Centrifugal pump start and stop and precautions

The three processes of starting, running, and stopping of centrifugal pump are critical to the proper operation of the equipment itself and the entire workflow.

Next, we will sort out the common pump start-stop operation steps and matters needing attention during operation.

Preparation before the pump starts

1. Irrigation pump (except for the submerged pump, before the other pumps are started (the first time the self-priming pump is started), the pump should be pumped (that is, the pumping medium must be filled with the pump chamber))

2. Irrigation device pump: Open the shut-off valve of the inlet line, open all the exhaust lines, discharge the gas, slowly rotate the rotor, and close the exhaust valve when there is no air bubble in the pumping medium.

3. Suction device pump: open the inlet line to close the valve, open all the exhaust lines, discharge the gas, inject the pump (the suction tube must have the bottom valve), slowly rotate the rotor, when the pumping medium has no air bubbles , close the exhaust valve.

4. Open all auxiliary systems and require all auxiliary systems to work for at least 10 minutes. Wait until the entire auxiliary system is stable before proceeding to the next step. The auxiliary system includes lubricating oil system, sealed flushing system, cooling and insulation system. Wait;

5. Check whether the equipment rotates flexibly on the equipment; jog the motor and judge whether the pump rotates in the correct direction; confirm the coupling guard after fixing.

6. (The pump with the dry gas sealing system) The dry gas sealing system is used. Open the nitrogen inlet valve and pressurize the sealed chamber. The dry gas seal source pressure must be between 0.5 and 1.0 MPa. Each pump adjusts the pressure and flow of the seal chamber according to specific requirements.

Pump start

1. Confirm that the suction valve is fully open, the discharge valve is closed or slightly open; when there is a minimum flow line, the discharge valve is fully closed and the minimum flow valve is fully open.

2. Close the outlet line stop valve (must ensure minimum flow);

3. Start the motor to make the pump rotor reach the running speed;

4. Slowly open the outlet valve so that the outlet pressure and flow rate of the pump reach the specified value. When opening the outlet valve, check the motor current change to avoid overloading the motor. When the flow rate increases, attention should also be paid to whether the pump seal has abnormal leakage, whether the pump vibration is normal, whether there is abnormal sound of the pump body and the motor, and changes in the outlet pressure, such as abnormal leakage of the pump, abnormal vibration, Abnormal noise or outlet pressure is below design value and the cause should be identified and disposed of.

5. When the pump is running normally, check the outlet pressure, outlet flow, motor current, temperature of the bearing and seal, the oil level of the lubricating oil, the vibration of the pump, the noise and the leak at the seal; (depending on the process) Minimum flow bypass valve. Make a record of the relevant equipment operation.

Note:

1, The maximum starting frequency of the pump should not exceed 12 times/hour;

2, The pressure difference cannot be lower than the design point, nor can it cause fluctuations in performance parameters in the system. The pump outlet pressure gauge value is equal to the differential pressure plus the inlet pressure gauge value;

3, The reading on the ammeter at full load ensures that the current does not exceed the value on the motor nameplate;

4, The motor of the pump belt may be selected according to the requirements of the buyer according to the actual medium specific gravity. When performing the test run, the power of the motor should be considered. If the actual medium specific gravity is smaller than the specific gravity of the test running medium, please strictly control the opening of the valve during the test run to avoid overloading or even burning the motor. Always contact the YANESS if necessary.

Pump stop

1. Slowly close the small discharge valve until the flow reaches the minimum flow.

2. Turn off the power, stop the pump, and close the outlet valve.

3. When the minimum flow bypass line is provided, close the discharge valve when the bypass valve is fully open, and then cut off the power to stop the pump. The high temperature pump should stop circulating water when the temperature is below 80 °C; the sealing system (flushing liquid, sealing gas) should be stopped after 20 minutes of pump stop.

4. Spare pump: The suction valve is fully open, and the discharge valve is fully closed (when the minimum flow bypass line is provided, the bypass valve is fully open and the discharge valve is fully closed), so that the pump is in a state of full suction pressure. The cooling water of the backup pump should continue to be used to keep the lubricating oil level below the specified oil level. Pay special attention to inspection in winter, keep the heating line and cooling water unblocked, and avoid freezing.

5. The spare pump should be driven according to the regulations.

6. (After stopping) the pump that needs to be repaired. After stopping the pump (cooling), first close the nitrogen inlet valve of the dry gas sealing system, depressurize the sealed chamber, and then completely drain the liquid in the pump and the cooling water in the cooling system to make the pump body The pressure drops to zero, the remaining material in the pump is purged, all valves are closed, and the substation is disconnected from the power supply. On-site processing is required to meet HSE requirements.