On the operating rules of the circulating pump start and stop the provisions
Circulating water pump is an important power plant thermal equipment, circulating pump start and stop operation in the power plant is often seen, Kai, stop is normal, affecting the safe operation of the unit. According to the investigation of the nine power plants on the normal circulation pump, start and stop have such a requirement:
(1) Turn the butterfly valve interlock switch of the circulating pump to "put" position;
(2) operating cycle pump control switch, check the circulating pump start or stop normal;
(3) Check the circulation pump outlet butterfly valve interlock open or closed normally.
This method of operation is based on "When operating the circulating pump control switch, the linkage of its outlet butterfly valve function.I think: When the unit is running, the circulating pump and its outlet butterfly valve control circuit is most likely flawed, according to this operation Methods start and stop the circulating pump, there is a big hidden danger of accidents, affecting the safe operation of the unit, due to circulating pump failure, condenser cooling water interruption, resulting in a lot of examples of unit trips. Such as:
(1) a power plant on the 4th (300
MW) After starting the grid connection, the No. 6 circulating pump is increased during the load-up period. After the butterfly valve is opened, the No. 6 circulating pump is not started successfully, and the low-vacuum protection action of the unit is triggered. The unit is tripped and the unit is stopped. 3.38
h The main reason: when on duty to start on the 6th circulating pump, the control switch to the starting position, the outlet butterfly valve interlock to open, but because of the control loop there is a defect, the circulating pump motor does not start, the circulating pump reversal, the condenser cooling water drastic Reduce, resulting in low vacuum protection action, crew trip.
(2) 2002-10-01, a power plant on the 2nd machine (125
MW) peak stop off standby, stop circulating pump No. 1 at the stop button, the outlet butterfly valve is not interlocked closed, but the circulating pump has stopped and reversed quickly, as the unit has been out of service, did not cause any loss.
(3) 2003-02-15, a power plant No. 1 machine (125 MW) in the regular switching work, start No. 1 standby circulating pump, the control switch to the starting position, the outlet butterfly valve interlock to open, but the circulating pump Did not start, but reversed, due to the attendant found timely and immediate closure of the circulating pump inlet butterfly valve and load, to avoid the low vacuum protection.
(4) 2003-06-19T07: 00, a power plant on the 4th (300
MW) The circulating pump No. 2 is switched on a regular basis. When the No. 2 circulating pump is started, its outlet butterfly valve opens very slowly and stops when it reaches 25%. The pump reverses causing the vacuum to fall sharply.
The above four examples, although all due to the control loop defects, but as long as the change of operation method can be avoided. When the unit is in normal operation, make the following changes to the operation of manually switching the circulation pump manually:
Pump operation:
(1) The circulating pump outlet butterfly valve interlock switch to "exit" position;
(2) operating cycle pump control switch to start the pump, check the circulating pump does start normal;
(3) Manually open the circulating pump outlet butterfly valve;
(4) Turn the butterfly valve interlock switch of the circulating pump to "put" position;
Stop pump operation:
(1) The circulating pump outlet butterfly valve interlock switch to "exit" position;
(2) Turn off the circulating pump outlet butterfly valve, check the normal closed;
(3) operating cycle pump control switch to stop the pump;
(4) If the normal switch and stop in standby mode, then the circulating pump outlet butterfly valve interlock switch to "put" position.
According to the modified method of operation, even if the circulating pump or its outlet butterfly valve control circuit defects, but also to avoid the condenser cooling water caused by low vacuum protection unit action. Of course, before the start of the unit or after stopping the operation of the circulating pump, you can first put the outlet butterfly valve interlock switch input, and then operate, so you can determine the outlet butterfly valve linkage function is normal.
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