Open and Closed Case…
What position should the pump discharge valve be in when the pump is started up? My answer is, it depends.
For most low to medium specific speed pumps, like our 2196 ANSI pump, having the valve closed or slightly open is preferred. Just off the closed seat will allow some flow, causing the differential pressure to equalize across the valve making it easier to open the valve.
In case of higher pressure applications, it would be difficult or almost impossible to manually operate the valve if it was fully closed. The closer you get to an axial flow pump, with higher specific speeds, the more important it is to have the valve wide open. This is because the pump requires maximum horsepower at low flow. The horsepower requirements drop as the flow approaches BEP and right side of the pump curve.
One thing is for sure is that the suction valve must be open, no matter what.
– The Summit Pump Team
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