10. Power Plant Operation Vol-V

7/27/2019 10. Power Plant Operation Vol-V

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Power Plant Operation - (GF-4)

Contents

1.0 GENERAL PRINCIPLES OF POWER PLANT OPERATION 1-20

1.1 Introduction 1

1.2 Safety 1

1.3 Role of operation engineers 3

1.4 Unit operation 4

1.5 Some general operating instructions 14

1.6 Shift routine 182.0 OPERATION OF BOILER & AUXILIARIES. 2 1 -75

2.1 Line-up Boiler feed water system. 21

2.2 Line-up boiler water and steam system. 22

2.3 Boiler filling. 23

2.4 Draft system. 26

2.5 Fuel firing system 28

2.6 Boiler purging & lighting up 40

2.7 Boiler loading 45

2.8 Normal shut-down to cold 55

2.9 Auxiliary steam system 64

2.10 Routine checks 67

2.11 Emergency operations 69

3.0 OPERATION OF LMW TURBINE & AUXILIARIES. 77-106

3.1 Line up. 77

3.2 Starting of turbine from cold state 81

3.3 Rolling instructions 84

3.4 Loading the turbine 88

3.5 Warm and Hot start 91

3.6 Hot start 95

3.7 Planned shut down 99

3.8 Important instructions during turbine running 100


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3.9 Do's and Don'ts during turbine running 102

3.10 Emergencies in turbine and auxiliaries. 103

4.0 OPERATION OF KWU TURBINE & AUXILIARIES 107-1284.1 Line-up 107

4.2 Cold start up. 110

4.3 Loading the turbine. 117

4.4 Start up after 48 hours shut-down. 123

4.5 Start up after 8 hours shut-down. 124

4.6 Normal shut-down of turbine. 124

4.7 Emergency shut-down. 125

4.8 Do's & Don'ts for turbine operation. 1265.0 OPERATION OF GENERATOR & AUXILIARIES 129-148

5.1 Lining up the system 129

5.2 Pre-synchronising checks 132

5.3 Steps for generator synchronising 133

5.4 Routine operation and periodic checks 137

5.5 Operational limits of 210 MW Generator 142

5.6 Emergency operation 145

Note:

For schemes of various systems, whose operating procedures are described in this chapter,please refer "Thermal Schematic Diagrams (210 MW)" published by Power Engineers TrainingSociety.


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GENERAL PRINCIPLES OFPOWER PLANT OPERATION


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1. GENERAL PRINCIPLES OFPOWER PLANT OPERATION

1.1 INTRODUCTION

Operating procedures vary with unit size, design, system requirement etc. This volumedescribes operating procedure of thermal units, having BHEL Boiler and210 MW BHEL-LMW/500MWBHEL-KWU turbo-generator. However, certain steps or procedures are common with almost every typeof boiler, turbine and generator. They, with the logics behind them, have been explained in the beginningof this volume before proceeding to the operating details of 210 MW/ 500 MW units . But this volume is

meant for training only and hence should never be considered as on Operation Manual for 210 MW /500 MW units .

1.2 SAFETY

Operation Engineers should

Ensure safe working condition.

Use himself and provide other necessary protective equipment to operating staff.

Assign employees the jobs which they are capable of doing safely.

Study and understand the safety procedures mentioned in operation manual and other relevantdocuments.

Take immediate steps to correct any violation of safety rules.

Investigate every accident and report to the concerned authorities.

Be familiar with relevant safety regulations like Factories Act, Boilers Act etc.

Ensure the provision of first aid box in the work place and should themselves know how to givefirst aid.

Permit to work system

Operation of thermal power plants involve dealing with vessels and pipes carrying Quids of hightemperature and pressure, hazardous chemicals, electricity of different voltage levels, rotating equip-ments etc. Therefore, a well planned permit to work (PTW) system must be followed strictly to ensure safetyduring work on any equipment or system (A typical PTW form has been reproduced in page 2)

It must be noted that

All equipments, in service or available, are under the custody of operation section.

Maintenance section has to request in writing the operation section for clearance to work on anyequipment or system.

Operation section must isolate the equipment and place proper tags so that the workmen arenot exposed to any hazard.


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Book No.

Unit No. II III IV

I hereby declare that all menand materials under my chargehave cleared the site, equipment/ pipe line and men have beenwarned that it is no longer safe towork on the equipment specified

, on this card.

Nature of defect noticeto

Details of work done

Time

Date

Name

Designation

Signature

A Typical PTW

....Thermal Power StationExpected time

of return Hrs. Day Permit No.

B. D. P.M. OPP.Type of Maintenance

I hereby declare that the following equipments are isolatedand safe to work. Caution notice have been affixed to all

Controlling valves or Electrical switches.EquipmentIsolations Made

Issued by

Issued to

Cancelled by

Name Desig Date Time Sign

Trial RunCarried

Yes No Date Time

Representative of Maintenance

Name ...

Designation

Signature

Representative of Operation

Name

Signature of

Controller

Thermal Power Station

BREAK DOWN INTIMATION SLIP

Book No Permit No

Unit No. I II III rv V s

Name of the equipment

Type of defect.

EquipmentStopped

Vltc Section incharge

Date Time

BLR TUR MISC C&I EDI E.D.D

Time.

)ate

fame

ignature of Controoler

hift Charge Engineer ..


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It is the responsibility of the operation section to deliver the equipment to the maintenancesection in such a condition that no hazard is faced by the work men during work.Before issuing any PTW the operation engineer should ensure that the persons collecting/ requesting PTW are fully familiar with the job and understand the associated systems, if any.

All PTWs must be issued in writing in prescribed forms and all copies of PTW must be signed bothat receipt and at clearance.

PTWs should be issued between specified hour only.

Before receiving back any PTW, the operation engineer must ensure personally that the job hasbeen carried out as schedule and there is no danger in charging the equipment/system.

Fire Protection

The operation engineer must be familiar that the fire prevention and protection systemsprovided in the plant.

Should know his responsibility clearly if a fire breaks out.

Should be able to lead the other operating staff in fire fighting operation till the fire brigade orothers concerned take over.

House Keeping

Operating engineers should :

Be Aware of the importance of cleanliness and proper house keeping inside the plant

Ensure all floors, steps, stairs, passages are kept free from any obstruction and foreignsubstances likely to cause a person to slip.

Ensure that no combustible or hazardous material is lying unattended in the plant.

Ensure that the fire fighting equipment and emergency exits are conspicuously marked and arenot obstructed by anything.

Ensure that adequate lighting has been provided in the work areas.

1.3 ROLE OP OPERATION ENGINEER IN THERMAL POWER STATION

The operation engineer is meant to ensure :Safety of equipment and personnel

Reliability of supply, and

Generation of energy at economic cost.

His responsibility is to :

Start up the equipment in a safe and systematic manner.

Connect the unit to the transmission network in a proper manner so that the consumer can drawpower.

Watch the equipment to ensure its run under safe working conditions.


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Adjust the different control inputs, like fuel, air, water makeup to match the electrical outputof the unit.

Maintain proper cooling of the different teeajing surfaces, by assur ing lubrication and heatdissipation by cooling.

Maintain salient levels in the different subsystems.

Maintain the specified pressure and temperature and levels at various points. Normally,automatic devices are provided but the operation engineers should be able to intervene andmodulate the control to maintain the parameters within the specified limits.

Maintain proper chemical conditions and concentrations.

Watch the mechanical behaviors of all moving equipment-noise, vibration, bearing lubrication,

cooling, control valves and dampers etc.

1.4 UNIT OPERATION

Unit system is the trend of the day. An unit consists of a boiler, a turbine (single or multicylinder)and a generator coupled with turbine along with their auxiliaries and subsystems. The unit is, infact, aself contained power station in its own right, and on load producesthepoweito drive its own auxiliariesvia its unit transformed.

The main functions of unit operation are :

i) Starting and loading

ii) On load activityiii) Off loading and shut down.

Operating procedures vary from unit to unit due to differences in unit si?es, design criteria,auxiliary systems, manufacturer etc. Still there are some common basic steps which are to be followedsystematically to ensure smooth operation of any unit.

1.4.1 Unit Start Up and Loading

STAGE-1 : Preparation (Pre-start checks, ensuring availability of fuel andother essential services)

STAGE-2 : Pressure raising on boiler

STAGE-3 : Putting turbine on barring gear

STAGE-4 : Steam admission to turbine and running it to speed

STAGE-5 : Synchronising and loading.

14.1.1 STAGE-1

Preparation for unit operation involve the following :

i) Checking supplies

ii) Checking availability of services,

iii) Investigation of Permit to work (PTW) system.


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The supplies include :

Fuel (coal & Oil)

Cooling water

Service water

DM water

Chemicals for water treatment plant

Lubricating oils and greases

CO2, Hydrogen

The Services include :

Electric supply availability

Water treatment plant availability

Compressed air (or Instrument air) availability

Ash and dust disposal system availability

Fire Fighting system availability

Coal Handling Plant availability.

Investigation of PTW involves :

Investigation of permits issued and returned

Identifying the plants and systems disturbed during maintenance,this will enable the operationstaff to exercise special care when recommissioning such items.

1.4.1.2 STAGE-2

Pressure raising on boilers CAchJevf .?iri\iog steam |j*an>QW*? 35-5ovw-

Pressure raising on boiler involves the following activities in boiler and turbine sides. Before engaging intothe activities mentioned below it is necessary that pre-start inspection and check has been carried outin each equipment and system. For example :

Sensors, gauges, recorders correctly set up for monitoring

All boiler access and inspection doors shut C fosznWdet \x> be.'&uibad.)

All soot blowers fully retracted

Ash hoppers door shut, ash hopper seal full

No obstruction to free boiler expansion

6>Precipitator inspected and ready

Draft system (ID, FD fans, dampers) thoroughly checked

Pre-start checks carried out for ID, FD fans, feed pumps, chemical dosing, pumps, mills, airheater etc. ^


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Boiler Activities

Fill boiler and obtain drum level indication

Charge boiler ring main. 2 comer burners" cracked on recirculation

Start both APH (air pre-heaters)

Start ID fan

Start FD fan with 30% air flow

Complete PURGING of the boiler

Light the boiler with oil burners and establish circulation.

(Recently, in some boilers arrangement has been made for direct firing of coal. In these boilersoil burners have been replaced by special coal-ignition burners)

Regulate firing, drains and vents for metal temperature control and raise pressure

IF HP/LP Bypass is available take it into system. This will ease reheater metal temperaturecontrol. At high pressure main p.f. burner may also taken into service.

Monitor water/steam quality and act according to chemists'instructions

Turbine Activities

Establish CW flow though condenser.

Fill hot well, start extraction pumpFill Peaerator

Prime and start standby feed pump

Prime HP feed system

It may be noted that the some activities mentioned above can be performed simultaneously(parallel), some one after another. Fig. 1.1 shows the PERT Network of pressure raising activities.

1.4.1.3 STAGE-3

Putting Turbine on Barring Gear

i) Turbine oil systemii) Aux CW system

iii) Generator system

Turbine Oil System

Turbine main oil tank has enough oil and high and low level alarms are working

Commission oil purifier, check oil flow through sight glasses

Check pump automatic start-up sequence


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FIG 1.1 STAGE 2 RAISING BOILER PRESSUREPERT NETWORK


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Start jacking oil pump and AC flushing pumpStart the exhauster fans

Auxiliaries CW System

Aux. CW pump run upPriming aux CW system(This system includes cooling water for pumps' bearings oils and other coolers)

Generator Systems

Commissioning seal oil system

Run AC seal oil pump. Control seal oil pressure manually.Inspect seal oil return sight glasses. Excessive or very low oil flow shows seal malfunctioning.Wait till turbine is put on barring gear for some time allowing the seals to re-align.

Gassing up

Replace air with CO 2Admit Hj till 25% purity is obtainedRaise gas pressure to designed value %Gassing up operation take long hours (5-6 hours). So may also be done after putting the turbineon barring gear

Observe safety regulation strictly during Gassing /Degassing procedure.Commissioning stator water system

Run stator water pump intermittently and vent after each run. The system thus is primed andpressurisedCheck leakages in the system and monitor pressure differential across stator inlet and outlet

Monitor water quality (mainly conductivity)

Putting turbine on barring gear

Lubrication oil pressure should be satisfactoryJacking oil pressure should be satisfactoryEngage barring gear with the main turbine shaftStart barring motor/Admit pressurised oil to gear turning mechanismFig. 1.2 shows the PERT network for commissioning barring gear.

1.4.1.4 STAGE-4

Steam admission to turbine and running it to rated speed.

Ensure that pre-start check has been carried out on :-

Turbine valves and lines for steam admission.

Gland packing and vacuum system

Exhausthood spray and flange heating sperm

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Cooling water culvera check __ / ^ ) Am ..cooling system check

Cooling witw pumps priming check i

Aux. cootiiig pump chock Slan aux. cooling pump Pnme aux. cooling system Prime condenser; _, ->

Stator coolani system check

Pnme stator cooling system _ Stator coolant systemSeal oil system in service y^ . Gas-up

Turt>m* lubricating oil system check

pit punfier m service OOI pumps stan A auto operation check ^^-^urbme lub oil system in s Turbo-alternator tuming gea/ 1-5

FIG. 1.2 STAGE 3 UNIT RUN-UP COMMISSIONING TURNING GEARPERT-NETWORK

Hydrogen cooling system and stator cooling system can be commissioned with turbine on or off turning gear.

The hydrogen cooling system must be commissioned prior to commissioning stator water system.

Condenser priming is not mandatory prior to tuming gear operation. It is desirable in many cases in order to check deflection.

Seal oil must be applied to seals for lubrication purposes prior to commissioning turning gear.


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L.P. feed systemTurbine protection devices

ACTIVITIES ARE AS FOLLOWS ;

Testing of Steam ValvesEmergency stop valves (ESV) of HP and IPT cylinders are to be open and their closure should bechecked by hand trip. This is most important for protection of plant and personnel.

Drainage regulation

On many modern installations main and reheater drains are thermostatically controlled andclose automatically when the desired temperature is achieved. In manual operation usually thedrains are not shut until a substantial flow is passing through the associated pipe work.Substantial quantit ies of valuable water and heat will be lost due to prolonged drainage. Generalprocedure is to close the leg drains when temperature in legs is 50C above saturatiqntemperature at that pressure. Note that reheat steam drain must be routed to condenser flashbox if vacuum raising process has already been started.

Vacuum raising and gland steam system

Methods of applying gland steam and raising vacuum vary according to size, manufacturer etc.Sequences could be :

Seal glands and then raise vacuum, or

Raise vacuum to a certain value and then apply gland steam, or

Apply gland steam and commission vacuum raising equipment simultaneously.

Warming

The turbine is to be warmed before it can be run up to rated speed. Warming is done by admittingsteam in the turbine. The quality and quantity of steam depends on the size of the machine andon temperature difference between the machine metals and the steam. The mass of metal inturbine rotor is less that of stator (or cylinder as commonly called). So, when steam is admittedin the turbine the rotor absorbs heat faster and expands^faster than the cylinder. The differencein expansion between rotor and cylinder is termed as differential (expansion) and should be nearzero to maintain axial clearance of blades and glands.

To achieve this the turbine is heated slowly and uniformly. Apart from limiting differential ex-pansion it also reduces chance of high stress and distortion.In order to heat the machine uniformly the temperature and quantity of steam must be raiseduniformly at a rate suggested by the manufacturer.

Also to reduce the amount of differential expansion and the stresses imposed on bolts andflanges, the flange heating system is provided. The methods of applying flange heating steammay vary to suit individual design. On some machines, flange heating is used as a precise formof control, more or less steam is being admitted to the flange as required. In others, manufac-turers recommend that the flange heating steam Is to be applied at the commencement of therun-up and remains on until the turbine has been carrying a substantial load for some time.

Rolling

Of various methods of turbine rolling, the two common methods are as following :

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Soaking method

In this method, the machine is given a soaking time just before the critical speeds. In a typicalexample, the turbine is rolled to 5Q0 rpga. and held at this speed for 15 minutes. Again at 2000rpm. the machine is held for 45 minuets and then at 3000 rpm. a soaking time of 30jninutesis given.

Constant acceleration method

The machine is rolled and speed is increased at a constant rate (i.e. constant acceleration) from0 to 3000 rpm. The acceleration rate should be as per manufacturers guidance.

With modern throttled governed turbines a combination of above two methods are also used.

During the entire rolling period the turbovisory equipments should be carefully monitored.Turbovisory equipments are :

1 < Diffential expansion detector

I , Eccentricity recorder

j . Total expansion recorder

/f t Tachometer

r Vibration recorder.

Overspeed Bolt Testing

Before synchornising the unit it is necessary to prove that overspeed bolts operates, if :

The bolts have been adjusted

The u,nit was under prolonged shut down

The legal period between testings has elapsed.

The start up activities so far described is cold start-up . The other type of star ts are warm start up and hotstart up. This catagorisation depends on the metal temperature of HP Turbine casing in the regulatingzone.

Metal temperature above 350G . - Hot start

Metal temperature between 150-350C - Warm star t

Metal temperature below 150C - Cold startWarm or hot start of the machine is required when the unit is stopped for few hours. But with the adventof two shifting operations hot start up of the machine may become a routine affair. Most important thingin_vvarm/hot start up is to match the steamtemperature with that of H.P. cylinder before steam admissionto turbine.

Loading

Loading of turbo-generator (TG) from zero to full load during cold start up involves many operations andkeeping constant watch on the supervisory conditions like :

/ Differential expansions of all cylinders

I. Axial shift

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3. Metal temperature

4- Vibration

$ Electrical parameters etc.

The TG should be loaded as prescribed by the manufacturer, For a 210 MW set (LMW - Soviet design) ittakes around 6 hours to attain full load.

The major operations during loading are :

f Charging LP and HP heaters


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After the unit has been tripped SH start/up vent is to_t>e_Qpengd.. Vents of SH and Drum is tobe opened when pressure is very low (around 2 kg/cm 2). Boiler must be purgedjor at 5 minutes with 30%air flow. Afterwards ID and FP fans may be stopped and dampers closed. Drum level should bemaintained. If the shut down is for a longer period boiler may be emptied of water and proper action forpreservation must be taken.

1.4 .3. 2 EMERGENCY SHUT DOWN

Emergency shut down can be of various types due to different reasons. A healthy unit may beinstantenously out of the grid due to system trouble, or it may be due to some serious problem of someequipment of the unit itself. Depending on the nature of emergency the shutting down procedure of theunit is to be decided. This will be discussed in details in later chapters.

1.5 SOME GENERAL OPERATING INSTRUCTIONS

Operating engineer and his team have to be fully familar with the details of the system, the designlimits, the sequence of operation, the interdependance of equipments, unsafe conditions of operation and

seriousness of each malfunction. One must know WHY he is carrying out certain operations and itsimplication on the system as a whole; Following are some important operations and the logics behindthem.

1.5.1 Air Vents

Air vents are provided to boiler, heating surfaces, heat exchangers, main steam lines etc. Theproper operation of these vents is essential to prevent any emergency situation later on. For example,precaution must be taken to expel all the air from boiler tubes while boilerfilling. For this purpose all theair vents are kept open and boiler filling rate is kept slow. If the air pockets are left in the system then itcan cause hindrance to fluid flow, and overheating of boiler tube causing their failure. Care also must betaken while depressurising. The air vents must be opened as the pressure approaches atmospheric air.

1.5.2 Charging and PillingThe operations of charging and filling are much the same regardless of the application. The

procedure normally followed is :

Open the air vents

Open the drain valves

Start the pump (if the pumps is already is service, open the filling/charging line valve as follows):

Crack open pumps discharge or filling valve until a satisfactory charging flow is obtained (thisis usually detected by the sound of the flow through the partially opened valve)

Check that the drain is free from any obstruction and close it

Expell the air and close the air vent after a steady flow of water has been obtained from it

While charging, care should be taken to avoid any water hammer

The air must be expelled gradually and completely. To ensure this the rate of charging shouldbe slow, this will also avoid overloading of fill pump. The slow charging is also essential to avoidthermal stre ss where there are temperature differences between the water and the item beingfilled.

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1.5.3 Warming

Warming differs from charging is that the admission of warm steam resul ts in the production of large quantities of condensate arising from the warming process. This condensate must be drained awaybefore the lower portion of the pipe can be warmed. Precaution also must be taken to carry out thisoperation slowly to prevent large thermal stresses.

1.5.4 Drain Valve Operation

Due to the tremendous amount of damage which can be caused by maloperation, it is importantto know the correct sequence in which drain valves must be operated. Almost invariably drain valves arefitted in pairs, two valves in series on the same drain line. The upstream valve (valve nearest to source of pressure) is isolating valve and its companion is the regulating valve. Drain lines should be warmed up

judiciously, avoiding sudden admission of steam or hot fluids which could result in large temperaturegradients in the drain lines and possible 'hammer' or thermal shock.

To avoid this , charging up should be slow, throttling the flow of steam or fluid by restricting valveopening. This introduces another problem; as the passage of steam or fluid through the restricted valveopening creates a phenomenon known as 'wire, the valve becomes damaged. To prevent this, the valveoperation sequence must be as follows : (Refer fig. 1.4).

SOURCE OF PRESSURE Regulating ""** v Isolating valve Valve

-& &* iii N n C H A R G E D c 0 L D LINEy?Q$ uirvv WHICH IS TO BEFIRST VALVE WARMED SLOWLY

FIG. 1 +

To charge drain line :

Crack open isolating valve. The small length of drain line between the two valves will bepressurised almost immediately. Wire drawing is virtually nil.

Open isolating valve fully

Crack open regulating valve. This valve is subject to wire drawing. Charge drain lineslowly. Regulate as required using regulating valve only.

To shut off drainage :

Close the regulating valve. Wire drawing takes place as the regulating valve throttles theflow.

Close the isolating valve. Flow is already zero. So on wire drawing takes place.

Crack open the regulating valve to release the pressure trapped between the valves.

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As mentioned, the damage due to wire drawing is inevitable but, at least, by using correctoperation techniques we can restrict the damage to regulating valve only. This means that we canreasonably expect the isolating valve to give tight isolation when closed, thus preventing losses viapassing drains.

1.5.5 Drum Metal Differential

The boiler drums are filled withwater in the bottom and steam in the top dueto which the cooling and heating rates varybetween the top and the bottom. This re-sults in temperature differences betweenthe top and the bottom. Stress analysesshow that the principal criterion for reliablerates of heating and cooling should be basedon the relationship between the tempera-ture differential through the drum wall andthe temperature differential between the topand the bottom of the drum, both measuredis same circumferential plan. Stress analy-sis also shows that the allowable tempera-ture differentials are based on tensilestrength, drum diameter, wall thickness,and pressure; therefore, each steam drumhas its own allowable temperature differen-tial curves, one set for cooling and one set for

heating. To keep the thermal stress valueswithin the limit, operation engineer mustensure that under all operating conditionsactual temperature differential is below theallowable temperature differential. Normallythe temperature differential should not exceed50C (see fig. 1.5).

70 Ho Jo " fi . . DRUM PRESSURE KO/C m* /

FIG. 1.5 DRUM TEMP. DIFFERENTAL LIMITS

1.5.6 Drum Gauge Glasses

Normally two gauge glasses (sometimes three) are 1 provided to boiler drum . It m us t be ensur ed

prior to light up that gauge glasses are available for service and are in charged condition - especially,during cold start. The remote indication is availablejibove J LO_kg/cm?_drum. pressure . Dur ing light upoperation there are large drum level fluctuations. At about 5^ to 10 kg/cm 2 thejgauge g l ^ ^J id t l ff d b l k i h

j g g g ^ ^J side to clear off any; dirt blocking the port. As per IBFLboiler must riot be

operated with all the gauge glasses provided out of servipe.

1.5.7 SCAPH - Operation

While lighting up the boiler from cold state, since most of the furnace is relatively cool, largeamount of heat is absorbed in the furnace. This reduces the temperature of flue gas leaving the boiler. Thefuel oil which is fired for light up has 1.5 to 3.5% sulphur depending upon the quality. This sulphur formsSO 2 /S0 3 after combustion and combines with HjO to form highly corrosive sulfuric acid when tempera-

ture of flue gas is low during lighting up the boiler from cold state. Due to large percentage of sulphur in

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oil, special care must be taken when oil is being fired. The sulfur ic acid thus formed corrodes air heaterand sometimes economiser tubes also. To prevent this cold ^Lnd corrosion, heat transfer in air heater isminimized by raising the temperature of air going to air heater. This is done by putting Steam Coil Air PreHeater (SCPAH) at thedischarge of F. D. Fan. Steam is passed through SCAPH when heavy oil is being firedwhich raises the temperature of airgoing to air heater and flue gas temperature in air heater remain high.When boiler gets sufficiently warm up, the flue gas temperature the exit of air heater starts increasing,then gradually steam supply to SCAPH is cut off keeping watch on air heater gas exit temperature.

1.5.8 Boiler Expansion Measurement

Normally for all utility boilers (i.e. power station boilers) the entire boiler, casing and insulationare suspended from top. The provision for free expansion for all parts of the boiler is important but in thecase of furnace tubes it is vital. Since the boiler is suspended from the boiler house steel work, theexpansion is mostly in downward direction. On a typical 500 MW boiler, the total expansion from cold tolull load can be as high as 340 mm. Expansions, in other directions are also significant of the order of 70 .to 80 mm. The boiler must be allowed to expand freely in all directions. Scales are provided at differentelevations to measure the expansions. Readings must be taken and free expansion must be ensured. Thisis very important especially when the boiler is being taken into service after major shut down because itis likely that during shut down some temporary piping, scaffolingwere welded with the boiler structure.

1.5.9 Economiser Recirculation Valve

During pressure raising period, very little amount of water passes through the economiser andthere is a danger of the economiser overheating, and in extreme cases, vapour locking. To prevent thiscondition the economiser recalculation valve is kept open during the pressure raising period. Therecalculation in economiser takes place in similar manner as in water wall tubes. Once a steady flow is

established to the drum, economies recirculation valve can be closed.1.5.10 Barring Gear

When shutting down hot machine or before turbine start up, the turbine must be on barringgear. When a turbine is shut down, due to its heavy weight, high temperature and uneven cooling theturbine rotor will have permanent deformation (hogging/bending). So the main function of the barringgear is to promote even cooling of the rotors, and cylinders when turbine is shut down. The barring gearis engaged immediately after turbine becomes stand still or at 250/500 r.p.m. for 500/210 MW KWU sets.The barring speed is usually low.(3 to 4 r.p.iru) for LMW sets but high speed barring gear (about 200 r.p.m.)are provided in KWU_set&, The provisions of high speed barring gear enables to bring the turbine off barring gear with minimum steam admission while rolling the turbine.

1.5.11 Soaking of Turbine

Depending upon the type of the start up (cold, warm, hot), turbine is soaked at some particularrpm. for predetermined time interval. During soaking period turbine speed is held constant and steamparameters kept steady. Care should be taken to see that soaking speed is not near critical speed (Turbinemanufacturer's recommendations to be followed). Soaking helps in bringing differential expansionswithin limits, also the operator gets sufficient time to check up other turbovisory parameters like turbineexpansion, turbine vibrations, bearing drain oil temp, drain oil flow etc. After satisfying himself of healthiness of turbine he can proceed for further rolling of turbine. The soaking time is more for cold startcompared to warm and hot start.

1.5.12 Critical Speed

When shaft or rotor, revolving in bearings, speeds up to where centrifugal force tending to whip17


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it sideways just balances the elastic stiffness tending to keep it straight, the slightest mechanicalunbalance builds up a whirling motion whicrftnay be of destiUctive amplitude. The rotor then is revolvingat critical speed. This phenomenon is due * the resonance frequency when the rotation speedcorresponds to the natura l frequencies of lateral vibration of the rotor. It is inadvisable to run any rotorat or near critical speed for any length of time regardless of perfection of balance. The operation engineermust be well aware of exact critical speeds of the turbine. Care must be taken NOT to hold the turbinespeed nearby critical speed value and the speed rise should be kept uniform without any interruption.

1.5.13 Use of Common Auxiliaries

In a power station consisting of number of units, there are many auxiliaries common to all theunits. So for the operation engineer it is essential to know how the adjacent units will be affected by hisoperation. For example, aux. steam supply, fuel oil supply, compressed air supply, cooling water supply,

reserve power supply etc. are common for all the units. Now if a unit is to be started, before charging, say,aux. steam header from adjacent unit they should be informed about this so that in case of any problemit can be immediately sorted out without creating any emergency. If not given prior notice, the unitcontroller of adjacent unit will have less time to correct the fault developed and this can endanger theoperation of his unit. To prevent such mishaps proper communication must be maintained between theunits especially while using common auxiliaries.

1.5.14 Proper Use of Instruments

As the unit sizes are going on increasing, more and more operation is carried out from remote.For an operator in UCB, therefore it is very important to have correct knowledge of system parameters.For this purpose there are large numbers of meters, graphs and other instruments provided in UCB.

For one parameter there could be more than one instruments available in UCB (e.g. drum level,steam temp, furnace draft etc.) The operator should see that the readings in such instruments arematching within reasonable limits. In case of any discrepancy^the operator should not take convenientcorrect reading for granted, instead should believe the worst reading as correct one and investigate thematter. If the result of such investigation proves that there is fault in the instrument, then it should berectified from maintenance department immediately. For other parameters also (where only oneinstrument is provided in UCB for indication) in case of any deviation from standard value, the mattermust be investigated and instrument fault must be attended.

1.6 SHIFT ROUTINE

1.6.1 Major observations

Following are some major observations/checks to be made at intervals within each shift and atthe commencement of each shift.

1.6.1.1 MAIN A.C. CIRCUITS :

Note the position of:

220 KV/400 KV bus bar distribution, distribution of feeders, generator and stationtransformers etc.

ii) Auxiliary supply position. The position of interconnectors of H.T. and L.T. supply,

iii) Note whether the unit is on station or unit supply for HT and LT systems.

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1.6.1.2 BOILER FEED SYSTEM

Note the feed pu mp s on load and If the stan dby p um ps are available. Observe whether they areselected to auto or manual.

i) Dr um level control - is it on au to or ma nu al ,

ii) Which feed line is charged and the position of sta ndby feed line

iii) Note the availability and condition of stan dby cond ensa te extraction pu mp.

1.6.1.3. TANK LEVELS :

i) Inspect all tank levels. C P **~v,, nemj&e& , Oe*\*S uki>*-w*M-;

ii) Check also the levels for F.O. ta nks, D.M. make up water ta nk s etc.

1.6.1.4 MILLS :

Examine mill system :

i) Chec k which mill sys tems are on load an d the position of sta ndb y milling sys tems.

ii) Note mill temp era ture and see whethe r controls are on aut o or man ual .

iii) Exa min e P.A. fan differentials and see whe ther they are on au to or manu al .

iv) Check R.C. feeder controllers - see wheth er on au to or man ual .

1.6.1.5 COMBUSTION CONTROL

i) Check wheth er furnace draft is on au to or manu al,

ii) Check whet her oxygen control is on au to or man ua l,

iii) Check furnace draft reading.

1.6.1.6 TURBOGENERATOR

Note :

i) Which eject or/air pu mp s is in service and the position of standb y pu mps ,

ii) Ext rac tion pu mp on load an d position of standby.

iii) Lub . Oil Syste m.

a) Auxiliary oil pu mp )

b) D.C. Emergency oil pum p. ) Auto or ma nu al selection.

c) Tu rn ing gear oil pu mp (if provided) )

iv) Availability of A.C. an d D.C. seal oil pu mp and au to manual selection,

v) Stat or water pum p in service and position of stand by pum p.

vi) Gen era tor trans forme r oil pu mp an d intercooler water pu mp on load and whetherstandby available and auto/manual selection.

The reason why any plant Is not on auto should be determined.

1.6.1.7 EFFICIENCY CONTROL

Particular attention should be given to following items to monitor efficiency.

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i) Ensure that all parameters are at their specified values. Load in particular must not belower than suggested by grid control.

ii) Examine milling and combustion. Ensure tha t they are in good order.

ill) Examine D.M. water consumption.

iv) Check total auxiliary power consumption.

v) Check condenser vacuum.

1.6.1.8 STATUTORY REQUIREMENTS:

i) Check stat ic condition for grit emission and smoke density. (Where these are continu-

ously monitored and each fitted with alarms, this problem is eased).

ii) Check C.W. condit ions to ensure that statutory limits are being observed.

1.6.1.9 MISCELLANEOUS:

i) Check all bearing and glands for any of abnormality.

ii) Check oil level of bearing. See whether oil is clean; if in doubt changeiii) Inspect for fresh oil leaks. This will be easy if the plant is clean and almost impossible

if it is dirty.iv) Check transformer oil levels.

v) Check fire fighting equipments.

vi) Check state of charge of station batteries (quick/trickle)vii) Check state of lighting - particularly emergency lighting.

viii) Attend to steam, water and coal leaks wherever possible.1.6.2 Shift Change Over :

It is observed that large number of mishaps in power station operation take place at the time of shift change over. This shift change over period is such that operator tends to take things easyafter days work-out or he is busy in writing log book. So, there are chances that he may overlook certain operational parameter going"astray. Similarly when some operator takes over the charge,then~~he is busy~ln~reading tne logboolTof previous shift. He also may ovejjcok__thejaultyparameter. Under such_circumstances emergency situation can arise. It is important for

operattorTstaff, therefore, to take care for avoiding such situation. The logging of each eventhould be done immediately after it occurs with all the details including the remedial actiontaken. The logging should be systematic. At the time of charge hand over, the incoming operatorshould be briefed about various important operations in the shift, especially if any abnormalsituations had been handled. The problem areas that can endanger unit working or can causeload reduction must be briefed to incoming operator. The status of standby auxiliaries must bementioned in the logbook. This systematic approach taken while shift change over can,therefore, help in performing safely.

At the same time during the shift also the operator has to be vigilant, so that the unit generationis kept at optimum level. Here, also, the systematic approach can be very productive.

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OPERATION OF BOILER & AUXILIARIES


25/133

2. OPERATION OF BOILER & AUXILIARIES2.1 LINE-UP BOILER FEED WATER SYSTEM

Closevalves

Closevalves

Boiler Feed Pumps discharge

Boiler feed pumps, dischargebypass valves

Close B.F. Pumps discharge headerdrain valve

Close

Open

Open

Close

Close

Open

Open

f

feed water isolating valves

ifeed line vent valve

1feed line drain valves

t

H.P. heater F.W. inlet valve

t

H.P. heaters F.W. outlet valve

f

H.P. heater F.W. bypass valve

1"F.W. line drain valves

f

Close S.H. & R.H. Attemperator headerisolating valve

Close

% f

R.H. spray block isolating valve

iClose S.H. Attemperator Control valvesinlet isolating valves

Close R.H. Attemperat-ior control valves'inlet isolating valves

Open feed line vent valve

Close Main Feed Control valve

1Close isolating valves

Close Standby Feed Control valve andisolating valves

Close bypass valves of Standby Con-trol valves' isolating valves

Close Low Load Control valve andisolating valves

Close bypass valves of isolating valvesof low load control valves

Open Feed Control station drain valves

Close boiler filling isolating valves fromBoiler Fill pumps

Close Hydrazine sampling valves' be-fore economiser.

Close economiser drain valve to waterwall header

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2.2 LINE-UP BOILER WATER & STEAM SYSTEM

2.2.1 Economlser

Open economiser inlet valve & closeits bypass valve

iOpen economiser recirculation valves

\ t

Close economiser drain valves

iOpen economiser outlet lines ventvalves

I Close economiser outlet lines drainvalves

2.2.2 Drum

Open Drum vent valves

t

Close C.B.D. Isolating valve

t

Close Phosphate dosing isolating valves

iCheck I.B.D. valves are closed.

r

Open Drum level gauge glass (Left andright) isolating valves quick closing

valves.1

Close Drum level gauge glass drainvalves.

'

Open isolating valves for local pres-sure gauge, level & pressure transduc-ers.

s r

Open isolating valves for remote drumlevel-indicator.

Close remote level indicator gauge glassdrain valves

Open saturated steam sampling branchline valves

Check that Drum safety valves are inservice condition.

2.2 .3 W.W. Drain Header

Close filling valve from Boiler fill pumps

Open S.H. headers & link vent valves

lOpen startup vent valves isolatingvalves

Open startup vent regulating valves

Open impulse safety valve isolatingvalve

Establish electric supply to impulsesafety valve.

Check that final S.H. header safety

valves are in service

Close M.S. shut-off valves & their bypassvalves

Open M.S. drain valves to before boilerStop valves

22

Close Scot Blower steam isolating valvesOpen isolating valves of local pressuregauges, pressure transducers etc.


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2.2.4 Reheater

Open Reheater headers vent valves

Open H.R.S. header motorised ventvalves

Close Sampling line valve

Check that R.H. header safety valveare in service.

Open R.H. desuperheater left & Rightdrain valves

Close R.H. spray line drain valve &after spray control valves.

2.2.5 C.B.D. Tank

A .Close C.B.D. tank vent valve to deaera-tor

Open the isolating valves, Flash tank level control valve

Open isolating valves of main C.control valve

r

Close C.B.D. control valve

f

B.D.

Close isolating and control valves of standby line

< t

Open C.B.D. tank atmosphericvalve

Check C.B.D. tank safety valveservice

vent

is in

Close the isolating valves tank control standby valve

r

Close standby C.B.D. tank leveltrol valve

PutCmode

r

B.D. level Control valve forof operation.

level

Con-

auto

2.3 BOILER FILLING

2.3.1 Boiler Filling Using B.F.P.

Fill the Deaerator with D.M. water usingboiler fill pump

Prepare Hydrazine & Ammonia solu-tion in the L.P. Dozing mixing tank

Take water in L.P. dosing meteringtank

Open Hydrazine dosing valve in B.F.suction line & run Hydrazine dosingpump.

Turn on feed waterheating steam & Oheat up the feed water gradually to80 to 85C.

Maintain deaeratorpr. just aboveatmospheric = 0.2to kg/cm 2 (g)

Run Boiler Feed Pump on recircula-tion

Continue to run B.F.P. on recircula-tion with Hydrazine amonia dosing

23


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Check water conditionbefore filling: should bepH 8.5 to 9.5 at 25C.Dissolved O 2 0.005ppm. Temperature 80to 85C. Hydrazine inF.W. 0.05 to 0.1 ppm

Ammonia contentshould be 0.2 to0.3 ppm.

Check F.W. system islined up

Refer feed watersystem line up

Crack open BFP discharge valve by-pass valve and slowly charge the FWlines

Throttle vent valves, as the air is beingreleased

Close Feed line drain valves

Close F.W. line drain valves after H.P.heater after flushing for few minutes.

Close the feed line vent valves beforeH.P. heaters when water starts comingthrough vent

Close the feed line vent valves beforefeed station when water starts comingthrough vent

Open bypass valves of feed controlvalves isolating valves.

Open low load feed control valves andcharge the line upto economisef .

Open isolating valves of low load con-trol valves.

Close economiser vent valves whenwater starts coming through it

r

Feed water linescharged

Open BFP discharge valve & close itsbypass valve

r

Maintain moderate

feeding about40 t/hr, for easy -\ purging ofair &gradual heating of drum & W.W. tubes.

t

Continuously monitordrum level whenwater is just visiblein gauge glass

Add make up to

deaerator as p the FST levelgoes down

Drum metaltemperature rise

* rate should beless than 110C/hr.

V

Close BFP dischargevalve when drumlevel approaches- 120 reading

Ensure that BFP. recirculation valveopens when flowreduces to 100 t/hr.

\ t

Boiler is filled up.

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2.3.2 Boiler Filling Using Boiler Fill Pump

This method of filling shall be used when cold filling of Boiler is required viz. hydro-static testing.

Check Boiler steamand water systemlined-up

Refer Boiler steam& water systemline up

Boiler filling solution is prepared inC.S.T.

Open fill pump suction header inletvalve from C.S.T.

Open Boiler fill pump 'A' or 'B' suctionvalves

Close fill pump discharge valves

Prime Boiler fill pump

Open isolating valves of pump dis-charge control valve

Open fill pump discharge bypass con-trol valve isolating valves.

Close fill pump discharge bypass con-trol valve

Close fill pump discharge control valve

Close filling line isolating valve to sec-ond unit

Close deaerator filling water isolatingvalve

Open economiser filling water valve &after feed control station & beforeeconmiser inlet valve

Close S.H. filling valve

V

Open economiser inlet valve &Close it bypass valve

Close isolating valves & its bypassvalves of Feed control valves downstream side.

< rCheck the level of water in C.S.T.

4Establish electric supply to Boiler fillpu mp A & B

r Star t Boiler fill pump

r

Open Boiler fill pump discharge valvewhen it attains full shut-off pressure,check pump discharge pressure.

t

Regulate filling rate by opening fillpump discharge control valve

r Water is filled up through economiser

When drum level comes to 'O' readingclose the fill pump discharge controlvalve. Stop boiler fill pump.

iClose the economiser filling line isolat-ing valve

Boiler is filled up.

2 5


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2.4 DRAFT SYSTEM

Draft System consists of Induced Draft Fans (2/3 Nos.), Forced Draft Fans (2 Nos.), Air Pre-heaters (2 Nos.), Steam Coil Air Pre-heaters (2 Nos.), Ignitor Air Fans (2 Nos) and Scanner Air Fans (2 Nos).This system provided the air required for combustion of fuel and pushes out the combustion products andmaintain a balanced draft in the furnace. This system also supplies air for cooling flame scanners.

2.4.1 ID Fan Operation

1. Starting Pennissives

i) Regulating vane in minimum

ii) Outlet damper closed

ill) Lub oil pr. adequate

iv) Fan/Motor bearing temp, not high

2. Flow chart for typical ID Fan operation

Check No PTWs are pending

Flue gas path lined up

Check ID Fan motor selected for lowspeed if two speed motor provided

Ensure that all permissives are OK

Check Air Heater in service

Check that bottom ash hopper is filledup/filling line is open

Ensure cooling \

START ID FAN

Open discharge

Load the fan by

rt

vater supply

f

ADamper

iIGV

3. Checks immediately after starting

i) Discharge damper should open automatically after 0-60 seconds,

ii) Check ID Fan Motor currentill) Other ID Fan suction and guide vanes should get close command and remains closed.

2.4.2 F.D. Fan Operation

1. Starting Permissives

i) ID Fan selected in combination is started,

ii) Control oil pr. is adequate (8 Kg/Cm ?)

iii) Fan impeller blades are in minimum position

iv) Outer damper is closed

v) Fan/Motor bearing temp, not high26


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2.Flow chart for typical FD Fan operation

Check that concerned FD fan air pathis lined up

START FD Fan motor

Ensure all permissivesIncrease Fan Loading by increasingimpeller blade pitch

Check cooling water supply Maintain 30% air flow and -20 mm WCfurnace draft

3. Checks immediately after startingi) Discharge damper should open after 0-60 secondg.

ii) .Other FD Fan discharge damper and blade position should get close command andshould remain closed.

iii) Check that furnace is not getting pressurised.

2.4.3. Starting Air Preheater

Check that air preheater guide bearing

circulating oil system is lined up

Check that air preheater support bear-ing circulating oil system is lined up

Check that air flow path is lined up

Check that gas flow path is lined up

Check that A.P.H. water washing top/ bottom valves are closed

Check that station air supply is avail-able for the air motor

Establish electric supply to A.P.H.motor. Take out the charging pushbutton of electric motor.

Start A.P.H. Electric motor.

Check A.P.H.interconnectingdamper operation

Check operation of air motor

r

fat

Interconnectingdamper opens if one APH is on/ closes when boththe APH's 'ON*.

Trip electricmotor-air motorshould start

Run air preheater electric motor, keepair motor on xAuto' standby

r

Check that supportbearing oil pumpstarts when oiltemperature exceeds30C.

7

Check that pumpdevelops correctpressure

Check that guide bearing oil pumpstarts when oil temperature exceeds30C.

V

Open cooler inlet outlet water valve/ maintain oil temp, at about 40C.

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2.4.4 Draft System Starting Start ignitor air Fan

Line up ID Fans/Motors lub oil system

IStart Scanner air Fan

Line up FD Fans/Motors lub oilsystem

Line up APHs guide bearing and sup-port bearing oil circulating system

A .Line up flue gas path

Line up secondary air path

r

Light up and load boiler

f

Start Second ID Fan

upto

Equalise Loading on Both ID

r

Start*second FD Fan

Equalise loading on FD Fans

50 MW

Fans

Take both APH in serviceStablise furnace draft

Start one ID FanPut furnace draft control on Auto

Start one FD Fan

2.5 FUEL FIRING SYSTEM

Fuel firing system comprises of three types of fuels and their associated systems for fuelpreparation, handling and firing. They are :

i) Light Oil (L.O) system for warm up (W/U),

ii) Heavy oil (H.O/LSHS/HPS) system for pressurising, and

iii) Pulverised fuel (PF) (i.e. Coal) firing system for taking on load.

In 210 MW BHEL boilers, fuel firing system is operated through a system called FSSS (FurnaceSafeguard Supervisory system). Boilers of other makes and ratings also, now-a-days, have suchautomatic firing control mechanism with different trade names likes BMS (Burner Management System)etc. As FSSS controls the operation of all fuel firing systemsin an integrated fashion, the milling system,H.O. W.U oil system etc. are not described separately.

Recently BHEL has also developed DIPC (Direct ignition of pulverised coal) system wherepulverised coal is directly fired by special ignitors. Both L.O. and H.O. systems are dispensed with; DIPChelps in saving precious fuel oil.

2.5.1 Introduction To FSSS

F.S.S.S. facilitates remote manual /automatic control of fuel firing equipment through mechani-

sed systems and suitable interlocks /logics. It is designed to ensure the execution of a safe, orderly2 8


33/133

operating sequence In start up and shut down of fuel firing equipment and to prevent errors of omissionof commission in following such a safe operating procedure.

The system provides protection against malfunction of fuel firing equipment and associated airsystem. The safety features of system are designed for protection in most common emergency situations.

F.S.S.S. comprises of control, indications and logics etc. to carry out the following :

To start complete furnace purge when all technological conditions are fulfilled.

To start, stop and monitor ignitors.

H.O. guns/w.u. oil guns starting stopping and supervision.

Pulverizer and feeder starting, stopping and supervision.

Flame scanner intelligence and checking.Furnace flame monitoring and overall furnace flarne failure protection.

To trip out all boiler fires when boiler safety is threatened.

To start/stop Ignitor & Scanner air fans.

To effect secondary air damper control with indication of auxiliary and fuel air dampermodulation /close.

To provide boiler trip signal to other equipment such as P.A. fan, turbine, generator etc.

F.S.S.S. Equipment can be grouped under three heads :

1. The operating and indicating console insert on operator's desk :

This consists of all switches for initiating controls and also indications of sta tus of all fuelfiring equipment and their auxiliaries.

2. Relay and Logic Cabinets :

These cabinets of relays, timers, programmers, circuit breakers for AC and DC controlsuppliers flame scanner unit, no coal flow units etc. They control the process logic.

3. Field Equipment :

Field equipments are those which help in actual remote" operation of fuel firingequipment and those which provide the status to the operating console and relay logiccabinet.

Field equipments include :Ignitor/W.U. oil/H.O. Trip valves, H.O./W.U. Oil, atomising steam/air, scavenging steam/air

nozzle valves (Hydrometer type), gun advance/retract mechanisms, oil gun assembly ignitors and itscabinets, flame scanner and ignitor air fans, pressure switches, temperature switches, flow switches andlimit switches.

Mill discharge valves, hot air gates, sealing air valves, tramp iron gate etc.

2.5.2 Furnace Purge

Furnace purge is required after a boiler tripout, before relighting the boiler to expel all unburntfuel particles/gases, vapours, etc. from the boiler so tha t possibilities of explosion are avoided when boiler

is lighted up.29


34/133

Boiler Purging cycle is of 5-*rtlnute$iwith air flow being more than 30%. Purging can be startedby pressing 'Purge Start' push button provided purge ready conditions are satisfied and 'PURGE READYsignal will come. This is an indication that boiler M.F.R. is reset and now boiler can be lighted up. If anytime during purging any of the "Purge Ready" conditions are violated, Purge Ready signal disappears andpurging cycle is to be started once again after establishing "Purge Ready" conditions.

Once purging of boiler is completed boiler will trip if any of 'Boiler trip' conditions occur.

Purge Ready Conditions :

220 VD.C. & 110 VA.C. supply to F.S.S.S. panglgstablished.

Boiler drum level normal.

Atleast one I.D. and one F.D. fan running.

Ignitor Trip valve proven closed.Warm-up oil Trip valve proven closed.

Heavy oil Trip valve proven closed.

All ignitor oil/air valves proven closed.

All W.U. & H.O. nozzle Hydrometer valves proven closed

All pulverizers are off.

All R.C. feeders are off.

All mills hot air gates closed and cold air dampers in minimum open position, (Less than 55

degrees).All auxiliary secondary air dampers modulating to maintain adequate windbox to furnacedifferential pressure.

All elevation flame scanners show "no flame".

No boiler trip command persisting.

2.5.3 Starting the Ignitors

2.S.3.1 IGNITOR TRIP VALVE INTERLOCK :

i) Ignitor trip valve will open when Trip valve 'Open'. P.B. is pressed provided all the

following conditions are fulfilled.a) Ignitor oil supply pressure is adequate (more than 13 kg/cm 2).

b) All Ignitor valves are closed.

c) No boiler trip command is persisting.

d) Ignitor oil pressure is more than 9 kg/cm 2.

e) When Ignitor trip valve is fully open, 'Open' signal comes on F.S.S.S. Console,

ii) Ignitor trip valve will close under following conditions :

a) "Close" Push button is pressed from console.

or b) Ignitor oil header pressure falls below 9 kg/cm2

for more than 2 sees, and any Ignitorvalve not closed. " ~

30


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or c) Boiler trip command present. When Ignitor trip valve is closed, Valve 'Closed' green

signal comes on.2.5.3.2 IGNITOR STARTING

There is no separate Ignitor start switch provided for any of the elevation AB, CD or EF ignitors.Pressing any one pair (L.O. or H.O.) of oil gun 'START' push button gives a starting impulse to all fourignitors of that elevation. The spark is applied for 10 seconds only for every pressing of ignitor start pushbutton.2.5.3.3 IGNITOR STOPPING

All four ignitors of each elevation are provided with one "STOP" Push button for taking outignitors from service. Also ignitors get stop command at the end of stop time trial of H.V. elevation or W.Uoil elevation.

When individual ignitor gets stop command its motorised oil/air valve closes thus taking outignitor from service.

2.5.4 Warm Up Oil Firing

Light (Warm up) oil can be fired only at AB elevation after selecting L.O. through L.O. SelectorPush Button. Oil guns have been programmed to light up in pair basis diametrically opposite (1,3 and 2,4)corners from the pairs. Each pair has got a separate start/stop push button. Warm up oil guns can belighted up, only if atleast 3 out of 4 ignitors at corresponding elevations are in service. The warm up oilguns are not self sustaining hence, ignitors corresponding to W.U. oil gun in service must remain on aslong as W.U. oil gun is in service. There is no flame monitoring for warm up except making sure that theyburn with the help of ignitors.

2.5.4.1 LIGHT OIL TRIP VALVE INTERLOCKS Light oU trip valve can be opened from F.S.S.S. Console 'Open' P.B. provided :

i) Boiler Trip Circuit (M.F.R.) is reset, and,

ii) All the light oil nozzle valves (Hydrometer) are proven closed and,

iii) Light oil supply pressure adequate.

When L.O. Trip valve opens "Valve Open" red light comes on.

Light Oil Trip Value will close if:

i) Light oil header pressure is low (2 sees, time delay) (less than 1.5 kg/cm2).

ii) Light oil to air differential pressure is low 0:3 kg/cm2 for more than 2 seconds.iii) Boiler trip occurs.

iv) Valve 'Close' Push button on F.S.S.S. Console is depressed.

Light Oil elevation start permlssives

i) D.C. Power, available.

ii) Ignitor Trip valve proven fully open.

iii) Light oil Trip valve proven fully open.

iv) Air flow adjusted between 30% to 40% of full load air flow (This condition is not requiredonce any feeder is proven on).

31


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v) Fuel air nozzle till placed in horizontal position (This condition is not required once any

feeder is proven on).vi) No boiler trip command persists.

Pennissives for each Light Oil Comer to be Satisfied for starting that corner gun.

i) The light oil gun is inserted in guide pipe and coupled,

ii) The local maintenance control switch is placed in remote.

ill) The light oil burner manual isolation valve is open,

iv) The light oil atomizing air manual isolation valve is open.

2.5.4.2 LIGHT OIL GUN STARTING SEQUENCE & MONITORING

When light oil pair Star t push button is depressed pair of light oil guns are placed in service infollowing sequence, (provided L.O. elevation start permissives and corner start permissives are satisfied).

i) In first 10 seconds of pair start time trial the assocjated_elevation ignitors are started.When ignitors are proven 'ignitor on' signal comes on. If the flame is noTpfovedrspark will cease and Jamesbury Valve will close after 10 seconds. ~~

- , -r W


37/133

2.5.4.4 UNSUCCESSFUL ELEVATION START

At the end of 90 seconds of light off pair start time tried of the second pair of light oil guns at theelevation a minimum of 3 of the 4 light oil nozzle valves at that elevation must be proven open, or an"Unsuccessful Elevation Start" alarm is annunciated and all the light all guns at that elevation are shutdown in an orderly fashion.

2.5.4.5 WARM-UP OIL ELEVATION SHUT DOWN

Warm-up oil elevation is removed from service on a pair basis. Depressing the associatedelevation pair stop Push button will initiate a 375 seconds stop time trial to shut down and scavenge theassociated pair of L.O. guns as follows :-

1) During first ten seconds of stop time trial associated elevation of ignitors is started.(Ignitors associated with L.O. gun not in service will only acknowledge the start signal

since the ignitors are already on at the L.O. gun in service).2) At the end of ignitor start time a stop command Is sent to corner 1 (when pair 1 & 3 is

stopped or corner 2 (when pair 2 & 4 is stopped).

3) Fifteen seconds later, a stop command is sent to Corner 3 (When pair 1 and 3 is stopped)or Corner 2 (when pair 2 and 4 is stopped).

When an individual warm up oil gun, that is in service, receives a stop command.

a) A Scavenge command for that corner is initiated and the W.U. oil nozzle valve closes. Theatomizing air valve remains open.

b) When the W.U. oil nozzle valve is proven fully closed and if the associated ignitor isproven on and the atomizing air valve has remained open, the Scavenge valve opens.

c) When the Scavenge valve is proven fully open, a five minutes scavenge period is started.

d) At the end of 5 minutes scavenge period, the atomizing air and Scavenge valves close.

e) When both the valves are proven fully closed the W.U. oil gun is retracted from firingposition.

Six minutes after remaining (2nd) pair of W.U. oil guns stop is initiated, a back up trip signal isestablished which will remove the associated elevation of ignitors from service and initiate a close signalto all of the W.U. oil nozzle valves, all of the atomizing air valves and all of the scavenge valves at theelevation to ensure that they are closed.

Fifteen seconds later on "Unsuccessful Elevation Shut Down" alarm is annunciated if:

a) Any W.U. oil gun is not retracted from firing position at that elevation.b) Any W.U. oil nozzle valve is not closed at the elevation.

2.5.4.6 SCAVENGING OF W.U. OIL GUN

A warm up oil gun that is in service can be scavenged individually by placing its localmaintenance switch to the "SCAVENGE" position. The W.U. oil gun will be shut down, scavenged, andretracted as described above. The individual W.U. oil gun can only be restarted by initiating another pairstart sequence.

Scavenging using local maintenance switch is possible only if ignitor associated to the gun isproven on.

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Scavenging will not take place during conditions which cause boiler trip or corner trip.

In the event of ignitor trip out during scavenge (using local maintenance switch or duringelevation pair shut down operation) cycle; scavenge and atomizing air valves will close interrupting thescavenge.

2.5.5 Heavy Oil Firing

Heavy oil can be fired at CD and EF elevation. It can be fired at AB elevation also provided H.O.is selected through H.O. Selector. Push button (ICRL 170 AB is on). Heavy oil gun have also beenprogramme d to light up on pair basi s, diametrically opposite corners (1,3 and 2,4) from the pair. Each pairis provided with separat e sta rt/ sto p pu sh button.

H.O. guns can be lighted up only if atleast 3 out of 4 ignitors at corresponding elevations are inservice. H.O. guns are self sustaining only when elevation firing rate is above 30% Hence, ignitorscorresponding to H.O. guns in service can only be removed when H.O. burner header pressure is above3 kg/cm 2 (g) and at least three H.O. guns at the elevation are in service.

Heavy oil gu n flame is monitored by flame se nsing sca nners only when the following condit ionsare fulfilled :

i) H.O. firing ra te (elevation load) is above 30%.

ii) 3 or more H.O. gu ns at the elevation are in service,

iii) Ignition energy is removed.

2.5.5.1 H.O. TRIP VALVE INTERLOCKS :

H.O. trip valve can be opened by pressing 'OPEN' push button provided.

a) Boiler Trip circuit (MFR) is reset, andb) All H.O. Nozzle valves of AB, CD, EF oil guns are proven fully closed, andc) H.O. supply pressure is adequate, (more than 7 kg/cm 2)d) H.O. pressure not low (less than 1.5 kg/cm 2 for more than 2 sees)e) When trip valve is full open valve 'Open' red light comes on. (ICRL 275 and 2 CRL 275 are

on).

H.O. Trip valve closes under any of the following conditions :

a) H.O. header pressure is low for more than 2 seconds orb) Steam or heavy oil differential pressure is low (less than 0.3 kg/cm 2) for more than 2

seconds and provided no guns are being started or stopped, orc) A boiler trip occurs, or

d) H.O. trip valve 'Close, valve 'Closed' green light comes on

2.5.5.2 H.O. RECIRCULATION VALVE INTERLOCK

Opening :

H.O. recirculation valve can be opened following a boiler trip and before starting furnace purgecycle by pressing valve 'Open' push button. Valve opens provided :

a) All the H.O. nozzle valves (hydromoter) are fully closed, and

b) H.O. trip valve is closed.

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ClosingH.O. decirculation valve closes automatically when.any one of the H.O. nozzle (hydromotor) is

not closed.2.5.5.3 HEAVY OIL ELEVATION START PERMISSIVES

a) D.C. Power available.

b) Ignitor Trip valve proven fully open.

c) No boiler trip command persists.

d) H.O. Trip valve proven fully open.

e) Heavy oil temperature above 100C.

f) Air flow adjusted between 30% and 40% of full load air flow.g) Burner tilt placed in horizontal position.

* These condition are no longer required once any one feeder is proven on.

2.5.5.4 H.O. CORNER START PERMISSIVES

At each main oil corner to be placed in service following conditions should be satisfied.

a) The main oil gun is inserted in guide pipe and coupled.

b) The local maintenance control switch is placed in remote.

c) H.O. manual isolation valve is open.

d) Atomizing steam manual isolation valve is open.

2.5.5.5 H.O. GUN STARTING SEQUENCE

Same as that for L.O. guns except.

a) H.O. is to be put in place of L.O.

Atomizing steam is to be put in place of Atomizing air

b) H.O. elevation ignitors can be removed by pressing ignitor stop push button when :

3 out of 4 H.O.nozzle valves are proven open, and

Elevation Loading is above 30%.

Minimum 2 out of 4 flame scanners serving that elevation prove flame on.2.5.5.6 H.O. ELEVATION SHUT DOWN :

Same as that of L.O. elevation shut down except -Ignitors associated with H.O. giins in service may or may not be on hence when stopcommand is given in first 10 seconds elevation ignitors in service receive start command;H.O. is to be considered in place of L.O.Steam is to be considered in place of air.

2.5.5.7 SCAVENGING OF H.O. GUN :

Same as "Scavenging of L.O. gun".

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2.5.6 Pulverizer Operation

2.5.6.1 AVAILABILITY OF IGNITION ENERGY FOR PULVERIZER OPERATION :

Prior to starting any pulverizer, ignition energy must be adequate to support coal firing. This isaccomplished as follows :-

Pulverizer. Ai) A minimum of 3 out of 4 Elevation AB light oil (or heavy oil) nozzle vales proven open, or

11)

Pulverizer B

i)

ii)

Pulverizer C

i)

ii)

iii)

Pulverizer D

i)

ii)

Boiler loading is greater than 30% and Pulverizer B is in service at greater than 50%loading.

A minimum of 3 out of the 4 Elevation AB light oil ( or heavy oil) nozzle valves .prove open,orBoiler loading is greater than 30% and Pulverizer A or C is in service at greater than 50%loading.

A minimum of 3 out of the 4 Elevation CD heavy oil nozzle valves proven open, or

Boiler loading is greater than 30% and pulverizer B or D is in service at greater than 50%loading, or

A minimum of 3 out of the 4 Elevation AB light oil (or heavy oil Nozzle valves proven open

and pulverizer B is in service at greater than 50% loading.

A minimum of 3 out of the 34 election CD heavy oil nozzle valves proven open, orBoiler loading is greater than 30% and Pulverizer C or E in service at greater than 50%loading.

Pulverizer Ei) A minimum or 3 out of-the. 4 Elevation EF heavy oil nozzle valves proven open, or

ii)

iii)

Pulverizer F

i)

ii)

Boiler loading is greater than 30% and Pulverizer D or F in service at greater than 50%loading, or

A minimum of 3 out of the 4 Elevation CD heavy oil nozzle valves proven open andpulverizer D is in service at greater than 50% loading.

A minimum of 3 out of the 4 Elevation EF heavy oil nozzle valves proven open, or

Boiler loading is greater than 30% and Pulverizer E is in service at greater than 50%loading.

2. 5.6.2 PULVERIZER READY :

Prior to starting a pulverizer, a Pulverizer Ready condition for the respective pulverizer must beestablished by the following conditions being satisfied :

i) D.C. Power available.36


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ii) Fuel and air nozzle tilts placed in the HORIZONTAL POSITION (see Note below).

ill) Air flow adjusted between 30 and 40% of full load air flow (see Note below).

Note : Conditions (ii) and (iii) above are no longer required to satisfy a Pulverizer Ready condition whenany feeder is proven on. However, the operator is still restricted to a minimum air flow above 30%of minimum continuous rating (M.C.R.).

iv) At the respective pulverizer, all of the following conditions are to be satisfied.

Pulverizer discharge valve open. (CRL 263 A is on)

Seal air valve open.

Cold air shut-off gate open.

Pulverizer outlet temperature less than 90C.

Feeder inlet gate open (operator check only).

Tramp iron hopper valve open.

Primary air adequate

When all of the above conditions are satisfied for the respective pulverizer, its associated"Pulverizer Ready" (white) light comes on. (CR 48, A,B,C,D,E,F are on).

2.5.6.3 PULVERIZER START :

When both "Ignition Energy Available" and "Pulverizer Ready" condition are established for therespective pulverizer, it may be placed in service as follows :

i) Start the pulverizer by depressing its associated push button.

ii) When the pulverizer is proven on (ICRL 53, A,B,C,D,E,F are on) as indicated by its (red)start ("Pulverizer On") light being on, open the hot air gate by depressing its open pushbutton and allow the pulverizer to come up to temperature.

iii) When the pulverizer is upto temperature (approx.) 60-70C, start the feeder by depress-ing its associated START push button (associated elevation of fuel air dampers to beproven closed for feeder starting).

Coal flow must be proven either by the coal flow detector or satisfactory pulverizer amps withinfive seconds after the feeder is started.

Fifteen seconds after the feeder is started, the feeder output is released to automatic control, andthe fuel air dampers are opened to modulate as a function of feeder speed.

When a minimum of two feeders are on for fifty seconds the feeder speed is released to automaticcontrol, and the fuel air damper are opened to modulate as a function of feeder speed.

When a minimum of two feeders are established at greater than 50% loading, the associatedelevation of oil guns may be shut down provided the feeder has been on for a minimum of three minutes.

2.5.6.4 PULVERIZERS IN SERVICE :

i) Either of the following conditions will run the feeder speed to minimum until the

initiating condition is corrected, at which time the feeder will be returned to control.

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a. Pulverizer bowl differential pressure high.

b. Pulverizer amps above maximum set point.

ii) Loss of coal flow and low pulverizer power as confirmed by low pulverizer amps will tripthe feeder, open the cold air damper, and close the hot air gate. The operator should takeappropriate corrective action, then reopen the hot air gas and restart the feeder.

ill) A high pulverizer outlet temperature (above 90C) will open the cold air damper and closethe hot air gate.

iv) The following conditions will initiate a pulverizer trip command :

a. Pulverizer discharge valve not open.

b. Loss of unit D.C. power (for more than 2 seconds).c. Pulverizer ignition permit is not satisfied wh&i support ignition is required and lessthan 3 out of the 4 associated oil guns in service.

d. Boiler trip

e. Primary air trip (see item v below).

(v) When both primary fans stop the primary air duct pressure falls below the low sejt point(for more than 5 seconds), all pulverizer in service receive a stop command. When theprimary air duct pressure falls below the very low set point all pulverizers in service aretripped instantaneously.

When only one primary air fan stops and four or more pulverizers are in service, a trip commandwill be given starting from the lowest pulverizer in service until the number of pulverizer remaining inservice is reduced to three.

2.5.6.5 PULVERIZER SHUTDOWN

Shut down of pulverizer is accomplished as follows :

i) If not in service, start the oil elevation associated with the pulverizer to be shut down.

ii) Reduce the feeder speed to.minimum.

iii) Close the hot air gate by depressing the CLOSE push button.

iv) When the pulverizer outlet temperature is reduced to approximately 60C shut down thefeeder by depressing its stop push button.

v) Allow the pulverizer to run for approximately two minutes to ensure tha t it is completelyempty of coal, then shut down the pulverizer by depressing its STOP push button.

vi) The associated oil elevation should be shut once furnace condition have stabilized.

Whenever pulverizer or feeder is shut down by the operator there will be steady indication of therespective off lamps at the console insert.

Whenever a pulverizer or feeder is tripped a flickering indication will come in the respective "off lamp at the console.

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2.5.6.6 F.S.S.S. PROTECTS THE BOILER BY TRIPTOIG OUT ALL FUEL INPUT UNDER THE

FOLLOWING CONDITIONS :Loss of 220V D.C. to F.S.S.S.

Less than fire ball load and loss of A.C. on any elevation in service

Flame failure trip

Loss of fuel trip

When at least one pair of ID & FD fan is not in service

When Boiler load is less than 30% air flow falls below 30%

Furnace Pressure High/Low (+ 200 mm)

Drum level High/Low (+ 200 mm)

Turbine trip

Both Boiler trip buttons on console pressed

Note : Loss of fuel trip occurs only when 3 ignitors have been proven and if one of the proven ignitorgoes off or if trip valves on warm up heavy oil and ignitor closes or if any valve is open and itscorresponding guns (minimum 3) are not in service, when both pairs are pressed. This conditionis applicable when boiler is on oil firing without any coal feeders.

2. 5.6.6 FIRE BALL CONDITION :

A Fire Ball condition is established as follows for the main fuel indicated :

a) Coal firing - any feeder established.

b) Main oil firing - a minimum of three of the four heavy oil nozzle valves proven open at anelevation (AB or CD or EF) and the elevation loading is above 30%.

When the ignition energy is removed the established FIRE BALL will be monitored by the opticalflame scanners. A unit flame failure signal is initiated when there is a NO FIREBALL condition at allelevations and either any feeder is not working at any elevation (AB or CD or EF) where less than threeof the four associated ignitors are proven on.

An elevation NO FIREBALL condition is as described below for the respective elevations :

Elevation A & B :

i. Elevation AB flame scanner count shows no flame and any of the following :

a) Loss of elevation (AB) A.C. power for more than 2 seconds, or

b) Light oil is selected at elevation AB and less than 3 of the four elevation AB light oil nozzlevalves are proven open, or

c) Heavy oil is selected at Elevation AB arid less than 3 of the 4 elevation AB ignitors areproven on.

ii) Both feeder A and B are off either :

a) Loss or elevation (AB) A.C. power for more than 2 seconds, or

b) Less than 3 of the 4 elevation AB heavy oil nozzle valves proven open.

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c) Elevation AB flame scanner count shows no flame and less than 3 of the 4 elevation AB

igniters are proven on.Elevation C & D

Same as above except delete condition AB and substi tute elevation designation E and F for A andB respectively.

Elevation E & FSame as tha t for elevation A & B except delete condition AB substi tute elevation designation C

& D for A & B respectively.

2.6 BOILER PURGING & LIGHTING UP

Feed pump is started & Boiler feed linecharged

Boiler steam &water system islined up

Refer Boiler watersteam system lineup.

Boiler is filled up

to working levelof gauge glass

Refer Boiler filling

instruction.

B.F.P. run on recirculation

1Boiler air & fluegas system islined up.

r

Start Air Preheaters

Refer Drafts system

A&B

Take lube oil system of I.D. fans inservice

Take oil systems of F.D. fans in service

Refer F.D. fanstarting instruction

Start one I.D. fan. Refer I.D. fanstarting instruction

Start one F.D. fan

i

Maintain 30% Airflow and 5 to10 mm WCLfurnace-.draft

Put secondary airdamper controlsystem on "Auto"& check thatauxiliary air

dampers aremodulating tomaintain 35-40 mmWC windbox tofurnace differentialpressure.

>Start E.P. rappingmechanism

>r

-

Refer F.D. fanstarting instruction

Air flow shallnot be morethan 40%

Check fuel airdampers aremodulating withaux. air dampers.

Check that E.P.insulator heaterswere switched on24 hrs beforeboiler light up.

Start Scanner Air Fan A/B

Start Ignitor Air Fan A/B

Select Burner tilt control on manual,keep burner tilt in horizontal position

Ensure that warm up oil^system is inservice, L.O. system is charged

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CHECK:

i) A.C. & D.C. power supply is es-tablished to F.S.S.S. relatedequipment

ii) Drum level is normal

iii) At least one I.D. fan one F.D. fanin service

iv) Minimum of 30% air flow is es-tablished

v) Ignitor.trip valve is proven closed.

vi) The light oil trip valve is provenclosed.

vii) The heavy oil trip valve is provenclosed.

viii) All the ignitor valves in all eleva-tions are proven closed.

ix) All the wajrmup and heavy oilnozzle valves at all elevationsare proven closed.

xii) All feeders are off.

xiii) All hot air shut off gates are fullyclosed.

xiv) All cold air dampers are lessthan 5 open.

xv) All elevation flame scannersshow no flame.

xvi) No boiler trip command is pres-ent

Purge start permissive

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Check that atomizing air lines for igni-tors & W.U. Oil guns are line up andcharged.

Make ready each W.U. oil corner indi-vidually

Start furnace purgeby pressing StartPurge

After 5 minutescheck that purgecomplete lightcomes on

Open igniter tripvalve from F.S.S.S.console insertOpenPB

Open light oiltrip valve fromFSSS consoleinsert Open PB

Purge cycle is of 5 minutes

This indicates thatM.F.T. relayis reset.

Igniter trip valveswill open if i) M.F.T. relays

is reset.

ii) Igniter valvesare provenclosed.

iii) Igniter oilsupplypressure isadequate (14kg/cm2) ^

L.O. Trip valveopens if 1) M.F. trip

relay is reset

2)

3)

Light oilnozzle valvesare provenclosed.

Light oilpressure isadequate (5kg/cm 2).

Select light oil firing from FSSS insertcontrol PB for AB elevation.

Establish light oilelevation permit

Check :i) D.C. Power

available.ii) L.O. trip valve

proven fullyopen.

iii) Air flowbetween 30%&.4Q%

iv) Burner tiltplaced inhorizontalposition.

v) No Boiler tripcommand ispersisting.

vi) Light oil gunis inserted inguide pipe &coupled.

vii) Localmaintenancecontrol switchis placed on"Remote"

viii) Light oilManualisolating valveopen

ix) L.O. Atomisingair manualisolating valveare open.

Start AB elevationare pair of L.O.guns bydepressing pairstar t PB onFSSS insertconsole.

Refer L.O.elevation startup.

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Check associated AB elevation at least3 out of 4 lighters are-proven on

rCheck that selectedpair of L.O. gunsare proven on intime sequence.

>rStart second pair of L.O. guns A.B.elevation bydepressing startPB on

- >

-

Maintain warmup oil pressure4.5 kg/cm 2through pressureregulating valve.Also maintainoil/ air AP between1 to 1-5 kg/ cm 2.

Maintain Warmup pressure 4.5kg/cm 2 throughregulating valve.

Check that at least 3 out of 4 L.O. gunsare proven on in timed sequence.

Check i) Light oil header pressure is

adequate.

ii) Light oil /air differential pressureis more than 1 kg/cm 2

Otherwise L.O. trip valve will close.

Check boiler expansion is free

Check:

Ignitor oil header pressure isadequate (14 kg / cm 2.)

Control firing rateduring initialwarming up suchthat boiler startssteaming after 45minutes.

Follow the coldstart up curvewhile bringingup pressure &temperature.

Fig. 2.1

Keep C.B.D. controlvalves fully openduring warm up

Open C.B.D.Isolating valve full

Control flue gas temperature at fur-nace exit below 538C by controllingfiring rate till adequate flow is estab-lished through reheater.

T

When boiler startssteaming throttleS.H. vents & drains

r

When drumpressure reaches2 kg/cm 2. Closedrum vents andoutlet header vent

- >

Warming up shouldbe slow; steamingshould start after45 to 50 minutesof lighting up.See Fig. 2.1.

Refer cold startcurve for rateof pressure &temperature rise.Fig 2.1

r

Close steam cooled wall extended sideoutlet header vents

Close S.H. Desuperheater link ventvalves

Close platen S.H. outlet link vent valves

Throttle following: S.H. drain, Radiantroof S.H. inlet header drain, & sidesteam cooled out let header drain, RearHeader drain, S.H. S.W.W. front roof inlet header.

Do not close these drain valves fullybefore rolling the turbine.

Check that M.S. line drains are opened(near turbine).

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7/27/2019 10. Power Plant Operati

10. Power Plant Operation Vol-V

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Transcript of 10. Power Plant Operation Vol-V