Briefly Analyz The State of Pump Outlet Valve

Under normal circumstances, starting the centrifugal pump, according to the specification should first fill the pump chamber with media, close the outlet valve, and then open the pump, the purpose is: on the one hand to prevent the starting current is too large damage to the motor; On the other hand, prevent the instantaneous loss of pressure after starting the pump, resulting in pump cavitation.

But many problems cannot be generalized!

For low flow and low head pumps, closing or not closing the outlet valve is not a problem.

For large pumps, the outlet is often slightly opened, in order to prevent the pressure difference between the front and back of the valve after starting, and the outlet valve is not easy to start, so slightly open the outlet valve opening.

Some centrifugal pumps will open the outlet valve slightly due to preheating and other needs.

If it is with suction, it is necessary to fully close the outlet valve, and then open the valve (not the self-priming pump), but also open the pump body exhaust valve.

For some special conditions, the outlet valve can not be opened, for example, liquid propylene, if the outlet valve is opened first, propylene is vaporized, the pump will certainly not be able to pressure, so it must be the first to close the valve, pump and then quickly open the outlet valve.

The above are centrifugal pumps, for other types of pumps, the situation is as follows:

1. Large flow starting characteristic of axial flow pump – full open valve starting

The maximum shaft power of the axial flow pump is 140% to 200% of the rated shaft power under zero flow condition, and the minimum power is at the maximum flow rate, so in order to have the minimum starting current, the starting characteristic of the shaft power should be a large flow start (that is, full open valve start).

2. Starting characteristics of mixed flow pump – full open valve starting

The shaft power of the mixed flow pump in the zero flow condition is between the above two kinds of pumps, which is 100% to 130% of the rated power, so the starting characteristics of the mixed flow pump should also be between the above two kinds of pumps, and it is best to start the valve fully open.

3. Starting characteristics of vortex pump – full open valve starting

The maximum shaft power of the vortex pump is 130% to 190% of the rated shaft power under zero flow condition, so similar to the axial flow pump, the starting characteristic of the vortex pump should be a large flow start (that is, full open valve start).

 

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