Issues with high-speed pump switching
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What was seen just now: the steps for switching between high-speed pumps (one pump running while the other is shut down). The outlet valve of the running pump is opened fully, so that its pressure can overcome that of the standby pump. When the standby pump has its outlet valve opened fully and starts up, the flow rate is low and the current is low as well. Once the current stabilizes, the running pump is shut down, completing the switch. When the standby pump has its outlet valve opened fully and starts up, will the flow rate be low and the current low as well? I’m a bit skeptical! Is this the usual way people cut high-speed pumps? When we start the pump, we open the outlet valve to about a 3-octave setting – could there be an error in the operation?
When switching high-speed pumps, there is backpressure in the outlet pipeline of the standby pump; therefore, the outlet valve is opened fully, resulting in a low starting current. Additionally: If the pump is started with the outlet valve closed, internal boiling may occur if the outlet valve is not opened in time, causing the pump to vibrate and damaging the mechanical seal. If the high-speed pump is started alone, it must be taken into account that the outlet valve cannot be fully opened; otherwise, the flow rate will be too high, the current will be excessive, and the motor will trip. Therefore, when a high-speed pump is started alone and the back pressure in the pipeline is not high, the outlet valve only needs to be opened to 1/3 of its opening degree during startup
Could starting the backup pump result in excessive flow, thereby affecting the process operations?
It seems so messy... Doesn’t the high-speed pump have a minimum flow rate setting? Just use that setting; it’s not necessary to open the outlet to three turns. If there’s no such minimum flow rate setting, then it’s fine to open it fully. The pump inlet is fully open; the outlet is also fully open at start-up. Will the motor overheat and get damaged due to excessive current when the motor starts?
It’s normal for the current to be low when the second unit is turned on; the flow rate can’t keep up. Turn on both at the same time, and then slowly close the outlet valve of the pump that needs to be stopped
If the high-speed pump starts automatically, the inlet and outlet valves of the standby pump must be fully open. If it is the first start-up, the flow rate should be set to the minimum allowable level; generally, the minimum flow rate specified by the manufacturer is lower than what is necessary in practice, so the flow rate should be adjusted according to actual conditions. If the outlet is set too small during the first start-up, the vibration level of the pump will be very high, and internal boiling may even occur, damaging the mechanical seal.