Centrifugal pump cavitation problem
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One of our maintenance requirements required that after the system was depressurized and the pump was shut down, the centrifugal pump was restarted and the pump's own suction was used to draw negative pressure at the pump inlet. However, since there was very little material in the system, in order to prevent pump cavitation, the opening of the pump outlet valve was reduced to 7%. What is the principle of this? Not too clear.
The centrifugal pump itself does not have self-priming ability. I don’t know what basis your question is based on. Everyone is welcome to express their opinions.
I don’t quite understand. Can you explain it in more detail?
When the centrifugal pump is running, isn't it possible to generate a period of low pressure at the pump suction inlet so that the material can be sucked in? At that time, there was very little material in the system, the bypass branch of the pump inlet pipeline leaked, and the valve upstream of the bypass branch was closed. The main pipeline was running normally, but the pump outlet valve was closed small. I don't quite understand what this means, so I'm asking you guys to tell me.
Your pump inlet bypass is leaking, although it is closed. However, when the main pipeline is operating normally, some gas will be sucked in from the bypass, causing instability in the operation of the pump. The purpose of closing the outlet valve is to discharge the inhaled gas from the outlet as much as possible to avoid further cavitation of the pump.
There are two considerations for shutting down exports.: 1. The system has less materials and needs to be reduced. ； 2. The pressure of the pump is not enough. Turning it down can increase the outlet pressure.
At this time, the amount of material at the pump inlet is very small. This operation is mainly to clean the material in the storage tank as much as possible, not just to solve the problem of cavitation. At this time, the amount of material sucked in by the pump inlet is too small. The purpose of closing the pump outlet valve is to control the outlet flow and prevent the pump inlet from being sucked empty and causing the pump to fail to pump volume.
Artificially changing the pump flow rate converts the kinetic energy of the fluid into static pressure energy. Prevent the occurrence of cavitation and improper inspection of the pump.
There seems to be something in this regard in the centrifugal pump maintenance regulations.