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OPERATION & MAINTENANCE MANUALFOR 5 X 115TPH

RAAGESHWARI GAS / ASSOCIATED GAS/ DIESEL OIL FIRED BOILER

SUPPLIED TO

CAIRN ENERGY PRIVATE LIMITED

BASRMAR, RAJASTHAN

THERMAX JOB NO. - PF1051/52/53/54/55

THERMAX LIMITEDBOILER & HEATER GROUP PUNE INDIA

0 PSK 20/02.2009 AA 20/02.2009 USU 20/02.2009 0

REV PREPARED BY CHECKED BY APPROVED BY REVISIONDESC. /

REMARK

Operation & Maintenance Manual

Contents

Volume 1 — Boiler Description ....................................................................................................1Section A................................................................................................................................2

1 Design Specifications of Auxiliary Boiler .......................................................................32 Design Code...............................................................................................................33 Material Specifications — Pressure Parts .....................................................................44 Heating Surface Area ..................................................................................................45 Fuel ...........................................................................................................................46 Fuel Analysis .............................................................................................................47 Site Condition ............................................................................................................68 Continuous Blow Down................................................................................................69 Safety Valves..............................................................................................................610 Fans ........................................................................................................................611 Burners.....................................................................................................................712 Dosing System..........................................................................................................7

Section B................................................................................................................................91 Section Overview .......................................................................................................92 Water and Steam System .......................................................................................... 10

2.1 Deaerator........................................................................................................ 102.2 Boiler Feedwater Pump ................................................................................... 122.3 Boiler Feedwater Control Station ...................................................................... 132.4 Economizer ..................................................................................................... 132.5 Boiler Assembly .............................................................................................. 142.6 Superheater .................................................................................................... 162.7 Attemperator ................................................................................................... 162.8 Main Steam Line.............................................................................................. 17

3 Valve Positions Chart (Before Light Up) ...................................................................... 224 Air and Flue Gas System........................................................................................... 28

4.1 FD Fan ........................................................................................................... 284.2 Air Duct........................................................................................................... 294.3 Windbox.......................................................................................................... 304.4 Furnace .......................................................................................................... 314.5 Flue Duct ........................................................................................................ 314.6 Cooling Air For Peepholes ............................................................................... 32

5 Fuel Firing System .................................................................................................... 325.1 Components Description ................................................................................. 32

Section — C ......................................................................................................................... 421 Section Overview ...................................................................................................... 422 Boiler Start Up and Shut Down................................................................................... 42

2.1 Startup of a Cold Boiler .................................................................................... 422.2 Charging of Fuel (Associated Gas / Raageshwari Gas/Diesel Oil ), Automizing

Steam & Air Line ........................................................................................ 462.3 Boiler Startup and Pressurizing ........................................................................ 48

3 Boiler Hot Startup Pressure Raising Curve.................................................................. 544 Boiler Warm Startup Pressure Raising Curve .............................................................. 555 Boiler Shutdown........................................................................................................ 56

5.1 Planned Shut Down ......................................................................................... 566 Boiler Emergency Trip ............................................................................................... 57

6.1 Boiler Shutdown During Sudden Tube Failure.................................................... 577 Boiler Operation ........................................................................................................ 57

7.1 Do’s and Don’ts for Boiler Operation ................................................................. 577.2 Boiler Log Sheet .............................................................................................. 58

8 Boiler Safety ............................................................................................................. 608.1 Emergency Procedures.................................................................................... 60

i


8.2 Operational Precautions for Safety.................................................................... 619 Tube Failures............................................................................................................ 6410 Trouble Shooting Chart............................................................................................ 6411 Water Quality Recommendations.............................................................................. 67

Section — D ......................................................................................................................... 691 Section Overview ...................................................................................................... 692 Recommended Maintenance Practices....................................................................... 69

2.1 Preventive Maintenance................................................................................... 692.2 Schedule of Inspections for Condition Based Maintenance ................................. 692.3 Boiler Annual Maintenance and Overhaul.......................................................... 742.4 Tube Thickness Survey.................................................................................... 75

3 Welding Procedure Specifications (WPS) ................................................................... 764 Boiler Preservation Procedure.................................................................................... 76

4.1 Definitions of Water Quality .............................................................................. 764.2 Dry Storage Preservation ................................................................................. 774.3 Wet Storage .................................................................................................... 784.4 Nitrogen Blanket .............................................................................................. 794.5 Boiler Lay UP Procedures ................................................................................ 804.6 Preservation of Rotating Equipments ................................................................ 804.7 Preservation of Instruments ............................................................................. 80

5 Tube Failures............................................................................................................ 815.1 Tube Failure Investigation / Analysis Method ..................................................... 815.2 Window Patch Welding .................................................................................... 83

6 General Principal of Weld Repairs.............................................................................. 857 Failure Reporting Format ........................................................................................... 978 Water Chemistry ....................................................................................................... 98

8.1 Undissolved and Suspended Solid Materials ..................................................... 988.2 Dissolved Salts and Minerals............................................................................ 988.3 Dissolved Gases.............................................................................................. 998.4 Other Materials................................................................................................ 998.5 pH Value of the Water and its Importance.......................................................... 998.6 Effects of Impurities ......................................................................................... 99

9 Feed & Boiler Water Conditioning............................................................................. 101Section E............................................................................................................................ 104

Volume 2 — Drawings.............................................................................................................. 105List of Drawings .................................................................................................................. 106

Volume 3 — E & I Specifications.............................................................................................. 107Section 1 ............................................................................................................................ 108Section 2 ............................................................................................................................ 108Section 3 ............................................................................................................................ 108Section 4 ............................................................................................................................ 108Section 5 ............................................................................................................................ 108Section 6 ............................................................................................................................ 108Section 7 ............................................................................................................................ 108Section 8 ............................................................................................................................ 108Section 9 ............................................................................................................................ 108Section 10 .......................................................................................................................... 109Section 11 .......................................................................................................................... 109Section 12 .......................................................................................................................... 109

Volume 4 — Vendor Manuals ................................................................................................... 110Section 01 .......................................................................................................................... 111

Fan — TLT Engineering................................................................................................ 111Section 02 .......................................................................................................................... 111

Scanner Cooling Fan — Andrew Yule ............................................................................ 111

ii


Section 03 .......................................................................................................................... 1113.1 Drum Level Gauges – Chemtrol............................................................................... 1113.2 Magnetic Level Gauge – Chemtrol ........................................................................... 111

Section 04 .......................................................................................................................... 111Process Valve – KSB.................................................................................................... 111

Section 05 .......................................................................................................................... 1125.1 Safety Valve – Tyco Sanmar.................................................................................... 1125.2 Relief Valve – Tyco Sanmar..................................................................................... 112


Pressure Transmitter (3051) – Emerson ........................................................................ 114Section 02 .......................................................................................................................... 114

Temperature Transmitter (644H) – Emerson................................................................... 114Section 03 .......................................................................................................................... 114

Oil Flow Meter (1700R) - Emerson ................................................................................ 114Section 04 .......................................................................................................................... 114

O2 Analyser (ZR22G) – Yokogawa ................................................................................ 114HART Protocol ............................................................................................................. 114

Section 05 .......................................................................................................................... 114Flame Scanner – Fireeye.............................................................................................. 114

Section 06 .......................................................................................................................... 1146.1 Thermocouple Assembly– Pyro Electrical ................................................................. 1146.2 Damper Actuator - Keltron Controls.......................................................................... 114

Section 07 .......................................................................................................................... 1157.1 Black & Bleed Valve- ELO Matic ............................................................................. 1157.2 Main Fuel Trip valve – Virgo .................................................................................... 115


SWAS Panel - Emerson................................................................................................ 117Section 02 .......................................................................................................................... 117

Gas Calori Meter – Chemtrol......................................................................................... 117Volume 7 — Vendor Manuals ................................................................................................... 118

Section 01 .......................................................................................................................... 119Spring Hangers – Techno Industries .............................................................................. 119

Section 02 .......................................................................................................................... 119Blow Down Valve - BHEL.............................................................................................. 119

Section 03 .......................................................................................................................... 119Control Valve - Fisher ................................................................................................... 119

Section 04 .......................................................................................................................... 119HP,LP & PH Dosing Pump - Metapow............................................................................ 119

Index.................................................................................................................................. 121

iii


iv


Volume 1 — Boiler Description

Chapters Covered in this Part

♦ Section A♦ Section B♦ Section — C♦ Section — D♦ Section E

Volume 1 — Boiler Description 1


Section A

Topics Covered in this Chapter

♦ Design Specifications of Auxiliary Boiler♦ Design Code♦ Material Specifications — Pressure Parts♦ Heating Surface Area♦ Fuel♦ Fuel Analysis♦ Site Condition♦ Continuous Blow Down♦ Safety Valves♦ Fans♦ Burners♦ Dosing System

Section A 2


Number and Type of Boiler

5 x 115 TPH, Water tube, Natural Circulation, Natural Gas / Oil Fired Bi-Drum Packaged boiler.Bottom Supported Pressure part arrangement.

1 Design Specifications of Auxiliary Boiler

PARAMETERS UNIT VALUE

Boiler Rating [MCR] TPH 115

Steam Pressure at Main Steam StopValve Outlet from minimum Loadupto MCR

Kg/cm2 (g) 42.32

Steam Temperature at the MainSteam Stop valve at MCR Deg C 371±5

Main Steam Temperature Controlrange at the Main Steam Stop ValveOutlet.

% MCR 40 –100

Hydraulic Test Pressure Kg/cm2 (g) 81

Design Pressure Kg/cm2 (g) 54

Fuel Firing

Combination of Associatedgas and Raageshwari gasand LDO. The system shouldbe capable of firing 100%MCR max with either fuel.The percentage of firing willbe on heat input basis.

Boiler Performance TestingProcedure

ASME PTC 4 EnergyBalance

2 Design Code

Boiler & Economiser / Pressure Parts: As per IBR 1950 with latest amendments

Section A 3


3 Material Specifications — Pressure Parts

Description Details Size In Mm Material

Shell 1500 ID x 70 ThkSteam Drum Dished end for S.D.

(Hemispherical) 1500 ID x 50 ThkSA 516 Gr 70

Shell 960 ID x 50 ThkWater Drum Dished end for W.D. (2:1

Semi Ellipsoidal) 960 ID x 50 ThkSA 516 Gr 70

Pass I 50.8 OD x 4.5 Thk SA 213 T11

Pass II 50.8 OD x 4.5 Thk SA 213 T22

Pass III 50.8 OD x 5.0 Thk SA 213 T22Super Heater

I/L & O/L Header 350 NB x 160 SCH SA 335 P11

Attemperator Header 300 NB x 80 SCH SA 335 P11

Boiler Bank Tubes 50.8 OD x 3.25 Thk SA 210 Gr. A1

Boiler side wall tubes 50.8 OD x 3.66 Thk SA 210 Gr. A1

Boiler side wall panels 63.5 OD x 4.06 Thk SA 210 Gr. A1

Bank Rear wall 76.2 OD x 4.06 Thk SA 210 Gr. A1

Side Wall Tubes 76.2 OD x 4.06 Thk SA 210 Gr. A1Furnace Tubes

Rear Wall Tubes 76.2 OD x 4.06 Thk SA 210 Gr. A1

Baffle Wall Tubes 76.2 OD x 4.06 Thk SA 210 Gr. A1

4 Heating Surface Area

Zone Unit Value

For Boiler Bank Sq.Mtr 1596

For Superherater Sq.Mtr 235

For Economiser Sq.Mtr 3008

Heating Surface Total Sq.Mtr 4839

5 Fuel

a) Main Fuels: Raageshwari Gas/Associated Gas/Diesel Oil

6 Fuel Analysis

Gas Associated Gas Raageshwari Gas

Composition (%) (%)

Methane 68.78 83.04

Ethane 0.52 11.01

Propane 0.66 3.1

Iso Butane 0.28 1.15

Normal Butane 0.36 0.71

Section A 4


Gas Associated Gas Raageshwari Gas

Iso Pentane 0.15 0.28

Normal Pentane 0.15 0.2

Hexane 0.01 0.11

Heptane 0.84 0.07

Nitrogen 0.2 0.24

CO2 19.94 0.01

Water Vapour 7.99 0.08

Total 100 100

Operating Temp °C(Min/Normal/Max) 80 / 85 / 95 15 / 40 / 50

Operating Pressure(kg/cm2) 3.57 / 4.22 3.57 / 4.22

Design Temp (°C) 130 130

Design Pressure(kg/cm2) 10.5 10.5

Total Molecular Weight 23.4 19.7

LHV (kJ/Sm3) 27510 40520

LHV (kcal/kg) 6541 11641

Fuel Fired(kg/hr) 11670 6540

Diesel Oil No.2

Composition Unit Value

Carbon % wt 90.355

Hydrogen % wt 9.21

Nitrogen % wt 0.155

Sulfur % wt 0.05

Moisture % wt 0.05

Ash % wt 0.04

Carbon Residue % wt 0.3

Vanadium ppm <25

GCV Kcal/kg 10,305

LHV Kcal/kg 9820

Kinematic Viscosity @ 40°C cst 2 – 5

Density @ 15 °C Kg/m3 820 – 860

Flash Point(min) (Pensky Martens closed cup) °C 66

Pour Point(min) (Winter / Summer) °C 15-Mar

Conditions at Battery Limit

Pressure

(Max / Nor) kg/cm2(g) 18.97 / 12.24

Normal Operating Temp °C 15 – 40

Section A 5


7 Site Condition

Site Location CEIPL, Barmer, Rajasthan

Ambient Temperature

Performance 40 ° C

Maximum 50 ° C

Minimum — 2° C

8 Continuous Blow Down

Design : 3%

Normal : 1%

9 Safety Valves

DESCRIPTI ON UNIT DRUM #1 DRUM #2 SH

APPLICATION

TYPE - SPRING LOADED

MAKE TYCO SANMAR

TAG NO - PSV-7018B PSV-7018C PSV-7018A

SIZE ORIFICE -

3 x L2 x 6 3 x L2 x 6 2.5 x K2 x 6

SET PRESS. Bar(A) 53 54 47

OPERATING TEMP. DEG.C 267 268 376

RELIEVING CAPACITY Kg/hr 54,808 55823 32377

QUANTITY - 1nos. 1nos. 1nos.

FLUID - Sat. Steam Sat. Steam SH Steam

10 Fans

Duty conditions Unit FD Fan

Make Andrew Yule And Co. Ltd

Model SI.BCB-92

Quantity 02 No. 1 x 60%

Nature of medium Clean Air

17.24 (Associated Gas)

17.16 (Raageshwari Gas)Design Mass Airflow (MCR) Kg/s

17.4 (LDO)

Air Temperature at Fan Inlet Deg C 40

Absorbed Power at operating temp. withspeed control KW 160

Fan Speed Rpm 1480

Section A 6



Inlet Static Pressure mmWC -35

Outlet Static Pressure mmWC 417

Free/Fixed Bearing 22218C (Anti Friction) + HousingSAF-218

Bearing Lubrication VEEDOL ALITHEX – 20 or eqvt.Grease (500 gms for first fill)

Motor 200 kW /4 Pole, Type-M38M/GM355LK4; ABB MAKE

Coupling Model / Make Flexible spacer type (80SPL-262-140) / MAKE- Metaflex

11 Burners

Burner Units Gas

Type

Burner Make Thermax Babcock & Wilcox

Operating Draught Type Forced

Quantity (for MCR) 3 x 36.67%

Type of Air control & Accessories Lead Lag Arrangement; VIV at FanSuction Control

Type of Ignitor Gas fired electric ignited lighter

Supply From Plant

Differential Pressure at tip inlet at peak Kg/cm2 11

Air quantity required for burner (Associated/ Raageshwari / LDO) Kg/hr 41370 / 41193 / 41755

Excess air - 10%

Fuel flow at MCR (Indicative) (Associated /Raageshwari / LDO) Kg/hr 3890 / 2180 / 2604

No. of Flame Scanner - 2 No (UV scanner) / burner

12 Dosing System

HP DOSING SYSTEM : METAPOW INDUSTRIES

Sr.No. DESCRIPTION HP DOSING LP DOSING PH DOSING

1 TANK (SS) SIZE /VOLUME

I.D 940 X 1000 X 3THK. / 500 Lit

I.D 940 X 1000 X 3THK. / 500 Lit

I.D 940 X 1000 X 3THK. / 500 Lit

0-15 L.P.H 0-15 L.P.H 0-15 L.P.H

51 kg/Cm2 (Nor.) 4 kg/Cm2 (Nor.) 6 kg/Cm2 (Nor.)2 PUMP CAPACITYPRESSURE ( MAX )

59 kg/cm2 (Design) 5.5 kg/cm2 (Design) 7.5 kg/cm2 (Design)

3 PUMP MAKE MetaChem MetaChem MetaChem

4 TYPE & SPEED RECIPROCATINGPLUNGER

RECIPROCATINGPLUNGER

RECIPROCATINGPLUNGER

5 NO OF PUMPS 2 Sets 2 Sets 2 Sets

Section A 7


Sr.No. DESCRIPTION HP DOSING LP DOSING PH DOSING

6 MOTOR 0.5 Hp. X 1500 RPM, 415 Volt, Crompton

0.5 Hp. X 1500 RPM, 415 Volt, Crompton

0.5 Hp. X 1500 RPM, 415 Volt, Crompton

7 MOTORISEDAGITATOR / MOTOR

1 HP X 1000 RPM ,415 Volt, Crompton



8PRESSURE RELIEFVALVE SETPRESSURE

59 Kg/Cm2 5.5 KG/Cm2 7.5 KG/Cm2

9 LUBRICATION (Forpumps) SERVOMESH 460 SERVOMESH 460 SERVOMESH 460

Section A 8


Section B


♦ Section Overview♦ Water and Steam System♦ Valve Positions Chart (Before Light Up)♦ Air and Flue Gas System♦ Fuel Firing System

1 Section Overview

This section gives a brief overview of the project,boiler packages and associated systems. Thedescription of the various systems that form part

of the auxiliary boiler package is also included.The aim of this section is to make the reader/ user familiar with the auxiliary boiler packagecomponents before introducing the operation andmaintenance sections.

BRIEF OVERVIEW

The five package boilers supplied by THERMAXBABCOCK & WILCOX, India are of fully modular(FM) type, shop/port assembled, bi-drumconstruction, water tube, natural circulation type,bottom supported, forced draft designed for firingwith Associated Gas / Raageshwari Gas / DieselOil.

The main parameters of individual boilers are –

Sr.No.

DESCRIPTION VALUE

1 Maximum Continuous Rating 115 TPH

2 Steam Pressure 42 Kg/cm2 (g)

3 Superheated Steam Temperature 371 ± 5 °C

4 Fuel Fired Raageshwari Gas / AssociateGas / Diesel Oil

The construction of the Boiler can be understoodfrom the pressure parts arrangement of the Boiler.P & I D of the water and steam system.

The boiler is divided into a ’furnace’ section anda ’second pass’ by a division membrane wall.The furnace section is made of tube walls anda refractory wall. The furnace comprises thefurnace side-wall, roof, floor & rear walls andthe front refractory wall. The furnace side, roofand floor, rear walls are of membrane panelconstruction. The furnace front wall is of refractoryconstruction. The second pass comprises theSuperheater, convection bank tubes. The secondpass is enclosed by the rear wall & boiler side-wall.Entire array of tubes in the furnace & secondpass is connected to the steam and water drums.The Superheater is designed for convective heattransfer and is fully drainable.

Feedwater from plant is admitted to theeconomiser through a feedwater control station.The feedwater is then led to the steam drum.Steam is generated in the convection bank tubes.In the riser tubes partial evaporation takes placedue to the heating. The resulting water-steammixture returns to the steam drum where theseparation of steam from water takes place. Thesaturated steam is led to the Superheater andthen through the main steam stop valve to theprocess plant.

Combustion of the fuel takes place in the furnacewith the help of the burners mounted on thefurnace front refractory wall. Combustion air issucked from the plant environment by the FDfan. The burners are capable of firing AssociatedGas / Raageshwari Gas / Diesel Oil safely andefficiently.

Flue gases generated from combustion passthrough the convection bank and is led toeconomiser through flue gas duct and finally intothe atmosphere through a steel stack.

Two burners have been provided on the furnacefront wall in two elevations for burning fuel oil. The starting, stopping and safe shutdownof the burner are monitored by a PLC basedBurner Management System (BMS). DCS basedcontrollers are provided by contractor for thecontrol loops. The operation of the boiler isenvisaged from the DCS operator stations.

Three long-retractable & three rotary soot blowersare provided in the superheaters, boiler bank andEconomiser surfaces, when the burners are inservice. Soot blowing is done to keep up the heattransfer efficiency at the maximum level.

Safety valves have been provided in the Drumand in the main steam line of the Boiler. Suitableinsulation around the drum, the membranepanels, steam lines, feed water lines, hot air and

Section B 9


flue ducts have been provided to minimize heatloss and for Operators safety.

Pressure, Temperature, Level transmitters,conductivity, pH, oxygen analyzers etc., for localindication as well as input to the DCS have beenprovided. Microprocessor based automatic (aswell as manual) control of Drum level, combustion,steam temperature etc., has been provided.Operation of the boiler as well as Data Acquisitionhas been envisaged through the DCS.

Description & details of equipment of the varioussystems of the boiler package are elaborated inthe subsequent sub-sections and chapters of thismanual.

2 Water and Steam System

The water and steam system covered in thissub-section describes the components thatconvert the feedwater water into steam.

The components in the serial order of the flow pathof water/steam are –

• Deaerator

• Boiler feedwater control station

• Economizer

• Boiler assembly

• Super Heater

• Attemperator

• Main steam piping

• Operational Control

• Dosing System

• Sample System

2.1 Deaerator

Purpose of Deaeration :-

Deaeration removes the corrosive gases such asdissolved oxygen and free carbon dioxide fromthe boiler feed water. This ensures protectionof the feed water lines, steam lines, boiler tubesand other pressure parts of the boiler againstcorrosion and pitting, saves costly boiler re-tubingand expensive plant shutdowns. Further as thetemperature of feed water is raised from ambientto Deaerator operating temperature of 130 °C[which corresponds to the operating pressure of169 kPa (g) ] and then fed to boilers, the overallboiler thermal efficiency also increases.

Deaeration is done by heating the feed waterwith steam. Vigorously scrubbing the waterwith this steam removes the last traces ofnon-condensable gases and brings down wellbelow the recommended level in feed water.

Construction Feature :-

The Deaerator supplied is of Thermal -Mechanical Deaerator in which DM water/makeup feed water is heated to its boilingtemperature at the operating pressure by steam.At boiling point all the dissolved gases such asOxygen, Carbon Dioxide, Etc. are liberated assolubility of gases decreases with increase intemperature. The mechanical scrubbing betweenwater and heating steam ensures release of thedissolved gases.

Deaerator is of spray and trays type, consists of astorage tank and a vapour tank. Water is sprayedfrom the top of the vapour tank by spray nozzleson set of multi level trays below it. Steam is fedfrom the supply pipe to the distribution headersinside the storage tank below the water level.Partial scrubbing of the steam and water takesplace in the storage tank water and the rest istaking place in the vapour tank with the incomingwater spray.

Vapour tank is mounted upon the storagetank. Both the tanks are connected withsteam connection Nozzle at the middle. Thisinterconnection nozzle of 100 ID & 20 THKis flushed with inner wall of the vapour tank’sdished end and embedded inside the waterlevel of storage tank to facilitate the feed waterflow from vapour tank to the storage tank.Interconnection accommodates concentricallythe steam balancing connection assembly. Thissteam connection is projected inside the vapourtank and masked from the water flow direction bya hood fitted at the top, thus facilitates the steamflow from storage tank to vapour tank.

DM water enters to the vapour tank throughthe topside nozzle N2 to the distribution ringheader. Five spray nozzles are fixed on thering header to spray the water into fine particlescovering the entire cross section of the tank sothat easy and complete scrubbing with steamis possible. Perforated stainless steel trays atsix levels are placed inside the vapour tank toprovide enough delay time to scrub the feedwater with the upcoming steam. Feed water fromvapour tank flows into the storage tank throughthe interconnection pipe.

Condensate enters to the vapour tank through thetopside nozzle N2 to the distribution ring header.

Section B 10


Nozzles are fixed on the ring header to spray thewater into fine particles covering the entire crosssection of the tank so that easy and completescrubbing with steam is possible.

Heating Steam is supplied through the supply pipe(Nozzle N1) to the steam distribution headers keptinside the storage tank well below the water level.Two steam distribution headers connected to thesupply pipe are lied at the bottom and along thelength of the storage tank. These headers areperforated pipes to distribute the steam along theentire length of the storage tank water space.

Steam rises from the bottom of StorageTank, heating the water and rises throughthe interconnection pipe into the Vapor Tank.Perforated Trays inside the Vapor tank increasethe residence time of water and Heating Steam.Oxygen, Carbon dioxide and other dissolvedgases are vented out along with Vent Steamthrough the nozzle N18

The dissolved Oxygen level in the feed waterby mechanical deaeration can be brought to0.02 to 0.03 ppm. If required the residualdissolved Oxygen can be further scavengedby the reaction with chemicals such as sodiumsulphite (catalyzed or un-catalyzed) or Hydrazine.By chemical scavenging the dissolved Oxygenlevel can be brought down to as low as 0.007ppm. Chemical may be dosed in the storagesection of the deaerator through a header. NozzleN5 20NB is provided for this and can be utilized.The dosing of the particular chemicals is donein predetermined quantity and concentration. Asample cooler provided in the feed water outletpiping is used to collect the sample for analysisof water.

Storage tank is supported by saddle supports.One of the saddles is fixed and the other is slidingone to take care of thermal expansion. PTFEsheets are provided under the sliding saddle forfree movement of saddle. Platforms and laddersare provided for tanks and condenser for O & Mfeasibility.

The Accessories and the Mountings :-

1. Deaerator Level Control :- The desired normalwater level (NWL), which is maintainedthrough a level control valves LV 7110 ofDM water line & condensate return linecombinely. Level in the storage tank ismonitored remotely by the level transmitter[LT 7111 A,B,C]. Two nozzles (N11A,B &N14A,B) at this elevation are provided for LTconnection at distance of 875 mm above and2125 mm below (for N11 A/B) and at distance

of 900 mm above and 2140 mm (for N14 A/B)the NWL.

A Feed back control loop with the electroniccontroller LIC 7110 is provided for automaticlevel control. Process variable signal for thelevel controller is transmitted by the LT 7110.Set point of the level controller is to be kept at’0’ mmWC, which corresponds, to NWL.

Apart from this remote level indication directlevel gauge glass [LG 7110] are provided tocover the height between very low level andupto over flow level. These level gauge aremounted on a water column connected to theNozzles N14

• Pressure Control :- The deaeratoroperating pressure of 169 kPa (g) ismaintained by the pressure control loop,which contains the pressure control valve[PV 7110 ] in the steam line, a pressuretransmitter [PT 7110 ] mounted on thestorage tank nozzle N10 and an electronicpressure indicating controller [PIC 7110] inthe control room. Set point for the pressurecontroller shall be kept at (169 kPA (g)).

A local pressure gauge [PG 7112] is alsoprovided (on Nozzle N9) for deaeratorpressure indication.

• Pressure Relief Valve (PSV 7111) :- ANozzle N20 is provided at the top of vapourtank to mount a relief valve. Relief valvewould relieve the steam at the designset pressure of 245 kPa (g), when thereis excessive pressure build-up insidethe vessels (system) incase of suddenreduction of water out flow/ intake todeaerator or malfunctioning of pressurecontrol loop.

• Vacuum Breaker :- A Vacuum Breakerassembly consists of Non Return Valves[VRV 7111] directed towards vapor Tankfrom atmosphere mounted on the NozzleN20. This is to prevent Deaerator fromoperating at vacuum or negative Pressure.Vacuum condition inside the Deaeratorwould mean that the Deaerator is not beingsupplied with enough Steam with respectto the water flow leading to condensationof heating Steam. In case the Deaeratorhappens to go under vacuum, atmosphericair will rush through these Non ReturnValves breaking the vacuum.

• Air vent :-Air vent is provided (nozzle N18)on topside of the vapour tank. Air vent isprovided with an orifice and a globe Valve

Section B 11


in parallel with it. Through the Air vent,Steam and dissolved gases are vent outto the atmosphere. The Valve shall bethrottled to minimize the outflow of Steam.

• Other Connections :-

– Feed water outlet nozzle N3 is provided.Water outlet piping going to the boilerfeed water pumps suction header.

– A drain nozzle (N4) for draining thestorage tank.

– Pegging steam connection (NozzleN7): A perforated pipe connected tothe nozzle is laid along the length ofthe storage tank below the water level.Admitting steam in a small quantitythrough pegging line and heating thewater to a temperature upto 150 Deg

C before admitting the main steam inlarge quantity will reduce the possiblehammering.

– Nozzle N16 is provided for recirculationline from the boiler feed water pumps.

– A Manhole are provided two for storageand one for vapour tank.

– A sample cooler is provided in the wateroutlet of deaerator for the analysis ofthe water sample. Sample cooler isa coil & shell heat exchanger, samplewater is passing through the coil andcooling water through the shell. Needlevalves are provided at the inlet and outletrespectively to regulate the sample flow.

Deaerator Specification:

UNIT VALUE

Deaeration capacity 126.5 TPH (Max)

Operating pressure 169 kPa (g)

Operating temperature 130 ° C

Design pressure 294 kPa (g)

Design temperature 200 ° C

Design & Construction code ASME SECT. VIII DIV1 Edition 2007,(WITHOUT STAMPING)

Reference Drawings :

Sr.No. Descreption Drawing No Revision

1 Assembly of Deaerator W21-1FM-45966 03

2 Assembly & Details of Vapour tank W21-1FM-45967 03

3 Assembly & Details of Storage tank W21-1FM-08203 04

4 P & I Diagram for Deaerator, D12 -1FM- 6712P 02

2.2 Boiler Feedwater Pump

The feed water pump is customer scope ofsupply

2.2.1Feed water pump’s associated system:

Suction piping:

Common suction header for all the three pumpsis connected from the deaerator outlet piping,providing necessary suction to the pump withisolation valve [DA032]at exit of De-areator.

Minimum circulation piping:

The minimum circulation piping is provided withindividual pumps. This ensures that during the

operation of the pump there will always be aminimum flow across the pump even when thereis no discharge into the boiler.

An auto re-circulation valve is provided onindividual pump discharge line for the abovepurpose

Throttle valve – for controlling the flow through thecirculation line.

Non-return valve – to prevent the back flow.

Discharge Piping:

Discharge of each pump is connected to thecommon discharge header, which supplies feedwater to the boiler. A pressure gauge [PG 7018]

Section B 12


installed on the discharge header for observingthe discharge pressure.

Auto re-circulation valve (ARC) installed at thepump discharge maintains the minimum flowrequired through the pump, when the flow to boileris low. This minimum circulation flow is takenthrough a line connected back to the deaeratorstorage tank with a gate valve (DA 031).

2.3 Boiler Feedwater Control Station

Feed water is supplied continuously to maintainnormal water level in the steam drum. TheFeedwater Control station installed in the feedwater line modulates the water flow to maintainthe level in steam drum. Water flows from the flowcontrol station through the economizer beforeentering into steam drum.

Feedwater from the plant is received at Terminalpoint. Following instruments are provided tomeasure the feedwater inlet parameters:

• Flow orifice [FE 7018-A] with a DP transmitter[FT 7018-A] for feed water flow measurement.Flow transmitter transmits the measured signalto the flow indicating controller( FIC 7018-A )in DCS

• A pressure transmitter [PT 7018-A] to providefeed water inlet pressure signal at DCS.

The feed water control station consists of a threepneumatic flow control valve [LV 7018-A], [FV7018-AA] & [7018 -AB] with capacity of 30%,110% and 110% MCR respectively. The controlvalve is provided with isolation valves BW009,B0013 & BW0017 respectively on its upstreamand BW 010, BW014 & BW018 on its downstreamrespectively. These isolation valves are normallykept open. A drain valve is provided at the downstream of the control valves for maintenance. Toprevent back flow from the boiler a NRV [BW023]is installed in the feed water line to Economizer.The thermocouple [TE 7018-E] installed withtransmitter [TT 7018-E] will provide the feed watertemperature at economizer inlet in DCS.

Drum Level Control Loop

Three-element feed water control system isprovided to regulate the quantity of feed waterflowing into the boiler to maintain the requiredwater level in the steam drum. In three-elementcontrol, the drum level is controlled by the threeprocess parameters (variables) - drum level, feedwater flow & steam flow.

Drum level is measured by the differentialpressure type level-transmitter [LT 7018-A] .The measured process variable (PV) from LT is

compared with the fixed set point (SP) in the drumlevel indicating controller [LIC 7018-A] block anda control signal is generated. The level controllercontrol output is added with steam flow signalfrom the main steam line in the feed forward block.This is done to achieve a better level control bytaking corrective action in anticipation. The outputof the feed forward block is used as a variableremote set point to the water flow-indicatingcontroller [FIC 7018-A]. This variable set pointis compared to the actual feed water flow signalfrom [FT 7018-A] and the controller [FIC 7018-A]will position the feed water control valve through acurrent-pneumatic converter. Action of the controlvalve is Air/ Signal fail to open and provided withair lock relay.

There are two flow control valves [FV 7018-AAand 7018-AB] provided with capacity of 110%MCR out of which only one control valve shallbe kept in AUTO mode at a time. Out of the twoany one can be used during three element modewhen selected.

Another flow control valve with 30%MCR capacityis provided in parallel with the rest two flow controlvalves. When the boiler load is less, this valveshall be used in single element mode to havebetter control on the drum level. Also becauseof low dP across the valve, erosion possibilitybecause of flow is minimized.

Alarms are generated from the transmitter signalin the DCS for low drum level (LALL) and highdrum level (LAHH).

2.4 Economizer

A continuous finned tube economizer is locatedon the flue gas duct from the boiler to recovereconomically feasible heat from the flue gasbefore discharging to the atmosphere. Therecovered heat increases the temperature offeedwater entering the steam drum. The directionof feedwater flow (inside the tubes) and flue gas(outside the tubes) are opposed cross flow foroptimum heat transfer. Flue gas flows verticallythrough the Economizer.

The coils are made of SA 210 GrA1 material andof size 50.8 OD * 3.66 thick and arranged betweeninlet and outlet headers. The headers 20NB x120 SCH are made of SA 106 Gr B material.The coils are supported on either side, inside thecasing. The economizer is fully drainable by thedrain valves provided on the inlet header [FD007& FD008] and on the outlet header [FD004 &FD005]. Manholes are provided on the casingfor cleaning and inspection of the economizersurfaces.

Section B 13


During operation, feedwater from control stationoutlet flows to the economizer inlet header andthrough the coils absorbing heat from the flue gas.Then it flows into the steam drum from the outletheader.

2.5 Boiler Assembly

The boiler is of bi-drum construction. Upper drumof the boiler is the steam drum and the lower drumis the water drum. Both the drums are providedwith manholes on each side for access inside thedrum. The drums are closed tight at either endby cover plates bolted against the manhole rim bytwo holding bars. A gasket is fitted between thecover plate and the mating machined surfaces inthe end shield. The cover plates swing inside, forconvenience during opening.

All the boiler tubes are connected to these twodrums except the rear wall panel tubes, whichare connected to the steam drum through riserpipes and through down comers to the waterdrum. The tubes enter the drums radially andhave been expanded mechanically inside. Thetubes support the steam drum, whereas waterdrum rests on the saddle supports.

The boiler is divided into a furnace section & asecond pass by a baffle wall made of membranepanel. The flue gases that are generated fromcombustion in the furnace pass to the secondpass through screen tubes at the rear side. Heattransfer takes place in furnace by radiation and insecond pass by convection. Furnace is formedwith the furnace side, roof & floor wall madeout of single membrane panel and at rear it hasflat studded wall construction. The furnace frontwall is constructed out of refractory bricks, whichhouses the burners and access door. Furnacefloor is covered with refractory bricks to facilitateeffective natural circulation in the furnace walltubes.

In the second pass, the superheater and theconvection bank tubes are located. In betweenthe baffle wall and the studded boiler sidewallthe superheater and convection bank areaccommodated. Combustion products (flue gas)from the furnace pass over the superheater andthen to the convection bank tubes. The flue gasexits the boiler at the front of the boiler sidewall.

Baffle wall is fitted with upper and lower rows ofrefractory plugs. These plugs are provided forinspection and water washing of convection bank.On completion of water washing these plugs are

installed back to seal the gaps. View ports areprovided at the furnace side and rear walls forobserving the flame.

Steam drum receives feedwater from theeconomizer. A perforated feed pipe inside thesteam drum distributes feedwater across thelength. Water flows to the water drum throughportion of the convection bank tubes, which arenot baffled at steam drum from the water level,acting as down comer tubes.

Boiler tubes absorb the heat from combustion andconvert water into water-steam mixture and thisconversion keep the tubes cool, within their safepermissible operating temperature.

Steam drum receives steam-water mixture fromthe furnace tubes, rear wall tubes and a portionof the convection bank tubes after evaporation.This mixture is routed to the cyclone separatorsthrough the baffles inside the steam drum. Themixture flows tangentially through the cycloneseparators. While flowing through the cyclones,water that is heavier gets separated from steamand tickle down to mix with the water in the steamdrum. Steam rises upward to flow through thescrubbers provided at the top of the steam drum.Scrubbers provide a tortuous path to the Steamand during this passage, last traces of water arestripped out from steam. Saturated dry steamcollects at the saturation chamber above thescrubber and then passes to the superheaterthrough the steam supply pipes to increase thetemperature of steam.

For controlling and monitoring of variousparameters, Steam drum is fitted with severalcomponents & instruments -

1. Level Sensing Instruments :- Level sensinginstruments are tapped off from the front& rear sides of the steam drum on thehemispherical dished ends.

• Level Gauges [LG 7018-A/B]:- Two directlevel gauges are provided one each onfront and rear side of the steam drum.Level gauges serve for direct and accuratereading of the steam drum level. The levelgauges are used to verify the readings oflevel transmitters.

• Level Transmitters :- Six level transmitters[LT 7018-A/B/C/D/E/F] is installed onthe steam drum. From these six leveltransmitters three [LT 7018-D/E/F] aretaken for drum level very low & high safetyinterlock as two out of three logic in BMS

Section B 14


to trip the burners. The other three leveltransmitter [LT 7018 A/B/C] signal is usedfor drum level control as process variable.

2. PRESSURE INDICATORS :-Two pressuregauges [PG 7018-F/G] are provided for localindication.

3. PRESSURE TRANSMITTERS :-Four pressure transmitters [PT7018-CA/CB/CC/CD] are installed on steamdrum. From these six pressure transmittersthree [PT 7018-CA/CB/CC] are taken fordrum pressure high high safety interlockas two out of three logic in BMS to trip theburners. The other one pressure transmitter[PT 7018-CD] signal is used for densitycompensation as process variable.

4. DRUM SAFETY VALVES PSV 7018 B/C]:- To protect the boiler and the personnelagainst the consequences of abnormalpressure increase caused by sudden loadcut, malfunctioning of firing system, closureof steam valves etc., two spring loadedmechanical safety valves have been fittedon the steam drum. On increase of thesteam pressure beyond the set value of theSafety Valve’s, [5198 kPa (g) & 5295 kPa (g)respectively] the valves open automatically torelieve the steam to atmosphere. The safetyvalve closes when the drum pressure falls tothe reset pressure of the valve. The relievingcapacity of all the Safety Valves put togetheris designed in such a manner that even atmaximum firing rate of the Boiler, the valvesare capable to relieve the total generation ofsteam thus safeguarding the boiler.

5. AIR VENT :- An air vent, with isolation valve[DM 039] along with motorized valve [MOV7018-G] is provided on the steam drum to ventout air during initial boiler filling & cold startupand while de-pressurization/ shutting downthe boiler to prevent the drum from going intovacuum pressure due to condensation. Whileboiler cold start up, the air vent is kept opentill the steam drum pressure reaches 2 bar(g) and similarly it is opened when the drumpressure falls to 2 bar (g) during shutdown.

6. N2 CONNECTION :- A connection withan isolation valve [NI 001 & NI 002] alongwith NRV [NI003] to fill N2 for boilerpreservation has been provided on steamdrum. Preservation procedure is explained inmaintenance section of this manual. N2 lineis isolated normally during the operation ofthe boiler.

7. DOSING AND BLOWDOWNCONNECTIONS :- A Continuous Blow down(CBD) connection and a Chemical Dosingconnection are provided on the steam drumfor conditioning of the Boiler Water.

• CONTINUOUS BLOWDOWN :- Due tocontinuous evaporation of boiler waterin the drum, minor impurities presentin the feedwater concentrate to highimpermissible levels in the boiler water.Rise in hardness of water, phosphates,content of chlorides, silica etc., haveto be kept to a minimum to preventscale formation or deposits in the boilerevaporation tubes, drums, superheater,steam piping and the down streamequipment. Sample of boiler wateris collected through a sample cooler.Based on measured value of conductivity,determined amount of water is continuouslydrained from the boiler drum throughthe Continuous Blow Down (CBD) lineby a CBD valve [MOV 7018-F] alongwith isolation valves [BD 001/002/003] toreduce the concentration of impurities andto maintain within the permissible levels.A 25 NB pipe with its one end open islaid along the water space of steam drumbelow the normal water level. This pipeis connected to blowdown drum with anisolation valve [BD 001/002/003] & mainblow down valve [MOV 7018-F].

• PHOSPHATE DOSING CONNECTION:- Tri-Sodium phosphate is dosed intothe boiler water to maintain a phosphateconcentration of maximum 34 ppm andpH of 9.0 to 11.2. The Phosphate has thecapacity to convert hardness producinginsoluble calcium/ magnesium salts tosoluble salts, which are drained throughthe blow down.A typical reaction can be as follows: 3CaSO4 + 2 Na3 PO4 → Ca3 (PO4)2 ↓ +3Na2 SO4 . The dozed phosphate alsoprovides desired alkalinity to the boilerwater. An alkaline pH minimizes thepossibilities of corrosion.Dosing of phosphate to the Boiler water isto be done in a manner that it quickly mixeswith the whole of Boiler water. To enablethis a perforated pipe has been laid alongthe length of the steam drum and connectedto the HP chemical dosing system throughline with an isolation valve [HP 021 & HP023 ] and NRV [HP 022].

Section B 15


• IBD CONNECTION :- The water drum isprovided with connection to collect thesludge and other impurities, which willbe removed through the intermittent blowdown (IBD).

To drain the boiler completely during shutdown and to remove the silica/ sludgecollected in the boiler during operationa drain line from water drum is providedwith a intermittent blow down valves [FD016, FD 017 & FD 018] along with IBDvalve BD013. During normal operation ofthe Boiler IBD shall be operated by theoperator once in a shift for approximately 1minute duration. IBD can also be operatedduring emergency to lower the drum level ifthe drum level increases beyond specifiedlimits (like swelling during cold start up andduring load upsets). IBD line is connectedto the IBD tank through the drain header.

2.6 Superheater

Saturated steam from the steam drum flowsto the superheater assembly to increase thesteam temperature. Saturated steam from thesteam drum internals flows through the supplypipes to the superheater primary header, fromwhere it is distributed to other Superheater tubes.Superheater tubes are placed in between theSuperheater primary (inlet) and outlet headers.The headers are baffled to form multiple passesfor effective heat pickup to attain the desiredsteam temperature. In order to maintain the finalsteam temperature a spray type attemperator isinstalled in-between the passes.

Superheater is placed at the flue gas entry ofBoiler second pass. Continuous and sufficientflow of the steam through the Superheaterensures the metal temperature of the coils doesnot exceed the design value. Superheaterheaders are provided with drains, which areconnected to the blowdown tank through thedrain header. Superheater has to be drainedbefore starting the boiler and after shutdown toremove the condensate. Superheated steamfrom superheater final header flows to the mainsteam line.

2.7 Attemperator

An inter-stage attemperator is provided inthe superheater to maintain the final steamtemperature. Spraying a controlled quantity offeedwater into the superheated steam lowers its

temperature as it looses some heat in evaporatingthe sprayed water.

The attemperator is a header, whichaccommodates an inner sleeve shaped like aventuri. A spray nozzle is fixed at the entranceto the restricted venturi section. The sleeveis held in position firmly by the locating pinswelded to the header at the steam entry side.The sleeve is free to expand at the steam exitside. Water is sprayed through the spray nozzle.The steam passes through the venturi picks upthe spray, which completes the evaporation andthoroughly mixes the steam. The connection ofthe inlet to the spray nozzle embodies a thermalsleeve construction to protect the steam line fromtemperature differential between the spray waterand the steam. A drain connection is provided atthe exit of the attemperator.

The spray water is taped from the feed waterpiping before the feed water control station. Aglobe type pneumatically actuated control valve[TV 7018-C] is provided to control spray water flowto the attemperator. The control valve is providedwith isolation valves [DSH 017/006/014/007] atupstream and downstream. To prevent back flowof steam a NRV [DSH 013] is provided in the line.

A flow nozzle [FE 7018-B] with a differentialpressure transmitter measures the flow of feedwater to attemperator. It gives the signal to [FIC7018-A].

2.7.1Steam Tempearture Control Loop

This loop is used to maintain the temperatureof Superheated steam at rated value of 371 0C.Steam Temperature is controlled by attemperationi.e. by spraying feed water into the steam by Desuper heater nozzle located between the Primarysuper heater outlet & Secondary Super heaterinlet.

The final steam temperature is measured bytemperature elements [TE 7018CD] & Transmitter[TT 7018CD], output of which acts as a Processvalue for [TIC 7018CD].

Final steam temperature is controlled by [TIC7018CD] which will have Local set point (at 371 +5 0C) set by operator. Output of [TIC 7018CD] willbe Corrected by feed forward signal (i.e. output ofTIC 7018B) this corrected output is fed to Temp.Control valve [TV 7018C].

Steam temperature at attemperator outletmeasured by [TE 7018B] & [TT 7018B] shallact as a process variable signal to feed forward

Section B 16


Controller [TIC 7018B] which compares processvariable with Remote set point generated fromhigh selector block for generating the correctionvalue for [TIC 7018CD] controller output.

2.8 Main Steam Line

Temperature & Pressure Measurements

The main steam line connects the steam outletfrom super heater to the plant steam main at theterminal point main steam stop valve.

This line incorporates the following -

Temperature element [TE 7018CA/CB/CC/CD]with transmitter [TT 7018CA/CB/CC/CD] isprovided on the main steam line to measureand transmit the steam temperature to DCS.Temperature signal is taken as the processvariable for the temperature indicating controlleras explained above and for temperaturecompensation of the steam flow signal. SteamTemperature HIGH HIGH is generated fromthe signal of temperature transmitters [TT 7018CA/CB/CC]

Pressure transmitter [PT 7018B] installed on thesteam line provides the main steam pressuresignal to DCS & it is also taken for the pressurecompensation of steam flow.

Steam pressure HIGHHIGH is generated from thesignal of pressure transmitters [PT 7018B].

Safety Valve

To take care of the pressure upset caused bysudden load cut, malfunctioning of firing system,closure of steam valves etc., a safety valve [PSV7018A] is provided on the main steam line at thesuperheater outlet. On increase of the steampressure beyond the set value of the safety valve(4609 kPag), the valve opens automatically torelieve the steam to the atmosphere. The valvecloses when the pressure falls to the reseat valueof the value. The relieving capacity of the valvealong with the two safety valves on the drumis designed in such a manner that even at themaximum firing rate of the boiler, the valves arecapable of relieving the total steam generation ofthe boiler, thus safeguarding the boiler.

Flow Element

Flow orifice [FE 7018C] is installed on the mainsteam line to measure the steam flow fromthe boiler. Differential pressure transmitter (FT7018C) transmits the flow signal to DCS. Steamflow signal is compensated for steam pressureand temperature.

Start Up Vent

During boiler start up, till the operating pressureis reached and connected to the main header, itis necessary to establish steam flow through thesuperheater to prevent overheating of the tubes.While start up, to establish sufficient steam flowthrough the superheater tubes, a start up vent isprovided with a control valve in the main steampiping. Start up vent flow is regulated by thispneumatic flow control valve [PV 7018B] operatedmanually through the controller [PIC 7018A] inDCS. A motorised gate valve [MOV 7018C] isprovided for positive isolation. The exhaust of thestart up vent is led through a silencer to attenuatethe noise level.

Start Up Vent Pressure Control:

Boiler HP steam pressure signal from PT 7018Bis fed to PIC-7018B where the process variable iscompared with the local set point for generatingthe manipulated variable, which controls thePV-7018B.

Opening of control valves is sensed usingposition transmitter (ZT7018B), position indication(ZI-7018B) is provided. If start up vent valveopening is more than 5 % open position alarmZAL 7018B is provided for operator attention.

Steam Flow:

Steam flow is measured using a steam flowtransmitter FT- 7018C. that is connected acrossflow nozzle; the steam flow signal is to be squarerooted at the DCS end.

Pressure and temperature compensation ofsteam flow is carried out to take care of errorsarising due to density variation of steam, whenboiler is operating at conditions different fromdesign conditions.

Compensated Steam flow as explained aboveshall generate low flow alarm FAL 7018C whenever HP steam flow is less than 30%. At this timeoperator shall operate the valve in manual mode(i.e. FAL 7018C shall force) to open start up ventvalve PV 7018B through PIC 7018B to pass the30% MCR flow.

Main Steam Stop Valve (MSSV)

Main steam stop valve [MOV 7018D] is providedto isolate the boiler from the plant during shutdownand during startup until the operating parametersare attained. During regular operation of theboiler, this valve is kept fully open supplyingsteam from the boiler to the plant main. Themain steam stop valve is provided with an integralbypass valve [MOV 7018E] for initial warm up of

Section B 17


the down stream steam line and to equalize thepressure across the MSSV prior to opening it. ANRV [MS 010] is provided before the stop valveto prevent back flow of the steam from the plantto the boiler.

Sample Connection

To analyse the super heated steam quality, asample line is taped off from the main steamline with isolation valve [SAM 001 / 002] andconnected to the SWAS panel.

2.8.1Operational Control

A brief overview of operational control points isdescribed below. Operation & troubleshooting areseparately explained later.

STEAM DRUM :-

• Maintain feedwater, boiler water quality, andchemical concentration as prescribed.

• Maintain water level in the steam drum withinpermissible low and high levels. The protectionsystem envisages boiler trip at very low levels,which should not be bypassed.

• Maintain drum level gauge glasses in goodworking condition. Operators may verify thelevel transmitter reading with the level gaugeonce a day.

• Thermal stress in steam drum during startupand shutdown - Steam drum is a largecylindrical shell. Before lightup, the inner andouter surfaces of the drum are at the sametemperature. When boiler is lighted up, theinner surfaces gets heated up first by the water(and then by steam) and transmits heat to theouter surface of the drum. The heat transferis by conduction and is a bit slow. For shorttime after lightup, there can be differencesof temperature between water and steamsurfaces of the drum. Such a difference can setup thermal stresses, which are not desirable.To minimize the thermal stresses, the operatormust restrict the firing rate.

• Swelling - During boiler startup, as the boilerwater temperature reaches 90°C, there is asudden increase of water level caused by theincrease in the volume of hot water. Suchswelling, if not controlled, can cause a highlevel in the drum. To avoid this, initial fillingis restricted to a level (about – 50mm) and asmart operator anticipates a swell and usesthe intermittent blowdown to drain and controlthe level.

• Do not operate the boiler with safety valvesgagged. Passing of safety valves must beattended during the next shutdown.

General :-

• Boiler water can be drained after a shutdownonly after depressurizing to atmosphericpressure and cooling down to 80°C.

• Draining of the boiler water to be donethrough the blowdown where such provision isavailable.

• If a tube failure is detected, it is advisable toplan for an early shutdown. It may be possibleto quickly repair the failed tube and returnto service. If the shutdown is inordinatelydelayed, there are possibilities of largersecondary damages, which may prolong theshutdown required for repairs.

• Keep the isolation valves of all the instrumentsfully open.

• Manually operated valves must be closed handtight only. Use of levers on hand wheels is notdesired.

2.8.2Chemical Dosing & Sampling System

Chemical dosing system consists of chemicaldosing tank with two pumps with motorisedagitator interconnecting piping, valves andmountings. The complete assembly is mountedon the skid. Chemical dosing system are requiredto maintain feed & boiler water quality at desirablelevels.

Phosphate Dosing System

During the boiler operation the impurities in theboiler water keep on getting concentrated. If theboiler feed water is hard the concentration of suchchemicals may cause formation & deposition ofscales on boiler heat transfer surfaces, which isdangerous. The chemicals dosed (Tri Sodiumphosphate-TSP), react and form insolublecompounds, which prevent scale formation andaid in removal of existing scales. The quantityof such chemicals should to be calculated anddepending on the analysis of boiler water.

2.8.2.1 Description Of Dosing System Skid (Hp)

Total system is mounted on a Base frame.Chemical-mixing tank made of SS of capacity500-litres for HP dosing is provided, where thechemical is mixed with water for 8/24 hrs dosing.Following are the attachments of the tank - A level

Section B 18


gauge, One mixing water connection, one drain,one over flow connection with isolation valves,one motorised agitator for proper mixing of thesolution and a perforated screen at the inlet toavoid foreign material entry.

Phosphate Dosing Pumps

Two phosphate dosing pumps (A & B) of havebeen provided, out of which one is for service ata time, and the other is a standby. The pumpsare plunger operated reciprocating, positivedisplacement type. The stroke of the plungercan be altered to vary the capacity of the pumpas per requirement. The pump is driven by amotor through a gearbox. The vendor manualof the pump and gearbox is available with fullinformation on construction and parts detail.

Pump suction line is tapped of from the bottom ofthe tank. It is connected to the pump through anisolation valve and a strainer. A direct connectionof the DM water is given in between strainer andisolation valve for flushing of the discharge piping& strainer. Y strainer traps dirt or other solidparticles in its basket. The Y strainer is to becleaned once a month, after stopping the pumpand closing its inlet and outlet isolating valves.

Each pump is connected to a common dischargeline with the following valve arrangement:

• In the discharge line a pulsation dampener isgiven to dampen intermittent discharge fromthe pump. On the discharge side of the pump, apressure gauge and two outlet isolating valvesare fitted before the common discharge line. Asafety relief valve has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure atleast oncea year. The pump must not be operated withthe relief valve continuously operating. (Causeof relief valve operation must be found andrectified). The pressure gauge is fitted with adampening device to minimize pulsations onthe gauge when the pump is in service.

• The common discharge line is connected tothe HP dosing line of the steam drum throughan NRV and an isolation valve. The isolatingvalve is verified open before boiler light up andnormally remains open all the time. Phosphatedosing is through a perforated pipe along thefull length of the water space in the drum.

• Availability of a minimum level in the mixingtank is a pre condition for starting or runningof the dosing pumps. For this purpose a level

switch has been provided for the tank thatgives level low signal LSLL 773A0, whichis interlocked to dosing pumps to preventaccidental start-up during low tank level. Outof the two pumps, one pump is selected forservice and the other is in reserve (DCS macro,Local panel). The pumps are interlocked suchthat when a working pump trips, the reservepump starts automatically. (Please referVendor manual for relief valve set pressure)

• Discharge of the relief valve is connectedback to the tank. Pressure gauge is providedwith a Snubber and a Diaphragm, snubberhelps to dampen the fluctuating pressure anddiaphragm avoids direct contact of chemicalsand the gauge internals. One drain providedafter the pressure gauge is used to releasepressure while adjusting the relief valve setting.Also it can be used to check the flow.

• According to the system, discharge line ofthe H.P dosing is connected to Steam Drum.Supports at required elevations are given.All the piping in the system is to withstandcorrosive chemical solution.

2.8.2.2 Amine Dosing System (PH DosingSystem)

Amine dosing is required continuously to keepfeed water quantity as per recommendedparameters. Feed water pH may reduce due tomixing of condensate at deaerator. In order toboost the pH of feed water, 2.5% concentratedsolution of Cyclohexyl Ammine to be preparedfor continuous dosing to make up water line tode-aerator vapour tank. Dosing pump stroke areset to get required Ph.

The quantity has to be sufficiently diluted anddosed in 24 hrs.

Description Of Dosing System Skid

Total system is mounted on a Base frame.Chemical-mixing tank made of SS of capacity500-litres for dosing is provided, where thechemical is mixed with water for 8/24 hrs dosing.Following are the attachments of the tank - A levelgauge, One mixing water connection, one drain,one over flow connection with isolation valves,one motorised agitator for proper mixing of thesolution and a perforated screen at the inlet toavoid foreign material entry.

Amine Dosing Pumps

Two amine dosing pumps (A & B) of have beenprovided, out of which one is for service at a time,and the other is a standby. The pumps are plunger

Section B 19


operated reciprocating, positive displacementtype. The stroke of the plunger can be altered tovary the capacity of the pump as per requirement.The pump is driven by a motor through a gearbox.The vendor manual of the pump and gearbox isavailable with full information on construction andparts detail.

Pump suction line is tapped of from the bottom ofthe tank. It is connected to the pump through anisolation valve and a strainer. A direct connectionof the DM water is iven in between strainer andisolation valve for flushing of the discharge piping& strainer. Y strainer traps dirt or other solidparticles in its basket. The Y strainer is to becleaned once a month, after stopping the pumpand closing its inlet and outlet isolating valves.


• In the discharge line a pulsation dampener isgiven to dampen intermittent discharge fromthe pump. On the discharge side of the pump, apressure gauge and two outlet isolating valvesare fitted before the common discharge line. Asafety relief valve has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure atleast oncea year. The pump must not be operated withthe relief valve continuously operating. (Causeof relief valve operation must be found andrectified). The pressure gauge is fitted with adampening device to minimize pulsations onthe gauge when the pump is in service.

• The common discharge line is connected to thedeareator DM & condensate water line throughan NRV and an isolation valve. The isolatingvalve is verified open before boiler light up andnormally remains open all the time.

• Availability of a minimum level in the mixingtank is a pre condition for starting or runningof the dosing pumps. For this purpose a levelswitch has been provided for the tank thatalso gives level low signal LSLL 774A0, whichis interlocked to dosing pumps to preventaccidental start-up during low tank level. Outof the two pumps, one pump is selected forservice and the other is in reserve (DCS macro,Local panel). The pumps are interlocked suchthat when a working pump trips, the reservepump starts automatically. (Please referVendor manual for relief valve set pressure)

• Discharge of the relief valve is connectedback to the tank. Pressure gauge is provided

with a Snubber and a Diaphragm, snubberhelps to dampen the fluctuating pressure anddiaphragm avoids direct contact of chemicalsand the gauge internals. One drain providedafter the pressure gauge is used to releasepressure while adjusting the relief valve setting.Also it can be used to check the flow.

• Supports at required elevations are given.All the piping in the system is to withstandcorrosive chemical solution.

2.8.2.3 O2 Scavenging System (LP)

Removal of dissolved oxygen/gases from boilerfeed water is essential. Presence of dissolvegases can cause corrosion and pitting of feedwater lines, steam line or condensate lines,boiler tubes and other pressure parts resultingin pre-matured failure of pressure parts or otherexpensive plant shut down.

Sodium sulphite (catalysed or un-catalysed) orhydrazine is to be used for oxygen removal fromboiler feed water. The major amount of dissolvedoxygen is removed in deaerator by mechanicaldeaeration. The remaining traces of oxygen areremoved by reacting with chemical (sodium sulfiteor hydrazine).

Description Of Dosing System Skid

Total system is mounted on a Base frame.Chemical-mixing tank made of SS of capacity500-litres for dosing is provided, where thechemical is mixed with water for 8/24 hrs dosing.Following are the attachments of the tank - A levelgauge, One mixing water connection, one drain,one over flow connection with isolation valves,one motorised agitator for proper mixing of thesolution and a perforated screen at the inlet toavoid foreign material entry.

O2 Scavenging Pumps

Two phosphate dosing pumps (A & B) of havebeen provided, out of which one is for service ata time, and the other is a standby. The pumpsare plunger operated reciprocating, positivedisplacement type. The stroke of the plungercan be altered to vary the capacity of the pumpas per requirement. The pump is driven by amotor through a gearbox. The vendor manualof the pump and gearbox is available with fullinformation on construction and parts detail.

Pump suction line is tapped of from the bottom ofthe tank. It is connected to the pump through anisolation valve and a strainer. A direct connectionof the DM water is given in between strainer andisolation valve for flushing of the discharge piping

Section B 20


& strainer. Y strainer traps dirt or other solidparticles in its basket. The Y strainer is to becleaned once a month, after stopping the pumpand closing its inlet and outlet isolating valves.


• In the discharge line a pulsation dampener isgiven to dampen intermittent discharge fromthe pump. On the discharge side of the pump, apressure gauge and two outlet isolating valvesare fitted before the common discharge line. Asafety relief valve has also been fitted on thedischarge line to relieve any over pressures incase of closure of valves on the discharge line.The outlet of the relief valve is returned to themixing tank. The relief valve must be tested forits operation at the set pressure at least oncea year. The pump must not be operated withthe relief valve continuously operating. (Causeof relief valve operation must be found andrectified). The pressure gauge is fitted with adampening device to minimize pulsations onthe gauge when the pump is in service.

• The common discharge line is connected tothe LP dosing line of the De-aerator throughan NRV and an isolation valve. The isolatingvalve is verified open before boiler light up andnormally remains open all the time. Dosing isthrough a perforated pipe along the full lengthof the water space in the de-aerator.

• Availability of a minimum level in the mixingtank is a pre condition for starting or runningof the dosing pumps. For this purpose a levelswitch has been provided for the tank thatalso gives level low signal LSLL 775A0, whichis interlocked to dosing pumps to preventaccidental start-up during low tank level. Outof the two pumps, one pump is selected forservice and the other is in reserve (DCS macro,Local panel). The pumps are interlocked suchthat when a working pump trips, the reservepump starts automatically. (Please referVendor manual for relief valve set pressure)

• Discharge of the relief valve is connectedback to the tank. Pressure gauge is providedwith a Snubber and a Diaphragm, snubberhelps to dampen the fluctuating pressure anddiaphragm avoids direct contact of chemicalsand the gauge internals. One drain providedafter the pressure gauge is used to releasepressure while adjusting the relief valve setting.Also it can be used to check the flow.

• According to the system, discharge line of thescavenging pump is connected to De-aerator.

Supports at required elevations are given.All the piping in the system is to withstandcorrosive chemical solution.

Flushing Line

In the system, the chemical mixing water line isconnected to the pump suction line also, calledas flushing line. This is provided to clear the linewhenever there is no need for dosing.

Whenever the dosing is stopped, always there isa chemically concentrate water is stagnant insidethe piping. If this liquid is not evacuated, it maytend to solidify and settle inside the piping, whichwill create a problem for free flow of chemicalwhenever the dosing is re-started.

Whenever the dosing is stopped, first close themixing tank outlet valve and open the flushing linevalve, operate the pump for 2 hrs. In this process,the chemically concentrated water is replaced withthe clear water; thus choking of piping can beavoided.

2.8.3Sample System

This sub-section provides an overview of thesample collection and cooling system providedon the boilers.

The sample system includes the sample coolerand the associated analyzers and the coolingwater sub-system

Sample Coolers :-

There are four sample coolers provided in theboiler to get Saturation steam, boiler feed water,drum sample and main steam sample

One sample cooler is provided for drum watersample emerging out from the continuous blowdown line. Sample cooler two is provided for thesuperheated steam sample from main steam line.Sample cooler three is provided saturation steambefore steam entering in to superheater. Samplecooler four is provided to feed water line samplewater before entering in to drum

The sample coolers are simple shell and coiltype heat exchangers. In these sample coolers,the sample is passed through the coils while thecooling water is passed around the coils on theshell side.

Individual sample coolers are provided withisolation valves on the cooling water inlet &cooling water return lines. The cooling water isprovided from the plant.

Section B 21


3 Valve Positions Chart (BeforeLight Up)

Valve Tag no. Service Open Close Remarks

FEEDWATER LINE TO STEAM DRUM

BW017,BW018

Upstream and downstreamisolation valves of flow controlvalve (FV7018AA)

YTo be closed when thecontrol valve is undermaintenance

BW013,BW014

Upstream and downstreamisolation valves of flow controlvalve (FV7018AB)


BW009,BW010

Upstream and downstreamisolation valves for level controlvalve LV7018A


BW011,BW012

Drain after level control valve(LV7018A) Y

To be closed whencontrol valve is undermaintenance

BW015,BW016

Drain after flow control valve(FV7018AB) Y

To be closed when flowcontrol valve is undermaintenance

BW019,BW020

Drain after flow control valve(FV7018AA) Y

To be opened when flowcontrol valves are undermaintenance

ATTEMPERATER LINE

DSH001 Attemperation line isolation valve Y To be closed only formaintenance of line

DSH006,DSH007

Upstream and downstreamisolation valves for flow controlvalve (TV7018C)

YTo be closed only forthe maintenance of flowcontrol valve

DSH008,DSH009 Drain after flow control valve Y

To be opened only forthe maintenance of flowcontrol valve

TV-7018C Attemperation water flow controlvalve Y Operated from DCS

DSH010 Bypass to flow control valve YTo be opened only duringthe maintenance of flowcontrol valve

SD007, SD008 Attemperater drain IsolationValves Y

To be closed whencondensate is drainedcompletely at 5 bar (g)pressure.

ECONOMIZER

ECO001,ECO002

Economizer top header VentIsolation Valves. Y

To be open only duringinitial filling or draining ofEconomizer/ boiler.

ECO005,ECO006

Economizer bottom header VentIsolation Valves. Y


Section B 22



FD004, FD005, Economizer Top header DrainIsolation Valves. Y


FD007, FD008 Economizer bottom header DrainIsolation Valves. Y


STEAM DRUM & MAIN STEAM LINE

DM039,DM040

Drum vent manual isolation valveof Y

To be closed whendrum pressure reaches2 bar (g) during boilerpressurization.

NI002,NI 004 N2 preservation connection YTo be opened only whenboiler is to be preservedwith N2

DM021,DM022,DM023,DM024

Isolation Valves for manifold onSteam Drum for Level IndicatingInstruments.(LT7018A)

YTo be closed duringmaintenance of leveltransmitter

DM001,DM002,DM003,DM004,

Isolation Valves of Steam DrumLevel Gauge Glass (LG7018A) Y

To be closed duringmaintenance of levelgauge

DM007,DM008,DM009,DM010

Isolation Valves of Steam DrumLevel Gauge Glass (LG7018B) Y


DM025,DM026,DM027,DM028,

High level switch (LSHH7018B)isolation valves Y

To be closed duringmaintenance of levelswitch

DM029,DM030,DM031,DM032

Low level switch (LSLL7018C)isolation valves Y

To be closed duringmaintenance of levelswitch

DM038,DM039 Auxiliary connection Y

SH001,SH002,SH003, SH004

Saturated steam line vent valves Y

To be closed whendrum pressure reaches2 bar (g) during boilerpressurization.

sd001,mov7018-asd004,mov7018-b,

Superheater Inlet & OutletHeader Drain Y

To be closed whencondensate is drainedcompletely at 5 bar (g)pressure.

MS001,MS002 Main steam line vent Y

To be closed when drumpressure reaches 2 bar(g).

Section B 23



MS011, MS012 Main Steam line drain beforeMSSV Y

To be closed whencondensate is drainedcompletely.

MOV7018-C Isolation Valve of Startup VentValve Y

To be opened beforeopening start up ventvalve.

MOV7018-E Motorized Pressure EqualizationValve of Main Steam Stop Valve Y To be opened for

equalization of pressure.

MOV7018-D Motorized Main Steam StopValve Y

To be opened afterreaching the ratedPressure.

DM043,DM044 Rear wall vent isolation valves Y

To be open only duringinitial filling or draining ofboiler.

BLOWDOWN SYSTEM

BD001,BD002, BD003 CBD Isolation Valve Y

To be closed only forthe maintenance of CBDvalve

MOV7018-F CBD control valve Y To be opened as perrequirement.

FD016, FD017 IBD Isolation Valve of IBD Line Y To be closed only formaintenance of IBD valve

BD013 IBD Valve from Water Drum. YTo be opened when IBD isrequired to be given. Andduring initial filling

DRAIN SYSTEM

FD019 Drain Header to Blowdown Tank, YTo be opened when drainis to be routed to theBlowdown Tank.

FD001, FD002,FD003 Rear wall header drain valve Y

To be open only duringinitial filling or draining ofboiler.

FD010, FD011 Drain header draining valves YTo be open for draining ofdrain header/ Boiler duringshutdown to atmosphere.

BD005, BD006 Isolation valves for level gauge(LG737AO) Y


BD009 Blowdown tank drain valve

BD010 Quenching water to Blowdowntank Y

To be throttled asper quenching waterrequirement

FUEL GAS SYSTEM

N-001 Inert gas isolation valve Y To be open for purging ofthe line with N2.

Section B 24



FG-001 Natural Gas Main Isolation Valve YTo be Closed when boileris under Shut down forLong period.

FG007,FG008,FG017, FG014

Natural Gas line drain valves YTo be kept closed andopened to drain line toremove condensate.

FG013 Vent isolation valve Y To be opened for manuallyventing fuel gas.

XV-7012 B Fuel gas MFT valve Y Will be opened/Closedfrom BMS command

FV7012A Fuel Gas Flow Control Valve Y

PV7012 C Fuel Gas pressure control valve Y

FG003,FG004,

Fuel gas flow control valveupstream & downstreamisolation valve.

YTo be closed when flowControl Valve is underMaintenance.

FG005, FG006Fuel gas pressure controlvalve upstream & downstreamisolation valve.

YTo be closed whenpressure Control Valve isunder Maintenance.

FG009 Manual isolation valve of headervent shut off valve Y

To be closed only formaintenance of ventvalve(XV-7012G)

XV-7012 G Gas line vent shutoff Valve Y Will be Opened/Closedfrom BMS Command

FG010 Fuel gas to burner A isolationvalves Y To be closed when burner

is under maintenance.

XV-7014DA,XV-7014DB,XV7014E

Block & Bleed Valves (Burner“A”) for main gas line Y Will be Opened and

Closed by BMS command

PILOT GAS SYSTEM

FG051 Pilot Gas Main Isolation Valve Y To be Closed during longShutdowns

PCV 7013 Pilot gas pressure control valve Y To be set at requiredpressure

FG055 Manual isolation valve of headervent Y To be opened for venting

pilot gas line

FG052 Burner A Pilot gas isolationvalves Y To be Closed during

maintenance

XV-7014H,XV-7014GA,XV-7014GB

Block & Bleed valves (Burner“A”) for pilot gas Y Will be Opened and

Closed by BMS command

COOLING AIR SYSTEM

SA-01, SA-02,SA-03, SA04,SA05, SA06

Isolation valves for Cooling Air toScanners Y

To be Closed onlyduring Maintenance afterensuring that Furnacetemperature is below 80Deg C

Section B 25



ATOMIZING STEAM SYSTEM

SM037,SM038

Atomizing steam line battery limitisolation valves Y To be closed during

maintenance

SMO43,SM044

Isolation valve of Pressurecontrol valve (PV7011A) Y To be closed during

maintenance of PV7011A

SM003,SM005

Strainer upstream anddownstream isolation valves Y To be closed when the

strainer is to be cleaned

SM007,SM008

Isolation valves of differentialpressure control valve(PDV7011B)

YTo be closed duringmaintenance ofPDV7011B

SM012 Bypass of differential pressurecontrol valve (PDV7011B) Y

To be opened duringmaintenance ofPDV7011B

SM009,SM046

Drain after differential pressurecontrol valve (PDV7011B) andbypass valve (SM012)

YTo be opened duringmaintenance and drainingof condensate

XV-7014C Atomizing steam to burner Ashutoff valve Y Will be Opened/Closed

from BMS Command

SM027 Main gun atomizing shutoff valve Y To be closed duringshutdown

SM028 Auxiliary gun atomizing shutoffvalve Y To be closed during

shutdown

XV-7014B Clearing steam line shutoff valve Y Will be operated by BMScommand

SM018 Clearing steam to main oil gunisolation valve Y To be closed when the

gun is under maintenance

SM019 Clearing steam to auxiliary oilgun isolation valve Y To be closed when the


SM011, SM002 Isolation valves for steam trapSM035 & SM036 respectively Y

To be closed formaintenance of steamtrap

SM039,SM040,SM040,SM042,SM001,SM010

Drains for condensate YTo be opened duringcharging/shutdown toremove condensate

ATOMIZING AIR SYSTEM

SM013 Atomizing air battery limitisolation valve Y

To be closed only for themaintenance of atomizingair line

SM045,SM015

Strainer upstream anddownstream isolation valves Y To be closed when the

strainer is to be cleaned

SM007,SM008

Isolation valves of differentialpressure control valve(PDV7011B)

YTo be closed duringmaintenance ofPDV7011B

Section B 26



SM012 By pass of differential pressurecontrol valve (PDV7011B) Y

To be opened duringmaintenance ofPDV7011B

SM009,SM046

Drain after differential pressurecontrol valve (PDV7011B) andbypass valve (SM012)

Y To be opened duringmaintenance

XV-7014C Atomizing air to burner A shutoffvalve Y Will be operated by BMS

Command

SM027 Main gun atomizing shutoff valve Y To be closed duringshutdown

SM028 Auxiliary gun atomizing shutoffvalve Y To be closed during

shutdown

XV-7014B Clearing air line shutoff valve Y Will be operated by BMScommand

SM018 Clearing air to main oil gunisolation valve Y To be closed when the


SM019 Clearing air to auxiliary oil gunisolation valve Y To be closed when the


FUEL OIL SYSTEM

DF001 Diesel oil battery limit isolationvalve Y To be closed only for

maintenance.

DF002, DF003Upstream and downstreamisolation valves of flowtransmitter

YTo be closed only formaintenance of flowtransmitter

DF004 Drain for flow transmitter Y To be opened only formaintenance.

DF005 Bypass valve of mass flowtransmitter Y

To be opened duringmaintenance of flowtransmitter

DF006, DF007Upstream and downstreamisolation valves of flow controlvalve

YTo be closed only formaintenance of controlvalve.

DF009, DF010Upstream and downstreamisolation valves of pressurecontrol valve (PV7010B)

YTo be closed only formaintenance of controlvalve.

DF008 Drain for flow control valve line YTo be opened only formaintenance of flowcontrol valve (FV7010A).

DF011 Drain for Pressure control valveline Y

To be opened only formaintenance of pressurecontrol valve (PV7010B).

XV7010D Main flow trip valve Y Will be Opened/Closedfrom BMS Command

DF024 Oil header drain valve Y To be opened only formaintenance.

XV7014A Burner A shutoff valve Y Will be Opened/Closedfrom BMS Command

Section B 27



DF012 Auxiliary oil gun isolation valve YWill be closed when mainoil gun is to be taken inline

DF013 Main oil gun isolation valve YWill be opened when mainoil gun is to be taken inline

DOZING SYSTEM

HP023, HP021 HP dozing isolation valves YTo be closed only formaintenance of dosingline

FWT07,FWT008

DM water to dozing tank isolationvalves Y To be closed during

shutdown.

SAMPLING SYSTEM

SAM003,SAM004

Feed water sample line isolationvalves Y

To be closed duringmaintenance of sampleline

SAM005,SAM006 CBD sample line isolation valves Y


SAM007,SAM008

Saturated steam sampling lineisolation valves Y


SAM001,SAM002

Superheated steam samplingline isolation valves Y


Note

Root valves of all the instruments to bekept open. Ensure vent and drain valvesof all instruments are closed.

Note

Above Philosophy is explained for burnerA only. Same philosophy is to be followedfor other burners

All above description is based on followingdrawings:

• P&I Dagram for Steam and Water systemD12-0FM-3232P

• P&I Diagram for Firing D12-1FM-6516P Sheet1 & 2

4 Air and Flue Gas System

The air and flue gas system covered in thissub-section describes the supply of combustionair to the boiler and forcing of the flue gas throughthe boiler to the stack.

The components that form part of the system are-

• FD fan

• Air duct

• Windbox

• Furnace

• Flue ducts

• Service air for Peepholes

4.1 FD Fan

The FD fan supplies combustion air to the burners.(The Vendor manual for FD Fan is included inVolume-III, which may be referred).

FD fan is of centrifugal type, with aerofoilbackward curved blades. FD fan is equipped withmotor drive, driven by an electrical motor.

The principal parts of the fan are described asbelow:

Casing - The casing envelops the impeller.The casing is fabricated out of carbon steelplates and stiffened by angles welded outside tostrengthen the casing to resist vibration when thefan is in service. The casing is of split designto enable removal of impeller if required, without

Section B 28


disturbing the fixing arrangement of the casing tothe foundation. An inspection door fitted on thecasing enable inspection of the impeller duringshut down. The casing has a drain to drain anyaccumulated water. The inlet cone provides astream lined smooth passage for the suction air.Base plate is the arrangement for supporting thefan bearing housing and the motor.

Impeller : Impeller is fabricated out of carbonsteel plates. The blades of the impeller are ofaerofoil backward curved design. The impeller isstatically and dynamically balanced at the worksto minimize vibrations during operation.

Shaft with bearings : The impeller is mountedon the shaft with a key arrangement in its hub andthe shaft. The shaft rests on two simply supportedbearings placed on either side of the fan. Thebearings are anti – friction, double row sphericalroller type and Grease lubricated. A spring gridtype resilient coupling couples the fan to the clutchand then to the drive. Sealing plates have beenfitted at each end of the casing to minimize airleakage through the shaft opening on the casing.

Technical Data For Fd Fan -


Make Andrew Yule And Co. Ltd

Model SI.BCB-92

Quantity 02 No. 1 x 60%

Nature of medium Clean Air

17.24 (Associated Gas)

17.16 (Raageshwari Gas)Design Mass Airflow (MCR) Kg/s

17.4 (LDO)

Air Temperature at Fan Inlet Deg C 40

Absorbed Power at operating temp. withspeed control KW 160

Fan Speed Rpm 1480

Inlet Static Pressure mmWC -35

Outlet Static Pressure mmWC 417

Free/Fixed Bearing 22218C (Anti Friction) + HousingSAF-218

Bearing Lubrication VEEDOL ALITHEX – 20 or eqvt.Grease (500 gms for first fill)

Motor 200 kW /4 Pole, Type-M38M/GM355LK4; ABB MAKE

Coupling Flexible spacer type (80SPL-262-140)

Model / Make MAKE- Metaflex

FD Drive Motor

A squirrel cage induction motor of 160 kWcapacity drives FD fan, working on 6-phasepower supply with DOL starter. The motor istotally enclosed and force cooled by air. Therated operating speed of motor is 1485 rpm. Themotor winding is of class F insulation but windingtemperature rise is restricted to class B (120 DegC) and motor protection class is IP 55.

4.2 Air Duct

FD Fan Suction Duct

The FD fan is provided with a suction ductfor sucking the combustion air from the plantenvironment.

The suction duct is provided with a rain hood anda bird screen.

An absorption type silencer is installed toattenuate the noise.

Section B 29


A control damper (inlet guide vane) has beenfitted at the suction of the FD fan. The pneumaticactuators [FV 7150-A] are provided to operatethe damper, which is modulated by the signalfrom airflow indicating controller [FIC 7150].The actuator is provided with position feed backswitches for the 0% & 100% opening, which areused as safety interlocks for fan start permissiveand furnace purge cycle respectively.

FAN Discharge Duct

FD fan Discharge Duct connects the FD fan withwindbox.

To measure the flow of combustion air to theburner, an aerofoil [FE 7150] is installed in thedischarge of the FD fan. Flow transmitters [FT7150] measure the pressure drop across theaerofoil, which will be converted into flow signalat DCS.

4.3 Windbox

The air duct terminates in the windbox. Burnersare accommodated in the windbox. The windboxis fabricated out of carbon steel and mounted onthe boiler front wall. The windbox has suitableopening for mounting the burner front plate andfor connecting the combustion air duct. Windbox facilitates proper air distribution around theburners.

Combustion Air Flow Control

The control of FD fan output to meet thecombustion air requirements of the boiler isbeing presented. The airflow given is inclusiveof the recommended excess air for completecombustion.

The pressure at wind box is for providing thedesired velocity and swirl required for completemixing of air with fuel gas and to force the productsof combustion through the boiler, economizer andfinally to the stack.

Out of the two requirements of airflow quantity andwind box pressure, the later is determined by thesystem resistance to flow of the flue gas by burnerthroat size.

FD fan damper control is the only devicefor delivering the required quantity of air forcombustion of the required quantity of fuel toproduce the required steam flow from the boiler.Combustion controller determines the fuel flowrequired for the steam flow, demanded from theboiler, computes the air required for that fuelflow from the Air/ Fuel ratio memory set on the

controller and sends demand signals to the fuelflow and the air flow controllers.

Combustion air flow is measured by the air flowtransmitter [FT 7150] using the principle that thepressure drop across an aerofoil is proportional tothe volume of air flowing through it. The air flowsignal is fed to the air flow indicating controller[FIC 7150], which compares it with the remoteset point received from the combustion controller,develops a deviation signal where necessary andpositions the inlet damper of the FD fan throughthe pneumatic actuator [FV 7150-A].

The combustion controller set point providesthe programmed air required for combustion.In actual practice, it may happen that thisair may either be a little more or a little lessthan the desired excess air, measured by theoxygen content in the flue gas, for most efficientcombustion. To obtain the desired O2 contentin the flue gas, the measured O2 signal fromthe analyzers [AT 717A0] are fed to combustioncontroller to trim the airflow set point to [FIC7150].

With certain digital outputs from the BMS, the[FIC 7150] output is forced to pre determinedvalues. They are 0%, 20%, 50%, 75%,& 100%.During FD fan startup, the actuator is forced to afull close position so as to have minimum load onthe motor during the fan startup period. Duringthe burner light up, the FD actuator is forced tothe 20% position which ensures the minimumrequired airflow for the burner light up and forpurging the furnace, the actuator is forced to the50% position.

The flow transmitter [FT 7151A/B/C] are in linewith the [FE 7150] to generate the air flow LOW[FSL 7151] and LOW LOW [FSLL 7151] signalbased on the output generated by comparing twoout of three output from transmitters.

Two fans of 60% capacity provided for the boiler.Both the fans have the outlet isolation damper [XV7151] and [XV 7152].

Oxygen Trimming

% Oxygen in the flue gas is measured usingan Oxygen analyser [AT-717A0] & is takenas process variable to Oxygen controller[AIC-717A0]. This is compared with the remoteset point, which is in turn varied according toBoiler Load. The remote SP is actually a functionof Steam flow. Oxygen Low alarm shall begenerated if the O2 value is less that the requiredvalue by 10%. This alarm shall be based on theSteam flow.

Section B 30


Execess Air Adjustment

In any burner system it is necessary to have airflow in addition to theoretical air flow to ensureproper combustion of the fuel being fired. Theamount of excess air depends on the burnerload at lower load quantity of excess air is highercompare to excess air at higher load. The Oxygencontent in flue gas outlet is function of excess air.

For combustion control the amount of excess airrequired shall be computed from Remote set pointof oxygen which is function of total burner load.

4.4 Furnace

The construction of the furnace is such that atotally gas sealed enclosure suitable for forceddraft operation is available.

The boiler block is provided with inner andouter casing for making suitable for forced draftoperation. The inner casing is of carbon steel andcovered by mineral wool insulation for personalprotection. The outer casing of carbon steelsheets & corrugated aluminum cladding furthercovers the insulation.

The furnace floor tubes are covered with refractorybricks to maintain natural circulation of waterinside the tubes.

The front wall is covered with refractory bricks andhigh temperature castable refractory is applied atthe Burner throat.

Studded rear wall and the boiler sidewall aresealed with castable high temperature refractory.Furnace peephole areas and the furnace cornersare sealed with castable refractory.

The furnace and the second pass chambers havebeen provided with drains that remain normallyplugged. They are to be used to drain water washeffluents during a shut down of the boiler or todrain out the accumulated water due to any tubefailure.

Instruments on flue path of furnace:

• A tapping has been provided in the roof wall tomeasure the furnace pressure. [PT 7017-A] isprovided for local indication.

• Three numbers pressure transmitters [PT 7017BA/BB/BC] are provided for remote indicationof the furnace pressure and for furnacepressure high alarm generation.

Access Door And Peepholes

Bolted access door is provided on the boiler frontwall for the access to the furnace. To prevent

the heating of the door during the operation of theboiler, the access opening is filled with refractorybricks and completely sealed before the door isbolted into position. Peepholes are provided onthe furnace sidewall and the rear wall to view theburner flame. The peepholes are pressurized andcooled by service air.

Boiler Base Frame

The base frame supports the entire boiler. Thebase frame anchored to the concrete foundation.The base frame anchors the water drum at frontside so that during operation the Boiler is allowedto expand vertically upwards and on rear side andalso allows the furnace to expand sidewise.

4.5 Flue Duct

Flue gases generated in the furnace, pass throughthe convection bank tubes in the second pass tothe economizer and then to stack. Flue ducts areprovided to connect the boiler to the economizerand the economizer to the stack.

The flue duct is fabricated from 6mm thick plates.The duct is provided with insulation mineral wool(120kgf/m3 density) of 75mm thick and thenprovided with aluminum cladding.

To isolate the thermal expansions of the flueduct from the boiler, economiser and the stack,expansion joints have been provided. Theexpansion joints are provided at the exit of theboiler block (1 no.), entry to the economizer (1no.), exit of economizer (1 no.) and entry to stack(1 no.)

The following instruments are provided on the ductfrom boiler to economizer –

• Temperature element [TE 733A0] for boiler exitflue gas temperature indication on DCS

• Local Pressure indicator [PT 733A0] for fluegas draft at boiler exit

The following instruments are provided on the ductfrom economizer to stack

• Temperature element [TE 717A0] foreconomizer outlet flue gas temperatureindication

• Pressure indicator [PG 717A0] for flue gasdraft at economizer outlet

• Flue gas oxygen analyzers [AT 717A0] formeasuring the oxygen in flue gas.

Stack

The stack exhausts the flue gases from theeconomizer to the atmosphere. The stack is a

Section B 31


cylindrical steel chimney fabricated out of carbonsteel plates. The stack is 30 m height and has aninternal diameter of 2.3m

The following have been provided on the stack -

• Sampling nozzles (4 nos.), for the analysis offlue gas for environmental pollution monitoringat an elevation of 20.1 m

• A drain connection from the base ring fordraining of rain water from the stack

• Access door for inspection and cleaning of thestack during shutdown.

• Platforms at EL+9500, +19000, & +28500elevation with ladder for accessing them.

4.6 Cooling Air For Peepholes

Cooling air connection is given to the peepholesto protect the peepholes from the radiationof the furnace. Cooling air connection isprovided through service air connection fromplant Individual peepholes on the boiler rear andfurnace sidewall and burner front are providedwith isolation valves and flexible hose.

Operational Control


FD FAN

• Ensure that the couplings are properly bolted• Ensure that the bearings are properly lubricated• Ensure that the inlet damper of the fan isclosed before starting the fan

• Ensure that the access doors on the fan casingare closed before proceeding to start the fan

General

Expansion joints (after boiler block, before theeconomizer and after economiser) may bechecked once in six months to ensure theymaintain their permissible dimensions. Collapseor stretching of the joints is to be attended duringthe next boiler maintenance program.

5 Fuel Firing System

This sub-section describes the burners installed inthe boiler and also the fuel lines with their valvesand instruments for burner light up, monitoring,control and shut down.

5.1 Components Description

The system consists of the following -

• Burner• Fuel Gas Oil & Pilot Gas Supply Pipe To TheBurner

• Burner Front Piping• Burner Technical Data• Burner Management System (Bms)• Local Burner Panel• Operational Control

5.1.1Burner System

This chapter describes the burner installed in theboiler with fuel lines together with their valves andinstruments for their light up, monitoring, controland shut down.

System Description

Two STS oil burners of Thermax Babcock &Wilcox design have been fitted on the frontwall panel of the boiler over the wind box.These burners are capable of efficient and safecombustion of fuel with low excess air and lowemission levels. The igniters and the oil guns arefitted with flame monitors and remote operatedshut off valves for supervision and control by theBurner Management System (BMS) describedin Chapter to ensure safety during light up andoperation.

The principal components of the circularindustrial burner are:

1. Front plate2. Air Register assembly3. Sleeve4. Swirler5. Gas chamber and spuds6. Fuel oil atomizer (gun) assembly7. Igniter8. Flame scanners9. Peep hole / view ports

1. Front Plate

The front plate forms the structural attachmentbasis of the burner components. Front plate ismounted directly to the windbox front face byframes with series of equi-spaced bolts along foursides of the front plate.

2. Air Register Assembly

The air register consists of a series of vanesarranged circumferentially in the air passage fromthe wind box to the oil gun, axially surroundingthe impeller of the gun. All the vanes operate

Section B 32


uniformly through linkages on a shaft, end ofwhich is located outside the oil burner housingin the front. The required movement of vanes isobtained by less than a quarter turn of the shaft.The vanes which overlap each other in the closedposition, by swinging through 55 0 on turning theoperating shaft, reach full open position.

The air register vanes provide a (rotary) swirlingmotion to the combustion air, which it imparts tothe mist of atomized fuel oil being sprayed by theoil gun, enabling the air and the oil mist to mixintimately for quick and complete combustion. Inthe ‘closed’ position of the air register vanes, exitof air is more tangential, increasing the swirl ofthe atomized fuel. In the ‘open’ position of thevanes, the combustion air exit is more radial, witha reduction in the swirl. Velocity of combustion airto the burners is high when the vanes are in closedposition. It decreases as the vanes are opened.Air velocity determines the

starting point of flame with respect to the gunimpeller and also the stability of the flame. Airregister vanes in the ‘close’ position offer moreresistance to airflow than in the ‘open’ positionand thereby increases the wind box to furnacedifferential as also the wind box pressure.

Air registers are not to be used for control of airquantity to the burners. (Air quantity adjustmentsare only by varying the FD fan output). Air registeradjustments are for obtaining optimum swirl of thefuel air mixture and suitable velocity of the airstream to produce a well-shaped flame.

A well-shaped flame has the followingcharacteristics

• Starts slightly away from the swirler of the oilgun.

• Does not touch the water walls

• Light orange in color.

• No sparks or smoke around the flame.

The Air registers are produced with clock-wiseswirls of the air stream. In this boiler, Burners A B& C all are clock wise swirls.

Air register vanes of the three burners arepositioned by power cylinders & by solenoidvalves on command from BMS. The percentageopening of the power cylinders are registeredback in BMS.

The BMS requires 100% of air register openingas a pre condition for furnace purge. Afterfurnace purge, before boiler light up, the airregister opening is set at 20%. Suitable settingsof the register ‘20%’ and ‘100%’ openings are

determined during initial commissioning of theBoiler.

3. Sleeve

Burner sleeve makes the air distribution andbalancing across the cross section of the burner.The design assures equal air distribution andacceleration of air to the required velocity forcomplete mixing with fuel. Air from windboxenters into the burner through para flow damper isaccelerated to a velocity in multiple of the windboxvelocity and also diverted axially into the burner.The converging cone of sleeve further acceleratesthe air and also distributes it equally across thecross section. Re-accelerating the air forces topass through and around the impeller. Pressuredrop is an effective means of assuring evenairflow distribution at higher flow rates. Its effectat lower flow rates is reduced, as the pressuredrop is proportional to the square of the airvelocity. Thus, at higher turn down conditions it ismore difficult to maintain the burner performanceand flame shape using only the pressure dropprinciple. To measure the pressure drop acrossthe burner tapings are provided in wind box &furnace. Sleeve assembly accommodates thegas spuds, oil gun, impeller and igniter and alsosupports them.

4. Swirler

A circular swirler of diameter 406 mm and havingvane type blades is mounted on the regulating rodof the burner gun assembly. Air passing throughthe swirler is referred to as primary air, whichgets further accelerated due to the pressure dropacross swirler. The primary air is imparted witha swirl, which is a function of the swirler bladeangle. This additional acceleration and swirlinggives the air the strength to penetrate and mixwith the fuel.

The swirl gives the air an outward trajectoryfrom the centerline of the burner. The outwardtrajectory creates a low-pressure regionimmediately in front of the swirler. This referredas primary combustion zone volume. The sizeand shape of this zone is dependent on swirlerblade angle, swirler diameter, swirler pressuredrop and position of the swirler with respect to thethroat. The important feature of this zone that itre-circulates the surrounding gases back into thezone. The size and re-circulating strength of thiszone are critical to the flame stability and to theability to retain the desired flame shape.

The air distributed around the swirler is termedas secondary air. The secondary air provides theoxygen for complete combustion process.

Section B 33


5. Gas Chamber & Spuds

Fuel gas is introduced through eight equallyspaced gas spuds located in the secondary airannulus. Gas for the spuds is introduced throughthe gas chamber mounted on the burner frontplate. The gas spuds are drilled with injectionorifices, properly sized to provide the correctvelocity to the exiting gas. In addition, the spudsare angled such that the gas is directed forimproved mixing with air to give proper flameshape and minimum emissions. More small holesare provided in the circumference of the pipe justbehind these gas holes called stabilizer holes. Forshielding the root flame a cover plate is weldedbehind the gas holes.

6. Fuel Oil Atomizer- Gun Assembly

The gun uses the energy of expanding steam toatomize the fuel oil, that is to divide the oil intovery fine particles for spray as a mist, for completemixing with air for easy combustion.

The fuel oil gun is composed of two concentricpipes to lead steam and oil up to the atomizer.Atomizer comprises of mixing chamber andsprayer cap. Fuel Oil flows through the innerpipe and reaches to the atomizer at the end.Steam/Air, which flows outside the inner tube,enters the atomizer through tangential slots inthe mixing chamber of the atomizer, mixes withoil and atomizes it. The pressure energies of oiland steam get converted into velocity energy ofthe furnace – steam/air mixture and sprays intothe furnace through the holes in the sprayer cap.The screwed sprayer cap of the oil gun keepsthe mixing chamber, the oil and steam pipestight without leakages. The mixing chamber andthe sprayer cap are precision machined ground,hardened and lapped for this purpose and requirecare in cleaning. Soft nylon brushes with a solventsuch as diesel oil can be used for cleaning. Theimpeller is bolted on to the gun serves to guidethe combustion air around the atomized oil sprayfor intimate mixing and shields the tip of the sprayfrom high air velocities, to initiate combustion.

The oil gun is inserted through a outer pipe inthe burner assembly called regulating rod. In theannular space between the gun and the outerpipe, air is admitted from the wind box throughthe holes provided in the peripheral of rod to coolthe gun and also to seal from the pressurizedfurnace.

The burner throat is made of special refractorywork to withstand furnace radiation. The axis ofthe burner assembly is aligned to coincide with

the axis of the burner throat. The oil gun axiscoincides with the burner axis.

The axial position of the gun in the burner can bevaried by sliding the regulating rod in or out by afew millimeters, so that the oil spray from the gunand the flame clear the burner throat to obtain awell defined flame. The ideal position found duringcommissioning is secured by a set bolt. Oil sprayon the refractory surfaces will cause incompletecombustion and dripping of oil to the furnace frontwall and floor.

7. Ignitor Assembly

Ignitor is a gas (pilot gas/LPG) fired lighter withan electric sparking device, which produces a pilotflame to light the fuel air mixture of the main fuel.Establishing the pilot flame and sensing it by ascanner is a pre-requisite for admission of mainfuel to the burner.

The Ignitor consists of a gas nozzle to admit pilotgas to a combustion chamber where the gasmixes with the combustion air. The gas nozzle isconnected to the pilot gas supply line.

A spark device is an electrode with 3-mm gapfitted on an insulator. The electrode is connectedto a High - tension transformer in the burner localcontrol box through an H.T. cable.

The sequence of operations for placing in servicethe ignitor of a burner is controlled by BMSand will be described in upcoming section. Abrief outline is now given for understanding thesequences. On an auto start command of burnerBMS energizes for 5 seconds the sparking devicewith HT supply from the ignition transformer inthe local panel to produce steady sparks in thecombustion chamber. BMS opens the pilot gasvalves & to admit gas to the ignitor combustionchamber where it mixes with air and lights up bythe spark already present.

Availability of the flame in the ignitor is viewedby Flame scanner and enables BMS to issuea command for admission of main Fuel. Ona normal auto start, the sequences of spark,opening of the gas valve, establishing a pilotflame, and establishing the main flame isexpected to be completed within 10 seconds.BMS shuts off the ignitor gas valve after 10seconds.

8. Flame Scanners

Each Burner is provided with two FIREYEmake flame scanners (One Ultra Violet (UV)flame scanner & another one is Infrared flame

Section B 34


scanner) in the scanner view pipes for continuousmonitoring of the flame and provide an input toBMS. Vendor’s manual of the scanner may bereferred for more details. A brief description of theprinciple of operation of the scanner is given. The‘detector’/ UV cell of the scanner is a sealed, gasfilled, ultra-violet transmitting envelope containingtwo electrodes, connected to an A.C. voltage.The detector is aligned to view the flame whereasIR flame scanner is based on photon transistor.

When the flame is there the UV rays/radiationstriking the electrodes makes the gas betweenthe electrodes conductive and a current flowfrom one electrode to the other in the form ofpulses. Number of pulses emitted per second arecharacteristic of the flame and differs from otherradiation (for example from the hot refractories)striking the scanner. The pulses are amplifiedand compared with a pre-set value to detect thepresence of flame. The scanner tube is swivelmounted to enable adjustments of the detector fora full view of the flame. Out of these two scannersone is positioned in such a way that to detectthe pilot flame properly while light up. However,main flame is detected by both the scanners.To cool the scanners from the heat of flameradiation, scanner cooling air is connected to thescanner view / mounting tube. The UV cell alsorequires cleaning at regular intervals to maximizeits performance. The scanner ‘flame On’ inputof burner, to BMS keeps the shut off valve offuel to open, when the burner is in service andimmediately closes it when no flame is sensed.

In general IR flame scanner justify presence of oilflame as it is having more infrared spectrum in it’sflame front whereas UV flame scanner justify thegas flame.

9. View Port

The Burners are provided with peepholes with aninner glass shield and a tiltable outer cover onburner front plate to monitor the flame by operatorduring burner start up / running. As the boileris pressurized, sealing air is connected to thepeepholes. The burner peepholes are used tothe view the flame for carrying out adjustments. Itis recommended to monitor the flame from boilerside peepholes as to get better judgement offlame.

5.1.2Fuel Gas, Oil, Pilot Gas & AtomizingSupply Pipe to the Burner

1. Fuel PipingFuel Oil Supply (Associated /Raageshwari)

Fuel oil supply to the burner is provided withthe following -

• Main isolation valve [1FG001] at theterminal point.

• Differential pressure transmitters [PDT7012] for indicating gas pressure acrossstrainers [F-1 and F-2] with three way valve[1 FG-020].

• Tapping (with isolation & NRV) fromNitrogen header for line purging &preservation.

• Flow orifice [FE 7012A] with a transmitter[FT 37012A] for fuel gas flowmeasurement.

• Temperature element [TE 7012A] usedfor indicating gas temperature as well forcompensating the gas flow

• Pressure transmitter [PT 47012A] usedfor indicating as pressure as well forcompensating gas flow

• Main fuel gas trip valve [XV-7012B]. Thisvalve is a solenoid operated safety shut offvalve. The valve is provided with positionfeedback arrangements for the open andclose positions.

• Fuel gas flow control station: The fuel gasflow control station consists of a pneumaticoperated spring opposed globe typecontrol valve [FV 7012A]. The control valveis provided with isolation valves. A bypassself acting pressure control valve [PV7012] completes the flow control station.The bypass control valve is for maintainingthe minimum pressure required for startupof the burner. The startup pressurecontrol signal is obtained from [PT 7012C]pressure transmitter.

• Transmitters [PT 7012 DA/DB/DC] logicinterlocked to the BMS for fuel gas lowand high pressure parameter with 2out of3 logic.

• A normal pressure transmitter [PT 7012E]with pressure HIGH alarm in DCS.

• Local pressure indicator [PG 7012B] forindicating fuel gas pressure.

• Header vent valve [XV 7012G]. Thevent valve is interlocked with the BMSand automatically opens in case of highpressure after the control station beforestartup of the burner.

• Nitrogen purging connection is available.Nitrogen from plant is connected with an

Section B 35


isolation valve and NRV for purging of fuelgas during long shutdown periods.

2. FUEL OIL SUPPLY (Diesel Oil No. 2)Fuel oil supply to the burner is provided withthe following -

• Main isolation valve [1DF-001] with aspectacle blind flange at the terminalpoint [Pressure gauge [PG 7010GA forindicating oil pressure]

• Flow orifice [FE 7010A] with a transmitter[FT 7010A] for fuel oil flow measurement.

• Fuel oil flow control station: The fuel oilflow control station consists of a pneumaticoperated spring opposed globe typecontrol valve [FV 7010A]. The control valveis provided with isolation valves. A bypassself acting pressure control valve [PV0710B] completes the flow control station.The bypass control valve is for maintainingthe minimum pressure required for startupof the burner. The startup pressurecontrol signal is obtained from [PT 7010B]pressure transmitter.

• Transmitters [PT 7010 CA/CB/CC] logicinterlocked to the BMS for fuel oil low andhigh pressure parameter with 2 out of 3logic.

• Local pressure indicator [PG 010B] forindicating fuel gas pressure.

• Temperature element [TE 7010] for localindication

• Main fuel gas trip valve [XV-7010D]. Thisvalve is a solenoid operated safety shut offvalve. The valve is provided with positionfeedback arrangements for the open andclose positions.

3. Pilot Gas SupplyPilot gas for the igniter torch is taken fromthe natural gas supply piping. An isolationvalve [1FG 051] and a self-acting pressureregulator [PCV-7013] are provided. Apressure indicator [PG 7013] are providedto indicate the gas pressure. A pressuretransmitter [PT 7013] is provided to indicateHigh and Low pressure in DCS.

A NRV (1FG-016) along with a manuallyoperated ball and needle valve [1FG-015]isolates the line from the main fuel line. Anadditional NRV [1FG-056] is also providedin Pilot line in tandem with main fuel lineconnection tapping in order to isolate the pilotline when main fuel shall be used as pilot fuelinstead of LPG.

4. Atomising Steam And Air Supply

• Atomizing steam is obtained from thesteam drum (4750 kPa (g) through anisolating valve[1SM-037 & 1SM-038].

• A pressure control valve is provided toreduce the pressure up to <1700 kPa (g)which the set pressure for the line pressurerelief valve[PSV 7011].

• A pressure transmitter [PT 7011A] isprovided to generate the High and Lowalarm through [PIC 7011A] and give thefeedback to [PV 7011A] in order to regulatethe header steam pressure to desired limit.

• Another pressure transmitter [PT 7011B] togenerate High High and Low Low alarm inDCS with burner interlock.

• A steam trap [1SM-035] is provided toremove the condensate after [PV 7011A].

• An NRV [1SM-004] is provided to isolatethe steam line from Air atomization whensteam is not available followed by anisolation valve [1SM-003].

• An NRV [1SM-014] is provided to isolatethe Air line from Steam atomization whensteam is available followed by an isolationvalve [1SM-045].

• Atomising air from plant at 700 kPa (g) isprovided with an isolation valve [1SM-013]for initial atomization purpose when steamis not available.

• Both Steam and Air line then combinestogether after the globe isolation valves[1SM-005] and [1SM-015] respectively.

• A pressure gauge [PG 7011A] is providedfor local indication.

• A differentials pressure control valve[PDV 7011B] is provided to maintain thespecified pressure difference with DieselOil line. This valve receives the signalfrom differential pressure transmitter [PDT7011B]. The differential pressure controller[PDIC 7011B] compares the pressurebetween Diesel Oil header and AtomizingLine in order to generate the requiredpressure difference across.

• Pressure transmitters [PT 7011 BA/BB/BC]are provided to generate the High high andLow Low alarm.

• A pressure gauge [PG 7011B] is providedfor local indication.

• A temperature gauge [TG 7011] is providedfor local indication.

Section B 36


5.1.3Burner Front Piping

The burner front piping involves the piping thatconnects the fuel oil, pilot gas and combustionair to the burner. The major components includethe safety shut off valves, damper. They aredescribed below

1. The fuel gas (Associated / RaageshwariGas) burner front piping is provided with thefollowing - (For Burner “A”)-

• Isolation valve [1FG-010]

• Block & bleed arrangement for burnersafety shut off valves

• Two-safety block shut off valves [XV7014DA] & [XV 7014E] are provided with avent shut off valve [XV 7014DB] in betweenthem. This arrangement of two shutoffvalves and an intermediate vent valve iscalled a block & bleed arrangement. Allthe shut off valves are connected to theBMS and interlocked for safe operation ofthe burner.

• Pressure indicator [PG 7014E] for localindication of the fuel gas pressure.

• Flexible hose connects the front piping tothe burner.

2. The Diesel Oil burner front piping is providedwith the following -

• Isolation valve [1DF-027]

• One shut off valve cum ramp up valve[XV 7014A] is provided. This valve isconnected to the BMS and interlocked forsafe operation of the burner. This valve ishaving the BMS interlock with a functionblock for ramp up of burner for smooth lightup.

• A manual three way valve [1DF-030] isprovided after shut off valve [XV 7014A]from which two lines are connected to mainand auxiliary gun of burner. A three wayvalve is having limit switches to indicatethe open position in BMS whether maingun [ZSM 7014JB] or auxiliary gun [ZSA7014JA] is in line for running burner.

• The limit switches for main gun [ZSI 7014A]and auxiliary gun [ZSI 7014B] are providedto indicate the inserted position of maingun and auxiliary gun respectively.

• An interlock for main and aux. gun isprovided in such a way that, for light upof burner with recommended main gun, athree way valve limit switch [ZSM 7014JB],

main gun inserted limit switch [ZSI 7014A]and atomizing media three way valve limitswitch [ZSM 7014KB] feedback should beavailable.

• The auxiliary gun can be fired in the eventof chocking of main gun by ensuringauxiliary gun at inserted position withavailability of atomizing media at auxiliarygun and by placing the three way controlvalve towards auxiliary gun.

• Pressure indicator [PG 7014A] for localindication of the fuel gas pressure.


3. The Atomizing Steam burner front piping isprovided with the following –

• Isolation Valve [1SM-049]

• A Shut off valve [XV 7014C] with limitswitches and interlock with BMS. Aminimum flow orifice [MFO 7014C] asbypass.

• A NRV [1SM-026] to restrict the back flow.

• A three way valve [1SM-027] with limitswitches to indicate the position (Main gun[ZSM 7014KB] or Aux gun[ZSA 7014KA])is provided.

• Pressure gauges for Main gun [PG 7014C]and Auxiliary gun [PG 7014D] are provided.


• A tapping is routed to main gun andauxiliary gun from first isolation valve [1SM049] for gun clearing purpose with isolationvalves.

4. The pilot gas front piping is provided with thefollowing -

• Isolation valve [1FG 052]

• Block & bleed arrangement for pilot gasburner safety shut off valves - Two-safetyblock shut off valves [XV 7014H] & [XV7014GA] are provided with a bleed shutoff valve [XV 7014GB] in between them.This arrangement is similar to that of themain burner. All the shut off valves areconnected to the BMS and interlocked forsafe operation of the pilot burner.

• Pressure indicator [PG 7014F] for localindication of the pilot gas pressure

• Flexible hose connects the front piping tothe burner

Section B 37


The burner is provided with a damper on itscombustion airside. This is used for isolatingthe burner airside during non-operation of anindividual burner. The damper is providedwith a position feedback arrangement on itopen and close positions and interlocked tothe BMS.

Note

FORABOVEDESCRIPTIONREFERP&IDIG. D12-1FM-6516P REV-4 (Sheet I &II)

5.1.4BURNER TECHNICAL DATA

Description

MAKE THERMAX BABCOCK & WILCOX LTD.

MODEL Industrial Circular Oil Cum Gas Burner

No. of burners per boiler 3

Capacity of each burner(% MCR) 36.67%

No. of oil gun provided in each burner 2 (One Main + One Auxiliary Gun)

Type of air control & accessories Lead lag arrangement, VIV at FD fan suction.

Burner Throat Dia, inch 32”

Type & no. of gas spuds Variable Mix Type Gas Spuds, 8 Nos.

No. of holes per spud 4

Oil Gun Atomiser I jet

Swirler/Impeller information Swirler

Fuel Fired Associated Gas / Raageshwari Gas Diesel OilNo. 2

Turn Down (auto) 4.4:1 / 3.1:1 3:01

Fuel for Igniter Natural Gas

Pilot gas pressure 1440 kPa (g)

Excess air at burner % @ design heatrelease rate 15% for Oil, 10% for Gas

124110 - Associated Gas

123580 - Raageshwari GasTotal air required all burner Kg/hr

125265 - Diesel Oil No.2

41370 - Associated Gas (Ambient)

41193 - Raageshwari Gas (Ambient)Air req. per burner Kg/hr & Temperature

41755 - Diesel Oil No.2 (Ambient)

182 - Associated Gas;

180 - Raageshwari GasBurner pressure drop mm WG

185 – Diesel Oil

30.939 – Associated Gas

30.822 – Raageshwari GasHeat Input per Burner Mkcal/hr

29.513 – Diesel Oil No.2

3890 – Associated Gas

2180 – Raageshwari GasFuel fired (max) per burner Kg/hr

2604 – Diesel Oil No.2

Section B 38


Description

84.38 – Associated Gas

84.06 – Raageshwari GasQ fired (Total on HHV) Mkcal/hr

80.49 – Diesel Oil No.2

Oil Pressure at tip inlet at peak (Psi) 120 (anticipated)

Diff Steam Pressure at tip inlet at peak 10.5 kg/cm2

12.95 - Raageshwari GasQuantity for Pilot Fuel (Nm3/hr)

19.51 - Associated Gas

Burner Flame

Maintaining a well-shaped flame, light orange incolor, stable without sparks or smoke surroundingthe flame is an essential requirement for stableoperation and high thermal efficiency. Theunder mentioned factors contribute towards goodcombustion.

• Correct fuel oil combustion air ratio andair register settings. These are controlledautomatically. The combustion control and airregister control must be fine tuned not onlyduring commissioning but also once every sixmonths, by checking the flame and analyzingthe flue gas at furnace exit or Economizer IIexit for CO, CO2 & O2.

• The local Operator must be encouraged toview the flame in the boiler two or three timesin a shift and report any malfunctions. Thelocal Operator must view the flame throughthe peephole from one side. Before viewing,availability of sealing air to the peephole mustbe checked and the Operator should usea shielding glass to protect his sight whileviewing.

Clean Gun

Atomization will not be proper in a clogged gun.Steam cleaning may be adequate to clear thegun most of the time. Disassembly and manualcleaning of the atomizer, steam and oil pathsand spray plate may have to be done at leastonce a month (or as often the conditions mayrequire). Correct assembly of the gun is neededafter manual cleaning. To save time required forcleaning, a spare gun may be installed, whena gun is withdrawn for cleaning. The cloggedgun can be cleaned without affecting the boilerloading. Before a cold start of Boiler, ensure thatall guns have been manually cleaned.

• Fuel Oil at gun inlet must be at a temperatureof about 15-40 0C with the viscosity of oil to 2to 5 CST for proper atomization.

• Availability of de-superheated atomizing steamwithout moisture at pressure of 15kg/cm2 andair at 7 kg/cm2 at oil gun Inlet. De-superheatedsteam is used as superheated steam maypromote carbonization of oil in the gun.Moisture in steam cause sparks in the flame.

• Concentric position of the gun in the burnerthroat (ensured during maintenance andoverhauls) and axial position of the gun toavoid spraying on to the refractory. • Goodcombustion from the gun requires some skillbut a new Operator easily

• acquires it by observation and simple training.

As the spark device of the ignitor, gas spuds,flame detectors must be maintained in goodcondition by following the vendor instructions.Suitable preventive maintenance schedules forservicing and checking their performance atregular intervals may be drawn up.

Burner Capacity

The oil guns have been designed to operatebest between fuel oil pressures of 1.5 kg/ cm2and 6.5 kg/cm2.To meet the boiler steam flowrequirements it is desirable to operate minimumnumber of burners within their design capacity.As the combustion control functions on auto, theOperator should provide margins in the gunscapacity for the control to function. When multipleburners are in service the Operator should :

• Remove one burner from service if the fuel oilpressure to the burners approaches minimumvalue.

• Take one more burner into service if the fuel oilpressure is near the maximum design value.

The fuel oil to the guns must be maintainedclean, free from dirt by monitoring the differentialpressure across the duplex filters and bringingthe reserve basket into service when the d/pincreases. If during cleaning, holes are noticedin the basket, the damages must be repaired.

Section B 39


If frequent cleaning is needed, oil filters in theplant pumping and heating station may have tobe checked.

As the spark device, gas nozzle, flame detectorof the ignitor influences the quick light up of theoil gun and the UV flame scanner of the oil gunkeeps the gun in service, these equipment mustbe maintained in good condition by followingthe vendor instructions. Suitable preventivemaintenance schedules for servicing andchecking their performance at regular intervalsmay be drawn up.

The emergency scanner cooling air must becontinued at least for eight hours after a boilershut down to shield the scanner from the boilerheat.

For the safety of the equipment (and personnel)protections envisaged in BMS must not be bypassed. Any mal-operation of protections ornuisance trips must be analyzed and causescorrected.

Possible fire risks in handling pressurized andheated fuel oil must be recognized. To avoidaccidents the following are suggested.

• House keeping should be of a high order. Fueloil lines and valves must be accessible. Oilleakages from valve glands, bonnet joints,flanges, instrument tapings if any noticed mustbe promptly attended.

• Operators are to be trained for fighting oil fires.

• Portable fire fighting equipments in workingcondition should be readily available.

• Smoke, automatic fire detection, gas leakdetection systems must be periodically tested.

Other Safety

The scanner cooling air must be continued at leastfor eight hours after a boiler shut down to shieldthe scanner from the boiler heat.

For the safety of the equipment (and personnel)protections envisaged in BMS must not be by

passed. Any mal-operation of protections ornuisance trips must be analyzed and causescorrected.

Possible fire risks in handling pressurized andgaseous fuel oil must be recognized. To avoidaccidents the following are suggested.

House keeping should be of a high order. Fueloil and valves must be accessible. Fuel gas /Oil leakages from valve glands, bonnet joints,flanges, instrument tapings if any noticed must bepromptly attended.

Portable fire fighting equipments in workingcondition should be readily available.

5.1.5Burner Management System

The Burner Management System (BMS) is aprogrammable logic controller (PLC) that controlsthe permissive for burner start, stop and tripfunctions. The PLC acquires the status from thefield instruments. The PLC and its hardware areinstalled in independent PLC panel. The PLCsystem consists of a CPU, power supply unit, I/Omodules & communication modules. The BMSPLC is provided for the burner safety interlocks/monitoring of related shutoff valves & Alarmgeneration.

The PLC system is programmed and configuredas per the BMS logic drawings and the I/O list.

The burners can be started / stopped either fromlocal burner panel Installed on the operatingplatform near the burners or from the DCSoperating station placed in control room. The localburner panel is provided with necessary lampsand pushbuttons for operation & Indications. PLCis provided with necessary software and hardwarefor communicating with DCS.

5.1.6Local Burner Panel

The following indicating lamps / push buttons areprovided on the local panel –

Tag No Description

LHS 7012 Emergency stop

LHS 7010 Lamp test

LHS 7011 Furnace purge start

LHSO 7014A Diesel burner start

LHSO 7014B Gas burner start

LHSC 7014A Diesel burner stop

LHSC 7014B Gas burner stop

Section B 40


Tag No Description

LHS 7013 Reset

XL 7016 Main interlock satisfied

XL 7017 Pre interlock satisfied

XL 7014A Diesel ready to start

XL 7014B Gas ready to start

XL 7014C Pilot on

XL 7014D Diesel firing on

XL 7014E Gas firing on

XL 7013 Furnace purge required

XL 7012 Furnace purge ready to start

XL 7014 Furnace purge running

XL 7015 Furnace purge finished

XL 715AA FD fan running

5.1.7OPERATIONAL CONTROL


BURNER

The under mentioned factors contribute towardsgood combustion.

Correct fuel gas to combustion air ratio. Thecombustion control must be fine tuned not onlyduring commissioning but also once every sixmonths, by checking the flame and analyzing theflue gas at economizer exit for O2, CO & CO2.The local operator must be encouraged to viewthe flame in the boiler two or three times in a shiftand report for any irregularity.

As the spark device, gas nozzle and UV flamescanners must be maintained in good conditionby following the vendor instructions. Suitablepreventive maintenance schedules for servicingand checking their performance at regularintervals may be drawn up.

The scanner cooling air must be continued atleastfor eight hours after a boiler shut down to shieldthe scanner from the boiler heat.

For the safety of the equipment (and personnel)protections envisaged in BMS must not beby-passed. Any mal-operation of protections ornuisance trips must be analyzed and correctiveactions initiated.

Possible fire risks in handling pressurized andheated fuel gas must be recognized. To avoidaccidents the following are suggested -

• House keeping should be of a high order.

• Fuel gas lines and valves must be accessible.

• Gas leakage, if any, noticed must be promptlyattended.

• Portable fire fighting equipment in workingcondition should be readily available at anaccessible location

Section B 41


Section — C


♦ Section Overview♦ Boiler Start Up and Shut Down♦ Boiler Hot Startup Pressure Raising Curve♦ Boiler Warm Startup Pressure Raising Curve♦ Boiler Shutdown♦ Boiler Emergency Trip♦ Boiler Operation♦ Boiler Safety♦ Tube Failures♦ Trouble Shooting Chart♦ Water Quality Recommendations

1 Section Overview

This section describes the startup, shut downprocedures of the boiler. Boiler operation andsafety are also described.

2 Boiler Start Up and Shut Down

This chapter describes the boiler start up and shutdown procedures as applicable for the followingboiler conditions:

1. Start up of a Cold boiler

2. Start up of a Warm boiler

3. Start up of a Hot boiler

4. Boiler shut down

Note

The procedures explained in this chapterapply for start up of the boiler alreadycommissioned. Commissioning anew boiler call for several additionalrequirements.

Note

It is assumed that Operators are fullyfamiliar with the design and constructionfeatures described in the earlier section.

Note

It is assumed that Operators are trainedin operation of similar type of boilers andhave been licensed to operate boilers bythe State Boiler authority.

Note

The owner is encouraged to evolvestandard operating procedures(SOP) based on the framework andrecommendations that are explainedin the subsections below. The SOPshave to be well understood by operatingpersonnel for safe and reliable operation.

2.1 Startup of a Cold Boiler

Boiler startup can be termed as cold startup whenthere is no pressure or when pressure is less than2-bar (g) in the steam drum.

In a cold start up, possibilities of some inspectionor maintenance work having been done ispresumed. A walk down check is required andthe boiler and its auxiliaries are to be preparedmeticulously for a start up from the DCS of thecontrol room. Before a walk down check ensurethat all work permits have been returned, safetytags are removed and maintenance permissionfor boiler start up is available.

Walkdown Checks

Using powerful torches or low voltage inspectionlamps, inspect the furnace and the second passof the boiler and ensure the following:

DEAERATOR

• Ensure that the deaerator drain /overflowpiping are terminated safely to the trench.

• Safety Relief valves are in proper workingcondition and their outlet piping is completed tothe requirement and supported properly.

• Check level gauges are in working condition.

• Check that all the instruments are ready forservice.

• Ensure that make-up water is available fordeaerator filling.

• Ensure that the steam is available at thedeaerator inlet line for charging Deaerator

• Ensure that Deaerator is filled with Dm waterupto normal water level.

• Ensure that the boiler/s running at considerableload or ensure that enough and continuous outflow of water is available.

Boiler

• Furnace and second pass are clear, allmaintenance personnel have been removedand no scaffolding or inspection devices havebeen left inside.

Section — C 42


• Furnace floor, water walls and second passconvection tubes are clean and there is noevidence of any water drips, slag or any otherdeposits.

• Steam and water drums are clear andmanholes are closed properly.

• Verify that all access doors, inspection doors offurnace and wind box are tightly closed.

• Verify that all peepholes have been tightlyclosed and sealing/ cooling air connectionshave been made and the air valves are open.

• Verify that the air duct, windbox, externaleconomizer and flue gas duct to stack is clearand that all maintenance personnel have beenwithdrawn. Ensure that the manhole doorsclosed properly.

• Verify that the safety valves are not gagged.

• Verify that the illuminators of local level gaugesare ’ON’. Inlet valves from steam and watersideis open and their drain valves are closed.

• Verify whether the Nitrogen purging valves areopen (connected to the steam drum and mainsteam piping). If they are open, they have tobe closed just before boiler light up, when airvents are opened.

Burner

• Verify that the pilot, fuel gas, oil & atomizingsteam/air flexible hoses are connected to theburner.

• Verify that the Ignitor has been inserted in theburner housing and that the HT cable has beenconnected to the igniter.

• Verify that the Flame Scanners have beeninstalled properly, cooling air hoses areconnected and valves are open.

• Verify that the air slide dampers fully open andair supply to actuator is available.

• Verify physically and in DCS that the fuel shutoff valves is fully closed and bleed valves areopen.

• The manually operated fuel isolating valves areto be verified for shut. These valves have to beopened just before boiler start up.

FD Fan

• Check that the fan inspection doors are closed.

• Ensure that the bearing lubrication is doneproperly.

• Check that the coupling guards are installed.

• Ensure that the damper actuator is properlyfixed to the operating lever and air supply isopen to actuator and I/P Converter.

General

Ensure that the battery limit valves are open andthe inputs are available:

• Instrument air and Service air.

• Feed water upto level control station.

• Power up of feeders for FD fan motor.

• Fuel oil and pilot gas up to terminal pointisolation valve.

• Phosphate dosing at terminal point.

• Cooling water supply at terminal point.

2.1.1System Line Up

Preliminary Requirements

• Power supply: Ensure that the power supply isswitched ’ON’ and available for all the motorsand panels.

• Operating station - DCS is ensured forreadiness and emergency push buttons arereleased, if activated.

• As instrument air is necessary for the operationof most of the valves and actuators, chargethe instrument air header, the branch linesand instruments supply lines elsewhere. Rootvalves of all Instruments (Pressure gauges,Pressure transmitters, DP transmitters, Levelgauges, etc.,) must be kept open and theirdrains if any are to be kept closed. They arenot separately listed.

• Ensure that all the transmitters are lined upmechanically / electronically.

Deaerator

• It is always recommended that the deaeratorhas to be taken in line at lower load/ the wateroutflow is less. It would be easier to control theparameters and there won’t be any hurry instabilizing the system. It is also recommendedto take deaerator inline, as the boiler/s arestarted and steaming out, so that the risk ofcorrosion and pitting will be minimised.

• Open the vent valve at the top of vapour tankto atmosphere. Line up all the instruments ondeaerator system.

Economiser

• Keep the air vent on the inlet & outlet header ofthe Economizer open. These valves will have

Section — C 43


to be closed when sufficient air was releasedfrom it at the time of filling.

• Ensure that the drain valves of top and bottomheaders are kept closed.

• Ensure that the drain valves of common lineis kept closed

Steam And Water Drum

• Ensure that the drum vent valves [DM 039/04]is kept open. These valves will have to beclosed when the drum pressure attains 2 bar(g).

• Open the CBD line isolation valves BD 001/002and keep close the CBD valve MOV 7018-F.

• Keep close the IBD line isolation valvesFD016/017 and the IBD valve [BD 013].Thesevalves to be operated only at the time of blowdown operation under personal supervision &close after completion of blow down operation.

• Keep open the phosphate dosing line isolationvalves [HP 021/023].

• Verify that drains and vents of Stand pipesprovided for level transmitters, indicator &gauges are closed.

Feedwater Water Line

• Select the drum level and feedwater flowcontrollers in manual mode. Keep close thebypass manual valve. Fill-up water in boiler byremote opening main control valve till boiler isfilled to recommended drum level.

• The control station drain valve to be keptclosed.

Superheater

• Ensure that the drain valves SD 004, MOV7018-B, SD 001 & MOV 7018-A are kept open.This is to ensure that the superheater coilsare totally drained before lightup of boiler.Attemperator drain valves SD 007 & 008 canbe kept open.

• Verify that the vent valves on saturated steamsupply pipes to Superheater are closed.

• Keep open the startup vent isolation valveMOV 7018C. The Pressure control valve [PV7018B] has to be kept open 100% during boilercold startup and let the controller (PIC 7018BA)remain in manual mode. This valve can bemanually placed/throttled till boiler reaches toits rated pressure and temperature. Put PIC7018BA in auto mode once boiler is connectedto plant mains.

• Ensure that the MSSV (MOV 7018D) andpressure equalization valve (MOV 7018E)

is in close position. MSSV to be open forconnecting boiler to the plant mains.

Note

Never close the startup vent valve till theboiler is connected to the plant mains.

Feedwater And Spray Water Line

• Select the drum level and feed water flowcontrollers in manual mode. Keep close the110% control valves [FV 7018-AA/AB] Fill-upwater in boiler by manually opening LV 7018-A(30% MCR capacity) till boiler is filled torecommended drum level.

• The control station drain valves BW011/012/015/016/019/020 in upstream anddownstream to be kept closed.

• Select steam temperature controller TIC7018-C in manual mode with 0% output.

• Open the manual isolation valves DSH006/007/014/017

• Keep the drain valves DSH 008/009 closed.

Sample System

• All the sample lines isolation valves have tobe closed. Sample coolers can be taken intoservice once the boiler is pressurized. Ensurea slight bleeding through the sample line as theboiler is pressurized to 2 bar to ensure that nochoking of the line occur.

2.1.2Filling Water in Deaerator & Boiler

• During water filling, for assurance of correctdeaerator level, post an attendant at thedeaerator level to monitor the local gauges andto communicate to the control room when thelevel of NWL is reached.

• Fill the deaerator slowly through the makeupwater inlet connection by opening the deaeratorlevel control valve in manual mode. Watch thewater level in the level gauges and ensure thatthe gauges are indicating the correct waterlevel. Cross check with the level indicationavailable at control room through the leveltransmitter LT. Mark the normal water level onlocal level gauge when control room indicationreads ”0” mmWC. Stop the water supply to thedeaerator.

• Once, water level has attained NWL, thenslowly admit the steam into deaerator throughthe pegging steam line. It will take one or twohours to heat the water with pegging steam.When the water temperature reaches 60 to 700C, deaerator is ready for charging the steamthrough main supply line.

Section — C 44


The following procedure is adapted for filling theboiler:

• During water filling, for assurance of correctsteam drum water level, post an attendant atthe drum level to monitor the local gauges andto communicate to the control room when thelevel of ’50 mm’ below NWL is reached.

• Operator to ensure that the feed water controlvalves are closed and the controller is inmanual mode.

• Operators to open slowly the feed watercontrol station by opening the 30% flow controlvalve [LV 7016-A] and allow the water to fill inEconomizer and boiler. The valve has to bemodulated gradually so that the water does notrush too much.

• Water rises to the steam drum through theeconomizer. It will take minutes to fill water tothe required level.

• As water level in steam drum reaches’50mm’ below the NWL on local level gauge(confirmation by the attendant) or in levelindicator, water filling can be discontinued byclosing the valve.

Filling water temperature should not bemore than 38 deg C of the boiler metaltemperature. During filling of a cold boiler,the ambient temperature should be used asan indicator of the boiler metal temperature.Assuming an ambient temperature of 40deg C, the maximum temperature of fillingwater shall be 78 deg C.

2.1.3Charging of Deaerator

The following procedure is adapted for chargingthe deaerator (place deaerator in service)

• Charge the steam up to the pressure controlvalve to warm up the line and keep the steamreadily available for charging into deaerator.Once, water level has attained NWL, thenslowly admit the steam into deaerator throughthe pegging steam line. It will take one or twohours to heat the water with pegging steam.When the water temperature reaches 60 to 70°C, deaerator is ready for charging the steamthrough main supply line.

• Try to maintain a low water level beforeadmitting the steam through the main supply

line. Level may be maintained well abovethe very low level and below the centerlineof the tank. Due to direct scrubbing of steamwith warm or cold water there may be littlehammering or vibration in the storage tank.By keeping the low Water level the quantity ofthe water in the storage tank will be less andless steam will be required initially to heat it.Thus vibration or hammering can be reducedwhile pressurizing the deaerator. Keepinglow water level will have to be done manuallywatching the level in the direct level gauge andby maintaining the water intake manually, asthe Level Transmitter will be out off its range.

• Start charging the steam gradually by openingthe Pressure control valve. The water will beheated up and steam will start coming out ofthe vent. The deaerator pressure will startrising, say 0.2 to 0.3 bar (g). Local pressuregauge on deaerator storage tank and thepressure transmitter can be referred for thepressure rise. Care should be taken to rise thepressure gradually.

• At this point of time, increase graduallysteam flow and water flow simultaneously.Objective is to maintain Normal Water Leveland to increase deaerator pressure up to 0.3kg/cm2 (g) and to maintain it. Once there isconsiderable rise in temperature, admittingof steam in more quantity will not causehammering in the deaerator.

• Water and steam intake should besynchronised so that at no point of timedeaerator pressure shall go beyond 1.7 bar(g) and to vacuum pressure. More steam flowwill lead to increase in deaerator pressure andless steam flow than the requirement for thewater flow will lead to condensing of steam andwill result into reduction in deaerator pressure,even to vacuum pressure.

• As the deaerator pressure increases the watertemperature will start increasing. If the wateroutflow from deaerator is faster, then thetemperature rise will be faster.

• Once the level and pressure are reached to theset values the controllers can be put into automode. Temperature will reach automatically tothe operating value of 130 °C.

• Condensate return lines can be taken in tothe deaerator at this point of time as the levelcontroller is in auto mode.

• The vent valve can be throttled to optimise theventing steam flow, even it can be closed fullyand the steam flow can be through the orifice. If

Section — C 45


the water temperature has not increased to theoperating temperature means air envelopingtaking place and need to increase the venting.

• In the event of taking the Deaerator into line,if abnormal hammering or vacuum situation iscreated, stop admitting the steam and repeatthe whole charging process once again.

2.2 Charging of Fuel (Associated Gas/ Raageshwari Gas/Diesel Oil ),Automizing Steam & Air Line

Fuel gas lines must be checked carefully beforecharging to ensure that there are no possibilities ofleak through flange joints, valve bonnet, pressuregauge tapings etc., During charging if any minorleaks are noticed Maintenance personnel must becalled to attend to the leaks. In case of seriousleaks, charging must be abandoned; line to bedepressurized, purged and leaks to be attendedbefore proceeding further.

Fuel Gas line is charged for light up:

• Close the Inert gas isolation valve. • Verify thatthe root valves of all the instruments are open.

• Verify that all the fuel gas, diesel oil and Pilotgas trip valves (XV 7012B, XV 7010D and XV7014 H/GA respectively ) are in ‘close’ position- physically and in DCS.

• Close the isolation valves of each fuel line tillthe entire system will be lineup.

• Closed the isolation valve of nitrogen purgingline.

• Before the gas line charging, lineup the strainer[F-1 & F-2] & select any one strainer by manualisolation three way valve [1FG-020]. Keepclose the other strainer. Other strainer shall betaken on line at the time of main line strainerget choked or under maintenance.

• With information to the plant, crack openthe terminal point isolation valve [1FG-101].Observe gas pressure upto Block valve as thepressure transmitter [PG 7012A] read this.Observe for leaks if any.

• Observe that the pressure is settled and the[PT 7012A] controls it. Then slowly increasethe opening of the terminal point isolation valve[1FG-101] to full open position.

• Once it is ensured that the fuel gas is available.Normalize the Block valve (MFT) [XV 7012B] &[PV 7012C]. Keep close [FV 7012A].

• Pressure gauge [PG 7012B] installed in thefield for measuring burner inlet pressure.

• For fresh burner starter used PCV [PV 7012C]to get smooth/controlled burner light up,subsequently flow control valve [FV 7012A]can be opened for increasing the firing rate.

• At the time of burner startup [FV 7012A] shallbe set at closed position while [PV 7012C] shallbe set at 15% open position (the position shallbe set at the time of commissioning).

Charging Of Pilot Gas For Lightup:

Ensure the availability of LPG cylinder & industrialregulator to deliver rated pressure from cylinder.The discharge pressure is to be throttled bysuitably adjusting the self-acting PCV.

• Verify that all the instrument root valves areopen.

• Burner shut off valves (XV7014H, XV7014GA)are in closed position and vent valve(XV7015GB) is in open - physically and fromthe DCS PANEL.

• Ensure vent valve (FG055) is in close position.

• Ensure root valves of all pressure gauges(FG-151, FG-153) and pressure transmitter(FG-152) open.

• Open the line isolation valve & charge the pilotgas up to burner isolation valve.

• Set the PCV7013 to get required pressure.

Note

The above procedure is explained forburner A. Same procedure is to befollowed for burner B & C.

Charging Of Diesel Oil Line For Lightup:

Diesel oil is to be charged from battery limit toburner. The charging of fuel oil is done as follows-

• Verify that the root valves of all the instrumentsare open

• Ensure spectacle blind is de-blinded.

• The main fuel trip (XV7010 D) and burnermanual shut off valve (XV7014A) is in closedposition - physically and from the DCS PANEL

• Ensure root valves of all pressure gauges(DF101, DF-103, DF-107, DF-108) andpressure transmitters (DF-102, DF104,DF-105, DF-106) are open.

• The isolation valves for the flow transmitter(DF-002 & DF-003) up stream and downstream respectively are to be kept open.

Section — C 46


• Flow control valve upstream and downstreamisolation valves (DF-006, DF-007) are to bekept open

• Flow meter bypass valve (DF-005) is fullyclosed.

• Ensure that the flow control valve (FV7010A) infully closed position - physically and from DCS.

• Pressure control valve upstream anddownstream isolation valves (DF-009, DF-010)are to be kept open

• Ensure that the pressure control valve(PV7010B) in minimum opening position -physically and from DCS. Minimum positionof PCV will be decided at the time ofcommissioning.

• Ensure all drain valves (FD-004, DF-008,DF-011, DF-024) are closed.

• Open the isolation valve at the battery limit(DF-001). This will charge oil up to main shutoffvalve (XV7010D).

• PT 7017B, PG 7010B, PT7010CA, PT7010CB,PT7010CC & TT7010 will show pressureand temperature of oil after control valvesrespectively.

• Initially auxiliary oil gun is to be taken in lineso its manual isolation valve (DF-012) to beopen & kept closed the main gun burner inletisolation valve (DF013).

• While taking main oil gun inline so its manualisolation valve (DF-013) to be opened.

Note


Charging Automizing Steam Line:

• Verify that the root valves of all the instrumentsare open.

• Ensure strainer [SM – 006] is cleaned andproperly tightened.

• Isolation valves of strainer upstream anddownstream (SM-003, SM-005) are open.

• Ensure root valves of all pressure gauges(SM-001, SM-007, SM-008, SM-105) andpressure transmitters (SM-102 SM-103SM-104) are open.

• Ensure burner A atomizing line shutoff valve(XV7014C) and clearing line shutoff valve(XV7014B) is in close position physically andin DCS panel.

• Pressure control valve (PV7011A) is usedto control pressure of atomizing steam withfeedback from pressure transmitter (PT7011A).

• Isolation valves of differential pressure controlvalve (PDV7011B) upstream and downstream(SM-007, SM-08) are open.

• Bypass of PDV7011B (SM-012) is closed.

• Keep all the drain valves (SM-039, SM-040,SM-041, SM-042, SM-001, SM-002, SM-009,SM-010, SM-046) are crack open tillcondensate is drained.

• Once the condensate removed from steam linethen line up the steam trap and open the rootvalve of steam trap continuously.

• Open valves SM-037, SM-038, SM-043,SM-044 one by one to charge steam up toburner.

• Isolation valves (SM-018, SM-019) in clearingsteam line to be kept open.

• Main and auxiliary gun clearing line shutoffvalve (XV 7014B) to be operated through BMSlogic.

Note

Clearing line NRV location should benearest to the oil line as possible.

Note


Charging Automizing Air Line:

• At the time of initial firing if steam is notavailable, air can be used as atomizing media.

• Verify that the root valves of all the instrumentsare open.

• Ensure root valves of all pressure gauges(SM-102, SM-105) and pressure transmitters(SM-102 SM-103) are open.

• Ensure burner A atomizing line shutoff valve(XV7014C) and clearing line shutoff valve(XV7014B) is in close position physically andin DCS panel.

• Ensure strainer (SM 016) is cleaned andproperly tightened.

• Isolation valves of strainer upstream anddownstream (SM-003, SM-005) are open.

• Open valve (SM-013) to charge atomizing airup to burners.

Section — C 47


• Isolation valves (SM-018, SM-019) in clearingline to be kept open.

• When you charge the air all atomizing steamline valve should be closed

• Once the air will be charged up DP controlstation, valve line up philosophy will be thesame as atomizing steam charging.

Note


Place Fd Fan In Service

• Check that the suction damper is in the closedposition.

• Ensure that the power supply is available forthe feeder in MCC.

• FD fan can be started either from DCS orfrom local burner panel. The remote / localselector switch to be positioned according tothe startup location decided. Start the FD fanafter selecting the airflow controller into manualmode in DCS console and output as 0%.

• Observe that the fan runs up to speed andcomes into service.

• Observe that there are no excessive vibrations(by feel) in the bearings and no abnormal noisefrom the fan and motor.

• Observe the bearing temperature stabilizebelow 70 - 80 0C.

• Observe that the motor casing temperature isnormal.

• Now the fan is ready for furnace purge. Purgestart command may be given if required.

2.3 Boiler Startup and Pressurizing

The preparations for a boiler start up so fardescribed can be summarized as below:

• Walk down checks of the boiler, economizer,FD fan, air & flue ducts and pipelines.

• System / valves line up of the boiler &economizer, feed water system, steam line anddrain lines.

• Filling the boiler with feed water andnormalizing the drum level.

• Charging the fuel gas lines.

• Start up of FD fan.

Now the boiler is ready for light up. Before light upit is necessary to understand BMS logic.

Burner Light Up

BMS - Burner Management System controls thesafe start up, running and tripping of the burner.BMS is a combination of safety logic implementedin the PLC and field instruments required formonitoring the parameters for safe operation /safe shutdown of burners. BMS also generatesnecessary alarms required for safe operation ofburner.

Main Interlocks

In the process of burner light up, first step is tosatisfy the ’Main interlocks’. Following are thesafety interlocks to be made healthy condition toget ’Main Interlocks Satisfied’:

• Emergency stop push button not operated fromDCS, ESD, CCR & LBP

• Any one FD Fan Running

• Drum level not low-low

• Drum level not High-high

• Final steam temperature not high-high

• Air Flow not Low-Low

• Furnace Pressure not High-high

Following are the conditions required for Fuel gasfiring Interlocks:

• Fuel Gas Pressure not Low Low

• Fuel Gas Pressure not High-high

• Main Interlock satisfied

• Leak test completed

• MFT to open after leak test completed

Following are the conditions required for Diesel Oilfiring Interlocks:

• Atomizing steam pressure not low low

• Diesel oil pressure not low low

• Diesel oil pressure not high high

• Main Interlock Satisfied

These above conditions have to be satisfied toproceed further. Operating burner(s) will trip onfailure of any (or more) of the above conditions.In case of failure, the same has to be reset beforerestarting.

Furnace Purging

Purging is the process of pushing out / removingunburned combustible gases present in thefurnace before every light up of the burner. Thisis done by forcing air through the furnace as perNFPA guidelines. In this case the purging is donewith an airflow of 50% MCR for five minutes.

Section — C 48


Upon satisfaction of the main interlocks & otherpurge conditions, "Purge Ready For Start"indication will be available in Local burner paneland in DCS. Before pressing the purge start PBon panel, the operator has to manually positionthe air damper(IGV) of FD Fan to increase airflow about 50% air flow and satisfy the interlock.As soon as these purge interlocks are satisfied(Airflow >50%), five minutes purge cycle will bestarted and ’Purge Running’ will be indicated.On elapse of the five-minute purge timer ’PurgeCompleted’ will be indicated.

If there is any interruption during purging, " Purgerequired " will be indicated and re-purging has tobe done.

Following are the conditions which need tobe satisfied for having ‘Purge ready for start’condition:

• Any burner start up started

• No flame detected in furnace

• All burner block valves closed

• Main interlocks satisfied

• Purge not completed

• Furnace purge not running

On having ‘ Purge ready for start ‘, purge startPB is to be operated either from local or DCS,following events occur on operating purge start:

• Open command is given for all burner windboxdampers from BMS logic.

• Open command to FD fan damper for purgeposition

After all windbox dampers open and FD fandamper open to purge position air flow willincrease to purge value

Purge sequence proceeds further on satisfyingfollowing conditions

• All burner windbox damper open feedback

• Air flow at purge value (60TPH)

Above conditions ensure that sufficient air isavailable and purge path is free.

On satisfaction of above conditions, purgerunning indication is available. Purge continuesfor 5 minutes (i.e. 300sec) provided aboveconditions prevail. On completion of 5 minutes ofpurging, purging is completed & purge completedindication is available on LBP.

After purge finished command will be given to FDfan suction damper to light up position. This willbring down the airflow to start up position.

Purge required condition be generated onfollowing cases:

On having ‘ Purge ready for start

Purge start Push button is to be pressed eitherfrom LBP or SCADA screen, Following eventsoccur on pressing Purge start:

• Purge is not completed

• No burner is running

• No Furnace purge running

On completion of the furnace purge a stand timeof 10 minutes will commence during which time aburner must be successfully started. In the eventof failing to start burner within this time the systemwill revert to furnace purge required status. ThenPurge should be carried out again.

Following indications concerning purge areprovided in Local burner panel:

• Furnace Purge Ready for Start

• Furnace Purge required

• Furnace Purge running

• Furnace Purge Finished

For Fuel Gas (Associated / Raageshwari)

• FD fan damper has to be set to the burnerstartup position manually by operator (minimumopen position / about 20%) this will satisfy “AirFlow at light off valve” condition.

• Fuel gas flow control valve have to be set forclose position. PRV [PV 7012C] to be set at15% open position( Final position to be set attime of commissioning).

• Operator has to open the battery limit manualisolation valve [1FG-101] manually. Fuel gaspressure in the header would be normalizedby the Pressure control valve [PV 7012C], apressure transmitter PT 7012C will generatehigh & low alarm in the event of pressurisation.Permissive will be available to open the Shutoff valves [XV 7012B] & close vent valve [XV7012G] through BMS after pressing Burnerstart push button.

• In any condition if gas pressure reaches to 400kPa (g) shut off valve PV 7012G will allow gasto vent out in atmosphere at safe location.

For Diesel Oil No.2

• FD fan damper has to be set to the burnerstartup position manually by operator (minimumopen position / about 20%) this will satisfy “AirFlow at light off valve” condition.

Section — C 49


• Diesel oil flow control valve [FV 7010A] have tobe set for close position. PRV [PV 7010B] tobe set at 15% open position.

• Operator has to open the battery limit manualisolation valve [1DF-001] manually. Fuel gaspressure in the header would be normalizedby the Pressure control valve [PV 7010B], apressure transmitter PT 7010B will generatehigh & low alarm in the event of pressurisation.Permissive will be available to open the Shutoff valves [XV 7010D] through BMS afterpressing Burner start push button.

2.3.1First Burner Lightup Sequence WithFuel Gas

Ignition conditions to be satisfied –

• Gas burner startup interlock satisfied

– Fuel gas MFT to open command,

– No flame inside the burner

– Block valve close start permissive

• Burner A no main flame failure

• Fuel gas burner ignition permissive

– Any one FD fan motor running– Fuel gas FCV at close position.

These ignition settings are valid for first burnerstartup; these conditions are bypassed by fuel gasany one burner ON.

• Fuel gas burner A ignition not started• Pilot gas pressure not low• Pilot gas pressure not high OR• Diesel oil burner A ON• Fuel gas MFT open feedback• Any fuel gas ignition sequence not started

On satisfying the above conditions, burner isready for fuel gas firing. Fuel gas ready for startindication is available in LBP.

There are two modes of fuel gas firing:

1. Only fuel gas firing2. Diesel oil to fuel gas changeover (Manual)

1. Following startup sequence shall occur whenonly gas firing is carried out Burner startupshall be initiated by operating fuel gas burnerstart P.B. from local burner panel (LBP).

Burner Windbox damper energies to open 20% which is burner start upposition. (For the first burner start, all burner windbox dampers should be fullopen following furnace purge, but at the end of the first burner start sequencethe non running burners windbox damper should be closed). If windbox20% open feedback is not received within 5 seconds start command will beremoved automatically.

Start :

Fuel gas header vent valve de-energise to open.

Ignitor energised ON.Start +Windbox20%open feedback

:

Burner ignition valves energised to open and vent valve energised to close.

Ignitor ON. Burner ignition pilot flame monitored for flame ON. If pilot flame isnot ON, start-up sequence will be stopped indicating flame failure signal.

Fuel gas header pressure monitor for normal pressure during first burner startcommand. Fuel gas pressure shall be less than 0.6 Kg/cm2g. If pressure isnormal fuel gas block valves of burner A energised to open and vent valveenergised to close.

Start + 5 sec. :

Fuel gas header vent valve energised to close.

Burner main flame monitored for flame ON. If flame is not sensed ON by anyof the two scanners burner will trip.

Burner ignition block valves de-energised to close and ignition vent valvede-energised to open after 10 sec.

Burner firing stabilised and burner running condition shall be indicated if mainflame is detected.

Windbox damper on non-running burner will close.

Start + 10 Sec. :

Windbox damper of the same burner will open to 100% after 60 secondsfrom start command.

Section — C 50


2. Following startup sequence shall occur duringdiesel oil to gas manual changeover.



Start + 10 Sec. :


Following indications concerning burner light up isavailable on LBP.

• Burner A pilot on• Burner A ready for start• Fuel gas Burner A ON

2.3.2First Burner Lightup Sequence WithDiesel Oil

• Diesel oil burner startup interlock satisfied

– Diesel oil MFT to open command,– No flame inside the burner– Block valve close start permissive

• Burner A no main flame failure• Diesel oil burner permissive• Scavenging permissive• Diesel oil firing interlock satisfied

• Diesel oil Burner A Ignition not started• Pilot gas pressure not low• Pilot gas pressure not high OR• Fuel gas Burner A ON• Diesel oil MFT open feedback• Any Diesel oil ignition sequence not started

On satisfying the above conditions, burner isready for Diesel oil firing. Diesel oil ready for startindication is available in LBP.

There are two modes of Diesel oil firing:

1. Only Diesel oil firing2. Fuel gas to diesel oil changeover (Auto)

1. Following startup sequence shall occur whenonly oil firing is carried out: Burner startupshall be initiated by operating diesel oil burnerstart P.B. from local burner panel (LBP).

Start : Burner Windbox damper energies to open 20% which is burner start upposition. (For the first burner start, all burner windbox dampers should be fullopen following furnace purge, but at the end of the first burner start sequencethe non running burners windbox damper should be closed). If windbox20% open feedback is not received within 5 seconds Start command will beremoved automatically.

Ignitor energised ON.Start +Windbox20%open feedback

:

Burner ignition valves energised to open and vent valve energised to close.

Ignitor ON. Burner Ignition pilot flame monitored for flameON. If pilot flame isnot ON, start-up sequence will be stopped indicating flame failure signal.

Start + 5 sec. :

Diesel oil block valves opens after 5 sec through digital output and 4 to 20mA. This signal is enerated in the PLC using a ramp generator and givento the valve.


Burner ignition block valves de-energised to close and igntion vent valvede-energised to open after 10 sec.


Windbox damper on non-running burner will close.

Start + 10 Sec. :

Windbox damper of the same burner will open to 100% after 60 seconds fromstart command.

Section — C 51


2. Following startup sequence shall occur in automode



Autochangeovercommand + 10Sec.

:


Following indications concerning burner light up isavailable on LBP.

• Burner A pilot on

• Burner A ready for start

• Diesel oil Burner A ON

Upon satisfaction of above interlocks, ’BurnerReady for Start’ will be indicated in local burnerpanel and on DCS.

Burner start command can be given by pressingthe start push button either from local burner panelor from DCS.

On issuing the Burner start command following willbe the sequence of actions:

• Igniter spark "ON" (For 5 Secs.)

• Burner Ignitor air solenoid valve will open

• Pilot burner upstream & downstream SOV willopen, vent valve SOV will close.

• Burner Pilot flame proven through ionization.

• Pilot gas shut off valves will open based onfeed back from Pilot detection.

• Flame "ON" indication at DCS and in LBP.

Igniter spark will be "ON" only for 5 seconds,pilot flame to get established and detected by theionization rod within this period. Failure of thepilot flame detection stops the sequence.

On successful establishment of pilot flame and ifthe flame is detected by flame scanner then thepilot gas shut off valves will be kept opened for apredetermined time for enabling the main flameto establish. On receiving the feedback signal’flame detected’ within 5 seconds of burner startcommand, a signal is given to open the Burnermain shut off valves. If the main flame is stabilizedand remain detected by the flame scanners evenafter 10 seconds from the opening of block valves,Burner "ON" indication will be available on DCSand LBP. Failure of flame detection after pilotwithdrawal will trip the burner and Burner flamefailure / Trip will be indicated in DCS / LBP.

2.3.3Boiler Pressurization and Loading

Once the burner is ON, Boiler will be pressurizedaccording to the pressurizing curve.

After establishing flame in burner, the operatortakes care of the following:

• Operator has to inspect the flame in the furnacethrough peepholes. Clear furnace with properflame is important.

• Monitor the steam drum water level.

• Monitor the parameters, which can cause aboiler trip as explained in BMS logic.

• Line up the phosphate dosing to steam drumat a slow rate.

• Operator has to be on alert for swelling of drumlevel when the boiler water temperature buildsup to 90 0 C. Open the IBD valve and regulatesuch that the water level is within limits. IBDValve is to be closed once the water level isnormalized.

• Modulate the firing / fuel flow so that the boilerpressurization is following the pressurizationcurve (attached later in this section). Firingrate has to be increased manually from DCSconsole. Positive air fuel ratio has to bemaintained during modulation. Start up vent/pressure control valve may have to be throttledin the process of pressurization to follow coldstart up pressurisation curve.

• At 2 bar (g) drum pressure, drum vent valveshave to be closed.

• At 2 bar (g) drum pressure, superheater drainvalves have to be closed.

• Once the swelling is over and the drum levelnormalizes, select the drum level controller intosingle element control and into auto mode withset point of 50%. Monitor that the drum level isbeing maintained.

• Operator shall have a walk down check offeedwater line, fuel gas line, the boiler and thevalves. Any water, steam leakage (through

Section — C 52


valve glands, bonnets, flanges) and otherminor abnormalities noted can be correctedwhen the boiler pressure is less than 5 bar (g).

• When the boiler is in service, the Operator hasto be alert to the alarms appearing on DCS.When an alarm registers, the Operator hasto check the cause for the alarm. Correctivesteps have to be taken wherever necessaryto restore normal values. Quick action bythe Operator prevents further deterioration ofvalues to the boiler trip level.

• Steam temperature controller TIC 7018-C shallbe put into auto mode in DCS console with theset point of 371 °C.

• At around 35 bar (g) of super heater outletpressure MSSV bypass valve can be openedto warm-up the main steam line to plant or toequalize the pressure across. The trap units inthe main steam piping to be lined up.

• When the main steam line pressure reachesabout 4150 kPa (g), MSSV (MOV 7018D) canbe opened to connect the boiler with plantmain. MSSV bypass pressure equalizationvalve (MOV 7018E) shall be closed.

• Once the steam flow indication is available andit is reached above 40% of MCR, drum level

control shall be changed over to 3-Elementcontrol mode.

• Now, Combustion control shall be taken intoauto mode (Boiler master pressure control).Combustion control will take care of the loaddemand, by modulating the fuel flow andairflow.

• Regulate the phosphate doing rate to steamdrum.

• Operator to adjust flow through SH steam,saturated steam and boiler water samplecoolers so that a small stream of cold samplesare obtained from them. Call for a laboratoryanalysis of the SH steam, boiler water andboiler feed water sample. Necessary water& steam parameters to be maintained byadjusting the phosphate chemical dosing rateand continuous blow down rate.

• Once the boiler is connected to the plantheader and the combustion controller is putinto auto mode, boiler will be responding to theload demands automatically. The control loopsshall be tuned up to take care even upto ramprate of 20% MCR per minute.

• Put Deaerator in service and start dosing LP& pH Dosing.

Section — C 53


COLD STARTUP PRESSURE RAISING CURVE

Boiler startup can be termed as cold startup whenthere is no pressure or when pressure is less than2-bar (g) in the steam drum.

In a cold start up, possibilities of some inspectionor maintenance work having been done is

presumed. A walk down check is required andthe boiler and its auxiliaries are to be preparedmeticulously for a start up from the DCS of thecontrol room. Before a walk down check ensurethat all work permits have been returned, safetytags are removed and maintenance permissionfor boiler start up is available.

Figure 1

3 Boiler Hot Startup PressureRaising Curve

Restarting a boiler immediately after a trip whenthe boiler is still hot and with steam pressure notless than around 32 kg/cm2 (g) is termed as HotStart-up. As the boiler was in service till the tripout, the required valve line up (as stated for thecold start up) will be available and can be quicklychecked by visual inspection. Hot restart requiresoperations to be done fast, within the maximumpermissible firing rates so as to obtain quickly therequired main steam pressure and temperatureconditions. Boiler can be pressurized to the ratedpressure and temperature by using start up ventvalve, and can be connected to plant mains afterachieving the rated parameters.

Following are the steps involved in the hotstart-up:

• Normalise the steam drum level by modulatingthe feed water flow control valve.

• Start the burner after achieving the necessaryBMS interlocks as explained earlier.

• As soon as the burner is started open the Startup vent valve.

• Once the flame is stabilised, increase the firingrate according to the rate of pressurisationspecified in the pressurisation curve.

• Maintain the drum level.• Once rated pressure and temperature isreached connect the boiler to the main headerand close the start up vent.

Section — C 54


Figure 2

4 Boiler Warm Startup PressureRaising Curve

Re-start of the boiler with steam pressure not lessthan 2-kg/cm2 (g) is termed as a warm start-up.

The preparations and valve line up required isas for HOT restart. However as the BOILERhas been idle for several hours, the valve line uprequires to be verified.

• Super heater drain operations

Opening of Main steam line drains, Superheaterdrains & Attemperator drains are required inwarm start up. These drain valve need to beclosed when condense is drained completely at 5Kg/cm2(g).

The time taken for a warm start may be more thanthat hot start but less than that of a cold start.Boiler can be pressurized to the rated pressureand temperature by using start up vent valve, andcan be connected to plant mains after achievingthe rated parameters.

Section — C 55


Figure 3

5 Boiler Shutdown

A Boiler shut down can be of two types:

• Planned shut down where the Operator getsadvance notice and adequate time to shutdown the boiler in an orderly manner, forinspection, maintenance or for cold reserve.

• Boiler Trip on interlock protection or emergencyshutdown by the Operator.

5.1 Planned Shut Down

On a planned shut down operator to carryout thefollowing activities in the sequence:

• Reduce the boiler load gradually. At steam flowbelow 12-15 TPH, stop the top burner fromDCS/ LBP.

• Close the MSSV. Take the combustion controlloop into manual mode.

• Then stop the burner manually from DCS/ LBP.

• Close the startup vent isolation valve. Ensurethat the pressure control valve is closed andselect the controller into manual mode.

• Carry out the furnace purge.• Stop the FD fan and close the suction damper.• Continue to feed water to the boiler to maintainnormal water level. Drum level controllershall be changed to single element modeand maintain the level. Once the level isnormalized, take the feed water / drum levelcontroller in to manual mode and close thevalve (output as 0 %).

• Stop phosphate dosing. Close the CBD valve.• Verify the IBD valve is closed.• Allow the boiler to cool naturally.• Scanner cooling air supply is continued till thefurnace temperature falls below 100 0 C or forat least 8 hours.

• If the proposed shut down of the boiler is formore than 8 hours, fuel gas supply has to beisolated.

Section — C 56


• When the steam drum pressure drops to 2 bar(g), open the steam drum vent and the startupvent.

6 Boiler Emergency Trip

Sometime boiler trips either by a protection ordue to a power failure or by an emergency tripcommand by the operator causing the fuel blockvalve to close and abruptly stopping the firing.

Under such emergency trip conditions theoperator action is -

• For protecting the boiler

• For investigating the cause of trip and ifpossible to eliminate the cause

• If the cause is eliminated, to restart the boiler

• If the cause cannot be immediately eliminatedto continue the shutdown till it is done

BOILER PROTECTION AFTER A TRIP

• Close main steam stop valve immediately

• Continue to feed the water if level requires tobe maintained

• Check that fuel Oil block valves are closed

• Check that there is no flame in the furnace

• Carry out post trip purge of the furnace

6.1 Boiler Shutdown During SuddenTube Failure

In case of a sudden tube failure followed by asevere loss of drum water level, it is advisedimmediately to stop the burners, purge thefurnace and also isolate the steam & feedwatersystem. This is to avoid undue thermal stresseson pressure parts. The drum vent & start up venthave to be opened as the pressure falls to 2 Bar(g). The extent of the damage is to be ascertainedafter cooling the boiler completely.

In case of a tube rupture, if the water levelcould be maintained and flame is not lost, it isrecommended that the boiler be taken out ofservice as soon as possible. The impingement ofsteam & water from a leaking tube on adjacenttubes can cause additional failure of tubes.In such cases, the normal planned shutdownprocedure is immediately implemented.

7 Boiler Operation

Walk Down Check List During Operation

Boiler

• Check for unusual noises. This may be fromsteam or water leakages

• Check for steam or water leaks from valves,connections and fittings

• Check for unusual traces of water on floor

• Check for air / flue leakage from windbox,boiler casing and ducting

• Walk around the furnace exterior and observefor any hot spots or gas leaks.

• Check position of fan suction damper andcheck for obstruction

• Check for passing from safety valves at normaloperating pressure. Check that the drain linesand drip pans are not plugged

• Check for clear & bright flame and clear stack

• Check to see that proper water level is beingshown by the direct water level gauge. Checkfor water or steam leak from ports or drainconnections, which will cause a false waterlevel in the gauge glass. Inspect the glass fordiscoloration or fouling

• Check for any obstruction for thermalexpansion

Rotary Equipments

• Listen for any unusual noises

• Feel and inspect for vibration regularly

• Inspect bearing temperature

• Inspect for lubrication level

• Check for any abnormality in couplings

• Check current and voltage of motors

7.1 Do’s and Don’ts for BoilerOperation

DO’S

• Maintain all instruments in good workingcondition

• All equipment interlocks should always be inline

• Maintain normal water level in steam drum

• Maintain water quality as per the recommendedlimits. A table showing the DM water & drumwater quality is included at the end of thissection

• FD damper must be in smooth operatingcondition

• Pressure raising from cold start must be doneas per the cold start up curve

Section — C 57


• All the duct joints must be leak proof

• Use proper lubricant and maintain the scheduleas recommended by the manufacturers

• Operate the boiler within the recommendedoperation limits

• Boiler, piping, ducts must be properly insulated

• Servicing of equipments should be done as perthe manufacturer’s schedule

• Maintain proper operation log sheets regularly

• Maintain the instrument air free from moistureand oily matters and the pressure asrecommended

• Carry out regular cleaning of direct water levelgauge glasses of Boiler drum

• Use proper valve gland packing to avoidleakage

• Use proper gaskets for flange joints

• Operate the blowdown valves as perrecommendation

• In case of power failure close the steam stopvalve

• If the water level goes up above the limitsoperate the intermittent blowdown valveimmediately and maintain the water level tonormal

• Maintain the feed water temperature atEconomiser inlet and flue gas temperature atEconomiser outlet as recommended

• Use genuine spares

• Boiler surroundings and equipments must beproperly illuminated

DON’TS

• Don’t bypass any instruments and safetyinterlocks

• Don’t use raw water as boiler feed water

• Don’t operate the boiler beyond the operationlimits

• Don’t leave the furnace door open while theboiler is in operation

• Don’t mix up different lubricants

• Don’t alter the equipment maintenanceschedule

• Don’t leave the instrument control panelunattended

• Don’t allow unauthorised persons to operatethe boiler and associated equipments.

• Do not dose chemicals into the boiler in batchwise, they should be done on a continuousbasis

• If boiler is running under combustion controlmanual mode, then while increasing loadair should be increased first followed byoil. Ensure always-proper air to fuel ratiocorresponding to load.

7.2 Boiler Log Sheet

It is suggested to record the boiler parametersduring start-up and normal operation. Observedabnormalities (if any) recorded can be usedfor analysis, troubleshooting and maintenancepurposes.

Log sheet to be filled once in every hour by theoperating staff.

Feed water, boiler water quality are also to benoted once in four hours.

Total Fuel consumption and steam production ofa day to be noted.

Logbook should furnish the details about

• Boiler trips with reasons and time.

• Boiler running hours.

• Boiler shut down details (forced or planned,outage hours, jobs carried out, etc.,)

Sample log sheet is enclosed.

7.2.1Log Sheet for the Boiler

Date:

Shift:

SL.No. PARAMETER TAG NO. UNIT TIME

1 Drum Level LT 7018A/B/C/D/E/F MMWC

2 Main Steam Pressure PT7018–B Kg/cm2 G

3 Steam Flow FT7018–C TPH

Section — C 58



4 Steam Flow Totalizer Tons

5 Gas Flow FT7012–A Kg/Hr

Oil Flow FT7010–A Kg/hr

Air Flow FT 7015 Kg/hr

Feed Water Pressure atControl Station Inlet

PT7018–A Kg/cm2 G

Feed Water Temp. at ECO.Inlet TI 7018–E DEG C

Feed Water Temp. at ECO.Outlet TI 7018–D DEG C

Flue Gas Temp. at FurnaceExhaust TI 733A0 DEG C

Flue Gas Temp. at ECO.Outlet TI 717A0 DEG C

FD Outlet Pressure PT 7150 MMWC

Windbox Pressure PT 7151 MMWC

Furnace Pressure PT7017BA/B/C MMWC

Flue Gas Draught at ECO.Inlet PT 733A0 MMWC

Flue Gas Draught at ECO.Outlet PT 717A0 MMWC

Flue Gas Oxygen AT 717A0 %

Feed Water Analysis

pH

Conductivity

TDS

Silica

Hardness

Oxygen

Drum Water Analysis:

pH

TDS Alkalinity as CaCo3

Silica

Phosphate as Po4

Sulphite as SO3

Sat. & Sh Steam Analysis:

pH

Conductivity

Section — C 59



TDS

Silica

8 Boiler Safety

8.1 Emergency Procedures

Low Water Level

Causes

1. Feedwater control system failure.

2. BFP failure

3. Tube leak

Action

Compare control room indication with gaugeglass level. If the water level falls out of sight dueto momentary failure of water supply system, dueto negligence of the operator, due to momentaryfluctuations that might occur with extraordinarychanges in load, appropriate action should betaken at once to trip the fuel. Any decision tocontinue to operate, even if only for a short timeat a reduced rating would have to be made bysomeone in authority who is thoroughly familiarwith the circumstances that led to the emergencyand positively certain that the water level can berestored immediately without damaging the boiler.

In the absence of such a decision

1. Stop the fuel feeders and Fans immediately.Shut off the main steam stop valve .

Simultaneously, if feedwater has becomeavailable and the operator is assured that nopressure part has been damaged

1. Take the feedwater control system intomanual mode

2. Allow the water flow to boiler gradually tonormal water level. (Do not hurry up whichmay lead to sudden quenching and tube leak)if pressure part damage is suspected

3. Reduce the steam pressure gradually

4. Open the drum air vent when the pressuredrops below 2 kg/cm²

5. Cool the boiler so as to examine the extent ofdamage

6. Drain the boiler after cooling

7. If any tube rupture and bulging is observedrectify the same

8. If any tube leakage were observed rectify /repair the leaking tubes and after the repairsconduct hydrotest

9. Determine the cause of low water

High Water Level

Causes

1. Feedwater control malfunction

2. Operator error

3. Instrument air supply failure

4. Foaming

Action

1. Take the drum level control loop into manualmode

2. Reduce the water level immediately byoperating the intermittent blow down tomaintain the drum level

3. Reduce the steam discharge rate, ifnecessary

4. Start the stand by compressor if required

Furnace Puffing & Back Firing

Causes

1. Uncontrolled feeding of fuel into the furnace

2. Sudden increase in FD fan air

3. Tube rupture

4. Foaming

Action

1. Take airflow control system into manual modeand maintain the furnace pressure

2. Never increase fuel / air flow suddenly.Always increase air first then fuel / oil / gaswhile taking boiler on load

3. In case of tube failure take the boiler out ofservice immediately

4. Keep the water wall tubes clean by monitoringthe combustion conditions.

Boiler Explosion

Causes

1. Accumulation of fuel in the furnace due toincomplete combustion

Section — C 60


2. Loss of ignition

3. Fuel oil valve leakages

4. Frequent unsuccessful startups

5. In-sufficient purging of furnace

With the mixture of unburned fuel with air inexplosive proportions and the application of heatsufficient enough to raise the temperature of themixture to ignition point.

Action

1. Trip the FD Fan immediately

2. Analyse the reasons for explosion and rectifythe system

3. Evacuate or clean the furnace to the possibleextend

Conditions for Boiler Restart after FurnaceExplosion

After a case of furnace/ boiler explosion, therestart of the boiler has to be carried out onlyafter a thorough and detailed investigation& understanding of the cause of explosion.Following necessary actions have to becompleted to prevent the repeat incidence ofexplosion and before restart of the boiler.

Find out the root cause for the explosion andrectify the same.

1. Inspect the furnace for any signs of bulging ordamage to the tubes.

2. Inspect the furnace refractory for damages

3. Inspect the air and flue ducts for any signs ofdamage

4. Inspect the expansion bellows in the air andflue ducts for damages

5. Inspect the economizer casing for damages

6. Assess the damage if any and rectify thesame.

7. Carry out the hydro test of the boiler. In theevent of a failure of the hydro test, identify thetubes that have failed and proceed to rectifythe same as explained in the maintenancesection.

8.2 Operational Precautions for Safety

Introduction

The handling and burning of any fuel is potentiallyhazardous. Some fuels ignite more readily thanothers. Safe handling and operation demands

knowledge of the characteristics of the fuel andcareful observance of necessary precautions.

1. Operating the boiler with low feed watertemperature along with high excess air willresult in exceeding metal temperature. Thereshould be no hesitation to bring down theload on the boiler if this temperature cannotbe brought under control by other means.

2. In the case of tube failure which can beidentified by hearing the noise in the boilergallery and cross checked by differencein steam and water flow, gas and steamtemperature, the boiler should be shut-downat the earliest by regular procedure formaintenance work. Otherwise large numberof tubes may fail due to steam erosion andimpingement.

3. Entry of wet steam into superheater andfirst row or after desuperheaters will resultin removal of oxide film due to thermalshock. Boiler salt in the steam will acceleratecorrosion. Austenitic steel is the worstaffected due to stress corrosion in this case.Hence temperature after the desuperheatershould be maintained well above thesaturation point in the case of direct spraytype.

4. Boiler washing (when the unit is shut down)can be done effectively by using hot water.Immediately after washing, the surfacesshould be dried.

5. Always use deaerated, de-mineralised waterfor boiler feeding with the recommended feedwater quality.

6. Feedwater temperature must also bemaintained at the highest level possibleeither with the help of feedwater heatersor heating the water in the feed tank. Lowfeedwater temperature obtained during lowload operation will result in external corrosionof economiser.

7. The economiser circulation system if providedshould be kept in service when there is fire inthe boiler with no feed flow.

8. Steaming in economiser is harmful toeconomiser unless otherwise it is designed assteaming type and hence steaming should beprevented by keeping a watch on economiseroutlet water temperature.

9. Carryover of salts in steam occur either due tomechanical or vapour carry over from steamdrum. Efficient drum internals can only reducemechanical carry over. Silica is always carried

Section — C 61


over in vaporous form. Continuousmonitoringof sodium and silica in steam is desirable.

10. Before operating a boiler, ensure completeknowledge of water chemistry.

11. Whenever boiler is started after a shutdown ofmore than 3 days, check all safety interlocksbefore boiler start up for proper functioning.

12. Superheater drain valve should be operatedas per recommendations.

13. The steam drum should normally be filled uptothe point when water is showing in the bottompart of the gauge glass. This is to allow for theswell on heating and to reduce any blowingdown resulting from this cause to a minimum.

14. Firing should be maintained having regard tothe instructions for protection of superheater,which will limit the maximum gas temperaturein the superheater zone.

15. Once the boiler is boxed up, the water levelin the steam drum must be raised to the verytop of the drum. Filling the drum like this willprevent excessive temperature differentialsalong the drum wall. The water is thenshut-off and the boiler is allowed to cool.

16. When staring from cold, the drains on both theinlet and outlet superheater boxes should bewide open (if applicable)

17. While raising pressure on boilers, a techniqueof continuous firing should be developed ifpossible, since intermittent firing may result inrecondensation in the tube loops.

18. Where spray type attemperator are fitted,it is very important that control of steam orsuperheater tube metal temperature is notattempted by the use of the spray duringpressure raising. This can lead to the entry ofspray water into the secondary superheatertube loops.

19. Ensure the availability of fuel / bed material /recycle ash in the bunkers.

20. Never allow oil or gas to accumulateanywhere, other than in a tank or lines whichform a part of a fuel supply system.

21. Purge the furnace completely beforeintroducing any light or spark. On a multipleburner unit, burners may be ignited without apurge if one or more in service already.

22. Have a lighted torch or spark producingdevice in operation before introducing anyfuel into furnace.

23. Maintain a positive airflow through theburners into the furnace and up the stack.

24. Maintain adequate oil pressure andtemperature for atomisation & also adequatesteam or air pressure in case of steam or airatomisers.

25. Ensure operation staff alerts to all abnormalconditions. To observe the above rules,automatic control instruction may include :-

a. Purge interlocks e.g. requiring a specifiedminimum airflow for a specific time periodsufficient to purge the setting before thefuel trip valve can be opened.

b. Flame Detector: Each burner shouldhave its own flame detector connected toan alarm and interlocked to shut-off thefuel to the burner, it serves upon flamefailure.

c. Closed position switches for burnershut-off valves, requiring that all shut-offvalves be closed to permit opening thefuel trip valve.

d. Shut-off of fuel on failure of draft fan (s).e. Shut-off of fuel in the event of low fuel

pressure and low atomising steam orair pressure, and low instrument airpressure.

f. Shut-off of fuel in gas fired units in eventof excessive fuel gas pressure.

g. Shut off of fuel in the event of electricpower failure.

26. The raising and lowering of steam parametersshould be restricted to the value given in thestarting diagram. Exceeding these values willresult in reduced fatigue life of pressure parts.

27. Entry of wet steam into superheater andfirst row or after de-superheaters will resultin removal of oxide film due to thermalshock. Boiler salt in the steam will acceleratecorrosion. Austenitic steel is the worstaffected due to stress corrosion in this case.Hence temperature after the de-superheatershould be maintained well above thesaturation point in the case of direct spraytype.

28. Carryover of salts in steam occur either dueto mechanical or vapour carryover from steamdrum. Efficient drum internals can only reducemechanical carry over. Silica is always carriedover in vaporous form. Continuousmonitoringof sodium and silica in steam is desirable.

29. Before operating a boiler, ensure completeknowledge of water chemistry.

30. The threaded portion of the burner tipshould be covered with a non-hardening

Section — C 62


high temperature lubricating compound.This facilitates easier subsequent removal.(Please refer burner manual)

31. Lapped burner tips must be kept in a plasticcontainer to prevent damage for atomisingsteam with internally mixing type steamatomisers.

32. Whenever boiler is started after a shutdown ofmore than 3 days, check all safety interlocksbefore boiler start up for proper functioning.

Proper Handling of Access Door

1. Never open an access door while the unit isoperating.

2. Any access door can have large amountof material built up behind it even after thebed has been drained. This material will fallout when the door is opened. Bed materialcan stay hot for many days even after boilershutdown.

3. Open the door slowly and always stand to theside of the opening.

4. Look at the cavities through the door beforeentering into the boiler. have sufficiently brightlight available at all times when personnel arein the furnace and or in convection pass.

Proper Handling of Thermocouples

1. Repair or changing of thermocouple /thermowells during boiler operation isabsolutely prohibited, particularly in thepositive pressure zone of the boiler. Howeverif the need arises, always recall that thefurnace is pressurised and that the thermowellmay be an open path to the pressurisedfurnace. slowly and carefully disconnect thethermocouple from the well

2. If you encounter resistance in removing thethermocouple, it is an indication that thethermowell has eroded and is packed withash and bed material. abort the attempt toreplace the thermocouple and refasten it untilthe boiler is off the line and cooled.

3. If no resistance is encountered then carefullyremove the faulty thermocouple and replaceit.

4. Never look into the thermowell opening.

Handling of Secondary Air Ports

1. The hand-operated dampers in the secondaryair nozzles will be very hot.

2. While handling the dampers / ports protectivegloves should be worn and enough attentionto be given.

Handling of Solid Piles

1. Always be cautious of piles of bed material.

2. The surface of piled material may be cool inthe surface while just below the surface stillmay be very hot.

3. Bed material in a pile can stay hot for severaldays.

Handling of Furnace Ports andObservation Doors

1. Ports and observation doors are open to thepositive pressure in the furnace.

2. Never stand directly in front of the ports.

3. Do not leave the poking rod in the furnace forlong. It will heat up quickly making the rod hotto handle and hazardous when it is removedfrom port.

4. Never look directly into the port or standdirectly in front of the open port. If thereis a pressure pulse in the furnace, hot bedmaterial can suddenly and unexpectedlyspurt out.

5. Never use anything that may burn or melt,such as plastic or rubber, to temporarily blowthe port.

6. Properly dispose of all combustible materialfrom the port area. If any hot material blowsout from the boiler it presents a potential firehazard.

7. Be sure aspirating air is on before you openthe port door. If the air is not on, a stream ofhot furnace gas, ash and bed media will blowout of the boiler. • Open the port cap slowly.

8. When inserting a probe in the port, stand asfar back as you can. Due to pressure somebed material can blow out.

9. When extracting the probe, again stand wellback.

10. Never leave the port unattended ever for shorttime while working.

Safety Precautions

1. Do not attempt to open the boiler doorsor observation ports without observing theproper safety procedure.

2. Always use a full-face mask with tinted glass.

Section — C 63


3. Do not stand directly in front of open ports ordoors especially when they are opened.

4. Use sealing air when opening the doors /observation ports.

5. Use ear protection devices, whenever it isnecessary.

6. Wear protective gloves when working aroundthe boiler.

7. Do not use open-ended pipes for rottingobservation doors or ports.

8. Never enter drums, ducts etc. until all thesteam and water valves including the drainand blow down values have been closed tocheck and tagged.

9. Do not enter a confined space until it has beencooled below 30 °C and property ventilated.

10. Completely drain the solids from the bed,hoppers etc. while entering.

11. Always use low voltage extension cords andlight bulbs with properly connected ground.

12. Never open or enter the rotating equipmentuntil it has come to a complete stop and circuitbroken i.e. open

13. When entries the furnace ducts etc. beprepared for falling.

14. Never step into fly ash or bed material. Itcan be cold on the surface yet remain hotand smoulder underneath for extended periodof time. Always secure the drive mechanismof dampers, gates and doors before passingthrough them.

15. Watch for hot water in drum and headerswhen removing manhole and manholecovers.

16. Never use toxic fluids like CTC in confinedspaces without adequate ventilation.

17. Never direct an air or water stream into anaccumulation of fly ash in a confined area. Ifthe fly ash is smouldering the asatation couldresult in an explosion.

Safety Tips

1. All scaffolding materials are removed andcleaned.

2. Check any observation for expansion anddampers operations.

3. Ensure that all inspection doors, access doorsand openings are closed and pad locked asrequired.

4. Disconnect and isolate the nitrogen purge if itwas used during the outage.

5. Open the steam drum vents and the vents.

9 Tube Failures

Operating the boiler with a known tube leak is notrecommended. Steam or water escaping froma small leak at pressure can cut other tubes byimpingement and set up a chain reaction of tubefailures. Large leaks can be dangerous. Theboiler water may be lost, the ignition may be lostand boiler casing can get damaged.

Small leaks can sometime be detected by the lossof water in the cycle or system. A loss of boilerwater chemicals or by the noise made by the leak.If a leak is suspected the boiler should be shutdown as soon as possible by following the normalshutdown procedure.

After the exact location of the leak or leaks islocated, the leaks may be repaired by replacingthe failed tube or by splicing in a new section oftube, conforming to relevant ASME code.

An investigation of the tube failure is veryimportant so that the condition causing the tubefailure can be eliminated and future failures canbe prevented. This investigation should includea careful visual inspection of the failed tube andin some cases a lab analysis. It is recommendedthat every effort be made to find the cause of tubefailures before operation is resumed.

10 Trouble Shooting Chart

The following chart is to be used for solvingproblems arising during operation.

Section — C 64


Indication Probable Source ProbableCause

Repair method &Preventive Measures

Unable to maintain boilerwater concentration

Tube Leak

Hideout

Slight leakagefrom pitting orcracking of tubeor tube seat leak.

Remove boiler fromservice at first convenienttime. Hydrostatic test to bedone to locate leak. Repairby welding or splicing asindicated and as approvedby insurance or StateInspection. Determinecause of failure and correctit.

Operation at normal loadsshould put chemical backin solution.

Sound of steam blowing infurnace or seeing visiblesteam from the stack.

Tube leak

Substantial leakfrom tube/tubes.Over-heatingas from scaleor tube seatleakage.

The same as above plustubes re-rolling.

Steam explosion infurnace followed byinability to maintain waterlevel.

Tube rupture

Failure of tubefrom low water,tube blockageor erosion ofexterior metalsurface.

Remove boiler from theline immediately. Inspector determine whether tubesplicing or wholesale tubereplacement is necessary.

High conductivitySolids carry over in thesteam or high CO2 orNH3 in boiler water

High boiler waterconcentrations,excessive waterlevel fluctuationdrum baffleleakage ordeposits onscrubbers

Check for baffle leaks insteam drum when out ofservice, or boiler watercontamination. Check ofdegasified steam samplewill indicate if CO2 or NH3is high

High gas temperature High excess airImproper control/adjustment ofairflow.

Check excess air atfurnace boiler outlet, andcorrect airflow if required

Excessive water levelfluctuation

Water load or controlconditions

High boilerconcentrations,extreme loadswings, varyingsupply pressureor control loopadjustment

Correct condition leadingto the problem

Section — C 65




Bowed water wallgenerating tubes Overheating

Internal depositor low water.Usually internaldeposits resultin tubes bowingaway from thefurnace & lowwater /starveresults bowingtoward thefurnace.

Severity of bowing willdetermine extent of tubereplacement. Internalscale will call for internalcleaning. If low wateris indicated a thoroughinspection for drumdamage and tube seatleakage must be made.Take steps to preventrecurrence or low watercondition

Tube blisters Localised overheating Internal deposit

Repair by re-tubing orwelding in tube sectionor by heating and drivingback blister dependingupon insurance carrier orState Inspector’s approval.Clean internally byturbining or acid cleaning.

Internal pitting sharpedged and covered withbarnacles in drum ortubes.

Corrosion Oxygen in Boilerwater

Depth and extent ofpitting determines needand extent of tubereplacement. Extensivedrum pitting can be weldedbut is subject to approvalby either the manufacturer& insurance carrier orState. Source of oxygenmust be located andeliminated

Internal loss of metalnot sharply defined andaccompanied by blackiron oxide (Fe 3 O4 )

Corrosion

Overheatingresulting inbreakdown ofwater into H& O2 Causeis usually fromsludge letdownor pluggage.

Individual inspectionwill determine extent orreplacement, internalcleaning and correctionof water conditions arerequired

External pitting Corrosion

From corrosiveash depositand moistureeither from dewpoint or externalsource suchas leaking sootblowing tube.

Extent of repair must bedetermined by individualinspection. In emergencytubes out of high heat zonecan be plugged, beingsure they are cut to ventand to prevent differentialexpansion with adjacenttubes.

Proper external cleaningcan prevent out of servicecorrosion.

Section — C 66




Locate and eliminatesource of moisture. If dewpoint is from in -servicecorrosion, take steps toraise metal temperature

Tube cracking

Mechanical stressor a combination ofstress corrosion or tubevariation.

Interferencewith expansionor differentialexpansion withadjacent parts togive mechanicalstress or thisstress pluscorrosion attack.Vibration setup by turbulentgas flowcharacteristicsover tubes.

When accessible andwith insurance or Stateapproval, the cracks canbe ground out and welded,otherwise splice in sectionor replace tube. Locate& eliminate source ofexpansion difficulty byinspection or hot to coldexpansion measurements.

Using tube spacers canstop vibration.

External metal loss.Highly polished area Erosion

Mechanicalabrasion fromsoot bloweraction.

Where accessible andwith insurance or Stateapproval pad weld orsplice in a tube section.Eliminate channeling ofsteam from soot blowersor use tube shields

External metal loss.Oxidized fire scale area. Overheating

Prolongedor repeatedoverheating.

Extent of metal losswill determine extentof tube or tube sectionreplacement. Inspection ora thermocouple installationwill determine cause ofoverheating

11 Water Quality Recommendations

Feedwater

Parameter Unit

pH at 25 Deg C 8.0 to 9.5

Total Iron as Fe < 0.05 ppm

Total Copper as Cu < 0.03 ppm

Dissolved Oxygen 0.007 ppm

Carbon Di Oxide -

Residual Hydrazine 0.02 ppm

Residual Phosphate / Permanganate -

Chlorides / Sulphates / Total Organic Carbon Nil

Oil & organics Nil

Section — C 67


Parameter Unit

Total suspended solids Nil

Total Dissolved solids 0.1 ppm

Total Hardness Commercial Zero

Conductivity at 25 deg C after cationic column 0.2 msiemens/cm

Total Silica 0.06 ppm

Drum Water

Parameter Unit

pH at 25 deg C 10.8 min - 11.2 max

Total Dissolved solids < 200 ppm

Silica as SiO2 5.5 ppm

Total Alkalinity as CaCO3 40 ppm

Residual Phosphate as PO4 20 – 40 ppm

Sodium Sulphite as SO3 18 – 30 ppm

Oil & Grease / Cu / Fe Nil

Free Chlorine / suspended Solids Nil

Steam

Parameter Unit

TDS <0.1 ppm

Silica < 0.02 ppm max

Note

The drum water quality should becontinuously monitored and suitableadjustment in blowdown to be made tomaintain the drum water as per aboverecommendations.

Note

2. Steam Quality is based on Feed waterquality.

Section — C 68


Section — D


♦ Section Overview♦ Recommended Maintenance Practices♦ Welding Procedure Specifications (WPS)♦ Boiler Preservation Procedure♦ Tube Failures♦ General Principal of Weld Repairs♦ Failure Reporting Format♦ Water Chemistry♦ Feed & Boiler Water Conditioning

1 Section Overview

This section describes the various maintenancepractices, overhauling, and preservationtechniques. Also discussed are failures andrepair techniques

2 Recommended MaintenancePractices

Systematic maintenance is essential to keepthe boiler and its auxiliaries in good conditionand to obtain reliable operation of the boiler withhigh availability and plant load factor. Effectivemaintenance aims at timely inspection of partsto repair or replace defective components and toprevent their failure when the boiler is in service.

Maintenance can be classified as -

• Preventive maintenance – mostly conditionbased

• Annual Boiler overhauls to clean andinspect pressure parts. The shutdown periodof the overhaul is also utilized to attend tosystems and parts which cannot be attendedduring short shutdowns or when the boiler is inoperation

The vendor manuals of the fans, motors, controlvalves with their positioners and actuators,instruments and controls, power cylindersetc., prescribe certain minimum maintenancerequirements which are to be carried out in oneof the above two maintenance categories.

2.1 Preventive Maintenance

The objective of the preventive maintenanceprogram is to obtain trouble free service from thecomponent till the next maintenance.

Vendor manuals for various equipments suggestinspection periods, checks to be done andrecommended spares. The true objective of themaintenance program can only be realized, if amaster plan of maintenance of all the componentsis prepared as per vendor instructions.

Full benefits of maintenance can be obtained onlyif proper parts are used. Mandatory spare partlist covers most of the spares required. It may befound that in the first two years of operation dueto variations of site conditions, some additionalspares not included are also required. Action hasto be initiated to procure such spares.

Some equipment have 100% reserve standbyunits. (Feedwater pumps etc.). Maintenance ofsuch equipments can be organized even whenthe boiler is in service, although some minimumrisk is involved. Equipment such as igniters,scanners have replacement spares which can beutilized when the working equipment are to bemaintained without affecting the boiler operation.The prepared master plan for maintenance shouldbe periodically reviewed during the first threeyears of the boiler operation.

It may be found that due to varying site conditions,the frequencies and quantum of work scheduledas per vendor manuals are either too much or tooless. Based on site experience, the frequenciesand work schedules can be modified. Ascientific method of preparation of the preventivemaintenance schedules is to make them conditionbased. In condition based maintenance, theequipment and components of the plant areinspected daily, weekly monthly etc., as pera suggested schedule by the local operatorsand deteriorating conditions if any observed arereported. Suggested inspection program is givenin this section. Based on operator reports of suchinspection, maintenance works are planned forthe next available planned shut down. Mandatoryinspections prescribed by the vendors are alsotaken care of, irrespective of the equipmentcondition.

2.2 Schedule of Inspections forCondition Based Maintenance

The schedule of daily, weekly and monthlyinspections given in the following pages do notrequire a boiler shutdown and in fact can onlybe done when the boiler is in service. Threeand six monthly inspections are done utilizing anavailable planned shutdown approximately in thespecified time period.

Section — D 69


Objective of these inspections is to ensurethat

• The components are in trouble free condition• To carry out any minor repairs or adjustmentswhich can be done with the boiler in service

• To plan for repair of such items, which cannotbe attended when the boiler is in service,during the next available shutdown

• To collect a database to determine optimumservice life of the systems and componentsbefore maintenance is required

The schedule can be expanded, curtailed ormodified based on experience in the first twoyears of operation.

Daily Checks

To be done once a day by the local operator duringhis walkdown checks. Such walkdown checksare to be encouraged to be done in each shiftby the operators. Only those operational checksthat require maintenance work for correction havebeen included.

EQUIPMENT CHECK WORK TO BE DONE

1. Local level gauge on steam drum • Check illumination is proper.

• Leaking valve glands.

• Leaking ports.

• Blurred level.

• Replace fused bulbs

• Isolate level gauges andtighten leaking glands

• Replace leaking ports

• Steam wash mica assuggested by vendor (Notto be done too frequently)

2. Comparison of levels indicated bylocal level gauge with that of remotelevel indicators in the control room

Compare the levels afterverifying there are no leaksfrom valves, glands etc., ofthe level gauge and indicators.Report discrepancies.

If there are seriousdiscrepancies, calibrationof the remote levelindicators has to be plannedimmediately.

3. Traces of water on boiler claddingetc.

Such spots are indicative ofvalve leaks, Instrument tappingleaks, boiler tube leaks etc.,Trace the source of leak.

Maintenance to be plannedto eliminate the sourceeither immediately orduring next planned shutdown (depending on thesource and quantity ofleak and accessibility formaintenance)

4. Fans & drive motors. • Check bearing temperatures

• Check for vibration levels.

If higher than normalbearing temperaturesare noticed check forcause-proper oil level / oilcirculation, correct gradeand quality of oil, abnormalsound or vibration. Ifbearing temperatures arevery high, start the reserveequipment (if avl.) and planfor a maintenance check.

Section — D 70



5. Drum safety valves. Check for passing of safetyvalves (noise or wisp of steamthrough silencer)

• Hand pop the affectedsafety valve one or twotimes to clear any dirtsticking to the valveseats.

• Lightly tap on the stem ofthe safety valves.

• If these measures donot succeed, requestfor check of the safetyvalve during next plannedshutdown.

6. Purity of Instrument air • Check by visual observationthat the instrument air is oiland moisture free

• If there is a feel by visualinspection, Oil and moisturecontent can also be checkedby laboratory examination asper standards

• Oil and moisture in theinstrument air is likelyto clog the positionersof pneumatic controllers/ solenoids and maketheir operation sluggishor unreliable.

• Open drain valves ofair-receivers for shorttime to drain condensateif any.

• If these measures arenot successful, inform theMaintenance Group

7. Scanner cooling fansuction-damper linkages andpower cylinders.

Check for their proper operation Sluggish operation offan suction dampermay be due to stucklinkage, stuck damper,faulty power cylinder,and faulty positioners.Check for possible cause.Maintenance works have tobe planned.

8. Steam or water leakages fromvalves and from flange joints

• Loose valve gland

• Loosened bolts of flange jointand / or failed gasket

• Tighten the gland nuts.If the leakage notgetting arrested, planfor maintenance duringshut down.

• Tighten the bolts. If thegasket failed then plan forthe maintenance duringshut down.

9. Boiler cladding, air duct or fluegas duct

Check for hot spots Hot spots may be due toleakage of flue gas or hotair. Source of leakage hasto be located after selectiveremoval of insulation (tobe planned for the nextplanned shut down)

Section — D 71


Monthly Checks


1. Fans and blowers.

With a vibration analyzerrecord vibration and measurebearing temperature. Also notethe operating condition of theequipment at the time of theabove observations and recordthem.

By monthly recording ofdata, establish a databasefor deciding the overhaultime of the equipment. Anoverhaul once in two or threeyears may be adequate.Such a database will helpin deciding the time frame.Sharp increase in vibrationlevels bearing temperaturesor sound levels may callfor early scheduling ofoverhauls

Section — D 72


Checks Every Six Months During a planned shut down of the boiler, thefollowing checks can be done.


1. Boiler Pre-interlock, purgeinterlocks, start permissive, boilertrip protection.

Coinciding with a plannedshut down of boiler, carryout the checks to identifymalfunctioning or sluggishpressure, temperatureswitches, solenoid operatedvalves, positioners, proximityswitches, actuators etc.,

Plan for maintenance orre-calibration of defectiveitems if any noticed, duringthe shut down period.

2. Burner refractory work. Visual check that there are noloose bricks, spalling or cracks

If any abnormalities are seenrepair works to be plannedduring next available shutdown

3. UV Scanner components

Clean UV Scanner cell andcheck its output as per vendormanual. Check its amplifierand flame relay

Replace scanner cells ifoutput is suspect. Adjustamplifier flame relay ifrequired.

Checks Every Year (Refer also work listed under Boiler overhaul)


1. Pressure temperature, Flow level,differential pressure controllers

Utilizing the boiler annual shutdown for overhaul, recalibrateall pressure, temperature, flow,level and d/p controllers as pervendor manuals

Carry out any maintenancereplacement or adjustmentneeded to secure initialcalibration values as percommissioning records

2. Pressure gauges, temperaturegauges, Pressure/temperatureSwitches

Recalibrate, Verify functioningof pressure/temperatureswitches as per design

Repairs or adjustments asnecessary

3. Positioners, actuators

Verify functioning of positionersand actuators by feedingcurrent inputs to positionersand measuring the air pressureoutput of the positioners andopening closing of actuators

Repairs or adjustmentsas necessary as pervendor manuals to obtainperformance as percommissioning records.Verify functioning ofproximity switches whereprovided. Clean filtersof air regulators. Checkfunctioning of air regulators.Verify tightness of airconnections

Section — D 73


2.3 Boiler Annual Maintenance andOverhaul

In addition to the check and inspections listedunder preventive maintenance, the boiler requiresan annual shut down of about 10 to 15 daysfor cleaning, inspection ad overhaul of boilerpressure parts. The shut down period is restrictedto a minimum by deploying adequate resources.If required, Field Engineering department of TBWcan assist the customer in carrying out the boileroverhaul.

The annual shutdown is utilized for cleaning andinspection of the pressure parts and to collectdata on the wear pattern of boiler, superheaterand economizer pressure parts. The shutdownopportunity is also utilized for overhaul of safetyvalves, regulating and isolating valves andcomponents, which can not be attended when theboiler is in service. (The valve overhauls neednot be done every year).

Annual Overhaul

Planning Before Overhaul

• Prepare a list of jobs to be done during theoverhaul based on earlier inspection reportsand the jobs listed below.

• Ensure availability of spares required for theproposed jobs.

• Ensure tools, tackles, scaffolding materialsrequired for the job.

• Ensure availability of manpower required forthe job (Own sources, contract labor etc.)Services of TBW are also available for carryingout annual overhauls and inspections.

Shutdown and Cooling the Boiler

Shutdown the boiler in a planned manner. Coolthe boiler. Open all access and inspection doors.Refer to the Section B of this volume for theshutdown procedures.

Inspection after Cooling

Carry out a preliminary inspection after cooling tocheck cleanliness and any sign of deposition onwater wall panels and the need for water wash.

Drums Inspection

• Open the access doors at either end of thedrums

• Allow the drum to ventilate for about 8 hours.If necessary two fan coolers can be fitted overtemporary stands to force air through the drum

• From the time the drum manholes are openedtill they are closed after inspection, the areaaround the drum must be cordoned to restrictentry only to specifically authorized personnel

• The names of persons who are entering thedrum for inspection, along with tools they carrymust be entered in a register. Persons comingout of the drum after inspection should beasked to account for the material they carriedinto the drum. This precaution is to preventaccidental dropping of foreign material throughthe water wall tubes, which may block watercirculation through them and can cause tubefailures

• Carry out a preliminary inspection of the drumto check for any deposits on the waterside ofthe drum

• Using nylon brushes, the deposits (which arenormally soft) are cleaned, collected on traysand disposed off outside the drum. Washingdown the deposits to the boiler tubes is notrecommended

• In case of excessive deposits, the chemist isasked to analyze the nature of the deposits. Areview of phosphate concentrations and boilerwater quality control, (high conductivity) maybe made to reduce the deposits in the nextyear of operation.

• After cleaning the following examinations aremade

– Examine the boiler drum metal for scale,pitting, corrosion and metal wastage. (Drumthickness is measured at a few selected spotsusing ultrasonic instruments and comparedto design thickness)

– Inspect fastenings of the baffles anddemisters to see that they are intact, withoutcorrosion pitting or holes. Eroded or corrodeddrum internals to be attended. No weldinghowever is permitted on the drum metal.The demisters can be examined in position.They need not to be dismantled. Reasonablewater tightness of the baffles is to be ensured

– Examine that feedwater pipe is intact withflange connections tight and discharge exitcorrectly oriented

– Examine that the continuous blowdown anddosing pipes are not plugged or corroded,their supports are normal, and their holeshave been correctly oriented

After the inspection, clean the manhole seatsand provide new gaskets. After the inspection

Section — D 74


and verifying that all men and material have beenremoved from the drum, close the manholes andbolt them tight.

Inspections in the Furnace

Check the water wall tube panels in thefurnace for

• Evidence of pitting / erosion / corrosion on tubeouter surfaces (exposed to the flue gas path)

• Evidence of overheating (bulging of tubes,blue color of tubes, blisters, disturbed verticalalignment of panels)

• On suspicion of any abnormalities consult TBWor a metallurgist for advice.

• Check the duct burner & accessories as pervendor manual & its setting.

• Any loose material inside the furnace needsto be cleared.

• The scaffolding inside the furnace shouldbe removed after such inspection (if any)and manhole door to be closed tightly afterensuring that the refractory blocks is placed inthe manhole.

Safety Valves, Start UP Vent Valves andOther Isolating Valves

These valves require regular overhauls, normallyonce in three years even if condition reports do notindicate any abnormality. Earlier overhauls can bescheduled if condition reports warrant. Overhaulsof the valves can be staggered after the first twoyears of operation in amanner that certain numberof valves are overhauled every year. Overhaulsof the valves are as per their vendor manualsenclosed.

Expansion Joints

Examine the expansion joints. Eroded / corrodedparts can be patched by welding. When severeerosion is noticed (after several years of service)the expansion joints are to be replaced. Collapseor stretching of the expansion joints is usuallydue to forces exerted by the connecting ducts.Readjustment of duct supports will solve theproblem and will assist the expansion joints toregain their original dimensions.

Insulation and Cladding

Verify insulation as per drawings and correctwherever necessary. Inspect cladding for

damages due pitting, hotspots, dislocation etc.Repaired as necessary.

Other Equipment

Overhaul of seal air fans, control valves, actuatorsetc., is scheduled as per vendor instructions andcondition monitoring described under preventivemaintenance

Light UP of the Boiler After Maintenanceand Overhaul

The pressure-raising rate during the first lightup after the overhaul should be slower thanusual giving time for check of equipment andcomponents. Valve flange joints and glandsmust be checked for absence of leaks andcan be re-tightened where necessary when theboiler pressure is less than 5 Kg/cm2. Burnerperformance has to be verified and its axialposition corrected if required. If overhauled,performance of the safety valves must be verifiedby floating them. The boiler expansions must beverified during pressure raising. A boiler overhaulis considered successful if it enables anothertwelve months of trouble free boiler operation.

2.4 Tube Thickness Survey

To make a quantitative assessment of wastage oftubes (both internal and external) a tube thicknesssurvey using ultrasonic tube thickness gaugesis recommended. For a useful tube thicknesssurvey program measurement location on waterwall, super heaters and economizers’ tubesmust be specified and indicated on a drawing.Vulnerable locations are usually chosen. Onrequest, the Field Engineering Department ofTBW can establish such a program. The followingare the suggested areas for a tube thicknesssurvey -

• Boiler bank, economizer coils, deaerator paneltubes & MUWH..

Tube thickness measurements at the selectedlocations are made and recorded after waterwashing and drying, during the first annualoverhaul. The base value is the design thicknessof the tubes. Subsequent measurements aremade at the same locations, every alternate year.The tube thickness survey provides useful dataon corrosion / erosion rates and can alert theowner when serious loss of thickness is noticed.

Section — D 75


3 Welding ProcedureSpecifications (WPS)

The pressure part of the boiler is made of severaltypes of steel of varying thickness. Welding isthe basic technique used in the fabrication of theboiler. The joints produced by welding shouldhave strength not less than that of the parentmetal. In the weld joint, the parent metals shouldfuse together, without cracks, blowholes, slaginclusions or defects of any kind. The weld jointapart from proving its mechanical strength intension must also be able to resist bending withoutcracking. Such requirements can only be met ifthe welding process used is strictly controlled.

ASME (and other organizations) classify materialsinto categories (P1 P2, P3, ... P9) as per carboncontent and alloying metals (chromium, Nickel,Molybdenum etc.) and specify the procedureto be used for welding materials of the samecategory or one category with another category.A specification of the materials and shapesadopted by TBW can be obtained on request.The welding procedure distinguishes betweenwelding of thin and thick material. The weldingprocess specification defines the following foreach category of welding.

• Edge preparation (angle, shape)

• Joint preparation (cleaning, gap) and tagging

• Joint pre-inspection before welding

• Pre-heat of the weld joint, if any required(method of pre-heating, temperature method ofchecking temperature)

• Root weld (gas welding, TIG or Arc, size ofelectrode, type of electrode)

• Radiographic inspection of root weld if required

• Subsequent runs of welding (TIG, Arc or othermethods, size of electrode, type of electrode,number of runs)

• Post weld heat treatment if any required(temperature, rate of increase of temperature,method of increasing temperature, holdingtime, rate of cooling)

• Radio graphic examination of the weld joint,indicating defects if any to be corrected

• Correction of weld defects

• Final acceptance of the weld joint

The WPS indicates compatible categories ofmaterials that can be welded. The WPS also laysdown the type of electrode to be used for each

category of welding. As the electrode depositsmaterials, the composition of the electrode mustbe compatible with the material welded and addstrength. The coating of the electrode also mustmeet specific requirements.

TheWPSmust be used not only during fabricationof the boiler, but also when any repair ormaintenance works are to be done. TBW hasWPS to cover every welding job connectedwith fabrication of the boiler in the factory anderection of the boiler at site, conforming to IBRrequirements. The Field Engineering Departmentof TBW will be glad to provide a WPS for any siterepair weld jobs required for maintenance.

4 Boiler Preservation Procedure

Introduction

Both the gas and waterside of a boiler should beprotected against corrosion during out of serviceperiods. It is known that many of the corrosionproblems of boiler and auxiliary equipment havetheir inception during storage. Rusting of tubesurfaces, as indicated by the formation of the redhematite (Fe2O3), not only cause a roughenedtube surface but also results in attack of parentmetal.

The advantages of efficient feedwater and boilerwater treatment during operation may be lost ifthe same diligence is not applied to protect heat.Transfer surfaces during idle periods. Protectionfrom corrosion during storage becomes vitallyimportant considering the number of times duringthe life of a boiler when it and its auxiliaryequipment are idle.

To minimize the possibility of corrosion, boiler tobe placed into storage must be carefully preparedfor the idle period and closely watched duringthe outage. There are two methods availablefor storing the unit dry storage and wet storage.Although the wet storage procedures is preferredsuch factors as availability of good quality water,ambient weather conditions, length of storageperiod, auxiliary supply of heat, etc may dictatethat the dry storage procedure is more practical.

4.1 Definitions of Water Quality

Some cleaning procedures, hydrostatic testingand storage require water of higher qualitythan others. For the purpose of economy andconvenience the lowest water quality consistentwith requirements is specified in these variousprocedures. The terms that identify the different

Section — D 76


water qualities along with their definitions are listbelow: Station service water - Water normallyused for drinking, fire protection, etc.

Softened water - Filtered, sodium zeolite softenedwater with total hardness less than 1 ppm.

Two- bed demineralised water - Water thenhas been passed through cation and anion ionexchanges in series.

Mixed bed demineralised water - Water that hasbeen passed through a mixed bed demineraliser.Water from an evaporator is considered to be ofequal quality.

Treated demineralised water - Mixed beddemineralised water that has 200 ppm ofhydrazine and enough ammonia added to givefinal concentration of 10 ppm (or a pH of 10.0).In this procedure, condensate is considered to betreated demineralised water.

4.2 Dry Storage Preservation

When it is known that a boiler is to be idle fora considerable length of time and that a briefperiod will be allowed for preparation to return it toservice, the dry storage method is recommended.In this method the unit is emptied, thoroughlycleaned internally and externally dried, and thenclosed up tight to exclude both moisture andair. Trays of lime, silica gel, or other moistureabsorbent may be placed in the drums to draw offthe moisture in the air trapped by the closing upof the boiler.

The following general procedure isrecommended when placing a unit into drystorage:

1. Fire the boiler according to the normalstart-up procedure and establish upto3.5-kg/cm2G-drum pressure. Stop firing.Secure the boiler and when the pressuredecays to 1.3 kg/cm2G, immediately drainthe boiler and headers under air. As soonas possible, open the drums to allow air tocirculate for drying of all internal surfaces.This step is included for a unit that has beenin service and is to be placed into storage.For a unit that has never been in service, startwith Step 2.

2. If the unit is full of water and cold, drain theunit under air. All non-drainable boiler tubesshould be blown with compressed air. If anexternal source of heat is available such asa steam coil air heater, portable heaters, etc.,

operate these heaters to assist in drying theinternal boiler surfaces.

Install trays (of non-porous constructionand capable of passing through the drummanhole) containing the moisture absorbent(silica gel is preferred) into the drums. Insertthe trays into the drum being certain thatnone of the absorbent comes into contactwith the metal surface of the drum. Toinsure against an overflow of corrosive liquidafter the moisture has been absorbed, thetrays should not be more than ½ full of dryabsorbent. The amount of absorbent canvary but the recommended minimum is oneKg of absorbent per 1000 Kg per hour steamflow capacity of the unit.

3. Open the isolation valve for nitrogenconnection, on the steam drum, close allother vents and drains and pressurize theboiler to 0.3 to 0.6 kg/cm2G with nitrogen.The amount of nitrogen required will varyaccording to the volume of the unit.

4. With the boiler pressurized, alternately openall boiler drains to purge air from the unit untilpressure decays to zero. It may be necessaryto repeat this process several times to reducethe amount of oxygen left in the unit to aminimum.

The unit should now be stored under 0.3 to0.6-kg/cm2G nitrogen pressure maintainedat the steam drum. To maintain the nitrogenpressure, all connections and valves shouldbe blanked or tightly closed. Check gaspressure daily to ensure protection. We wouldrecommend that periodic inspection of theunit be performed every 3 months to assurethat no corrosive action is taking place andto replenish the absorbent as required. Sinceair will enter the unit during this inspection,it will be necessary to repeat Steps 3 & 4 toexpel the air.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum. Before entering drumstest to prove that the oxygen concentrationis at least 19.5 %. The above procedure isintended to include the economizer.

Section — D 77


4.3 Wet Storage

The advantage of employing the wet storageprocedure is that the unit is stored completelywet with the recommended levels of chemicalsto eliminate a wet-dry interface where possiblecorrosion can occur. It is suggested that volatilechemicals be used to avoid increasing the levelof dissolved solids in the water to be used forstorage.

In preparing a unit for wet storage, the followingprocedure is recommended.

The unit should be filled with deaerated,Demineralised water treated with 200 ppmhydrazine (N2H4) for oxygen removal andsufficient ammonia (NH3) in order to attain a pHof 10 (for demineralised water, this will requireapproximately 10 ppm ammonia).

We strongly recommend pre-mixing of thechemicals with the water to insure a uniformmixture entering the boiler. This can beaccomplished by the blend-fill method. Theblend-fill method consists of blending thechemicals with the demineralised water at acontinuous rate such that a uniform mixtureis entering the boiler. Simply introducing thechemicals through the drum after establishingwater level will not insure adequate dispersion ofchemicals to all internal surfaces, unless sufficientheat is delivered to the furnace (i.e. firing theboiler) to induce natural circulation throughout theboiler.

Fill the unit with the treated demineralised waterto the normal centerline of the steam drum. Stopfilling further.

Back-fill the with treated Demineralised water untila rise in steam drum level is noted. Continue fillinguntil water exits from the steam drum vents. Afterfilling, all connections should be blanked or tightlyclosed.

A source of low-pressure nitrogen should beconnected at the steam drum to maintain 0.3 to0.6 Bar G to prevent air from entering the unitduring the storage period.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum.Before entering drums test to prove that theoxygen concentration is at least 19.5%.

If storage continues into winter, ambienttemperatures below the freezing point of watercreate a real hazard to the boiler pressure partsand it will be necessary to provide a means ofkeeping the unit warm to avoid damage.

At some later date when the unit is to be placedinto service, the boiler can be drained to normalstart-up water level and placed into operation.

In some cases, an expansion tank or surge tank(such as a 55-gallon drum) above the steamdrum elevation may be required to accommodatevolume changes due to temperature changes.This tank is equipped with a tight cover and sightglass and contains properly treated water. Thetank should be connected to an available opening,such as a vent line at the top of the steam drumin order to create a hydrostatic head. This tankwill provide a ready, visual check of water level orin leakage during lay up.

A source of low-pressure nitrogen should beconnected to the surge tank to maintain 0.3 to 0.6Bar G to prevent air from entering the unit duringthe storage period.

The treated demineralised water should beanalyzed weekly, and when necessary, sufficientchemicals should be added through thechemical feed line, to establish the proper levelsrecommended. Samples of the treated water canbe taken at the continuous blowdown line or anysuitable drain connection.

No unit should be stored wet when there is anypossibility of a temperature drop to the freezingpoint unless sufficient heat can be provided to theunit to eliminate the danger of water freezing andsubsequent damage to pressure parts.

Section — D 78


4.4 Nitrogen Blanket

Nitrogen can be introduced at the followinglocations

1. Through the steam drum2. Through the main steam line

The nitrogen required to seal the drainablecomponents may be supplied from a permanentnitrogen system or portable tanks located nearthe vent elevations. Due to differences in plantlayout, the owner should choose his own methodof piping the nitrogen, either from their permanentsystem or from portable tanks, to the vent (ordrain) locations listed.

The unit should be properly tagged and theappropriate warning signs attached notingthat the boiler is stored under nitrogenpressure and that complete exhaustion ofthe nitrogen must occur before anyoneenters the drum.Before entering drums test to prove that theoxygen concentration is at least 19.5 %

Section — D 79


4.5 Boiler Lay UP Procedures

TYPE OF SHUTDOWN PROCEDURE

SHORT OUTAGES 4 DAYS OR LESS. UNITNOT DRAINED

Maintain the same hydrazine and ammoniaconcentration as present during normaloperation. Establish 0.3 to 0.6 kg/cm2G nitrogencap on the steam drum

SHORT OUTAGES 4 DAYS OR LESS. UNIT ISDRAINED

Drain and open only those sections requirerepair. Isolate remainder of the unit under 0.3to 0.6 BarG nitrogen pressure where possible.Maintain the same nitrogen and ammoniaconcentration for water remaining in the cycle

LONG OUTAGES LONGER THAN 4 DAYSUPTO 15 DAYS. UNIT IS DRAINED

Fill the boiler with Polish water having 200 ppmof hydrazine and 10 ppm of ammonia to maintainpH 10. Establish nitrogen cap of 0.3 to 0.6kg/cm2G over the steam drum.

LONG OUTAGES MORE THAN 15 DAYS - UNITIS DRAINED.

Dry storage of boiler with nitrogen alone ispreferred procedure. Nitrogen cap of 0.3 to 0.6kg/cm2G to be maintained on the steam drum.Installed silica gel tray in the steam drum to soakmoisture if any present in the drum atmosphere.

4.6 Preservation of RotatingEquipments

1. Put the rotating equipment in service once inevery 48 hours or atleast once in a week

2. If the equipment is going to be under longshutdown

a. Fill bearing block full of oil to preserve thebearing and rotate the Fan/Pump Shaft by90o once in every 48 hours

b. Cover the bearing block & uncoveredportion of shaft with plastic sheets toprevent dust/water ingress

c. Ensure no dust/water accumulates on therotating equipment

4.7 Preservation of Instruments

1. Cover all field instruments with plastic sheets

2. Power up the panel instruments and check theoperation

3. Keep the control room dust and moisture free

4. Operate control valves, power cylinders oncea week and check operation.

5. Operate quick shutoff valves frequently(Twice a week)

6. Ensure that O2 analyzer is powered up andreference air supply is given when flue gas ispresent.

7. Check operation of Ignition Transformer oncein 2 weeks

8. Check operation of Flame Scanners & FlameAmplifiers once in 2 weeks

Section — D 80


5 Tube Failures

Operating a boiler with a known tube leak is notrecommended. Steam or water escaping from asmall leak can cut other tubes by impingementand set up a chain reaction of tube failures. Largeleaks can be dangerous. The boiler water may belost, the ignition may be lost, and the boiler casingmay be damaged.

Small leaks can some times be detected by theloss of water in the cycle or system, a loss in boilerwater chemicals or by the noise made by the leak.If a leak is suspected the boiler should be shutdown as soon as possible by following normal shutdown procedures (If situation permits).

After the exact locations of the leak or leaks areidentified, the leaks may be repaired by replacingthe failed tube or by splicing in a new section oftube as per relevant codes.

An investigation of tube failure is veryimportant so that the condition causingthe tube failure can be eliminated andfuture failures can be prevented. Thisinvestigation should include a carefulvisual inspection of the failed tube and insome cases a laboratory analysis.

1. It is recommended that every effort be madeto find the cause of tube failures beforeoperation is resumed.

2. It should be ensured that, whenever a spoolpiece is inserted in the failed zone, the weldjoint needs to be of proper weld quality.

3. Free from excess weld penetration to avoidany obstruction in the water / steam mixtureflow inside the tube. Excess weld penetrationcan cause internal tube erosion and results intube failures.

4. It is suggested to have all the joints arex-rayed and interpreted by qualified /experienced radiographer.

5.1 Tube Failure Investigation /Analysis Method

Investigation / analysis methodology is listed asfollows, which needs to be followed to find theactual root cause of the problems.

PLEASE FILLUP THE ENCLOSED (end of thissub-section) OBSERVATION FORM AND THE

SAME MAY BE SENT TO TBW ALONG WITHTUBE SAMPLE FOR ANALYSIS.

Objectives of Failure Investigation

Boiler tube failures are the largest cause of forcedoutages experienced by a utility. To avoid orminimize outages and the associated economicpenalties, it is important to identify the mechanismand root cause of tube failures. Informed visualinspection is often adequate for this purpose,however failure analysis involving detailedmetallurgical investigation is necessary. Tubefailures may be due to overheating, corrosion,erosion, fatigue, hydrogen damage etc. A failureinvestigation and subsequent analysis shoulddetermine the primary cause of a failure, andbased on determination, corrective action shouldbe initiated that will prevent similar failures.

Stages of Failure Analysis

Although the sequence is subject to variation,depending upon the nature of a specific failure, theprincipal stages that comprise the investigation &analysis of a failure are:

• Collection of background & selection ofsamples

• Preliminary examination of the failed part(visual examination & record keeping)

• Non destructive testing

• Mechanical testing (including hardness &toughness testing)

• Selection, identification, preservation, and/orcleaning of all specimens

• Macroscopic examination and analysis(fracture surfaces, secondary cracks, & othersurface phenomena)

• Microscopic examination and analysis

• Selection & preparation of metallographicsections

• Examination and analysis of metallographicsections

Collection of Background OperatingDATA:

Boiler operating data just before & at the timeof a tube failure is very important, as it will giveinformation of the service conditions faced by thetube at the time of failure. This operating datashould also be co-related with the past operationdata & abnormalities if any should be taken careoff. Water chemistry analysis, fuel analysis shouldalso form an important part of this data. This data

Section — D 81


& the metallurgical analysis will help us in truesense to arrive at the exact cause of a tube failure.

Investigation of Tube Failure in a Boiler

Study the boiler log sheet & water chemistryrecord prior to tube failure and after tube failure.Preserve the copies of these log sheets. Record,if any abnormality noticed, such as mal operation,malfunction, very high or low temperature/loads,fluctuating loads, sudden increase in load ortemperature, poor water chemistry, start up ventcrack open / close etc. etc. (if possible collectand send the water samples, internal scale fromdrum & tubes, external scale samples).

After entering in boiler and before proceeding totube failure location inspect & record the conditionof boiler and pressure parts without disturbing theevidence i.e. distortion of pressure parts/coils,bulging of pressure parts, scaling / lump formationon pressure parts, blockage of flue gas path, other/ secondary failures etc. etc. In such case takingphotographs will help in great extent in analyzingof the tube failure, boiler problem. The failedpressure part tube should not be hammered, anymechanical impact should be avoided.

Inspect the failed tube and record all findings onthe same as well as its adjacent tubes. Carryout dimensional measurement of failed tube andaffected adjacent tubes.

Number mark the failed tube for its location,flue gas flow, steam flow with oil paint.After completion of inspection, recording andphotography, cut the failed tube and affectedadjacent tube, if any, with the help of HACKSAWonly. Gas cutting of the tubes should be avoidedas much as possible. The failed tube, keeping

the failed portion in middle should be cut for totallength of minimum 350 mm. Immediately aftercutting the tube sample both the ends shouldbe covered with plastic caps. While doing this,internal or external scale of tube should not falldown.

The failed tube samples should be carefullypacked in plastic bag / wooden caseaccompanying duly filled format with waterchemistry of boiler log sheets should be sent toTBW, Pune.

Removal of Failed Tube Sample

• The tube sample should be cut with a hacksawblade. Gas cutting should be avoided

• The sample should be cut approx. 8-10 inchesabove & below the affected area

• The exact location & elevation should bemarked on the tube sample

• The direction of the fluid flow should be markedon the tube sample

• Immediately after cutting the tube sample boththe ends should be covered with plastic caps.Internal or external scale of tube should not falldown

The failed tube sample nicely packed in plasticbag / wooden case accompanying duly filledformat as given below with water chemistry ofboiler log sheets should be sent to TBW H.O formetallurgical investigations.

Tube Failure Analysis ObservationSheet

SR.NO: DATE:

NAME OF THE CUSTOMER

BOILER SPECIFICATIONS

CAPACITY

STEAM PRESSURE

STEAM TEMPERATURE

FUEL FIRED

LOCATION OF TUBE SAMPLE

DURATION OF SERVICE OF BOILER

DURATION OF SERVICE OF TUBE SAMPLE

DATE OF FAILURE

SAMPLE RECEIVED ON

NO. OF SAMPLES HANDED OVER TO LAB ON(With identification Mark/No) Nos. / Date

VISUAL INSPECTION REPORT

Section — D 82


NAME OF THE CUSTOMER

WITH SKETCH / NATURE OF FAILURE

TUBE MATERIAL ( Specified)

TUBE OD x THK (Specified)

ORIENTATION OF TUBE

FLUID FLOW DIRECTION

(With marking)

BOILER OPERATING CONDITION

AT THE TIME OF FAILURE (Water

Chemistry & boiler operation log sheets)

ANY OTHER RELEVANT INFORMATION ABOUT THE FAILURE

5.2 Window Patch Welding

Purpose

The purpose of the window patching method is toallow the welding of tubes that could not otherwisebe welded because of limited access to part of thetube diameter. This procedure is restricted to thatuse.

Preparation

1. The area to be patched shall be cleaned tobare metal

2. The patch shall be made from tube materialof same type, diameter and thickness, as thetube being welded

3. The area of the tube to be removed shall becarefully marked out as close as possible tocontour of the patch. The tube section maythen be removed using an oxyacetylene gascutting torch or by mechanical means

4. The weld preparation shall be made as per theFigure #1. The fit up of the patch weld gapshall be 2.4 0.8 mm

Welding

1. A welder qualified to the requirementsof ASME shall make the tube and patchwelds in accordance with an approved weldprocedure.

2. The root pass shall be done with GTAWprocess. The weld may then be completedwith either SMAW or GTAW process. Someacceptable weld procedure specifications arelisted in Table below

Testing

1. All the tube and patch welding shall besubject to close visual inspection and100% radiography in accordance with therequirements of ASME section V. Thestandard for accepting /rejecting is specifiedin ASME section I

2. Completed welds are subject to hydrostatictest

Base Material Filler Metal

P1 TO P1 CARBON STEEL TO CARBONSTEEL ER 70S.2 E7018

P3 TO P3 CARBON ½ MOLY TOCARBON ½ MOLY ER80S.B2 E7018A1

P3 TO P3 ½ Cr ½ MOLY TO ½ Cr ½MOLY ER80S.B2 E8018B2L

P4 TO P4 1-1/4 Cr TO 1-1/4 Cr ER80S.B2 E8018B2L

P5 TO P5 2-1/4 Cr 1 MOLY TO 2-1/4 Cr1 MOLY ER90S.B3 E9018B3L

P8 TO P8 STAINLESS TO STAINLESS ER308 ER308-16

Section — D 83


Figure 4

Section — D 84


6 General Principal of WeldRepairs

Furnace and Boiler Tubes

• The minimum replacement tube length shouldbe not less than 150 mm. A damaged tubeshould be cut at least 75 mm each side of thedefective area.

• Backing rings must not to be used in weldingheat absorbing tubes carrying water or mixtureof steam and water.

• If a backing ring is not used, the first pass of theweld must be made with inert gas-arc or oxyacetylene. The weld passes may be completedby either process, or by a manual metal arc.

• Pre heat or post heat is not required for weldingcarbon steel furnace or boiler tubes.

• Prior to welding, clean the tube ends to brightmetal inside and outside for at least 40 mmfrom the weld area. Remove all deposits ofoxide, boiler water salts and slag to avoid gasor slag inclusions in the weld.

• Fit-up of the weld joints is important. It isdifficult to obtain accurate cuts on furnacetubes especially those in welded furnace walls.However, it is worth to spend extra time to getthe existing tube ends squared and correctlychamfered and to cut the replacement tubeto the correct length. Poor fit-up increase thepossibility of an unsuccessful weld.

• Allow for shrink in the welding, remember, theweld metal and parent metal are melted in thewelding process and the molten metal shrinksas it solidifies. A butt weld in the tube willshorten the total tube length about 1.6 mm.

• Use a clamp or guide lug to hold one end ofthe replacement tube alignment while the firstweld is made. Do not tack weld both end of thereplacement tubes particularly if the existingtubes are rigidly supported

• As a general rule, first complete the welds atthe lower end of the replacement tube. Do notstart welding the upper end of the replacementtube until both the replacement and the existingtubes have cooled to ambient temperature.

Weld Repair of Small Cracks in Tube

In the interest of saving time and cost, it is betterto weld small cracks rather than replace a lengthof the tube. The crack must be ground out to forman acceptable welding groove. The groove shouldcontinue well beyond the ends of the crack. Inert

gas arc or oxy acetylene process must make thefirst pass of the weld.

Note

This type of the repairs entails somerisk. Internal deposits. Particularlycopper, may exist under the crackwhich will result in damaging the parentand/or weld metal causing failure in ashort period of time.

Over-heating the tube may havecaused the longitudinal crack. In thiscase, the tube has swollen and theweld thickness reduced. In the modernwelded wall construction, it is difficult toaccurately measure the tube diameteror circumference to detect the minorswelling. If visual indicates swellingand reduction of wall thickness atthe crack, a complete replacement ofthe damaged tube length is the bestsolution.

A circumferential crack indicates afailure due to excessive stress appliedby expansion restriction, bending orfatigue; welding can repair such cracks.However, unless the cause of failureis diagnosed and corrected, anothersimilar failure could occur at or nearthe original crack.

Also the tube cannot be cleaned frominside and there is always a possibilityinternal deposits will contaminate theweld.

Plugging Tubes in Drums & Headers

Often after a tube failure, it is desirable to plugthe failed tube in the drum or header shell sothe boiler may be returned to service with theleast possible delay. It is recommended that thefailed tube be replaced whenever possible in lieuof plugging. If the leak is remote from the tubeseats and accessible, the faulty section of thetube should be cut out and replaced rather thanplugging.

Water wall tubes (space tube) should be replacedif possible and plugged only as a last resort. Theplugged tube must be free to expand and distortwith respect to the adjacent tubes. Membranetubes must be repaired and not plugged.

When tubes are plugged, the old tube should beremoved from the boiler setting since it probablywill burn off due to lack of cooling and couldbecome displaced and obstruct gas lanes, foul

Section — D 85


up soot blowers, be dangerous to personnel aftershutdown, and etc. If the tube is not removed fromthe setting, a definite hole must be punched ordrilled in the tube to prevent a possible dangerousbuildup of pressure between the tube plugs.

A expanded tube leaking at the seat should beremoved from its seat and

1. a new tube rolled in,

2. a new short stub rolled in and plugged,

3. the tube end seal welded to the shell or, ifthe drum shell is internally counter bored, acylindrical plug must be installed and sealwelded to the drum shell.

Note

No. (1) is the preferred fix with No. (3)the least preferred.

Seal welding of tube ends, tapered plugs, orcylindrical plugs to the shell should be done insuch a manner as to minimize the heating ofadjacent tube seats, which may become loose.It is essential that the welding process should beas per standard procedure for carbon steel shellsand tubes to be followed very closely to ensuresuccess. Deviations from these parameters willnormally result in unsatisfactory connections.The major welding parameters for shells or tubesother than carbon steel may be obtained fromqualified welding procedures.

Ensure that welders are qualified in accordancewith ASME Section IX and local provincialrequirements. They must also ensure that thewelding is done to the applicable qualified weldprocedure.

It also to be ensured that the proposed repair hasbeen approved by the Boiler Inspection Branch ofthe local jurisdiction.

Machined tube stubs and plugs are used wherethe old tube can be removed from its seat withoutseat damage and for new construction that isdrilled for future addition of tubes. The rolled-intube stub extends into the shell and a solid plugis installed and seal welded to the stub. Thesestubs and plugs are standardized to have onlyone tube stub and one plug for each standardtube hole.

Before rolling stubs in, they should be cleanedinside and outside with a wire brush, abrasivepaper, or a liquid cleaner until the metal is free ofall foreign substances. In general, stubs do notrequire cleaning beyond the removal of dirt, rust,scale or foreign material.

The stub seat (tube hole) should be similarlycleaned. If a liquid solvent is used to clean eitherthe stub and/or tube hole, care must be taken todry the metal completely. Liquid trapped betweenthe stub and its seat prevents contact of the twometal surfaces.

Before the expanding tool is inserted, the insideof the stub should be lubricated with a suitablecompound. The compound selected shouldbe water soluble to facilitate cleanup. Therolling process should not be rushed since heatgenerated during rolling is detrimental to thestrength of the rolled joint. The tube stub isproperly expanded when the wall thickness in theseat is reduced by 6 to 10 percent for generatingtubes and 10 to 14 percent for other boiler tubes.The tube stub wall reduction for thin shells shouldbe less than that for thicker shells. This is toprevent over rolling which could cause adjacenttube seats to leak. Since the stub wall itselfcannot be measured after it is rolled in its seat,the only alternative is to calculate the increasein the stub ID that is necessary to prove that thewall has in fact been reduced by the requiredpercentage. This depends upon the tube seatID (hole diameter), tube stub OD, the clearancebetween these two and also the stub wall. Anexample of this conversion for a 2 ½" OD by0.150-inch wall tube stub for a 10% wall reductionis as follows

MeasureHold Dia

= 2.531

MeasureStub OD

= 2.500 / 0.031 Clearance

MeasureStub ID

= 2.200

Clearance = 0.031 / 2,231 Stub ID @Contact

StubID @Contact

= 2.231

10% of0.150 x2

= 0.030 / 2.261 Stub ID afterexpanding

Plug all internal counter bored holes in the fieldwith the cylindrical plug when the tube is still inthe seat. Some counter bores may be shallowenough that the tube ends are exposed sufficientlyto permit seal welding to a tapered plug. SeeFigure 2. If the tube seat is leaking, then the tubemust either be seal welded to the drum shell or thecounter bore can be plugged with the cylindricalplug and seal welded per Figures 3 and 4. It

Section — D 86


may be necessary to machine the tube ends backin order to provide a seat for the cylindrical pluginstallation. See Figures 3 and 4.

Figure 5 shows the details of this cylindrical plugand gives instruction for the specific plug sizedesired.

Tapered plugs are used to plug existing tubeswhere it is not practical to remove the tube from itsseat and there is no internal counter bore. Theseplugs must be tailor made for each tube diameterand tube wall thickness. Figure 6 shows thedetails of this tapered plug and give instructionsfor a plug to fit tube diameters from 1-3/4" through4 ½" OD and any wall thickness. Figure 7 showsthe arrangement of the tapered plug seal weldedto the tube.

The plugs and seal welds described above aredesigned for the boiler pressure to be on the head(seal weld side) of the plug only. The ¾ inchdiameter by 1/8-inch thick button weld on the plugis to eliminate leakage through the “piping” whichcan occur at the center of some bar stock.

Figure 8 shows a tube seal welded to the shell.This arrangement may be used when the tubeseat is leaking and it is not practical to replace orremove the tube and use a rolled stub and plug.

Economizer headers and superheater headersmay be plugged as shown in Figure 9 & 10where external access is available and theconditions shown on the figures are met. If thoseconditions cannot be satisfied, tube replacementis recommended. In these two figures, thepressure is on the internal end of the plug and theexternal strength weld restrains the plug.

Plugged tubes that are below the horizontalcenterline of the shell will not drain. Therefore,after chemical cleaning it is necessary that theplug to be removed and the stub swabbed out toremove the chemicals in these stubs. The plugcan then be welded back in or in some cases itwill have been destroyed in the removal processand anew one will have to be installed. Caremust be taken in the plug removal process to notdamage or thin the tube stubs wall.

Replacement of Sections of Tubes

Experienced personnel must do the replacementof a section of failed tube. The length of thereplaced section should be a minimum of 12inches. Usual practice is to cut out the defectivesection with an oxyacetylene torch, but it ispreferable to use a saw or wafer disc. Care mustbe taken to prevent slag from entering the tube.

The ends are prepared for welding by grinding orwith special tools.

The root pass of the joint should be depositedwith the gas tungsten arc process. A 3/32-inchdiameter shielded metal arc-welding electrode isrecommended for the remainder of the joint. Thewelding parameters for tubes may be obtainedfrom qualified Welding Procedures.

Removing Tubes from Drums, Headers &Tube Plates

The removal of tubes from their tube seats mustbe done very carefully to prevent damage to thetube seats. If the tube seat is damaged, it maybe impossible to ever roll another tube in andmake a tight seal. Gouging of the tube seat couldalso affect the ligaments between tube holes andintegrity of the shell. Tubes can be removed fromtheir seats without seat damage if the followingprocedures are carefully followed.

With light- gage tubes, it is often possible to coldcrimp the tube end to loosen it in its seat, thendrive or "jack" the tube out. When the tubes aretoo heavy for cold crimping, the two-stage heatingmethod may be used. Heat is applied to the insideof the tube end with a torch. Heat is first appliedfor a short period - not long enough for it to betransferred to the tube sheet.

When the tube end cools, the joint will haveloosened enough so that the second heat willnot be transferred readily to the tube sheet.The tube end can then be heated sufficiently forcrimping and the tube can be pushed out of itsseat. If neither of these methods is applicable,the following methods may be employed.

To remove light tube tubs, it is advisable to cutgrooves about 3/4 inch apart with a round nosechisel. When the tongue (the metal between thetwo grooves) is knocked free, the tube can becollapsed and removed.

To remove heavy gage tubes, the type of groovingtool shown in figure 12 is used to prepare thetongues without damage to the tube seat. It isused with a pneumatic hammer, but it is necessarythat the tool be suited to the tube thickness sothat it will cut the grooves as deep as possibleand yet leave a minimum thickness of metal overthe tube seat. In very heavy gage tubes, a thirdgroove is often cut, as nearly opposite the tongueas possible, so that less heavy pounding will berequired to collapse the stub. These latter twomethods require that the flare on the end of thetube be crimped straight before starting, to cut thegrooves for collapsing the tube. Of course, the

Section — D 87


seal weld around the end of any tube must beground or machined off before attempting to cutthe grooves for collapsing the tube. This mustbe done carefully to prevent damage to the drumshell.

Attached Figures 2 to 10

Figure 5

Section — D 88


Figure 6

Section — D 89


Figure 7

Section — D 90


Figure 8

Section — D 91


Figure 9

Section — D 92


Figure 10

Section — D 93


Figure 11

Section — D 94


Figure 12

Section — D 95


Figure 13

Section — D 96


7 Failure Reporting Format

Enclosed is a format for reporting of failure ofequipment etc.

The enclosed formats are exclusively for the useby O & M engineers of the client for reportingany malfunctioning or failure of the boiler pressureparts and its auxiliaries. Most of the boilers atsite need to be investigated with the help of pasexperience and guidance from the O & M. TheO & M, in turn, required precise and systematicinformation on which the failure analysis will haveto be based.

TBW request the boiler users to report to TBWany problems that they may come across duringroutine O & M of the plant, immediately onoccurrence.

It is suggested that enclosed formats be used forthis purpose and help provide better and quickerservices for trouble shooting.

There may be cases when problems arisingduring the O & M are resolved on temporaryor permanent basis by the O & M engineersand there may not be any immediate need forservice of TBW or OEM. Even in such cases it isthe request of TBW with the enclosed reportingformats be filled in and faxed over to TBW, Pune.

This will go a long way to generate a data bankon the auxiliary equipments and come out withimprovement rather for the final users.

Customer Feed Back form

Customer Details:

COMPANY NAME

COMMUNICATION ADDRESS

TELEPHONE NUMBER

FAX NUMBER

E-MAIL ADDRESS

CONTACT PERSON

OTHER DETAILS (IF ANY)

Boiler Details:

BOILER NUMBER :

DATE OF COMMISSIONING

BOILER CAPACITY – MCR

STEAM PRESSURE

STEAM TEMPERATURE

FUEL FIRED

Feed Back Details: Equipment Details:

SL.NO PROBLEM DETAILS OBSERVATIONS CORRECTIVEACTIONS TAKEN

COMMENTS /RECOMMENDATIONS

OTHERINFORMATIONS:

EXPECTATIONSFROM TBW :

REPLYAWAITED/ SERVICEENGINEERVISIT :

SIGNATURE &DATE:

Section — D 97


8 Water Chemistry

Introduction

The natural water contains solid, liquid andgaseous impurities and therefore, this cannot beused for the generation of steam in the boilers.The impurities present in the water should beremoved before its use for steam generation.The necessity for reducing the corrosive natureand quantity of dissolved and suspended solidsin feed water has become increasingly importantwith the advent of high pressure, critical andsupercritical boilers.

The impurities present in the feed water areclassified as given below

1. Un dissolved and suspended solid materials.

2. Dissolved salts and minerals.

3. Dissolved gases.

4. Other materials (a soil, acid) either in mixedand unmixed forms.

8.1 Undissolved and Suspended SolidMaterials

A) Turbidity and Sediment:

Turbidity in the water is suspended insolublematter including coarse particles (mud, sedimentsand etc,) that settle rapidly. Amounts rangesfrom almost zero in most ground waters and60,000 ppm. in muddy and turbulent river water.The turbidity of feed water should not exceed5 ppm. These materials can be removed bysettling coagulation and filtration. Their presenceis undesirable because heating or evaporationproduces hard stony scale deposits on theheating surface and clog fluid system. Both areobjectionable as they cause damage to the boilersystem. A standard of measurement of hardnessis taken as being the amount of calcium carbonate(CaCO3) in the water and is referred to in part permillion (ppm) or grains per gallon (grain/gallon) X17.1 = ppm.

B) Sodium and Potassium Salts:

These are extremely soluble in water and donot deposit unless highly concentrated. Theirpresence is troublesome as they are alkaline innature and accelerate the corrosion.

C) Chlorides:

Majority of the chloride causes increasedcorrosive action of water.

D) Iron:

Most common soluble iron in water is ferrousbicarbonate. The water containing ferrousbicarbonate deposits becomes yellowish andreddish sediment of ferric hydroxide if exposedto air. Majority of ground surface water containsless than 5 ppm but 0.3 ppm, can create troublein the feed water system by soft scale formationand accelerating the corrosion.

E) Manganese:

It also occurs in similar form as iron and it is alsoequally troublesome.

F) Silica:

Most natural water contains silica ranging from 1to 100 ppm. Its presence is highly objectionableas it forms very hard scale in boilers and formsinsoluble deposits on turbine blades. In modernhigh-pressure boilers its presence is reduced aslow as 10-50 ppm.

G) Microbiological Growths:

Various growths occur in surface water (lakeand river). The microorganisms include diatons,molds, bacterial slimes, algae; manganese andsulfate reducing bacteria and many others. Thesecan cause coating on heat exchanger and clogthe flow passages and reduce the heat transferrates.

H) Color:

Surface waters from swampy areas becomehighly colored due to decaying vegetation. Colorof feed water is objectionable as it causes foamingin boilers and may interfere by chlorinating ofabsorption by activated carbon.

8.2 Dissolved Salts and Minerals

A) Calcium And Magnesium Salts:

The calcium and magnesium salts present in thewater in the form of carbonates, bicarbonates,sulfates and chlorides. The presence of thesesalts is recognized by the hardness of the water(hardness of water is tested by soap test). Thehardness of water is classified as temporary andpermanent hardness. The temporary hardnessis caused by the bicarbonates of calcium andmagnesium and can be removed by boiling. Theboiling converts the soluble bicarbonates intoless soluble carbonates, which can be removedby simple blow-down method. The presenceof chlorides, sulfates and nitrates of calcium

Section — D 98


cause the permanent hardness of the water andmagnesium and they cannot be removed just byboiling because they form a hard scale on heatingsurfaces.

8.3 Dissolved Gases

A) Oxygen:

It presents in surface water in dissolved form withvariable percentage depending upon the watertemperature and other solid contents in water. Itspresence is highly objectionable, as it is corrosiveto iron, zinc, brass and other metals. It causescorrosion and pitting of water lines, boilers andheat exchangers. Its effect is further acceleratedat high temperature.

B) Carbon Dioxide:

The river water contains 50 ppm & well watercontains 2-50 ppm of CO2. It also helps toaccelerate the corrosive action of oxygen.

The other gases are H2S, CH4, N2 and manyothers but their percentage are negligibleTherefore their effects are not discussed here.

8.4 Other Materials

A) Free Mineral Acid:

Usually present as sulfuric or hydrochloric acidand causes corrosion. The presence is requiredby neutralization with alkalis.

B) OIL:

Generally the lubricating oil is carried with steaminto the condenser & thorough the feed system tothe boiler. It causes sludge, scale & foaming inboilers. Strainers and baffle separators generallyremove it.

The effects of all the impurities present in thewater are the scale formation on the differentparts of the boiler system and corrosion. Thescale formation reduces the heat transfer ratesand clogs the flow passage and endangers thelife of the equipment by increasing the tempabove the safe limit. The corrosion phenomenonreduces the life of the plant rapidly. Therefore itis absolutely necessary to reduce the impuritiesbelow a safe limit for the proper working of thepower plant.

8.5 pH Value of the Water and itsImportance

The pH value of the feed water plays veryimportant controlling the corrosion. pH is a

number denoting the degree of acidity or alkalinityof a substance. It does not indicate the quantityof acid or alkali in a solution as found by filtrationmethod. It is derived by measuring the amount ofhydrogen ion (H+) in grams per liter of solution.The greater the amount of hydrogen ions presentin solution its acid reaction becomes stronger.Therefore, pure water is being neutral solution,any solution producing more hydrogen ion thanpure water will be acidic and degree is governedby difference and other solution producing lesshydrogen ions than pure water will be alkaline andthe degree is also governed by the difference.

The Role OF pH IN Corrosion:

The role of pH in corrosion of metals is extremelyimportant. The corrosion rate of iron in theabsence of oxygen is proportional to pH up to avalue of 9.6. At this point, hydrogen gas formationand dissolving of iron practically stops. This isthe came pH produced by a saturated solution offerrous hydroxide Fe (OH) 2.

The Oxygen in the water unites with ferroushydroxide to form ferric hydroxide. This reactionlowers pH of the solution and levels to stimulatecorrosion.

Alkalinity adjustment and film formation areclosely related. The pH value of feed water shouldbe maintained greater than 9.6 to reduce thecorrosion effects caused by the reason mentionedabove. The required alkalinity of feed water isadjusted by adding soda ash caustic soda ortrisodium phosphate. The calcium hardness,alkalinity and pH are inter-related variables inscale control. Calcium carbonate is one of themost troublesome deposits responsible for scaleformation.

8.6 Effects of Impurities

The major troubles caused by the feeding ofwater of undesirable quality are scale formation,corrosion, foaming, caustic embrittlement,carry-over and priming. The details describedbelow: -

1. Scale Formation

Feed water containing a group of impurities indissolved and suspended form flows into theBoiler for continuos generation of Steam. Withconversion of water into steam in Boiler, solidsare left behind to concentrate the remainingwater. The scale formation tendency increaseswith the increase in temperature of feed water.Because, the solubility of some salts (as calciumsulphite) decreases with the increase in feedwater temperature. Calcium sulphite has solubility

Section — D 99


of 3200 ppm. at 15 Deg. C and it reduces to 55ppm. at 230 Deg. C and 27 ppm. At 320 Deg. C.

Scale formation takes place mainly due to saltsof calcium and magnesium. Sometimes, it iscemented into a hard mass by Silica. Among all,calcium is the principal offender and particularly,Calcium sulphate, magnesium sulphate and otherChlorides are sufficiently soluble in water and arenot much troublesome. Sodium salts are highlysoluble in water and are non-scale forming.

The scale formation takes place mainly in feedwater piping and Boiler Tubes. Its first effect onthe piping system is to choke the flow of water byreducing the flow area and increases the pressurerequired to maintain the water delivery. Anothereffect of scale formation is to reduce the transferof heat form the hot gases to water. Real dangersof the scale formation exist in radiant heat zonewhere boiler tubes are directly exposed to thecombustion. The scale formation retards the flowof heat and metal temperature increases. Even athin layer of scale in high heat zone can over-heatthe metal enough to rupture the tubes. The metaltubes weakened due to over-heating yield topressure providing a protrusion known as bag.Such bag provides a pocket for the accumulationof sludge and scale, which eventually causesfailure. The over-heating of metal causes layer ofmetal to separate and form a blister.

2. Corrosion

The corrosion is eating away process of boilermetal. It causes deterioration & failure of theequipment, eventually this cause for major repairsor expensive shut -downs or replacements.

The corrosion of boilers, economizers, feedwater heaters & piping is caused by an acid orlow PH in addition to the presence of dissolvedoxygen & carbon dioxide in the boiler feed water.The presence of oxygen is mostly responsiblefor corrosion among all other factors. Thepermissible limit of oxygen content varies with theacidity of water. Generally it should not shouldexceed 0.5 cc per liter .O2 generally entersinto closed system through make up condenserleakage and condensate pump packing.

CO2 is next to O2, which is responsible forcorrosion. The CO2 comes out of bicarbonateson heating and combines with water to form weakacids known as carbonic acid. This acid slowlyreacts with iron and other metals to form theirbicarbonates. The newly formed bicarbonates ofmetals decompose by heat once more and CO2 isagain liberated. This gas again unites with water

to form carbonic acid and the cycle is repeated.Adding alkali solution to neutralize acids inwater and raise the PH value can minimize thecorrosion. The effect of CO2 is minimized by theaddition of ammonia or neutralizing the amines inwater. This is necessary because CO2 lowers thePH of the boiler feed water and dissolved solidsto leave the boiler.

The priming is a violent discharge of water withsteam from the boiler. It can be compared to thepumping of water that frequently accompaniesrapid heating in a open vessel. In priming thewater level in the boiler undergoes rapid andgreat changes and there are violent dischargesof bursting bubbles. Therefore ‘sludge’ of boilerwater is thrown over with the steam.

The priming is caused due to improper boilerdesign, improper method of firing, overloading,sudden load changing or a combination of thesefactors. The priming effect is reduced by installingsteam purifier, lowering water level in the boilerand maintains constant load on boilers.

The foaming is the formation of small andstable bubbles throughout the boiler water. Thehigh percentage of dissolved solids, excessivealkalinity and presence of oil in water areresponsible for foaming.

Boiler water solids are also carried over in themoisture mixed with steam even when there isno indication of either priming or foaming. Thisis known as ‘carry-over’. The carry-over of boilerwater solids is partly a mechanical and partly achemical problem. The amount of suspendedsolids and alkalinity in the boiler water is alsoimportant in addition to other reasons like boilerdesign, high water level, and overloading andfluctuating loads on boiler.

3. Caustic Embrittlement

The caustic embrittlement is the weakening ofboiler Steel as a result of inner crystalline cracks.This is caused by long exposure of boiler steel tocombination of stress and highly alkaline water.

The course of embrittlement takes place underfollowing condition:

a) When boiler water contains free hydroxide,alkalinity and some silica. It has been alwaysfound that the feed water was high in sodiumbicarbonate, which broke down into sodiumcarbonate in the boiler and partially hydralizedas shown by the following reaction in case ofembrittlement.

Section — D 100


Na2CO3 + HOH = CO2 + 2 NaOH

b) Slow leakage of boiler water through a joint orseam.

c) Boiler metal is highly stressed at the point ofleakage. This may be caused by faulty design andexpansion etc.

The prevention of caustic embrittlement consistsof reducing the causticity or adding inhibitingagents to the feed water. The most practicalmethod of preventing caustic embrittlement is toregulate the chemical composition of the boilerwater. The obvious solution to embrittlement isto eliminate all free NaOH from feed water byaddition of Phosphates.

9 Feed & Boiler Water Conditioning

1. Introduction

The successful use of boiler is dependent onproper water conditioning and treatment. Thequality of water must have accurate for troublefree operation of boiler.

The water as available to industry is not suitablefor boiler use. A complete pre-treatment andinternal chemical treatment is necessary to makeraw water suitable for boiler feed.

The objective of the water treatment is:

• Eliminate scaling - deposition in boiler whichcause tube over heating leading to accidents.

• Control corrosion of boiler system, which causefailure of boiler tubes, leading to unscheduledshutdowns.

• Reduce carry over of water with steam, which isthe cause of deposition on super heater/turbineblades, leading to the expensive failures.

• To maintain peak boiler efficiency by keepingcomplete boiler water system clean.

In order to meet above objectives, it is necessaryto maintain certain chemical conditions in boiler,condense and feed water systems. A brief reviewof important factors is given in this section to assistthose taking charges of new boiler equipment. It isnot possible to cover the subject fully, there fore, itis recommended that the care and control of waterquality be entrusted to water treatment specialist.

2. Need for Water Treatment

A. Corrossive Control

Water is corrosive to boiler metal. Typicallycorrosion due to water will reduce thickness oftube @ 1 mm/year. Thus the life and safety of

boiler entirely depends on the rate of corrosionof boiler metal. In order to protect boiler fromcorrosion, pre-treatment is done to removeexcessive corrosion ions like chloride, sulphateetc. However, further chemical conditioning isrequired to protect boiler and auxiliary systemsfrom corrosion.

Tri sodium phosphate, caustic, ammonia andamines are used as corrosion inhibitors. Thesechemicals form a protective film over metalsurface and reduce corrosion. It is necessaryto maintain prescribed concentration of thesechemicals in boiler water systems continuously.

B. Oxygen Corrosion Inhibitor:

Oxygen is present in dissolved form in water.At high temperature, oxygen reacts with metalto cause pitting corrosion. Thus prevention ofoxygen lead to pin holes in economizer, steamdrums and steam tubes.

Most of the oxygen is removed externally bydeaerator and preheating of feed water. However,traces of residual oxygen must be removed bychemical conditioning.

Sodium sulfite, hydrazine and amines arerecommended for oxygen removal. Thesechemicals react with residual oxygen makingit inactive and protect metal against pittingcorrosion. Catalyzed oxygen scavengers areused for quick reaction.

C. Scale / Deposit Control:

Raw water contains dissolved solids, hardnesssalts and suspended matters.

External treatment is used to remove suchimpurities.

• Clarification - To remove suspended matters.

• Filtration - To remove residual turbidity

• Softening - To remove hardness salts

Dealkaliser - To remove hardness salts andexcessive alkalinity

• Demineralization - To remove residual saltsand silica

• Mixed bed - To remove residual salts and silicafrom DM water.

A combination of above equipments are used toremove undesirable impurities in raw water.

Scale Control

Hardness salts in feed water cause formation inboiler. Under temperature and pressure inside theboiler and due to concentration, hardness salts

Section — D 101


precipitate in tubes as calcium carbonate, calciumsulphate and Ca/Mg silicate scales.

External treatment like softening,demineralization or de-alkalisation removes mostof the hardness salts from boiler feed water.However, malfunctioning of this equipment,occasional bypassing of the softener/DM plant orcontamination of condensate or feed water withraw water often led to ingress of hardness in theboiler.

All hardness salt precipitate inside boiler leadingto hard scale formation on tubes. Such scalehas lower conductivity causing increase in metaltemperature, leading to bursting of tubes inextreme conditions.

Therefore, inspire of elaborate external treatment,internal chemical conditioning is alwaysrecommended as additional safety. Followingchemical methods are used for internal treatment.

Phosphate Conditioning

Trisodium phosphate is commonly used.Hardness salts react with trisodium phosphateto form calcium phosphate precipitate. Thisprecipitate above pH of 9.5 colloidal in natureand therefore do not allow for form hard scaleof carbonate and silicates. The precipitatedhardness salts are then removed through blowdown as sludge and boiler tubes are kept scalefree.

Trisodium phosphate, apart from actingas hardness conditioning agent, also is agood corrosion inhibitor. The recommendedconcentration in boiler water is given in Table -1

Note 1 : TSP will act as hardness conditioner,only when boiler pH is above 9.5 . Below 9.5pH TSP may cause hard scale formation of Ca3(PO)2. Therefore, coordinated or congruentphosphate treatment is recommended. The watertreatment experts can advise you right treatmentafter studying your water quality and operationconditions.

Thermax Chemicals can provide services forarriving at right chemical treatment for your boiler.

Chelant- Polymer treatment:

Hardness scales do not precipitate in presence ofchelant like NTA/EDTA The chelant treatment isrecommended when hardness ingress in boiler isexperienced regularly.

Excessive chelant dosing causecorrosion of boilerHence balanced chelant program asrecommended by experts should beused.

Organic polymer conditioners are used toprevent hardness scales. Such organic polymerdisperse scale forming compounds like CaCO3& Ca(PO4)2 in colloidal form facilitating theirremoval through blow down. Polymer andcopolymer of acrylic, methacrylic, styrene maleicacrylics are commonly used. Most of the polymersare proprietary in nature and therefore dosage isbest recommended by manufacturer.

D. Fouling Control

Suspended matter, oil/grease /oxygen & ironsalts commonly cause fouling inside the boiler.Most of the suspended matter and iron salts areremoved by external treatment. However due tomfg. of these equipment, contamination throughcondensate and concentration in boiler causefouling of boiler tubes.

Similar to hardness scales, such foulants arepoor conductor of heat. Thus fouling causesoverheating of tubes.

Fouling can best be avoided bymaintaining qualityof feed water as per norms. In case of upsetsor occasional contamination, polymeric disersenthelp to prevent fouling due to turbidity and organicmatter. Iron is picked up mostly in condensatesystem due to corrosion of condensate line. Insuch case, condensate corrosion inhibitor likeammonia cyclohexylamine and filming amine isrecommended.

E. Turbine / Superheater Deposition Control:

The solids in boiler feed water get concentratedin boiler. The concentration of solids in boiler isdecided blowdown and feed water quality. Thecarryover of boiler water with steam depends on;

Mechanical Factors:

• Boiler load - Higher the load, lower is the steampurity

• Water level in boiler - Higher the water level indrum, lower is steam purity.

• Load Variation - Sudden increase in loadreduce steam purity for short time.

Section — D 102


• Separation efficiency - Higher efficiency, betteris steam purity.

Chemical Factors:

• TDS - Higher TDS in boiler, lower is steampurity.

• Total Alkalinity - Higher alkalinity as % of TDSlower is steam purity

• Organics - Higher the organic contamination,lower is steam purity.

• Foaming - Higher the foaming character ofwater, Lower is steam purity.

The water carried over with steam due toabove reasons is exactly similar in quality toblow-down or boiler water. In superheater or inturbines, water evaporates, leaving dissolved andsuspended matter as scales or deposits.

Thus severity of scaling and fouling of superheaterand turbine depends on boiler water quality andsteam purity.

Maintaining boiler water quality as per norms andmaximum steam purity is the only way to preventdeposition due to carryover of water with steam.Antifoam agents help to some extend to improvesteam purity in case of excessive in boiler.

F. Silica Deposit Control:

Silica is volatile under high temperatureand pressure inside boiler. In turbines, theevaporated silica precipitates during pressureand temperature reduction and form hard scales.

Maximum allowable concentration of silicadepends on water analysis. Expert’s best decidethe maximum permissible concentration afterstriding the operating parameters.

G. Condensate Corrosion Control:

The carbon dioxide is present in boiler feed waterin dissolved and combined from as carbonate.Under boiler pressure and temperature it isliberated and carried over with steam as CO2gas. This gas re dissolves in steam condensateto form carbonic acid.

CO2 + H2O = H2CO3

H. Maintenance of Peak Efficiency:

Corrosion, scaling, fouling carryover andcondensate corrosion can cause unscheduledshutdown, accidents and deterioration of systemefficiency.Therefore for trouble free operationand maintenance peak operation efficiency,a combination of various internal chemicaltreatments is essential along with a good controlover boiler water quality.

Maintaining boiler water quality by usingcommodity chemicals likes TSP, Hydrazine, andSodium sulfite. However, it is recommendedthat the care and control of water chemistry beentrusted to specialist.

Section — D 103


Section E

This section holds the Lubrication Scheduleand Spare Part List for the HCFM Boiler.

Lubrication Schedule

Lubrication Schedule

Spare Part List

Spare Part List for HCFM Boiler

Section E 104

./O & M Manual.pdf.ditaLinks/SEC - E -LUB Schedule.pdf

./O & M Manual.pdf.ditaLinks/SEC_E_ Spares List.pdf


Volume 2 — Drawings


♦ List of Drawings

Volume 2 — Drawings 105


List of Drawings

01. G. A. of 5 x 115 TPH NG - LDO Fired Boiler_D11-0FM-08050_Rev.5.pdf

02. Pressure Part Assly._D11-0FM-08053_Rev.1.pdf

03. P&ID For Steam & Water_D12-0FM-3232P_Rev.1.pdf

04.P&ID For Deaerator, FWP & Dosing System_D12-0FM-3233P_Rev.1.pdf

05. P&ID For Firing _D12-1FM-6516P_5 Sheet 1.pdf

06. P&ID For Firing _D12-1FM-6516P_5 Sheet 2.pdf

07. P&ID For Steam & Water (Sheet 1) Boiler 1_D12-1FM-6710P_Rev.2.pdf

08. P For Steam & Water (Sheet 2) Boiler 1_D12-1FM-6711P_Rev.2.pdf

09. P For Deaerator (Sheet 1)_D12-1FM-6712P_Rev.2.pdf

10. P For Dosing System For Boiler 1_D12-1FM-6713P_Rev.2.pdf

11. Stack Assly & Details_ G27-0FM-08191_Rev.0.pdf

12. 32 inch Gas Burner Sys. Type for 5’ W-B with LH Gas Inlet_L11-1FM-46313_Rev.0.pdf

13. 32 inch Gas Burner Sys. Type for 5’ W-B with RH Gas Inlet_L11-1FM-46314_Rev.0.pdf

14. Assly & Details of Windbox_ L12-1FM-47132_Rev.1.pdf

15. Steam Drum_ (1500 ID)_P21-0FM-08001_Rev.1.pdf

16. Internal Attach. of Steam Drum_P21-0FM-08002_Rev.0.pdf

17. Steam Purifier Assly (1500 ID Steam Drum)_P21-0FM-08003_Rev.0.pdf

18. Superheater Coil & Header_P4J-1FM-44958_Rev.1.pdf

19. Economiser Header & Coil Assly_PM2-2FM-40727_Rev.3.pdf

20. Gen. Arran. of Refractory_R11-0FM-08342_Rev.0.pdf

21. Steam Drum Refractory_R11-2FM-42104_Rev.0.pdf

22. G.A. of Deaerator_W21-1FM-45966_Rev.3.pdf

23. Assly & Details for Blow Down Tank_W31-1FM-48306_Rev.1.pdf

List of Drawings 106

./O & M Manual.pdf.ditaLinks/01. G. A. of 5 x 115 TPH NG - LDO Fired Boiler_D11-0FM-08050_Rev.5.pdf

./O & M Manual.pdf.ditaLinks/02. Pressure Part Assly._D11-0FM-08053_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/03. P&ID For Steam & Water_D12-0FM-3232P_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/04. P&ID For Deaerator, FWP & Dosing System_D12-0FM-3233P_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/05. P&ID For Firing _D12-1FM-6516P_5 Sheet 1.pdf

./O & M Manual.pdf.ditaLinks/05. P&ID For Firing _D12-1FM-6516P_5 Sheet 2.pdf

./O & M Manual.pdf.ditaLinks/07. P&ID For Steam & Water (Sheet 1) Boiler 1_D12-1FM-6710P_Rev.2.pdf

./O & M Manual.pdf.ditaLinks/08. P&ID For Steam & Water (Sheet 2) Boiler 1_D12-1FM-6711P_Rev.2.pdf

./O & M Manual.pdf.ditaLinks/09. P&ID For Deaerator (Sheet 1)_D12-1FM-6712P_Rev.2.pdf

./O & M Manual.pdf.ditaLinks/10. P&ID For Dosing System For Boiler 1_D12-1FM-6713P_Rev.2.pdf

./O & M Manual.pdf.ditaLinks/11. Stack Assly & Details_ G27-0FM-08191_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/12. 32 inch Gas Burner Sys. Type for 5' W-B with LH Gas Inlet_L11-1FM-46313_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/13. 32 inch Gas Burner Sys. Type for 5' W-B with RH Gas Inlet_L11-1FM-46314_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/14. Assly & Details of Windbox_ L12-1FM-47132_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/15. Steam Drum_ (1500 ID)_P21-0FM-08001_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/16. Internal Attach. of Steam Drum_P21-0FM-08002_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/17. Steam Purifier Assly (1500 ID Steam Drum)_P21-0FM-08003_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/18. Superheater Coil & Header_P4J-1FM-44958_Rev.1.pdf

./O & M Manual.pdf.ditaLinks/19. Economiser Header & Coil Assly_PM2-2FM-40727_Rev.3.pdf

./O & M Manual.pdf.ditaLinks/20. Gen. Arran. of Refractory_R11-0FM-08342_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/21. Steam Drum Refractory_R11-2FM-42104_Rev.0.pdf

./O & M Manual.pdf.ditaLinks/22. G.A. of Deaerator_W21-1FM-45966_Rev.3.pdf

./O & M Manual.pdf.ditaLinks/23. Assly & Details for Blow Down Tank_W31-1FM-48306_Rev.1.pdf


Volume 3 — E & I Specifications


♦ Section 1♦ Section 2♦ Section 3♦ Section 4♦ Section 5♦ Section 6♦ Section 7♦ Section 8♦ Section 9♦ Section 10♦ Section 11♦ Section 12

Volume 3 — E & I Specifications 107


Section 1

Electrical Motor Selection for FD Fan Motor.pdf

Section 2

2.1 Boiler Utility Consumption List.pdf

2.2 Cause and Effect Diagram.pdf

Section 3

Instrument Erection Drawings.pdf

Section 4

4.1 Control Schematic Diagram.pdf

4.2 Logic Diagram for BMS.pdf

Section 5

5.1 D13-FM-CS-32491.pdf

5.2 BMS PLC IO List.pdf

5.3 BCS IO.pdf

5.4 BMS Logic Narrative.pdf

5.5 Electrical System Requirements for Motor Selection (EMS1).pdf

Section 6

6.1 Motorised Valves and Actuators Specification (Non Integral).pdf

6.2 Electrical Load List.pdf

6.3 General Specifications for Electrical Cabling and Erection Material.pdf

Section 7

7.1 Electrical Junction Box Specifications.pdf

7.2 Local Control Stations (General Specification).pdf

7.3 Specification for Aviation Lamp.pdf

Section 8

8.1 Boiler Control Panel (BCP) Specifications.pdf

8.2 Burner Management System (BMS) PLC Specs.pdf

8.3 Arrangement for Local Burner Panel.pdf

Section 9

9.1 Local Burner Panel Specifications.pdf

9.2 Field Junction Box and Cable Schedule.pdf


./O & M Manual.pdf.ditaLinks/Electrical Motor Selection for FD Fan Motor.pdf

./O & M Manual.pdf.ditaLinks/2.1 Boiler Utility Consumption List.pdf

./O & M Manual.pdf.ditaLinks/2.2 Cause and Effect Diagram.pdf

./O & M Manual.pdf.ditaLinks/Instrument Erection Drawings.pdf

./O & M Manual.pdf.ditaLinks/4.1 Control Schematic Diagram.pdf

./O & M Manual.pdf.ditaLinks/4.2 Logic Diagram for BMS.pdf

./O & M Manual.pdf.ditaLinks/5.1 D13-FM-CS-32491.pdf

./O & M Manual.pdf.ditaLinks/5.2 BMS PLC IO List.pdf

./O & M Manual.pdf.ditaLinks/5.3 BCS IO.pdf

./O & M Manual.pdf.ditaLinks/5.4 BMS Logic Narrative.pdf

./O & M Manual.pdf.ditaLinks/5.5 Electrical System Requirements for Motor Selection (EMS1).pdf

./O & M Manual.pdf.ditaLinks/6.1 Motorised Valves and Actuators Specification (Non Integral).pdf

./O & M Manual.pdf.ditaLinks/6.2 Electrical Load List.pdf

./O & M Manual.pdf.ditaLinks/6.3 General Specifications for Electrical Cabling and Erection Material.pdf

./O & M Manual.pdf.ditaLinks/7.1 Electrical Junction Box Specifications.pdf

./O & M Manual.pdf.ditaLinks/7.2 Local Control Stations (General Specification).pdf

./O & M Manual.pdf.ditaLinks/7.3 Specification for Aviation Lamp.pdf

./O & M Manual.pdf.ditaLinks/8.1 Boiler Control Panel (BCP) Specifications.pdf

./O & M Manual.pdf.ditaLinks/8.2 Burner Management System (BMS) PLC Specs.pdf

./O & M Manual.pdf.ditaLinks/8.3 Arrangement for Local Burner Panel.pdf

./O & M Manual.pdf.ditaLinks/9.1 Local Burner Panel Specifications.pdf

./O & M Manual.pdf.ditaLinks/9.2 Field Junction Box and Cable Schedule.pdf


Section 10

10.1 Transmitters and Analysers.pdf

10.2 Gauges and Switches.pdf

10.3 Valves and Actuators.pdf

10.4 Sensors and Amplifiers.pdf

10.5 Power Cylinder.pdf

10.6 SWAS System Specification.pdf

Section 11

11.1 Specification for Motorised Valves.pdf

11.2 Valve Schedule.pdf

11.3 Valve Schedule for Oil & Gas Firing.pdf

Section 12

12.1 Specification for Continuous Blowdown Valve.pdf

12.2 Specification for Intermittent Blowdown Valve.pdf


./O & M Manual.pdf.ditaLinks/10.1 Transmitters and Analysers.pdf

./O & M Manual.pdf.ditaLinks/10.2 Gauges and Switches.pdf

./O & M Manual.pdf.ditaLinks/10.3 Valves and Actuators.pdf

./O & M Manual.pdf.ditaLinks/10.4 Sensors and Amplifiers.pdf

./O & M Manual.pdf.ditaLinks/10.5 Power Cylinder.pdf

./O & M Manual.pdf.ditaLinks/10.6 SWAS System Specification.pdf

./O & M Manual.pdf.ditaLinks/11.1 Specification for Motorised Valves.pdf

./O & M Manual.pdf.ditaLinks/11.2 Valve Schedule.pdf

./O & M Manual.pdf.ditaLinks/11.3 Valve Schedule for Oil & Gas Firing.pdf

./O & M Manual.pdf.ditaLinks/12.1 Specification for Continuous Blowdown Valve.pdf

./O & M Manual.pdf.ditaLinks/12.2 Specification for Intermittent Blowdown Valve.pdf


Volume 4 — Vendor Manuals


♦ Section 01♦ Section 02♦ Section 03♦ Section 04♦ Section 05

Volume 4 — Vendor Manuals 110


Section 01

Fan — TLT Engineering

O & M Manual

FD Fan Manual

Drawing

Drawing

Data Sheet

Data Sheet

Section 02

Scanner Cooling Fan — Andrew Yule

O & M Manual

Manual

Drawings

Drawing

Section 03

3.1 Drum Level Gauges – Chemtrol

O & M Manual

Drum Gauge Glass Manual- Trasperent type

Drawings

Drawing

3.2 Magnetic Level Gauge – Chemtrol

O & M Manual

Magnetic Gauge Glass Manual

Drawings

Drawing

Section 04

Process Valve – KSB

Manuals

Manual

Drawings

PF1051 Drawing —1

PF1051 Drawing —2

PF1052 Drawing —1

PF1052 Drawing —2


./O & M Manual.pdf.ditaLinks/FD FAN MANUAL- ANDREW YULE.pdf

./O & M Manual.pdf.ditaLinks/FD Fan Drawing.pdf

./O & M Manual.pdf.ditaLinks/1- FD Fan Data Sheets.pdf

./O & M Manual.pdf.ditaLinks/2 Scanner Cooling Fan.pdf

./O & M Manual.pdf.ditaLinks/Scanner cooling Fan Drawing.pdf

./O & M Manual.pdf.ditaLinks/Transparent level gauge.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/4 - Cairn Energy Drum LG Rev.1.pdf

./O & M Manual.pdf.ditaLinks/magnetic level gauge.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Magnetic level gauge.pdf

./O & M Manual.pdf.ditaLinks/Process Valve KSB.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/3 - Process valve drawing/08100434/CL4 16908 R0.pdf





PF1053 Drawing —1

PF1053 Drawing —2

PF1054 Drawing —1

PF1054 Drawing —2

PF1055 Drawing —1

PF1055 Drawing —2

Data Sheets

Data Sheet — PF1051


Section 05

5.1 Safety Valve – Tyco Sanmar

O & M Manual

HCI — Manual

Standard Manual —1

Manual — 2

Manual — 3

Manual — 4

Data Sheets

SV Data Sheets of — PF1051





Drawings

SV Drawing of — PF1051 To PF1055

5.2 Relief Valve – Tyco Sanmar

O & M Manual

Manual

Manual

Data Sheets






Drawings

Drawing PF1051 To 1055








./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/3 - Process valve drawing/Process valve data sheet - 1052-55/Data sheet -Process valve -1052.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/3 - Process valve drawing/Process valve data sheet - 1052-55/Data sheet -Process valve -1053.pdf

./O & M Manual.pdf.ditaLinks/HCI.pdf

./O & M Manual.pdf.ditaLinks/Installation Instuctions for Safety Valves - Tyco Sanmar.pdf

./O & M Manual.pdf.ditaLinks/Installation, Maintenance & Adjustment Instruction (HCI) - Tyco Sanmar.pdf

./O & M Manual.pdf.ditaLinks/Installation, Maintenance & Adjustment Instruction (HSJ) - Tyco Sanmar.pdf

./O & M Manual.pdf.ditaLinks/Installation, Operating & Maintenance Instruction (HPV-ST)- Tyco Sanmar.pdf

./O & M Manual.pdf.ditaLinks/SV data sheet-1.pdf





./O & M Manual.pdf.ditaLinks/SV Drawing.pdf

./O & M Manual.pdf.ditaLinks/JOS-E Relief Valve.pdf

./O & M Manual.pdf.ditaLinks/JOSJBS.PDF

./O & M Manual.pdf.ditaLinks/RV data sheet - 1.pdf





./O & M Manual.pdf.ditaLinks/RV drawing.pdf




♦ Section 01♦ Section 02♦ Section 03♦ Section 04♦ Section 05♦ Section 06♦ Section 07



Section 01

Pressure Transmitter (3051) – Emerson

O & M Manual

Manual — 3051S

Section 02

Temperature Transmitter (644H) – Emerson

O & M Manual

Manual — 644H

Section 03

Oil Flow Meter (1700R) - Emerson

O & M Manual

Manual — 1700R

Section 04

O2 Analyser (ZR22G) – Yokogawa

O & M Manual

Manual — ZR402G

HART Protocol

O & M Manual

Manual — ZR

Section 05

Flame Scanner – Fireeye

O & M Manual

Manual — 95UA

Section 06

6.1 Thermocouple Assembly– Pyro Electrical

O & M Manual

Manual

6.2 Damper Actuator - Keltron Controls

O & M Manual

Manual


./O & M Manual.pdf.ditaLinks/3051S Pressure Transmitter.pdf

./O & M Manual.pdf.ditaLinks/644H& 644R Smart Temp Transmitter-Emerson.pdf

./O & M Manual.pdf.ditaLinks/3095 MV- Mass Flow Transmitter - Emerson.pdf

./O & M Manual.pdf.ditaLinks/ZR402G- O2 ANALYSER- YAKOGAWA.pdf

./O & M Manual.pdf.ditaLinks/3.2 HART PROTOCOL.pdf

./O & M Manual.pdf.ditaLinks/951R-95UV-95DC-S1-S2 FLAME SCANNER-FIREYE.pdf

./O & M Manual.pdf.ditaLinks/Pyro TC.pdf

./O & M Manual.pdf.ditaLinks/5.2 PNEUMATIC ACTUATOR - KELTRON.pdf


Section 07

7.1 Black & Bleed Valve- ELO Matic

O & M Manual

Manual —P Series

Manual

Drawing And Data Sheets

Drawing & Datasheets

7.2 Main Fuel Trip valve – Virgo

O & M Manual

Manual

Drawing

Drawings


./O & M Manual.pdf.ditaLinks/P & E SERIES- ACTUATOR-EL-O-MATIC.pdf

./O & M Manual.pdf.ditaLinks/P SERIES- Pneumatic Acturators - EL-O-MATIC.pdf

./O & M Manual.pdf.ditaLinks/Block & Bleed Valve - El-O-Matic.pdf

./O & M Manual.pdf.ditaLinks/Shut off Valve - Virgo.pdf

./O & M Manual.pdf.ditaLinks/Shutoff Valve - Virgo.pdf




♦ Section 01♦ Section 02



Section 01

SWAS Panel - Emerson

O & M Manual

Manual

Section 02

Gas Calori Meter – Chemtrol

O & M Manual

Service Manual

Instruction Manual

Gas Calculation Specification

Specification


./O & M Manual.pdf.ditaLinks/SWAS Manual - Emerson.pdf

./O & M Manual.pdf.ditaLinks/Instruction Manuel RHADOX 3000.pdf

./O & M Manual.pdf.ditaLinks/Instruction Manuel RHADOX 3000.pdf

./O & M Manual.pdf.ditaLinks/Cal.Gas Specification.pdf




♦ Section 01♦ Section 02♦ Section 03♦ Section 04



Section 01

Spring Hangers – Techno Industries

O & M Manual

Manual

Drawings

Drawing

Drawing

Section 02

Blow Down Valve - BHEL

O & M Manual

Manual

Section 03

Control Valve - Fisher

O & M Manual

657 — Manual

667 — Manual

95L— Manual

ET — Manual

EZ — Manual

ED — Manual

EWT — Manual

Drawings

Drawings

Data Sheets

Data Sheets

Curves

Flow Curves

Section 04

HP,LP & PH Dosing Pump - Metapow

O & M Manual

Manual

Drawings

HP Dosing Drawing

LP Dosing Drawing


./O & M Manual.pdf.ditaLinks/Veriable Support - Techno Indust.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Spring Hanger/Spring Hanger 1top mounted.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Spring Hanger/Spring Hanger 2 bottom mounted.pdf

./O & M Manual.pdf.ditaLinks/BB,BD,BM,BP SERIES- Blow Down Valve - BHEL.pdf

./O & M Manual.pdf.ditaLinks/657.pdf

./O & M Manual.pdf.ditaLinks/667.pdf

./O & M Manual.pdf.ditaLinks/PRV 95H FISHER.pdf

./O & M Manual.pdf.ditaLinks/ET & EAT_IOM.pdf

./O & M Manual.pdf.ditaLinks/EZ_IOM.pdf

./O & M Manual.pdf.ditaLinks/ED & EAD_IOM.pdf

./O & M Manual.pdf.ditaLinks/EZC ETC & EWTC.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Control Valve/CV Drawing - Fisher.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Control Valve/Data Sheets - Fisher.pdf

./U:/COMMSG/COMMNG/C-TYPE/Cairn Energy/ABORTEXT/Volume - 4/Control Valve/Flow Curves - Fisher.pdf

./O & M Manual.pdf.ditaLinks/Standard Manual of HP & LP Dosing - Metapow.pdf

./O & M Manual.pdf.ditaLinks/CAIRN ENERGY-HP.pdf

./O & M Manual.pdf.ditaLinks/CAIRN ENERGY-LP.pdf


PH Dosing Drawing


./O & M Manual.pdf.ditaLinks/CAIRN ENERGY-PH.pdf


Index

AAir and Flue Gas System .............................. 28Air Duct........................................................ 29Amine Dosing System (PH DosingSystem)...................................................... 19Attemperator ................................................ 16

BBoiler Annual Maintenance andOverhaul .................................................... 74Boiler Assembly............................................ 14Boiler Emergency Trip................................... 57Boiler Feedwater Control Station ................... 13Boiler Feedwater Pump................................. 12Boiler Hot Startup Pressure RaisingCurve ......................................................... 54Boiler Log Sheet ........................................... 58Boiler Operation ........................................... 57BOILER PRESERVATIONPROCEDURE............................................. 76Boiler Pressurization and Loading.................. 52Boiler Safety................................................. 60Boiler Shutdown ........................................... 56Boiler Shutdown During Sudden TubeFailure........................................................ 57Boiler Start Up and Shut Down ...................... 42Boiler Startup and Pressurizing...................... 48Boiler Warm Startup Pressure RaisingCurve ......................................................... 55Burner Front Piping....................................... 37Burner Management System ......................... 40Burner System ............................................. 32BURNER TECHNICAL DATA ........................ 38Burners.......................................................... 7

CCharging of Deaerator................................... 45Charging of Fuel (Associated Gas /Raageshwari Gas/Diesel Oil ), AutomizingSteam & Air Line......................................... 46Chemical Dosing & Sampling System ............ 18Components Description ............................... 32Continuous Blow Down ................................... 6Cooling Air For Peepholes............................. 32

DDeaerator..................................................... 10Description Of Dosing System Skid (Hp)......... 18Design Code .................................................. 3

Design Specifications...................................... 2Dissolved Gases .......................................... 99Dissolved Salts and Minerals......................... 98Do’s and Don’ts for Boiler Operation .............. 57Dosing System ............................................... 7

EEconomizer .................................................. 13Effects of Impurities ...................................... 99Emergency Procedures................................. 60Evaporating Heating Surface Area ................... 4

FFans .............................................................. 6FD Fan ........................................................ 28Feed & Boiler Water Conditioning ................ 101Filling Water in Deaerator & Boiler ................. 44First Burner Lightup Sequence With DieselOil.............................................................. 51First Burner Lightup Sequence With FuelGas............................................................ 50Flue Duct ..................................................... 31Fuel ............................................................... 4Fuel Analysis.................................................. 4Fuel Firing System........................................ 32Fuel Gas, Oil, Pilot Gas & Atomizing SupplyPipe to the Burner ....................................... 35

GGeneral Principal of Weld Repairs ................. 85

LLocal Burner Panel ....................................... 40Log Sheet for the Boiler ................................ 58

MMain Steam Line .......................................... 17Material Specifications of pressure parts .......... 4

OO2 Scavenging System (LP) ......................... 20Operational Control....................................... 18OPERATIONAL CONTROL........................... 41Operational Precautions for Safety................. 61Other Materials............................................. 99

121


PpH Value of theWater and its Importance......... 99Planned Shut Down ...................................... 56Preventive Maintenance................................ 69

RRecommended Maintenance Practices .......... 69

SSafety Valves ................................................. 6Sample System ............................................ 21Schedule of Inspections for ConditionBased Maintenance .................................... 69Section — C................................................. 42Section — D................................................. 69Section —B.................................................... 9Section Overview................................. 9, 42, 69Site Condition................................................. 6Startup of a Cold Boiler ................................. 42Steam Tempearture Control Loop .................. 16Superheater ................................................. 16System Line Up ............................................ 43

TTrouble Shooting Chart ................................. 64Tube Failures ............................................... 64Tube Thickness Survey................................. 75

UUndissolved and Suspended SolidMaterials .................................................... 98

VValve Positions Chart (Before Light Up).......... 22

WWater and Steam System.............................. 10Water Chemistry........................................... 98Water Quality Recommendations................... 67Welding Procedure Specifications(WPS) ........................................................ 76Windbox....................................................... 30

122

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