The pump outlet valve is open to a low degree
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May I ask, for a centrifugal pump whose process medium is demineralized water, if the outlet valve opening is very small during the water circulation process, will that have an impact on the pump? Is this approach reasonable?
Hello! A very small opening of the outlet valve indicates a low flow rate; you can refer to the curve graph provided by the supplier. Cavitation will occur if the operating flow rate is below the minimum stable flow rate or falls within the area not allowed for operation on the curve ； Furthermore, the outlet pressure of the centrifugal pump (i.e., the head) decreases as the flow rate increases; in other words, it increases as the flow rate decreases. It is possible to refer to the head curve to determine whether the pump’s outlet pressure exceeds the allowable operating pressure of the downstream equipment!
Also, if the pump operates in this manner for a long time, it’s a waste; it might be better to choose a smaller centrifugal pump；
That’s unreasonable. Every pump has its optimal operating conditions; such a low flow rate not only leads to waste but also, if it falls below the pump’s minimum flow requirement, it is detrimental to the pump’s proper operation
Of course it has an impact; improper operation leads to low flow rates, high pressure, and internal friction within the liquid
Operating at the minimum flow rate for an extended period can damage the pump shaft. It has happened to my company. The minimum flow point can operate, but not for a long time, as the radial force of the centrifugal pump causes damage. You can find out by looking into the principle of the radial force in centrifugal pumps.
Operating at particularly low flow rates causes the pump to vibrate significantly. Then many problems arise; bearings and mechanical seals will significantly reduce the service life. Pumps are designed with preferred operating ranges and allowable operating ranges based on flow rate; it is best for pumps to operate within their preferred operating ranges, and they should not operate for extended periods at flow rates below those of the allowable operating range.