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Unit shutdown procedure operation

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Nitin Patel
Nitin Patel

The document outlines the steps to safely shut down a 210 MW power generation unit for overhaul and maintenance. It involves gradually reducing boiler steam parameters and turbine load over several steps by cutting mills and heaters, before finally tripping the turbine. Key steps include maintaining temperature differences, ensuring availability of emergency equipment, monitoring parameters, and opening drains. The shutdown is completed by venting the boiler drum and stopping auxiliary systems once drum pressure is reduced.

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9 N S PATEL DE (7069003798) OPERATION 4&5 210 MW UNIT SHUTDOWN PRODUCERS UNIT PLANED SHUT DOWN FOR OVER HAULING MAIN STEAM TEMPERATURE LEFT/RIGHT DIFFERENCE MAINTAIN < 20°C HP/IP CASING INNER/OUTER WALL TEMPERATURE DIFFERENCE MAINTAIN < 30°C HP/IP CASING TOP/BOTTOM TEMPERATURE DIFFERENCE MAINTAIN < 50°C MSV/MCV TI/TM TEMPERATURE DIFFERENCE MAINTAIN < 30°C NECESSARY CLEARANCE FROM SLDC / SCE 1. ALL COAL BUNKERS SHOULD BE PREFERABLY MADE EMPTY BEFORE LONG SHUT DOWN 2. STOP / REGULATE COAL FEEDING TO BUNKERS ACCORDINGLY 3. CHARGING OF AUXILIARIES PRDS STEAM FROM OTHER UNITS 4. ENSURE AVAILABILITY OF ALL FO GUNS 5. TAKE TRIAL RUN OF ALL EMERGENCY AUXILIARIES LIKE DC EOP, DC SOP, DC SCANNER AIR FAN ETC. 6. CARRYOUT WALL SOOT BLOWING AND APH SOOT BLOWING 7. ENSURE SGC OIL AND SLC OF OIL SYSTEM IS ‘ON’ 8. REDUCE COAL FIRING IN MILLS AND BRING DOWN THE UNIT LOAD TO 160 MW. 9. GRADUALLY REDUCE BOILER STEAM PARAMETER (STEAM/PRESSURE) 10. RATE OF REDUCTION TO BE CONTROLLED AS PER THE PERMISSIBLE LIMITS. 11. ENSURE THAT THE TSE MARGINS ARE OK AND SET TURBINE LOAD GRADIENT 05/10 MW/MIN 12. CHARGE DEAERATOR PEGGING STEAM FROM CRH OR AUXILIARIES PRDS 13. CUTOUT THE TOP MILL( E Mill) MAKE THE FEEDER BELT EMPTY BEFORE STOPPING OF MILL 14. ALL HP HEATER LEVEL SET POINT REDUCE THROUGH FLASH TANK AND KEPT EMPTY AND CUTOUT HP HEATER FROM STEAM SIDE 15. CUTOUT THE BOTTOP MILL( A Mill) 16. REDUCE UNIT LOAD 120 MW AFTER TAKING OIL SUPPORT IN CD ELEVATION FOR BOILER STABILITY 17. CUTOUT ONE MORE MILL(B Mill) AND REDUCE UNIT LOAD 80 MW 18. ENSURE THAT TURBINE GLAND SEALING STEAM TEMPERATURE > 250 °C AND CHANGE OVER FROM LEAK STEAM CONTROL TO SEAL STEAM CONTROLLER. 19. CHANGE OVER UNIT BUS POWER SUPPLY FROM UATS TO STATION BUS 20. MONITOR AND RECORD ALL TURBINE SUPERVISORY PARAMETERS 21. MONITOR BOILER DRUM TOP/BOTTOM DIFFERENTIAL TEMPERATURE WHILE REDUCING PRESSURE AND LOAD. 22. CUTOUT ONE MORE MILL(C Mill) AND REDUCE LOAD 50 MW 23. REDUCE LOAD TO 30 MW PARTIAL OPEN HP BYPASS TO MAINTAIN BOILER PRESSURE 24. CUTOUT LP HEATERS FROM STEAM SIDE MAINTAIN DRUM LEVEL 25. MAL DRAINS SLC KEPT ‘ON’ 26. TRIP THE TURBINE THROUGH PUSH BUTTON OR DCS EMERGENCY TURBINE TRIP. 27. ENSURE THE FOLLOWING AFTER TURBINE TRIP  GENERATOR CIRCUIT BREAKER OPENED  GENERATOR FIELD BREAKER OPENED
10 N S PATEL DE (7069003798) OPERATION 4&5  EXCITATION SUPPLY OFF  ESV/IV STOP VALVE & CONTROL VALVES , CRH NRVS VALVE SHOULD BE CLOSED  ALL EXTRACTIONS VALVE AND ITS OIL NRVS ARE CLOSED 28. TURBINE AOP HAS TAKEN START < 2850 RPM OF TURBINE SPEED 29. MONITOR TURBINE SPEED, BEARING VIBRATIONS, BEARING TEMPERATURE AND TURBO SUPERVISORY PARAMETERS DURING COSTING DOWN. 30. MONITOR HOTWELL LEVEL / DEAERATOR LEVEL AND CONDENSER VACUUM. 31. ENSURE OPENING OF THE FOLLOWING DRAINS MAL DRAINS MAL-65/ MAL-66, MAL -54/55, MAL 15/16, MAL- 26/27, MAL-31/32 and MAL- 47/51 ALSO HP CASING DRAINS AS WELL AS REQUIRED 32. STOP THE LAST MILL BEFORE FEEDER IS EMPTY AND BOILER STOPPED THROUGH PUSH BUTTON 33. ENSURE THE CLOSURE OF HOTV/IOTV AND ALL OIL GUNS HONV VALVES 34. CLOSED BOILER MAIN STEAM STOP VALVE AND HP BYPASS ALSO CLOSED 35. PURGE THE BOILER FOR 5 MINS AND SCAVENGE ALL THE OIL GUNS WHICH WERE IN SERVICE. 36. ISOLATED SH/RH SPRAY STATIONS ISOLATED FO/LDO ALL GUNS ISOLATING VALVES 37. STOP IF/FD FAN IF BOILER FORCE COOLING IS NOT REQUIRED 38. ENSURE THAT SCANNER AIR FAN EMERGENCY DAMPER HAS OPENED AFTER STOPPING BOTH FD FANS. 39. SWITCH OF ALL ESP FIELDS SYSTEM AND IF REQUIRED RAPPING SYSTEM. 40. ENSURE TURBINE JOP HAS TAKEN START AT 510 RPM AND JAKING OIL PRESSURE > 130 KG/CM² 41. GATE GEARING VALVE HAS OPENED AT TURBINE SPEED 200 RPM 42. ENSURE TURBINE HAS COME ON BARRING GEAR AND SPEED > 100 RPM 43. OPEN GENERATOR BREAKER ISOLATOR 400 KV SIDE 44. STATOR WATER COOLER/ SEAL OIL COOLER WATER SIDE ISOLATED AS TEMP GOES DOWN 45. RE-HEATER LINES TO BE EVACUATED COMPLETELY USING LP BYPASS VALVES 46. VACUUM CAN BE KILLED IN A SHUTDOWN UNIT PROVIDED THERE IS NO PASSING OF STEAM IN TO TURBINE AND THERE SHOULD NOT BE ANY RISE IN SPEED OF BARRING GEAR. 47. STOP CONDENSER VACUUM PUMP’S AND KILL VACUUM. 48. OPEN VACUUM BREAKER VALVE AND VACUUM REACHED 200 MM OF HG ISOLATED SEAL STEAM SUPPLY TO TURBINE GLANDS AND STOP GSC EXHAUSTER FAN 49. STOP ONE CW PUMP AND MONITOR LP TURBINE EXHAUST HOOD TEMPERATURE. 50. LP TURBINE EXHAUST TEMPERATURE < 55 °C STOPPED CE PUMP AFTER 04 HOURS. 51. CE PUMP STOPPING BEFORE LP WATER INJECTION SPRAY AND LP BYPASS V1/V3 MAY BE OPENED TO REDUCE LP EXHAUST HOOD TEMPERATURE. 52. CE PUMP SHOULD BE STOPPED ONLY AFTER ENSURING LP EXHAUST HOOD TEMPERATURE IS LESS THEN 55°C WITH LP WATER INJECTION AND LP BYPASS SPRAY CLOSED CONDITION. 53. ACW BOOSTER PUMP CAN BE STOPPED BEFORE STOPPING CW PUMP. 54. AT 02 KG/CM² DRUM PRESSURE OPEN BOILER DRUM VENTS, SH VENTS AND SH HEADER DRAINS

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Unit shutdown procedure operation

  • 1. 9 N S PATEL DE (7069003798) OPERATION 4&5 210 MW UNIT SHUTDOWN PRODUCERS UNIT PLANED SHUT DOWN FOR OVER HAULING MAIN STEAM TEMPERATURE LEFT/RIGHT DIFFERENCE MAINTAIN < 20°C HP/IP CASING INNER/OUTER WALL TEMPERATURE DIFFERENCE MAINTAIN < 30°C HP/IP CASING TOP/BOTTOM TEMPERATURE DIFFERENCE MAINTAIN < 50°C MSV/MCV TI/TM TEMPERATURE DIFFERENCE MAINTAIN < 30°C NECESSARY CLEARANCE FROM SLDC / SCE 1. ALL COAL BUNKERS SHOULD BE PREFERABLY MADE EMPTY BEFORE LONG SHUT DOWN 2. STOP / REGULATE COAL FEEDING TO BUNKERS ACCORDINGLY 3. CHARGING OF AUXILIARIES PRDS STEAM FROM OTHER UNITS 4. ENSURE AVAILABILITY OF ALL FO GUNS 5. TAKE TRIAL RUN OF ALL EMERGENCY AUXILIARIES LIKE DC EOP, DC SOP, DC SCANNER AIR FAN ETC. 6. CARRYOUT WALL SOOT BLOWING AND APH SOOT BLOWING 7. ENSURE SGC OIL AND SLC OF OIL SYSTEM IS ‘ON’ 8. REDUCE COAL FIRING IN MILLS AND BRING DOWN THE UNIT LOAD TO 160 MW. 9. GRADUALLY REDUCE BOILER STEAM PARAMETER (STEAM/PRESSURE) 10. RATE OF REDUCTION TO BE CONTROLLED AS PER THE PERMISSIBLE LIMITS. 11. ENSURE THAT THE TSE MARGINS ARE OK AND SET TURBINE LOAD GRADIENT 05/10 MW/MIN 12. CHARGE DEAERATOR PEGGING STEAM FROM CRH OR AUXILIARIES PRDS 13. CUTOUT THE TOP MILL( E Mill) MAKE THE FEEDER BELT EMPTY BEFORE STOPPING OF MILL 14. ALL HP HEATER LEVEL SET POINT REDUCE THROUGH FLASH TANK AND KEPT EMPTY AND CUTOUT HP HEATER FROM STEAM SIDE 15. CUTOUT THE BOTTOP MILL( A Mill) 16. REDUCE UNIT LOAD 120 MW AFTER TAKING OIL SUPPORT IN CD ELEVATION FOR BOILER STABILITY 17. CUTOUT ONE MORE MILL(B Mill) AND REDUCE UNIT LOAD 80 MW 18. ENSURE THAT TURBINE GLAND SEALING STEAM TEMPERATURE > 250 °C AND CHANGE OVER FROM LEAK STEAM CONTROL TO SEAL STEAM CONTROLLER. 19. CHANGE OVER UNIT BUS POWER SUPPLY FROM UATS TO STATION BUS 20. MONITOR AND RECORD ALL TURBINE SUPERVISORY PARAMETERS 21. MONITOR BOILER DRUM TOP/BOTTOM DIFFERENTIAL TEMPERATURE WHILE REDUCING PRESSURE AND LOAD. 22. CUTOUT ONE MORE MILL(C Mill) AND REDUCE LOAD 50 MW 23. REDUCE LOAD TO 30 MW PARTIAL OPEN HP BYPASS TO MAINTAIN BOILER PRESSURE 24. CUTOUT LP HEATERS FROM STEAM SIDE MAINTAIN DRUM LEVEL 25. MAL DRAINS SLC KEPT ‘ON’ 26. TRIP THE TURBINE THROUGH PUSH BUTTON OR DCS EMERGENCY TURBINE TRIP. 27. ENSURE THE FOLLOWING AFTER TURBINE TRIP  GENERATOR CIRCUIT BREAKER OPENED  GENERATOR FIELD BREAKER OPENED
  • 2. 10 N S PATEL DE (7069003798) OPERATION 4&5  EXCITATION SUPPLY OFF  ESV/IV STOP VALVE & CONTROL VALVES , CRH NRVS VALVE SHOULD BE CLOSED  ALL EXTRACTIONS VALVE AND ITS OIL NRVS ARE CLOSED 28. TURBINE AOP HAS TAKEN START < 2850 RPM OF TURBINE SPEED 29. MONITOR TURBINE SPEED, BEARING VIBRATIONS, BEARING TEMPERATURE AND TURBO SUPERVISORY PARAMETERS DURING COSTING DOWN. 30. MONITOR HOTWELL LEVEL / DEAERATOR LEVEL AND CONDENSER VACUUM. 31. ENSURE OPENING OF THE FOLLOWING DRAINS MAL DRAINS MAL-65/ MAL-66, MAL -54/55, MAL 15/16, MAL- 26/27, MAL-31/32 and MAL- 47/51 ALSO HP CASING DRAINS AS WELL AS REQUIRED 32. STOP THE LAST MILL BEFORE FEEDER IS EMPTY AND BOILER STOPPED THROUGH PUSH BUTTON 33. ENSURE THE CLOSURE OF HOTV/IOTV AND ALL OIL GUNS HONV VALVES 34. CLOSED BOILER MAIN STEAM STOP VALVE AND HP BYPASS ALSO CLOSED 35. PURGE THE BOILER FOR 5 MINS AND SCAVENGE ALL THE OIL GUNS WHICH WERE IN SERVICE. 36. ISOLATED SH/RH SPRAY STATIONS ISOLATED FO/LDO ALL GUNS ISOLATING VALVES 37. STOP IF/FD FAN IF BOILER FORCE COOLING IS NOT REQUIRED 38. ENSURE THAT SCANNER AIR FAN EMERGENCY DAMPER HAS OPENED AFTER STOPPING BOTH FD FANS. 39. SWITCH OF ALL ESP FIELDS SYSTEM AND IF REQUIRED RAPPING SYSTEM. 40. ENSURE TURBINE JOP HAS TAKEN START AT 510 RPM AND JAKING OIL PRESSURE > 130 KG/CM² 41. GATE GEARING VALVE HAS OPENED AT TURBINE SPEED 200 RPM 42. ENSURE TURBINE HAS COME ON BARRING GEAR AND SPEED > 100 RPM 43. OPEN GENERATOR BREAKER ISOLATOR 400 KV SIDE 44. STATOR WATER COOLER/ SEAL OIL COOLER WATER SIDE ISOLATED AS TEMP GOES DOWN 45. RE-HEATER LINES TO BE EVACUATED COMPLETELY USING LP BYPASS VALVES 46. VACUUM CAN BE KILLED IN A SHUTDOWN UNIT PROVIDED THERE IS NO PASSING OF STEAM IN TO TURBINE AND THERE SHOULD NOT BE ANY RISE IN SPEED OF BARRING GEAR. 47. STOP CONDENSER VACUUM PUMP’S AND KILL VACUUM. 48. OPEN VACUUM BREAKER VALVE AND VACUUM REACHED 200 MM OF HG ISOLATED SEAL STEAM SUPPLY TO TURBINE GLANDS AND STOP GSC EXHAUSTER FAN 49. STOP ONE CW PUMP AND MONITOR LP TURBINE EXHAUST HOOD TEMPERATURE. 50. LP TURBINE EXHAUST TEMPERATURE < 55 °C STOPPED CE PUMP AFTER 04 HOURS. 51. CE PUMP STOPPING BEFORE LP WATER INJECTION SPRAY AND LP BYPASS V1/V3 MAY BE OPENED TO REDUCE LP EXHAUST HOOD TEMPERATURE. 52. CE PUMP SHOULD BE STOPPED ONLY AFTER ENSURING LP EXHAUST HOOD TEMPERATURE IS LESS THEN 55°C WITH LP WATER INJECTION AND LP BYPASS SPRAY CLOSED CONDITION. 53. ACW BOOSTER PUMP CAN BE STOPPED BEFORE STOPPING CW PUMP. 54. AT 02 KG/CM² DRUM PRESSURE OPEN BOILER DRUM VENTS, SH VENTS AND SH HEADER DRAINS