For shielded pumps, what are the detailed steps for shutting down a shielded pump? It’s the type that cannot have its flow interrupted

Reply to 1# li*aolong602: First, open the inlet valve of the other pump. After the pressure builds up, open the outlet valve. Then, you can turn off the first pump!

Start the backup pump and contact the operators in relevant positions to prepare for starting it. Activate the motor of the backup pump; stop the startup immediately if any of the following occur: abnormal leakage from the pump, abnormal vibration, unusual odors, abnormal noises, sparks, smoke, or persistently high current levels. Confirm that the pump outlet has reached the start pressure and is stable, then switch to and start the backup pump following the proper procedure for starting a pump. After powering on the pump being switched in, gradually open its outlet valve while closing the outlet valve of the pump being taken out of service. Once the flow rate and pressure of the newly activated pump become normal, fully close the outlet valve of the decommissioned pump and then cut off its power supply. Close the pressure gauge valve. For pumps used to transport viscous liquids, after shutting down the pump, it is necessary to open the drain valve at the lowest point of the pump during winter in order to drain all the liquid, preventing it from freezing inside the pump.

The meteorological balance tube of the shielded pump must not be clogged, and the pipeline must be free of impurities; otherwise, the graphite bearings are prone to sticking

The most important thing regarding shielded pumps is to prevent them from running idle; they are lubricated by the material itself. When operating the pump, it is necessary to first open the inlet valve and close the outlet valve in order to pump the material from the tank, thereby avoiding air entrainment. Pump the material from the tank for five minutes, then start the pump – that’s all that’s needed

There must be no interruption in flow; this is especially important for pumps that transport materials outward. To avoid disrupting the normal operation of other processes, the standby pump should be started first. Once the standby pump becomes stable, the originally operating pump can then be shut down. The startup procedure for the pumps remains the same as per the operating instructions for canned pumps.

Operating Procedures for Shielded Pumps 　　　 I. Checks before startup: 　　　 1. The insulation resistance must be above 2 MΩ. 　　　　2. Check whether the rotation direction of the motor is consistent with the direction of the arrow on the pump casing. 　　　　3. Check whether the bearing monitor is pointing to the designated area; if the pointer points to the red indicator band, it indicates an abnormality. 　　　　4. Check whether all fastening components are secure, whether the pressure gauge and cooling water are functioning properly, and whether the outlet valve and the pump’s exhaust valve are closed with no leaks. 　　　　5. Check whether the cooling water is flowing. 　　　　II. Pump startup: 　　　　1. Fully open the inlet valve and slightly open the bypass valve to remove air from inside the pump. At the same time, the reverse circulation valve is opened fully to fill the pipeline with liquid. 　　　　2. Start the pump, open the bypass valve, and fully discharge the gas from within the pump. 　　　　3. After exhaust is complete, gradually close the bypass valve, check whether the outlet pressure gauge shows the specified pressure, and then slowly open the outlet valve to bring the discharge volume to the flow rate at the operating point. 　　　　4. Adjust the valve of the reverse circulation tube to keep the reverse circulation rate within the range of 8–15 l/min, while checking whether the liquid inside the glass sight glass is flowing adequately. 　　　　5. During operation, pay attention to the pressure difference before and after the coarse filter; if this difference increases significantly, it is necessary to reverse the pump’s direction of operation. 　　　　III. Shutting down or switching pumps 　　　1. Start the standby pump following the startup procedure, then slowly close the outlet valve. Meanwhile, monitor the operation of the standby pump to ensure there are no abnormalities, and finally close the outlet valve completely. 　　　　2. Press the stop button to shut down the pump; 　　　　3. Close the outlet valve; 　　　　4. Stop the cooling water supply.

Passing by Xue*, thanks to the original poster for the question

Reply to 1# li*aolong602: Start the standby pump, gradually open its outlet and return valve, while simultaneously gradually closing the outlet and return valve of the operating pump; this way, there will be no interruption in flow.