Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)The following procedure is intended to provide guidance on the general operation of the plant. It is not intended to take the place of any operating instructions provided by the original equipment suppliers, nor is it intended to be used as a substitute for operational job sheets or detailed procedures which would typically be developed by the plant operator, to suit the level of experience and ability of his staff. A. BOILER : NORMAL SHUTDOWN TO COLD The following procedures for normal shutdown assume that the unit is operating at full load on automatic control, and the intention is to reduce the unit pressure to zero and cool the boiler completely. 1. The rate at which load is reduced will be a function of the turbine requirements. The operator determines the required trip load and the rate of load decrease as input, then the control system will automatically reduce boiler inputs at the required rate. Feed water, airflow, fuel flow, and steam temperature should remain on automatic control during the shutdown for best-coordinated control. Reduce the unit load at a rate determined following the prescribed sliding pressure vs. load curve (for a shutdown to hot, a higher pressure may be desirable to preserve energy in the unit). Steam temperatures will automatically follow the predetermined program. At approx 20% load the superheat spray valves are automatically closed and steam temperature will be controlled solely by biasing between fuel and feedwater flow. Reduce the firing rate in line with the decreasing steam flow. Leave the steam temperature, combustion and feedwater controls on automatic to 30% load. When the feeder rating on all pulverizers is reduced to 40%, put the upper elevation of warm-up fuel in service. Place the pulverizer supplying the upper coal elevation on manual control. Gradually reduce the feeder rating. When minimum rating is reached, close the hot air shutoff gate and adjust the cold air damper to maintain 100% pulverizer air flow.. Stop the feeder when the coal/air temperature has dropped to approximately 130F (54C). Close the coal shutoff gate above the feeder, run the feeder until the spout and feeder are empty, and then stop the feeder. Make sure the pulverizer is completely empty by running it for at least 3 minutes. Then, stop the pulverizer. Unless an emergency condition exists, the pulverizer should always be emptied in this manner before being stopped. (Refer shutdown procedures in the Pulverizer and Pulverized Coal System sections of this manual). As pulverizers are taken out of service, the secondary air damper control system should close the associated wind box dampers and adjust the other dampers to compensate for the reduced firing rate. Take the second pulverizer supplying the next highest elevation of coal nozzles out of service when the feeder rating on all remaining pulverizers reaches 40%. Continue taking additional pulverizers out of service in the same manner. When only two pulverizers remain in service, the adjacent warm up fuel must be placed in service prior to reducing the feeder rating of either pulverizer to below 50%.

2.

3. 4.

5.

6.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)It is recommended that this consecutive elevation shutdown sequence be followed. Firing coal at separated coal nozzle elevations without auxiliary supporting fuel is not permitted. 7. Over fire air will be reduced automatically as the unit load is reduced per the prescribed control curves. Below approximately 30% load, over fire will be closed to a minimum position. Keep the over fire air dampers at minimum open position to prevent the nozzle tips from overheating. Operate all soot blowers as load is reduced. (Refer to the soot blower manufacturers instructions). Normally the unit controls will be on automatic during the shutdown, which will automatically maintain the design fuel-air balance. If it is necessary to use manual control, reduce the airflow by reducing FD fan flow in line with the fuel reduction until 30% airflow is reached. Do not reduce the airflow below this rating until all fires are out, a furnace post firing purge has been completed and the unit is off the line (Refer air flow curve and the Percent Excess Air Versus Load curves, as recommended in the Design and Operation manual of manufacturer). To avoid firing instability during this period of high airflow, the auxiliary air dampers at all elevation should open and the wind box-to-furnace differential pressure reduced to its lower setting per the manufacturers prescribed control curve. Check the boiler expansion movements as the load is reduced. Remove the pollution control equipment from service according to the manufactures instructions. At app. 40% steam flow, feed water flow will be higher than the firing rate. The steam temperature at the separator outlet will fall below the superheated region, and a water level will develop in the SST. The boiler will now be returned to recirculation (wet) mode. The boiler is proven in recirculation (wet) mode when all the following conditions exist: i. ii. iii. iv. Steam flow < 40%. Separator storage tank level > 39 inches (1 meter) Separator outlet temperature < saturation temperature + 30F (17C), Difference between economizer inlet temperature and feed water inlet temperature >10F (6C).

8. 9.

10. 11. 12.

FW flow control will switch from coordination of FW-Firing Rate controlling steam temperature to SST level control. The Boiler Recirculating Pump (BRP) will be auto started to provide minimum water wall evaporator flow. 13. Continue to reduce load to the predetermined load where the turbine will be taken off-line. At this point a turbine trip should be automatically initiated, and the bypass system valves will open. After the last pulverizer is shut down, remove the warm up fuel from service. All fires should

14.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)be extinguished when the unit is off the line. With no pulverizers in service, the PA fans and the pulverizer seal air fans may also be shut down. The PA fans should not be shut down if the air heater gas inlet temperature is above 400F (205C) 15. 16. After all fuel firing is removed, close the HP and LP bypass valves. Immediately after closing the HP/LP bypass valves, open the superheater outlet vents and drains and all reheater vents and drains. Open other drains in the superheater system, as required, for further pressure reduction. Open the steam line ,drains, reheat line drains and turbine drains as per the turbine manufacturer's instructions. Close the desuperheater isolating valves and ensure CRH spray water valves are closed. Do not exceed a cool down rate of 104C/hr of fluid temperature change anywhere in the unit. Operate the economizer grits and air heater grits removal cycles, and empty the economizer and air heater hoppers. Operate the SSC drag chain until the SSC is completely empty of ash. It can then be shutdown. Empty each pulverizer reject hopper. When all hoppers are empty, the sluicing system can be shutdown. If the steam generator will not be entered during the shutdown period, a slower rate of pressure and temperature decay may be desirable. This can be accomplished as follows: i. ii. Complete a post trip purge of the unit by running the ID and FD fans for at least 5 minutes at 30% airflow after the fires are extinguished. If not already done, reduce the airflow through the unit to 30% minimum airflow. Keep the fans and air heaters in service until the unit has cooled to the desired temperature. Air heaters and fans should not be taken out of service until the air heater gas inlet temperatures have dropped below 205C. Keep the BRP in service until the boiler water temperature is reduced to the desired point. Keep the water level near normal in the SST, adding makeup water as required.

17. 18. 19.

20.

21.

iii.

22.

If the cooling process must be accelerated to permit entry into the steam generator for maintenance, proceed as in step 212121, except: i. Continue running the fans at the desired rate to cool the unit. The air heaters may be shut down when the gas entering temperature has dropped below 205C. Refer to the air heater instructions. With the air heaters stopped and the fans running, deposits of fly ash may

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)accumulate in the air heater and cause a rotor unbalance. ii. Keep the BRP in service to increase recirculation. Keep the water level near normal in the separator storage tank. Shut down the pump when the boiler water temperature is reduced to the desired level.

23.

Do not shut down the scanner/ignitor air fan until the furnace temperature has dropped to below 149C. 23.24. If the boiler is to be laid up wet,refer to lay-up procedure. 24.25. For emptying the boiler, the boiler water temperature should be reduced to at least 93C before draining. NORMAL SHUTDOWN TO HOT STANDBY During a shutdown to hot standby, it is assumed that the unit will be shut down for a relatively short period of time and that the existing pressure and temperature conditions will be substantially maintained. A procedure similar to that for normal shutdown should be used, with the following exceptions: 1. Reduce steam pressure in line with unit load reduction, following the prescribed sliding pressure curve. To preserve energy in the boiler, maintain a higher pressure (approximately 2000 psig (141 kg/cm2)) until the turbine is taken off line. After the turbine is off line, fires removed and HP/LP bypass valves closed, the boiler may be bottled up by closing all superheater drains and vents. Reheater drains and vents should be opened to relieve pressure in the reheater. If the unit will be restarted soon enough to prevent turbine metal temperatures from decreasing appreciably, it may be desirable to cool the turbine metal by reducing the steam temperature and pressure, while the unit load is being reduced. This will reduce the steam/turbine metal differential temperature upon restart. Refer to the turbine manufactures instructions. 2. It is not necessary to close the feeder inlet gates and run the spouts and feeders empty. As each pulverizer is taken out of service, close the hot air shutoff gate. Stop the feeder when the coal/air temperature drops to 54 deg C. Run the pulverizer for a 3 minute period until it is empty, and then stop the pulverizer. The BRP should be kept in operation to ensure uniform boiler metal temperatures. This will prevent possible local overheating due to hot slag deposits. After the fires are extinguished, keep the ID, FD and PA fans and air heaters running until the air heater gas inlet temperatures have dropped to below 205C. Close all gas duct and secondary air duct dampers after the air heaters and fans are shut down. Keep the scanner air fan running. Shut down the BRP after the unit has been bottled up. However, if an immediate hot restart is anticipated, keep the BRP in service for more effective warm-up circulation.Formatted: Font: Arial, 11 pt

Comment [k1]: As per presentation given by Alstom, in case of restart MS pressure will be maintained at 180 bar. Please check since this will be required for HPLP bypass philosophy. DESEIN : ALSTOM to confirm Formatted: Highlight Formatted: Highlight Formatted: Highlight Comment [k2]: Desein to confirm the lower limits. DESEIN : L&T to specify.

3.

4.

5.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)6. The operator should observe the SST level periodically so that he is always aware of the actual level and can take the appropriate action to re-establish the water level when the unit is being restarted. When the BRP is shut down, the water level will rise. As the unit cools and the water shrinks, makeup water should be added intermittently to prevent the water from dropping below normal level. Adding relatively cold feedwater will establish a reservoir of cooler water in the system. If the BRP is then started, this cooler water will produce a cycle of cool and hot temperature transients to the pump casing and other pressure parts of the boiler. The BRP should be operating when makeup water is added to minimize the temperature stratification. EMERGENCY PROCEDURES: 1. Reheater Protection Stopping or significantly reducing steam flow through the reheater when the entering gas temperature is above 593 deg C can cause overheating and damage to the reheater tubing. To prevent this condition, the following measures are taken with the automatic reheat protection interlocks. TURBINE VALVE CLOSURE If a loss of load should cause the turbine valves to close , the turbine will be rundown to house load and the boiler should be rundown to below the HP bypass capacity (60% BMCR or 65% TMCR at full pressure) plus house load demand (approximately 5 %). If the HP bypass is not proven open within a short time delay, then all fuel should be tripped automatically and instantaneously. If a master fuel trip occurs following turbine control valve closure, an immediate restart is feasible in most instances because the turbine is still rolling and will be available to take steam as soon as the governor has the turbine speed under control. (Refer to turbine manufacturers instructions for no load operating procedures and limitations.) If an immediate turbine restart is not possible and the turbine is tripped, the CRH and HRH drain lines should be opened (refer to turbine trip below) 2. Turbine Trip i. If the turbine is tripped, then the boiler should be rundown to match the capacity of the HP bypass (60% BMCR or 65% TMCR at full pressure). If the HP bypass is not proven open within a short time delay, all fuel should be tripped automatically and instantaneously. The superheater and reheater safety valves will protect against overpressure. The CRH and HRH drain lines to the condenser should be opened to evacuate the steam in the reheater in the event of a unit trip.

ii.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)

3.

Post-Trip Procedures i. ii. The furnace must be purged immediately following a master fuel trip. Empty any pulverizer containing coal as soon as possible. Refer to Master Fuel Trip.

4.

Master Fuel Trip When a master fuel trip occurs automatically through normal interlocks, or is initiated manually by an operator, all fuel shall be tripped instantaneously. If coal is being fired, the pulverizers shall be tripped immediately. The master fuel trip will automatically trip the feeders and close the hot air gates and close the cold air shutoff gates on pulverizers that were in service at the time of the trip. (Refer to Pulverizer Emergency Shutdown Procedures). Also refer to the pulverizer clearing procedure located in the steam inerting section of the Design and Operations manual. If warm-up fuel was being fired, the fuel trip valves and individual nozzle shutoff valves should be closed immediately. The following steps should be taken immediately following an emergency fuel trip: i. Maintain the unit airflow at the pre-trip value for at least 1 minute and then gradually reduce the airflow to the purge rate (30% airflow) and complete a unit post trip purge. If a hot restart is anticipated, the prefiring purge can be initiated once all purge permissives are met. After re-establishing SST level > 39 inches (1 meter) and all other permissives are satisfied, the BRP should be auto started and recirculation established to maintain uniform temperatures throughout the boiler circulation system. Using the Motor operated BFP, make-up water should be added to re-establish normal level in the SST. These steps will naturally cause pressure to decay. Note that the start up system valves (HWL-1, HWL-2) are interlocked to prevent opening above 102 kg/cm2 to protect the flash tank, so pressure must be reduced in preparation for a restart. (Refer to Boiler Circulating Pump Operating Procedures). Procedure after Master Fuel Trip when all ID and FD Fans are off: a. The ID and FD fans discharge dampers shall be opened to allow natural ventilation of the unit. Opening of fan(s) dampers shall be timed or controlled to avoid excessive furnace pressure excursions during fan(s) coast-down. The fans discharge dampers shall remain open for a period of at least 15 minutes. During this 15-minute period, the ID and FD fans shall not be started. At the end of the 15-minute period, the ID/FD fans may be started in accordance with ID/FD fan(s) start-up procedures.

ii.i.

b. c.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)d. iii.ii. iv.iii. If the unit will not be re-started for an extended time, a flow of air through the unit shall be maintained.

If warm-up fuel is in service when the fuel trip occurred, make sure the warm-up header trip valve and individual nozzle shutoff valves are closed. If all auxiliaries are lost during a fuel trip, refer to the Boiler Circulating Pump Operating Procedures for handling the low pressure cooling water. The cooling flow must be maintained. If all auxiliary power sources were lost during a trip, after completing the 15 minute natural draft purge described above, start the fans and air heaters when power is restored, increase the unit airflow to the purge rate and complete a 5 minute purge. Observe the hot restart precautions in the air heater instructions. The BRP, if available, should be placed in service during the purge, and the boiler should be refilled. (See Boiler Circulating Pump Operating Procedures for restarting procedures). If pulverizers are in service when the fuel trip occurs, all operating pulverizers will be automatically inerted. Refer to section on Pulverizer Inerting and Fire Fighting for details. The pulverizers must remain under inerting until they can be cleared of coal or cooled to ambient. After a boiler trip at a high pressure,a controlled pressure reduction is carried out to the highest pressure with which a restart is possible (to approximately 180 bar) to obtain reliable SST level indication. The BRP should be placed back in service and recirculation established to maintain uniform temperatures throughout the boiler circulation system and to enable a restart of the boiler. The boiler must be refilled to re-establish normal SST level for BRP restart and the minimum recirculation flow must be re-established as a prerequisite for re-firing. This process will naturally cause pressure to decay, concurrent.with the controlled pressure reduction. Check that the startup system is ready for operation (HWL-1 isolation valve open, HWL-2 is interlocked to prevent opening at high pressure to protect the flash tank) and the drain transfer system is ready for operation. Place the BFPM in service, stabilize deaerator conditions, and establish feedwater flow of 10% BMCR to the boiler to refill to normal SST level. Follow the same procedure for boiler filling as outlined previously. When SST level is stable with HWL-1 at stable opening and all BRP start permissives are satisfied, start the BRP (Refer to Boiler Circulating Pump Operating Procedures). Zero the feedwater flow as SST level recovers and attains the operational setpoint. If restart of the BRP is delayed, excessive HWL action will result in draining of water at pressure, oscillatory dump-feed action, with further reduction in boiler pressure and extension of startup time The prefiring furnace purge can be initiated once all purge permissives are met. If the boiler cannot be immediately restarted, then raise load to >20% on auxiliaryFormatted: List Paragraph, Left, Line spacing: single, No bullets or numbering, Hyphenate, Tab stops: Not at 1.25"

v.iv.

v.

vi.

vii.

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viii.

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vi.ix. vii.x.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)fuel utilizing the HP/LP bypass and then successively clear the pulverizers serving at least the 2 lower coal elevations using the steam transport system prior to resynchronizing the turbine as described below while the SG is operated on Bypass at >20% BMCR firing auxiliary fuel. The remaining pulverizers can be cleared using steam transport before or after the turbine is synchronized. Refer to the pulverizer clearing procedure located in the steam inerting section of the Design and Operations manual for additional details: a. Close the pulverizer discharge gates on all other idle pulverizers containing coal during each steam transport procedure. This prevents hot furnace gases from being carried back into the pulverizers in the event of a furnace pressure rise when a pulverizer is started. Start the lower elevation of warm-up fuel and establish the ignition energy required to start a pulverizer. Refer to, COLD START-UP, and to the Control System suppliers instructions for ignition energy requirements and permissives. IF RH flow has not been establish via the HP bypass or via turbine synchronization, then reduce furnace exit gas temperature to 900-950 deg F (482-510C) by adjusting warm-up fuel flow. before transport steam flow is initiated Before transport steam flow is initiated, reduce furnace exit gas temperature to 900-950 deg F (482-510C) by adjusting warm-up fuel flow. Clear pulverizer A by following the pulverizer transport procedure located in the steam inerting section of the Design and Operations manual Shut down pulverizer A. Clear pulverizer B per the same procedure. Continue with normal unit start up sequence until both pulverizers are in service and the turbine is synchronized. When boiler load is approximately 20%, the remaining pulverizers may be cleared one at a time using the steam transport procedure and returned to normal service or shut down in a normal fashion if not required for load regulation. If the pulverizer will be retained in service, when the pulverizer has completed the clearing process, open the hot air shutoff gate, bring the pulverizer up to normal operating temperature and start the associated feeder. If the pulverizer will not be retained in service, stop it after completely clearing the coal. The pulverizer discharge gates should remain open to allow a flow of cooling air through the empty pulverizer.Formatted: List Paragraph, Left, Line spacing: single, No bullets or numbering, Hyphenate, Tab stops: Not at 2.5" Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt, Not Highlight

b.

b.c.

c. d. e. f. g. h.

i.

j.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)viii.xi. If, due to load conditions and/or requirements to the Burner Management System, it is impossible to establish ignition permissives to allow steam transport, inerting steam shall be maintained until each pulverizer can be cleared of coal using steam transport or cooled to ambient ix.xii. If the boiler cannot be re-started and the auxiliary steam source cannot be continued indefinitely, then the pulverizers (which still containing coal) must be switched to an alternate steam inerting source or to an alternate inerting medium until they can be cooled to ambient and manually emptied. Refer to the clearing procedure located in the Pulveriser Inerting and Fire Fighting section of the Design and Operations manual for additional details.

5. Low Water wall Flow i. The flow entering the economizer is monitored continuously to direct and alert the operator of abnormal flow conditions. Low flow could be the result of a malfunction of BRP, MEFCV, feedwater pump, controls, or operator neglect. Low flow subjects the water wall tubing to overheating, and potential for failures. ii. If the flow drops below the alarm set point, the operator must check the above listed items. iii. If the water wall flow continues to drop below the minimum trip set point, automatically trip the fuel following a maximum 10-second time delay. The time delay allows for momentary fluctuations due to valve transfers, etc.: a. b. c. d. e. f. g. Trip all fuel immediately. Shut off all steam being discharged from the unit (trip turbine, steam driven auxiliaries, and such). Leave the BRP in service as long as it is operating normally. If the problem is rectified, re-establish minimum water wall flow. If the BRP cannot be kept in service, do not admit feedwater to the unit. Maintain a high airflow at first to hasten the cooling process. If pressure part damage is suspected, reduce the steam pressure gradually by opening the super heater start-up drains. As the boiler cools, reduce the airflow. Shut down the air heaters and fans as soon as the unit is cool enough to enter. When the separator metal temperature is 200F (93C), drain the boiler following normal draining procedures. Determine the cause of low water flow and examine the boiler for signs of overheating, such as leaks and distorted pressure parts. Repair any leaks.

h.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)i. Hydrostatically test the boiler before putting the unit back in service.

6. High Water wall Tube Temperature Permanent thermocouples are installed on selected furnace spiral and vertical tubes. The purpose of these thermocouples is to direct and alert the operator to any abnormal condition of excessive heat absorption or low fluid flow. High water wall tube temperatures are an indication of an imbalance between firing rate and water wall flow (over firing, low water wall flow, or combination of both). Over firing could be a result of extreme load change rates. Low water wall flow could be a result of excessive SH spray flow, BRP trouble,MEFCV trouble,feedwater pump trouble, control system trouble, or tube blockage. If water wall tube metal temperatures exceed the alarm set point, then the operator should investigate the above listed items. If water wall tube metal temperatures exceed the trip set point, automatically trip the fuel following maximum 3- second time delay. This trip protects the tubes from overheating damage and potential failure and therefore immediate action is required. Investigate the above listed parameters and their control before re-firing the boiler. 7. Evaporator Inlet Sub-Cooling The fluid condition entering the evaporator is monitored to alert the operator to abnormal conditions. If the fluid entering the evaporator is allowed to rise into the saturation region, the flow distribution in the evaporator will be detrimentally affected, causing tube temperatures to increase. If the fluid condition at the evaporator inlet is sub-cooled by less than 6C, an alarm is generated. The operator should take steps to reduce the temperature of feed water entering the economizer or increase the flow of feed water entering the pumps. 8. Loss of All Feedwater Pumps If all feedwater pumps are tripped at any time, cooling of all boiler circuits will be lost. All fuel must be automatically tripped with a maximum 20-second time delay. 9. Low Airflow If airflow drops below 25% at any time, combustion conditions could become dangerously unstable. All fuel shall be automatically tripped immediately. 10. Furnace Pressure High/Low

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)If furnace pressure exceeds the high-high or low-low set point at any time, all fuel shall be automatically tripped immediately. A warning alarm is generated at high and low set points. 11. Separator Storage Tank Level High If the SST level exceeds the high-high level set point, then all fuel shall be tripped immediately. An warning alarm is generated at high set point, at which time the operator should check operation of the HWL valves, SST level control, or the balance of feedwater and firing rate (possible that firing rate is too low for feedwater flow). 12. Airheater Gas Outlet Temperature High If the gas temperature leaving the air heater exceeds the high setpoint, all fuel shall be tripped immediately. This is to protect downstream equipment from over-temperature. 13. Both FD Fans Off or Both ID Fans Off If at any time both FD and both ID fans are off while firing the boiler, then all fuel shall be automatically tripped immediately. 14. Load Run-Backs Upon loss of the following equipment, load must be automatically reduced to a level that can be supported by the remaining equipment. The load reduction is typically at a rate of 50% per minute (except for individual pulverizer trips). The reduction of fuel input is accomplished by equal decrease of coal feeder speed or by tripping of pulverizer(s) (for loss of PA fan or BFP). 1. 2. 3. 4. 5. 6. 7. 5. 6. One out of two FD fans. One out of two ID fans. One out of two PA Fans. One out of two feedwater pumps. Any pulverizer(s). (depending on boiler load and number of pulverizers in service ) One out of two air heaters Turbine trip (as described above) Disconnection from electrical grid without turbine trip (as described above) One out of two PA or SA air heatersRunback Initiator Target LoadFormatted: Normal, Justified, Indent: Left: 0.5", Line spacing: At least 12 pt, Don't hyphenate Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt, Not Highlight Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt Formatted: Normal, Justified, Indent: Left: 0.5", Hanging: 0.5", Line spacing: At least 12 pt, Numbered + Level: 4 + Numbering Style: 1, 2, 3, + Start at: 1 + Alignment: Left + Aligned at: 1.75" + Tab after: 2" + Indent at: 2", Don't hyphenate Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt, Not Highlight Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt Formatted: Font: (Default) Arial, 11 pt, Condensed by 0.15 pt, Not Highlight Formatted: Normal, Indent: Left: 0.5", Line spacing: At least 12 pt, Don't hyphenate

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R

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)One PAF on One FDF on One IDF on One airheater on One BFPT on and One BFPM on One BFPT on One BFPM on Main turbine trip 50% 50% 50% 50% 75% or capacity of BFPT + BFPM 50% or BFPT capacity 30% or BFPM capacity 60% (within HP Bypass capacity) 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minute 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minute Formatted: Font: (Default) Arial, 10 pt 50% per minuteFormatted: Font: (Default) Arial, 10 pt Formatted: Font: (Default) Arial, 10 pt

15. Tube Failures If any water or steam carrying tube fails, the best shutdown method will be dictated by the size of the failure, the ability to maintain a normal water flow (or level if the boiler is in the recirculation mode) and the demand for the unit to remain in service. The following instructions are general since most of the conditions will require the judgment of the operators. 16. Water wall Tubes If a leak or tube failure does not involve a serious drain on the feedwater supply, the water flow/level should be maintained and the unit taken out of service in the normal manner: a. Operate the soot blowers if conditions permit. b. Switch the combustion control equipment to manual control and proceed to reduce the firing rate and air flow in a normal manner. c. When all fires are extinguished continue the airflow through the unit at a reduced rate to purge all combustible gases, vapors, etc. Shut down the fans when the unit is cooled sufficiently. d. Feed water to the boiler by manual control. To speed cooling, boiler pressure can be reduced by opening the super heater outlet drains. e. Allow the boiler to cool at least to 200F (93C) (separator metal temperature); before draining. If there is a serious water loss and the water flow/level cannot be maintained with the feedwater supply available. Use the following method: a. Trip all fuel. b. Shut off the feedwater to the boiler. c. Maintain only enough airflow to carry the escaping steam up the stack. d. Leave the fans and air heaters in service until pressure is off the unit e. Once the unit is cool enough to enter, inspect the pressure parts for damage

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)caused by the loss of water level. After the necessary repairs have been made, apply a hydrostatic test and obtain the approval of the proper authorities before putting the unit back in service. 17. Economizer Tubes An economizer tube leak can be detected by sound and/or increased makeup water requirements. Check the leak as soon as possible. Water leaks in the economizer can cause considerable erosion damage to adjacent tubes. Water carried over from an economizer tube leak may cause plugging of hoppers and air heaters. Any decision to continue operation with known leaks should be made with this in mind. The unit should be shut down in a normal manner. 18. Superheater and Reheater Tubes A leak in a super heater or reheater element should be checked as soon as possible. Steam leaks in the super heater or reheater can cause considerable erosion damage to adjacent tubes. Any decision to continue operation with known leaks should be made with this in mind. The unit should be shut down in a normal manner. A major super heater or reheater tube failure may require an emergency unit shutdown. The operator must judge the degree of failure, its consequences, and then decide what type of shut down is required. . 19. Shutdown without BRP 1. 2. Reduce load in auto mode following the normal procedure. At approximately 40% load, the boiler will transfer to the recirculation mode. With the BRP off, the feed water flow set point will automatically control the BFP loading to maintain the minimum economizer flow set point. The HWL-1 will open in auto mode when the level in the SST reaches the high set point. If additional drain capacity is needed, HWL-2 will open when HWL-1 reaches full open and level continues to rise. Note that the start up system valves (HWL-1, HWL-2) are interlocked to prevent opening above 2100 psig (148 kg/cm2) at higher pressure to protect the flash tank, so pressure must be reduced to less than this value before the transfer to recirculation mode is made. Continue to reduce load and shutdown the unit following the normal procedure. Keep the BFP in service with the feedwater flow at minimum set point of 40% until the boiler water temperature is reduced to the desire point. Keep the water level near normal in the SST, draining water via HWL valves as required.

3.

4.

5. 6.

Recommended Shutdown Guidelines

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)RECOMMENDED SHUTDOWN GUIDELINES and LIMITATIONS Material Temperature Gradient Limitation All Boiler Temperature < 232C Components Decreasing Temperature > 232C Decreasing 333C/hr 83C/15 Minutes 167C/hr 42C/15 Minutes

A1: SHUT DOWN PROCEDURE FOR Electrostatic Precipitator (EP)

a. b. c. d. e.

Switch-off the transformers at dropping of gas temperature to 120 degree centigrade. Continue rapping in continuous mode for approximately thirty minutes (Power-off rapping). Empty the ash hoppers and switch off heating element after ID fan has stopped. Switch 'OFF' control cubicle and LT main supply. Switch 'OFF' HV disconnecting switch. After locking the control panel in control room, inspection doors may be opened for cooling.

f.

During shut down inspect the internals for i. ii. iii. iv. Snapped or loose wires Excessive ash accumulation Displacement of shock bars, shock bar guides and collecting electrode. Any other abnormality.

g.

Short term shut down when no work inside EP is expected. Close the inlet and outlet dampers. Do not open the doors. this reduces the precipitator start up time by retaining as much heat as possible. Heaters need not be switched off.

h.

Short terms shut down when inspection of EP is required.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)i. ii. Heaters where inspection is carried out along need be switched off. Complete the internal check and close the doors as quickly as possible.

Caution: On no account must access to EP internals be attempted unless HV systems are switched off, isolated and appropriate access permits issued. Earthing rods are applied. Interlock sequence is adhered to and inside temperature is dropped to a safe level. i. Normally the precipitator does not require any periodical manual cleaning since the rapping systems ensure adequate cleaning of EP internals during the operation. However operation of EP under following conditions may cause excessive dust deposit on the internals. a. b. c. d. Prolonged operation of EP without rapping mechanisms. Energisation of EP with wet internals. Operation of EP below acid dew point. Flue gas entering the EP is misty due to incomplete fuel particularly at the time of initial boiler operations.

Accumulation of such dust deposits not only causes the reduction of precipitator efficiency but also results in unstable operation, rapid corrosion of electrodes and failure of insulators. Therefore during any shutdown if excessive ash deposit is noticed, clean the internals and identify the cause of such excessive deposit for rectification. Removal of such sticky dust may be done with brush, scrapers, compressed air or water. Use of water is the most effective method. ii. a. b. c. Procedure for Water Washing The openings to the shaft insulators and support insulators shall be covered prior to water washing to avoid any direct flushing on the inside of the insulators. The hopper outlet shall be kept open for easy discharge of water with out stagnation in the hopper. Hot water may be used for quicker dry up. The water shall be free from any chloride and other chemicals, which can cause corrosion. The quality of the water shall be analyzed and the record shall be maintained for future reference.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)d. The water pressure in the flushing equipment shall be maintained between 2-3 kg/cm2. Higher water pressure may induce stresses in the functional parts. The water shall be sprayed on to the internals through a simple nozzle system. The flushing shall commence from the top of the internals and proceed towards the bottom. All the fields in the casing shall be flushed. If a field is left unflushed high humidity inside the casing may leave sticky deposit in that field. Plant access doors to remain open to encourage draft flow to assist the drying process.

e.

f. g.

A 2: SHUT DOWN PROCEDURE FOR PULVERISER Pulverizer Shutdown The coal pulverizer can be shut down manually or automatically. Each coal pulverizer is shut down in the same manner. The manner in which the coal pulverizers are shut down, manually or automatically, is described in the following sections. Pulverizer Manual Shutdown The manual mode of operation must be selected for the pulverizer to be shut down. The MANUAL indication is on. A normal pulverizer shutdown sequence of events is as follows: 1. 2. 3. 4. 5. Place the adjacent oil elevation in service to provide furnace stabilization energy as the pulverizer is shut down. After the oil elevation is in service, reduce the feeder speed to the minimum setting. A hot air gate close command is generated when the operator activates the associated CLOSE push button. When this is done, the pulverizer air control is removed from automatic control. The hot air damper is closed, the cold air damper is opened to the 100% pulverizer airflow position and 30 seconds later, the hot air gate is closed. When the pulverizer outlet temperature is reduced below 54 C, shut down the feeder by activating the associated STOP push button. When the push button is released, a feeder stop pulse is established for three seconds. The start feeder command is removed. Two seconds later, the feeder start seal-in signal is removed and the feeder is stopped. (The OFF indication will come on and the ON indication will go off.) When the feeder is off, the following events occur: a. b. c. d. 7. The include feeder in totalizer circuit output to CLC is removed. The release feeder to auto output to CLC is removed. A three minute timer is started. The pulverizer ignition permissive is required for pulverizer operation until the three minute timer expires. A fifty second timer is started. When it expires, the associated elevation fuel air dampers are commanded to close.

6.

Allow the coal pulverizer to run until it is completely empty of coal. The pulverizer is

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)8. shutdown by activating the associated STOP push button. When the pulverizer is off, the following events occur: a. b. 9. 10. The close hot air damper to 0% output to CLC is established. The close cold air damper to 5% output to CLC is established.

If the pulverizer is to remain on standby, then the discharge valves should remain open to allow air to flow through the pulverizer. If required, the discharge valves are closed by activating the CLOSE push button. The pulverizer seal air valve should be left open to provide seal air flow to the pulverizer when not in operation. The seal air valves can be closed manually (for maintenance) by activating the associated CLOSE push button. The associated oil elevation can be shut down when the furnace and boiler conditions have stabilized.

11.

Pulverizer Auto Shutdown The auto mode of operation must be selected for the pulverizer to be shut down. The AUTO indication is on. An auto pulverizer shutdown sequence of events is as follows: The operator initiates a pulverizer shutdown sequence by momentarily activating the coal elevation STOP push button. The following events will occur: 1. 2. 3. The auto stop memory is established and the auto start memory signal is removed. A ten-minute elevation auto stop timer is started. If the pulverizer ignition permit is not established for the associated coal elevation, the adjacent oil elevation is placed in service. When the pulverizer ignition permit is satisfied and the oil elevation start time (120 seconds) has expired, the following commands are established simultaneously: a. b. Run feeder demand to minimum. The release feeder to auto signal to CLC is removed. The pulverizer hot air damper is closed and the cold air damper is opened to its 100 % airflow position. Thirty (30) seconds later, the hot air gate is closed.

When the pulverizer outlet temperature is reduced below 54C and the feeder demand is at minimum, the associated feeder will receive an auto stop feeder command. When the feeder is off for three minutes, the associated pulverizer will receive an auto stop pulverizer command. 4. 5. If the pulverizer is to remain on standby, then the discharge valves should remain open to allow air to flow through the pulverizer. If required, the discharge valves are closed by activating the associated CLOSE push button. When the ten minute auto elevation stop timer expires, an unsuccessful elevation shutdown condition is established if any of the following conditions exist:

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)a. b. The pulverizer is on. The feeder is on.

6.Oil elevation is shut down manually.OIL ELEVATION SHUTDOWN

Manual Shutdown An elevation of oil may be shut down by the operator only when a source of ignition energy is no longer required by any adjacent pulverizers. For For For For For For oil oil oil oil oil oil elevation A, this is coal elevations A & B. elevation B, this is coal elevations A, B, & C. elevation C, this is coal elevations B, C, & D. elevation D, this is coal elevations C, D, & E. elevation E, this is coal elevations D, E, & F. elevation F, this is coal elevations E, & F.

The oil loading should be reduced before the elevation is shut down. After the oil loading is reduced, the oil elevation is shutdown by the operator. The oil guns are removed from service in pairs. Activating the PAIR STOP push button for Corners 1 and 3 generates a stop command for Corner 1 followed in thirty (30) seconds by the stop command for Corner 3. Corners 2 and 4 are removed from service in a similar manner using the associated PAIR STOP push button. Oil Corner Shutdown The oil corner shuts down in the following manner: 1. 2. The oil valve is closed when the scavenge oil gun signal is established. The oil valve closed indication comes on and the open indication goes off. The HEA igniter receives an advance command and when proven advanced, the spark signal is established for thirty (30) seconds. Simultaneously, the scavenge valve is opened. After sparking for 30 seconds, the HEA igniter is retracted. When the scavenge valve is open, a 300 second scavenge timer is started. When the 300 seconds expires, the oil gun scavenge complete signal is established. The scavenge valve and the atomizing air valve are both closed.

3. 4.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)When both pair stop 360 second stop times expire, the following events occur: 1. 2. 3. The corner stop signals are removed. The associated oil elevations position air dampers for oil firing signal is removed. The elevation back-up trip signal is established for each oil gun corner on the associated oil elevation to maintain a shut down signal to each oil gun valve.

If any of the HEA igniter spark rods are not retracted, the unsuccessful spark rod shut down alarm is activated. If any oil valve remains not closed, the elevation unsuccessful shutdown alarm is activated Oil Corner Local Scavenge Each corner oil gun can be scavenged and shut down individually from the associated corner's local control station. This is accomplished by placing the local control station's selector switch in the SCAVENGE position. The oil gun is scavenged and shut down in the same manner as previously described. When the oil gun is scavenged and successfully shut down, the local control station's selected switch is removed from the SCAVENGE position and returned to the REMOTE position. Oil Corner Trip When an oil gun is in-service, it is automatically shut down without scavenging if a "corner trip" signal is established. The associated corner oil valve is closed. Any of the following conditions will establish a corner trip signal for the oil gun: 1. 2. 3. 4. The oil gun becomes not engaged. The local control station's selector switch is moved from the REMOTE position to the OFF position. The manual atomizing isolation valve is not open. The elevation back-up trip signal exists. When any of the following conditions are established. a. Light and Heavy oil trip valves not open. b. Master Fuel Trip. The oil valve is not open and no scavenge signal is established when the corner start time is expired. The discriminating scanner shows no flame when the thirty (30) second ignition trial time expires and there is no scavenge command or the atomizing valve is not open.

5. 6.

A3: MASTER FUEL TRIP An abnormal unit shutdown occurs when a master fuel trip signal is established. A master fuel trip signal is established when there is a boiler trip condition present after the furnace purge cycle has been completed.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)The master fuel trip is accomplished by closing the Oil Header Trip Valves and all corner oil valves. The pulverizers and feeders are also shutdown. When a master fuel trip signal is established, the following events will occur: 1. 2. 3. 4. 5. 6. 7. The Light and Heavy Oil Trip Valves are closed. All corner oil valves are closed. All pulverizers and feeders are shut down. All pulverizer hot air gates are closed. All pulverizer hot and cold air dampers are closed. The primary air fans are tripped. The fuel and auxiliary air dampers are opened and the auxiliary air dampers control is transferred to manual.

Any of the following conditions will establish a boiler trip command signal which will then generate a master fuel trip memory signal. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. Loss of any (unit) critical power. Loss of DCS control capability for more than ten seconds. Both ID (Induced Draft) fans are off. Both FD (Forced Draft) fans are off. Unit airflow is less than 25%. All feed water pumps are off for more than twenty seconds and loss of fuel trip arming. Furnace pressure is at the high trip set point. Furnace pressure is at the low trip set point. Loss of Reheat Protection. Both EMERGENCY TRIP (hard) push buttons are depressed simultaneously or the MFT (soft) push button is activated. Economizer inlet feed water flow low for more than ten seconds and loss of fuel trip arming. Evaporator tube metal temperature high for more than three seconds. Separator level high. Separator Pressure high. MFT Relay Tripped. Loss of fuel trip. A loss of fuel trip arming signal is established when any oil valve is open. After becoming armed, a loss of fuel trip signal will be established when all of the following conditions are present: a. b. c. d. 17. All feeders are off. The Light Oil Trip Valve is not open or all Light Oil Valves are closed. The Heavy Oil Trip Valve is not open or all Heavy Oil Valves are closed. All scavenge valves are closed or all feeders have been off for less than 185 seconds.

Unit No Flame Vote trip. The Unit Flame Failure trip is armed (ready to monitor for Unit Flame Failure) when

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)any feeder is proven. After becoming armed, a Unit Flame Failure trip exists when all twelve flame scanner elevations indicate a No Flame Vote as listed below: a. Elevation A indicates No Flame Vote when any of the following conditions are present: (1) Feeder A is off. (2) Both of the following conditions are present: Any oil valve not closed on elevation A. Two out of four oil guns not proven on Elevation A. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation A. Two out of four oil guns not proven on Elevation A. Elevation AB indicates No Flame Vote when any of the following conditions are present: (1) Feeder A and feeder B are off. (2) Less than two out of four scanners show flame on Elevation AB. Elevation B indicates No Flame Vote when any of the following conditions are present: (1) Feeder B is off. (2) Both of the following conditions are present: Any oil valve not closed on elevation B. Two out of four oil guns not proven on Elevation B. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation B. Two out of four oil guns not proven on Elevation B. Elevation BC indicates No Flame Vote when any of the following conditions are present: (1) Feeder B and feeder C are off. (2) Less than two out of four scanners show flame on Elevation BC. Elevation C indicates No Flame Vote when any of the following conditions are present: (1) Feeder C is off. (2) Both of the following conditions are present: Any oil valve not closed on elevation C. Two out of four oil guns not proven on Elevation C. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation C. Two out of four oil guns not proven on Elevation C. Elevation CD indicates No Flame Vote when any of the following conditions are present: (1) Feeder C and feeder D are off. (2) Less than two out of four scanners show flame on Elevation CD. Elevation D indicates No Flame Vote when any of the following conditions are present:

b.

c.

d.

e.

f.

g.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)Feeder D is off. Both of the following conditions are present: Any oil valve not closed on elevation D. Two out of four oil guns not proven on Elevation D. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation D. Two out of four oil guns not proven on Elevation D. Elevation DE indicates No Flame Vote when any of the following present: (1) Feeder D and feeder E are off. (2) Less than two out of four scanners show flame on Elevation DE. Elevation E indicates No Flame Vote when any of the following present: (1) Feeder E is off. (2) Both of the following conditions are present: Any oil valve not closed on elevation E. Two out of four oil guns not proven on Elevation E. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation E. Two out of four oil guns not proven on Elevation E. Elevation EF indicates No Flame Vote when any of the following present: (1) Feeder E and feeder F are off. (2) Less than two out of four scanners show flame on Elevation EF. Elevation F indicates No Flame Vote when any of the following present: (1) Feeder F is off. (2) Both of the following conditions are present: Any oil valve not closed on elevation F. Two out of four oil guns not proven on Elevation F. (3) Both of the following conditions are present: Less than two out of four scanners show flame on Elevation F. Two out of four oil guns not proven on Elevation F. Elevation FF indicates No Flame Vote when any of the following present: (1) Feeder F is off. (2) Less than two out of four scanners show flame on Elevation FF. Low waterwall flow after 10 seconds Air heater gas outlet temperature high temperature (1) (2)

h.

conditions are

i.

conditions are

j.

conditions are

k.

conditions are

f.

conditions are

18. 19.

A4: FIRST OUT CAUSE OF TRIP SYSTEM The first out cause of trip system will determine the first cause of a boiler trip. The first cause of a boiler trip will be retained in memory and indicated on the CRT. All subsequent boiler trip commands to the first out cause of trip system will be blocked. Any boiler trip condition that initiates a master fuel trip will activate the first out boiler trip system. The No Boiler Trip Command indication will go out. The Boiler Trip conditions will be alarmed.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)When the cause of the boiler trip is corrected and no other boiler trip conditions exist, the No Boiler Trip indication will come on. A purge cycle can be initiated by the operator when the Purge Ready indication comes on. When a five minute furnace purge cycle has been completed and the No Master Fuel Trip indication comes on, then the first out trip systems memory will be reset. The first out cause of boiler trip indication will go off.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)B : STEAM TURBINE SHUT DOWN PROCEDURENormal Shut-Down 1. 2. Except in an emergency shut-down, load must be removed gradually as per manufactures recommendation for load changes. At approximately 15% of rated load, open all turbine drains except reheat steam inlet piping drain. Reheat steam inlet piping drain shall be opened at approximately 7% of rated load. When all load has been removed, shut-down the unit by tripping either manually of remotely. This closes all the turbine main steam and reheat inlet valves and disconnect the generator from the line, and opens the field circuit breaker. If the turbine is still providing load, then the bypass valves will open. Make sure that Turning oil pump starts when the bearing oil pressure drops below 0.83 barg. Generator instruction book should be followed regarding water supply to hydrogen coolers. In order that the turning gear will be remotely engaged, be sure that the rotor speed is below the turning speed before the control switch is turned to the START POSITION. This will also supply oil to the turning gear. Open the vacuum breaker when the turbine speed reaches about 400 rpm. Shut-down the air removal equipment. When the vacuum has reached zero, shut-off sealing steam from the main steam header to the gland steam regulating valve and shut-down the gland steam condenser exhauster. Shut-down the condensate pumps. Shut-down circulating water pumps. Regulate water to the oil cooler to maintain the temperature of the oil leaving the coolers between 35C and 40C, if possible. Loss of Electrical Tie to the System In the event of the complete or partial loss of electrical load, energy in the entrapped steam will cause the rotor to accelerate. The amount of accelerate is a function of the load level at the time of the load separation. 1. The over speed protection control (OPC) function senses excess turbine speed and closes all governing and interceptor valves when the speed is greater then predetermined valve. When the speed of the unit decreases towered rated speed after

3.

4. 5. 6.

7.

8. 9. 10. 11.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)the steam entrapped in the reheat system is dissipated, the interceptor valves return to open. 2. If desired, the unit may now be resynchronized and load applied as follows: a. b. c. 3. If the unit can be synchronized and loaded within 15 min., increase load as quickly as possible. If there is more than 15 min. delay in synchronized, load should be applied. If it is decided not to put unit back on the line, the normal shut-down procedure outlined above should be followed.

If the cause of the load dump cannot be determined, resulting in a delay in resynchronized, the unit should be tripped automatically after a specified time delay, the shut-down procedure described below under Loss of Pressure of Temperature should then be followed. Loss of Pressure or Temperature Under normal operation the IPR (Initial Pressure Regulator) will be in operation and will function as follows: a. b. For any sustained pressure drop in the boilers the initial pressure regulator will cut in at a predetermined value. After the initial pressure regulator has cut in the load will be reduced until the throttle pressure is increased to the initial pressure regulator set point or a minimum valve opening of 20% is reached. During this period, the operator should decide whether the operating temperature and pressure can be maintained. If the boiler pressure increases sufficiently, the operator can increase the Reference setting to the load value held before the decrease of pressure.

12. 1.

c. d. 2.

If the IPR (Initial Pressure Regulator) set point is lower than 90% of normal operating inlet pressure of the IPR is out of service, the following procedure shall be followed: a. b. The operator will begin to reduce load in an attempt to maintain pressure above 90% of normal and throttle and reheat temperature drop to not more than 83C. If the pressure falls below 90% of normal or temperature drops 83C, remove the load and trip the unit. All turbine drain valves will open automatically when the load has decreased to 15%. Check by-pass valves around traps on all drain lines from stage extraction heaters. Place unit on turning gear and listen for rubs. For the case where the pressure can be held above 90% of normal manner after temperature drop to less than 83C bring the unit up in normal manner after temperature and pressure have been restored to normal.

c.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)13. Protective Devices Function 1. This unit is equipped with protective devices, which trip the unit in the event of low vacuum; low bearing oil pressure; thrust bearing failure, vibration, eccentricity, and differential expansion. In addition a generator trip will also trip the turbine. In addition the unit can be tripped, either with the trip solenoid or with the hand trip lever. The situation can also arise whereby the unit is inadvertently tripped in the process of testing the protective devices if the over speed trip test lever is released prematurely. 2. In the event the unit is tripped as noted in 1. above, and the trouble has been recognized, cleared and the vacuum maintained, reset the protection, run the unit back to speed and proceed to synchronize. If in the event of a trip and the vacuum is lost, let the unit come to rest, following the normal shut-down sequence. After the trouble is corrected, restart the unit in accordance with the normal starting sequence.

3.

B1 :Turbine Shut-down of extensive repair or adjustment:Both the turning gear and bearing oil circulation systems are to be kept in operation for a minimum of 12 hours; oil temperature from the cooler should be maintained between 35 and 40C, if possible. Both the turning gear and the oil circulation may then be shut-down. If operation of the unit is to be resumed before the turbine is thoroughly cooled, the turning gear should be started 3 4 hours before rolling the unit and steam.

B2 :Turbine Shut-down for minor repair or adjustment:Depending upon the nature of the work to be done, the following schedule may be adopted:1. Keep the turning gear and bearing oil circulation systems in operation for a minimum of 3 hours. Both systems may then be shut-off for a period of not more than 15 minutes; if practical, however, oil circulation should be maintained. 2. Immediately thereafter roll the turbine on turning gear for at least 2 hours. Both turning gear and oil circulation may then be stopped for not over 30 minutes; however, 15 minutes after stopping the rotor is to be turned 180 with the turning gear. The 180 turn may be made without oil circulation, if unavoidable.

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Plant Shut Down Procedure for SDSTPS Unit # 1&2 (BOILER AND STEAM TURBINE GENERATOR)3. Following the 30 minute shut-down period in (2) above, the turbine should again be rolled on turning gear with oil circulation for a minimum of 2 hours. The system may then be shut-down indefinitely, provided that at 30 minute intervals for the next 6 hours the rotor is turned 180. These 180 turns may again be made without oil circulation if necessary. In any case, if the turning gear has been disengaged, it should be put in operation a sufficient time before admitting steam to the unit to allow the rotor to become straight within a limit of approximately 0.025 mm on the truth indicators.

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