Tech. Day Presentation.ppt

8/11/2019 Tech. Day Presentation.ppt

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Power Sector Western Region

Technology Day

11th May 2009


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TECHNOLOGICAL TOOLS


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Use of Electrical Torque wrench for Tightening

Boiler Structure Bolts

At 1 x 500 MW Khaperkheda


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Cycle time reduction in tightening boiler structure bolts

Background

At boiler erection site thousands of BOLTED JOINTS are to be tightened

MANUALLY using DE Spanners for snug tightening & Torque tighteningby trip torque type long handle torque spanner.

The process of bolting arrangement consumes enormous time forachieving desired results, including uniform tightening & ensuring adesigned torque value.

This process was identified for taking up Improvement project because ofthe following

being repetitive in nature

time consuming

labour intensive

having substantial amount of preparatory work to be done before thestarting actual process (set up time)

high level of risk involved (some locations for actual work place areabove 80 meter above ground level & are to be performed ontemporarily erected scaffoldings


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Objective

Reduction in time taken for complete bolting arrangementnecessary for a 500 MW Boiler erection (at Khaperkheda siteabout 40, 000 no. M24 Bolts of lengths 70160 mm are used)

Ensuring designed tightness of bolting arrangement without

further need of cross checking by Quality representative Safer working conditions for Operator



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Evaluation of alternatives

1. Pneumatic torque wrench Benefits

Available with leading hand tool manufacturers like Bosch, Ingersoll Rand &

others.

Widely used in manufacturing plants (automotive assembly lines) where high

turnover per day is the hour of need (but here the Operator has a fixed place &jobs move to his operating area one after another).

These wrenches are comparatively lighter.

Drawbacks for us

Difficulties in ensuring dry air to the wrench in all weather conditions

Maintaining desired air pressure at a long distance through a compressor

Requirement of supports since length of air pipes may extend up to 100 meters

Thus making the whole arrangement very clumsy & big.



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2. Hydraulic torque wrench

Benefits

Available with leading hand tool manufacturers

Widely used in manufacturing plants

Drawbacks for us

Need sophisticated hydraulic equipment (difficult to maintain)

Require very good quality pressure hoses to feed optimumliquid pressure to the wrench limiting factors

Practically impossible to provide such facilities at sites



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3. Electrically operated torque wrench

Benefits

Such wrenches are popular in assembly lines especially where

job sizes are bigger & operator has to move around the job Available with leading hand tool manufacturers

Electrical cables are much smaller, lighter & easily

maneuverable

Operate at 1 phase ac supply abundantly available at all areasof sites



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Electrically operated torque wrench(contd..)

Results of Field Trial

M/s Tristar Industrial Tools Pvt limited was a source located for

making a demo at Khaperkheda

Trial was successfully done on 10thApril 2009 at a height of about

10 meters on Column number 19.

Time taken to fully tighten bolted joint by ETW was about 15

seconds as against 3 to 4 minutes by a handle type Trip Torque

Wrench

Substantial saving in operation time for the activity

Saving in manual effort by Operator

Positive assurance of Quality of bolted joint.



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Electric wrench for tightening boiler structure bolts

Technische Daten DEATechnical data DEA

PLARADGERMANY MakeTechnische Daten DEATechnical data DEA

Our select ion

Type DEA 12 TLX Torqu e 200 1220 NM Weigh t 6,8 kg


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Electr ic wrench tightening of boiler structure bolts


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Electr ic wrench tightening of boiler structure bolts


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Expected Benefits

Tangible Saving in Time - On average saving of about 3 minutes per bolt

Saving in manpower cost

No need for Quality representative to ensure desired objectiveof proper tightness

Additional helper to hold spanner and a trip torque wrench, notrequired.

Intangible

Safety of Operating Personnel (Operators & others assisting him)

from any Accidental fall due to Slipping Slipping / Falling of the job from temporary scaffolding

Better safety of personnel on ground from falling of long torquewrench etc.



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Measurement of Face Run- out of IP & LP Rotors

by improvised technique at site


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Measurement of Face Run- out of I P & LP Rotors

Normal Practice (Contd..)

The normal method has few problems associated with it1. It is not possible to restrict axial movement of the rotor in order to avoid

overshooting the range of the dial gauge.

2. Area of contact being very small, it requires extreme care and controlwhile operating the EOT, lest it should cause an irreparable accident and

lead to loss to both men and material.3. It has often been noticed that there is quite an error between the

measurement made at shop and those made at site leading to avoidableloss of time in correspondence, summoning experts from MUs, etc.

4. It gives the feeling of using a very primitive and un-reliable method of

measurement.5. Overall, it is never like measuring the run-outs by anchoring the rotor on

a lathe to take the measurements and thats exactly the cause of theerror.


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Suggested New Method

A simple device is made at site using the following material

Shaft of 40mm x 1000mm long 1 no.

Ball Bearings with Plummer block for above shaft 2 nos.

Supports to anchor the Plummer blocks 2 nos.

Cross arm 1 no.

Dial Gauges for mounting to X-arm 2 nos.


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Brg with

Plummer

Block

Cross Arm

Shaft Support provided by UnitExternal Support for

anchoring the

Plummer Block

Dial

Pointers

Dia

40

Shaft

Fixture developed and used


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Advantages

User friendly and costs only Rs.5000/- to make.

Does not require too much of a precision in machiningthe shaft.

Does away with repeated rotation of the rotor forevery reading.

Reduces the risk of the rotor toppling during rotationby EOT crane.

Compares well with the values attained at works on alathe.

Stator l i f ting by Strand Jack M ethod at 1x250MW Uni t#8


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TATA Trombay

This was the 1sttimethe Generator Statorhas been lifted by

Strand Jack Methodin PS-WR. Also, thisis the 1st for 250MWStators in the whole

of BHEL. Pictureshows Stator liftedoff the Blocks.



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TATA Trombay.Contd

Stator lifting inprogress



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TATA Trombay.Contd

Stator lifted andbeing moved insidethe A-Row of TG

Building



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TATA Trombay.Contd

Stator lifted abovethe bottom of TGDeck and ready to

be moved inside forplacement.



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TATA Trombay.Contd

Picture shows theStrand JackHydraulic Control

System

Stator l i f ting by Strand Jack Method at 1x250MW Uni t#8


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Stator li f ting by Strand Jack Method at 1x250MW Uni t#8

TATA Trombay.Contd

Picture shows statorin position

The entire operation

was completed in 4hrs from the start.


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PORTABLE INDUCTION HEATING MACHINE


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I NDUCTION HEATING MACHINE

Conventionally, we at BHEL Power Sector Sites have been using theInduction Heating Machines of EDN Bangalore make. There are certain

disadvantages of using this equipment listed below:1. Too bulky and comes in two parts one the Induction HeatingEquipment proper and the other, the operators panel. Weighs a fewtonnes.

2. Due to its bulk, moving the machine to different areas of work is an

arduous task. Each shift of the machine is a 1 days activity.3. Often, it has been seen that when the machine is moved from onelocation to the other is has not been in use for a few months, the next re-start is faced with quite a few problems. The reason is not known.

4. Getting spares on time for the equipment is a big issue. This results in

machines with minor repairs and requiring spares quarantined.5. Overall the machine is not user-friendly

6. Costs around Rs. 75 Lakhs per machine


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I nduction Heating Machine -.Contd


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Alternatively, there are machines available in the market and beingused by our competitors that is a vast improvement on the EDN

Make machine and has the following advantages:1. Very small and easily portable, thus rendering easy movementof the machines to various locations without loss of vital erectioncycle time. Requires only a 2-3 hrs for shifting and re-connecting.The entire machine is as compact as welding transformer and issingle modular. Weighs approx. 105Kgs.

2. The connections are very simple and does not need expertise.

3. Though imported, has a presence in the Indian market for thelast 3 years and has been used to weld pipes of 94mm thick atSipat. The machine can be used to thicknesses in excess of100mm pipes as well. The size of MS Pipe for the proposed 660MWUnit with Full Flow is 660 x 102mm.

4. Costs only Rs.30 Lakhs. For every one machine of EDN Make,one can two of this kind.


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C d


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660 MW 800 MW

System Material Size Material Size

MS - HalfFlow

P91 OD 508 x 80 P91 ID 370 x 66

MSFullFlow

P91 OD 660 x 102 P91 ID 480 x 90

HP BypassU/S

P91 OD 355.6 x 52 P91 OD 355.6 x 54

HRHHalfFlow

P91 OD 711 x 40 P91 OD 813 x 49

HRHFull

Flow

P91 OD 864x48 P91 OD 1016 x 58

LP BypassU/S & D/S

P91 OD 711 x 40 /OD 1219 x10(SA691 2 Cr)

P91 OD 864 x 50 /OD 965 x 35


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Induction Heating for Opening & Tightening

Casing fasteners of Steam Turbine

I nduction Heating for opening & tightening


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I nduction Heating for opening & tighteningCasing of Steam Turbine

Introduction

Casing of steam turbines are tightened together by usingthreaded fasteners of M48 to M140 size .

These fasteners referred commonly as studs and cap nuts have

to be tightened firmly to withstand the high internal pressure

and temperature.

During the tightening process, specified value of elongation has

to be achieved so that during working at high temperature, the

nuts will not slacken .

A recommended practice for tightening these fasteners is heat

tightening.



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Commonly used devices for heating the fasteners

Electric heaters - which include heater elements, cables, power source

/transformer of high capacity etc.

Gas heaters. This is relatively simpler method which uses the specially

fabricated bolt heating devices - Gas Torches with special nozzles, and

oxy-acetylene cylinders , compressed air supply etc.

Main disadvantages of the above two methods

Long time taken for the operation

Due to the slower rate of heating, effectiveness of these methods is

less and some other problems such as seizure of the threads also

occur quite frequently.

Apart from this, the arrangements required are also complex and timewasted in maintenance / repairs of the equipment in case of defects is

quite considerable.



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Induction heating method for threaded fasteners

Induction heating method is being used in other site applications such

as preheating of joints for special welding of alloy steel pipe lines inthermal power stations.

This method is very quick and effective means for heating.

By using some modified gadgets, it was found suitable for loosening

and tightening of the big size threaded fasteners of steam turbines,

valves etc.

SAS Nagpur decided to use the induction heating method for loosening

and tightening of threaded fasteners.

This method has resulted in saving valuable time for dismantling and

assembly of steam turbines during overhauls. The method is simple

and highly effective.

With the use of induction heating method, the problem of seizure of

threads necessitating cutting and gouging of the nuts and studs, in

LMW design, has been minimized.



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Comparison of time required for bolt opening

210 MW /500 MW KWU Electric/ Gas Heating Induction Heating

HP inner casing 6 hrs 3 hrs

IP Outer casing 10 hrs 7 hrs

IP inner casing 14 hrs 8 hrs

Time saved for overhauling is 3 days .

For a 210 MW set this translates into a gain of 5.04 million units perday

i.e approx. Rs. 2 crore per day

For 500 mw set, 12 million units per day i.e.approx. Rs.4.8 crore perday

LASER ALIGNMENT KIT


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LASER ALIGNMENT KIT

OBJECTIVETo carry out various alignment works in Turbine erection

With high precision.

At a reduced cycle time.

WORKS CARRIED OUT

Catenary of pedestals

Centering of bores of Diaphragms, Pedestals, Shaft Seals etc. Alignment of Rotors.

CATENARY OF PEDESTALS

Accuracy of 10 Microns achievable.

Source equipments to be placed at extreme pedestals.

Mobile equipment placed in intermediate pedestals.

Laser is passed thro mobile equipment and adjustments carried

out as per requirement.

LASER ALIGNMENT KIT


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LASER ALIGNMENT KIT

Centering of Bores of diaphragms,pedestals,shaft seals etc

Source Laser device fixed in one extreme end pedestalReceiver end device fixed in other extreme pedestal.

Special fixtures used for centering of intermediate pedestals.

Online adjustment possible.

Alignment of Rotors

Can cater to Coupling Dia from 100 mm to 1200 mm.Alignment Device fixed on couplings to be aligned

Total misalignment is indicated by just 60 degree rotation of Rotors.

Misalignment values as well as correction required indicated in

display.

Salient Advantages

Saving in Cycle time.

Accuracy of Measurement.

Indication of correction factors.

LASER ALIGNMENT KIT


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LASER ALIGNMENT KIT

CONCLUSION

The Laser Alignment kit is a useful equipment that is State of the Art

in Technology and can be used very effectively in Turbine activities at

high precision and reduced cycle time, as has been proved in

Kudankulam site.

Hence extensive use of this equipment has to be practiced.

ORBITAL WELDING


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ORBITAL WELDING

PurposeTo provide leak proof joint between Tube to tube sheetin Condenser in addition to Forced expansion

ProcessGTAW without filler wire addition

SIGNIFIC NT SPECTS

Material-Titanium

Large Qty of welding

Welding in position & at site

Materialsupply by Russians

TIT NIUM TUBES

Grade : ASTM B 338 Gr2

Tube Sheet : 35 + 5 mm thick

Material : ASTM A516Gr 70 + ASTMB 265 Gr 1 CLAD

ORBITAL WELDING


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ORBITAL WELDING

Why Titanium is used?

Provides excellent resistance to general and localized attack under

most oxidizing, neutral and inhibited reducing conditions inaqueous environments.

Corrosion Resistance due to stable, protective strongly adherentoxide film which forms instantly when a fresh surface is exposedto air moisture.

This film is transparent and not deducted by visual means.

Titanium resist corrosion by sea water to temperature as high as260 0C.

Even exposed to sea water for many years at a depth of over a mileshows no measurable corrosion.

Provides over 25 years of trouble free sea water service forchemical refinery de-salination and nuclear industries

ORBITAL WELDING


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ORBITAL WELDING

Has the ability to resist erosion by high velocity sea water

The presence of abrasive particles such as sand has only a small

effect on the corrosion resistance of Titanium

Production began in the late 1950s

Most widely used titanium is commercial pure (99.5 % Ti)

Manufacturing Process

Ingot slab Hot strip cold strip Slitting Forming TIG

Welding Stress relieving Eddy Current & Ultrasonic testing


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Tensile, flare, flattening & reverse flattening

Visual InspectionCleanliness, ID, OD, Surface condition, end condition

and marking.

Tube to tube sheet joiningContact Rolling (0 to 5 % wall thinning for a length of 10

mm)

Orbital WeldingFor highly reliable leak tightness

Forced Rolling (8 to 10 % wall thinning for a length of

25mm)

Physical Testing

ORBITAL WELDING

PROCESS FLOW CHART


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PROCESS FLOW CHART

Front / Rear end tube sheet cleaningwire

brush mounted in portable drilling machine

followed by acetone

Visual inspection

Titanium tube insertion

Initial cleaning before contact rolling

Initial contact rolling up to 10mm

Sh 1 of 3

PROCESS FLOW CHART CONTD


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End facing of tube & tube sheet up to 0.05 mm

Welding

Visual inspection

Rectification of repair work

Final expansion 8 to 10 % by lubricating

SAE 40 oil

Excess length trimming in the rear side

PROCESS FLOW CHART CONTDSh 2 of 3

PROCESS FLOW CHART CONTD Sh 3 f 3


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Tube tightness test by MAUS Gun G-150

Dye Penetrant testing

Final cleaning by acetone

PROCESS FLOW CHART CONTD Sh 3 of 3

TUBE SPECIFICATION


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TUBESPECIFICATION

TUBE INSERTION AT KODAMKULAM


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TUBE INSERTION AT KODAMKULAM


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FRONIUS MODEL - FPA 2000 (AUSTRIAN MAKE)

PROGR M BLE ORBIT L WELDING M CHINES

AFTER TUBE INSERTION


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AFTERTUBE I NSERTION

TUBE SHEET PROTECTION


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TUBESHEET PROTECTION

Welding parameters for FRONIUS MODEL - FPA 2000


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Welding parameters for FRONIUS MODEL - FPA 2000

Process : GTAW (Automatic )

No of weld passes 1Argon Gas flow rate 4 to 6 ltr /min

Pre Gas time T10 30 SecPost Gas time T11 30 SecPre Fusion current I21 90A

Pre fusion current time T21 0.1Sec

Pulse current I22 90ATime of pulse current T22 100msec

USE OF HYDRAUL IC OPERATED TORQUE CONTROLLED BOLT


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TIGHTNING KIT

OBJECTIVE

To adopt a safe State of the Art methodology in bolt

stretching of coupling bolts of TG Couplings.

GENERAL COUPLINNGS IN TG

HP Tubine to IP Turbine

IP Turbine to LP Turbine

LP Turbine to Generator Shaft

REQUIREMENT

The coupling bolts which are like pins, having a clearance of 0.03mm

diametrically, have to be stretched up to 0.55 mm ,depending on the bolt

dimensions to ensure uniform tightening .


G G


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TIGHTNING KIT

Prevalent practice

Nut of the Coupling bolt is tightened by a box spannerLeverage applied on end of the spanner by EOT crane through slings.

Differential expansion monitored by Dial Gauge positioned at bolt ends.

Sources of Error

Dial gauge at the nut end has to be fitted with a long extensionrod,which may lead to error in reading.

Disturbances in the nut also can lead to erratic readings.

Safety element

The whole stretching operation dependent on skill of the Fitter and

EOT Crane operator

Fine movements in EOT Crane not possible

Danger of slipping/shearing always present.


TIGHTNING KIT


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TIGHTNING KIT

RECOMMENDATION

Hydraulically operated Torque controlled Bolt tightening kit can be used.

Manufacturing Unit to specify Torque tightening values of individualcouplings.

ADVANTAGES

No error in reading.

Uniformity in bolt stretchingSafe for the working personnel

Safe for the equipment


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IMPROVED PROCESSES

ALL -VOLATI LE & OXYGENATED TREATMENT


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ALL VOLATI LE & OXYGENATED TREATMENT

`

AVT :The basic idea of AVT is to minimize corrosion &erosion corrosion in the low temperature region by

using deaerated high purity water with elevated PH.The actual PH range depend on cycle metallurgy

In absence of Oxygen, the primary reaction of iron

dissolution is inhibited by increasing PH.

The solubility of ferrous hydrazine rises with increasein temperature and then decreases with steep drop to

the solubility of magnetite between 200250 0C. This

results in undesirable magnetite deposit in this

temperature range.



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`

To maintain the solubility of ferrous hydroxide in feedwater below or equal to that of magnetite at 250 0C and

to exclude the possibility of over saturation, a minimumPH of 9.6 should be maintained. A PH of 10 would beeven better.

Hydrazine acts both as a O2scavenger & corrosioninhibitor by formation of ferrous oxide hydrate.

OXYGENATED TREATMENT :This process uses oxygenated high purity water tominimize corrosion & erosion corrosion in the feedwater train.

Oxygen, Hydrazine peroxide, air are used as

oxidants



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`

Oxygen level should be 30-50 ppb for drum units and 30-

150 ppb for Once Through Units.

Ph level shall be 9-9.6 at Drum units and 8-8.5 for OnceThrough Units

In oxygenated system, p rotective layer consists of

Magnetite(FE3O4) and Hematite(FE2O3) layers

For temperature ranges upto 250 0C the addition ofoxygen allows the formation of oxide protective layer which

have a very low corrosion product release rate in the

following water



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ALL VOLATILE TREATMENT (AVT)

Ferrous or mixed feedwater train

Cation conductivity 0.2-0.4 S/cm pH 8.89.6 (Dependent on feedwater metallurgy)

Fe 10ppb N2H4 ( >3x02)

O2 30 ppb )NH3 ( 20 -70 ppb )

OXYGENATED TREATMENT (OT)All ferrous feedwater trainCation conductivity < 0. 15 S /cmpH 8.08.5

HP

HeatersBoiler BFP DA LP Heaters CP CEP CondenserHP

HeatersBFP

LP BYPASS SYSTEM


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LP BYPASS SYSTEM

LP BYPASS SYSTEM

MODIFICATION CARRIED OUT IN OLD LPBPSYSTEM

In case of Turbine trip, direct command will beissued to LP Bypass valves for opening upto 45%for 3 secs.

It is expected that within this 3 secs., the sprayvalves will open and the spray water pressure will beachieved.

However, if the spray water pressure has not

reached a value of 5 kg/cm2 within 3.5 secs., or thecondenser wall temperature has become more than90 0C, the LP Bypass trip command will be issued

LP BYPASS SYSTEM


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SS S S

The sensing of pressure is done by installation ofadditional pressure transmitters at the downstream

of spray water valves The modification was implemented first in

Vindhyachal U#10 and two occasions since themodification, the turbine has tripped and LP Bypassvalves opened within 5 secs thereby saving theboiler trip

LBPB SYSTEM FOR NEW 250 MW SETS

To address this issue, now BHEL, Hwr has gone for

a new High Pressure LP Bypass system which hasmuch better response time. Such system have beensupplied at 1 x 250 MW Parli, 1 x 250 MW Paras, 4 x250 MW JPL and 2 x 250 MW Bhilai sites.

LP BYPASS SYSTEM


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The logic provided for the operation of the LBBypass valves are similar to that of the older low

pressure LPBP valves. However, the following arethe new features of High Pressure LPBP valves

The LPBP valves on sensing increase HRHPressure, automatically opens without looking for

adequate water pressure

For the water injection spray control valves, twocurves have been implemented, one for control andthe other for protection based on down stream

pressure of LPBP valves.

LP BYPASS SYSTEM


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SS S S

If the actual water injection flow is less than flowcorresponding the protection flow, then the LPBP

valves closes on water injection flow protection.

The following problems have been noticed in the newsystem

As per the water injection curve, a continuous waterflow is required to the system which is unnecessaryand wasteful.

The spray water flow element and flow transmitter is

showing 0 reading upto 50% of spray control valveopening.

The problem has been taken up with BHEL, Haridwar

LP BYPASS SYSTEM


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Conclusions :

The new High Pressure system is working satisfactorilyand therefore, the boiler tripping due to reheaterprotection in the new system has been avoided in therecently commissioned units.

By implementing the modification in the old units asdone at NTPC Vindhyachal U#9, 10, the problem of theold units can also be resolved.


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BEST PRACTICES

Best Practices, TSX PSWR


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CARD BOARD BLASTING OF LUB OIL AND CONTROL

OIL LINES OF STEAM TURBINESGENERAL PRACTICE

Only mechanical cleaning is done before start of oil flushing forlub oil and control oil system of steam turbines.

BEST PRACTICE

Exhaustive card board blasting along with mechanical cleaningis carried out for all the control and lub oil system before start ofoil flushing.

This practice is being followed in almost all the sites now.

ADVANTAGES

Effective cleaning and time reduction.

,



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USE OF PORTABLE CENTRIFUGE DURING LUB OIL

FLUSHING OF ROTARY MACHINESGENERAL PRACTICE

Generally oil flushing were carried out at ambient temperaturewithout any centrifuging arrangement for rotary machines such

as BFP, ID Fans, FD Fans and Mills.BEST PRACTICE

Oil flushing is carried out with portable oil centrifuge having in-built heating arrangement .

ADVANTAGES

Effective cleaning and time cycle reduction.

,



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CHEMICAL CLEANING OF PRE BOILER SYSTEM WITH

CEPGENERAL PRACTICE

Carried out by using temporary pumps, tanks and piping alongwith boiler acid cleaning setup

BEST PRACTICE

Existing CEP and Hotwell are used for the purpose of circulationin the entire system

ADVANTAGE

Effective cleaning of the entire system with minimum number oftemporary loops

Cost and time cycle reduction



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USE OF DEAERATOR AS MIXING TANK FOR PRE-

BOILER FLUSHING

GENERAL PRACTICE

Mixing tanks and associated pipings are arranged for carrying

out the pre boiler flushing activities.

BEST PRACTICE

For industrial sets, Deaerator itself is used as mixing tank for

carrying out chemical cleaning of pre-Boiler system.

This results in cost and time cycle reduction.

,



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CHEMICAL CLEANING OF BOILER (WW, SH) AND MSLINES IN INDUSTRIAL PROJECTS

GENERAL PRACTICE

Stages are : Alkali boilout, Acid cleaning and passivation

BEST PRACTICE

Alkali flushing, Citric acid cleaning, passivation of the entiresystem

ADVANTAGE

Chemical cleaning activities can be completed even before Boilerlight up

Since both SH and MS lines are acid cleaned & steam blowingcycle is considerably reduced




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CHEMICAL CLEANING OF HSD AND NAPHTHA LINES INCCPP

GENERAL PRACTICE

Cleaned by card board blasting

BEST PRACTICE

Citric acid cleaning with passivation

ADVANTAGE

Where the length of HSD and Naphtha lines is more than 500meters cardboard blasting shall not be very effective. Hence,

citric acid cleaning is a most effective way of ensuringcleanliness of the entire piping

Time cycle reduction and trouble free operation



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USE OF THERMIC FLUID HEATER FOR COMMISSIONINGACTIVITIES IN GREEN FIELD PROJECTS

GENERAL PRACTICE

Auxiliary boiler is used for generation of steam for pre-

commissioning activities like flushing of Boiler Feed Line,Condensate Lines, Drip Lines etc.

BEST PRACTICE

Thermic fluid heater is used in green field projects in place ofauxiliary boiler for carrying out chemical cleaning activities.

This results in cost and time saving.



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ACID CLEANING WITH EDTA

GENERAL PRACTICE

Generally HCL is used for acid cleaning of main boiler.

BEST PRACTICE

HCL is replaced by EDTA for all green field projects especially,where auxiliary steam is not available.

This is safe, environment friendly and reduces time cycle.



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PROVISION OF ADDITIONAL INTERSTAGE VALVES FOR

STEAM BLOWINGGENERAL PRACTICE

Interstage valves are not used during steam blowing operationsresulting in three to four days shut down for start of subsequent

steam blowing operations.

BEST PRACTICE

Additional temporary valves are used at Main Steam HP Bypass

lines, CRH Lines during steam blowing operations.

This has resulted in cycle time reduction.



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CONTINUOUS STEAM BLOWING IN CCPP

GENERAL PRACTICE

Puffing method is used due to limitation of fuel firing system

BEST PRACTICE

Continuous blowing method (30 minutes) is used in stages

ADVANTAGE

Effective cleaning and time cycle reduction



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HIGHER STEAM BLOWING PARAMETERS

GENERAL PRACTICE

Steam blowing is carried out at 40 Kg / sq cm and 300350 deg C

BEST PRACTICE

Steam blowing carried out at 50 Kg / sqcm and 370400 deg C

ADVANTAGE

Effective cleaning due to higher disturbance factor at elevated

parameters Time cycle reduction



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USE OF FRESH LUB OIL BOTH FOR FLUSHING AND REUSE

IN ALL INDUSTRIAL SETS

GENERAL PRACTICE

Flushing oil is used for oil flushing operation, fresh oil is used for

normal operationBEST PRACTICE

After cleaning of entire lub oil system by cardboard blasting freshoil is used both for flushing and normal use

ADVANTAGE




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AIR LEAK TEST OF LUB OIL, CONTROL OIL, AND

CONTROL FLUID SYSTEM

GENERAL PRACTICE

No separate test conducted before start of flushing resulting inleakage of oil / fluids

BEST PRACTICE

Entire system is pressure tested with compressed air at 5 to 6Kg/sqcm before start of flushing operation

ADVANTAGELeakage of oil and control fluid is minimised




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GENERATOR SEAL OIL FLUSHING

GENERAL PRACTICE

Seal oil flushing is done for the site erected pipes upto the inletnozzle in the end shield

BEST PRACTICE

Pre-fabricated pipes from the end shield upto seal ring inlet arealso included in the final stage of flushing.

ADVANTAGEAvoids damage to Generator seal from the entrapped foreignmaterial.



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HYDRAULIC TEST OF LUB OIL, CONTROL OIL AND

SEAL OIL LINES

GENERAL PRACTICE

Jacking oil pumps were used for carrying out hydraulic test of luboil, control oil and seal oil line after flushing.

BEST PRACTICE

AC seal oil pimp is used for the purpose of hydraulic test of theabove system.

ADVANTAGEAvoids damage to Jacking oil pumps.



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CONDENSER MASS FLUSHING

GENERAL PRACTICE

Cleaning of condenser is normally carried out during steamdumping operation

BEST PRACTICE

Condenser tubes are thoroughly flushed through high pressurejets (fire fighting water) before commissioning of CEP

ADVANTAGE

Duration of steam dumping operation reduced




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CLEANING OF VACUUM PUMP SUCTION LINES

GENERAL PRACTICE

No structured cleaning is envisaged except draining the systemthrough drain valves (NB50) during initial commissioning ofvacuum pumps

BEST PRACTICE

Vacuum pumps suction lines are throughly cleaned throughcardboard blasting before commissioning of vacuum pumps

ADVANTAGE

Smooth trouble free operation

Damage of vacuum pumps due to entry of foreign material isavoided



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OLTC COMMISSIONING

GENERAL PRACTICE

OLTC is commissioned normally after attaining continuousoperation of unit, i.e., CW system has been put into service forprolonged period

BEST PRACTICE

OLTC is commissioned either

Immediately after running of CW pump or

Before conductance of PG test after thorough cleaning ofcondenser tubes

ADVANTAGE

Collection efficiency of balls increase

Trouble free condenser operation



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SELF CONTAINED BEARING COOLING ARRANGEMENTAT EPC PROJECT

GENERAL PRACTICE

Lub oil coolers for ID, FD and PA Fans are kept charged throughthe bearing cooling water system

BEST PRACTICE

In EPC project where due to certain circumstances there is adelay in commissioning of Cooling Water system a separate selfcontained cooling arrangement (Sintex tank, pumps and suitablehoses) to facilitate initial commissioning

ADVANTAGE

Trial operation of all major boiler auxiliaries can be completed bythis method leading to time cycle reduction



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PRE ERECTION CHECKING OF BUS-DUCTS

General Practice

Bus-ducts are cleaned and erected

Commissioning jobs taken up later

Best Practice

While at ground, check tightness of all electrical connections ofheaters, thermostats etc

Check heaters healthiness and adjust thermostat tripping pointseasily now

Check drain pad holes before lifting so that any corrections, if

required can now be done easily

Trial assembly of Bus-duct structure on ground before erection

Avoids difficulty in commissioning / troubleshooting



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TURBINE X-CRITERIA

General Practice

In X1 criteria for turbine rolling, main steam inlet temperature toturbine has been used for criteria calculation. During any boiler trip

and restart, X1 criteria gets fulfilled even though boiler outlettemperature is less. This leads to cold steam entering the turbine.

.

.Best Practice

Additional criteria X11 introduced using Temperature before HPbypass.



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ADDITIONAL TRIPPING DURING ATT

General Practice

Tripping criteria during conductance of ATT does not include manyvital trip inputs

.

.Best Practice

Conditions like MFT, Turbine Bearing temperature VH, axial shift VH,vacuum low, cold gas temp trip, seal oil temp trip etc are added



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COMMISSIONING OF ATRS, ATT & AUTOSYNCHRONIZER

General Practice

Normally, ATRS, ATT and Auto-synchroniser are getting commissioned aspending points and not as a part of normal plant commissioning.

So after the pending point is cleared, customer is normally not using the

system.

Best Practice

We are putting efforts for commissioning these system in the first rolling

synchronisation itself.

Recently at Bhilai and Tata Trombay, ATRS and Auto-synchroniser have

been commissioned during first few start-ups.

At Tata Trombay, ATT is also commissioned.



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DC EOP AND SOP LATCH RELAY

General Practice

Lub Oil pressure low switch starts DC EOP through max systemSLC latch relay contract..

.

Best Practice

SLC latch relay contract in DC EOP and SOP cabinet looped so thatlub oil pressure low switch contact starts DC EOP and SOP directly,

bypassing MAX system SLC ON. This safeguards machine in the event of AC as well as failure of max

system



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AUTOSYNCHRONIZATION

General Practice

As per circuit configuration, auto synchronizer after fulfilling its setcondition directly closes the Generator circuit breaker..

.Best Practice

Additional contact of check synchronization relay wired up in autosynchronization circuit. Here autosynchroniser setting arecoordinated with setting of check synchronizing relay so thatautosynchroniser and check synchronization relay operates at thesame time.

This helps in safeguarding the machine during malfunctioning ofautosynchronizer.



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AUTOSYNCHRONIZER TESTING

General Practice

As per normal practice, autosynchronizer is tested and its outputcommand is verified within the panel terminals..

Best Practice

Autosynchronizer is tested in cold condition with supply of PTvoltages through injection kit and actual Generator breaker closing(ensuring that isolators are open)

This helps in optimization of autosynchronizer setting morecorrectly and also total circuit gets checked.



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USE OF MULTIPLE FILTRATION MACHINES FORTRANSFORMER DRYOUT

General Practice

One Oil filtering machine (about 6 KL capacity) engaged for dryout

Best Practice More than one such machine put in parallel operation to optimally

utilise transformer drain header flow capacity

Advantage

Cycle time reduced around 50%



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TURBINE BEARING METAL TEMPERATURE CHECKING

General Practice

As per normal practice, cabling from bearing metal temperature JBto control room/Cold Junction Compensation(CJC) JB are checked

after installation of thermocouple in bearings...Best Practice

Before installation of thermocouples in bearing, signal upto DCSchecked by heating the thermocouple tag wise.

This ensures correctness of connection, readings and alsoambiguity of polarity change is avoided.



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DAVR DUMMY LOAD TESTING

General Practice

As per normal practice, the AVR/DAVR dummy load testing iscarried out at site with the help of 500W lamp or any available

resistive load...Best Practice

Dummy load testing is carried out with same type of resistive load

which is identical in ratio to that of factory testing. With this type oftesting, exact and identical readings with factory can be ensured.

Customer as well as commissioning engineer gets betterconfidence on DAVR working.



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PAINTING OF TRANSFORMERS AND BUS-DUCTS

General Practice

Painting works for busducts and transformers are attempted atvery late stages

Becomes difficult because of shutdown requirement and thusopportunity may not be there

Best Practice

At least Station transformer and its busducts may be paintedimmediately after erection completion (before first charging).This transformer hardly goes into shutdown later

Better to paint the other transformers and busducts as well assoon as possible before charging

However, customer opinion / permission may be required sincethey may insist on painting only after all works are completed



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SEQUENCE STARTUP OF HT DRIVES

General Practice

All HT drives are generally started individually during firstcommissioning of the drives

This lead to a pending point as we do not get suitable opportunity tocommission the HT drives in sequence mode

Best Practice

All the HT drives to be started in sequence during first startup of the

any HT drive


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Introduction


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Implementation of Best Practices during Overhauling

of T.G. has resulted into the following -

Overhauling cost reduction.

Reduce overhauling periods.

Improvement in quality.

Introduce latest technologies.

Improve customer satisfaction

Implementation of Best practices


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Use of latest technology like induction heating for dismantling andassembly of turbine.

Unit de-synchronization at 480 C of HP shaft temp by decreasingthe load before shut down..

Turbine oil pump stop at 125C (HPS temp).

Barring gear stop at 125C (HPS temp).

To initiate overhauling activities as soon as machine comes tobarring gear.

Decoupling of Generator rotor from turbine rotor and put backturbine rotor in barring.

Start dismantling of generator and O/H activities thereafter.

Review by Site and follow-up from HQ


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Site reviews all activities minutely

Time taking processes, idle times between activities, delay in

arranging spares and mobilization of experts from units etc

are identified well in advance.

HQ also involves in reviewing processes and all important

issues and HQ inputs are duly incorporated on activity

planning at site.

Reduction in overhauling duration to the target schedule is

attributed to meticulously planning and follow-up of critical

activities, which is accomplished in a shortest duration.

Strategic Planning


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List out the History of past problems

Pre-overhaul survey record.

Analyze Present running behavior.

Input from MOUs and utilities.

Timely arrange experts service from MOUs

Milestone based review.

Mobilization of resources 3 days before start of Overhaul.

Scheduling of sequential & parallel activities

Identification of idle time & to avoid them by detailed planning inadvance

All the anticipated spares required for completion of theoverhauling work arranged at T.G. Floor before start of the work.

Generator work starts within 36 hrs of De-synchronization


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0000 hrs : De-synchronization (HP shaft temp at 480 Deg.C)

17.5 hrs : Barring gear stop (HP shaft temp at 400 Deg C)

17.5 hrs. to 20.5 hrs:

AOP stop

Lub o i l to b rg. 5,6,7 blanked & brg . 4 min im ized

LP-Gen coupl ing decoup l ing

Hand barr ing w i l l con t inue dur ing th is per iod

20.5 hrs : B/G re-started

With this practice Generator rotor thread out work startswithin 36 hrs of de-synchronization.

Procedure for decoupl ing of LP-Generator in hot conditions


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Turbine is on Turning Gear. JOP in service, AOP in service.

Loosening of pedestal cover bolts, removal of Vibration probes.

Close turning gear valve to reduce the speed. Simultaneously

loosen and remove pedestal cover bolts.

When Turbine speed becomes zero. Stop AOP while JOP is

continuously kept in service. Continue Hand Barring.

Remove pedestal 4 cover. Close Lubricating oil throttle valve to

the minimum possible.

Simultaneously blank lub oil supply to bearing 5,6 and 7 by putting

gasket in lub oil supply line. (parallel, by 3 gangs). Keep watch on

bearing 1,2 and 3 metal temperature and simultaneously do hand

barring.

Procedure for decoupl ing of LP-Generator in hot conditions


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Put tin sheet/polythene to cover on bearing 4. Start EOP andcontinue hand Barring.

Loosen LP-Generator coupling bolts and decouple LP-generatorby continuing hand barring.

Shift generator rotor away from turbine Stop EOP and Adjust brg. 4lubricating oil throttle valve to normal. Put pedestal cover backand start EOP & barring gear.

Dismantling & prepare for rotor thread out.

At the time of rotor thread out, stop turning gear again and stopEOP. Remove pedestal 4 cover.

After thread out put pedestal 4 cover back. Turbine on Barring

gear with AOP in service till HP shaft temp comes to 125 deg C .

Note: Jacking oil pump is throughout kept in service.

PSWRs Best records on TG overhauls


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Overhauling of IP-LP Turbine & Generator including LP Turbine

blades MPI have been carried out in record lowest time of 8

days barring to barring. (13 days Bar to Bar) on year 2007 at250MW U#2 Dahanu TPS.

Overhauling of LP Turbine & Generator have been carried out in

record lowest time of 9 days barring to barring. (15 days Bar to

Bar) on year 2005 at 250MW U#2 Dahanu TPS . This was achieved

as an exceptional case to avoid power problem in Mumbai.

Overhauling of HP- LP Turbine & Generator including HP rotor

replacement & HP/IP coupling hole reaming, LP free standing

blades MPI & NFT along with bearings 1,2 & 4 replacement have

been carried out in record lowest time of 13 days baring tobarring. (18 days Bar to Bar) on year 2006 at 250MW U#1 Dahanu

TPS.

PSWRs Best records on TG overhauls


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Overhauling of IP-LP Turbine & Generator including LP

Turbine blades MPI & NFT have been carried out in record

lowest time of 12 days barring to barring. (17 days Bar to Bar)in year 2008 at 250MW U#2 Dahanu TPS.

Unit-3 HP Module overhauled in 14 days barring to barring

(19days bar to bar) in year 2006 at 200MW U-3 KSTPS NTPC

Korba.

Capital Overhauling of HP-IP-LP Turbine & Generator

including HP rotor replacement & HP/IP coupling hole reaming,

LP free standing blades MPI & NFT have been carried out in

record lowest time of 35 days barring to barring in year 2008 at500MW U#8 NTPC VSTPS Vindhyachal .

Schedule comparison


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Sl.

No Capacity (MW)

Capital Overhauling TG SET (Barring to Barring)

Previous Best Record Present Record

1 500

(All three module +Gen)

36 Days Unit-6, NTPC,KSTPSKorba on year 1996

35 days Unit-, NTPC, VSTPSVindhyachal on year 2008

2 250(HP-LP&GEN)

30 Days Unit-U-2 REL, DahanuTPS on year 2002

13 days Unit-U-2 REL, DahanuTPS on year 2006

3 250

(IP-LP&GEN)

- 8 days Unit-U-2 REL, DahanuTPS on year 2007

4 200/210

(HP Module)

28 Days Unit-2 NTPC KSTPSon year 2001

15 Days Unit-3 NTPC KSTPSon year 2006

Conclusion


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A benchmark on record minimum duration in KWU design TG setoverhaul could be achieved.

It was the determination, commitment, monitoring and follow-up ofassociated activities that ascertained to achieve a challengingtarget.

Working out activities well in advance with subcontractor

agencies/ partners and round the clock execution of job with newstrategies helped to meet schedule deadlines.

Work can be started as soon as machine comes to Barring gear.

Cooling Down period can be saved relatively by 4 days during the

Generator overhauling.


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IMPROVED SITE FACILITIES

Porta Cabins - to overcome delay in site mobil isation


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Award of Enabling works and its construction takes considerable

time, after receipt of confirm order. This delays posting of site

staff and material management including posting of ConstructionManager.

PSWR has decided to procure Porta Cabins with all amenities as

replacement of Conventional Site office sheds.

This will be provided in all new sites like Satpura, Mauda,Chandrapur, Raigarh, Vindhyachal, Bela Ideal Energy including

all forthcoming sites.

NIT has been floated and tender is likely to be finalized by end

April 2009.


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Porta Cabins - to overcome delay in site mobil isation


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Advantages of Porta Cabins

1. Quick mobilization

2. Quick realization of mobilization advance from customer

3. Quick demobilization

4. Flexibility in use & can be installed as per the site condition

5. Environmental friendly due to cleanness & easy maintenance

6. Provide better facility to site staff

7. Light weight (Easy in handling and transportation)

8. Aesthetic look.

9. Durable and Termite proof

10. Seismic-resistant11. Economical in long term because of repetition

12. Thermal Insulation


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Tech. Day Presentation.ppt

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