Suction head is also called “maximum self-priming height” (also known as “capability of self-priming”). The NPSH of the pump is subtracted from the local atmospheric pressure, and the loss along the path of the suction pipe and the vaporization pressure of the water temperature are determined to determine the vertical distance of the pumping port from the surface to be pumped. Any pump has a suction stroke and the size is different.
Some centrifugal pumps do not have self-priming capability and must be drained for the first time. Although some micro-pumps also have self-priming capability, the standard "suction stroke" is often different from the vertical height of the water that can be pumped under the "all air in the inlet pipe", and may even be less than half. Therefore, the suction stroke is a more important parameter when selecting the pump.
According to the liquid pressure formula p=ρgh, it is estimated that the height of the water column that can be pressurized by atmospheric pressure is h=p/ρg=10m.
Suction head=10m-0.5m-NPSHr
