As one of the most commonly used types of water pumps, centrifugal pumps require professionals in the industry—whether in sales, technical roles, or after-sales service—to have a solid understanding of their installation. Installing a centrifugal pump involves detailed calculations; today, the pump experts at Shanghai Shenyin Pump will provide a brief overview of centrifugal pump installation and the associated calculations.
To prevent cavitation, the installation height of a centrifugal pump must be determined through careful verification calculations. A schematic diagram of the pump's inlet-side configuration is shown below:
The pump's permissible geometric installation height depends on various factors, as expressed by the following formula:
Where:
[Hg] — Permissible geometric installation height of the pump (m); (the calculated result is used for design purposes; the actual installation height must be lower than the permissible height)
pe — Pressure at the suction water surface (Pa); (atmospheric pressure at the suction surface; atmospheric pressure decreases as altitude increases)
pv — Saturated vapor pressure (Pa); (depends on water temperature; higher water temperatures result in higher saturated vapor pressure)
ρ — Fluid density (kg/m³);
g — Acceleration due to gravity (9.81 m/s²);
[NPSH] — Permissible Net Positive Suction Head (cavitation allowance) of the pump (m); (depends on pump performance; specified by the manufacturer)
hw — Head loss in the suction pipeline (m); (depends on the design of the suction pipeline; determined by the design engineer)
As indicated by the formula above, the permissible geometric installation height decreases as altitude increases, water temperature rises, the required NPSH increases, or head loss in the inlet pipeline increases. The table below shows atmospheric conditions and corresponding pressure heads at various altitudes:
Atmospheric conditions and corresponding pressure heads at various altitudes
The table below shows water's saturated vapor pressure and corresponding pressure heads at various temperatures:
Water's saturated vapor pressure and corresponding pressure heads at various temperatures
Example: According to the pump specifications, a certain centrifugal pump has a required net positive suction head ([NPSH]) of 3.29 m. It is to operate at an altitude of 500 m, where the maximum summer water temperature is 40°C. If the head loss in the suction pipe is 1 m, the geometric installation height ([Hg]) for the pump at this location is calculated as follows:
Assuming the pressure at the suction water surface equals the local atmospheric pressure, the atmospheric pressure head at an altitude of 500 m is found from the table to be 9.7 m, and the saturated vapor pressure head of water at 40°C is 0.752 m. The calculation is:
[Hg] = 9.7 - 0.752 - 3.29 - 1 = 4.658 m. We hope the information above regarding centrifugal pump installation has been helpful to you.