Pump Static Head
Static head refers to the difference in elevation thus, the total static head of a system is the difference in elevation between the liquid levels at the discharge and suction points of the pump.
The static discharge head is the difference in elevation between the discharge liquid level and the pump centreline.
The static suction head on the other hand is the difference in elevation between the suction liquid level and the pump centreline.
If the static suction head has a negative value because the suction liquid level is below the pump centreline, it is often referred of as static suction lift.
If either the suction or discharge liquid level is under a pressure other than atmospheric, this pressure can be considered as part of the static head or separately as an addition to the static head.
There are occasionally situations that arise in which the determination of a pump duty pressure rise is not as straight-forward or at the very least, sometimes appears counter-intuitive. Lets look at the following example case.
The system flow rate is 1000 USGPM and the system static head is 10 ft. There is also a 50 ft elevation change in the system downstream of the pump. The results of this system as modeled in FluidFlow are seen below.
As we can see, the pump duty pressure rise is 25.31 ft fluid (approx). The pump only needs to generate 25.31 ft head due to the syphon effects experienced in the system. This syphon effect helps reduce the required pump head when the system if filled with fluid as a result of hydrostatic pressure recovery as the liquid in the pipe drops in elevation and the pressure increases. It's this issue which often produces result you may not expect.
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