LIGHT UP CHECK POINTS

BEFORE LIGHT UP ACTIVITIES

BOILER SIDE

• MAN ,MATERIAL REMOVED AND BOILER IS READY FOR LIGHT UP.
  

Water-chemistry: 500 MW

Recommended Parameter Values
1. Boiler Water – pH = 9.1-9.4
2. Boiler Water – Specific Conductivity < 20.0 μs/cm
3. Boiler Water – Silica < 100 ppb
4. Boiler Water - Phosphate = 1-2 ppm
5. Boiler Water - Chloride < 0.5 ppm

Check List (Light-Up)

Unit:

Date:

Switchyard Breaker arrangement: Rihand

Stage-I

GT#1  à 1-52  Main (GCB to Bus Bar-1) à 2-52 (Tie-GCB to bus Bar-2) à 3-52(IBT-1 i/c)

GT#2 à 7-52Main (GCB to Bus Bar-2) à 8-52((Tie-GCB to bus Bar-1)

Bus bar-1 à 4-52 (H1) à 5-52(Tie H1-S2) à 6-52(S2) à Bus Bar-2

Bus bar-2 à 10-52 (S1) à 11-52(Tie S1-H2) à 12-52(H2) à Bus Bar-1

Bus-1  ß13-52(Bus-coupler-1) à Bus-3

Bus-2  ß14-52(Bus-coupler-2) à Bus-4

Turbine Governing system

Key Points

Ø  Governing- Regulation of Turbine Speed under No Load and Varying Load

Ø  Others Works: CV Actuation/ Initial Run-up & Synchronization/ Load Variation to meet Grid Freq

Ø  500 MW KWU: Throttle Governed Machine

Ø  2 Governors , EHC and HG connected in Parallel: Only One at a time through Hyd Minimum slection

Ø  CVs Open according to Secondary oil Pressure

Ø  Between 100 MW  to 525 MW , Load variation done by HPCV throttling

Important Procedures

Vacuum Pulling : Procedure:

Ø  Close RH Vents, CRH, HRH UFT drains

Ø  Close Vacuum Breaker

Ø  Open 8.5 m steam Manual valve full Both (100%), Temp> 250 Deg ( Open

Ø  Start GSC Exhauster Fan

Ø  Start Both Vacuum pumps ( Casing Empty, Receiver tank Level adeq)

Ø  At -0.2 ksc charge steam gradually ( lower Controller from 50% à 0 %)

Ø  Build Vacuum upto -0.9 ksc

Hydrogen Purging

Ø  SLC AS SOP Off, SLC DC SOP Off, SLC H2 SOP Off

Ø  Suppy of DC SOP Off

Ø  Start one AC SOP ( DP=1.5 ksc)

Ø  Dew Point Air=<-10 Deg, clearance from Chemist

Ø  H2 (Isolated Position), CO2(Isolated Position), Air Inlet(Open), Casing vent ( Closed)

Ø  Fill and Pressurise upto 0.5 ksc

Cold start-up

Points to Remember

Ø  maximum of HP casing and HP shaft is less than 150°C(more than 5 days)

Ø  It requires soaking of Turbine at 360 rpm with steam(40ksc,360 Deg)

Ø  An upper limit of 200° C/hr. saturation temp gradients can be allowed, i.e. approximately the boiler pressure can be brought to 20 Kg/ Cm² within an hour of cold start up

Ø  But actual temp gradient is limited by the thick walled Y piece provided in the main steam and HRH lines

Ø  maximum differential temp allowed between inner (98%) and mid wall temp (50%) is ±40°C

Ø  Start only two CC pumps in order to minimize flashing in down comers (and subsequent vibration) when the boiler water is in the range of 85° to 125° C

IBT Outage

Consequences on Stage-2 ( Station Transformer Tripped)

Ø  132 KV Switchyard dead results in tripping of -Station Transformers, Construction Transformer, Misc Transformer

Ø  All colony power( Lighting,Water supply) will get interrupted

Ø  Power Supply to DM Plant, HFO Pump house, PTCW Pump house, Offsite Board, ADPH,

Ø  Following Board will get dead:

§  OBA,OBB,OBC,OBD (11 KV station Board)

§  OCA,OCB (3.3 KV Station aux Board), ADPH MCC, CHP Transformers

§  DMPT, CWST, WTPT,BTST,ODA,ODB(Station Service), ODC(FW Pump House),ODD ( Offsite ): 3.3 KV

§  OQA,OQB(St. Serv),3SA,4SA(Air Washer MCC),3TA,4TA(Unit Ventilation MCC),OTA(HVAC ) : 415 V

§  OSA(SW MCC), OTB(Serv Bldg Ventilation MCC), FOPH : 415 V

Main Equipments Tripped

Instrument Air supply Failure

Reasons of  Failure:

Ø  Failure of control supply of  compressor

Ø  Loss of Cooling Water (SG ECW Pump Trip)

Ø  Massive leakage in  IA supply Header

Ø  One Unit Under Overhaul. Unit Aux Board/ Station Aux board  got Tripped of that Unit

Ø  Total Black Out of any stage

DG Load Trial and Regular checks

Requirements:

1	Inform & Ensure availability of TMD/EMD/C&I
2	SG/TG/BOP source-2 AC Power Supply Interruption. Inform C&I for Standby chargers
3	Ensure DG Set Tank Oil Level Adequate
4	Evacuate and Isolate Boiler Passenger, Service Building Lift and Isolate. Inform EMD(temporary supply )
5	Arrange 3 Walky Talky : 1-CR 2-DG board 3-DG Set room
6	Note Down Initial Parameters of DG Set

Furnace Air Tightness Test

Ø  Scope- Boiler Furnace, Air and FG Duct upto ID Fan Inlet

Ø  Why- To test Tightness of Furnace wrt Environment not for Strength

Ø  Ensure- All PTWs of BMD( PP, Rotary, Mills, Ash handling) cancelled and Clearance Available

Emergency Instructions:220 V DC Failure

220 V DC Failure

Unit condition

Ø  DCDB section-1 & 2 under voltage alarm in LVS-5

Ø  All HT/LT Breakers Indication Becomes Bad

Ø  Boiler will Trip on MFT ( after 2 Sec)

Ø  Turbine will Trip on MFT

Ø  Generator will not Trip as GCB Protection will not act

Ø  Generator will run as Synchronous Motor

Start-Up After 8 Hours of Shutdown ( Hot start-UP)

Unit condition

1	At least 2 BCW pump in Serrvice
2	Both SAPH and PAPH Running
3	Turbine : On Barring (AOP,JOP,SOP, HPCF  in service)
4	Generator: PW system, Seal Oil system, Gas system
5	Condenser Pass : Both Charged
6	PAC & IAC : 1 PAC & 2 IAC in Service
7	CEP & Make-up :  1 CEP with H/W Make-up on auto

Tripping on Boiler Tube Leakage

Mill reject system

CERC Norms 2019 Vs 2014 : Changes

TDBFP Rolling

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Turbine and TDBFP Overspeed & Oil Injection Test Procedure

Oil Injection of Main Turbine:

• Press Test Valve
• Turn Test Hand-wheel Anticlockwise slowly ( to develop Test Oil)
• Note Turbine Speed, Test Oil Pressure, Primary Oil Pressure when Bolts Operate(Aux Trip Oil becomes 0)
• Turn Test Hand-wheel Clockwise slowly (Test Oil pressure becomes 0)
  

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Volumetric Vs Gravimetric Mode : Feeder

Volumetrric Vs Gravimetric Mode : Feeder

• Coal properties constantly vary due to sizing differences and the adverse impact of moisture. These affect heating value, flow characteristics and density.The resultant density changes are measured by the Gravimetric Feeder. 
•  The gravimetric feeder compensates for the variation in bulk density and feeds a fixed weight of coal in response to a boiler fuel demand
•  This ability to accurately weigh the coal provides significant improvement over volumetric types in terms of matching the fuel delivered by the feeder to the actual process energy required on coal fired units. 

Benefits of Gravimetric Feeder

• Fuel Savings through Improved Boiler Efficiency
• Improved Combustion Efficiency/LOI
• Less Slagging and Fouling, leading to Less Corrosion
• Less NOx through Better Control of Excess Air
• Stability and Improved Response of Combustion Controls
• Improved Pulverizer/Cyclone/Combustor Performance
• Reduced Safety Concerns

How It Works : Gravimetric Mode

• Gravimetric feeder weighs material on a belt between two fixed points (span) precisely located in the feeder body.
• A roller, located midway in the span and supported at each end by precision load cells, supports half the weight on the span
• The load cells generate an electrical signal directly proportional to the weight supported. 
•  The microprocessor takes samples of the output of each load cell many times a second. 
• If the load cell outputs are within the expected range, they are added to obtain total weight per unit of belt length. 
• Belt speed is determined by sampling the output of a tachometer attached to the motor shaft, multiplied by a calibration factor to convert it into a belt speed signal
• The microprocessor multiplies the speed and weight signal for the feeder rate of fuel output.
• Finally, the microprocessor matches the feeder output to the output required by the boiler control, by adjusting the feeder motor speed.
• Feeders provide an accuracy of +/- ½ of one percent of totalized weight when calibrated and maintained

Volumetric feeding

• Volumetric feeder is Open-loop device

• Volumetric mode is set-speed constant , choke-fed or flooded infeed of a particulate solid and it feeds by volume only.
• Feed must have consistent bulk density
• As there is no information on  feedback of feeder ouput and drive control system

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Controlled Fast Cooling Procedure

Controlled Fast Cooling Procedure

• Normally Rihand-II and III 500 MW units take 8-9 days to stop Barring
• Using CFCP, it takes roughy 75 Hours after Desynchronisation.
• It is done in 2 stages.
• First Stage: Unit Parameters Lowered By Reducing Load and steam Parameters.
• Second stage: After Desynchronisation, till 350 Deg( HP Casing Temp), it is to be cooled thru Natural Cooling. thereafter by Modulating HPCV and Vacuum( Forced Cooling) maintaining Drop rate 5-6 Deg/Hour.
• During this : Top/Bottom DT, Differential Expansions, Axial shift, Bearing Temperatures, Bearing & shaft Vibrations need to be Observed and Logged in the sheet and if any Deviation Found, should be rectified.And if these deviations are beyond rectification, then abort force Cooling.

Stage I : Parameters Reduction on Load:

• Ensure all Auto Loops and SLCs in service and MS Temp <480 deg to be bypassed in order to lower Temperature. (Desk, Control Desk, SCE  & C&I with Proper logging in Register).
• Start Parameters Reduction Before 6 Hours to shut-down
• First Reduce Load by 5% (25 MW of 500 MW), then stabilise Load and Steam parametrs.
• Then Reduce MS Set point to 525 Deg .( Rate of Reduction of MS Temp :1.5~3 Deg/min)
• Further Reduce Load by 25 MW and stabilise parameters, and after that reduce MS Temp to 515 Deg.(If SH Attemperation in Manual if not maintaning )
• Repeat Above steps, till 300 MW and HP Casing Temp 480 Deg.
• Check HP Exhaust Temp with HP Exhaust Pressure, it should be above Saturation Temp value.
• Do not reduce load and MS Temp together because of DE, Transient vibration, Lower Margin of TSE.
• Open all MAL drains, HP SV/CV, Extraction drains as there may be consensate caused during parameters reduction.
• After HP Casing temp reaches 480 Deg, Desynchronise Machine.
• Ensure AOP, JOP, Barring gear starts as per logic.
• Note down the Coasting down time from 3000 rpm to 510 rpm,210rpm,120 rpm.

Stage II : Controlled Fast Cooling of Turbine

After Depressurisation of Ms Line( Thr Pr=0ksc), Ensure BSVs and their IBVs are Closed & Isolated.

Ensure all MAL drains, Extraction NRV drains are Open as per SLC.

Ensure HP/LP Heaters Extraction Valves are closed and Alternative Drip valve OPEN.

Kill Vacuum and Isolate Seal steam and GSC Ex Fan in On condition for intial cooling.

Isolate Aux PRDS from Unit and Other Interconnection with other Units.

Ensure HPBP Spray v/v closed

CW charged, one CEP in service and monitor LP Exh Hood temp

In 24 Hours, HP casing Temp reduces to 350 Deg

Controlled Fast Cooling by admitting air :

Ensure Turbine on barring gear.All stop & control valve closed

Ensure Casing Temp reached 350 deg by natural cooling

Open air inlet sockets b/w main stop & control valve and cover opening thru mesh

Set Test valve of all stop valves in Closed Condition.

Open HP control v/v. IP CV remain closed using Test motor(closing test oil signal)

Ensure gland area is clean, Pull Vacuum without seal steam charging

Ensure all MAL valve Open & Their isolating manual valve Open, SLC drain OFF

Stop GSC Ext Fan, allow air to be sucked thru Socket and gland area

Maintain vacuum -0.2 ksc initially, monitor TSI, TSE(lower margin in limit)

Maintain 5-6 deg/hour Temp drop by  by regulating HP CVs and vacuum pump.

After 48 Hours, HP Casing temp drops to 110-125 Deg. from 350 Deg

If drop rate is less than 5 deg/hr increase vacuum -0.4ksc

at 110 deg, Stop Barring