Static Suction Head

Static Suction Head The static suction head / is the vertical distance measured from the free surface of the hquid source to the pump centerhne plus the absolute pressure at the liquid surface. 

NPSH (net positive suction head) = (pressure head of source) + (static suction head) — (friction head of the suction line) — (vapor pressure of the flowing liquid). 

The total head on the pumps in Fig. 6.13d, c, and /is computed in the same way as described above, except that the total static head is less because the pump has a static suction head—that is, the elevation of the liquid on the suction side reduces the total distance through which the pump must discharge liquid thus the total static head is less. The static suction head is subtracted from the static discharge head to determine the total static head on the pump. 

Compute the net positive suction head on the pump. The net positive suction head hn on a pump when the liquid supply is above the pump inlet equals pressure on liquid surface + static suction head-friction-head loss in suction piping and pump inlet-vapor pressure of the liquid, all expressed in feet absolute of liquid handled. When the liquid supply is below the pump centerline—i.e., there is a static suction lift—the vertical distance of the lift is subtracted from the pressure on the liquid surface instead of added as in the preceding relation. 

The static suction head is a physical dimension that is measured in feet of liquid at the operating temperature. In this installation, hsh = 10 ft absolute. 

The terms suction and discharge in the context of heads refer to portions of the system before and after the pumping station, respectively. Static suction lift h( is the vertical distance from the elevation of the inflow liquid level below the pump inlet to the elevation of the pump centerline or eye of the impeller. A lift is a negative head. Static suction head h, is the vertical distance from the elevation of the inflow liquid level above the pump inlet to the elevation of the pump centerline. Static discharge head h is the vertical distance from the centerline elevation of the pump... 

Static suction head—The vertical distance from the elevation of the inflow liquid level above the pump centerline to the centerline of the pump. 

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