Normal shutdown

1.2.1 Confirm DEH is in “Operator Auto” mode; confirm ”lower limit of initial steam pressure” is released.

1.2.2 Open the sub-picture of set value control on the main control picture of DEH to set the target load at 110MW, and set the load down rate at 1.25MW//min by turning down the governing valve in the condition of holding steam temperature and pressure, then press the button “GO” to make the unit load start to decrease. At the same time, the main operator shall decrease the temperature and pressure according to normal shutdown curve.

1.2.3 When the load decreases to 110MW, press button “HOLD” with the initial steam temperature to 500℃, reheat steam temperature to 480℃, initial steam pressure to 11Mpa and HP stator lower carrier metal temperature to 455 .℃

1.2.4 Table of load, steam temperature & time at normal shutdown Load MW

Item 135 110 75 54 5.4 0

Time (min) 20 51 60 71 72

Initial steam temperature ( )℃ 535 500 474 472 466 465

Reheat steam temperature ( )℃ 535 480 452 450 445 444

HP stator lower carrier metal temperature ( )℃ 496 455 415 410 400 398

1.2.5 Decrease the parameter and load according to the normal shutdown curve at the rate of initial steam temperature of 1.5 /min, reheat steam temperature of 2.5 /min and initial steam℃ ≯ ℃ pressure of 0.05Mpa/min.

1.2.6 Open the sub-picture of set value control on the main control picture of DEH to set target load at 75MW and load down rate at 1.13MW/min, then press “RATE” and “ENTER” button; press

1.2.7 When the differential pressure between HP heater #2 steam side and deaerator is <

0.3MPa, stop the HP heater steam side from high to low; close the drain motor-operated valve of deaerator, change HP heater water drain to the condenser; close HP heater #1 and #2 to the deaerator air valve and close the air inlet value of HP; open the drain valves before and after extraction check valve of No. 1 and 2.

1.2.8 When No. 3 extraction pressure decreases to 0.25MPa, check if the auxiliary steam header’s steam supply valve is opened, close the No. 3 extraction to deaerator air inlet valve;

make the deaerator run at constant pressure of 0.192Mpa.

1.2.9 Set the target load at 54MW, load down rate at 2.33MW/min and the unit load continues to decrease; when the load decreases to 54MW, the initial steam temperature decrease to 472 ,℃ reheat temperature to 450 and HP stator lower carrier metal temperature to 410 .℃ ℃

1.2.10 When the load decreases to 45~60MW, stop the LP heater drain pump and open LP heater #6 l to multistage water-seal inlet and outlet valve; change LP heater #6 drain water to condenser

1.2.11 Set the target load at 5.4MW, load down rate at 4.42MW/ min, and the unit load continues to decrease.

1.2.12 When feed water flow decreases to 132m³/h, check the feed-water recirculation valve that shall open automatically, otherwise open it manually. In the process of load decrease, check if the shaft seal steam supply pressure is not less than 0.08 Mpa, adjust the shaft seal attemperating water and maintain the shaft seal steam supply temperature within specified range.

1.2.13 When the load decreases to 40MW, put the auto control of HP & LP bypass according to the requirement of boiler.

1.2.14 Open the attemperating water valve of proper drain flash tank. Close the air inlet valves of LP heater #4~#6.

1.2.15 When the load decreases to 27MW (20％ of rated load), the drain valves of LP part shall open automatically, otherwise open them manually.

1.2.16 When the exhaust temperature is ≥ 80 , check if the LP cylinder water spray starts to℃ operate automatically

1.2.17 When the load decrease to 13.5MW (10％ of rated load), the drain valves of HP part shall open automatically, otherwise open them manually.

1.2.18 When the load decreases to 6MW, the initial steam pressure decreases to 1.57~2.06Mpa, initial steam temperature to 466 , reheat temperature to 445 and HP stator lower carrier metal℃ ℃ temperature to 400 , prepare to shut down the unit. ℃

1.2.19 Set the target load at 0 MW and load down rate at 5MW/ min, and the unit load continues

to decrease to zero.

1.2.20 Start AC lubricating oil pump, advise electrical personnel that the generator can be paralleled off, at this time the steam turbine and boiler shall interlock trip (press the button “OFF”

to trip them in special case). Check HP & MP main stop valve, governing valve, extraction check valve and exhaust check valves of HP cylinder A & B that shall close all; unit speed decreases.

1.2.20 Works to done during unit idle time

1.2.20.1 Check the condition of unit idling, listen to its internal sound and record the idle time;

1.2.20.2 When the rotating speed is 2,500r/min, close the air valve of condenser; when the rotating speed is 1,500r/min, check if the jacking oil pump opened automatically, if not, open it manually;

1.2.20.3 When the rotating speed is 300~400r/min, open the vacuum breaker valve to decrease vacuum degree, control the rotating speed to “0” and vacuum to “0”; stop the shaft seal motor, stop the shaft seal steam supply and close isolating valve; stop the vacuum pump.

1.2.20.4 When the unit comes to rest, put the continuous turning into operation and record the shaft bending and turning gear current.

1.2.21 Operation after shutdown

1.2.21.1 Check HP & LP bypass that shall stop and exit.

1.2.21.2 Close the cooling water valve of oil cooler and air cooler, close the attemperating water valve of feed water pump and open the oxygen exhaust valve of deaerator to decrease the pressure to zero.

1.2.21.3 When boiler is filled with water, stop the feed water pump, stop the deaerator heating and close the isolating valve.

1.2.21.4 Open the recirculation of condensate pump and adjust the water level of deaerator and condenser.

1.2.21.5 When the exhaust hood temperature is <50 , stop the circulating water pump with℃ approval of unit supervisor.

1.2.21.6 When the exhaust hood temperature <50 , stop the condensate pump with approval of℃ unit supervisor.

1.2.21.7 When the HP carrier lower half metal temperature is <150 , stop continuous turning.℃ 1.2.21.8 When the rotor comes to rest; release the interlocking of oil pump and stop the jacking oil pump and AC lubricating oil pump.

1.2.22 Precautions in normal shutdown

1.2.22.1 In the process of shutdown, keep the initial and reheat temperature within normal range as much as possible that shall not be lower than 450 minimally.℃

1.2.22.2 In the process of load down, pay attention to the change in differential expansion of HP

value continues to increase, take measures to reduce the load quickly to zero for shutdown.

1.2.22.3 When the vibration at unit idling increases, reduce the vacuum degree to make the unit speed lower quickly.

1.2.22.4 After the unit shuts down and before the boiler, deaerator and auxiliary steam header release pressure completely, closely monitor the metal temperature of steam turbine to prevent steam & water from escaping into the steam water.

1.2.22.5 If discover exhaust cylinder temperature increases after shutdown, find out the cause and cut off steam source, or else start the condensate pump and put the LP cylinder spray into operation to reduce the exhaust cylinder temperature. After shutdown, pay attention to monitoring the water level of condenser and deaerator to prevent overfeed of water.