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 circulating pump normal Kai, stop has such a requirement: (1) the circulating pump outlet butterfly valve interlock switch to "put" position; (2) operating cycle pump control switch, Check the circulation 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 The method starts and stops the circulating pump, there is a great potential accident, affecting the safe operation of the unit, due to circulating pump failure, condenser cooling water interruption, resulting in a number of unit tripping example: (1) a power plant 4 (300 MW), the No. 6 circulating pump was increased during the load-up period. After the butterfly valve was opened, the No. 6 circulating pump was started unsuccessfully, and the low vacuum protection action of the generator set tripped the generator and caused the shutdown of the generator 3.38 h. Main reasons: When the on duty pump starts circulating pump No. 6, the control switch is switched to the starting position and the outlet butterfly valve is interlocked to open. However, due to the defect of the control circuit, the circulating pump motor is not started, the circulating pump is reversed and the cooling water of the condenser is drastically reduced, resulting in low Vacuum protection action, unit trip (2) 2002-10-01, a power plant 2 (125 MW) peak outage standby, stop circulating water No. 1 Press the stop button, the outlet butterfly valve is not interlocked closed, but the circulating pump has stopped and quickly reversed, as the unit has been shut down, no loss. (3) 2003-02-15, a power plant Unit 1 (125 MW) When doing regular switching work, start standby pump No. 1, the control switch to the starting position, the outlet butterfly valve interlock to open, but the circulating pump does not start, but reversed, because the attendant found timely and immediate closure of the circulating pump inlet butterfly valve (4) 2003-06-19T07: 00, a power plant on the 4th machine (300 MW) to switch the circulating pump No. 2 on a regular basis, start circulating pump No. 2, the outlet of the butterfly valve is very open Slow, and open to 25% stop, the pump appears reversed, causing the vacuum drop sharply.The above four examples, although all due to the control loop defects caused, but as long as the change of operation method can be avoided when the unit is in normal operation , Manual normal switching cycle pump operation to make the following changes: Kai pump operation: (1) the circulating pump outlet butterfly valve interlock switch to "exit" position; (2) (3) manually open the circulating pump outlet butterfly valve; (4) the circulating pump outlet butterfly valve interlock switch to "put" position; stop the pump operation: (1 (2) Turn off the butterfly valve at the outlet of the circulating pump to check if it is closed normally; (3) Turn on the pump control switch of the circulating pump to stop the pump; (4) If it switches normally and stops After the standby state, 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 outlet butterfly valve control circuit defects, but also to avoid the condenser cooling Reduced water caused by the unit low vacuum protection 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.