When determining the installation height of centrifugal pump, the NPSH of the pump should be greater than the necessary NPSH of the pump in any working condition, which is greater than the necessary NPSH of the pump, or The suction vacuum height Hs of the water pump is smaller than the allowable suction vacuum height of the water pump. Hsao The calculation formula of the pump installation height is:
In the formula ▽a, ▽min.——water pump datum elevation and inlet water minimum operating water level elevation, m. It must be pointed out that (NPSH)r, Hsa. It changes with the flow. (NPSH)r, Hsa should be calculated according to the maximum (NPSH)r or Hsa value corresponding to the maximum and minimum net head that may occur during the operation of the pump. The calculated H can be added to the water level of the corresponding pool to get the maximum. The installation height at the minimum net head is then compared and the lowest ▽a is selected as the installation height of the pump. If the pump allows the water absorption height to calculate a positive value, it means that the pump can be installed above the water level of the inlet pool, but the submerged pump will flood the center line of the impeller below the water surface in order to facilitate the start and prevent the nozzle from generating harmful vortices. —1.0m. If H is allowed to be negative, it means that the pump must be installed below the water surface, and the submerged depth is not less than the above-mentioned value, and is not less than 0.5~1.0m.
