If the inlet diameter of a pump is smaller than the outlet diameter, will cavitation occur?
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This post was last edited by Hallond on 2010-1-3 at 16:10. The pump in question has an inlet pressure of 100 and an outlet pressure of 125; when the inlet and outlet valves are fully open, there is some vibration, but it’s not very noticeable. The process currently aims to reduce the flow rate; when the inlet valve is closed to adjust the flow, severe vibration is observed. I would like to ask whether cavitation can occur in such a situation? Please discuss this: I believe that closing the valve partially will increase the flow velocity of the fluid entering the system, which in turn impacts the impeller and causes vibration. It should be noted here that this pump was originally a centrifugal pump with a low flow rate; now, a pump with a higher flow rate has been installed in its place.
Severe operation error! ! ! To reduce the flow rate, some outlet valves should be closed; it is strictly prohibited to use inlet valves to adjust the flow rate! ! ! Closing the inlet valve will inevitably cause cavitation in the pump! ! !
It’s possible. Generally, to increase the cavitation margin and prevent cavitation, the inlet is made larger than the outlet; this also depends on the type of fluid in use
This pump is also designed in a strange way; could you tell me the manufacturer? In principle, the pump inlet should be at a higher level than the outlet. It is strictly prohibited to operate the inlet valves on pump equipment; they must remain fully open.
There are many causes of cavitation; for example, whether the medium reaches its boiling point at the temperature you have set, and whether the medium tends to accumulate and block the pipes, thereby reducing their diameter； Is the layout of the inlet pipes reasonable? There should not be too many elbows ； The flow rate at the pump inlet must be sufficient ； Whether the export is smooth or not, etc. Cavitation problems are sometimes caused by various factors, and it is necessary to conduct a thorough analysis to identify and eliminate them. It is recommended that you adjust the flow rate rather than using an inlet valve for that purpose.
In my opinion, the method used to regulate flow rate is inappropriate; it’s rare to hear of flow regulation being achieved using inlet valves. If possible, please send a photo of the pump so I can learn from it!
There is a net positive suction head; as long as it isn’t exceeded, there will be no problems. In other words, the inlet temperature of the pump must not be too high ； Ways to reduce flow rate **small outlet valve**
What type of pump is this? Is it a centrifugal pump?
How can flow be regulated using the inlet valve? It should be regulated using the outlet valve.
It is incorrect to use the inlet valve to regulate the flow rate; there may be other reasons for the vibrations, which depend on the operating conditions. Is it really necessary to replace the pump just because of low flow rate?
It has to be said that none of your opinions are correct! 1 \"The pump inlet is 100 and the outlet is 125.\" Generally, the inlet diameter should be larger than that of the outlet; I’m not sure what rules govern this. 2 “When the inlet and outlet valves are fully open, there is some vibration, but it’s not very noticeable”; cavitation may be a possibility. And it is related to the small size of the inlet pipe! 3 “Currently, the process aims to reduce the flow rate; when the inlet valve is closed to adjust the flow, severe vibration is observed.” Cavitation has occurred, and this approach is completely incorrect. The flow rate should be adjusted only by controlling the outlet valve, while the inlet valve should remain fully open. 4. “I personally believe that closing the valve partially will increase the flow rate of the fluid entering the system, which in turn impacts the impeller and causes vibration.” This is not cavitation of a vibrating type“