Discussion on the problem of pump evacuation
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There is a pump in our factory, one is on and the other is on standby. Whenever the pump is switched off, it is easy to cause the other pump to evacuate. We analyzed this situation and found that each of our two pumps has a gate valve at the inlet. The gate valve is installed horizontally on the inlet pipeline. We plan to install the gate valve vertically to reduce cavitation. I wonder if this will work?
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If you close the outlet valve first and then switch it, won't it cause emptying? There is no problem if the outlet valve is closed within an hour, but cavitation is a big problem. So you can consider it.
Under normal circumstances, there should be no evacuation when pouring the pump according to the pump pouring procedures, unless the design is unreasonable (the inlet main pipe is too thin and cannot operate two pumps at the same time)! On the other hand, butterfly valves are sufficient for the inlet valves. Gate valves are a bit wasteful and not easy to open and close!
1. A check valve should be installed in front of each pump. 2. Or close the outlet valve of the working pump before switching pumps. Start the backup pump and then stop the pump that was started first.
When cutting the pump, open the outlet valve while closing the inlet valve of the other pump to keep the outlet pressure and flow rate unchanged. Generally, this phenomenon will not occur. It has nothing to do with valves or anything.
I can’t say whether it can be solved, but our pump inlet valves are all installed vertically. In addition, it is unreasonable to use a butterfly valve for the inlet valve, because the pump will not be empty when it needs repair. :handshake
Cavitation should be caused by improper operation, such as not shutting down the running pump in time after starting the backup pump.； The diameter of the pump inlet header is too small, etc.
It may be caused by improper operation. When cutting the pump, it is best to ensure that the flow rate is stable, at least not to exceed the original flow rate too much. It has nothing to do with the valve, unless the inlet valve is not fully opened when the pump is turned on.