200MW Trainig Simulator Volume 2

8/7/2019 200MW Trainig Simulator Volume 2

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KORBA SIMULATOR 1



KORBA SIMULATOR 2



KORBA SIMULATOR 3



KORBA SIMULATOR 4

CONTENTS

CHAPTER NO. TOPIC PAGE NO

1. CHARGING OF ELECTRICAL SYSTEM 7-11

2. CONDENSATE AND FEED WATER SYSTEM

CEP OPERATION 15-20

BFP OPERATION 21-28

3. BOILER SYSTEM

AUXILIARY PRDS CHARGING 31-32

HEAVY FUEL OIL SYSTEM CHARGING 33-34

FSSS LOGICS 35-74

AIR PRE-HEATER OPERATION 75-78

ID FAN OPERATION 79-84

FD FAN OPERATION 85-88

FURNACE PURGE 89-91

BOILER LIGHT UP 92-96

PA FAN OPERATION 97-102

PULVERISER OPERATION 103-108

4. TURBINE AND GENERATOR SYSTEM

VACUUM PULLING 111-1

HP/LP BYPASS CHARGING 115-116

TURBINE START-UP 117-12

TURBINE ROLLING 121-12



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GENERATOR SYNCHRONISATION 125-128

UNIT SUPPLY CHANGEOVER 129-130

LP HEATERS CHARGING 131-132

HP HEATERS CHARGING 133-134

SH/RH STEAM TEMPERATURE CONTROL 135-136

SOOT BLOWING OPERATION 137-139

5. UNIT COLD START-UP 141-156

6. UNIT HOT START-UP 157-162

7. AUTOMATIC TURBINE RUN-UP SYSTEM (ATRS) 163-208

SGC OIL SYSTEM 171-182

SGC TURBINE SYSTEM 183-208

8. UNIT PLANNED SHUTDOWN

BOILER SHUTDOWN 211-212

TURBINE SHUTDOWN 213-215

GENERATOR SHUTDOWN 216

9. EMERGENCY HANDLING 217-255

10. EFFICIENCY ASPECTS OF POWER PLANTS 257-288

11. SIMULATED MALFUNCTION LIST 289-296

12. APPENDIX

BOILER STARTUP CURVES 299-306

TURBINE STARTUP CURVES 307-317



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CHARGING OF ELECTRICAL SYSTEM



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CHARGING OF ELECTRICAL SYSTEM

UNIT POWER SUPPLY: SINGLE LINE DIAGRAM

ACTION OBSERVATIONREMARKS

1. ENSURE all thefollowing conditionsare satisfied, beforecharging the unit

HT/LT buses.

- ADEQUATE service air pressure is availablefor 400 KV breakers

(30 Kg/cm2 )

- Local check/ operation.Not simulated.

- Bus section coupler on400 KV lines isCLOSED

- Switchyard check.

- Bus-coupler on 33 KV Bus in OPEN.

- Switchyard check &operation



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- Tie Xmers 1 & 2 areCHARGED from 400KV and 33 KV sides.

- Switchyard operation.Not simulated.

- 33 KV bus voltage isNORMAL.

- Switchyard check.

- 220 V DC supply is AVAILABLE.

- Switchyard check.

- All the protections areHEALTHY and inSERVICE.

- EMD Engineer'sclearance, required.

- Bus couplersconnecting buses SA &SC and SB& SD areOPEN.

- Not simulated.

- Station transformer'sincoming breakersfrom 33 KV busesoutgoing to 6.6 KV

buses (SA, SB, SC &DC) are CLOSED.

- Not simulated.

"Power available"indications are ON, toall the four station

buses (SA, SB, SC &SD).

- Common StationSupply Auxiliary Electrical Panel.C.S.S.A.E.P.

2. CLOSE both the HT (6.6 KV) incomer

breakers to unit auxiliary buses 1-A and 1-B from station

buses SA & SB.

Buses I A and I B get charged and their

voltages come to 6.6KV , " 6.6 KV bus

volts/ VT trouble",alarm gets reset.

UCB Operation/check.

3. CLOSE the H.T. side breakers and then L.T.side breakers of theunit servicetransformers (UST).

- Bus sections LA andLB get charged andtheir voltages come to415 V (approx.)

- UCB indications.

- USTs in rush current momentarily shoots upmeter pegs out anddrops to no load value.

- UCB indication.

- All the "power/control - UCB annunciation.



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supply fault" and"UATs cooler/ OLTCtrouble and "415 V

boiler/turbine MCCfault" annunciationsreset.

4. CLOSE the normaltiebreaker to ACemergency section.

- AC emergency sectiontie breaker getscharged and voltageshows 415 V (approx.)

- UCB operation

- All annunciationspertaining toEmergency MCC get reset.

- UCB indications

5. CLOSE the incomer breakers to ESP &lighting Xmers.

- "ESP switch gear trouble" alarm getsreset.

- UCB indication.



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KORBA SIMULATOR 12

CONDENSATE AND

FEED WATER SYSTEM



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CEP OPERATION

PRE-START CHECKS OF CEP

CONDENSATE SYSTEM

ACTION OBSERVATION REMARKS

1. CHECK if all start permissive for startingCEP is satisfied.

- CEP suction valvesMC-1/MC-2 are OPEN.

- Local operation.

- Hot well level is ADEQUATE (300 mm wcl.)

- UCB indication. Also to be locally checked.

- Bearing temperature of

CEPs is NOT HIGH 600 C.)

- UCB indications and

also to be locally checked

- CEP re-circulation valve MC-33 is OPEN100%.

- Hotwell level controller output is zero.



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- CEP discharge valvesare CLOSED (MC-5/MC-6).

- UCB operation.Interlock, beforestarting the first CEP.

2. CHECK that CEPs arelocally lined up for starting.

- Condensate pumpgland sealing water-isolating valve isOPEN.

- Local operation. Not simulated.

- Condensate pumppriming (pressureequalising) valve isOPEN.

- Local operation Not simulated.

- CEP bearing cooling water line isolating valve is OPEN.


- CEP bearing oil level isadequate.

- Local check.

- Local emergency push button is released.

- Local operation check.

- CEP electrical supply is AVAILABLE.

- Breaker is inService/Remoteposition.

3. ENSURE condensatesystem is lined up

before starting CEP.

- Main ejectorsinlet/outlet- valves areOPEN (MC-11/MC-12and MC-13/MC-14).Bypass valve (MC-15)is closed.


- Gland steam cooler inlet/outlet valves MC-19/MC-20 are openand bypass valve (MC-21 is CLOSED.


- LPHs (1-2-3) inlet/outlet valves (MC-61/MC-63, MC-67/MC-68, MC-72/MC-73)are CLOSED.

- Local operation(Remote function).

- LPHs (1-2-3) bypass valves (MC-64/MC-69/MC-74) are OPEN.

- Local operation. LPHsare bypassed initially to minimise corrosion.



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- Deaerator inlet valve(MC-75) is OPEN.

- Local check Not simulated.

- CEP header vents andline vents OPEN.


- HW level controller, DA level controller andcycle make-upcontroller valves areCLOSED. (MC-27,MC-41 and MC-55)

- UCB operation andcheck.

- Bypass valves of HW,DA and cycle make-upcontrollers (MC-28/MC-42/MC-55respectively) are alsoCLOSED.

- UCB operation andcheck.

- Local operator intimated prior tostarting of pump.

- Use plant PA system toinform the operator.

GLAND STEAM COOLER AND EJECTOR CONNECTIONS



KORBA SIMULATOR 17

STARTING PROCEDURE OF CEP

WHEN BOTH THE PUMPS ARE OFF

ACTION OBSERVATIONREMARKS

1. CHECK before startingany condensate pump. - All pre-start checks areOVER. - Local /UCB checks &operation

- All permissive are AVAILABLE.

- Associated saffronlamps on.

2. START the CEP motor. - CEP starting current comes down to 20A after 5 sec.

- UCB ammeter indication.

- CEP dischargepressure increases to

25 Kg/cm2. Approx.

- UCB indication.

- CEP's discharge valves(MC-5 MC-6) open100%.

- Associated red lampscome on.

3. CLOSE the air vents oncondensate lines.

- The air vents arelocally closed.

- Local operation Not simulated

4. LOAD the condensatepump by opening MC-27.

- CEP current startsincreasing

- UCB ammeter.

- CEP dischargepressure decreasesproportionately.

- UCB check.

- Condensate flow toD/A starts increasing

- UCB indication.

5. INSTRUCT the localoperator to check

bearing temperaturesand vibrations.

- Limiting values of bearing temp and vibrations are:

- UCB OMNIGUARD brgtemp and vibrationindicators must beregularly checked.

Alarm TripBearing Temperature 75 oC 90 oC

Vibration 40 microns 75 microns



KORBA SIMULATOR 18

6. CHECK that thesecond condensatepump is ready for starting and isavailable on STANDBY.

- Breaker control switchis on 'Normal After Stop' position.

- UCB control switch on'off' position

- Pump OK standby - All permissive areSATISFIED.

- UCB check.

- All local line ups areCOMPLETE

- Refer to pre-start checks list.

WHEN ONE PUMP IS RUNNING


1. CHECK before-starting the secondcondensate pump that all these conditionsare satisfied.

- All pre-start checks areOVER.

- UCB/local check.

- All permissive are AVAILABLE

- All associated saffronLAMPS ARE ON.

2. START the CEP motor - CEP motor breaker gets closed.

-

- CEP discharge header pressure improves a little.

At a dischargepressure of 17.5

Kg/cm2., the standby CEP can take start

automatically.

- The motor current of the other CEP dropsslightly.

- CHECK bearingtemperatures and

vibrations locally.

- Bearing temperaturesand vibration limits are

- UCB OMNIGUARDand vibrationindicators must bemonitored regularly.

Alarm Trip

Bearing Temperature 75 oC 90 oC

Vibration 40 microns 80 microns



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CEP SHUTDOWN PROCEDURE



1. Start the other CEP if it is available. - Discharge pressureimproves slightly - Maintain hotwell levelapprox 500 mm wcl.

- MC-27 closes slightly on auto.

2. STOP the first condensate pump.

- Discharge pressurefalls slightly.

- Hotwell level HI alarm isat 600 mm wcl.

3. CLOSE the suctionand discharge valves.If any maintenance is

to be carried out,rack-out the motor breaker.

- Suction anddischarge valveclosed indication

comes on.

- Hotwell level LO Alarm400 mm.

- Hotwell level LO-LO Tripis at 250 mm wcl.

WHEN BOTH PUMPS ARE RUNNING


1. TRANSFER MC-27control to MANUAL and CLOSE it to 20%approx.

- Manual mode onindication comeson.

- M/A release push button must be pressedfor all auto/ Manualchange over.

- Discharge header pressure goes upslightly.

STOP the CEP motor. - The dischargeheader pressuremay tend to drop

further.

- If required, close MC-27more to maintaindischarge header

pressure.



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BFP OPERATION

PRE-START CHECKS OF BFP


1. CHECK all theBFP start permissive issatisfied beforestarting any BFP.

- Deaerator level is ADEQUATE (700 mm wcl)

- UCB indication, alsocheck locally.

- BFP suction valve (FW-1/FW-2/FW-3) is OPEN100%.

- Local operation.UCB permissiveindication. Not simulated

- BFP booster pump suctionpressure is ADEQUATE

(>3.0 KSC)

- Local check. UCBindication for

permissive.

- BFP pneumatic re-circulation valve (FW-8/FW-9/FW-10) is 100%OPEN.

- Re-circulationcontroller output is100% and valveopen indicationavailable.

- BFP manual re-circulation valves at the Deaerator are100% OPEN.

- Local check only.Not simulated.

- BFP cooling water pressure

is ADEQUATE 2.5 Kg/cm2

- Local operation andcheck.

- BFP bearing temperaturesare less than 60 OC.

- UCB and localCHECK Saffronlamp on indicationis available.

- BFP lub oil pressure is

ADEQUATE (2.0 Kg/cm2).

- AOP for the BFP ison and on "Remote".If not, start the AOP

from UCB.- BFP selector switch is on

NORMAL.- For UCB operation

(interlock).

- BFP scoop tube is onMINIMUM position.

- Operator check only



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2. CHECK that beforeBFP is locally LINED UP starting.

- BFP lub oil, working oiland seal water coolers arein CHARGED position. Allmanual valves for cooling

water to bearings areOPEN.

- Local operations.Not simulated.

- BFP motor air box cooling water-inlet/ outlet manual valves are OPEN.

- Local operation andcheck. Not simulated.

- BFP suction strainer DP is

0.2 Kg/cm2- Local check.

3. CHECK that feed water system islined-up (Requiredonly for the first

BFP to be started).

- All air vents on suctionand discharge lines of BFPand feed regulating stationare OPEN.

- Local check. Not simulated.

- Spray pressure control valves on HP bypass & AUX. PRDS station areCLOSED.

- UCB check only.

- Suction strainer drain valve is in CLOSEDposition.

- Local check.

- HPHs are in BYPASSEDcondition.

Group bypass valvesare in 'Bypass' mode

or individual HPHsBypass valves areopen.

- Feed regulating stationcontrol valve are inCLOSED position.

- UCB check.

- Economiser inlet valve E-2is open.

- UCB check only

- Header block valves onsuper heater and reheater

attemperation lines areCLOSED.

- UCB and localcheck.

- BFP local operator intimated before starting of BFP.



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FEED WATER SYSTEM

BFP STARTING PROCEDURE

WHEN BOTH PUMPS ARE OFF


1. CHECK before startingany BFP.

- All pre-start checks areCOMPLETED

- Local/UCBchecks.

- All BFP permissive are ON. - Associatedsaffron lampsare ON.

2. START the boiler feedpump motor.

- Breaker closed indicationcomes on.

- Red indicationON.

- Motor takes starting current

and then comes to no loadcurrent of 125 amps.approx.

- UCB check.

- BFP header discharge Pr.

increases up to 85 Kg/cm2.

- Associated red& green lampsare on

- Integral bypass valves of theBFP main discharge valve (FW-

- UCB indication.



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101/FW102/FW-103) start opening.

- After integral bypass valves arefully open, BFP main discharge

valve starts opening

- Interlock.

Suction flow increases to150 T/Hr. approximately.

- UCB check.

- Motorised cooling water valve,(BCW-72/98/124 startsopening.

- Suppliescooling water tomotor air box and working oilcoolers.

- BFP aux. oil pump goes off asthe main oil pump takes over.

- Interlock.

- Scoop control transfers to

AUTO with a time delay of 5secs.

- Interlock.

3. TRANSFER to manual &RAISE BFP scoop tubeposition to get desiredfeed water

- BFP discharge pressure rises. - If on auto BFPscoop tube can

be operatedthrough BFPmaster.

- Feed water flow through theBFP starts increasing above150 T/Hr.

- BFP header pr. low alarm getsreset.

- UCB indication.

- Re-circulation valve autorelease becomes available, if BFP flow exceeds 150 T/Hr.

4. OPEN feed regulatingstation low rangecontrollers isolating

valves

- Integral bypass valves of FW-99/100, A and B open up.

- UCB indication

- Main Isolating valves of FW-99/100 open up.

5. ADJUST re-circulationflow set point to 30%and TRANSFER controlto auto.

- Re-circulation flow set point isprovided above the recirculation

valve controller.

- M/A releasespush button for auto/ manualtransfer.



KORBA SIMULATOR 24

- Re-circulation valve controltransfers to auto.

6. INSTRUCT Localoperator to check

bearing vibration andtemperatures locally

- Various bearing temperaturesand vibration limits are:

- Monitor Brgtemp and

vibrationindicators.

Alarm Trip

Brg. temp. 95 oC 105 oC

Working oil outlet temp 95 oC 130 oC DAS/Local indication.

Vibration 9 mm/sec. 12 mm/sec. DAS/local point.

Motor wdg temp. 110 oC 135 oC



1. CHECKS beforestarting the secondBFP.


- UCB/local check,

- All BFP start Permissive is AVAILABLE.

- UCB check only.

- BFP main discharge valveOPEN.

- UCB check only.

- Aux. oil pump is ON and luboil pressure is ADEQUATE.

- IF not, start the AOP.

- BFP scoop tube position isMINIMUM

- UCB indication.

- BFP selector switch is onNORMAL.

- UCB check.

2. START the BFPmotor

- Breaker closed indicationcomes on.

- UCB indication.

- BFP scoop tube controller transfers to auto and followsmaster controller output.

- Interlock. UCBindication.

- Motorised cooling water valve, (BCW-72/98/124)open up.

- Interlock. UCBindication

- BFP aux. oil pump trips - Interlock.



KORBA SIMULATOR 25

automatically as the mainoil pump takes over.

3. ADJUST re-circulation flow set point to 30% and

TRANSFER controlto auto.

- Re-circulation flow controltransfers to auto.

- Re- circulation valvecontrol trips tomanual & opens100% if BFP flow drops below 130

T/Hr

- Re-circulation valvemodulates to maintain set re-circulation flow.

4. ADJUST scoops of the two runningBFPs to equaliseloads.

- BFPs discharge pr. flow indications must becomeapprox. equal.

- UCB check only.

5. ADJUST BFP biasto 50% and

ADJUST BFPmaster controller equal to BFPs scooptube position.

- BFP biasing set has beenprovided above BFP scoopcontrol.

- M/A release must bepressed for auto/manualtransfers

- Controller error on thescoop controls of therunning BFPs becomeszero.

6. TRANSFER runningBFP SCOOP controlto auto.

- BFPs scoop controlstransfer to auto.

- UCB indicationMaintain DP across

FRS 6-8 Kg/cm2.

7. Adjust FRS DP, set to 60% -80% and

TRANSFER BFPmaster control toauto.

- Controller error on BFPmaster Controller becomeszero, when actual& set

values of DP are matching

- UCB M/A releasepush button is to bepressed for auto/manual changeovers.

- BFP master trips tomanual if any of therunning BFPs trips or

individual BFPcontrol is changed tomanual mode.



KORBA SIMULATOR 26

BFP SHUTDOWN PROCEDURE


1. TRANSFER scoopcontrol of the BFP

to manual.

- Scoop control transfers tomanual.

- UCB indication.

- BFP master also transfers tomanual.

- UCB indication.

2. REDUCE scooptube controller of the BFP tominimum position.

- BFP discharge pressure andflow start decreasing

- If needed, start thestandby BFP, or reduce unit load to80 MW - 100 MW.

3. STOP the BFPmotor.

- BFP motor breaker opens. - Associated greenlamp comes on.

- BFP re-circulation valveopens 100%

- UCB indication.

- Motorised cooling water valvestarts closing.

- UCB check only.

- If no other BFP is in servicethe discharge valves of allBFPs start closing.

- Interlock.

4. Close the BFP

suction valve andrack out breaker if any maintenance to

be carried out.

NOTE:- Before closing the suction valve, please ensure that discharge valve isclosed & there is no passing in the discharge valve and NRV. Otherwise,due to back pressurising booster pump glands may fail, leading to leakagesetc. Watch for any increase in suction pressure when closing suction valve.



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SINGLE ELEMENT FEEDWATER CONTROL

THREE ELEMENT FEEDWATER CONTROL



KORBA SIMULATOR 28

BOILER SYSTEM



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KORBA SIMULATOR 30

AUXILIARY PRDS CHARGING


1. CHECK theseconditions are satisfied

before charging theaux. steam header.

- Station start-up boiler has been started

already.

- Refer to theoperating instruction

of the Aux. Boiler.Not simulated.

- Aux. steam isolating valve S-16 and its bypass from aux. boiler side are CLOSED.

- The entire header drainsDW-238/239 DW-178/179, DW-182 /183,DW-186/187 and DW-190/191 on the stationheader are OPEN fully.

- Not simulated. Localoperation.

- Station header inlet vlv AS-3 is OPEN 100%.

- All the unit aux. header drains and vents DW-194/195 are OPEN.

- Not simulated.

- Unit interconnecting valve AS-31 to Unit-1and/or other units are

CLOSED.

- UCB operation.

- Valve AS-10, Unit PRDSconnection to unit header, is CLOSED.


- All header drains can beclosed after charging theheader.

- Local operation.

3. OPEN-UP AS-31 fully tocharge unit aux.header.

- Unit aux. header pressure increases up to

15 Kg/cm2

and '' aux.steam pressure low''alarm clears off.

- UCB indications

4. ENSURE all theconditions are satisfied

before charging the unit PRDS system.

- Oil tank level is ADEQUATE & oil pumpis RUNNING and itspressure is ADEQUATE.

- Local check only. Not simulated.



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- All hydraulic valves'controls are onREMOTE.

- Localoperation/check. Not simulated.

- Isolating valve AS-6 and AS-9 are OPEN 100%


- Isolating vlv AS-4 and AS-7 are CLOSED fully. - UCB check.

- Main steam pressure is

more than 50 Kg/cm2.

- UCB check. Interlock for opening AS-4/7.

- All iso. valves on F.W.line for de-superheatingare OPEN 100%.

- Not simulated.

- Steam pressure andtemperature set points

at 14 Kg/cm

2

and 220deg. C., respectively.

- UCB operation.

5. OPEN AS-4 and AS-7from the UCB to chargeunit PRDS header.

- Integral isolating valves4A and 7A open-up andthen AS-4/7 start opening

- UCB operation.

6. OPEN AS-10 fully andPRDS pressurecontroller gradually andtransfer control to auto.

- PRDS-1 (30% line)starts opening.

- UCB indication

- Temp controller transfers to auto tomaintain set temp after de-super heater

- UCB indication.

- Spray pressurecontroller maintainsfeed water pressure at

20 Kg/cm2(for 30% line)

- UCB check only.

- PRDS-2 starts openingafter a certain controller output.

- Interlock

- Spray pressure set point

ramps up to 40 Kg/cm2

(for 100% line)

- Auto interlock.

7. CLOSE AS-31 after unit PRDS is fully charged.

- PRDS header pressureis to be maintained at 14 Kg/cm2

- At 300 deg. C allPRDS valves are tripclosed.



KORBA SIMULATOR 32

HEAVY FUEL OIL SYSTEM

In coal fired Thermal Power Plants, the Fuel Oil plays a vital role in initial firing of theBoilers and running it up to 25-30% of its capacity. The fuel oil is also used as a stabilising fuel in the coal fired boilers till the coal flame stabilises in the furnace andfor proper coal burning while the load is reduced in the boiler for a shut down.

All the main storage tanks are generally interconnected to the suction side of unloading pumps so that oil from one tank can be transferred to another for thepurpose of any maintenance work. The storage tanks are equipped with Magnetic typefloat switches and Mechanical type float level Indicators to measure the quantity of oilstored.

In order to keep the viscosity of oil in storage tank low, it is essential to keep the oil warm between 50 0C to 70 0C so that the oil from main tanks can be transferred toservice tanks for normal / daily utilisation of fuel oil for the firing. For this purpose a steam floor-heating coil has been laid at the bottom of the tank. Thermostatictemperature controller installed at the inlet of steam heating coil, controls the

temperature of oil tank at the desired point selected between 500C to 700C.

The HFO passes through the oil strainer on the suction side of the high-pressurescrew pump. Heavy oil pumping unit consists of oil suction strainers and screw pumps each coupled through flexible coupling and mounted on a common frame.

HEAVY FUEL OIL SYSTEM



KORBA SIMULATOR 33

The screw pump, when connected to an induction motor with constant speed, is a constant quantity pump and valves in the delivery line control the delivery pressure.

When only a small quantity of oil is fired, the excess oil from the pump dischargeshould be bypassed. This is done automatically by electrically operated, pressuremaintaining valve bypassing the excess quantity through the return oil line to storagetank and the delivery pressure of oil is maintained constant at the pump outlet,

whatever be the quantity of fuel oil.

HFO from the delivery side of the HFO pumping unit enters the HFO pre-heater whereit is heated from pumping temperature to a temperature corresponding to anatomising viscosity. The outlet temperature of HFO from the heat exchanger isautomatically maintained at a constant value by the automatic temperature-regulating valve, mounted on the steam supply line to heaters. The temperature-regulating valve controls the quantity of steam to the heater according to the outlet temperature of the oil from the heater.

H.F.O STORAGE TANKS:

3 Numbers, Capacity: 2500 M3 each

H.F.O. Pressuring Pump:

3 Numbers, Type: Triple screw type, Bornemann

Motor Rating 50 KW, 415 V, 3 ph., 50 Hz

Power Required 32 KW at 370 cst.

Capacity 430 litres / min. at 370 cst.



KORBA SIMULATOR 34

FURNACE SAFEGUARD AND SUPERVISORY SYSTEM

FSSS facilitates remote manual/automatic control of fuel firing equipments throughmechanised system with suitable interlocks and logics. It is designed to ensure theexecution of a safe, orderly operating sequence in start up and shutdown of fuelfiring equipments, and thereby to prevent errors or omissions in following such

procedure.

The system provides protection against malfunction of fuel firing equipments andassociated air system. The safety feature of system is designed for protection in most common emergency situations. FSSS comprises of control circuits, various logics andindicators to carry out the following:

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

• To start and monitor the Ignitors.

• HFO Gun starting, stopping and supervision.

•

Pulveriser and Feeder starting, stopping and supervision.• Flame Scanner intelligence and checking.

• Furnace flame monitoring and overall furnace flame failure protection.

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

• To start/stop ignitor and scanner air fans.

• To regulate the Secondary Air Dampers depending upon the fuel flow

variation.

• To provide boiler trip signal to other system such as PA Fan, Mills,

Turbine, Generator etc.

FSSS equipments can be grouped under three heads:

1. The Operating and Indicating Console Insert in UCB:

This consists of all switches for initiating controls and also indications of status of all fuel firing equipment & their auxiliaries.

2. Relay and Logic Cabinets:

The cabinets consist of relays, timers, programmers, circuit breakers for AC andDC control supplies flame scanner unit, number of coal flow units etc. They control the process logic.

3. Field Equipment:

Field equipments are those which help in actual remote operation of fuel firingequipments and those, which provide the status to the operating, console andrelay logic cabinet.



KORBA SIMULATOR 35

Field Equipment Includes:

Ignitor/HFO Trip Valves, HFO atomising steam, Scavenging steam/ Nozzle valves(Hydra motor type), gun advance/retract mechanisms, oil gun assembly, ignitorsand its cabinets, flame scanner and ignitor air fans, pressure switches,temperature switches, flow switches and limit switches, Mill Discharge valves, hot air gates, seal air valves, cold air, tramp iron gate etc.

FSSS POWERSUPPLY ARRANGEMENT



KORBA SIMULATOR 36

220 V AC SUPPLY SYSTEM

1. ANALOGUE CONTROL SYSTEM (ACS) : (H&B)

2. ANNUNCIATION

3. AUX. PRDS :(SULZER)

4. AUX. RELAY PANEL

5. DATA ACQUISITION SYSTEM (DAS)

6. FEEDER CABINET

7. FSSS AC SUPPLY

8. HP BYPASS CABINET: (SULZER)

9. HYDRASTEP

10. SECONDARY AIR DAMPER CONTROL (SADC)

110 V AC SUPPLY SYSTEM

1. ATOMISING STEAM NOZZLE VALVES

2. FLAME SCANNER MODULE

3. HFO NOZZLE VALVE MOTOR

4. IGNITOR FAN DISCHARGE DAMPER

5. LAMP INDICATION + LOGIC POWER

6. MILL DISCHARGE VALVE

7. MILL FEEDER CONTROL

8. MILL SEAL AIR DAMPER

9. SCAVENGE STEAM NOZZLE VALVE MOTOR

10. SEAL AIR FAN DISCHARGE DAMPER

220 V DC SUPPLY SYSTEM

1. HFO TRIP VALVE

2. HFO RE-CIRCULATION VALVE

3. IGNITOR OIL TRIP VALVE

4. MILL MOTOR CONTROL

5. SCANNER FAN DISCHARGE DAMPER

6. SCANNER FAN EMERGENCY SUCTION DAMPER





KORBA SIMULATOR 38

B) 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 seconds

AND any ignitor valve not closed.

c. Boiler MFR trip command is present.

When ignitor trip valve is closed, the valve ''closed'' green lamp comes on.

Ignitor Starting

There is no separate ignitor start switch provided for any of the elevation AB, CDor EF Ignitors. Pressing any one pair of oil gun ' START' or STOP' push buttongives a starting impulse to all four ignitors of that elevations. The spark is appliedfor 10 seconds only for every pressing of ignitor start push button.

Ignitor Stopping

All four ignitors of each elevation are provided with one 'STOP' push button for taking out ignitors from service. Also ignitor gets stop command, at the end of stoptime trial of HFO oil elevation. When individual ignitors get stop command itsmotorised oil/air valve closes thus taking out ignitors from service.

HEAVY OIL FIRING

Heavy oil can be fired at AB, CD and EF elevation. Heavy oil gun have beenprogrammed to light up on pair basis, diametrically opposite corners (1,3 and 2,4)form the pairs. Each pair is provided with start/stop push button.

HFO guns can be lighted up only if at least 3 out of 4 ignitors at correspondingelevations are in service.

HFO guns are self-sustaining only when elevation firing rate is at 30%, hence,ignitors corresponding to HFO guns in service must only be removed when HFO

burner header pressure is above 3 Kg/cm2 (g) and at least 3 HFO guns at theelevation are in service and corresponding flame scanners are sensing flame.

Flame scanners monitor heavy oil guns flame only when the following conditionsare fulfilled.

i. HFO firing rate (elevation load) is above 30%.

ii. 3 or more HFO guns at the elevation.

iii. Ignition energy removed.



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HFO TRIP VALVE INTERLOCK

A. HFO Trip Valve (HOTV) can be opened by pressing 'OPEN' push button,provided the following conditions are fulfilled.

a. Boiler Trip Command (MFR) is RESET, and

b. All HFO nozzles of AB, CD and EF oil guns are proven fully closed.

c. HFO supply pressure is adequate (more than 16 Kg/cm2).

d. HFO header temperature adequate (more than 95OC)

OR HFO recirculation valve is open 100% (Bypass conditions for all the above.)

B. HO trip valve closes under any of the following conditions:

• HFO header pressure is low (<3.5 Kg/cm2) OR

• HFO header temperature is low (< 95 0C) OR

• Atomising steam pressure is low (<7.5 Kg/cm2.) AND all HFO nozzle valves

not closed. OR A boiler trip occurs, OR

• HFO trip valve 'CLOSE' P.B. is pressed, when HFO trip valve is fully closed,

valve 'CLOSED' green light appears.

HFO Re-circulation Valve Interlock

Opening: HFO re-circulation valve can be opened following a boiler trip and beforestarting furnace purge cycle by pressing valve 'open' push button. Valve opensprovided:

a. All of the HFO nozzle valves are fully closed, and

b. Re-circulation Valve ' OPEN' command is given.

Closing: HFO re-circulation valve closes automatically when anyone of the nozzle valves (Hydra motor) is not closed, or manual ' CLOSE' command is given.

Heavy Oil Gun Elevation Start Permissive:

a. D.C. power available

b. Ignitor trip valve is proven fully open.

c. No boiler trip command persists.d. HFO trip valve is proven fully open.

e. Heavy oil temperature above 100oC.

f. Airflow adjusted between 30% and 40% of full load airflow.

g. Burner tilt placed in horizontal position.

The last two conditions are not required if any one feeder is PROVEN.



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HFO Corner Start Permissive

At each main oil corner to be placed in service, following conditions should besatisfied:-

a. The main oil guns are inserted in guide pipe and coupled.

b. The local maintenance control switch is placed in REMOTE.

c. HFO manual isolation valve is open.

d. Atomising steam manual isolation valve is open.

e. Scavenging steam valve is closed.

f. 'Elevation Start' Permissive available

HFO Gun Starting Sequence

When HFO Pair start push button is pressed a pair of HFO guns is placed inservice in following sequence (provided HFO elevation start premissives aresatisfied).

• Within first 10 seconds of pair start trial time associated elevation ignitors arestarted. When ignitors are proven, Ignitor 'ON' signal comes on. If the flame isnot proven, sparkwill cease and Jamesbury Valve is closed after 10 seconds.

• When minimum 3 out of 4 ignitors at the associated elevation are proven ‘ON’ at the end of 10 seconds, a start command is given to heavy oil gun no. 1 (if pair 1- 3 is selected) or to heavy oil gun no. 2 (if pair 2 - 4 is selected), if corner-scavenging valve is closed.

• Twenty five seconds later a start command is sent to corner no 3 (in case of 1 -3 pair) or corner no. 4 (in case of 2 - 4 pair)

When an individual heavy oil corner receives a 'start' command and its associatedignitor is proven 'ON' it is placed in service in following sequence.

a. Heavy Oil gun advances to firing position. 'Gun Retracted' lamp

goes out and 'ADVANCE' light glows.

b. When the gun is fully advanced, the atomising steam valve

opens.

c. When the atomising steam valve is proven fully open, the heavy

oil nozzle valve opens placing the HFO gun in service.

All ignitors can be removed by pressing Ignitor Stop push button.

- 3 out of 4 HFO nozzle valves are proven open.

- Elevation loading is about 30%.



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- Minimum 3 out of 4 flame scanners sensing flame at that

elevation.

Unsuccessful Corner Start:

At the end of 90 seconds of pair start trial time a heavy oil corner trip isinitiated for any corner when -

a. Heavy oil nozzle valve is not proven fully open.

b. Associated ignitor is not proven 'ON'.

Heavy oil Elevation Shutdown

Heavy oil elevation is removed from service on a pair basis. Depressing theassociated elevation pair stop P.B. will initiate a 375 sec. time trial toshutdown and scavenge the associated pair of heavy oil guns as follows:

a. During first 10 seconds of stop time trial associated elevation of

ignitors is started.

b. At the end of start time a stop command is sent to corner no. 1

(when pair 1 & 3 is stopped) or corner no. 2 (when pair 2 & 4 is

stopped).

c. Fifteen seconds later, a stop command is sent to corner no. 3

(when pair 1 & 3 stopped) or corner no. 4 (when pair 2 & 4 is

stopped).

When an individual heavy oil gun that is in service, receives a stop command:

a. A scavenge command for that corner is initiated and HFO nozzle

valve closes. The atomising steam valve remains open.

b. When the HFO valve is proven fully closed and if the associated

ignitor is proven ON and the atomising steam valve has remained

open, the scavenge valve opens.

c. When the scavenge valve is proven fully open, a five minute

scavenge period is started.

d. At the end of 5 minutes scavenge period, the atomising steam valve close.

e. When both the valves are proven fully closed, the HFO gun is

retracted from firing position.

Six minutes after, remaining pair of HFO guns stop is initiated, a back-up trip



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signal is established which will remove the associated elevation of ignitorsfrom service and initiate a close signal to all HFO nozzle valves, all of thescavenge valves at the elevation to ensure they are closed. Fifteen secondslater an 'Unsuccessful Elevation Shut-down' alarm comes if –

a. Any HFO gun is not retracted from firing position at any elevation,

OR b. Any HFO nozzle valve is not closed at any elevation.

PULVERISER INTERLOCKS

Pulveriser Ready Permits

At the respective Pulveriser, all of the following conditions are to be satisfied:

1. Start Permit.

2. Pulveriser discharge valve open.

3. Seal air O.K.

4. Cold air gate open.

5. Pulveriser outlet temperature less than 200o F.

6. Primary air permit.

7. No Pulveriser trip.

8. Feeder local selector switch is on REMOTE.

9. No unsuccessful start.

10. Tramp iron hopper valve open.

When all the above conditions are satisfied for the respective Pulveriser, itsassociated 'Pulveriser Ready' light appears.

Availability of Ignition Permit for Pulveriser Operation:-

Prior to starting any Pulveriser, ignition energy must be adequate to support coal firing. This is accomplished as follows:

Pulveriser-A

i. A minimum 3 out of 4 elevation AB heavy oil nozzle valves provenopen.

OR

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





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ii. Boiler loading is greater than 30 % and feeder-E is in service andgreater than 50 % loading.

Condition (i) is not required if any coal feeder is already 'PROVEN'

Pulveriser Start

When both ''Ignition Permit'' and 'Pulveriser Ready' are established for the respectivePulveriser, the Pulveriser may be placed in service as follows:

• Start the Pulveriser by depressing its associated push button.

• When the Pulveriser is proven ON as indicated by its (red) indication open thehot air gate by pressing its open push button and allowing the Pulveriser

outlet temperature to come up to more than 60oC. Adjusting Hot/Cold air controlling dampers does this.

•

When the Pulveriser temperature comes up to (Approx. 60-90oC) start thefeeder by depressing its associated START push button (associated elevation of

fuel air dampers should be closed for feeder starting).

Coal flow must be proven either by the coal flow detector or satisfactory Pulveriser amps within five seconds after the feeder is started. Fifteen seconds after the feeder is started, the feeder output is released to automatic control, and the fuel air damper is opened to modulate as a function of feeder speed.

When a minimum of two feeders are established at greater than 50% load theassociated elevation of oil guns may be shutdown provided the feeder has been on for a minimum of three minutes.

Feeder Start Permissive and Interlocks

a. Feeder speed minimum (controller position less than 20%).

b. Pulveriser 'ON' and its outlet temperature more than 55oC.

c. All Pulveriser ready conditions as mentioned above are satisfied.

d. Coal silo gate open (Operator check only).

Feeder Interlocks.

Either of the following conditions will force the feeder speed to manual and

minimum until the initiating condition is corrected.

i). Pulveriser bowl differential pressure high (>250 mm WCL)ii). Pulveriser grinding current above 38 Amperes.

Loss of coal flow and low Pulveriser power as confirmed by Pulveriser amps will tripthe feeder. Any Pulveriser trip shall trip the associated feeder instantly.



KORBA SIMULATOR 45

Hot/Cold Air Dampers and Hot Air Gate Interlocks

All cold air dampers (CADs) will close to less than 5% open when the START

command is given to any PA Fan if no PA fan is running.

All CADs shall open 100% if boiler trips.

When the start command is given to any Pulveriser, the associated cold air

damper is open 100%.

When any Pulveriser outlet temperature is more than 95oC the CAD is open

100% and HAD is closed 100%.

Operation release for the CAD is obtained when the associated HAG (hot air gate)

is opened 100%.

The HAG can be opened manually when the associated Pulveriser is 'ON'. or it

can be opened automatically when Pulveriser on command is given on 'AUTO'.

HAG of any Pulveriser will close if the temperature at outlet of Pulveriser is more

than 95oC or the associated feeder trips with a time delay of 40 sec.

The HAG will close instantaneously if the associated Pulveriser trips from

service.

PULVERISER TRIP CONDITIONS

The following conditions will initiate a Pulveriser trip command:

• Pulveriser discharge valve not open.

• Loss of unit critical power for more than 2 seconds.

• Pulveriser ignition permit is not available or lost when supporting

ignition is required if the feeder is 'on' for less than 3 min.

• Boiler MFR trip.

• Primary air header pressure very low (< 585 mm wcl).

Note:

1. When both PA fans are tripped or hot PA pr. falls below the low set point of

585 mm wcl all pulverisers in service receive a trip command with a time delay of 5 seconds. When hot primary air duct pressure falls below very low set point of 525 mm WCL, all pulverisers in service are tripped instantaneously.

2. When only one PA fan trips or stopped and four or more pulverisers are inservice, a trip command will be initiated to trip the running Pulveriser fromthe top until the number of pulverisers running is reduced to three.



KORBA SIMULATOR 46

BOILER TRIP CONDITIONS (200MW)

FSSS protects the boiler by trippingout all fuel inputs, under thefollowing conditions

1. Simulate Trip.2. Loss of 220V DC to FSSS.

3. Elevation Power Failure.

4. Flame failure.

5. Loss of all fuel.

6. Airflow falls below 30% (MCR).

7. Furnace pressure high (+ 200 mm WCL).

8. Furnace pressure low (- 200 mm WCL).

9. Drum level high (+ 225 mm).10. Drum level low (-225 mm).

11. Re-heater protection trip.

12. Turbine Trip with boiler load more than HP/LP Bypass capacity (60%).

13. Loss of all Boiler Feed Pumps.

14. Both Emergency Push Buttons pressed.

15. Loss of ACS Power.

16. Loss of Unit Critical Power.

17. Both FD Fans OFF.18. Both ID Fans OFF.



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KORBA SIMULATOR 48

STEPWISE OPERATION LOGICS OF F.S.S.S. (200 MW)

1. PURGE PERMISSIVE & PURGE COMPLETE

2. IGNITOR WARM-UP & RE-CIRCULATION FUEL TRIP VALE

3. IGNITOR FAN AND OUTLET DAMPER CONTROL

4. SCANNER AIR FAN CONTROL

5. WARM-UP ELEVATION START PERMIT

6. PAIR 1-3 AND 2-4 WARM-UP ELEVATION CONTROL

7. SELECTION OF OPERATION MODE

8. OPERATION IN ELEVATION MODE

9. WARM-UP ELEVATION IGNITOR CONTROL

10. WARM-UP ELEVATION CORNER NOZZLE CONTROL

11. PULVERISER READY

12. PULVERISER TRIP

13. COAL ELEVATION PULVERISER CONTROL

14. PULVERISER SEAL AIR VALVE & DISCHARGE VALVE CONTROL

15. FEEDER CONTROL

16. AUTO CLOSE COMMAND FOR HOT AIR GATE

17. HOT AIR GATE CONTROL

18. COLD AIR DAMPER CONTROL

19. MILL FEEDER SPEED DEMAND TO MINIMUM

20. MILL FEEDER PROVEN SIGNAL

21. RELEASE FOR AIR AND TEMP. CONTROL TO AUTO

22. PULVERISER IGNITION PERMIT A & F

23. PULVERISER IGNITION PERMIT B & E

24. PULVERISER IGNITION PERMIT C & D

25. CONTROL OF SEAL AIR FAN



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KORBA SIMULATOR 74

OPERATION PROCEDURE

AIR PRE-HEATER OPERATION

PRE-START CHECKS


1 CHECK all thepre-start conditions aresatisfied.

- Support bearing/ guide bearing lub oil pumpsRUNNING and lub oilcoolers are CHARGED.

- Associated red lamp ison

- Bearing temperature NOT

HIGH (less than 60oC)

- Ascertain from localoperator.

- Electrical supply is

AVAILABLE.

- If not, line-up air motors.

Local operation.

- Isolating valves of air motors are 'OPEN' and

bypass valves of air motor solenoids are 'CLOSED'.


- 'Air motors' lub oil level ADEQUATE

- Local check.

- Service air pressure is

ADEQUATE (> 5 Kg/cm2)

- Local/UCB check.

APH STARTING PROCEDURE

WHEN BOTH APHS ARE OFF


1 START air motors of both

APHs.

- Air motors ON indicationscome on

- Corresponding red lampglow.

- Isolating dampers of APHsstart opening.

- UCB indications.

2 START air heater electrical motor.

- Breaker CLOSEDindication comes on

- UCB indication.

- Associated air motor stops.

- UCB indication.



KORBA SIMULATOR 75

- Starting current shoots upand comes down tonormal load current.

- UCB indication.

- Isolating dampers of theair heater remain open.

- Associated red lamps on.

- Isolating dampers of theother air heater, not inservice, start closing if itsair motor is not ON.

- Associated green lampscome on.

3 INSTRUCT localoperator tocheck, locally,for any abnormalsounds from

bearings/seals.

- There should be noabnormal hunting in air heater amperes meter readings.

- UCB check.

- There should be noabnormal sounds from air pre-heater seals or

bearings.

- Local check.

- Bearing temperaturesmust be within the normal

range (65 oC -75 oC)

- UCB OMNIGUARDindicators must befrequently monitored.

Note: Air pre-heaters air motors can be started manually provided electrical motorsare off, isolating valves of air motor solenoid are open and service air pressureis normal. The air motors come into service on auto interlock, whencorresponding electrical motors trip-out on any protection.

WHEN ONE APH IS RUNNING


1 CHECK beforestarting any

APH.

- All pre-start checks areCOMPLETED.

- Local/UCB.

- Support bearing / guide bearing lub oil pumps areON.

- Corresponding red lampsON.

- Bearing temperature NOT

HIGH (< 60 oC) and lub oilcoolers are CHARGED

- Ascertain from localoperator.



KORBA SIMULATOR 76

- Electrical supply is AVAILABLE

- Refer to the respectivemodules.

- Air motor is ON - UCB check only.

All isolating dampers of the air pre-heater areOPEN.

- Red lamps on.

2 START air pre-heater electricalmotor.

- Breaker CLOSEDindication comes on.

- Red lamp on.

- Starting current goes upand comes down tonormal load current

- UCB/Local check.

- Air motor goes off. - UCB indication Interlock.

- Air heater isolatingdampers remain open.

- UCB check.

There should be no ABNORMAL hunting of ampere reading.

UCB indication.

3 INSTRUCT localoperator tocheck for healthy runningof air heater.

There should be noabnormal sounds from air pre-heater seals/

bearings.

Local checks.

The bearing temperaturesmust be within the normal

range (60 oC to 75 oC).

UCB OMNIGUARDindicators must bechecked for bearing tempfrequently.

SHUT DOWN PROCEDURE


1 CHECK - Corresponding ID& FDFans are running.

- Associated breaker closed indication are on.

2 UNLOADassociatedID/FD fans,gradually.

The other pair of ID/FDfans (if running) startsloading up on auto.

Operator's action, if fancontrols are on manual.



KORBA SIMULATOR 77

3 STOP theassociated FDfan.

- Fan breaker goes open. - Maintain desired oxygenpercentage.

- Furnace total airflow indication drops slightly.

- Reduce firing if required.

4 STOP theassociated IDfan.

- Furnace pressureincreases slightly.

- Maintain furnace draft between-5 to - 10 mm wcl.

5 STOP air heater electrical motor.

- Air heater electrical motor goes off.

- Breaker off green lampcomes on

- With a few seconds timedelay, the isolatingdampers of the air heater are closed, if the other AIR HEATER is in service.




KORBA SIMULATOR 78

ID FAN OPERATION

PRE-START CHECKS


1 CHECK all thestart permissiveare satisfied

before startingthe ID Fan.

- Fan lub oil pressure is ADEQUATE (1.2 Kg/cm2).

- If not, ask the localoperator to start the luboil pump and check thepressure.

- Fan inlet/outlet dampers(GD 17/18, GD 21/22 isCLOSED.

- The dampers start closing after the first fanstart command is given.

- Fan inlet guide vanes areat MINIMUM position.

- This permissive isfulfilled after the first fanstart command is given.

- Fan bearing temperature

is NOT HIGH (< 60 oC .)

- Local/UCB check. Fanstart permissive. areavailable.

2. CHECK if thefan is lined-upfor operation.

- Electrical supply for various motor operateddampers is ON.

- Local operation/check.Boiler VDDC / MCCpanels to be checked.

- Lub oil system is lined upand water/oil coolers areCHARGED.


- Oil level in the tank is ADEQUATE.

- Local check. Not simulated.

- Anyone or both APHare ON.

- UCB check. Interlock.

- EPBs are in RELEASEDposition.

- Local operation/check

- Inlet guide vanes are100% open when both ID

fans are off.

- Local check. IGVs areOPERATIONAL and ON

REMOTE

- Instrument air pressureis ADEQUATE.



KORBA SIMULATOR 79

3 CHECK if fluegas path isLINED-UP for IDFan operation.

- ID fans' suction/discharge dampers areOPEN 100% andoperational.

- Local check.

- Manual isolating damperson suction / dischargeducts of ID fans (GD-19/20/23/24) are OPEN.


- Sealing/flushing water supply for ESPs,economiser, APHs and

bottom ash hoppers is AVAILABLE.

- Local check.Not simulated.

- Gas isolation dampers for ESPs and APHs are open.

- UCB indications.

- Changeover dampers GD-5/6 before ESPs areOPEN.

- UCB indication

- Changeover dampers after ESPs (GD-15/16) areoperational and CLOSED.

- Local check. UCBindication and interlock.

- Gas path is through for starting ID fan. (ESPs) A &B isolation dampers, APH-

A gas and secondary air isolation dampers areOPEN. OR ESPs C & Disolation dampers + APH-B gas isolation dampersare OPEN. OR APH-B gasisolation dampers+ ESPs

A&B isolation dampers +GD-5 and GD-6 are OPEN.

- For ID Fan-A gas pathclear interlock.

Gas path ready conditions for IDFan-B can be found out

by symmetry

- ID Fan breaker is onSERVICE/REMOTEposition.

- Local operation.



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STARTING PROCEDURE

WHEN BOTH THE FANS ARE OFF


1 Check before startingID Fan. - All pre-start checks areOVER. - ''Inlet guide vanesmin.'' & Inlet/outlet dampers closed''permissive becomeavailable after the fanstart command isgiven.

- All permissive for thefan AVAILABLE.

- Local operator is

informed before the fanis started.

2 START fan. - Inlet/outlet dampersstart closing

- UCB indication.

- Inlet vanes come tominimum.

- Controller output minimum.

- The fan breaker isCLOSED after inlet/outlet dampers

close fully.

- Breaker closed redindication comes on.

- Starting current goes upto 500A and comesdown to no load current of 45 A.

- UCB indication.

- Change-over dampers(GD-15, GD-16 start opening. (After fanstarts).

- Corresponding redlamps come on.

- Inlet/outlet dampersopen up.

- UCB indication.

- Inlet/outlet dampers of the other fan go closedand regulating vanes goto minimum position.

- Associated greenlamps on & controller position of IGV

becomes zero.

3 ADJUST inlet guide - Fan amperes go up with - UCB indication.





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2 START fan motor - Fan motor current settles down at 45A.

- Breaker closedindication comes on.

- Inlet/outlet dampersstart opening.

- Associated redlamps come on.

- GD-15 and GD-16 get closed.

- Interlock.

3 REGULATE fan vanes toequalise load on boththe fans.

- Maintain furnace draft -5 mm wcl.

- As per the boiler load.

- Maintain desiredairflow.

4 CHECK locally & inUCB the brgtemperature and

vibration level.

- Bearing temperaturelimits are Alarm Trip

- UCB OMNIGUARDindicators may bechecked.

Alarm Trip

Fan 95 oC 105 oC

Motor 75 oC 80 oC

5 ADJUST bias to 50%and furnace draught set point to 45%.

- Furnace draught set point and biasing set points have beenprovided above Fan-A &Fan-B vane controlsrespectively.

- Operator action.

- Check furnace draught is maintained between -5 mm wcl to-10 mm wcl.

- UCB checks.

6 TRANSFER vanecontrollers of both fansto ''AUTO''.

- Vane controllerstransfer to AUTO

- UCB INDICATION

- Inlet vanes modulate tomaintain set value of furnace draught.

- Furnace draft highalarm at + 50 mm &low alarm at -50 mm.



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SHUT DOWN PROCEDURE


1 SELECT IGV controlsof both fans to

manual.

- IGVs control transfers tomanual.

- M/A release push button must be pressed

for auto manualchangeover.2 REGULATE IGVs of

the ID Fan tominimum.

- ID fan dischargepressure decreases.

- Maintain furnacedraught at -5 mm wcl

by loading the other IDfan.

- ID fan current come tominimum load current of 45 amps.

3 STOP the ID fan. - The flue gas after EPinterconnecting dampers

open on interlock.


- Total airflow dropsslightly avoid Boiler trip

- Maintain airflow morethan 30%.

- The inlet and outlet dampers close oninterlock.

- UCB indication.

4 REGULATE the inlet guide vanes of therunning ID fan todesired loading.

- Maintain furnacedraught at -5 mm wcl.

- If the need be, reduce boiler firing to approx.50% to maintainfurnace draught &prevent running ID fanover-loading.

- Maintain desiredamount of oxygenpercentage.

5 CHECK the motor winding temperatureof the running ID fan

- Motor windingtemperature limits are

- DAS indication

Normal Trip

100 0C130 0C

Note : If associated FD fan is in service it will be necessary to unload FD fan andstop it before stopping ID fan; to avoid airflow fluctuations (Refer to FD fanshutdown procedures). With ID fan being stopped corresponding FD fan

will also trip.





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- FD fan dischargedampers areOPERATIONAL andelectrical supplies are

AVAILABLE.

- UCB checks.

STARTING PROCEDURE



1 CHECK beforestarting FD Fan.

- All pre-start checks are OVER. - "Blade pitch minimum"and "Discharge damper closed" permissive areavailable after the fanstart command is given

- Control/lub oil pressure: OK - Bearing temp is NOT HIGH.

- Blade pitch is MINIMUM.

- Discharge damper is CLOSED.

- Control oil temp is NORMAL.

- Local operator is INFORMED.

2 START the FDfan motor.

- Discharge dampers start closing - UCB indication.

- Blade pitch comes to minimum. - Controller output 0%.- As soon as discharge damper

closes, "Blade pitch minimum"permissive comes on.

- Associated saffron lampon.

- Fan takes starting current (300A approx and comes down to noload current of 15A).

- Red lamp ON indicationcomes

- Discharge damper starts opening(for the fan started).

- Refer to the damperslogics.

- FD fan discharge pressureincreases.

- UCB indication

- Blade pitch for the other fangoes to minimum.

- Associated saffronlamps come on.

- Discharge damper for the other fan closes

- Interlock.



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3 Instruct localoperator tocheck bearing

vibration andtemperature.

- Bearing temperature and vibration limits are:

- UCB OMNIGUARDindicators must beregularly checked for

bearing temperatures.

Alarm TripFan

90oC 105

oC

UCB indication

Motor 80 oC 95 oC UCB indication

Vibration. 2 mm/sec 2.5 mm/sec. UCB indication

Motor wdg temp. 120 oC

135 oC DAS indication

4 ADJUST the blade pitchcontroller to get desired airflow.

- Fan discharge pressureincreases.

- Maintain furnacedraught between-5 to10 mm wcl and airflow 30%-40% duringpurging.

- Fan amperage changes

accordingly.

- Oxygen percentage variesaccordingly.

- Wind box pressure also varies, with FD fan loading

5 MAINTAIN the Wind box tofurnace DP asper boiler

loading.

- Wind box to furnace DP should be maintained as shown: -Boiler load<30%-30 to 40 mm of

wcl Boiler load>30% - 100 mm of

wcl

- UCB indication.

WHEN ONE FAN IS RUNNING


1 CHECK all fanstart permissivein the UCB.

- Bearing temperature is NOT

HIGH. (<60 oC)

- Associated saffron lampson

- Control/lub oil pressure is OK.

- Local check & operation

- Blade pitch controller positionis at MINIMUM.

- Local/UCB check.

- Discharge damper CLOSED. - Interlock.

- Both ID fans are in SERVICE. - UCB check only.



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- Control oil temperature isNORMAL

- Local check.

- Local operator duly informed.

2 START the FD fan - The fan breaker gets closed.

- Red lamp ON.

- Discharge damper of the fanstarts opening

- UCB indication

- Furnace pressure and totalairflow increases slightly.

- UCB indication.

3 ADJUST the bladepitch to maintaindesired airflow and wind box pressure.

- Fan discharge pressureincreases

- UCB indication.

- Fan amperage increases

accordingly

- Maintain furnace draft &

Wind box DP

- Furnace pressure increasesslightly

4 CHECK vibrationand bearingtemperatures inthe UCB.

- The limiting values of vibration& bearing temperatures are:

- UCB vibration & bearingtemperature indicatorsmust be monitoredregularly.

Alarm Trip

Vibration. 2mm/ sec.pk 3mm/ sec.pk - Check locally also.

Fan brg. 90oC 105oC

Motor Brg. 80oC 95oC

5 ADJUST biasingset pt. to 50%.

- Biasing setpoint comes to 50%. - It ensures equal fanloadings on auto mode.

6 TRANSFER FDfans blade pitchcontrol to AUTO.

- FD fan blades modulate tomaintain set oxygenpercentage.

- Oxygen set point isgenerated as per boiler load. (Boiler master output)

- Oxygen in flue gas variesaccordingly

- Maintain 3% to 6%oxygen before APHsdepending on boiler load.



KORBA SIMULATOR 88

FURNACE PURGE PROCEDURE

CTION OBSERVATION REMARKS

1. CHECK ALL THEPURGE PERMISSIVE

IS satisfied on theFSSS console.

- "No boiler trip" commandis AVAILABLE.

- Associated lampscorresponding to

each permissivecomes on in the FSSSconsole.

- All ignitor valves areCLOSED.

- UCB indication.

- All HFO nozzle valves areCLOSED.

- UCB indication.

- HFO and ignitor trip valves are CLOSED.

- UCB check only.

- All pulverisers andassociated raw coalfeeders are OFF.

- UCB indication.

- All mill hot air gates areCLOSED

- UCB operation frommill console

- Both PA fans are OFF - UCB check only.

- All fire ball and oildiscriminating flamescanners must be sensingNO FLAME.

- UCB check only.

- AC/DC electrical power supplies to FSSS panelsare AVAILABLE.

- UCB alarmsindications are reset

- All auxiliary air dampersof the wind box areMODULATING& furnace to

wind box DP > 40 mm wcl.

- Permissive. UCBcheck

2. ADJUST aux. air andoil air dampers'controllers to 50%

position & TRANSFER damper controls to auto

- Damper controllers cometo 50%

- UCB operation.

- After damper reset programme is over, wind

box dampers modulate tomaintain set WB/F DP if put on auto.

- Refer to the note inthe end of thesection.



KORBA SIMULATOR 89

- Oil elevation dampers alsomodulate with aux. air dampers when no oil gunis in service

- Refer to thesecondary air damper control logics

3. ADJUST ID and FDfan vanes and wind

box dampers to get desired airflow and

wind box pressure.

- Boiler airflow less than30% annunciation goesoff.

- On the total airflow indicator 27% and36% airflow corresponds to 30%and 40% boiler MCR airflow values.

- Boiler airflow and wind box pressure aremaintained at less than40% and 40 mm wcl,respectively.

4. ADJUST burner tilt controller to 50%position

- All burners at allelevations and in allcorners, come tohorizontal position

- UCB indication.

- "Burner tilts horizontaland Airflow less than 40%"permissive comes ON.

- UCB indication.

- If all other permissive aresatisfied, "Purge Ready"indication comes ON.

- UCB check only.

5. PRESS "push topurge" button on theFSSS console

- "Purging" indication comeson the FSSS console.

- UCB indication.

- If in the meanwhile noneof the permissive are lost,"Purge complete"indication comes on FSSSconsole, with a time delay of 5 minutes.

- Refer to the FSSSlogics

- MFR-A & MFR-B get reset. - Indication on FSSS

- Boiler Trip "cause" alsoresets.

- "Boiler MFR Trip"annunciation clears off.

- UCB annunciation.





KORBA SIMULATOR 91

BOILER LIGHT-UP

PREPARATION FOR BOILER LIGHT-UP

ACTION OBSERVATION REMA

- HFO supply header pressurestarts increasing, up to 24

Kg/cm2.

-1. INSTRUCT fuelstation operator tostart HFO & light oil(HSD), pumps.

- Ignitor oil pressure(HSD) comes up, at the unit fuel station locally.

Minimum 17kg/cm

2 supply header Pressureis required for opening HOTV.

2. - Atomising steam pressurestarts increasing up to

8.5 Kg/cm2.

- UCB indication.INSTRUCT firing floor operator to chargeHFO heating and

Atomising steam lineslocally - HFO temperature starts

increasing, providedHFO re-circulation is charged.

- Associated steamline drains must

be opened.Local.

3. OPEN HFO short Re-circulation valves,HO-55.

- HO-55 valve open indicationcomes on & oil flow isestablished up to the HFO trip

valve.

- UCB indication.Not required if other units areon oil firing.

4 INSTRUCT localoperator to

-Put all HFO guns intheir guides.

- Oil gun ADV/RETRACT indication comes in the UCB.

- Local operation

-Check guns

ADVANCE/ RETRACT mechanism.

- Corresponding indicationcomes on, in the UCB.

- Local operation

-'Put guns' selector switches onREMOTE.

- Associated gun on REMOTEindication comes in the UCB.

- Permissive.Local Operation

-Open all isolating

valves on oil &steam lines of allHFO guns

- No indication in the UCB. - Gun start permissive.Not simulated.



KORBA SIMULATOR 92

BOILER LIGHT-UP PROCEDURE

ACTION OBSERVATION REM

1. CHECK theseconditions before the

boiler light up

- Boiler "MFR TRIP" is RESET. - Purgingcomplete. UCB

indication.- Pre-start checks for boiler

light up have beenCOMPLETED.

- Local/UCBcheck.

- Fuel oil system is adequately LINED-UP.

- Local operatorsresponsibility.

- Super heater / Reheater air vents are OPEN.

- Local operation.

- SH/RH start-up vents are

OPEN.

- UCB operation

- Ignition air fans are LINED-UP for operation

- Local operation

2. Open heavy fuel oil re-circulation valve

- HFO re-circulation valveopens up.

- UCB indicationInterlock beforeopening HFOtrip valve.

3. OPEN heavy fuel oiltrip valve

- HFO trip valve opens up. - UCB indicationon FSSS

console.- Short re-circulation valve

closes.- Interlock. UCB

indication.

4. OPEN heavy fuel oilcontrol valve.

- HFO header pressure rises up

to 10 Kg/cm2(approx.)

- UCB indication.

- "HFO" inlet and re-circulationflow start increasing

- UCBannunciation.

- "HFO header pressure very low" alarms clear off.

- HFO temperature in the HFO

header increases up to 110 oC

- UCB indication.

5. OPEN Ignitor oil trip valve

- Ignitor oil trip valve opens up. - Associated redlamp comes on.

- Ignitor air fans A & B, start - Refer to ignitor



KORBA SIMULATOR 93

automatically. trip valve logics.

- Ignitor oil and ignitor air pressure increase up to 23

Kg/cm2

and 400 mm wcl,respectively.

- UCB indication.

- "Ignitor air to furnace DP low"& "Ignitor oil/Atomising air pressure low" & "Ignitor oil/HFO trip valve closed"alarms clear off.

- UCBannunciations/Indication.

6. CHECK theseparameters are withintheir operation limits.

- Drum level normal (-60 mm.to 0, preferably on lower side).

- To take care of swelling effect

- HFO temp. 110 oC . (Min.

temp. required is 95 oC).

- HFO trip valve

closes at 93 oC.

HFO atomising steam

pressure 8.75 Kg/cm2

HFO trip valveis tripped at

6.5 Kg/cm2

atomisingsteam pr.

Light oil pressure more than

15 Kg/cm2.

Ignitor atomising air pressure

5 to 7 Kg/cm2

Ignitor trip

valve closes at 8Kg/cm

2of light

oil pressure and

4.5 Kg/cm2

of instrument air pressure.

Wind box pressure between35 to 40 mm wcl

7. ADJUST HFO header pressure set point to

50%(13 Kg/cm2) and

TRANSFER its controlto auto.

- HFO header pressure set point is provided above theHFO pressure controller.

- M/A releasemust be pressedfor auto /

manualchangeover.

- HFO pressure controller transfers to auto andmodulates to maintain the set HFO header pressure.



KORBA SIMULATOR 94

8. CLOSE heavy fuel oilre-circulation valve.

- HFO re-circulation flow valvecloses.

- UCB indication.

- HFO re-circulation flow comesto minimum position

- UCB check only.

- HFO header pressure goes upand is brought down to set HFO pressure by autocontroller

- Controller action.

9. PUSH " Pair 1-3 or 2-4Start" push button.

- In the first 10 secs of the pair start trial time; ignitors 1-3and 2-4 are proven, in theassociated oil elevation.

- Associatedignitors “ON”indicationscome on.

- "Ignitor Stop" light goes off inthe associated elevation.

- If the flame isnot proven,spark ceasesand ignitor

Jamesbury valve closes.

If minimum 3 ignitors areproven on, command goes tocorner 1 or 2, for the gun toadvance to the firing position,provided associated ignitor ison

- Minimum threeignitors should

be proven ON.

- Gun. "Advance",lamps come on

- Command is given to open theassociated atomising steam

valve after the gun is fully advanced.

- Refer to theFSSS logics.

- After the atomising steam valve is fully open, commandis given to open thecorresponding HFO corner nozzle valve.

- Refer to theFSSS logics

- 25 second later commandgoes to corner 3 or 4, as thecase may be, HFO nozzle valveto open.

- UCB indication

- Associated discriminating oilflame scanners start sensingflame.

- Refer to theFSSS logics.



KORBA SIMULATOR 95

- HFO control valve modulatesto maintain set HFO header pressure

- Maximum HFOheader pressuremust not bemore than 13

Kg/cm2 (alarm)

10. ADJUST heavy oilpressure controller todesired firing

- HFO header pressure changesaccordingly - HFO trip valvetrips at theheader pressure

of 3.5 Kg/cm2

- Oil scanner performanceimproves with increasingheader pressure.

11. PUSH second pair "Start"(Pair 1-3/2-4)push button.

- HFO guns advance andcorresponding nozzle valvesopen up.

- Refer to theFSSS oil gunlogics.

12. PUSH "Ignitor Stop"push button to removeignitors if the oil flameis stable in every corner in the elevation

- All the elevation ignitors gooff.

- UCB indication.

- If any discriminating scanner flickers to show 'no flame',corresponding oil nozzle valveis closed automatically



KORBA SIMULATOR 96

PA FAN OPERATION

PRE-START CHECKS


1 CHECK that all PA fans start permissiveis satisfied.

- PA fan bearing tempNOT HIGH (<60oC.).

- Local/UCB checks.

- PA lub oil pressure is ADEQUATE.

- If not, instruct localoperator to line-up.

- PA fan inlet guide vanesare at MINIMUMposition.

- This permissive issatisfied after thefirst PA fan start command is given.

- PA fan FSSS start

command is AVAILABLE(BOILER MFR: RESET &all mill cold air dampersare less than 5% OPEN).

- This permissive is

satisfied after thefirst fan start command is given.

- PA fan discharge damper is CLOSED.

- Interlock.

2 CHECK that PA fan islocally line up for starting.

- PA fan lub oil coolers areCHARGED from aterside.


- PA Fan LOP : ON andother pump is on AUTO

- Local operation andcheck.

- PA fan lub oil tank levelis ADEQUATE.

- Local check.

- PA fans EPBS are inRELEASED position.


- PA fan guide vanes areon REMOTE. Instrument air pre. is AVAILABLE.

- Local operation/check.

- PA fan discharge damper is OPERATIONAL andpower supply is

AVAILABLE.

- Local check.

3 CHECK. if air systemis lined up beforestarting PA fan.

- APHs primary air isolation dampers areOPEN.

- UCB indication.



KORBA SIMULATOR 97

- Seal air fans are LINED-UP and their suctiondampers AD-31/32/33are OPEN.


- Mills' cold air damperson REMOTE. Instrument air pre. is AVAILABLE.


- Furnace purging isCOMPLETED and MFRsare in RESET condition.

- FSSS start commandrequirement is met.

- All man material isremoved from thepulverisers.

- Local check.

STARTING PROCEDURE



1 CHECK theseconditions beforestarting the PA fan.

- All pre-start checksCOMPLETED.

- Local/UCB check.

- Fan discharge dampers100% OPEN.

- UCB check only.

- Regulating vanes are 100%OPEN.

- UCB indication

- Lub. oil pressure is ADEQUATE. (>.1.8 Kg)

- If not, ask the localoperator to line-up.

- FSSS start command (MFR - A&B reset on the FSSSconsole and all mills coldair dampers are less than5% open) is ON.

- This permissive becomes availableonce the first PA fanstart command isgiven.

- Bearing temperature NOT HIGH. (<60 O C).

- Saffron lamp on.(Permissive)

2 START thePA fan motor.

- Discharge damper startsclosing.

- Associated red andgreen lamps comeon.

- Regulating vanes of the fanget closed.

- Saffron lamps(permissive) glow on.



KORBA SIMULATOR 98

- All mills cold air dampersgo to less than 5% openand "FSSS start command"permissive comes on.

- Saffron lamp(permissive) glow on.

- CB closed indication comeson.

- Associated red lampcomes on.

- Fan current shoots up to700A and comes to No loadcurrent 70A.

- UCB PA Fanammeter.

- Discharge damper opensand for the other fan, it closes and regulating vanesof the other fan also goes tominimum position

- UCB indication.

3 ADJUST the PA fanguide vanes to get desired hot PA header pressure of 760 mm wcl

- PA fan discharge pressuregoes up.

- Maintain furnacedraught (-5 to -10mm.)

- PA fan current go up. - Maintain desiredairflow in furnace.

- PA header pressure goes upto 760 mm wcl, gradually.

4 INSTRUCT the localoperator to check

bearing Temperature& vibration locally.

- Limiting values of bearingtemperature and vibrations

- UCB OMNIGUARD & vibration indicators

must be regularly monitored when thefan is running.

Alarm TripFan 96oC 105oC

Motor 85oC 95oC

Vibration 2 mm/ sec. 3 mm / sec.

Motor winding temp. 110oC 130oC - DAS points

- There must be no abnormal

sound from the fan or bearings.

- Local check



KORBA SIMULATOR 99

WHEN ONE FAN IS RUNNING


1 CHECK before startingthe PA fan.

- All pre-start checksare COMPLETED.

- Local/UCB check.

- LOP: ON. Lub. oilpressure ADEQUATE(1.8 -2.5 KSC)

- Corresponding saffronlamp (permissive) on.

- Discharge damper (AD-15/16: CLOSED.

- UCB check.

- Regulating vanes arein MINIMUM position.

- Associated controller output is 0%.

- Bearing temperatureNOT HIGH (< 60 O C )

- Associated saffronlamp is on.

- FSSS start commandis AVAILABLE.

- Permissive.

- Local operator informed prior tostarting of the fan.

2 START the PA fanmotor.

- Breaker closedindication on.

- Red lamp is on.

- Fan current goes upto 700A and comesdown to no load

current of 70A.Discharge damper AD-15/16 open up.

-

3 INSTRUCT the localoperator to check

bearing vibration andtemperature locally.

- Limiting value of bearing vibration andtemperatures are:

- Vibration and theOMNIGUARD bearingtemperature indicatorsin UCB must bemonitored regularly.

Alarm Trip

Fan. 95oC 105oC

Motor 85oC 95oC

Vibration. 2 mm / sec. pk. 3 mm / sec. pk.

- There should be noabnormal sound fromthe fan/bearings,locally

- Local checks.



KORBA SIMULATOR 100

4 ADJUST the fan guide vanes to get desired PA header pressure andequalise fan loadings.

- Fan dischargepressure read approx.800 mm wcl.

- Maintain PA Header pressure760 mm wclconstantly

- PA header pressurerises to 760 mm wcl.

ADJUST the fan biasing and header pre. set point to 50% &80% respectively andtransfer vanecontrollers to auto.

- Header pressure and biasing set pointshave been providedover the IGV controllers of PA fan

A&B respectively.

- Biasing set point can be altered suitably tochange the fanloadings.

- IGVs of both fansmodulate to maintainset header pressure.

- Normal biasing is 50%for ensuring equal fanloadings.

SHUT DOWN PROCEDURE

WITH BOTH THE FANS RUNNING


1 TRANSFER the IGV controls to manual

- Manual modeindication comes on.

- Use the M/A release

2 STOP all thepulverisers in excess of three from the top.

- Three pulverisers only can be in service withone PA fan.

- If needed, stop morepulverisers, to maintainthe PA header pressure

at 760 mm wclCut-in oil support if odd combination of mills are running.

-

3 REDUCE IGVs of thefan to their minimumposition.

- Fan dischargepressure comes down.

- UCB indication.

- Notice the other fanloading going up, tomaintain the set header pressure.

- If needed keep thesecond fan also onmanual & maintain PA header pressure.

4 STOP the fan motor. - The fan breaker opens - UCB indication.- Discharge damper

(AD-15/AD-16), startsclosing.


- Regulating vanes go tominimum, position

- UCB/local check.



KORBA SIMULATOR 101

WITH ONE FAN RUNNING


1 SHUTDOWN allrunning pulverisers

one by one.

- Boiler total fuel flow starts decreasing.

- Adequate oil elevation must be cut-in before stopping

pulverisers.

- Oxygen percentage inthe flue gases startsincreasing.

- Ensure adequate FD fanloading & wind box dampers opening to prevent airflow from going < 30%tripping the boiler inadvertently.

- Associated mills coldair dampers start closing.

- Total airflow keepson decreasing.

- ID fan vanesmodulate (on auto),to maintain set furnace draught.

2 REDUCE the IGV of the PA fan to itsminimum position.

- PA fan dischargepressure startsdecreasing.

- UCB check only.

- PA header pressuredecreases to 400 mm

wcl, approximately.

- Maintain airflow andfurnace draught

3 STOP the PA fan &Rack-out the breaker if required for maintenance.

- Breaker openindication comes on.

- UCB indication.

- Guide vanes of bothPA fans will remainat minimumposition.

- Associated red lamps comeon.

- Discharge dampersof both PA fans go to100% open.



KORBA SIMULATOR 102

PULVERISER OPERATION

PRE-START CHECKS


1 CHECK that all thepulveriser start permissive issatisfied.

- Pulveriser START PERMIT is AVAILABLE. (Boiler total airflow is < 40% andall burners areHORIZONTAL).

- Alternatively, if anyonecoal feeder is proven thenstart permit will comefrom the proven feeder.

- Mill discharge valves at allfour corners are OPEN.

- UCB operation.

- Local feeder selector switch is ONREMOTE.

- Local operation/check.Not simulated.

- Mill tramp iron gate is100% OPEN.


- Cold air gate of the mill is100% OPEN.


- Pulveriser seal air valve is100% open.

- Local operation Not simulated. Seal air valveopens on interlock whenpulveriser is started.

- "No unsuccessful start"

permissive for pulveriser is ON.

- Refer to FSSS logics.

UCB check only

- "No pulveriser trip"command is present.

- UCB check. Refer toFSSS permissive

- Pulveriser PA Fan permit is AVAILABLE.

- Anyone or both PA fan onand PA header pressure700 mm WCL

- Mill ignition energy permit conditions are SATISFIED.

(Minimum 3 out of 4 gunnozzle valves in adjacent elevation are open andelevation oil flow is morethan 30% OR adjacent feeder speed is more than50% and boiler load ismore than 30%.

- Interlock. Refer to FSSSlogics for more details on

ignition energy conditionrequirements.



KORBA SIMULATOR 103

2 CHECK if thepulveriser is locally lined up for operation.

- All man and materialremoved from site.

- Local check.

- Pulveriser oil bath level is ADEQUATE

- Local check.

- Cooling water isolation valves to oil bath coolersare OPEN.


- Mill cold air and hot air dampers areOPERATIONAL and onREMOTE. Instrument air pressure is available

- Local check andoperation. Not simulated.

- Seal air to pulveriser differential pressure is125 mm wcl.

- UCB alarm andindication.

- Raw coalbunker level is ADEQUATE and bunker gate is OPEN.

- Local check/operation.

MILL STARTING PROCEDURE


1 CHECK these before starting any mill.


- UCB/Local check.

- All per missives are AVAILABLE.

- Local check lamps are on

- Electrical supply is AVAILABLE. Breaker isRACKED IN/REMOTEposition and feeder selection switch is inremote position.

- Local check. (Not simulated).

- Mill's cold and hot air dampers (CAD/HAD)CLOSED.

- CADs are <5% open.

- P.A. permit is AVAILABLE.

- Anyone PA fan 'ON' & PA Hdr pr. 770 mm wcl.



KORBA SIMULATOR 104

- Pulveriser on MANUAL MODE.

- If not, set on manual.

2 START thepulveriser.

- Pulveriser start red lampcomes on.

- It's a good practise tokeep primary header pressure control on

AUTO, so that at the timeof sudden openingof CAD, pulveriser doesnot trip(time delay 5 sec.)due to dip in the PA header pressure(585mm.).

- Pulveriser startingcurrent settles down at 12amps.

- Mill cold air damper opens 100%.

- Mill airflow 80 T/Hr.(app.).

- Mill differential pressuregoes up to 100 mm wclapproximately.

- PA header pressure dipsslightly until autocontroller opens the PA fan guide vanes.

3 OPEN theCAD/HAD tomaintain desiredairflow and milloutlet temperature.

- Hot air gate opentemperature increases.

- UCB check.

- Mill differential pressuregoes up to 100 mm wcl,approximately.

- Maintain mill outlet tempat 75 O C & mill airflow at 60 T/Hr

4 CHECK beforestarting the millfeeder.

- Coal silo gate is OPEN. - If not, get it opened.

- Feeder speed is MINIMUM(0% - 20%), correspondingto 9 T/Hr.

- Feeder start permissive.



KORBA SIMULATOR 105

- The entire mill permissiveis AVAILABLE.

- ''Pulveriser Ready'' lampindication is on.

- Mill outlet temperature >55 O C.

- Feeder start permissive.

- Mill ignition permit is AVAILABLE.

- UCB Check.

5 START the millfeeder.

- Feeder ON indicationcomes on.

- Maintain mill temp andairflow, asrecommended.

- Coal flow indicator reads9 T/Hr. approx.

- Maintain furnacedraught.

- Mill current startsincreasing.

- UCB check only.

- Mill outlet temperaturetends to come down.

- Control coal-firing rateto control mill outlet temperature.

6 RAISE mill feeder speed gradually.

- Mill differential pressuregoes up to 180 mm wcl. at 34 T/Hr. coal firing,depending upon coalquality & mill condition.).

- Watch the flame quality improving in coal flamescanners. If flame is not good, instruct the localoperator to check thefurnace flame and oilflame. If the need beincreased the HFO

pressure by adjustingHFO control valve (to

approx. 12 Kg/cm2.) to

improve flame quality.- Mill current goes up to 30

-32 amp. At maximumloading of 34 T/Hr.depending upon the coalgrindability (Hargroveindex).

- Mill outlet temperature

may tend to drop.

7 ADJUST flow &temp control set points to 70% and50% respectively and RELEASE millair control to auto.

- Flow & temp Control set points are provided over CAD & HAD respectively.

- Refer to ACS drawingsfor details of flow andtemperature controllersof the pulveriser.



KORBA SIMULATOR 106

- CAD & HAD modulates tomaintain 60 T/Hr.of airflow and 75 O C of milloutlet temperature.

8 CHECK the milllocally for any abnormal sounds,reject rate and return oilflow.

- There should be noabnormal hunting of millcurrent, which isindicative of foreignmaterial ingress, usually.

- Local check only.

Return oil continuousflow should be noticedthrough local Sight glass.

- Whenever the mill ampor DP is rising millrejects must beevacuated.

NOTE:

- Oil support can be withdrawn or reduced depending upon LOAD,IGNITION ENERGY and FEEDER PROVEN criteria.

- Operator must monitor continuously the mill temperature and bowl DP,

which should not exceed 95 oC and 200 mm wcl respectively.

- Before starting mill, operator must make sure water supply for oil bathcoolers.

- Mill outlet temperature should be in between 80 oC to 85 oC during

start-up. In no case it should be less than 60 oC and more than 90 oC.

- Coal feeding should be reduced if desired mill temp. is not maintained.(When hot air damper is 100% open).



KORBA SIMULATOR 107

MILL SHUTDOWN PROCEDURE


1 TRANSFER millfeeder and fuel

master controller to manual.

- Fuel master and feeder control transfer to

manual.

- M/A release push button must be pressed

for auto/manualchangeover.

2 REDUCE feeder speed to minimum,gradually.

- Coal flow to mill startscoming down.

- Maintain `milltemperature and airflow.

- Other running feedersstart loading up, tomaintain boiler loading, if on auto.

- Maintain loading on therunning mills by adjusting the fuelmaster.

3 STOP the millfeeder. - Feeder Off' indicationcomes on, in the millconsole.

- Associated green lampcomes on.

- Hot air gate closes with a time delay of 30 secapprox.

- UCB indication.

- Mill current anddifferential pressure start reducing as the mill

becomes empty,

gradually.

- UCB indication.

4 EVACUATE themill reject chamber locally and STOPthe mill.

- Mill temperature comes

down to less than 50oC.

- UCB check.Local operation.

- Mill CAD goes to <5%open

- UCB check.Interlock.

- Airflow to furnace dropsslightly.



KORBA SIMULATOR 108

TURBINE AND GENERATORSYSTEM OPERATION



KORBA SIMULATOR 109



KORBA SIMULATOR 110

VACUUM PULLING


1 CHECK before

starting vacuumpulling operation.

- Auxiliary steam header

charged and its pressure ADEQUATE.

- Aux. steam pr. must

be 14 Kg/cm2

- Ejector PRDS is CHARGEDand Ejector steam pressure is

ADEQUATE ( 7.5 Kg/cm2)

- “Ejector steam pr.low" alarm shouldnot be there.

- At least one condensate pumpis ON.

- UCB operation

- Main ejectors and GSCCHARGED from the waterside

(MC-11, 12, 13, 14, 19, 20OPEN & MC-15, 21 CLOSED).

- Local operation DAScheck points Refer

to condensatesystem.

- Condenser air valve CA-1/CA-2 & air valves to mainejectors, CA-3/CA-4, areOPEN.

- Local operation. Not simulated





KORBA SIMULATOR 112

gearing and theLub. Oil tempcontroller.

automatically by SGC OIL Start-upprogramme.

- Turbine starts barring at 110rpm approximately.

-

- Lub oil temperature controller modulates to maintain set luboil temperature.

4 CHARGEcondenser primingejector from steam& airside.

- AS-83, CA-15 & CA-16 areopened.

- Local operator DAScheck.

- Condenser water box priminginitiated.

5 INSTRUCT localoperator to start one CW pump andCHARGE bothcondensers 50 %approx., to curbCW power consumption.

- CW header pressureincreases, slightly.

- DAS indication.

- Condenser inlet & outlet valves are partially opened.

- UCB operation.

- Condenser flow startsincreasing.

- DAS indication.

6 CUTOUT thepriming ejector after CW water starts coming fromthe air vents of priming ejector.

- Priming ejector's steam andairside valves are closed.

- Local operation.

7 OPEN seal steamline and header drains & CHARGEgland sealing

steam into theturbine glands.

- AS-85 and SLC gland steamdrains are opened.

- UCB operation.

- Gland seal steam controlopens up and gland steamheader pressure startsincreasing.

- UCB operation.

TRANSFER seal - Seal steam pressure control - Maintain a pressure



KORBA SIMULATOR 113

steam control toauto.

transfers to auto mode. of 0.01 Kg/cm2

inthe seal steamheader.

8 CHARGE startingejector by openingejector’s steam

supply & air suction valve.

- Starting ejector steam supply valve AS-80/ AS-81 is opened.

- UCB operation.

- Air suction valve to startingejector (CA-5/CA-6) is opened.

- UCB operation after steam supply valveis 100% open

- Condenser vacuum starts

increasing to 0.7 Kg/cm2.

- UCB indication.

9 OPEN steamsupply valve to any one main ejector asper desired

vacuum.

- Vacuum builds up to 0.92

Kg/cm2

i.e 72 mm Hg (approx)

- UCB indication.

- Turbine barring speedincreases up to 220-RPMapprox.

- UCB check only.

- "Condenser vacuum low"alarm gets cleared off.

- UCB annunciation.

10 ISOLATE startingejector by closingair suction valvefirst and then

steam supply valve.

- Air suction valve (CA-5/CA-6),gets closed first.

- UCB indication.Interlock.

- Ejector steam supply valve(AS-0/As-81) is closed.

- UCB operation.

11 MAINTAIN ratedcondenser vacuumof 73 mm Hg (back pressure)

- Condenser vacuum is

maintained at 0.92 Kg/cm2.

- Condenser backpressure highalarm is at 150 mmHg and turbinetripping at 225 mmHg.



KORBA SIMULATOR 114

HP BYPASS AND LP BYPASS CHARGING


1 CHECK beforecharging HP/LP

bypass system.

- Boiler stop valves S-42 &S-64 are OPEN

- UCB operation.

- M S pressure 12 Kg/cm2. - UCB check.

- CRH and HRH steam linedrains are OPEN.

- UCB operation.

- HP bypass oil unit's oillevel NORMAL, its PumpON and its pressure

ADEQUATE.

- Local check.

- LP bypass rack is LINEDUP and all setting &tripping values checked.

- Local operation

- HP bypass downstreamtemperature set point isat 200 O C approx.

- Can be altered tomaintain desired HRHsteam temp.

- HP bypass spray pressure set point: 70

Kg/cm2.

- UCB operation.

- All isolating valves beforethe spray pressurecontroller are OPEN.

- Local operation/ check. Nsimulated.

- HP bypass upstreampressure (main steampressure) set point is at

10 Kg/cm2.

- Can be altered later tomaintain desired mainsteam pressure.

2 TRANSFER LP bypass control to

auto and SWITCH-ON the AutomaticControl Interface(ACI).

- LP bypass controltransfers to auto.

- UCB indication.

- HRH fixed set point

comes to 3 Kg/cm2.

- Refer to the text on LP bypass. (Volume-1)



KORBA SIMULATOR 115

3 TRANSFER HP BP control to auto.

- HP bypass controltransfers to auto.

- UCB operation.

- HP bypass valves (BP-1/BP-2) start opening if MS pr. is more than theset point.

- UCB alarm "HP bypass valves open" comes on.

- CRH pressure startsincreasing.

- UCB indication.

- HP bypass tempcontroller and spray pressure controller transfer to auto andmaintain set values of downstream temp &spray pressure.

- Interlock.

4 ADJUST mainsteam pressure set point to obtaindesired MSpressure.

- Main steam pressure ismaintained as per the set point.

- HP bypass consoleindication.

- HP bypass valves open or close, depending on

whether set point is lessor more than the MSpressure respectively.

- Biasing should bemaintained positive (set point less than MS Pr.)to ensure that HP

bypass remains open tomaintain sufficient steam flow in R/H

NOTE: -

1. MS pressure set point must not fall too much below the actual MS pressure;otherwise due to pressure interlock (error deviation + 10), a fast openingcommand is given to HP bypass control valves.

2. At 380 O C, HP bypass valves receive a closing command and their control tripsto manual. The temperature set point must be suitably altered to maintain thedesired HRH temperature.

3. For details on ACI (Automatic Control Interface) device, please refer to the text on HP/LP bypass system (Volume-1)



KORBA SIMULATOR 116

TURBINE START- UP

PRE-START CHECKS


1 CHECK that all theturbo-Supervisory instrumentations arefunctional.

- All UCB indicators andrecorders are functionaland healthy.

- If required, contact the related C&Iengineer for maintenance.

- All recorders are inked andall instruments arecalibrated.

2 CHECKS beforestarting the turbinerun-up

- Electro-hydraulic controller for turbine is ON.

- Electrical supply for the EHC must beON (C&I).

- EHC isolating valves on secoil lines to control valvesare open.

- Local operation

- Electro-hydrauliccontroller's output is zero.

- Indication ongovernor console.

- "EHC control fault" and"EHC Plunger coil off"alarms do not appear in theUCB.

- UCB annunciation.If alarms are on,inform C&Imaintenance

- Speed reference set point for the Speed Controller iszero or less than the

barring speed.

- If not, bring it downto zero. Theindication is onturbine governor console.

- Load reference set point for the Load Controller and theload limiter output arezero.

- If not, bring it downto zero.

- Speeder gear position is100%.

- If not, raise thespeeder gear position to 100%.

- Starting device is at 0%position.

- UCB operation.UCB indication.



KORBA SIMULATOR 117

- The alarms "TSE influenceoff" "Turbine stress effectsoff" and "Turbine stresscubicle fault" are not on.

TSE influence is ON.

- TSE influence can be made on fromturbine relay panels.Local operation.

- Unit trip relay (A & B) arein RESET condition

- If not, reset UTRsafter resetting MFR.GTRs and checkingif stator water flow &conductivity arenormal (UTR reset permissive)

- "Turbine Trip" and "Turbine Trip gear operated" alarmsare not on and Trip oil

pressure > 5 Kg/cm2

- UCB check only

All differentialexpansions of theturbine are NORMAL and within the alarms

values

Alarm Trip

HPT +4.5mm +5.5mm

-2.5mm -3.5mm

IPT +5.0mm +6.0mm

-2.0mm -3.0mm

LPT +25 mm +30 mm

- 5 mm - 7mm


NORMAL. 0.92 Kg/cm2

approx.

- "Condenser vacuumlow" (150 mmHg) &"Turbine electricprotection for low

vacuum" (225 mmHg) are not ON.

- Turbine SLC Drains is ONand NOT FAULTED. "SLCDrains fault" Alarm is not ON.

- These drains can beswitched ON/OFF from the SLCsection on turbinepanel.



KORBA SIMULATOR 118

- Turbine stop valves (ESV-1&2, IV-1&2). Control

valves (HPCV-1&2), IPCV-1&2). Extraction block

valves (ES-1,2,3,7,5,6) areCLOSED.

- Check from bothUCB indicators andlocal indicators.

- Extraction NRV's (A2, A3, A4, A5) and CRH lineNRV's L/R are CLOSED.

- UCB indication.

- The turbine is on BARRINGand there is no abnormalsound from the turbine &its bearings.

- Gate valve gearing isopen.

- The Speed of rotation of shaft is between 200 and220 rpm.

- UCB indication.

- Turbine "Control oilpressure" is greater than 5

Kg/cm2

- Normal value is 6.5

to 6.8 Kg/cm2 with AOP and 7.5-8.5

Kg/cm2 with MOP.

- Turbine lub oil temperatureafter coolers is normal i.e.

45oC. (40oC + 5O C )

- UCB indication.

- Lub oil pr. is normal at 3.5

Kg/cm2 before coolers.

- UCB check

- Main oil tank level isNORMAL.

- Local check. Normal value is zero.

- Thrust bearing oil filtersare NOT CHOKED.

- Local check.UCB alarm reset.

3 CHECK that theentire turbine MSstrainer drains CRHdrains HRH strainer drains and ESV & IV

before seat drains areopen.

- MS strainer drains(DW-51/52/53/54) to flashtank are OPEN.

- Indications of allelectrical drainsavailable in UCB. Incase anyone is not open (indicated by green lamp on),open the same withthe respectivecontrol switch.



KORBA SIMULATOR 119

- CRH drains(DW-160/161/162/163) toflash tank are OPEN.

HRH strainer drains toflash tank,(DW125/126/131/132) areOPEN

ESV & IV before seat drainsto flash tank (DW-121/122/123/124 and DW-127/128/129/130) areOPEN.

4 CHECK that thegenerator seal oil andstator water systemare in service andhealthy

- Generator hydrogenpressure is NORMAL, more

than 3 Kg/cm2

- 3.5 Kg/cm2

max.UCB/localindication.

- Seal oil pressure (turbineand exciter side) is more

than 4.8 Kg/cm2

- UCB check

- Seal oil to hydrogen DP is

NORMAL (1.2 Kg/cm2)

- UCB recorder.

- Stator water flow is more

than 23 m3/Hr.

- Normal value is

27 m3/Hr.

- Stator water specificconductivity is less than 1micro mho/cm.

- Maximum allowable value is 5 micromho/cm.

- Stator water pressure is

NORMAL. (2.8 Kg/cm2)

- UCB / localindication

- Generator and field breakers are in RESET condition and Generator /Field breakers tripped" &"Generator trip relay operated" alarms are reset.

-

-

UCB operation.

UTR reset permissive



KORBA SIMULATOR 120

TURBINE ROLLING PROCEDURE


1 CHECK turbine start-up criteria as

determined from the X-curves.

- Main steam, at the turbineinlet should have minimum

of 50 oC superheat.

- Applicable during allturbine start-ups.

- M.S. pressure is 30 KSC

approx. & temp. 280oC

- For cold start-uponly.

- Criteria for Openingthe ESVs.

- Max/Min. SH steam temp.depending upon mid walltemp. of HPCV.

- Start-up curves X-1, X-2 and X-3

- Rolling to warm-upspeed of 600 rpm.

- Max. MS temp dependingupon saturated steam tempand mid body temperature

of HP casing/ shaft

- Start-up curves X-4and X- 5.

- Rolling up to ratedspeed of 3000 rpm.

- Required minimum meanmetal temp of H.P Shaft depending upon availableMS temp.

- Start-up curve X-6

- Loading the turbineafter synchronisation.

- Required minimum meanmetal temp of IP shaft,depending upon theavailable HRH steam temp.

- Start-up curve X-7

2 Maintain boiler side

steam parameters asrequired for turbinestart-up.

- The MS/HRH temp and

pressures are within thedetermined ranges.

- UCB indicators are

available for all these values.

- HRH steam pressureshould not be more than

15 Kg/cm2

during rolling.

- Low HRH pr. duringstartup is to prevent HP exhaust temprising too high.

3 RAISE starting deviceto 70% gradually.

- Start-up oil pr. Falls to 1.8KSC and HP ESVs (1&2)open 100% at 42% positionof starting device.

- UCB indication onturbine governor console.

- Interceptor stop valves(1&2), open 100% at 56%position of starting device.

- UCB indication onturbine governor console.

- Start-up oil pre. = 0 at 70%of starting device position.

- UCB indication.



KORBA SIMULATOR 121

Aux Sec oil pressureincreases up to 4 KSC

UCB indication

4 SWITCH ON SLC"Warm-up controller"is required (duringcold rolling)

- Drains before HP control valves, (HPCV-1/2), start opening, 100%.

- Refer to the SLClogics.

- HP ESVs and control valves, heating starts andtheir respective temp. start increasing.

- Surface and meantemp start rising.Indicated on TSErecorders.

- Wait until the meantemperatures of HPCVs

come to min. 200 - 250 oC.

- Min. temprequirement for HPSV /HPCV is only for absolute cold start-ups

- Upper TSCmargin for admission channel startsdroping slowly & after minimum temp areattained, starts improvingagain.

- Maintain all TSEmargins of Admissionchannel > 30 K.

- The metal temperatures of ESV/CV body are within

30oC of the MS temppreferably.

- The heating-up of stop/control valves iscomplete.

5 RAISE speed

reference set point to600 rpm.

- EHC starts increasing from

its initial zero position.

- Speed controller is in

action during turbinerolling.

- HP CVs start opening. - UCB indication.

- Turbine speed starts risingto 600 rpm at a rateselected by TSE.

- TSE/UCB indication.

- The gate valve for turbine barring starts closing whenturbine speed comes to 240rpm. "Gate valve gearing

not closed" alarm startsflashing and resets after the valve gets fully closed.

- Refer to the SLClogics for gate valvegearing.

- The JOP trips in auto asthe turbine speed comes to540 rpm.

- Refer to SLC logics for JOPs.UCB indication.



KORBA SIMULATOR 122

6 MAINTAIN turbinespeed and soak tillrequired HP shaft temp is attained.

- DT (MS temp. – Mean HPshaft temp) becomes lessthan the value specified by turbine start-up graphs.

- Start-up curve X-6.

- HP shaft mean temp becomes steady after 40minutes (approx)

- Maintain all TSEmargins more than30 K.

7 RAISE turbine speedreference set point to3030 rpm.

- Turbine EHC's output starts increasing slowly.


- Turbine control valves(HPCV & IPCV) start opening more.


- Turbine speed startsincreasing gradually at a rate decided by turbine

stress evaluator.

- Ensure TSE marginsto ensure a min.speed gradient of >

108 rpm /minute toavoid DN/DT protection.

Critical speeds.(RPM)

- "Turbine/Gen. bearing vibration high" and"Turbine absolute shaft

vibration high" alarms flash when turbine speed crosses1400 rpm and 2200 rpm(approx.) and vibrationlevels increase appreciably

and again become normal

-

137015442125

Bearing temperaturesdisplay an upward trend

- If vibrations arealready on higher side

before the criticalspeeds, DO NOT ROLL and soak at 600 for some moretime until vibrations

become normal.

8 MAINTAIN turbine

speed. Soak untilrequired IP shaft temp is reached andSET load reference at 20-40 MW and loadgradient at 10 MW /Minute (Max).

- DT (HRH steam temp-

Mean IPS temp) becomesless than the valuespecified by turbine start-up graphs.

- Start-up curve X-7.



KORBA SIMULATOR 123

- Load limiter set point must be more thanload ref.

- Load controller is set at 20-40 MW to ensure speedcontroller transfers to loadcontroller after synchronising.

- Refer to the generator loadingrecommendations.

- CHECK all theturbine / generator parameters beforesynchronisation.

- All bearing pedestal vibration is less than 35microns.

- UCB/DASindications.

- All relative shaft vibrationsare less than 150 microns

- UCB/DASindications.

- All bearing babbit metal

temp are less than 80oC

- UCB/DAS indication.

- Bearing return oil flow is

normal and temp < 77 oC.

- To minimise ageing of turbine oil.

- All casing absoluteexpansions are withinnormal range.

- HPT - < 15 mm.IPT - < 10 mm.

- Thrust bearing oil filtersare clean (not choked).

- Local checks.

- Axial shift < + 0.3 mm. - UCB indication.

- Turbine casing top/ bottom

temperature is< 30 oC.

- UCB indication.


normal at 0.92 Kg/cm2

- UCB check.

- Gen hydrogen pressure isnormal at 3.5 KSC

- Local/UCB check.

- Stator water flow is More

than 27 m3/Hr.

- Local/UCB check.

- Stator water specificconductivity is less than 5micro mho/cm.

- UCB check.

- Seal oil to hydrogen DP is

normal (1.2-1.50 Kg/cm2).

- UCB check.



KORBA SIMULATOR 124

GENERATOR SYNCHRONISATION


1 CHECK all thegenerator Parametersare healthy

- Stator cooling water flow more than 21 T/Hr.

- UCB indication

- Stator cooling water temp

less than 40 oC.

- UCB indication

- Cold end hydrogen temp

less than 40 oC

- UCB indication

- Seal oil pressure at turbineand 5.0 KSC

- UCB indication

- Seal oil pressure at exciter

end 5.0 KSC

- UCB indication.

- Seals oil D.P. between1.2 -1.5 KSC

- UCB indication

Generator stator water specific conductivity is less

than 5 µ mho/cm

UCB indication.

Alarm: 12 µ mho/cm Trip: 20 mho/cm

Gen. hydrogen and stator water coolers are chargedand ''Clarified water pressure to hydrogen &stator water coolers low''alarm is not on.

Local operation.Remote function.

2 CHECK before closingthe field breaker

beforesynchronisation

- Turbine RPM is more than2980 rpm. Generator isolators are closed fromswitchyard.

- UCB & switchyardoperator'sresponsibility/ UCBindication

- Generator excitation controlis on REMOTE.

- Field breaker doesnot close from UCB if control is on local.

- Generator excitation controlis on MANUAL OR AUTO.

- UCB indication.

- AUTO/MANUAL excitationcontrollers are on HOMEposition.

- Associated whitelamp is ON. If not,lower it down tohome position.



KORBA SIMULATOR 125

3 CLOSE the generator field breaker.

- Generator field breaker getsclosed & Generator voltageincreases to 10 KV, 15.75KV approx. on manual /auto excitation control,respectively.


- Field current and voltagealso increases 700 A &90 V respectively

- UCB indication

4 RAISE generator excitation manually,to raise gen. voltage.

Generator voltage comes to15.75 KV approx.

UCB indication.

- Field current and voltageincrease to 900A & 105V respectively.

- UCB recorders.

- Generator gas and rotor winding temperatures start increasing.

Maintain all temps within LIMITS.

Alarm TripCold gas temp. (HI) 47oC -

Hot gas temp. (HI) 52oC 75oC

Rotor wdg. temp. (HI) 85oC 110oC

5 CHECK all thegenerator voltages(phase to phase).

- All the three phasesshould read equal voltages

- UCB indication

6 SWITCH-ON thesynchroscope toCHECK mode.

- IN-COMING/RUNNING voltages and frequenciesstart showing on their Corresponding meters.

- UCB indication &operation.

- Alternatively synchroscope is put onCheck mode and autosynchroniser can beswitched on.

- Synchroscope needle startsrotating at a rateproportional to difference

between the generator andgrid frequencies.

- If the direction of rotation is clockwisethe incominggenerator frequency is higher than the

grid & vice-versa.

7 ADJUST turbine speedreference to matchgenerator freq with thegrid (running).

- Incoming and gridfrequencies should becomeequal.

- Synchroscopeindications.



KORBA SIMULATOR 126

- Synchroscope needle slowsdown as the frequenciesmatch.

- Incoming freq. must be higher than that of grid beforesynchronising.

8 ADJUST generator excitation to match the

gen. voltage with that of grid.

- Grid and generator voltages start

matching.

- UCB/synchroscopemeter readings.

- As synchroscope needlecomes to 11'O clock position (clockwise), thegreen CHECK lamp comeson & the red lamp goes off.

At 12' O clock position thecheck lamp goes off andred lamp comes on again.

- With synchroscopeon check mode thegenerator can besynchronised(breaker closed) only

when the green lampis on.

9 CLOSE the generator

breaker when thecheck lamp is green.

- ''Generator Breaker'' gets

closed, if all parametersare matching during the''close'' command.

- If the breaker fails to

close.'' Gen. Breaker Trip'' alarm comes on.re-set and try again.

- ''Generator motoring'' alarmcomes on.

- Synchroscope needle getslocked in 12'O clock position.

- Synchroscope redlamp stays "ON"

- Generator line charging

MVAR (approx.-80 MVAR)indication comes on.

- Power factor becomes

leading for somemoments and

becomes unity againdepending upon thegen. Load andexcitation.

9A INCREASE StartingDevice to 100%

Starting device comes to100 %.

UCB indication.

10 RAISE speedreference slightly to

increase Gen load,immediately after closing the generator

breaker.

- Turbine load increases to20 MW approximately.

- Speed reference can be operated from

generator desk if the ATRS selector switchis on UCB mode.

- ''Generator motoring'' alarmclears off.

- UCB indication



KORBA SIMULATOR 127

- ''Speed controller'' transfersto 'Load controller'' after some time delay.

- UCB indication

11 RAISE excitation autoset point until theexcitation null voltage

becomes zero and TRANSFER excitationto auto.

- Excitation null voltage becomes zero.

- UCB indication.

- Automatic voltage regulator gets transferred to Auto.

- Manual channel backs the autochannel if AVR is on.

12 CHECK all thegenerator parametersare OK and allphases show equalcurrents.

- Generator windingtemperatures less than 85O C (alarm.)

- UCB indication.

- Generator transformer winding temp less than90 O C (alarm.).

- UCB indication.

- Rotor winding temp are lessthan 85 O C (alarm).

- UCB indication.

- Gen. cold gas temp is lessthan 47 O C (alarm).

- UCB recorders.

- Hydrogen cooler inlet water temp is less than 36 OC(max.)

- Local/DAS check.

- Hydrogen cooler outlet water temp is less than 43OC. (max.).

- DAS/Local check.

- Stator water temp at theinlet of stator is less than44 O C (maxi.).

- DAS/Local check.

- Stator water outlet temperature is less than 70OC. (max.)

- UCB/Local check.



KORBA SIMULATOR 128

UNIT SUPPLY CHANGEOVER FROM STATION TO UAT


1 CHECK beforechanging over

6.6 KV bus supply station to unit auxiliary transformers.

- Unit load is more than 40MW

- UCB check.

- All HT buses incomer breakers from UATs are inSERVICE/REMOTEposition.

- Local operation.Must be done beforeclosing field breaker.

- UATs (A&B) on load, tapchanger gearbox oil levelsNORMAL.

- Local check.

- UATs conservator tank oillevel ADEQUATE.

- Local check.

- UATs cooler cubicle power supply is normal.

- From TG MCC.

- UATs breather silica gelcolour NORMAL.

- Local check.

- UATs mulsifire system

AVAILABLE. Its air pressure and water pressure NORMAL.

- Local

check/operation.

2 SWITCH-ONsynchroscopeto CHECK mode.

- RUNNING/INCOMING voltage comes on andindications come on.

- UCB indication.(Synchroscopeswitch CS-1006, S-20 and CS-1007, S-26 for bus A & Brespectively).

- Unit synchroscope red lamp

comes on and needle comesto its zero vertical position.



KORBA SIMULATOR 129

3 ADJUST OLTC (onload tap changer) of the UAT (A or B) tomake incoming

voltage equal torunning voltage.

- Synchroscope green lampcomes on after the two

voltages are matching

- Without the greenlamp CHECK that associated breakerscannot be closed.

- Incoming/running voltageand frequency indicationsmatch.

- UCB/Synchroscopeindication.

4 CLOSE UAT (A/B)incomer to Unit bus.

- UAT incomer to bus breaker gets closed.


- ''Unit/Station transformersparalleled'' annunciationcomes on.

- UCB annunciationGenerator panel

5 Immediately OPENthe station breaker.

- Station breaker opens up. - Associated greenlamp comes on.

- ''Unit/Station transformersparalleled'' alarm clears off.

- UCB annunciation.

6 ADJUST OLTC &MAINTAIN Unit bus(A/B) voltage at 6.6KV.

- UAT winding temperaturestarts rising.

- Alarm 85 0C UCBindication

NOTE: For changing-over the supply from UATs to station or station to UATS useappropriate synchroscope switches. OLTC operation of station transformer is not simulated. In the reference plant the same is operated from CSSAEPpanel located in UCB-1.



KORBA SIMULATOR 130

LP HEATERS CHARGING


1 CHECK theseconditions aresatisfied beforecharging the LPheaters.

- Generator load is at least 40 MW.

- UCB check only.

- All LP heaters areCHARGED from watersideand their bypass valves areclosed.

- Local check and localfunction.

- All LP heaters airline tocondenser, are OPEN.

- Air vents not simulated

- Local operation, not simulated.

- All pneumatic drain valvesare OPERATIONAL & onREMOTE.

- Localoperation/check.

2 OPEN LPH-1Extraction steam

block valve ES-1.

- LPH-1 extraction block valves opens.

- UCB operation.

- Condensate temperatureacross LPH starts rising.

- DAS/Local check.

3 OPEN LPH-2extraction block valveES-2.

- LPH-2 extraction block valve goes open

- UCB indication

- Associated line drain valveDW-83 starts closing after the extraction block valveopens 100%.

- Interlock.

- LPH-2 alternate drain tocondenser HD-14 startsclosing.

- Interlock.

- "LPH-2 level low" alarmclears off.

- UCB annunciation.



KORBA SIMULATOR 131

- LPH-2 normal drain valveHD-11, starts modulatingto maintain the level.

- Associated Green/redindication come on.

- Condensate temperatureafter LPH-2 starts rising(DAS check).

- Levels can bemonitored locally only.

4 OPEN LPH-3extraction block valveES-3.

- LPH-3 extraction valve ES-3goes open 100%

- UCB indication.

- Associated line drain valveDW-80 starts closing after ES-3 opens 100%.

- Interlock.

- Alternate drain valve HD-19starts closing.

- Interlock

- "LPH-3 level Low" alarmclears off.

- UCB annunciation.

- LPH-3 normal drain valveHD-16 starts modulating tomaintain the LPH-3 level.

- Associated green andred lamps start glowing.

- Condensate temperatureacross LPHs starts rising.

- DAS/Local check.

5 INSTRUCT localoperator to throttle allLPH's airlines tocondenser and check LPHs levels.

Airlines can be fully isolated after 80 MW load.

It is preferable that allfeed heaters beevacuated at least once in the shift by opening their respective side air

vents to condenser

LPHs levels are maintained within alarm limits



KORBA SIMULATOR 132

HP HEATERS CHARGING


1 OPEN extractionsteam block valve ES-

7 to Deaerator.(Extraction to DA ischarged immediately after 40 MW)

- Extraction block valve ES-7opens 100%.

- UCB indication.

Associated line drain valveDW-79 closes 100%

- UCB check.Interlock.

- De-aerator pressure

increases to 4 Kg/cm2

(approx.)

- At higher loads DA pressure varies withIPT exhaust pressure.

2 ADJUST Deaerator pre. set point to 35%( 3.5 KSC) & releaseits control to auto.

- D/A pressure set point isprovided over D/A pr. controller.

- Use M/A release

- D/A pre. controller valvestarts closing if extractionsteam pre. is >3.5 KSC.

- UCB indication

3 CHECK beforecharging the HPH-(5&6).

- Unit load is more than120 MW.

- UCB check only

- HPHs inlet/outlet valves

(FW-43/44/46/47) areOPEN and individual

bypass valve FW-45/48 areCLOSED.

- Give ''In-Service''

command to HPHsafter opening ventson the feed water lines of HP heater.

- HPHs group bypass valvesare IN-SERVICE positionand "HPHs bypassed" alarmis NOT On.

- FW-34/35, the group bypass valves can beoperated (de-energised) from UCB.

And opening of pressurising valvelocally cause group

bypass to open, incase they are not open previously)

- All HPHs shell drains areOPEN.




KORBA SIMULATOR 133

- All HPHs airlines tocondenser isolating valvesare open.

- Local operation. Not simulated

4 OPEN HPH-5 extr.steam block vlv ES-5.

- Extraction steam block valve ES-5 opens 100%.

- UCB indication.

- After ES-5 is open, extr.line drain DW-73 closes. - Interlock.

- HPH-5 alternate drain tocondenser HD-31 closes

- Refer to theassociated logics.

- "HPH-5 level low'' alarmclears off.

- HPH level start building-up.

- HPH-5 normal drain to D/A starts modulating tomaintain the level.

- Level checks localonly.

- Feed water temp after HPH-

5 starts increasing.

- DAS/local

indications.

5 OPEN HPH-6extraction steam

block valve ES-6.

- Extraction block valveES-6 opens 100%.

- UCB indication.

- Extraction line drainDW-74/75 valves close.

- UCB indication.Interlock.

- HPH-6 alternate drain tocondenser closes and''HPH-6 level low'' alarmclears off.

- Interlock. UCBannunciation panelindication.

- HPH-6 normal drain to D/A HD-51 starts modulating tomaintain HP heater level.

- Level checks localonly.

- Feed water temp after HPH-6 starts increasing.

- DAS/localindications.

6 INSTRUCT localoperator to close allfeed line vents andshell drains of the HPheaters.

- NOTE: HPH-6 drain toHPH-5 can be charged,provided extraction steampressure to HPH-5 is morethan 3 KSC and there is no''level high'' command in

HPH-5 (Block valve HD-39can be opened).

- UCB operation &ckeck.

NOTE :Isolating valve of Group Bypass charging line (pressurising line) locally hasto be opened. This only causes group bypass to operate after some time.''HPHs bypass'' indication is from the group bypass valve limit switch, not from the solenoids.



KORBA SIMULATOR 134

SUPERHEAT AND REHEAT STEAM TEMP. CONTROL


1 OPEN super-heater and reheater spray

water header block valves.

- Super-heater block valveS-80 and re-heater block

valve R-40 is opened 100%.

- RH block valves: DCsolenoid operated

and the SH block vlv are motor operated.

2 OPEN S/H and R/Hattemperation block

valves, one stream A & B.

- S/H attemperation block valves S-83/S-86 onstream-A & S-89/S-92 onstream-B open 100%.

- Associated red lampsare on. One block

valve each on stream A&B is to be opened.

- R/H attemperation block valves R-43/R-46 onstream-A and R-49/ R-52on stream-B open 100%.


- Manual/auto releaseflickering stops, enablingthe releasing of associatedcontrollers to auto.

- UCB indication.

3 OPEN Manualisolating valves after control valves (A & B)

- Valves S-88, S-85, S-91,S-94 and R-48, R-45, R-51and R-54 are open

- Local operation. Not simulated. DASindication.

4 OPEN S/Hattemperation control

valves.

- S/H attemperation flow increases.

- UCB recorders.

- After attemperationtemperature startsdropping and the difference

between before & after attemperation startsincreasing.

- UCB recorders.Maximum diff.

permissible is 50oC.

5 ADJUST S/H outlet temp set points to

90% each. (540oC).

- S/H temperature set pointsare provided over respectivecontrollers.

- M/A release must bepressed for manualto auto transfers.

- ADJUST hot reheat temp set point to 90%and biasing set point to 50%.

- Hot reheat temperature set point is provided over

burner tilt controller.

- Auto controller for SH/HR temp trips tomanual if BFP DPacross FRS is >20KSC





KORBA SIMULATOR 136

SOOT BLOWER OPERATION


1 CHECK theseconditions beforesoot blowing.

- Boiler load is more than75%.

- Furnace stability criteria.

- Furnace flame is STABLE. - If not, cut in oilsupport.

- Soot blower MCC power supply (220V) is ON.

- Supply is provided inthe Boiler MCCpanel.

- Soot blowers control supply (415V) A/C) is ON.

- All blowers are in 'HOME'

position.

- No red lamp

indication should be'on' on the UCB panel.

- Soot blower header drain valves are in OPEN position.

- UCB operation

- Main steam inlet isolating valves to soot blower system, SB-108/SB-109 areCLOSED.

- SB 109 is UCBoperated.

- SB 108 is locally operated (not

simulated).

- Soot blower steam pressurecontrol valve SB-4(pneumatic) isOPERATIONAL and itsimpulse/root valve is OPEN.

- Root valve not simulated.Pneumatic pressurecontrol valvemaintains approx. 20

Kg/cm2 of steam

pressure tapped off from SH header No.10.

- Uni-selector (stepper) relay is in its STARTINGPOSITION.

- Sequence Completeindication is ‘ON’ onthe soot-blowingpanel.



KORBA SIMULATOR 137

- Soot blowers' selectionswitches should be on

AUTO or BY-PASS positionsas per soot blowingrequirements.

- Individual switchesare provided on theUCB soot-blowingpanel.

- Individual blowers' overloadtripping must be RESET'. (If operated)

- Local operation fromindividual blower MCC. Not simulated.

- Blower control panelselector switch is on'PANEL' position.

- UCB operation

2 OPEN electricalisolating valveSB-109 completely.

- SB-109 opens up 100% - UCB indication lampcomes on.

- Steam pressure andtemperature gradually raise

to approx. 20 Kg/cm2 and

280 oC respectively.

- 'Pr. Low' and 'Temp.Low' indication getsreset on the soot

blowing panel.

- OPEN manualisolating valve SB-108 gradually for

warming up lines.

3 CHECK steamtemperaturein all the four drain'points by operatingthe selector switchprovided on thepanel. CLOSE all thefour drain valvesonce the requiredsteam temperatureis achieved.

- Temperatures in all four-drain lines must be greater

than 220oC

each.

- Temp low is a sequence interruptingprotection/ condition.

- All four-drain valves on soot blower header are CLOSED.

- UCB operation.Drains closed is anInterlock/Permissive for sequence starting.



KORBA SIMULATOR 138

4 PUSH ' Reset' PushButton on UCB soot

blower panel andthen SEQUENCESTART push button.

- ''Soot blower systemtrouble'' alarm clears off

- UCB indication.

- 'Pressure/temp low' alarmsget reset.

- UCB indication onsoot blower panel.

- ‘‘Sequence On’’ indicationscome on. Wall soot blower leaves its 'HOME' positionand advances to itsoperating position (providedit is selected on (AUTO).

- Red indication comeson the soot blower panel.

- Steam header pressure dipsslightly as the soot blower opens.

- Steam pressuremaintained by thePressure control valve.

- After approximately 1.5min. the blowers retracts toits home position.

- RED indication goesoff.

- Next blower on Auto comesinto service with a timedelay of 3 seconds andsequence continue. One

blower at a time.

- Total 56 nos of wall blower are provided inthe boiler, each with a

blowing time of 1.5minutes.

NOTE :

1. LRSBs are numbered from 57 onwards up to 80 for soot blowing in platenS/H, final S/H, horizontal S/H and economiser respectively.

2. Blowing time for LRSBs is approx. 8 min. and blowing operation for LRSBcontinues right from the moment it leaves its home position unlike wall

blowers in which case, blowing starts after the blower reaches blowingposition.

3. APH soot blowing is also possible through auto sequential operation besides independent/manual operation with aux. steam. Their total blowing time is approx. 45 min. and blowing takes place only during theforward stroke.

4. Recommended frequency for wall blowers is once a shift, for LRSBs it isonce a day and for APH soot blowers during oil firing or whenever thegas/air DPs across APH exceed the normal value by 30-40 mm wcl.



KORBA SIMULATOR 139



KORBA SIMULATOR 140

UNIT COLD START-UP



KORBA SIMULATOR 141



KORBA SIMULATOR 142

UNIT COLD START UP PROCEDURE

ACTION OBSERVATION REMARK

1. CHECK all pre-start conditions aresatisfied beforestarting the unit from cold.

- All work permits on main boiler, all electrical panels,all aux. Systems areCANCELLED

- Refer to the PTW record book andunit controller'slogbook.

- All man/materials areREMOVED from equipmentsand site.

- Local checks.

- Lube oil levels in bearingand MOT/oil tanks are

ADEQUATE.

- Local Checks. Not simulated.

- Clarified/Raw water pumpsare ON and water systems

are LINED-UP.

- Local checks/operation.

Not simulated.

- Ash hopper sealing/ flushing water Supplies are AVAILABLE.

- HP/LP water pumpare ON Not simulated.

- Service/Instrument Air Pr.

ADEQUATE (7-8 kg/cm2).

- Local operation.UCB indications.

- Water treatment division has been INFORMED and DM water storage is ADEQUATE.

- Shift-charge’sresponsibility.

- Generator hydrogen fillingsystem is LINED-UP.


- Generator seal oil system isline-up.


2 OPEN all drains/ vents on aux. steamheader & line-up unit aux. steam hdr for charging.

- Valves AS-5, AS-6 AS-8, AS-9, AS-10 are OPEN.

- Local operation.Not simulated.

- All aux. steam (unit) supply

valves AS-11/ 12/ 13/ 14/16/17/18 19/32 are OPEN.

- Local operation.

3 OPEN AS-31, theinterconnection

between aux. steamhdr of U#1, U#2, U#3.

- Unit aux. steam pressure

starts rising to 13 kg/cm2

- UCB indication.



KORBA SIMULATOR 143

- Aux. steam temperature goes

up to 220oC (approx.)

- DAS/UCBindicated.

4 CLOSE all associateddrains and vents onthe aux. steam

header

- All aux. steam hdr drains & vents are closed after theaux. steam header reaches

to 2-3 kg/cm2

- Local operation.Not simulated.

5 INSTRUCT localoperator to chargeseal oil system andthen hydrogencylinders intogenerator casing.

- Hydrogen pressure in thegenerator starts rising and

comes to 3.5 kg/cm2

(approx.) H2 pressure will be

raised to 3.5 kg/cm2 only

after achieving the gaspurity. Before that pr. is to

be maintained 2 to 3 kg/cm2

to reduce H2 consumption.

- Local/UCB check (If air is filled-up thenCO2 must be

charged to expel theair and after recommended CO2purity is achievedhydrogen filling isstarted.

Seal oil to H2 DP is to be

maintained at 1.2-1.5

kg/cm2

UCB indication.Local operation.Not simulated.

6 ENSURE before boiler filling, allpreparations have

been made

- At least one condensate andone boiler feed pump isLINED-UP and READY for operation.

- Refer to therespective operationinstruction.

- Condensate and feed water

systems areLINED UP.

- Local/UCB checks.

Economiser and super-heater air vent are OPEN

Local operation.Not simulated.

Drum air vents and SH/RHstart up vents are OPENfully.

Local UCBoperation.

Drum emergency blow-down valves B-82, B-83 andintermittent blow down

valves B-105, B-106 areCLOSED.

UCB operation.



KORBA SIMULATOR 144

CBD and low point drains(LPDs) are CLOSED.

Local operation(Remote functions).LPDs not simulated.

HP/LP chemical dozingstations are LINED-UP &

AVAILABLE.

UCB operation &local checks.

Boiler Economiser re-circulation valves E-27, E-29are OPEN.

UCB operation.Not simulated.

Aux steam connection toD/A, AS-64 & AS-16 isOPEN.

UCB/Local check.

D/A pressure set point is at 10%-15%. (Corresponding to

1.5 kg/cm2 DA pressure)

UCB operation.

D/A storage tank heating valves AS-76, AS-77 areOPEN.


Isolating valves of D/A pr.controller, S-66, AS-67 areOPEN.


7 START one CEP for

D/A filling, after filling the condenser hot well.

Deaerator level starts

increasing and comes up to1500 mm wcl.

UCB indication

Maintain D/A and Hotwelllevels at 1500 mm & 500mm wcl respectively

UCB Operation.

8 CHARGE D/A feedstorage tank heating

by opening AS-78slightly and transfer

D/A pr controller toauto control after DA pressure is 1.5

kg/cm2.

D/A feed storage tank water temp starts rising.

DAS indication.

D/A pressure starts building

up to 1.5 kg/cm2, gradually.

AS-78 not simulated. Localoperation.



KORBA SIMULATOR 145

DA pressure controller maintains the set pressure.

Set point can beraised to 20% and40% at TG loads 40MW and 80 MW respectively.

9 START one BFP to fill-up the boiler by operating low rangefeed control valve.

Drum level starts increasinggradually.

UCB/DAS/Localindications.

Maintain drum level at (-) 60mm wcl before boiler light-up

Boiler fill pumpconnections to DA economiser, SH and

boiler W/W ringheader for direct fill-in, is not simulated.

10 START one LP dozing(hydrazine) pump andadjust its stroke asrequired, after feed

water temp comes to

150oC.

Hydrazine concentration before economiser startsrising after some time (max.0.05 ppm).

UCB checks.

Oxygen in feed water to bemaintained 0.007-ppm max.

As per boiler manufacturer’srecommendations.

11 START one HP dozing

(phosphate) pump if drum water pH valueis lower thanrequired.

PH value of drum water to be

maintained at 9.0-9.4.

UCB indication or

chemist'srecommendations.

Residual phosphate to bemaintained at 5-10 ppm. at full load.

UCB check andindications.

12 ENSURE all pre-start Conditions for purging and light up

are satisfied.

Both APHs are IN-SERVICE UCB operation.

One set of ID &FD fans andassociated air & flue gassystems are lined-up andIN SERVICE.

Refer individualoperatinginstructions.



KORBA SIMULATOR 146

All wind-box dampers areOPEN.

UCB/Local checks.

All purge per missives areON.

UCB checksoperation.

Two HFO and one light oilpumps are IN-SERVICE.

Local operation.(Remote functions).

Aux. steam to atomisingsteam hdr, HFO heating andSCAPH, is CHARGED.

Local operation.(Remote functions)

All drum. SH, RH air & start-up vents and drains areOPEN.

Start up vents isUCB operated.

Furnace probes are IN-SERVICE positions. (100%)

UCB operation.

13 START furnacepurging.

MRF (A&B) are reset after five minutes.

"MFR TRIP” alarmgoes off.

First cause of trip resets. UCB indicationFSSS - console.

14 LIGHT-UP the boiler with AB elevation oilguns Initially, CDelev. Guns can betaken after drum Pr reaches up to 2 KSC

Drum metal temperaturestarts increasing, gradually.

DAS indications.

Rate of saturation temp rise

to be maintained 110 oC per hour (maximum).

DAS indications.

Drum differential temp to be

maintained below 50oC(maximum).

DAS indications.

15 SWITCH-ON the vapour extractor fan

of the MOT & SGCOIL to auto.

"Green ON lamp comes on"and associated alarm clears

off.

UCB check only.

Aux. oil pump-1 and Jack oilpump no.-1 become on.

UCB operation/check.

OR





KORBA SIMULATOR 148

19 OPEN all Main steamCRH and HRH drainsto BD tank.

Valves DW-153/154/155/156, DW-171/172/173/174 and' DW-164/165/141/142 areOPEN.

UCB indication

20 CLOSE all drum SHand RH air vents after the drum pr. comes

to 2-3 Kg/cm2

andthrottle start-up

vents.

SH-RH and drum air ventsclosed.

Local operationNot simulated.

S-28, S-23, R-15 and R-20are throttled.

UCB operation.

Drum pressure starts rising. UCB/DASindication

21 At a drum pr. of 6Kg/cm2 , OPENintegral bypas valvesto main steam stop

valves, for MS lineHeating, gradually.

Valves MSBP - 1 and MSBP-3 are to be opened 100%. UCB/DASindication.

Valves MSBP-2 and MSBP-4are to be throttled & openedgradually, after MSBP-1/3are fully open.

UCB operationInterlock.

22 ENSURE all prestart checks for chargingHP/LP Bypass system& Rolling turbine areover.

All turbine line drains toflash tank are OPEN and toBD tank are CLOSED.

UCB operation.Refer respectiveoperationinstructions.

Turbine starting-device is at 0% position and UTRs (unit trip relays) are RESET.

UCB operationGTRs must be inreset position andstator water conductivity andflow must be normal

before one can reset UTR

All turbine and generator parameters are NORMAL.

UCB/DAS check.



KORBA SIMULATOR 149

TSE and Frequency influence on EHG are NOT OFF.

UCB check only.

Speeder gear is at 100% andEHC 'NOT FAULTED' and is0%

UCB operation,Electro hydraulicGovernor is at selected.

All HP/LP bypass set pointsare ADJUSTED as per procedures.

Refer to thecorrespondingOperatinginstructions.

Turbine SLC drains is ON. UCB operation.

23 CHARGE MS lines100% and raise boiler firing to raise steamparameters to 40 KSC

of MS Pr. and 300oCof MS temp (mini),

before turbine rolling.CLOSE start-up vent

valves and SH header drain valves.

- Valves S-42, S-64 are beingOPEN 100%.

- UCB operation.

- The bypass valves MSBP1/2/3/4/ are automatically closed.

- Interlocks.

- HP/LP bypass valves start modulating to maintain set steam parameters, to beadjusted upwards.

- UCB operation.

- Steam temperaturesmust be maintainedat minimum valuesas indicated tominimise soakingtimes.

- Steam parameters start rising, depending upon firingrate and HP/LP bypassoperation.

- Refer to the turbinestart-up curves.



KORBA SIMULATOR 150

24 At MS pressure 25-30

Kg/cm2 RAISE

starting device to 70%position and SWITCHON the SLC warm upcontroller.

- HP stop valves open at 42%of starting device position.

- UCB operation.

- IP stop valves open at 56% of starting device position.

- UCB Observation.

- Aux. secondary oil pressure

increases to 3 Kg/cm2

(approx.)

- UCB check only

- Start-up oil pressure becomes zero.

- UCB check only

- Warm-up drains after HP

stop valves start opening for warming up HPCV and closeafter set TSE margins areachieved.

- UCB check only.

Warm-up drain valves must be put on auto & set point to be adjusted by the operator, asrequired.

- HPSV & HPCV meantemperatures increase

gradually to 220oC.

-

25 RAISE speedreference to 600 RPM

and SOAK turbine at 600 RPM untilrequired mean HPshaft temp is attained(speed-up criteria)

- Turbine speed gradually increases to 600 RPM.

- UCB check only

- Gate valve gearing startsclosing at 240 rpm.

- Interlock, if corresponding SLCis on.

- Jack oil pump trips at 540rpm

- Interlock, if corresponding SLCis on.

- HP shaft mean temperaturestarts increasing gradually.

- TSE recorder’sindications, in theUCB.





KORBA SIMULATOR 152

28 SWITCH-ON the loadcontroller and loadgradient controller.CLOSE the field

breaker and ADJUST the excitation to therequired Gen. voltage.

Load gradient and loadcontroller become on.

UCB check only.Load limiter to beset more than loadreference.

Ensure excitation M/A channels controls are at MINIMUM, (HOME) Position

Generator voltage builds upto 15.75 KV.

UCB indications.

29 RAISE starting deviceto 100% and load ref.& load gradient set points to 20 MW & 5MW/MIN respectively.

Aux. Secondary oil pressuregoes up to 4.5 Kg/cm2 (approx.)

UCB indications.

All turbine and generator parameters to be maintained

within their normal,Specified limits.

Local/UCB check.

30 Close the Bus isolator and Generator isolator and switch onthe synchroscope andsynchronise the Gen.

with the Grid.

- Generator breaker getsclosed.

- UCB operation.

- Generator block loading is to be done to avoid tripping of the gen. on "REVERSEpower" protection.

- Refer tosynchronisingProcedures.

- EHC speed controller transfer to load controller,after some time delay.

- Refer to EHCcontrol logics.

31 LINE-UP and CUT-INone PA fan and any one mill and feeder,RAISE load to 40 MW.

- Turbine load increases to 40MW.

- UCB operation.

- Generator voltage to bemaintained at rated value of 15.75 KV.

- Refer to thegenerator Capability curves.



KORBA SIMULATOR 153

32 LINE-UP andCHARGE all L.P.heaters one by one.CLOSE all turbinedrain & close HP/LP

bypass system.

- Condensate temperature toD/A starts increasing..

- DAS points.

- Main steam pressureincreases slightly.

- UCB indications.

32 CUT-IN another pulveriser and RAISEfiring. RAISE load onthe unit.

- Unit loading increasesgradually up to 60 MW.

- UCB indication.Load must follow the MS pressure

- MS pressure keepsIncreasing.

- Main steam pressure

Comes to 70-80 Kg/cm2

- UCB indications.

34 CHANGEOVER fromstation supply to unit aux. transformers(U.A.T.s), andCHARGE unit aux.Steam header frommain steam lines.CHARGE D/A extraction from the IPturbine.

- Unit bus voltages to bemaintained at 6.6 KV withtap changers.

- Refer to the buschangeover procedures.

- Aux. steam pressure to bemaintained at 14-15 Kg/cm2 - Refer to theoperating

Instructions.

- D/A pressure modulates with the unit load.

- Aux. Steam header can be charged only after MS pr is 50

Kg/cm2 or more.Interlock.

35 START the second set of ID, FD, PA fans &BFP and START the

third pulveriser feeder and RAISE load to150 MW. CHARGEhigh-pressure heatersone by one.

- MS pressure to be

maintained at 148 Kg/cm2

after 100 MW.

- UCB operation.

- Unit load increases up to150 MW.

- UCB check only.



KORBA SIMULATOR 154

- Feed water temperature risesup gradually.

- DAS points.

Unit heat rate improvesgradually.

- DAS point.

36 CUT-IN 4th pulveriser

and raise load to200MW

- Unit load increases up to

200 MW.

- UCB operation.

- MS/HRH steam temperature

to be maintained at 535oC.

- UCB operation.

37 TRANSFER all ID, FD,PA fans controls andBFP scoop controller to auto.

- ID fan vanes transfer to auto& maintain set furnace

vacuum.

- UCB operation.Furnace draft of -5to –10 mm wcl is to

be maintained

- FD fan blades modulate tomaintain Oxygen in fluegases.

- Boiler master controller out put generates oxygenset point.

- PA fan vanes transfer to auto& maintain set PA hdr.Pressure.

PA header pressureof 750 mm wcl is to

be maintained.

- BFP Master maintains theset feed water DP across thefeed regulating station.

- Feed regulatingstation DP is to bemaintained. at 5-8

Kg/cm2

38 ENSURE the mill PA flow and temp controlon auto.

- Auto lamp of both thecontroller is ON.

- Both the controller must be in automode before feedersare put in auto.

39 ADJUST raw coalfeeders' biasing to50% and the FuelMaster Controller’soutput, as per requirement.

- The feeder speed controller'serror deviation comes to 0%(biasing may be adjusted toget dev. 0% for a given fuelmaster output).

- UCB check only.

40 ADJUST throttlepressure set point equal to the mainsteam pressure &SET boiler master'soutput as required.

- Error deviation on boiler master comes to 0%

- Before puttingcontrol on autocorresponding error deviation must bezero to avoidhunting.



KORBA SIMULATOR 155

- Errors deviation on fuelmaster comes to 0%.

41 RELEASE all mill,feeders and fuelmaster controller toauto.

- Boiler firing can be adjustedfrom Boiler Master,manually.

- UCB operation.

42 ADJUST Unit Master output equal to the

T/ G load and set max/min. load limitsand load rate on CMCconsole. RELEASEBoiler master controller to auto andunit control to CMC.

- Boiler Master controls the boiler firing rate, dependingon the unit load demand andthrottle pressure set point.

- Refer to the CMClogics.

- Unit Master on automodulates according to theload demand signal from theload dispatch centre.

- Before putting Unit Master on auto,unit master’soutput to be madeequal to the loaddemand signal from

ALDS.



KORBA SIMULATOR 156

UNIT HOT START-UP



KORBA SIMULATOR 157



KORBA SIMULATOR 158

UNIT HOT START-UP PROCEDURE


1 CHECK the

conditions existingimmediately after the unit tripping.

- Generator/Field breakers

are tripped with thecorresponding alarms.

- UCB annunciation.

- UATs' supply to unit busesis tripped and station supply takes over automatically.

- UCB indications.Inter-lock.

- Generator AVR trips tomanual mode, automatically

with an alarm.

- UCB annunciation.

- All the turbine stop andcontrol valves are closed.

- Refer to Turbinegoverning system.

- Turbine trip oil, aux.secondary oil, and secondary oil pressure become zero

- UCB check only.

- All LP / HP heatersextraction block valves areclosed automatically.

- UCB check only.

- All extraction line NRVs are

closed.

- Refer to turbine

governing system.

- Turbine AOP -1 startsautomatically (if SLC is on).

- Interlock.

- The JOP -1 startsautomatically at 510 rpm. (If SLC is on).

- Interlock.

- Turbine gate valve gearing isopened automatically at 200rpm. (If the SLC is on).

- Interlock. Check locally also.

- HP/LP bypass valves open-up if on auto with proper set points, to limiter set position.

- UCB checks. Refer to the HP/LP

bypass interlocks.

- Condenser vacuum breaker valve may open if tripping is

- Interlock. Refer tothe tripping logic





KORBA SIMULATOR 160

airflow.

- Furnace airflow is to bemaintained between 30% to40%.

- UCB indication

- Burners to be brought tohorizontal position, quickly.

- UCB operation

4 ENSURE all purgepermissive areavailable and dofurnace purging for 5 minutes.

- Boiler MFR (A&B) gets reset after a time delay of 5minutes.

- UCB operation.

- The first cause of unit tripping gets reset along withMFR. reset.

- Indication on FSSSconsole.

5 ENSURE Deaerator Pressure ismaintained at 3.5

Kg/cm2 and aux.steam pressure at

14 Kg/cm2

- D/A pressure controller must be on auto andpressure set point to be at 3-

4 Kg/cm2.

- UCB check only.

ESTABLISHcondenser vacuumif it hasdeteriorated on

protection.

- If MS pressure falls below 70

Kg/cm2 aux steam header may be charged other units.

- Isolating valve of unit PRDS areclosed at MS pr. of 50 ata.

- Cond. vacuum must be more

than 0.8 Kg/cm2 beforecharging HP/LP bypasssystem.

- UCB operation.

6 CLOSE HP/LP bypass system toavoid drop in steampressure

- Main steam pressure is to bemaintained below 100

Kg/cm2, preferably for hot start-up.

- UCB operation.

7 RESET generator trip relay and unit trip relays andturbine.

- Starting device is brought to0% position

- UCB operation for turbine resetting.

- Turnine gets reset. - UCB indication

8 LIGHT UP the - Maximum and minimum - Refer to the turbine



KORBA SIMULATOR 161

boiler with theupper elevationguns and a mill if required to hold theMS/HRH temp.CHARGE HP/LP

bypass.

steam temp required for hot rolling might be determinedfrom HPCV and HPS midmetal temperatures.

start-up curves XI - X7. Roughly steamtemperature >(HPCV temp.+ 50 O C )

- HRH steam temp tend todrop with the charging of HP/LP bypass systems. (Min

Required is 480oC).

9 Roll the turbine to600 rpm and SOAK for 5 minutes.

- Gate valve gearing & JOPcut out of service at 240 and540 rpm respectively.

- Interlocks.

10 RISE speed to 3000

rpm andSYNCHRONISE asper procedures.

- Load gradient can be raised

above 10 MW/min. for loading, however thegenerator loadingrecommendations must beadhered to.

- UCB operation.



KORBA SIMULATOR 162

AUTOMATIC TURBINE RUN-UP SYSTEM

(ATRS)



KORBA SIMULATOR 163







KORBA SIMULATOR 166

MODE OF OPERATION

Each functional group is divided into logical steps arranged in a proper sequence.Prior to the commencement of any step, it is necessary that certain conditionsregarding status of plant get fulfilled and the relevant Parameters acquire the desired

value. All these pre-conditions are meticulously planned for each step and demandedfrom the system as 'Enabling Criteria' for next step.

ATRS - STRUCTURE AND GENERAL FEATURES

Automatic Turbine Run-up System is essentially organized in two sub-group controlsnamely Turbine System (SGC Turbine) and Oil System (SGC Oil). These groups inconjunction with wall stress analyser and electro-hydraulic governing systemaccomplish the various functions. A sub-group control essentially executes a set of steps in a proper sequence. Sub-group control at times envisages a sub-loop controlthat essentially executes commands based on the availability of 'Enabling Criteria'.

Sub-group control for the turbine run up acts directly on:

• Sub-loop controls (SLC) for the drains.

• Electro-hydraulic Governing System.

• Auto Synchronizer



KORBA SIMULATOR 167

Sub-group control for the oil directly actuates:

• SLC for the DC lube oil pump.

• SLC for lub oil System.

• SLC for turning gear operation and

• Interface devices for selected few pumps.

ATRS OPERATION CONSOLE

According to the pre-determined sequence, SGC & SLC ensure various requirementsof control oil, lube oil, oil for hydraulic turning etc. under run-up, shutdown and tripconditions.

The sub-loop controllers get switched on and off according to the pre-definedsequence logic built in the SGC. However, the actual execution of command of a SLCtakes place only if the enabling criteria for the fulfilment of a particular command arecompletely satisfied. It is possible to intervene manually at any level namely interfacesub-loop control or sub-group control.

The enabling criteria at the various level of hierarchy are of different nature. For instance, the enabling criteria at the ‘Interface Level’ envisaged are based on theequipment protection point of view rather than the process consideration.

It is also possible to manually start the plant up to any level/status then ask thesub-group control to perform the remaining functions. To facilitate such modes of operations, the sequential logic has been development in such a manner the sub-group control shall quickly skip to the proceeding step done manually andaccomplish the steps automatically in the desired logical manner. The SGC Turbinelogics for (ATRS) incorporating various steps and criteria required to execute eachsteps are in the following sections.



KORBA SIMULATOR 168



KORBA SIMULATOR 169



KORBA SIMULATOR 170

SGC OIL SYSTEM LOGICS





KORBA SIMULATOR 172



KORBA SIMULATOR 173



KORBA SIMULATOR 174



KORBA SIMULATOR 175



KORBA SIMULATOR 176

SUB LOOP CONTROL - AUXILIARY OIL PUMP - 1

1. When SLC AOP - 1 is ON AND AOP - 2 trips OR Oil pressure < 4.8 Kg/cm2,

command is given to switch on Aux. Oil Pump - 1

SUB LOOP CONTROL - AUXILIARY OIL PUMP - 2

1. When SLC AOP - 2 is ON AND AOP - 1 trip OR Oil pressure < 4.5 Kg/cm2,

command is given to switch on Aux. oil Pump - 2

SUB LOOP CONTROL - DC EMERGENCY OIL PUMP

1. When SLC emergency oil pump is ON AND if lube oil pressure < 1.1

Kg/cm2

command is given to switch on EOP.

SUB LOOP CONTROL - JACKING OIL PUMP - 1

1. When SLC JOP - 1 is ON AND if turbine speed < 510 RPM, command is

given to switch on JOP -1,

2. If turbine speed > 540 RPM, command is given to switch off JOP - 1

SUB LOOP CONTROL - JACKING OIL PUMP - 2

With SLC JOP - 2 is ON, if JOP - 1 trips OR if jack oil pressure < 120 Kg/cm2, with

turbine speed < 510 rpm with a delay of 5 seconds, command is given

1. To switch ON JOP 2

2. To switch OFF JOP 1

3. To switch OFF SLC JOP-1

SUB LOOP CONTROL - TURNING GEAR

1. With SLC turning gear is ON AND if turbine speed < 200 RPM, command is

given to open the gate valve gearing.

2. If turbine speed is greater than 240 RPM, Command is given to close gate

valve gearing





KORBA SIMULATOR 178

STEP - 4

1. SWITCH SLC TURNING GEAR ON

2. MONITORING TIME 60 SEC

CRITERIA FOR STEP - 5

1. GATE VALVE GEARING OPEN OR TURBINE SPEED > 250 RPM

2. SLC TURNING GEAR ON

STEP-5

1. SLC AOP-1: ON

2. SLC AOP-2: ON

3. SLC EOP: ON

4. SLC JOP-1: ON

5. SLC JOP-2: ON



1. SLC AOP-1: ON

2. SLC AOP-2: ON

3. SLC EOP: ON

4. SLC JOP-1: ON

5. SLC JOP-2: ON

6. TURBINE SPEED > 15 RPM

STEP - 6

1. NO COMMAND ISSUED.

2. MONITORING TIME BLOCKED



STEP - 7

1.

NO COMMAND ISSUED2. MONITORING TIME 60 SEC



KORBA SIMULATOR 179


1. JACKING OIL PUMP-1: OFF

2. JACKING OIL PUMP-2 : OFF

3. GATE VALVE GEARING CLOSED

STEP - 8 1. NO COMMAND ISSUED




2. PRESSURE-OIL PRESSURE > 7 KG/CM2

STEP - 9

1. SWITCH AUXILIARY OIL PUMP (1) OFF

2. SWITCH AUXILIARY OIL PUMP (2) OFF

3. MONITORING TIME 0.5 SEC


1. WAITING TIME 0.5 SEC

STEP - 10

1. NO COMMAND ISSUED



1. WAITING TIME 10 SLC OR GEN LOAD > 10%

2. AUXILIARY OIL PUMP - 1 OFF

3. AUXILIARY OIL PUMP - 2 OFF

4. EMERGENCY OIL PUMP OFF

STEP - 11





KORBA SIMULATOR 180

SUB LOOP CONTROL : OIL SYSTEM

SHUTDOWN PROGRAMME

CRITERIA FOR STEP: 51

1. TEMP HP CASING TOP < 100 OC

2. TEMP HP CASING BOTTOM < 100 OC

STEP: 51

1. SLC TURNING GEAR: OFF

2. GATE VLV GEARING: CLOSE



1. SLC TURNING GEAR: OFF

2. GATE VLV GEARING: CLOSED

STEP: 52


2. MONITORING TIME: 100 SEC


1. TURBINE SPEED < 10 RPM

STEP: 53




1. WAITING TIME 1000 SEC

STEP: 54

1. SLC JOP 1 OFF

2. SLC JOP 2 OFF

3. SLC OIL TEMP CONTROL OFF

4. JOP 1 OFF

5. MONITORING 4 SEC



KORBA SIMULATOR 181


1. SLC JOP 1 OFF

2. SLC JOP 2 OFF

3. SLC OIL TEMPR CONTROL OFF

4. JOP 1 OFF

5. JOP 2 OFF

STEP: 55

1. SLC AOP 1 OFF

2. SLC AOP 2 OFF

3. SLC EOP OFF

4. AOP 1 OFF

5. AOP 2 OFF

6.

OIL TEMP CNTRL VLV CLOSED7. MONITORING 30 SEC


1. SLC AOP 1 OFF

2. SLC AOP 2 OFF

3. SLC EOP OFF

4. AOP 1 OFF

5. AOP 2 OFF

6. OIL TEMP CONTRLR OFF

7. EOP OFF

STEP: 56





KORBA SIMULATOR 182

SGC TURBINE SYSTEM LOGICS



KORBA SIMULATOR 183



KORBA SIMULATOR 184



KORBA SIMULATOR 185



KORBA SIMULATOR 186



KORBA SIMULATOR 187



KORBA SIMULATOR 188



KORBA SIMULATOR 189



KORBA SIMULATOR 190



KORBA SIMULATOR 191



KORBA SIMULATOR 192



KORBA SIMULATOR 193





KORBA SIMULATOR 195



KORBA SIMULATOR 196





KORBA SIMULATOR 198


1. TRIP FLUID PRESSURE > 5 Kg/cm2


3. CONDENSATE PUMP DISCHARGE PRESSURE: OK

4. SLC DRAINS NO FAULT 5. DT HP CASING (TOP-BOT) > MINUS 40 K

6. DT HP CASING (TOP-BOT) > PLUS 40 K

7. DT IP CASING FR (TOP-BOT) > PLUS 40 K

8. DT IP CASING FR (TOP-BOT) > MINUS 40 K

9. DT IP CASING REAR (TOP-BOT) > PLUS 40 K

10. DT IP CASING REAR (TOP-BOT) > MINUS 40 K

STEP: 3

1. CLOSE DRAIN BEFORE HP CTRL VALVE -12. CLOSE DRAIN BEFORE HP CTRL VALVE -2

3. SWITCH SLC WARM UP CONTROLLER: OFF

4. MONITORING TIME: 60 SEC


1. DRAIN BEFORE HP CTRL VLV-1: CLOSED


3. SLC WARM-UP CONTROLLER: OFF

STEP: 4




1. BOILER FIRE ON

2. STEAM BEFORE HPBP-1 > 30 K SUPERHEAT

3. STEAM BEFORE HPBP-2 > 30 K SUPERHEAT

4. STEAM BEFORE LPBP-1 > 30 K SUPERHEAT

5. STEAM BEFORE LPBP-2 > 30 K SUPERHEAT

6. DT (HPBP-1 -CNTRL VALVE MID) > X 1.1

7. DT (HPBP-2 -CNTRL VALVE MID) > X 1.2



KORBA SIMULATOR 199

8. TOTAL BOILER STEAM FLOW > 15%

9. DT (WET STEAM- CNTRL VALVE -1.) > X 2.1

10. DT (WET STEAM- CNTRL VALVE -2.) > X 2.2

11. DT (HPBP-1 -CNTRL VALVE MID) < X 3

12. DRN BEFORE HP ESV-1 NOT CLOSED

13. DRN BEFORE HP ESV-2 NOT CLOSED

14. DRN BEFORE INTCPT ESV-1 NOT CLOSED

15. DRN BEFORE INTCPT ESV-2 NOT CLOSED

16. OIL TEMPERATURE AFTER COOLER > 35 0 C

STEP: 5

1. STARTING DEVICE RAISE

2.

MONITORING TIME 30 SEC


1. ANY HP ESV OPEN

STEP: 6




1. HP ESV1 OPEN

2. HP ESV2 OPEN

STEP-7




1. TOTAL STEAM FLOW >15%

2. STEAM BEFORE HP BYP 1 > 30 K SUPERHEAT

3. STEAM BEFORE HP BYP 2 > 30 K SUPERHEAT

4. STEAM BEFORE LP BYP 1 > 30 K SUPERHEAT

5. STEAM BEFORE LP BYP 2 > 30 K SUPERHEAT

6. BOILER FIRE ON



KORBA SIMULATOR 200

7. DT (HP BYP1-CTRL VLV) > X 1.2

8. DT (HP BYP 2-CTRL VLV) > X 1.1

9. CONDENSER PRESSR < 0.5 kg/cm2

STEP: 8

1. SLC WARM UP CTRL ON



1. SLC WARM UP CTRL ON

STEP: 9


2. MON TIME 20 SEC


1. STARTING DEVICE > 56%

2. INTCPT ESV - 1 OPEN

3. INTCPT ESV - 2 OPEN

STEP: 10




1. DRAINS NO FAULT

2. SPEEDER GEAR 100%

3. GLAND STEAM PESSR CONTRLR ON

4. SLC OIL TEMPR CTRL ON

5. ANY OIL VAPOUR EXTRACTOR ON

6. HYDROGEN PURITY > 97%

7.

GEN GAS PRESSR > 3.4 kg/cm2

8. GEN SEAL OIL / GAS DP > 0.9 kg/cm2

9. GEN SEAL OIL TURB SIDE PRESSURE > 3.8 kg/cm2

10. GEN SEAL OIL EXCITER SIDE PRESSURE > 3.8 kg/cm2

11. LEVEL IN PRE-CHAMBER – 1&2 < MAX



KORBA SIMULATOR 201

12. GEN CW FLOW > 21 M3/Hr

13. GEN STATOR CW PRESSURE > 2.4 kg/cm2

14. STATOR CW INLET TEMPERATURE < 44 0 C

15. HYDROGEN COOLER CW PRESSURE > 2.5 kg/cm2

16. LIQUID IN GEN NOT PRESENT

17. GEN STATOR WATER CONDUCTIVITY < 5 MHO/CM

STEP: 11




1. ALL CRITERIA FOR STEP 11

2.

STEAM BEFORE HP ESV 1 SUP HEAT > X4.13. STEAM BEFORE HP ESV 2 SUP HEAT > X4.2

4. DT (HP ESV 1-HP CASING) > X5.1

5. DT (HP ESV 2-HP SHAFT) > X5.2


7. DT (LP BYP 1-IP CASING) > 30 K

8. DT (LP BYP 2-IP CASING) > 30 K

9. STEAM BEFORE LP BYP 1 > 480 0 C

10. STEAM BEFORE LP BYP 2 > 480 0 C

11. DRAIN BEFORE HP CONTROL VLV-1 NOT CLOSED

12. DRAIN BEFORE HP CONTROL VLV-2 NOT CLOSED

13. POWER SET POINT > 10 %

14. CONDENSER PRESSURE < 0.2 Kg/cm2

15. REL EXP CAS 1 FRONT < +8 mm

16. REL EXP CAS 1 REAR > -2 mm


18. REL EXP CAS REAR > -2 mm


20. REL EXP CAS 3 REAR > -2 mm



KORBA SIMULATOR 202

STEP: 12

1. TURBINE SPEED SET POINT RAISE



1. SPEED SET POINT > 650 RPM

STEP: 13





STEP: 141. TSE TEST PROGRAMME BLOCK

2. WAIT TIME 180 SEC


1. WAITING TIME 180 SEC

2. DT (HP BYP-HP SHAFT TEMP) < X6

3. TURBINE STRESS MARGIN > 30 K

4.

BRG VIBRN CAS1 FRONT < 35 MICRON5. BRG VIBRN CAS1 REAR < 35 MICRON

6. BRG VIBRN CAS2 FRONT < 35 MICRON

7. BRG VIBRN CAS2 REAR < 35 MICRON

8. GEN BRG VIBRN FRONT < 50 MICRON

9. BRG VIBRN GEN FRONT < 50 MICRON

10. BRG VIBRN GEN REAR < 50 MICRON

11. BRG VIBRN GEN REAR < 50 MICRON

12. BRG VIBRN HP SHAFT FRONT < MAX

13. BRG VIBRN HP SHAFT REAR < MAX

14. BRG VIBRN IP SHAFT < MAX

15. BRG VIBRN LP SHAFT < MAX



KORBA SIMULATOR 203

16. RAD BRG1 CAS FRONT LH TOP TEMP < MAX

17. RAD BRG1 CAS FRONT RH TOP TEMP < MAX

18. RAD BRG1 CAS FRONT LH BOT TEMP < MAX

19. RAD BRG1 CAS FRONT RH BOT TEMP < MAX

20. RAD BRG1CAS REAR LH TOP TEMP < MAX

21. RAD BRG 1CAS REAR RH TOP TEMP < MAX

22. RAD BRG1 CAS REAR LH TOP TEMP < MAX

23. RAD BRG1 CAS REAR RH BOTTOM TEMP < MAX

24. AX BRG1 CAS R/F LH TEMP < MAX

25. AX BRG1 CAS R/F RH TEMP < MAX

26. AX BRG1 CAS R/R LH TEMP < MAX

27. AX BRG1 CAS R/R RH TEMP < MAX

28. RAD BRG2 CAS REAR TEMP < MAX

29. RAD BRG2 CAS REAR R/R RHB TEMP < MAX

30. RAD BRG2 CAS REAR R/F RHB TMP < MAX

31. RAD BRG3 CAS REAR R/R RHB TEMP < MAX

32. REL EXP < MAX

33. GEN FRONT BRG TEMP < 90 0 C

34. GEN REAR BRG TEMP < 90 0 C

STEP: 15

1. SLC WARM UP CONTROLLER OFF



1. SLC WARM UP CONTROLLER OFF

STEP: 16

1. TURB SPEED SET POINT: RAISE

2. DRN BEF HP CONTROLL VLV-1: CLOSE

3. DRN BEF HP CONTROLL VLV-2: CLOSE

4. MON TIME 200 SEC



KORBA SIMULATOR 204


1. SPEED SET POINT > 3036 RPM.

STEP: 17





2. BEAR VIB CAS GEN < MAX

3. SHAFT VIB < MAX

4. BEARING TEMP. < MAX

STEP: 18

1. DRAIN BEFORE HP CTRL VLV-1: CLOSE2. DRAIN BEFORE HP CTRL VLV-2: CLOSE





STEP: 19




1. BOTH AOPS : OFF

2. DT (LP BYPASS 1 – IP SHAFT) < X7

3. GEN CONDITIONS FULFILLED

4. FIELD FLASH SUPPLY ON

5. AVR CONTROL SUPPLY ON

6. AVR PROT. SUPPLY ON

STEP: 20

1. GEN FIELD BREAKER ON

2. WAIT TIME 15 SEC



KORBA SIMULATOR 205


1. WAIT TIME 15 SEC

2. GEN FIELD BREAKER ON

3. GEN VOLTAGE >15 KV

STEP: 211. SYNCHRONISER: ON



1. GEN BREAKER ON

STEP: 22




1. GEN LOAD > 10%

STEP: 23


2. WAIT & MONITORING TIME 2 SEC


1. WAIT TIME 2 SEC

STEP: 24




1. STARTING DEVICE 100%

STEP: 25





KORBA SIMULATOR 206

SUB LOOP CONTROL : TURBINE SYSTEM

SHUTDOWN PROGRAMME

STEP: 51

1. SLC DRAINS ON



1. SLC DRAIN ON

STEP: 52

1. POWER SET POINT LOWER

2. MONITORING TIME BLOCK


1. SPEED CONTROLLER IN ACTION

2. POWER SET POINT 0% OR GEN BRKR OFF

STEP: 53

1. TURBINE SPEED SET POINT LOWER



1. STEP-53 COMPLETED WITH TIME DELAY 100 SEC

OR GENERATOR BREAKER OFF

STEP: 54

1. ELEC TURB TRIP - CHANNEL 1

2. ELEC TURB TRIP - CHANNEL 2

3. SYNCHRONISER OFF



1. SYNCHRONISER OFF

2. TRIP FLUID PRESSR < 5 kg/cm2

3. GEN FIELD BRKR OFF

4. ALL ESV S CLOSED



KORBA SIMULATOR 207

STEP: 55

1. STARTING DEVICE LOWER

2. DRAIN BEFORE HP CONTROL VLV-1 OPEN


4.

SLC WARM-UP CONTROL OFF 5. MONITORING TIME 120 SEC




3. STARTING DEVICE 0%

4. DRAINS NO FAULT

5. SLC WARM-UP CONTROLLER OFF

STEP: 56





KORBA SIMULATOR 208

UNIT PLANNED SHUTDOWN



KORBA SIMULATOR 209



KORBA SIMULATOR 210

BOILER SIDE SHUTDOWN OPERATIONS

ACTION OBSERVATION& REMARKS

1.

ENSURE all oil guns Available.2. REDUCE mills firing Maintain furnace Draught.

3. WATCH and ensure Steamtemperatures to be brought down by Attemperation, for thepurpose of force cooling

Gradual reduction in steamparameters.

4. Soot-blow boiler at160 MW. MAINTAIN load at 160 MW untilsoot blowing is over.

160 MW

5. BRING DOWN Deaerator

set point to 3.5 Kg/cm2

D/A pressure must not fall below

3.5 Kg/cm2

to prevent cavitation.

6. REDUCE load to 130 MW. CUT-OUT one top pulveriser

If needed, take adequate oilsupport.

7. REDUCE firing gradually.

8. CUTOUT one more mill. Monitor ignition energy considerations.

120 MW

9. CLOSE ES-7. Ensure AS-64 opens up at CRHpressure less than 9 Kg/cm

2.

10. STOP one P.A. Fan.

11. REDUCE load to 80 MW.

12. STOP one set of ID/FD Fan.

CHECK APH tripping interlock.

13. CHECK APH gates isloated from

gas/air side.

80 MW

14. CHECK changeover dampers before ID Fan have opened.

15. STOP one B.F.P

16. REDUCE firing of the remainingtwo mills.

Boiler airflow may be reduced to

maintain only the required amount



KORBA SIMULATOR 211

of excess air, to ensure optimum

efficiency.

17. STOP mills and the second P.A.

Fan.

18. Reduce steam temperatures by attemperation and cutting out oil elevation.

TURBINE STOPPED

19. PURGE boiler for 5-minuteskeeping all auxiliary /secondary / fuel dampers open.

Any of the boiler protections can

be tested after the turbine is

tripped.

20. STOP remaining ID/FDFans,

ignitor fans.

21. ENSURE all inlet / outlet dampers, guide/regulating vane,mill cold air dampers anddischarge valves and all wind-

box dampers are OPEN.

22. FILL boiler to maximum drumlevel.

23. CLOSE SH stop valves.

24. ISOLATE feed control station.

25. STOP B.F.P.

26. At 2 Kg/cm2

drum pressureOPEN drumvents/SH and RH

vents and SH drains.

27. At flue gas temperature of

1400C, STOP APH and scanner

fans.



KORBA SIMULATOR 212

TURBINE SIDE SHUTDOWN OPERATIONS

ACTION OBSERVATION & REMARKS

1.

REDUCE load reference to 160MW. Monitor TSE margins and turbine bearing vibrations/temperaturesetc.

Steam temperature / pressurestart dropping.

SET load gradient to 5 MW/min.

210 MW

2. ENSURE HP/LP bypassoperation.

Keep the HP/LP Bypass control on AUTO.

3. REDUCE load reference to 120MW

Load must be reduced only if steam pressure drops.

160 MW

4. ENSURE AS-62 is open.(CRH steam to Deaerator)

5. CUT OUT HP heaters

120 MW

6. CARRY OUT automatic turbinetest. Refer to the chapter on ATT.

7. SET load reference to50 MW.

80 MW

8. ENSURE changeover of glandseal steam controller from leak off to gland steam pressurecontroller supply.

9. ENSURE changeover fromUAT to station supply.

50 MW

10. Ensure steam temperature isreducing.

Maintain TSE lower margin andcasing Differential temperature.



KORBA SIMULATOR 213

11. REDUCE load reference to 30MW.

12. CUT OUT LPHs.

13. SWITCH OFF load controller. 'Speed Controller Acting' indicationcomes on.

30 MW

14. TRANSFER operation to speedcontroller.

15. REDUCE speed reference to lessthan actual.

(CHECK 'Reverse Power Protection').

Turbine Trip

ENSURE turbine ESV's and IV'sclosed.

Testing of any of generator protections can be done.

Trip fluid pressure zero.

CRH NRVs are closed.

Extraction NRVs and block valves closed.

Generator/field breaker opened.

Control Oil Pre. 4.8 Kg/cm2.

16. AOP-1 starts on auto.(Approx. at 2950 rpm).

510 RPM

17. JOP-1 starts on AUTO

210 RPM

18. Gate valve gearing opens up.

19. LOWER speed reference to "0".

20. LOWER starting device to 0%.



KORBA SIMULATOR 214

21. ENSURE opening of thefollowing drains:

HP casing drain.

Drain after CRH NRV's

Drain before/after IV's. NRV's.Drain before extraction NRV's

Seal steam header drain.

Drain before ESV's.

22. STOP turbine barring. Barring can be stopped after casing/shaft temp. have reduced

below 150oC23. SHUTDOWN all condensate

pumps.

At Casing temp. of 100 O C

24. SHOUTDOWN oil system

25. SWITCH-OFF all SLCs.

26. SHUT-DOWN JOP only when nomovement of journal in bearingis expected due to rotor cooling.





KORBA SIMULATOR 216

EMERGENCY HANDLING



KORBA SIMULATOR 217



KORBA SIMULATOR 218

CONDENSATE WATER SYSTEM

1. HOTWELL LEVEL LOW.

FAULT CONSEQUENCE ACTION

''Hotwell level low''alarm comes on at 400mm wcl of Hot well level.

Loss of NPSH for the pump. Open Hotwell make-up valves MC-49/48.

CEP will trip at 250 mm wclof hot well level.

Ensure cycle makeupfrom surge tank MC-54is open.

Excessive flow to D/A from Hotwell

LP bypass valves close/tripon condensate discharge pr.low protection.

CST level is adequate.

Some leakage insteam/water (feed)circuit (water-wallsuper heater,Economiser etc.).

If the condensate pumpstrip. Cond. vacuum may start dropping as the mainejector performancedeteriorates; Cycleefficiency comes down withfalling vacuum.

In case two pumps arerunning, stop onepump immediately,after closing Hotwelllevel control valvessufficiently.

ACS Xmitter failure/fault.

Reduce flow to D/A or surge tank. Close MC-41 or/ and MC-27.

DM make-up may be

inadequate.DM make up pumpmay have tripped.

Ensure there is no

leakage in condensatesystem and CBD, EBD& IBD are closed.

2. HOTWELL LEVEL HIGH.


Hotwell level highannunciation comes at 600 mm wcl.

Vacuum will start deteriorating if level goeshigher than 1600 mm wcl.

Close DM make up valves to Hotwell.

MC-27 may be closed.(No flow to Deaerator or surge tank).

Deaerator level will start coming down, if the flow from Hotwell has beenstopped.

Close cycle make-up if it is open.

Too much DM make-upto Hotwell.

Running BFPs can trip on''D/A level very low''.

CHECK & ADJUST set point less than 600mm wcl.



KORBA SIMULATOR 219

Hotwell set point toohigh.

Boiler can trip on ''loss of all BFPs'' protection

CHECK if MC-27 is not open sufficiently,OPEN and take some

water to D/A or surgetank. If the need be,open The electrical

bypass V/Vs of MC-27& MC-41 (MC-28 andMC 42 respectively.

ACS transmitter fault.

Unit will trip due to boiler tripping.

Condenser tubeleakage.

Cond. water conductivity will increase and pH valuemay drop. This will causethe boiler- water chemistry to deteriorate beyondpermissible limits.

Condensate pumpsmay have tripped

If the need be, (2ndpump comes intoservice automatically if discharge pressurecomes below 17 KSC.

CONDENSER COOLING WATER & VACUUM SYSTEM

1. LOSS OF CIRCULATING WATER PUMP


Operation of motor protection. Condenser Vacuum may deteriorate due toinadequate water flow.

Immediately reduce theload on the unit to50%.

Loss of lub water pumpof CW pumps.

Turbine may trip on''Vacuum low'' protection.

(0.72 Kg/cm2).

Immediately throttlecondenser outlet valvesof both condensers tomaintain the CW header pressure.

Pump mechanicalfailure.

Condenser exhaust hoodtemp may increase with theincrease in back pressure

and cause LPT diff. exp. (+)to increase.

Ensure LP water injection valve opens tomaintain ex. Hood

temp below 80 deg. C

''CW pump trip'' alarmcomes on DAS.

Due to reduced header pressure (CW), the other running units may experience low vacuum.

Cut in additionalejectors, if needed, tomaintain vacuum at

0.92 Kg/cm2(rated).



KORBA SIMULATOR 220

Circulating water header pressure dropsslightly.

Boiler firing may increaseon CMC mode due to low cycle efficiency.

CW flow through thecondensers Decreases.

Start the standby CW pump, immediately, if it's available.

3. CONDENSER VACUUM IS DETERIORATING, GRADUALLY.


Air ingress in thecondenser hasincreased.

Turbine vacuum startsdeteriorating and LPT exhaust temp rises.

Immediately decreaseunit load low enoughto sustain vacuum.

Cond. surge tank levelmay be very low.

Turbine control valves openmore to meet load demandand boiler firing increaseson CMC.

Take additional air ejectors in service.

Hotwell level may be very high.

Turbine may trip on''Vacuum low'' protectionand the boiler may trip onR/H protection.

Ensure hot-well CST level and gland sealsteam pr. are OK andcond pumps are on.

Also ensure ejector steam pr. is adequate.

Cond. pump may havetripped or MC-27/28 isclosed & MC-33/34 isnot open.

Low vacuum causes thecycle efficiency to decrease.

Ensure CW header pr.and condenser circulating water flowsare normal.

Cond. CW pumps may have tripped.

Due to high cond back pressures, the diaphragmmay get ruptured.

If any condenser isfound choked carry out cond. Backwashing

Ejector steam pressureis low.

On hydraulic governingmode unit output willreduce due to Low cond.

vacuums.

Ensure all cond. CW pumps, cooling tower pumps and fans arerunning normally.

Cond. CW temp may behigher (CT pp. may not

be in service).

Condenser tubes may be fouled up or evenchoked.



KORBA SIMULATOR 221

3 . CONDENSER WATER BOX DP HIGH (ALARM)


Condenser tubes may be choked or badly

fouled-up.

Condenser choking may result in bad heat transfer and reduce CW condenser

flow

Find out thecondenser, which ischoked by seeing CW

flow (low) temp. (High)or diff. from DAS or locally.

Due to inadequatechlorination, some

biological growth hastaken place at thecond. inlet.

Consequently condenser vacuum may fall, causinglow thermal efficiency.

Reduce load to 80 MW (approximately)

Condenser CW flow decreases and its

differential tempincreases. (DASindication).

Unit may trip on low condenser vacuum and

cause low plant loadfactors/availability

Cut-in one more mainejector and starting

ejector, if required.

Condenser vacuummay start falling (alarm

at 0.8 Kg/cm2.)

Charge priming ejector and close CA-1 or CA-2air valve of the cond. to

be back-washed.

Reverse the direction of 4-way butterfly valve of

the condenser.

OPEN CA-1/2 that wasclosed and close theother one and

backwash the 2ndcondenser.

BOILER FEED PUMP

1. BFP RE-CIRCULATION VALVE FAILS CLOSED.


BFP dischargepressure may increase.

Increased differentialpressure across the FW regulating valve causes theBFP speed to be reduced if it is on auto.

Adjust the re-circulation of the BFPsuch that BFP flow does not fall less than150T/Hr.



KORBA SIMULATOR 222

'BFP'' suction flow low alarm may come at 125

T/Hr.

Insufficient feed flow through the BFP may causechurning and may lead toseizure of the pumpultimately due to prolongedoperation of BFP withinsufficient feed flow.

If re-circulation cannot be maintained takeanother BFP in serviceand stop the one withthe problem.

BFP bearingtemperature may increase due tocavitations or churning.

2. BFP LOSS OF LUB. OIL PRESSURE


Lub oil pressure low alarm comes.

Any feed pump; trip pingout of service may causeserious drum leveldisturbances.

Ensure immediately that standby BFP isavailable.

Lub oil pres sure Lo-Loalarm comes

Boiler may trip on drumlevel protection.

Maintain levelotherwise, unit may trip on 'Low' drum levelprotection.

BFP trips & brings onalarm of BFP trip.

Bearing starvation anddamage may take place.

Filters may be chockedup

Drum level will dropmomentarily and Deaerator may increase slightly

Unit may run back onCMC mode. Avoid any possible failure by cutting in oil elevation

BFP's lub oil Pressureswitch may havemalfunctioned.

Other running BFP goesfully loaded

("lub. oil pr. adequate"lamp remains on).

The standby BFP gets anauto start command &

comes into service after 5sec. time delay

If the standby BFP hasnot started, then start

it manually.

Instruct local operator to change over the oilfilters (duplex).



KORBA SIMULATOR 223

3. BFP BEARING VIBRATION: HIGH


Lub oil quality bad. BFP may trip at high (7mm/sec.) vibration level.

Unit runs back onCMC if any BFP tripsand the standby pumpdo not come intooperation within 10 sec

Damaged bearing.Mechanical problemsin pump

Boiler may trip if no other BFP is in operation

Cavitation due toair/vapour ingress intoBFP.

Boiler may also trip ondrum level fluctuations(V.HI / V.LO).

Avoid any possibleflame failure due tounloading of the millson CMC runback, Cut-in oil elevation.

Unit may trip or run back

on CMC to its lower loadlimit

Ensure the D/A pr. is

not dropping rapidly after a tripping; andBFP suction pr. isadequate.

4. BFP HYDRAULIC COUPLING OUTLET OIL TEMPERATURE IS GOING HIGH.

FAULT CONSEQUENCE ACTIONBFP may be runningon low scoop tubeposition for a longtime.

At 130oC working oil outlet temperature, the BFP may trip and can cause drumlevelFluctuations.

Instruct local operator to change over workingoil coolers.

BFP working oil cooler may be fouled up.

Unit may run-back on CMCto lower load limit.

Ensure ARCW pumppr. is adequate.

BFP cooling water pr.(ARCW) may be low.

Unit may trip due to loss of all BFPs.

Increase BFP scooptube position.

''BFP brg. metal/oiltemp high''& "BFPhydraulic coupling oiltemp high'' alarms may start flashing.

5. BFP SUCTION PRESSURE IS FALLING LOW.


Deaerator pressure BFP may trip on low Ensure standby BFP is



KORBA SIMULATOR 224

may be falling. suction pressure. (< 6.5

Kg/cm2)

available and comeson, in service.

BFP suction strainer chokes.

Boiler/unit may trip or runback on CMC.

Maintain D/A pressure.

''BFP suction pressurelow'' and ''BFP suctionstrainer clogged''alarms start flashing.

BFP may cavitate and seizeultimately.

Shut-down the BFPfor strainer cleaningand maintenance.

6. BOILER FEED PUMP MASTER SPEED CONTROLLER FAILS HIGH.


BFP speed controllersgo to maximum.

Drum level will start increasing.

Transfer the BFPmaster controller tomanual mode.

F.W. control valvedifferential pres- sureindicator goes to zero.

The high range feed control valve will start closing inresponse of high feed water flow and drum.

Reduce the individualspeed controller’soutput to bring downthe Water flow, if needed.

Feed water flow increases.

BFP may trip on account of high feed flow.

If BFP flow is morethan 430 T/hr. for more than a minute,BFP will tripimmediately reduce thescoop controllers

BFP flow high alarmmay come.

Drum level high alarmcomes if the level reaches125 mm.

Unit trip will occur if levelreaches 225 mm andremains for more than 10secs.

Watch the drum level& ensure it ismaintained normal.



KORBA SIMULATOR 225

REGENERATIVE FEED HEATING SYSTEM

1. EXTRACTION SHUT- OFF VALVE ES-6 TO HP HEATER-6 FAILS CLOSED


Extraction shut- off valve es-6 to hp heater-6 fails closed

FW temperature leavingHPH-6 will be equal to FW temp out of HPH-5.

Give ES-6 an openingcommand.

Spurious electricalfault.

HP control valve positiondecreases slightly onincreasing MW.

If it does not openreduce the boiler firingand RH outlet.

Indication/ Causes: Drum level drops due toshrinkage.

Watch the steamtemperature at SHoutlet and RH outlet

Extraction block valve ES-6 closeindication comes.

Throttle pressure increasesmomentarily and thendrops.

Check the steamtemperature beforeattemperation. If it isincreasing, thenincrease theattemperation slowly tocontrol the mainsteam/ reheat temperature

HPH-6 normal drain valve goes closed as

soon as ES-6 closescompletely.

Firing rate increases if unit is on CMC and slight loss of

efficiency caused by loss of a feed water heater.

Normal drain to HPH-5goes closed.

Drum level drops.

2. LP HEATER-3: TUBE LEAK.


Extraction steam line NRVsto Heater-3 will close down.

Drain the affectedheater and try tocharge the heater

Possible Causes: Extraction line drain valveon turbine panel opens

when NRV is less

If level does not comedown, try to bypass theheater.



KORBA SIMULATOR 226

Tube rupture Condensate flow toDeaerator drops by 100

T/hr.

Check the proper closure of extraction

block valve and NR valves.

LP Heater-3 level highalarm comes.

Deaerator level controller output increases ondecreasing D/A level

Instruct the localoperator to bypass theheater from feed

waterside.LPH-3 alternate drain

valve begins to open.Deaerator level controller output increases ondecreasing Deaerator level.

Maintain the Deaerator level and condensatepump dischargepressure.

LPH-3 normal drain valve closes.

Condensate dischargeheader pr. decreases sincecondensate is re-circulatingthrough LPH-3.

Take Hotwell levelcontrol in manual andreduce its output tomaintain thecondensate pumpdischarge pressure.

LPH-3 level Hi-Hialarm comes in DAS

LP heater extractionsteam block valve ES-3

If condensate dischargeheader pressure drops

below 17.5 Kg/cm2

for 15secs., condensate pump willtrip.

LPH-3 extraction linedrain valve DW-80opens.

Feed water temp. todeaerator will decrease.

3. HP HEATER TUBE LEAK.

FAULT CONSEQUENCE ACTION HPH-6 level high

alarm comes.Extraction steam line NR

valves to Heater-6 will closedown.

Under very high levelHP heaters get

bypassed on waterside

and extraction valvecloses. However, it isadvised not to wait for this action.

HPH-6 alternate drain valve to condenser opens. Red light comeson.

Extraction line drain valveson turbine panel open whenNRV is less than 5% open.



KORBA SIMULATOR 227

Feed water temperatureleaving HPH-6 drops down.

Bypass the heaters by energising the group

bypass valves

HPH-6 level high andhi-hi alarm comes inDAS.

Drum pressure will increasedue to closure of extraction

valve.

Tilt the burner tilts tonegative side toprevent the shootingup of R/Htemperature.

HPH-6 & HPH-5 heater extraction drain valvesES-6 and ES-5 set closed.

Flue gas temperatureleaving furnace willincrease.

Watch the drum level. Take it on manual if necessary

Main steam temperatureleaving furnace willincrease.

NOTE: one canmaintain full load

without HP Heater also

Extraction steam linedrains DW-75 and DW-74 open.

Drum level drops due toshrinkage.

Check the heater levelfrom the local.

HPH-6 normal drain valves HD-37 and HD-51 to HPH-5 anddeaerator closes.

Throttle pressure drops asthe efficiency drops.

4. HPH-6 ALTERNATE DRAIN VALVE FAILS OPEN.


Spurious controlsignal.

When all the condensate hasgot drained out of the FW heater, steam will start

blowing directly through theheater and into thecondenser.

Restore instrument air pressure if possible.

Instrument air failure.

Reset and put onRemote, if needed; thepneumatic control valves,after air supply isrestored.

HPH-6 alternatedrain valve HD- 43open indicationcomes HPH-6normal drain toHPH-5 closes.

If required, get thealternate drain closedmanually.

If there is water in the heater Ensure HPH level is



KORBA SIMULATOR 228

due to higher surface area,the FW temperature shouldincrease slightly.

maintained normal.

If the heater is drainedcompletely, then the FW temperature will drop, aslatent heat of steam is not

being utilised for feed water heating.

Boiler heat rate goes up andfuel firing has to increase tomaintain steam parameters.

AIR PRE-HEATER

1. AIR PRE HEATER BEARING TEMPERATURE VERY HIGH.


Cooler may befouled up.

At high bearing temp 100oCthe APH can trip.

Normalise cooling water pressure andflow.

Lub. oil pump may have tripped oncoupling failure

Due to interlock if APH tripscorresponding ID/FD Fan

will also trip.

If lub. oil pump isfound tripped start thestandby pump.

Inadequate cooling water flow.

Unit load comes down toapprox. 50% on CMC.

Restart the APH, IDand FD fan and raise

the unit load.

Alarm comes on at

75oC.

Furnace/flame getsdisturbed, depending onflame configuration. Boiler may trip on loss of flame or furnace pressure high or low.

Note: Starting of 2ndguide brg. pumpautomatically brings inthe second oil cooler into service providedit's charged from the

water side.

2.A. AIR PRE-HEATER ELECTRIC MOTOR TRIPPED.


''APH electrical motor trip''alarm comes on in UCB.

Corresponding ID/FDFans will trip if the air motor does not comeon interlock.

Ensure the air motor comes into service.

The bearing temperature Due to inadequate If possible restore



KORBA SIMULATOR 229

very high protection may have acted.

excess air in boiler (fuel rich mixture)flame out may occur and boiler can trip.

electrical supply andstart the APHimmediately.

Motor/breaker protectionmay have acted.

Fuel rich mixtures may cause boiler explosionand result in damagesto boiler supports.

Ensure sevice air pr.is adequate and air motor isolating valvesare open.

Electrical supply may havefailed.

Unit runs back onCMC mode due toID/FD fans tripping.

If air motor is not available, cut in oilelev. & reduce boiler firing to approx (50%)and transfer load of the correspondingID/FD Fans on theother pair completely.

2.B. APH ELECTRIC DRIVE TRIPPED AND AIR MOTOR FAILS TO START.


Air motor may not belined up.

With a time delay of 30secs. tripped APH'sisolating dampers areclosed and correspondingID/FD fans also trip-out.

Ensure service air pr.is adequate and theisolating valves of theair motor are open.

Service air pressure

< 5 Kg/cm2.

Unit runs back on CMC. If air motor is not available,immediately transfer load of ID/FD fans tothe other pair or start afresh the 2nd pair of ID/FD FANS &maintain draft &airflow in boiler.

Solenoid may befaulty.

Boiler may trip due tofurnace disturbances or flame failure.

Reduce boiler firingimmediately.

3. AIR PRE-HEATER ON FIRE.


Oil deposition on air pre-heater element.

Overall damage to the air pre-heater element and

Unload and stopcorresponding ID/ FD



KORBA SIMULATOR 230

parts. Fans quickly.

High flue gastemperature

Loss of generation due tounavailability of one set of

APH/ID/ FD Fans.

Stop air heater andensure isolationdampers are closed.

''APH fire detectiontemperature trouble''alarm comes in theUCB.

Lower cycle efficiency dueto part load operation.

Wait until alltemperatures becomenormal. Then start air heater electricalmotor again

Flue gas temp. before/after air heater andsecondary air temp.increases.

APH soot blowingmust be doneregularly in eachshift& positively after every boiler light up.

Note : Any APH may be allowed to run on air motor (or air motor bypass mode)provided the gas inlet temperature of the APH is maintained within 370oC(max.)

INDUCED DRAUGHT FAN

1. ID FAN LUB. OIL PRESSURE / BEARING TEMPERATURE TROUBLE.


Lub. oil may be

inadequate.

ID Fan may trip on tank

level by lub. oil pumppressure or very high bearing temperature.

Ensure the stand- very

low lub. oil pump istaken into service.

Lub. oil filters may bechoked.

Unit runs back on CMCto low load limit. (Approx.50%).

Top-up oil level in thelub. oil tank. Clean thefilters.

Greasing long over-due in fan bearings.

Corresponding FD Fancan also trip due to IDfan tripping.

Reduce load on thetroubled ID Fan andalso on the unit, if furnace is getingpressurised.

Corresponding alarm will indicate theproblem area.

Undesirable furnacepressurisation.

Stablise furnace.

Boiler/unit may trip dueto ''all IDs tripping'' or ''allFDs tripping''.

Cut-in oil as quickly aspossible to avoid flamefailure trip.



KORBA SIMULATOR 231

Boiler/unit may trip dueto ''all IDs tripping'' or ''all FDs tripping''.

If available, get ID Fan bearing greased up andGradually increaseloading, on the fan.

If unavoidable,shutdown the ID Fan.

The other fan set must be running beforeshutting down any IDFan.

2. ID FAN TRIP.


Motor over-loaded. Corresponding FD Fanshall trip.

Immediately cut insuitable oil elevations.

CorrespondingFD Fan hastripped.

Unit runs back on CMC to50% load.

Reduce boiler firing fromthe upper elevations tomake it compatible withavailable airflow; to avoidfuel rich furnace.

Spurious electricalfault.

Furnace pressure increases(above atmospheric).

Lub. Oil pressureproblem.

The other ID/FD Fan pair becomes over-loaded if on

auto.

Immediately cut insuitable oil elevations.

Bearing temperatureproblem.

May lead to partial flamefailure due to fuel richmixtures in the furnaceand cause a lot of furnacedisturbance.

Reduce boiler firing fromthe upper elevations tomake it compatible withavailable airflow; to avoidfuel rich furnace.

Corresponding APH may havetripped.

Reduce Unit load toapprox. 50% manually

All annunciationspertaining to thecauses of tripping

will annunciate.

If possible, restart ID Fanand the corres- pondingFD Fan and stablise unit at 200 MW.



KORBA SIMULATOR 232

FORCED DRAUGHT FAN

1. FD FAN TRIPPED.


Lub oil pressure

trouble.

Unit runs back on CMC

to minimum load set point.

If load does not drop

automatically, reduce theload manually to 50% tosuit one fan set.

Bearingtemperaturetrouble.

Load is reduced to 105MW

ID fan has tripped. Oxygen in flue gasdecreases.

Cut in oil to avoid flamefailure.

FD lub. Oilpressure low.(‘‘Lub. Oil pressure

low'' alarm comesin.

Fuel flow drops down toavailable airflow.

Maintain O2 (3%-5%) in

the flue gases.

Corresponding ID fantrips out.

Maintain furnace draught between -5 mm wcl. to -10 mm wcl.

''FD Fan trip''alarm and whitetrip lamp comeson.

Flame fluctuations. may take place.

If boiler has tripped thenmake preparation for light-up again.

Boiler may trip on ''all FDfans tripped''.

2. FD FAN BEARING TEMPERATURE GOING HIGH.


Cooling water flow may be inadequate

Load drops down to 100MW approx. as unit runs back on CMC tomin. load set point.

Reduce load on the FDFan. INSTRUCT localoperator to charge theother lub. Oil cooler.

Coolers may be fouledup.

Corresponding ID Fantrips.

Bearing temperatureincreases. Alarm

comes in at 95oC.

Unit may trip on '' AllFDs tripped''.

If the other fan set isnot running andavailable for operation,put them in to avoid a unit trip.



KORBA SIMULATOR 233

FD Fan-A trips when bearing temperature

reaches 105oC.

PRIMARY AIR FAN

1. PA FAN TRIPPED


''PA Fan Trip'' annunciationcomes on.

Hot primary air header pressure may dip and cause '' PA header pressure low''alarm at 585 mm wcl.

Maintain furnacedraught (-5 mm wcl to10 mm wcl).

If the tripping is due to high

bearing temp. (104oC).Corresponding alarm comeson before tripping of the fan

(85oC).

Mills start tripping

from top until nomore than three millsare in service.

Maintain PA header

pressure at 760 mm.

If the 2nd fan isrunning and controlis on auto, 2nd fantakes up load and

bring up the PA header pressure tonormal (760 mm).

Check the bearingtemperatureindcations locally andin UCB, for the fan.

Spurious electrical tripping. Discharge damper of tripped fan closesand regulating vanescomes to minimumposition. Turbineload comes down upto approx. 50% onCMC.

Check the runningmills for possiblechoking.

Boiler has tripped. Unit runs back on CMC. If not onCMC, reduce load

on turbine up to40%-50% manually.

Lub. Oil pressure may be very low.

CHECK the lub. Oilpump system.

If possible, RESTART and load the PA Fan



KORBA SIMULATOR 234

and stablise unit at 200 MW.

2. PA FAN VIBRATION TROUBLE

FAULT CONSEQUENCE ACTION''PA Fan vibrationhigh'' annunciationcomes on (1.5mm/sec)

High vibration can damagethe bearing and shaft of the fan

Reduce loading in thefan immediately, loadthe other fan if that'srunning or take thesecond fan into service.

Damaged bearing. At 2.5 mm /sec pk., PA fanis recommended to betripped.

Pulverisers in excess of 3,may have to be stopped

and unit load may have to be lowered.

Instruct the localoperator to check up

the bearings, lub. oilpressure, bearingtemp and vibration etc.

Loose bearing pedestal bolts.

Reduced boiler efficiency at part load.

Quality of lub oil may have deteriorated.

Machine down timeincreases the maintenanceoverhead.

If required (on account of high vibration) stopthe fan immediately.(Follow shutdownprocedures).

3. PA FAN LUB. OIL TROUBLE


Correspondingfacia/window glowson.

It can starve the bearing of oil, brg. Temperature cango high. It can evendamage the bearing.

Check if lub. oil pumpis running andpressure adequate(2.5

g/cm2.)

Lub. oil pressure may be lower than 1.6

Kg/cm2.

Fan trips if lub. oilpressure Lo-Lo alarm

comes on at 1.2 Kg/cm2.

CHECK if the other pump comes on

interlock, at 1.6kg/cm2. if pressurekeeps falling.

Filters may be choked. Pulverisers in excess of 3 will trip and the boiler loadreduces.

Changeover the lub. oilfilters to maintain lub.oil pressure.



KORBA SIMULATOR 235

Pump glands may beleaking.

COAL PULVERISER SYSTEM

1. PULVERISER DP GOES HIGH.


''Pulveriser DP high''alarm comes at 240 mm

wcl. mill DP.

The pulveriser may bechoked up completely.

This may damage thedust guard or the motor or the mill coupling

because of overloading.

Maintain pulveriser outlet temperature at 750C.

(if needed, take controlon manual).

Coal pulveriser may beChoking up. Boiler steampressure/temp may come down. Turbineload comes down.

Cut in another mill Raiseload on T/G.

Pulveriser motor getsoverloaded.

Reduce feeding. See if DP improves.

Pulveriser out-let temperature falls low.

Choking reduces themill output.

Also check up locally thecondition of reject mouth

whether it is choked upand air is coming.

Too much coal feeding. At high DP (240 mm) or mill current (38 amp.),feeder speed runs back to minimum.

NOTE:If pulveriser iscompletely choked up,STOP feeder, STOP mill.Issue, work permit toBMD (Boiler Maintenance Division).

Reject mouth choked up because of some foreignmaterial stuck up inreject sprout (not simulated).

Oxygen (%) goes highdue to reduced coalinput to furnace.

Moisture content of thecoal may be high.



KORBA SIMULATOR 236

2. COAL FEEDER TRIPPED.


Motor may beoverloaded.

Feeder tripping will stopthe coal flow to the mill.Hot air damper closes

after a timedelay of 30 secs.

After feeder tripping check if hot air damper & gate haveclosed & cold air opened

100%.

Silo gate closed.

No coal flow to thepulveriser for more than 10secs.

Mill current goes no loadamps Boiler/ unit loadalso comes down. Changefuse if needed.

Check the healthiness of feeder's electrical supply.

Adjacent mill will trip (if it's feeder is not

established) due to loss of ignition energy.

Transfer fuel master tomanual control & prevent

the overloading of other running coal feeders.

Take the other availablepulveriser in service andraise load.

3. PULVERISER TRIPPED


Ignition energy may

have been lost.

If the adjacent mill

feeder is not established, that milltrips out.

Restore ignition support

and cut-in the trippedadjacent mill.

PA header pressuremay be low (585mm wcl).

Boiler/unit load may come down.

Stabilise furnace draft and bring down the O2% to 4%

- 5%.

Anyone PA fantrips.

Oxygen percentage will start increasing.

Cut in oil guns andtransfer fuel master tomanual, if foundnecessary.

Boiler may trip due tofurnace/flamedisturbances.



KORBA SIMULATOR 237

4. MILL OUTLET TEMPERATURE GOING HIGH.


Mill dischargetemperature high

alarm comes on at 95 0C.

At 95 0C mill cold air damper opens 100% and hot air

damper and gate close fully.

Ask local operator to remove all men

working near/onthe mill.Change in coalquality(volatilematter).

Mill temp. starts comingdown, increasing thepossibility of mill choking if coal feeding is not reducedimmediately

Ensure HAG/HADof the mill areclosed and CAD isopened

Pulveriser fire dueto lean (explosive)air coal mixtures inthe mill.

Prolonged operation of themill with high outlet tempincreases the possibility of explosion.

Cutting all air supply and coalover feeding cansmother smallfires.

Ensure continuouscoal supply for themill.

Temperaturecontroller may havefailed.

Mill fire may spread to other parts of the mill piping.

Cold air damper may be jammed-up.

If needed, transfer the mill air controlto manual &maintain temp./flow.

5. MILL CURRENT HIGH (MORE THAN 38 AMP.)


Grindability index low. Mill requires morepower for the sameoutput.

Reduce feeder speed toprevent motor overloading.

Pulveriser capacity reduced due to theclassifier setting toohigh.

At motor load of 38 Amp. Feeder speedruns back tominimum (30%)rated).

Put another pulveriser inservice to maintain unit load.

Pulveriser may bechoking up.

Unit load comesdown.

Maintain PA header pressure at 760 mm wcl toavoid coal hang-up in mill.



KORBA SIMULATOR 238

Pulveriser may not have been cleared for a long time.

Dischargetemperature of themill tends to increase

back.

Instruct local operator tooperate the reject gate toevacuate the mill.

At 95 O C hot air damper closes. HAGalso closes after a time delay.

Instruct shift chemist tocheck for coal fineness andre-adjust the classifier setting.

Mill may trip on over load and other running feeders willoverload, if on auto

6. COAL FLOW TO MILL INDICATION GOES OFF.


Feeder belt may be broken and feeder coal flow is lost.

Pulveriser discharge temp.may increase. Pulveriser DP reduces.

Maintain furnace draft and oxygenpercentage.

Feeder dischargechute may get plugged.

HAD & HAG close at 95 0Cand CAD goes to 100 %opening

Take associated oilguns in service tostabilise furnace.

Mill motor current comesdown due to gradual lossof coal, as mill inlet chuteis getting plugged.

Stop the mill after it gets emptied.

Feeder coal flow transmitter may befaulty.

HAD & HAG close at 950C. as mill outlet tempgoes up with loss of coal tomill.

Take associated oilguns in service tostabilise furnacedraught.

Feeder trips on overload,as the coal chute iscompletely plugged.

Adjust fuel master tomaintain loads on therunning feeders (auto).

Other feeders start loadingup, if on auto.

If other mill isavailable, cut-in themill and raise unit load.

Look for reasons for the too much moisturein coal.



KORBA SIMULATOR 239

7. FUEL FLOW RUN BACK TO LESS THAN DEMAND (DROPS BY 20%).


Spurious electricalmalfunction.

All feeders get unloaded by 20% (Combustion

control is on Auto).

Raise fuel master output to increase

load.

Combustion controltrips to manual.

Airflow reduces by 20%. Continue operation on'Manual' mode.

''ACS auto to manualtransfer’’ alarmcomes in.

Drum level drops due toshrinking.

Maintain millparameters.

Boiler pressure alsodrops.

Maintain boiler parameters.

Unit load decreases. Maintain unit load at 100% MCR.

If no action taken, loadsteadies down at 80% of rate value (approx.).

If required, take theother available mill inservice.

8. PULVERISER HOT AIR GATE FAILS CLOSED.


Spurious electrical

signal causes theHAG to close.

Pulveriser cold air damper

goes 100% open. HAD goesclosed.

Cut in corresponding oil

elevation to stabiliseflame.

Someone may haveclosed hot air gatelocally.

Reduce coal feeder loading to avoid millchoking due to low temperature operation.

Pulveriser temperature startsdropping.

Instruct local operator to open the hot air gatelocally or inform C&Imaintenance.

Pulveriser current runs up if feeder speed is not reduced(Because of poorer grindability of high moisturecoal).

If unavoidable, stop thepulveriser and cut-in a new mill.

Pulveriser DP may go low due Stabilise unit load at



KORBA SIMULATOR 240

to reduced air volume if CADis not opened.

200 MW.

NOTE: All pneumatically operated dampers must be reset and put on remoteoperation, only after ensuring E/P converter and the actual damper positionare matching.

9. PULVERISER AIRFLOW FEED BACK OFF SET 25% HIGH AIRFLOW READING)


Flow measuringpitot tube may beplugged.

HAD and CAD closepartially to compensatefor increased airflow feed back signal.

Reduce feeder speedslightly to maintainpulveriser DP.

UCB instrument for airflow indicator may be faulty.

Mill DP increase as thecoal retention in the millgoes up due todecreased airflow; hencemill DP goes up along

with pulveriser current.

Take mill air control onmanual and adjust theairflow to the required 60

T/Hr.

Mill air control,if on auto reducesthe actual millairflow and airflow reading drops a little.

Pulveriser output comesdown and reject rategoes up.

Instruct local operator toevacuate mill reject locally.

Boiler/unit load comesdown and oxygenpercent increases

If possible, load up other mills to maintain unit load.

10. Pulveriser PA flow Temperature Compensation Thermo-Couple Fails.


Thermocouple wire broken.

Airflow indicationcomes down but actual airflow remainsas it was initially.

Reduce feeder speed tocontain mill DP.

Hot Primary Air temperatureindication goes up to400 deg. C. (falsely)on DAS and ''Hot PA

HAD/CAD modulateto restore airflow;thus raising theactual airflow throughmill.

If feeder runs back, dueto high mill DP; let millget emptied and stabilisemill.



KORBA SIMULATOR 241

to mill temp. HI''alarm comes on DAS.

Mill DP goes up dueto excessive airflow.

Transfer mill air controlto manual to control mill

Airflow and temperature.

11. COAL FEEDER FLOW INDICATION LOST.


Belt broken. If belt is broken coalflow to pulveriser stopsafter sometime andpulveriser current comes down.

Immediately take the fuelmaster on manual andprevent overloading of other feeders.

Transmitters failure (Inthis case, feeder trips tomanual from auto) and

' ACS to manual'annunciation flashes.

If pulveriser is runningnormal (without drop incurrent) that indicates

flow transmitter failure,in which case other feeders overload tomaintain boiler load, if on auto.

Maintain O2 % approx.

3%-4%.

If other feeders haveoverloaded, reduce their output gradually.

A fuel rich mixture may result in furnaceexplosion if boiler does

not trip on flamefailure, on account of increased firing andinsufficient airflow.

If flame quality hasdeteriorated (as shown

by scanners) and opacity

has increased,immediately’ hand-trip'the pulveriser (if severefluctuations of furnacedraught are noticed) andsee if things improve.

11. PRIMARY AIR PRESSURE CONTROLLER MALFUNCTION(P A HEADER PRESSURE DOES NOT CHANGE WHEN REQUIRED).

FAULT CONSEQUENCE ACTION Fan vanes freeze.

Mechanical jamming.

At PA header pressure

of 585 mm wcl. allpulveriser trip out after 5 sec.time delay.

As soon as drop in

header pressure isnoticed immediately tripthe new mill, which is

being taken in service.

If more air isdemanded (whiletaking another

Boiler will trip if no oilelevation is in serviceand all pulverisers trip

Ask local operator tocheck the freeness of guide vanes, control air



KORBA SIMULATOR 242

pulveriser), controller output goes to 100%But actually header pressure drops).

out. supply & local switch onRemote for operationfrom UCB.

At 525 mm wcl PA header pressure, allmills tripinstantaneously.

Pulverisers coal output reduces at reducedpressure of primary air.

NOTE:E/P converter and theIGV positions must bemade equal before it'sput on 'Remote'; to avoidany inadvertent changein PA header pressure.

TURBINES AND AUXILIARY SYSTEM

1. TURBINE SHAFT OIL PUMP FAILURE.


Broken impeller due tomaterial defect.

High vibrations candamage the bearings of the turbine.

Immediately trip theunit manually fromUCB.

Lub oil/ control oilpressure drops, AOP-1comes on AUTO (inter-lock).

Continued operation of the turbine in thiscondition is not recommended. It may result in damage toother turbine parts.

Cut-down boiler fireimmediately but gradually andshutdown

High vibration in bearing No.1. Once Trip oil Pr. is <5.0Kg/cm

2. ESVs will

CLOSE

Turbine will Trip without any fault indication

2. TURBINE LUB OIL RESERVOIR LEVEL LOW.


A leak in the lub oilcooler or oil line.

At -900 mm. MOT level fire protection-1

operates. Turbineelectrical trip isinitiated.

If possible quickly,switch over the

leaking cooler to theone on standby andsee if MOT levelimproves.

''MOT level low' alarmannunciation' in UCB'.

Vacuum breaker opens.

If unit trips, RESET turbine fire protectionand make-up lub. Oil



KORBA SIMULATOR 243

level in MOT.

''Fire protection oil tank level LOW'' alarm comeson in UCB.

LP bypass, if charged,trips on low condenser

vacuum.

Proceed to revive theunit, after getting thelub oil leakageattended and MOT level topped up.

Boiler trips on R/Hprotection after 10secs time delay.

3. LOSS OF TURBO SUPERVISORY POWER.

Power supply to turbo-supervisory cabinet failed due to blowingup of the fuse.

All turbo-supervisory parameter indicationsassociated with the TSI

will be lost, including vibration expansionand shaft position.

Get the fuse replaced.Mean while do not change any parameters.

TSI power supply failure alarm comes in

4. BROKEN LAST STAGE BLADE OF L. P. TURBINE.

Turbine bearing vibrations go up,especially bearing No.4.

- Immediately trip the turbine/unit from UCB.

Broken pieces from the blade may damage the condenser tubes,resulting in condenser tube leakage.

- Prepare for shutting down the boiler by cutting out the coal firing.

5. MAIN TURBINE ELECTRO-HYDRAULIC CONTROLLER FAILS HIGH.

The machine becomesoverloaded unduly

Immediately start reducing thehydraulic governer toget the desired load.(When the speeder gear position gets low enough to take over from EHC, a slight decrease in secondary oil pressure to HP/IPcontrol valves is seen.)



KORBA SIMULATOR 244

''EHC Faulted'' alarmcomes on.

Boiler metal temp goes upas the boiler loads up (If the unit is on CMC or

boiler follow mode).

EHC output goes to100%.

Generator/generator transformer windingtemperatures start goingup, as generator overloads.

Turbine loads up tomax limit set by hydraulic speedcontrol.

Continued and prolongedoperation may lead totripping of T/G unit onhigh windingtemperatures of generator or transformers due tooverload.

Lowering of startingdevice, instead of thespeeder gear, bringsthe load change muchfaster. After thedesired load has beenreached, speeder gear is lowered until it takes over; and thenstarting device isagain raised to 100%

HP control valves go100% open and the

boiler firing goes upon boiler follow mode.

6. TURBINE AXIAL SHIFT HIGH.

"Thrust bearing metaltemp high'' alarm may come in UCB.

Unit may trip on highthrust pad wear protection (0.6 mm).

Immediately de- creaseload on M/C and watchif axial shift improves.Otherwise, unit tripson thrust pad wear protection. (Boiler may trip on R/H protection)

Unit load may have to be reduced, resulting inloss of generation

''Axial shift high''alarm may appear.

Excessive axial shiftscan cause rubbing of moving and stationary parts.

Silica/ chemicals may have deposited on the

Vacuum breaker valveopens up after tripping

If unavoidable, trip theturbine manually from



KORBA SIMULATOR 245

turbine blades. and vacuum getskilled.

the UCB for investigations by the

T/G maintenance.

7. TURBINE LUB. OIL TEMPERATURE IS GOING UP.

Lub. Oil coolers may befouled-up. ''Lub oiltemperature after coolers high'' alarm at

47 0C. (UCB

annunciation).

Oil viscosity comesdown with increasingtemperature of lub oil.

That may lead to boundary lubricationand metal-to-metalcontact. It may causeextensive damages to

T/G bearing and high brg. Vibrations.

Take in service thestandby lub oil cooler if available.

If high vibrations areobserved, trip theturbine immediately.

''Turbine lub. Oiltemperature high''

alarm at 47 0C. (UCB

alarm)

Bearing outlet oil tempincreases. Brg. outlet oil temp more than 78oC causes acceleratedaging of oil and soadditional revenuelosses for each oilchange.

Ensure ARCW/CW water pressure isadequate.

Bearing metal temp

goes up ''Brg. temphigh'' alarm comes at

90oC.

Maintain bearing outlet

oil temp below 78 oC tocurb aging of oil.

8. LOSS OF CONTROL POWER TO TURBINE EHC SYSTEM.

Control supply may have gone off due toearth fault or blownfuse etc. and ''EHCcontrol fault’’ alarm

comes on.

HP/IP control valves gofully open and unit load goes up to max.

Start reducing thestarting device till theload comes back todesired value.

Generator overloadingmay lead to windingtemperatures increase.

Reduce speeder gear till a further decreasein load is observed.Raise the startingdevice to 100%.

EHC output goes to100%.

Boiler firing may increase depending on



KORBA SIMULATOR 246

the operation mode &overload the mills.

Indications on turbinecontrol console goesoff.

Furnace pressure may go very high. ID fansmay get overloaded.

Close the isolating valves on secondary oillines from EHC.

Maintain unit load &ask the boiler operator to maintain the millfiring, furnace draft &drum level and steamparameters.

9. TURBINE STRESS EVALUATOR.

Electrical fault. Operator will have togo by matchingindividual metaltemperature of turbine

with available steamtemperature. Noindications direct) of stress limits shall beavailable.

Instruct the localoperator to switch off the TSE influence(TSE influence off annunciation comeson).

''Turbine stressCubicle fault' and'Turbine stress effect off annunciations come

on.

'Stop reference limiter'light comes on and any further increase inspeed or load is stops.

Frequent changes insteam temperaturesmay cause unduestresses in turbine, as

visual stress levels'indications will not beavailable for operator to go by.

On the turbine consolehousing AOP/JOPSLCs etc., press themaster set point release push button toremove ''Stop ref.limiter'' lamp. Now theload or speed referencecan be manipulated tomaintain desired load/

speed.

On the TSE, the redlamp starts flashing.

Maintain recommendedrate of turbine loadchanges.





KORBA SIMULATOR 248

H2 pressure drops. Hydrogen leakage will require morehydrogen cylinders to

be charged. Hyd.consumptionincreases.

Continuedoperation at reduced load (165MW) with 3 gascoolers ispermissible.

3. LOSS OF H2 / SEAL OIL PRESSURE.

''Generator cooling /seal oil working filters clogged'' alarmmay come on.

Seal oil DP goes low.(Alarm at 0.9

Kg/cm2)

Instruct localoperator to chargemore hydrogencylinders.

Seal babbit liners may bedamaged. So due toincreased clearances more

seal oil may drain.

H2 may leak out of

the system.

Maintain Gen. loadas per generator capability curves;

with falling H2 Pr.

Rotor temperaturegoes up.

''Seal oil pressure low'' alarm

comes at 3.6 Kg/cm2 andreserve seal oil pump comeson interlock.

Hot gas temperaturehigh alarm comes at 75 0 C.

Ensure rotor andgen. winding tempare within limits.

Under extremeconditions generator may have to be

tripped, manually.

If DPR is found to be malfunctioningget it bypassed,

locally.

4. GENERATOR HYDROGEN LEAKAGE.

H2 pressure drops. Hot gastemperature goesup (High alarm at

75 0C.

Reduce loadimmediately.

H2 pressure (2.8 Kg/cm2

low alarm sounds.

Rotor temperaturegoes up.

Instruct local operator to charge more

hydrogen cylinders &maintain H2pressure at 3.5

Kg/cm2

Seal oil pressure decreases tomaintain DP. Reserve seal oilpump may come on

T/G may have to be tripped due tohigh rotor winding





KORBA SIMULATOR 250

T/G may trip dueto low stator water

flow at 13 m3/hr.

MISCELLANEOUS SYSTEMS

1. LOSS OF STATION AIR PRESSURE.

Leakage in the pipe At a pressure o f 3.5

Kg/cm2, ignitor oil/atom

air pressure low alarmcomes and all ignitors tripout.

Immediately increase heavy oil

pr. to 12.5 Kg/cm2.

Compressor tripping.

Pressure indication in

UCB starts to drop.

This may lead to oil valves

tripping if correspondingoil flame scanners areflickering and possibility to boiler tripping on 'Lossof all fuel' or 'FlameFailure'.

Attend to the fault

& get the leakages,if any, rectified.

Low service air pressure alarm comes

at 6 Kg/cm2.

OPEN Instrument&service air inter-connection valve.

2. LOSS OF INSTRUMENT AIR PRESSURE.

Compressor tripping. At 5 Kg/cm2 instrument

air pressure thefollowing valves willOPEN

Decrease load gradually to keep drum level incontrol and also therate of vacuum drop.

Leakage from theflange.

Maintain drum level by scoop adjustment anddo not change anythingon the unit.

Pressure indication

drops.

1 DA overflow valve (MC-

84).

Low instrument air Pr. alarm at 5.5

Kg/cm2

2 BFP re-circulation valves.





KORBA SIMULATOR 252

9 Ejector steam pressurecontroller AS-56, AS-79.

10 Steam to D/A controller AS-68.

All other pneumaticactuators will remainfrozen at their position.

Turbine may trip on vacuum protection or boiler can trip on low drum level.

2. REHEATER TUBE LEAK OR SECONDARY SUPER HEATER TUBE LEAKAGE.

Overheating of tubes. Hot R/H or main steam

pressure drops.

Immediately cut down

firing and reducepressure and unit load.

Fire side corrosion. HP control valves openmore to maintain loadas per reference value.

Unit may have to beshutdown immediately for maintenance asthese leakages candamage theneighbouring tubes.

Severe fluctuations influe gas DP across

platen S/H, RH,economiser etc. takeplace.

Furnace draught becomes unstable and

goes up.

ID fans load more tomaintain draught.Make-up consumptiongoes up.

Furnace pressure goesup.

Pulveriser fires more tokeep the throttlepressure up. If on auto,flue gas temperaturesincrease.

Boiler pressure(MS/RH) drops.

Relevant alarms willannunciate.

Metal temperature in boiler goes up andsteam attemperation



KORBA SIMULATOR 253

goes up.

D/A level tends to drop.Neighbouring tubesmay also get damageddepending upon theseverity of leakage.

4. WATER WALL TUBE LEAKAGE.

Corrosion. It can damage theneighbouring tubes.

Reduce load to about 150MW

Over heating of tubes. Feed water flow goesup, to maintaindrum level.

Reduce firing to keep steamtemperature under control.

Indications will be Make-upconsumptionincreases.

Eventually unit has to beshut down. So makepreparation for a plannedshut- down.

Drum level dropsdepending upon theseverity of leakage.

D/A level Hotwelllevel drop gradually

Throttle pressuredrops.

Condenser surgetank level low annunciation comeson if cycle make-upis open.

NOTE:

A decrease in boiler water pH is theprimary indication of any water wall tubeleakage.

Boiler metal temp goup as firingincreases tomaintain throttlepressure which goesdown due to leakage

Furnace draught starts hunting.



KORBA SIMULATOR 254

5. BOILER WATER SILICA HIGH.

'Boiler water chemistry trouble'alarm comes in.

Silica carry-over increases resultingin formation of silicates on turbine

blades. Turbineefficiency comesdown over a time.

Start HP dosing and openCBD. Reduce load anddrum pressure, as per chemist's advice tomaintain drum water silica not more than 0.5ppm.

Dust ingress intophosphate andhydrazine dozingtank. Also duringshutdowns becauseof SH /RH tubeleakages.



KORBA SIMULATOR 255



KORBA SIMULATOR 256

EFFICIENCY ASPECTSOF

POWER PLANTS



KORBA SIMULATOR 257



KORBA SIMULATOR 258

EFFICIENCY ASPECTS OF POWER PLANTS

With tremendous rise in electricity demand throughout the world, need of enormousincrease in sizing and installation of power plant has been felt two to three fold. Thishas imposed an urgency to ensure that the plant is operated and maintained as near to optimum conditions as possible. Cost of fuel (Coal, oil, gas) is rising day by day

and unless proper measures are not taken to optimise the usage, operating power plants most efficiently and economically will not come true. At current Indian fuelprices, loss of one percent in efficiency will incur an additional fuel (coal) cost of over Rs. 23 millions per annum (equivalent of additional 250 Tones of coal/day).

It is of paramount importance that power plant engineers get aware of causes of poor efficiency and adopt methods to control and keep check on process parameters those

will be affecting the power plant efficiency.

In this chapter, an attempt has been made to educate engineers so as to find themeans and ways in solving numerous problems concerning efficiency losses in power station operation.

The Temperature–Entropy (T-S diagram) isrepresented by area between the curve andthe entropy figures (0-10 KJ/kgK).

Temperature starts from –273 0C to 0 to 7000C. The curve representing boiling water starts from 1000C and reaches to around3700c and in rising side entropy scale to 4-6KJ/kgK and the lowering side represents thedry saturated steam. Sensible heat isrepresented between y-axis and x-axis

before latent heat covers. Latent heat is

represented by the rectangle between thecurves traced by entropy figures. A horizontal line gives the pressure andextends upwards. The critical point occursat the conditions (221.2 bar abs, 374.15 OCtemp and 3.17cm3/kg volume) and at themore elevated condition the steam reachesin super critical stage.

The curve represents the total heat, useful heat & the rejected heat as well. An idealRankine Cycle incorporating reheat and regenerative feed water heating can berepresented by the curve.

In the ideal cycle the steam expands in the turbine and the expansion is assumed to be frictionless and adiabatic. The expansion of steam continues until some reducedpressure. Condensation at a constant temperature takes place until all latent heat had removed (rectangle covered under X line as rejected Heat). The formulae that follow can be referred for calculating the thermal efficiency. There are two ways toimprove the basic Rankine efficiency. Those are: Reduce the rejected heat component and then increase the useful heat component.



KORBA SIMULATOR 259

The rejected heat component is dependent primarily upon the condensationtemperature and this in turn is determined by the cooling water temperature.(usually is controllable a little.).The useful heat is determined largely by steam temperature.

The efficiency can be improved by restricting limits of upper & lower temperature by actually resorting to Reheating. Ideal Cycle efficiency for turbine conditions at 158.6

bar/566 oC/566 oC is about 47.2 %. A combination of reheating and feed heating

will give an even higher ideal efficiency.

The Carnot efficiency is obtained for any substance working between the limits of temperatures and the Carnot efficiency is given by (T1-T2)/T1 in which T 1 is theupper absolute and T 2 is the lower absolute temperature and the heat addition &heat rejection are isothermal process and that the expansion and compression of the

working substance is isentropic. Of course no such substance as portrayed in theCarnot cycle exists. However the Equivalent Carnot cycle is one, which is equivalent of a given Rankine cycle. The temperature is assumed to be constant at the averagetemperature at which heat is received in Rankine cycle; they give the same results.Let us take a case of a unit having different figures.

TSV pressure: 240 bars TSV Temperature: 590(0C)

Final feed temperature: 270(0C)

Back Pressure: 30 mbar

Reheat temperature: 570(0C)

Reheat pressure:50 bars abs.

The efficiency of Unit –2 converts 83% of the available heat into electrical output.

Selected parameters and its complete T-S Diagram (Ideal Steam Cycle)

Steam Parameters: Ms Pr = 160 Bar, SH temp = 570oC,Cond.pr = 30 mbar,

RH temp = 570oC, RH Pr. = 44 Bar

Carnot Efficiency Basic: 52.1%(with dry/sat steam between 347oC & 24oC)

64.8%(Between 570oC and 24oC)

Rankine Cycles Efficiency (Ideal): 41.4%

Rankine Cycle Efficiency with S/H: 45.7%

Rankine Cycle efficiency with S/H & R/H: 47.5%

Rankine Cycle Efficiency

(with SH, RH &Regenerative feed heating): 53.2%(with feed Water temp = 180oC)

55.8% (with Feed water Temp. 250oC)

Useful heat Thermal efficiency =

Total heat



KORBA SIMULATOR 260

Total heat - Rejected heat =

Total heat

Rejected Heat = 1 -

Total Heat

Condensate temperature:24(297.1)0C/K Entropy of final feed: 2.9763 KJ/kgK

Total heat at TSV: 3469.9 -do-Entropy at TSV: 6.3539 -do-K

Total heat at R/H inlet: 3013.0 -do- Total heat at IP inlet: 3595.1 -do-Entropy at IP inlet: 7.1769 -do-K Heat in final feed water: 1185.2 -do-Heat added in Boiler (H1-hf):2284.7-do-Heat added in R/H(H1-H2): 582.1-do-

Total Heat added: (1) 2866.1 -do-Entropy change(S2-S1):(2) 4.2006 -do-K

Heat rejected T.(S2-S1):(3) 1248.0 -do- Work done :(1)-(3): (4) 1618.8 -do-Ideal cycle frequency :(5) (4)100/(1):56.5% Alternatively Average temp. (1)/(2): 682.5 K (6) Equivalent Carnot efficiency: (7) 56.5 %

= { (6) –T } 100/(6) Overall efficiency: 46.9%

If a comparison is made between the efficiency of a basic Rankine Cycle without reheat regenerative feed heating and the one with reheat and regenerative feedheating an apparent gain in efficiency of the cycle can be noticed. It can be explained

on the basis of equation for efficiency of cycle; incorporating reheating increases thetotal heat, input, and incorporating feed heating, reduces the amount of heat rejected, thereby increasing the cycle efficiency.

In general, entire cycle efficiency of a power station depends upon the efficiency of itscomponents i.e. boiler, turbine, generator, pumps etc., efficiency of which in turndepends on many other factors as discussed here.

Cycle Efficiency (ξ)= ξ (S.G) * ξ (Tur) * ξ (Gen.)

BOILER EFFICIENCY

There are two ways of determining the boiler efficiency: i) Direct & ii) Loss method.

Direct method was standard for long time, but is little used nowadays. It is basically the straight forward of measuring the heat supplied in a given timeand heat added to the steam in the boiler. By this method the efficiency of a non-reheat boiler is:



KORBA SIMULATOR 261

Efficiency = {Enthalpy of (steam – feed)* steam flow} 1/Cv .(coal) *Coal quantity Per unit time

Losses Method: The efficiency of a modern boiler is dependent basically upon theefficiency of combustion and the heat transfer within the boiler.

The efficiency of the Boiler is therefore 100% -losses. Thus, if the losses are known,the efficiency can be derived easily.

The losses in the boiler comprises of the following:

1. Dry flue gas loss.2. Moisture loss: a. Moisture in fuel.

b. Combustion of hydrogen.c. Moisture in ambient air

3. Unburnt carbon loss: a. Carbon in bottom ash. b. Carbon in flue gas

4. Incomplete combustion.5. Radiation and unaccounted losses.6. Ash hopper loss.7. Mill rejects loss.

Dry Flue Gas Loss

This loss is due to residual thermal energy contained in the dry flue gas when itstemperature is too low for further useful work. At this point it is exhausted toatmosphere. This loss constitutes the largest portion of boiler losses and isdependent upon-

a. Quantity of dry combustion gases. b. Temperature rise between FD Fan inlet and gas exit temperature.c. Mean specific heat of the flue gases (Constant pressure).

The amount of excess air supplied over and above the theoretical air, has the greatest bearing upon this loss as this causes both quantity and temperature of the flue todeviate. A change in excess air quantity by 5% effects + 1.0% in dry flue gas loss.

Dry flue gas loss ={100/12*(CO2+CO) + C/100+(S/267)-C ash}*30.6 (T-t) K J/Kg. (In

fuel)

Alternatively Dry flue gas loss % = K x (T-t) (on GCV v basis)

In the dry gas loss equations, the abbreviations are as under:

C is %carbon/kg , CO2,CO,N2 all in % by vol. as present in dry flue gasS %/kg fuel, M is Moisture /kg fuel; H is %kg fuel; h is moisture in kg/kg air Ma is dry air for comb in kg/ kg fuel; c is carbon in refuge in kg A is ash content in kg/kg fuel.

GCV v gross calorific value KJ/kg, NCVp is net calorific value KJ/kg

t is F.D. air inlet temp., T is the exit air temp at A/H outlet



KORBA SIMULATOR 262

K is constant and have values as given below.K = 0.68 for anthracite

= 0.63 for bituminous= 0.70 for coke= 0.56 for fuel oil.

Optimisation of Total air supply Optimum Co2 % at Boiler outlet

Wet Flue Gas Loss (Moisture Loss)

This loss is the thermal energy in water vapour entrapped in flue gases leaving boiler. The water is in the form of superheat steam if exit gas temperature is above the dew

point at the stack. The total moisture loss is due to water derived from three sources:-

i) Total sum of free & inherent moisture in fuel.ii) Products of combustion of hydrogen in coal;iii) Moisture in atmospheric air.

Wet flue gas loss =(M + 9H)/100 [1.88 (T-25) + 2442 + 4.2(25-t)] KJ/Kg. of fuel.

Sensible heat in water vapour. = Wet flue Gas Loss - (GCV - NCV)

Moisture in combustion air loss = Ma*h*1.88(T-t) KJ/Kg.fuel

For solid liquid fuels Ma =3.034 N2/ (CO2 + CO ){C/100 + S/267 -C in ash}Unburnt Carbon Losses

The main source of this loss is due to the carbon contained in bottom ash or entrained in fly-ash leaving boiler furnace.





KORBA SIMULATOR 264

Mill Reject Loss

This loss may be kept very small if the milling plant is designed, operated andmaintained correctly. It can be calculated by sample of reject for calorific value and

weight of rejects.

Note: Efficiency calculations done on the basis of NCVp yield higher values thanGCVv. Hence, calorific values must be specified clearly.

Most of these boiler losses can be kept under acceptable limits by ensuring completecombustion at minimum excess air. Control of combustion process requiresregulation and distribution of fuel & air to and within the furnace using:

i) Milling plant; ii) Burners; iii) Air control equipments.

The other factors, which must be considered, are

a. The need to cool the combustion products below the softeningtemperature of ash before the leaving the combustion chamber.

b. The need to avoid deposition of burnt coal onto wall tubes. This caninduce corrosion of tubes, ultimately involving a loss of plant availability.

c. The need to avoid acid corrosion of lower temperature flue gases. (Theexcess air quantity and flame temperature can influence Dew point temperature).

TURBINE EFFICIENCY

The efficiency of turbine is dependent upon the following factors.

Internal Losses

Nozzle Friction: The effect of nozzle friction is to reduce the effective heat drop of steam as it passes over the nozzle. The velocity of steam is reduced as it subsequently strikes the moving blades. Because of reduction of velocity there will besome shock as steam strikes the blades because blade profile is designed so that steam glides over it (for a particular steam velocity).

Blade Friction: Its effect is same as of nozzle friction. Without friction the outlet relative velocity of steam would be same as inlet but because friction cannot beavoided, velocities are reduced to 90%. As friction increases, steam expansion tendsto be more ''irreversible''.

Actual heat dropStage efficiency =

Isentropic heat drop

Disc Friction: The discs on impulse turbine shafts rotate in an atmosphere of steam. The disc surface friction causes some drag and produces eddies of steam causingloss of power. This effect is more pronounced where the steam is densest.



KORBA SIMULATOR 265

Diaphragm Gland and Tip Leakage: In pressure-compounded turbine there is a pressure drop across each fixed nozzle of diaphragm. Therefore, the gap betweendiaphragm and shaft is a source of steam leakage, which can be minimised by providing inter-stage glands for sealing. There are balancing holes on the discsthrough which steam can leak and cause disturbances when it joins the steamcoming from the nozzles. It is extremely important, therefore, to maintain eccentricity to minimum during start-up and loading.

On impulse/reaction machines, there is pressure drop across each stage or blade;thus there is steam flow around tips of all fixed and moving blade. Seals at the tips inradial & axial directions are provided. Because of wear & tear of the seals, leakageloss can amount from 0.55% to 1.0%.

Partial Admission Loss: In nozzle-governed machines in particular, and in throttlegoverned machines at part load conditions, steam is subjected to Throttling. Apart from that in nozzle-governed machine, steam is admitted to one or more areas of theinlet nozzle ring. The valve lifts are varied in sequence, as the turbine is loaded untilat full load the valves are fully open. The moving blades alternately come in and off contact of any running arcs. In the process, they run full of steam while in contact

with running arc and from eddies when they come in line with non-running arcs. This leads to windage losses. However, nozzle governed machine can be said to bemore efficient than throttle governed machines, at part load. While, at full load thethrottle governed machines are more efficient.

The basic construction and assembly of partial arc and full arc i.e. nozzle governedand throttle governed turbines, are a lot similar with only real difference being theabsence of the control stage in full arc admission turbine. This arrangement dispenses with excessive stresses in the HP turbine blades and enhances thereliability of full arc admission turbines and improves their efficiency.

Upon comparing the thermal performance curves of the two types of turbines it can be noted that the throttle governed, full-arc-admission turbine has better efficiency.

Although as compared to the throttle governed, the nozzle controlled partial arcadmission turbine does show a lower net heat rate in the lower load range; whenoperated in constant pressure mode, the full arc admission turbines can also exhibit a better performance in the upper load range with only periodic load drops; by way of

both, better heat rate and energy consumption. Various degrees of hybrid operation(combination of both, constant pressure and variable pressure mode) of both typesfurther improve the thermal performance of each at partial loads also.

The variable pressure mode of operation is best suited for full arc admissionturbines, whereas the partial arc admission turbine operates over the entire loadrange with some what a lower heat rate level. For constant pressure operation, theload changing characteristics of both types of turbines indicate a better ability of fullarc admission turbines to deal with severe load transient conditions, because they exhibit smaller changes in temperatures for a given load change.

Load dependent temperature changes can, however, be minimised by applying hybridpressure mode operation or can be totally eliminated by adopting the variablepressure mode operation.





KORBA SIMULATOR 267

Wetness Loss

The wetness of steam goeson increasing towards thelast stages of a turbine, at a given set of parameters.Condensation of steamcauses wetness or formation of water droplets on blades, whichlose some mechanical

work in throwing off thedrops. Apart from that severe erosion is alsocaused to the blade tips of last stages. Generally, 1%increase in wetnesscauses 1% loss inefficiency

External Losses: Shaft gland leakage.; Journal and thrust bearing; Governor and oilpump.

MONITORING TURBINE PERFORMANCE

Cylinder efficiency Test

By accurately measuring the temperature and pressure of steam before and after HP

and LP cylinder, it is quite easy to determine the respective cylinder efficiency. TheLP cylinder efficiency can't be ascertained as the steam is wet there and exact 'statepoint' can't be located.The cylinder efficiencies do not change appreciably with load,as ratio of blade to steam speed (u/V) remains constant with load. However, due todeteriorating cylinder efficiencies, change in turbine heat rate can be computed withthe following formulae:

HP Cylinder ∆(HR) = {{0.43 (H-h) ∆ (n)%}1/ Kwa} *2.36 Qr/ HRa _ 2.158 Qh/3600}

Where,∆(HR) = % change in heat rate value.

H = Enthalpy at TSV, KJ/Kg. (ref. data)h = Enthaply at HPT exhaust, KJ/Kg. (ref. data)∆n % = % change of efficiency from designed value.KWa = Ref. alternator output, KW Qr = Reheater steam flow (present) Kg/hr.HRa = Reference test heat rate, KJ,/KWHQh = Present steam flow to HP cylinder, Kg/hr.



KORBA SIMULATOR 268

IP Cylinder∆(HR) = ∆n % { 0.928 (H1-H2)* Qr) *1/ KWa *3600 -1}

Common causes of cylinder efficiency deterioration include:Damage to blades caused by debris past the strainers.Damaged seals and glands.Deposition on blades.

Increased roughness of blade surfaces.

The surface roughness affects the HP cylinder maximum, then IP cylinder and thencomes LP cylinder. Larger machines are affected to a lesser extent as compared tosmaller machines.

Turbine Pressure Survey

This is a very useful tool indicating the internal condition of turbine. Following stepsare followed for preparing the pressure survey diagram

i) Choose a pressure scale on Y-axis from zero to any pressure above ESV pressure,say, at rated load.ii) From acceptance test results or design reference, mark off various pressures at

various points of tapping as shown below.iii) Join all points with a straight line.

Basic Pressure survey diagrams & effect of Heaters out of service :2

If at some later date, the pressures are noted at each point while the load is the sameas plotted, as before, the points will lie on the same line if the cylinder condition hasnot deteriorated. But, if the load is lower and the condition of machine is same thepoints will plot on a line lower than the previous. When plotted pressure points areon the optimum pressure line for a particulars load it is indicative of general wear of



KORBA SIMULATOR 269

diaphragm, seals etc. If the line has 'kink', then it indicates some restriction in theturbine. The pressure before the restriction will be higher, after that lower thanoptimum.

LP cylinders are difficult to assess on pressure survey scale, as pressures can't beplotted accurately. Nevertheless, chances of rubbing and wearing are less due toliberal clearances, but there remains a possibility of silica deposits. Hence, LP inlet and bled steam pressure should be checked regularly.

Effects of Internal Restrictions Effects of load changes

Silica can enter the system through reheater leaks during shutdown because of

vacuum built up in the steam space as steam condenses. This can happen especially when vents are not opened prior to pressure decay. Also BFP and feed heaters whenthey are opened for maintenance, silica can enter the system.

EFFECT OF OPERATING PARAMETERS ON CYCLE EFFICIENCY

The complexity of a power station unit offers scope for many parameters to havedeviation from optimum. Fortunately technical expertise and know-how gatheredover the years facilitate ascertaining the causes of efficiency loss due to deviationfrom optimum, by monitoring just a few terminal conditions. They are

a. Turbine backpressure.

b. ESV steam pressure.

c. ESV/RH steam temperature.

d. Amount of attemperation spray.

e. Final feed water temperature.

f. Boiler excess air.



KORBA SIMULATOR 270

g. Combustibles in ash.

h. APH gas outlet temperature.

i. DM water make up rate.

j. Auxiliary power.

k. Unit load.

Turbine Back Pressure

This is the most important parameter that severely affects efficiency of a power plant cycle. It is dependent upon

1. Condenser air tightness.

2. CW inlet temperatures.

3. Condenser tube fouling.

4. Effect of variations of heat transferred.

5. CW flows in condenser.

Generally speaking, improving the backpressure improves the amount of work done by steam, but up to a limit. Because, with increase in certain losses also increases.

Backpressure correction curves Minimum Back press.at different loads

They can be listed as follows:

1. CW pumping power.

2. Leaving/exhaust loss.



KORBA SIMULATOR 271

3. Reduced condensate/feed water temperature.

4. Wetness losses.

The losses mentioned will eventually significantly affect the results. Continuedoperation with reducing backpressure will result in net improvement in heat consumption becoming progressively less until a point is reached where gains equalthe losses. There is no point for further reducing back pressure beyond this.

Loss due to high CW inlet temperature may be due to inefficient cooling tower operation; can be compensated by increasing flow of CW. But the gain in efficiency must be weighted against loss due to increased CW pumping power.

Loss due to incorrect CW flow can be eliminated. If the temperature rise across thecondenser is less, that means more than optimum CW flow. It can be reduced.Excessive CW flow can cause under cooling of the condensate, ultimately loweringthe final condensate temperature.

Loss due to air ingress is entirely preventable and steps must be taken to ascertainair tightness and points of leakages, if any. Remember, 1 mm. thick air sheet has thesame resistance as 17 mm. copper slab.

Deviations in backpressure due to fouling cannot be eliminated thoroughly duringoperation. Off load cleaning of tubes is a must. However, if any increase in frequency of back washing is noted, it should be ensured that chlorination is adequate.

ESV Steam Pressure

On a throttle governed machine the output is proportional to 'after control valve'pressure or first stage pressure. It can be assumed that even if throttle control valvesare 100% open, there is a drop of 5% - 10% in ESV pressure at control valves.

Variation of turbine steam pressure causes

a. The total heat drop to vary, higher pressure causes increased heat drops(at the same inlet temperature conditions).

b. Increasing exhaust wetness at higher pressures.

c. Increased turbine output for a given control valve opening such that 10%increase of pressure will produce 10% extra output.

For more common reheat type machine, variation of ACV (after control/throttle valve)pressures are proportionally dependent on load conditions, such that 50% reductionof load will reduce ATV pressure by 50% as shown in the figure. Ignoring pressuredrops in reheat lines at 100% expansion lines in HP and IP/LP turbine is AB and CDrespectively as shown in the figure. At. 50% output turbine expansion is EF and GHas shown.



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It can be seen that

• HPT enthalpy drop remains same.

• IPT/LPT enthalpy drop becomes smaller in spite of increased IP inlet specificenthalpy because of reduced slope of temperature lines with respect to

consistent slope of condenser pressure line.

Controlling load by sliding pressure operation on the CE boilers supplied by BHEL toNTPC within a + 10% of the rated value may yield some benefit by way of reducedthrottling losses at part load.

This may also have the following disadvantages:

a. Boiler pressure is reduced hence cycle efficiency is very much lower thanoptimum at full load conditions.

b. At very low pressure, at higher loads steam volume is more, which tends toenvelop water in the boiler tubes, leading to film boiling and subsequently overheating of tubes.

Any deviation in turbine inlet pressure can change the steam flow through turbine, because of which stage pressure and extraction pressure will change, changing feed water temperature. The volumetric flow to condenser also changes accordingly.Hence, ramifications of a small pressure change can be seen through out the cycle.CE make Korba Boiler is not designed for Sliding Press. Operation.



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Re-heater Line Pressure Drop:On account of reducing slope of temperature line with respect toconsistent slope of condenser pressureline, the turbine expansion line ABCHI(under ideal 'no pressure drops'conditions) denotes optimum heat dropsacross HP/IP turbines. However a practical steam turbine has about 5% to7% pressure drops in reheat line.Subsequently turbine expansion linesnow become ACCDEFG, which indicatesa far less efficient steam utilisation It must always be ensured that cold reheat NRVs are functioning freely. Opening out along the steam flow.

Also reheat pressures along with HPT exhaust pressure at various load must berecorded for a healthy machine so that the same can be used for comparisons at a future date.

Throttle governing

In modern, large machines the economic rating coincides with the maximum rating. The steam flow is controlled by the degree of opening of the throttle valves, which arelocated in the HP cylinder steam chest. Obviously the up-stream steam pressure at the throttle valves will be constant, irrespective of the turbine load, but the pressureafter the throttle valves will reduce as the valve opening reduces. This will cause theavailable energy per kilogram of steam due to expansion to be reduced, as well as themass flow of steam. This is illustrated for a non-reheat turbine the in fig.

The turbine stop valves conditions are

105 bars and 565oC. At full-load, theloss of steam pressure due to thethrottling effect of the turbine stop andthrottle valves is about 5%. Hence theafter throttle valve (ATV) pressure is,say, 100 bar absolute. The steam does

work in the turbine by expansion until40 m bar backpressure is reached, thestate-point of the steam being

represented by the line AB,representing 80% efficiency. At half-load, the ATV pressure will be half of that at full-load, as shown at C. Theexpansion of the steam is shown fromC to D.

Specific Entropy vs Enthalpy steam state-point lines in throttle governing



KORBA SIMULATOR 274

Similarly, for 25% load, the ATV pressure will be a quarter of full load and theexpansion EF. Notice that the specific enthalpy of the inlet steam remains unalteredfor the range of loads. However, the available energy is reduced significantly as theloading falls, as shown in Table.

Heat drop per Kg of steam at various loads (at 80% efficiency)

Load Enthalpy KJ/Kg Heat drop KJ/Kgat inlet at exhaust

100% 3357 2343 1194 50% 3537 2419 111825 % 3537 495 1042

This reduction of heat drop, coupled with the reduced flow of steam, causes theturbine output to be reduced as the throttle valves close. Notice that the slope of theexpansion line remains the same for all loads, so the efficiency of the expansionremains the same, which is what one would expect from the earlier discussion about cylinder efficiency. On the other hand, it should be realised that throttling incurslosses as the steam pressure and temperature are adversely affected.

Nozzle Governing

Here the first-stage nozzles are divided into a number of groups, sometime more thanten. The steam admitted to each a valve controls group, and each valve is opened inturn as loading is increased as shown in the fig. Consider a four-valve arrangement

where the first valve only is in service from no-load to quarter-load, and at quarter load it is fully open. This is followed by the second half-load, and then valves three tothree-quarter load. Finally, the last permits maximum loading when fully open. Theonly valve operating in the throttling mode is the last one to be brought into service,all the previous ones being wide open, so the losses due to throttling are not so great as with the previous type, so operation is more efficient.

This is illustrated in the fig wherethe conditions are similar except for the governing used. At full-load, the expansion is from A toB, similar to the previousexample. However, at 50% load,only two valves are open, but again a pressure of 50 bar isrequired. This is achieved moreefficiently than before, so the linefor two nozzle operation is shown

from A to C. Thereafter theexpansion is from C to D.Similarly one nozzle operation isshown from A to E, and hencefrom E to F.



KORBA SIMULATOR 275

Nozzle governing differs from throttle governing as follows:

*The turbine efficiency is higher at part-loads because of reduced throttling loss

*The va.lve control gear is more complicated.

*The internal efficiency of throttle and nozzle governed machines can be the same(Represented by slope of the expansion lines on H-S diagram) after the wheel case.

*Because of their improved part-load efficiency, nozzle-governed machines arepreferable where the loading regime involves prolonged operation under theseconditions.

ESV/RH Steam Temperature

Variations in steam temperature results in variations of specific volume of the steamand this result in change of steam flow according to

Fa = Fo*{(Pa *Vo)/ (Po * Va)}1/2

Where F=flow, P= Pressure, o= Optimum condition; V= Sp. volume of steam of ESV a= Actual condition

Other effects for reduced steam temperature for a non-reheat set are:

a. Total energy-reduces hence turbine efficiency is also reduced.

b. Wetness increases at the exhaust of L.P.T. turbine.

c. Change of flow and pressure of steam.

For reheat machines as shown in the figure reduction of main steam temperaturecauses available energy of steam to be reduced causing reduction in efficiency. Also,extra heat is required in reheater to have the same hot reheat temperature.Expansion in IP/LP turbine remains unchanged as long as HRH temperature isconstant:



KORBA SIMULATOR 276

If the reheater temperature is reduced and MSV temperature is constant, IP/LP

turbine output reduces due to less available heat drop, exhaust wetness increasesand heat addition in R/H is reduced. The HPT is not affected.

High temperature yield high heat drops but cause significant reduction in operationlife of high temperature components.

Effect of Inlet Temperature changes

ATV tem eratureoC 570 560 580 570 570

Reheater tem eratureoC 570 570 570 560 580

Exhaust tem eratureoC 29.0 29.0 29.0 29.0 29.0

Exhaust wetness % 14.7 14.7 14.0 15.1 14.1

Heat drop in HPC KJ/Kg 421.8 414.8 428.3 421.3 421.8

Heat drop in R/H KJ/Kg 1407.4 1407.4 1407.4 1394.3 1422.9

Total heat drop 1829.2 1822.2 1835.7 1816.1 1844.7

Note that the effect of reducing the ATV temperature to 560OC is significant withreference to total heat drop even though it only affects the HP cylinder heat drop anddoes not affect the wetness.

Steam Attemperation

Attemperation of steam invariably causes loss of power output and increase in heat

rates. But is not entirely avoidable in modern high capacity boilers.

Especially reheat attemperation should be avoided until absolutely necessary. As far as possible, the reheater steam temperature should be controlled by the burner tilt.

The basic objection to reheat attemperation is that the steam so formed does work only in IP and LP turbines bypassing the HP turbine; hence there is a considerablereduction in cycle efficiency.



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Feed Water Temperature

The feed water temperature at boiler inlet is another main important factor determining cycle efficiency. It is mainly dependent on

a. Heater performance.

a. Feed flow through heaters.

c. Terminal Temperature difference (outlet feed water temperature steam

saturation temperature at the extraction pressure).

d. Bled steam pipe pressure drop.

e. Steam temperature at heater inlet.

One degree centigrade rise in TTD (Terminal Temperature Difference) leads to 0.027%drop in efficiency. A bad heater performance can be attributed to the following:

- Air blanketing

- Waterside contamination.

- Steam side contamination.

- Drainage defects.

In order to avoid this factor, the boiler must be operated at constant pressure, sothat feed flow remains optimum. Proper and frequent air venting of heaters,prevention of oxygen ingress and thus exfoliation i.e. flaking of tubes causingsubsequent choking and TTD increase; and maintaining of proper pH value inCondenser should be practiced.

Boiler Excess Air

Boiler combustion efficiency largely depends upon supplying adequate quantity of excess air, too much of which results in increased dry flue gas losses and flameinstability, leading to poor efficiency and reliability of operation.

Too much of excess air can be through ingress points such as

a. Suction milling plants.

b. Expansion joints on ducts.

c. Openings like peepholes.

d. Ash hopper doors open.

e. Ash hopper seals.

These leakages put extra burden on ID Fans and limitations on unit loading. Theleakages after air pre-heaters do not affect the efficiency significantly.



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Air Pre-heaters Gas Outlet Temperatures

Low air pre-heater gas outlet temperature may be due to the following:

a. Light up of cold boiler.

b. Excessive air leakage in the APHs (damaged seals).

c. Very high wind box pressure.

d. Inadequate air supply in boiler.

e. Poor fuel quality.

f. Air pre-heater sooting.

High APH gas temperature may be due to

a. APH sooting or ineffective soot blowing.

b. Holed and torn element at cold ends, due to corrosion.

c. Sooting of boiler.

d. Excessive air supply to boiler.

e. Film boiling due to poor circulation in boiler.

f. Low feed water temperature.

g. Poor milling and longer burn-off times of coal.

h. Use of higher elevation burners at low loads.

i. Excessive firing.

j. Air ingress into furnace.

Generally speaking a 20 OC rise in final gas temperature causes a drop of 1% inefficiency.

DM Water Make-up Rate DM water make up is a must in modern power station due to certain problems which

warrant invariable blow-downs soot-blowing etc. There are four usual sources of loss

Soot blowingSoot blowing must be done selectively and only when required. Frequency of soot

blowing is also dependent upon coal quality and furnace temperature and firingconfiguration.

Boiler Blow down During initial start-ups it is unavoidable, hence very conditions that lead to outagesmust be avoided. On load condition it is a loss of DM water and useful heat. So allattempts should be taken to keep dust ingress into the boiler water to a minimum,and to have good boiler water chemistry.

A good maintenance schedule to prevent any leakage or passing of valves must be



KORBA SIMULATOR 279

envisaged. The operators must take due care to avoid any undesirable overflowing of DM storage tank, deaerator, drum etc.

Auxiliary Power Consumption These are the following factors contributing to excessive auxiliary power consumption.

Machine Loading As the unit load is decreased, percentage aux. power rises as shown in the fig. Incommon practice, operator must have three mills running at full load rather thanfour mills running at part capacity. CW pump flow must be controlled in accordance

with optimum backpressure requirements so that benefits from running equipmentsshould be more than the cost of running them.

Variable Speed Drives Power consumption of variable speed drives varies as the cube on the speed. Hence,precaution must be taken to affect only the minimum speed, which will do the job.

For example, BFP discharge should be maintained to give the lowest requireddifferential pressure across feed water station at any load.

Parallel Operation of Auxiliaries Two pumps in parallel do not give twice the output of one pump. In fact it is quitecommon to derive only marginal increase by running second pump and adds tohigher auxiliary power consumption, which reduces overall station efficiency.

Milling Plant Power Consumption Attempts should be made to run the existing mills at full load rather than startingnew mills to be run at part load. Moreover, classifier settings should be regularly checked to give just the required fineness of coal, not more. More fines puts extra

burden on the pulverisers.

Mill outlet temperatures must be maintained at the rated value. Low temperatureputs a limitation on loading of the mill. High mill reject operation puts extra burdenon PA Fans and also it is a loss in terms of loss of some pulverized coal from the mill.



KORBA SIMULATOR 280

Unit Loading

The efficiency of a unit improves as the loading improves. So, all out attempts must be made to ensure, there is no part loading or outages to maintain a high load factor,and shortfalls should be kept to minimum. Because fixed heat has to be sustained at all loads. It is important to generate every possible megawatt while on high load. Oneimportant way of preventing short-falls, is to ensure that boiler firing must becontrolled to control boiler pressure not, by varying load on T/G.

CONDENSER PERFORMANCE

Even a small worsening of backpressure is very expensive in terms of extra heat required for a given output. To illustrate this for a 200MW station, if the

backpressure worsened by just 100 mm (Hg.), the resulting extra fuel cost would beabout Rs. 6,000,000/- per annum. Hence condenser performance is undoubtedly themost important operating parameter on a unit. So the factors affecting backpressuremust be clearly recognised so that effective remedial measures can be taken oncethey are detected.

It is evident that work obtained from theturbine increases if backpressure isreduced. So it is always desirable tooperate at minimum economic

backpressure i.e. condenser temperature isas low as possible. If the condensingsurfaces were infinitely large, condensingtemperature would equal the CW inlet temperature. However there is a practicallimit and in practice the average condenser temperature is 15OC above the inlet CW temperature, but even then the size of condensing plant is considerable. For example, on 660 MW unit the condenser may have 20000 x 25 mm diameter tubes,each 20m long. Reason for this is apparent

when we realise that for generated output of 660 MW, 780 MW is surrendered to thecondenser.

Determination of deviation

The manufacturer supplies various performance curves for the condensing plant, which should be verified by test as soon as possible. Two important relationshipmust be established - load vs. CW temperature rise and load vs. terminaltemperature difference.



KORBA SIMULATOR 281

Knowledge of these optimum values is basic to much condenser performance.Importance of CW temperature is obvious but TTD (Terminal Temperature Difference)needs a bit of understanding.

To make heat flow from condensing steam to cooling water requires sometemperature gradient, steam temperature being higher than that of cooling water.Excellent heat transfer requires small gradient whereas bad heat conduction requiresa large gradient. Hence TTD is a measure of effectiveness of heat transfer.

Condenser condition graph

As has been explained the backpressure in condenser depends mainly on-

- Variation of CW inlet temperature

- Variation of CW flow

- Interference with heat transfer

Effect of these factors can be illustrated with the help of condenser condition graphshown in the adjoining fig. For example optimum and actual conditions for a



KORBA SIMULATOR 282

condenser are listed below.

Parameter Optimum Actual

- CW inlet temp. oC 16.5 20.0

- CW outlet temp. oC 25.0 26.0

- CW temp. rise oC 8.5 6.0

- Saturated steam 30.5 36.0temperaturecorresponding to

back pressure oC

- TTD. oC 5.5 10.0

- Back pressure mbar 43.7 59.4

To determine the contribution of each of the main factor to the total deviation in backpressure from optimum we can use condenser condition graph.

Contribution due to CW inlet Temperature

Plot a line vertically from actual CW inlet temperature point up to the optimum CW rise line and then horizontally to the optimum TTD. From this point drop a verticalline to intercept the saturation temperature line at 34OC with corresponding

backpressure of 53.2 mbar. So the backpressure deviation due to CW inlet temperature alone is (53.2 - 43.7) = 9.5 mbar.

Contribution due to incorrect CW flow

In the list it can be seen that actual rise is less, hence the CW flow must be morethan optimum. To determine its component affecting backpressure, plot a line fromactual CW inlet to actual CW rise, then to optimum TTD line, finally downward to cut saturated steam temperature line at 31.5OC. Equivalent backpressure is 46.2 mbar.

Therefore, the pressure deviation due to high flow is 46.2 - 53.2 = 7 mbar. High CW flow improves the backpressure by 7 mbar.

Contribution due to heat transfer

Deduct from actual backpressure of 59.4 the backpressure of 46.2 (= 13.2 mbar).

This is the deviation caused by high TTD.

Shift Monitoring

For this purpose, the required curves are CW temperature rise v/s. load, optimum TTD v/s. load (both have been illustrated earlier) and target back pressure for various CW inlet temperature v/s, load.



KORBA SIMULATOR 283

Once per shift during the period when load is steady, backpressure on the unit should be monitored to determine backpressure deviations and their removal. A standard form can be used as shown below (typical for a 500 MW set).

The air suction temperature is required because it is an indication of air ingress tothe condenser. For example if there were no air ingress, air suction temperature of

vacuum pump inlet would be 4-5oC lower than the saturated steam temperature. Air ingress causes the temperature or the suction of vacuum pump to fall further as per 'Dalton's Law of Partial Pressure. The total pressure of inlet to the pump is made upof partial pressure of air and water vapour. But the temperature of mixture is dueonly to the water vapour. Consequently as the vapour quantity is reduced, so is thetemperature.

The effect of internal tube deposits and the effect of air blanketing on outside of tubes are indistinguishable in their effect on TTD. Hence, when the air ingress isascertained and rectified, then any deviation in back pressure ascribed in air/dirty tubes will be due only to the dirty tubes and hence a decision can be taken to cleandirty tubes.

SPOT BACK PRESSURE CHECK

UNIT NO. DATE

1. Actual back pressure mbar 52.3

2. Saturated steam temperature oC 33.7

3. CW inlet temperature oC 17.9

4. CW outlet temperature oC 26.8

5. Exhaust steam temperature o

C

33.7

6. Condensate temperature oC 34.9

7. Air suction temperature oC 24.9

8. CW outlet valve position % 55%

9. Target back pressure mbar 48.4

10. Optimum CW temp rise oC 9.0

11. Optimum TTD oC 5.2

12. Back pressure due to CW inlet

= (3) + (10) + (11) mbar

47.8

13. Back pressure due to CW flow = (4) + (11)

mbar 47.5

14. Variation due to CW inlet temperature= (12) - (9)

mbar -0.6



KORBA SIMULATOR 284

15. Variation due to CW flow = (13) - (12) mbar -0.3

16. Variation due to air/dirty tubes= (10 - (13)

mbar 4.8

17. BP variation = (1) - (12) mbar 4.5

18. No of air pumps in service

FEED WATER HEATER PERFORMANCE

In modern power stations direct and indirect feed water heaters are invariably in useto enhance the unit performance. Usually the number of feed water heaters providedon a power plant depends on the trade off between the full costs saved by a particular no of heaters balanced against the annual fixed charge on heater investment for minimum generating cost. Economically justifiable maximum number of heaters on a plant is ten. It is common to find 6-7 feed water heaters on power generating units in our country.

Heat transfer to feed water in non-contact type heater is achieved by the surrender of latent heat of steam primarily because heat recovery by de-superheating and draincooling is about 6%-8% of the total latent heat recovered by feed water.

The two important parameters used in assessing heater performance are TTD(Terminal Temperature Difference) and Drain Approach. TTD is defined as thedifference between saturation temperature of extraction steam and feed water temperature after the heater. Where as drain TTD or drain approach is defined asdifference between feed water temperature at inlet to heater and drain outlet temperature after the heater.

Factor Causing Deterioration of Heater Performance

It is not sufficient to just measure final feed water temperature to determine if theheaters are operating efficiently, because trouble at one heater can be compensatedfor by other heaters doing more work. This causes bled steam flow to heaters, to alter and thus affect the work done. So cycle efficiency is altered. Therefore, it isnecessary to check individual heaters from time to time, checking particularly the

TTD and drain approach as a general rule, preferably twice in a year, heaters(individually) investigation must be carried out.

Deterioration of heater performance occurs on account of one or more reasons asshown below:

• Air accumulation

• Steam side fouling

• Water side fouling

• Drainage defects.



KORBA SIMULATOR 285

Air Accumulation

Air is a superb thermal insulator, hence, highly undesirable. Proper vents aregenerally provided on heaters (to condenser) body to prevent accumulation of air. Air can get into heaters when extraction pressure in them is reduced below atmospherei.e. wherever the machine load is reduced or machine is off-loaded.

Hence, the vents of sub-atmospheric heaters must be permanently open while thoseon the rest should be open long enough to vent them thoroughly while machinecomes on load and periodically thereafter. It needs to be emphasised that steam(generally 0.5%) passing through the vents is a loss to the system.

Accumulation of air manifests itself in the following:

• Reduced drain approach.

• Increased TTD

• Elevation of steam to heater temperature.

• Reduced temperature rise of feed water heater.Steam Side Fouling

Cupro-nickel (70/30) alloys was generally used in the past. However, it was foundthat this material exfoliates (i.e. it flakes off like a dead skin). Due to this the space

between the tubes in the cluster becomes blocked with debris and heat transfer isprogressively reduced. It has been practically established in one case that TTD rosefrom 4 OC to 14 OC continuously over a period of 7 years.

Alternatively now 90/10 cupro-nickel, Monel metal, mild steel etc. are used as tubematerial to reduce problems of exfoliation.

The effect of exfoliation include:

• Progressive increase of TTD.

• Drain temperature of unaffected.

• Reduced feed temperature rise

• Eventual tube failures due to weakening

• Accumulation of debris in heater shell.

When the heater is out of service, it is important that there is no standing water at tubes such as those in the drain cooling section to prevent corrosion. Also, oxygenpercentage must be kept under recommended units to keep the rate of corrosion to

minimum.

Water Side Fouling

Most common cause of waterside fouling is oil. Oil can get into the system fromleaking bearings and important gland seals of LP turbine. Deposition of them occursin HP heaters affecting them all but being worst at the highest-pressure heater.

Thermal manifestations of troubles are similar to those for exfoliation except that the



KORBA SIMULATOR 286

onset of increasing TTD is usually sudden and rate of deterioration is rapid.

Slightly fouled tubes can be chemically cleaned. In the worst cases high pressure water jetting may be required.

Drainage Defects

Apart from obvious problems such as passing valves etc. the usual troubles are dueto

a. Damaged flash box internals

b. Reduced/enlarged orifice opening

c. Heater drains pump defects.

A typical flash box has an orifice followed by a diffuser, which diverts the flashingdrain downward on to water reservoir. If the diffuser disintegrates, its pieces cancreate obstruction in pipes and cause flooding. Further flashing steam/water may

cause erosion of flash box internals.

Reduction due to fouling, of the orifices is very common. It results in drain blockingup to previous flash box resulting in flooding and some water droplets are carriedinto flash steam to the bled steam pipe. Heat is taken up by the water and steam toheater temperature drops.

Conversely, orifice size can increase due to erosion and can reduce differentialpressure from inlet to outlet. The orifice plate does not alter the bled steam pressureat upstream and downstream heater so the reduced differentials achieved by lowering the water level in upstream heater. Sometimes high-pressure heater draincascade to a drain pump which pump it to deaerator. At deaerator pressure the

saturation temperature is of the order of 160OC approx. and if the pump suctionhead is not sufficient then water can flash in the pump itself interfering with thepumping. This causes heater level to rise; consequently drain to condenser opens upand results in lowering heater efficiency.

Effect of Heater out of Fouling

Fouled heater gives increased TTD, as is already evident i.e. lower feed water out temperature. This relatively cold water goes to the next heater, which has to work harder to maintain its TTD and draws more steam in the process. This steam is not available for doing work hence cycle efficiency is lost. Increased steam flow alsocauses mechanical damage to the nearing tube bundles because of increased velocity

and mass flow.

Effect of Heater out of Service

Anyone heater being out of service considerably affects the cycle efficiency. Feed water outlet is lowered and the next heater has to do extra work as is explainedearlier. If the final (highest pressure) heater is taken out the feed water to boiler is at lower temperature and has to have extra heat given to it in the boiler. Further bled



KORBA SIMULATOR 287

steam, which is now not being bled, can do extra work in the turbine, significantly improving the unit output although at the expense of lower thermal efficiency.(Incremental heat rate of the additional MWs is very high hence this is a very expensive method of generation).

As a general guide to the effect of having a heater out of service, the followingefficiency reductions may be used.

TSV pressure Up to 100 bar over 100 bar

L.P. Heater 0.5% 0.5%

Last HPH 1.3% 1.5%

Monitoring of Feed Water System

Feed heater surveys can be conducted every six months to detect any early deterioration of heater performance. Operations staff must keep a routine check of the performance on a shift-to shift basis noting down final FW temperature, heater

TTD and steam-to heater temperature.

Feed Water Chemistry (High Oxygen Regime)

Magnetic layer, against corrosion by feed water, protects low alloy/mild steel tubes.

At temperature between 140OC and 200

OC magnetic layer is more porous than it

would be if it is formed under higher temperature. Since it has slight solubility it can be removed by turbulent/ past feed flows in heaters. A fresh layer is formed anderoded and go on causing metal loss at bends and bifurcations.

To deal with these problems, 20-150 micro gm. per litre of oxygen is injected intofeed water before heater drain. This oxygen causes iron oxide to be deposited as

hematite. To save this layer of hematite feed water should have low anion content (low chlorides, sulphate), or i.e. should have low after cation conductivity, usually

below 20 micro siemens /m. This can be achieved by good condensate polishing.



KORBA SIMULATOR 288

SIMULATEDMALFUNCTION LIST



KORBA SIMULATOR 289



KORBA SIMULATOR 290

LIST OF SIMULATED MALFUNCTIONS

BOILER SYSTEM MALFUNCTIONS

B01 Pulveriser A to F choking or loading up

B02 Coal Feeder A to F trip

B03 Pulveriser A to F tripB04 Pulveriser A to F Fire

B05 Pulveriser A to F reduced capacity

B06 Coal Feeder A to F fail to deliver coal

B07 Water Wall Tube leakage

B08 A or B ID Fan trip

B09 A or B FD Fan trip

B10 A or B PA Fan trip

B11 A or B I D Fan out board bearing temp. high

B12 A or B FD Fan outboard bearing temp high

B13 A or B PA Fan outboard bearing vibration high

B14 A or B I D Fan outboard bearing vibration high

B15 Flame Scanner Elevation AB, CD or EF shows flame continuously

B16 Fuel Flow run back to less than demand

B17 Drum Steam Pressure Transmitter fails low

B18 Low Drum level

B19 RH Tube leakage

B20 Secondary SH Tube leakage

B21 Electromatic Safety Valve fails open

B22 APH Primary Air Output Damper AD-20 fails closedB23 Pulveriser A to F tempering Air Damper froze

B24 Plugged Air Heater

B25 Aux Air Dampers adjacent to coal elevation faulty modulating

B26 FSSS AC Supply fail

B27 FD Fan A or B Discharge Damper AD-3 / AD-4 fails closed

B28 Aux Air Dampers not modulating

B29 Drum Emergency blow-down Valve B-82 or B-83 fails open

B30 Left side Furnace Pressure low

B31 Burner Tilt fails high

B32 HO Header Pressure low

B33 HO Trip Valve fails closed

B34 HO Temperature low

B35 HO Supply Header Pressure low

B36 Aux PRDS Valve fails closed



KORBA SIMULATOR 291

B37 A or B APH main drive motor trip

B38 Firing Rate limited

B39 Airflow run back to less than demand

B40 I D Fan A or B Inlet Vane froze

B41 High Drum Level

B42 High SH tube metal tempB43 Boiler Water Silica concentration high

B44 Throttle Pressure Transmitter fail

B45 Loss of Seal Air to Pulveriser A to F

B46 Airflow less than 30%

B47 Airflow more than 40% during start-up

B48 All Pulverisers trip

B49 Boiler Purge Timer failure

B50 Flame Scanner failure, elevation AB, BC, DE and EF

B51 Ignitor pair 1 and 3 of elevation AB, CD and EF fail Off

B52 Elevation AB Oil Gun # 1 Scavenging Valve stuck open

B53 No Start Permissive for Pulverisers A to F

B54 Pulveriser A to F Primary Airflow Temperature Thermocouple fail

B55 Pulveriser A to F Hot Air Gate fails closed

B56 Pulveriser A to F motor stator temperature high

B57 Pulveriser A to F Airflow feedback offset 25% high

B58 Pulveriser A to F fails to start

B59 Loss of Coal Flow Indication of Feeders A to F

B60 Loss of Drum Level Transmitter

B61 Furnace walls badly slagged

B62 Abnormal Ash build-up on RH pendant

B63 Ash build up in Economiser

B64 PA Header Pressure Controller malfunction

B65 Furnace Pressure Controller A or B malfunction

B66 Purge Ready condition cannot be met

B67 Air Heater A or B fire

B68 Aux Air Damper control power failure

B69 Burner Tilt position difference

B70 ACS Power Supply failureB71 Boiler Master Controller failure

B72 Economiser Tube leakage

B73 A or B SH Attemperation Spray Block Valves fail closed

B74 A or B RH Spray Valve fails

B75 Failure of Final RH Temperature Controller



KORBA SIMULATOR 292

B76 SH outlet steam temperature swinging

B77 RH outlet steam temperature swinging

ELECTRICAL SYSTEM MALFUNCTIONS E01 Stator Cooling Water tube leakage

E02 Hydrogen Cooler tube leakage

E03 Loss of Hydrogen Seal Oil pressure

E04 Generator Hydrogen leakage

E05 Generator Cold Gas temperature high

E06 Low Stator Cooling water flow

E07 Loss of Outside Power to buses 1A or 1B

E08 Generator Trip

E09 Generator Auto Voltage Regulator failure

E10 Grid Frequency drops down to 49.5 Hz

E11 System Voltage drops low

E12 Loss of Generator Excitation

E13 Unequal Generator Phase Loading

E14 Loss of 220V DC bus to FSSS

E15 Loss of 415 V AC Bus

E16 Loss of Normal Power to Emergency Bus

E17 Megawatt Transducer fails

E18 Low Stator Water Resistance

E19 Loss of one Hydrogen Cooler

E20 Generator Bearing # 1 babbit temperature

E21 High Stator Cooling Water Temperature

E22 Seal Oil leakage into the generator

E23 Auto Synchroniser failure

E24 Generator Seal Oil temperature high

E25 Main Power Transformer oil temperature high

E26 UAT A or B failure

E27 Loss of Emergency Supply Power

E28 Generator Auto Voltage Regulator oscillatingE29 DC Seal Oil Pump fails to start

E30 Stator Cooling Water Pump A or B trip

E31 220V DC Bus fuse blown



KORBA SIMULATOR 293

FEED WATER SYSTEM MALFUNCTIONS

F01 Loss of CW Pump 1-3

F02 HPH-6 Extraction Valve fails closed

F03 LPH-3 tube leakage

F04 HPH-6 tube leakage

F05 HPH-6 alternate drain valve fails openF06 HPH-6 normal drain fails closed

F07 HP heaters Group Bypass Valve fails open

F08 BFP A-C Re-circulation Valve fails closed

F09 BFP A-C Speed Controller failure

F10 Fluctuating FW Control Valve

F11 One FW Regulating Valve fails open

F12 BFP A-C loss of Oil Pressure

F13 BFP A-C high Bearing Vibration

F14 BFP A-C loss of Suction

F15 BFP A-C Re-circulation Valve fails open

F16 Condensate Re-circulation Valve MC-33 fails open

F17 DA Overflow Valve failure

F18 DA Level Control Valve MC-41 fails open

F19 DA Extraction/Pegging Steam Valves AS-62/ES-7 goes closed

F20 DA level transmitter used for ACS, freezes at present level position

F21 Condensate Surge Tank low level switch (DC 43) fails

F22 Hot Well level high

F23 Hot Well level transmitter failure

F24 Condenser Tube leakage

F25 Condenser Air leakage

F26 CEP A or B trip

F27 LPH-3 Extraction Steam Valve fails closed

F28 BFP A-C trip

F29 BFP A-C Hydro coupling Oil temperature high

F30 LPH-3 Normal Drain level controller failure

F31 DA Pressure Controller failure

F32 CW Differential Pressure high

F33 HPH-5 Extraction Valve fail to close on demandF34 Condensate Re-circulation Valve fails closed

F35 HPH-5 Normal Drain Valve fails closed



KORBA SIMULATOR 294

TURBINE SYSTEM MALFUNCTIONS

T01 Turbine AOP A or B trips

T02 Low Secondary Oil pressure to Intercept Control Valve

T03 Gland Steam Condenser tube leakage

T04 Loss of Gland Sealing Steam

T05 Gland Steam Pressure high T06 Emergency Stop Valve # 2 fails closed

T07 Intercept Stop Valve # 1 fails closed

T08 Turbine Control Valve malfunction

T09 Loss of Exhaust Hood Spray

T10 Turbine Shaft Oil Pump fails

T11 Low MOT level

T12 Turbine Bearing Vibration high

T13 ATRS Sub Group Control Turbine failure

T14 ATRS Sub Loop Control Drains failure

T15 Loss of TSI Power

T16 Broken last stage turbine blade

T17 Main Turbine EHG control fails high

T18 Main Turbine Thrust Bearing temp signal monitor fails high

T19 Turbine Axial Shift high

T20 Turbine Over Speed

T21 Main Turbine Lub Oil Cooler cooling capacity reduced

T22 Barring Gear Valve stuck closed

T23 HPT Differential Expansion high

T24 Turbine EOP fails to auto start

T25 Condenser Back Pressure high

T26 Turbine Thrust Bearing Trip Device faulty

T27 Seat Drain Valve before Emergency Stop Valve will not open

T28 Loss of 415 V AC to turbine EHG system

T29 Turbine Initial Pressure Limiter (IPL) transmitter fails low

T30 Turbine trip

T31 HP Bypass Valve fails open

T32 LP Bypass Spray Valve fails closed

T33 Water in turbine Inlet Steam T34 Turbine Stress Evaluator failure

T35 LP Bypass fails to open on demand

T36 HP Bypass fails to open on demand

T37 Turbine Lub Oil Pressure controller failure



KORBA SIMULATOR 295

T38 Turbine Lub Oil Pressure Low trip device faulty

T39 ATRS Control Power failure

T40 ATRS Sub Group Control fails

T41 Low Vacuum Trip Device fails to function

T42 Plugged Oil Line disarms Trip Devices

MISCELLANEOUS SYSTEM MALFUNCTIONS

M01 Loss of Station Air Pressure

M02 Loss of Instrument Air Pressure

M03 Aux Cooling Water Pump Motor A or B trips

M04 Loss of Aux Steam

M05 Stuck Water wall Soot Blower (B-8)

M06 APH A or B Cold End temperature low

M07 Loss of Gland Steam Vapour Extractors

M08 Loss of MOT Vapour Extractor A or B

M09 Scanner Air Fan A or B trips

M10 UPS Power failure

M11 Loss of Soot blowing steam

M12 Retractable Soot blower (R-4) failure

M13 APH Air Motor A or B fails to auto start

M14 Hydrazine BD Valve's CRH temperature interlock bypassed

X01 HP Bypass BD Valve’s CRH temperature interlock bypassed

X02 Starting Device frozen

X03 Mill A trip

X04 Mill B trip

X05 Mill C trip

X06 Mill D trip

X07 Mill E trip

X11 FD Fan-B trip



KORBA SIMULATOR 296

APPENDIX



KORBA SIMULATOR 297

APPENDIX

TITLE

1. Load Vs Superheater outlet Pressure 327

2. Boiler Load Vs Airflow 328

3. Wind box to Furnace DP Vs Load 328

4. Load Vs Superheater and Reheater Temperature & Spray 329

5. Deaerator Pressure Vs Load 329

6. Drum Pressure change during start-up and shutdown 330

7. Boiler start-up after 250 hours shutdown 331




11. Turbine start-up curves 335-345



KORBA SIMULATOR 298

ASSUMING SUITABLE PRESSURE DROP IN THE MS LINEFOR THE VARYING FLOW CONDITIONS

LOAD Vs SUPER HEATER OUTLET PRESSURE(PREDICTED)



KORBA SIMULATOR 299

WIND BOX TO FURNACE DIFFERENTIAL Vs LOAD



KORBA SIMULATOR 300

LOAD Vs SUPERHEATER AND REHEATER TEMPERATURE

DEAERATOR PRESSURE Vs LOAD CURVE



KORBA SIMULATOR 301

MAXIMUM ALLOWABLE RATE OF PRESSURE CHANGE

FOR NORMAL START-UPS AND SHUTDOWNS



KORBA SIMULATOR 302

BOILER START-UP CURVES AFTER 250 HOURS SHUTDOWN

NOTE:

Aux steam is available from external source

Steam temperature downstream of HP Bypass

need not be regulated by spray until the MS Temp is

above 300OC. Then HP BP downstream temp may

be regulated to 230OC.

The Deaerator drawl from CRH is expected to cut in

after synchronisation and at least 20% loading is done.

HP Heaters from CRH may cut in afterwards at 30%load.

SH Spray need not be used for controlling SH outlet

temp until the boiler flow is at least 160 T/H. SH & RH

temp may be regulated and allowed to raise along

the suggested curve at higher loads.



KORBA SIMULATOR 303


NOTE: The metal temp anticipated: HP Casing: 140OC

ST Valve: 50OC

Boiler : Ambient.

Aux steam is available from external source.


need not be regulated until MS temp is above 300

OC. Then this may be regulated to 230 OC.

The Deaerator drawl from CRH is expected to cut in

after synchronisation and at least 20% loading is

done. HP Heaters from CRH may cut in afterwards at

30% load.

SH Spray need not be used until the boiler flow is at

least 160 T/H. SH & RH temp may be regulated and

allowed to raise along the suggested curve at higher

loads.



KORBA SIMULATOR 304


NOTE: The metal temp anticipated: HP Casing: 350OC

ST Valve: 210 OC.

Steam temperature downstream of HP Bypass need

not be regulated until 90 T/H bypass flow is established.Afterwards this may be regulated to 260 OC.

Only Deaerator steam is extracted from CRH. HP

Heaters are anticipated to be put into service only

after synchronisation.

SH Spray need not be used until the boiler flow is

at least 120 T/H.


Deaerator is to be kept pegged at 140 OC

minimum before firing the unit.

Reheater temp control by spray may be adopted

if required, after HP bypass closes.



KORBA SIMULATOR 305


NOTE:

The metal temp anticipated: HP Casing: 465OC

ST Valve: 410OC.


Deaerator is to be kept pegged at 140 OC

minimum before firing the unit.


need not be regulated until 50 T/H bypass flow is

established.

Full vacuum should be available before firing.

SH Spray need not be used for controlling SH

outlet temp until the boiler flow is at least 160 T/H. SH

& RH temp may be regulated and allowed to raisealong the suggested curve at higher loads.

Turbine can be loaded along the dotted line i.e.

21 MW/Minute. For this, the boiler should be at rated

parameters before rolling using HP and LP bypass.



KORBA SIMULATOR 306

TURBINE START-UP CURVES

Warming-up and Starting the Turbine Temperature Criteria

Fig: 1 STEAM WITH 50O SUPERHEAT



KORBA SIMULATOR 307

Fig: 2 RECOMMENDED MINIMUM CURVE (CURVE-A) ANDMAXIMUM (CURVE-B) MAIN STEAM TEMPERATURE AHEAD

OF TURBINE WHEN OPENING THE MAIN STOP VALVES.



KORBA SIMULATOR 308

Fig: 3 ALLOWABLE MAXIMUM MAIN STEAM PRESSURE AHEAD OF TURBINE WHEN OPENING THE MAIN STEAM STOP

VALVES.



KORBA SIMULATOR 309

Fig: 4 RECOMMENDED MINIMUM MAIN STEAM TEMPERATURE AHEAD OF TURBINE BEFORE OPENING THE

MAIN CONTROL VALVES



KORBA SIMULATOR 310

Fig: 5 RECOMMENDED MINIMUM REHEAT TEMPERATURE AHEAD OF IP TURBINE BEFORE OPENING THE REHEAT

CONTROL VALVES



KORBA SIMULATOR 311

Fig: 6 RECOMMENDED MAXIMUM MAIN STEAM TEMPERATURE AHEAD OF TURBINE BEFORE THE TURBINE

IS BROUGHT TO RATED SPEED



KORBA SIMULATOR 312

Fig: 7 RECOMMENDED MAXIMUM MAIN REHEAT TEMPERATURE BEFORE TURBINE IS LOADED



KORBA SIMULATOR 313



KORBA SIMULATOR 314



KORBA SIMULATOR 315



Documents

200MW Trainig Simulator Volume 2