Calculation formula of Hg geometric installation height of energy-saving self-balancing multistage centrifugal pump
Energy-saving self-balancing multi-stage centrifugal pump The floor elevation in the pump room depends on the installation height of the pump. Correctly calculate the maximum allowable installation height of the energy-saving self-balancing multi-stage centrifugal pump, so that the pump station can provide safe water supply and save soil construction costs. , Has a very important meaning.
In order to avoid the occurrence of cavitation, the installation height of the centrifugal pump needs to be checked and calculated very carefully. The schematic diagram of the inlet side device of the energy-saving self-balancing multi-stage centrifugal pump is as follows:
Energy-saving self-balancing multi-stage centrifugal pump inlet side device form diagram
The allowable geometric installation height of the energy-saving self-balancing multi-stage centrifugal pump is related to various conditions. The calculation formula for the Hg geometric installation height of the energy-saving self-balancing multi-stage centrifugal pump is as follows:
Energy-saving self-balancing multi-stage centrifugal pump Hg geometric installation height calculation formula
where:
[Hg]—The allowable geometric installation height of the pump,
M; (Calculation results are for use in design, the actual installation height must be lower than the allowable installation height)
Pe—water surface pressure,
Pa; (the atmospheric pressure of the water surface, the higher the altitude, the lower the atmospheric pressure)
Pv—saturated vapor pressure,
Pa; (related to water temperature, the higher the water temperature, the higher the saturated steam pressure)
Ρ—the density of the fluid, kg/m3;
G—gravitational acceleration, 9.81m/s2;
[NPSHr]—The allowable NPSH of the water pump,
M; (related to pump performance, provided by the pump manufacturer) hw—head loss in the suction pipeline, m. (Related to the design of the suction pipe, determined by the designer)
From the above formula:
The higher the altitude, the higher the water temperature, the greater the allowable cavitation margin, the greater the head loss of the inlet pipe, and the smaller the allowable geometric installation height.
The atmosphere and corresponding head height at different altitudes are shown in the following table:
The saturated vapor pressure of water at different temperatures corresponds to the height of the head as shown in the table below:
Example: A certain brand of MDP450-95X8 energy-saving self-balancing multi-stage centrifugal pump has a NPSH [NPSHr]=3.29m. If you want to work at an altitude of 500m, the highest water temperature in summer in this area is 40℃. If the water head of the suction pipe If the loss is 1m, the local operating geometric installation height [Hg] of the pump is calculated as follows:
suppose: the water surface pressure is the local atmospheric pressure, and the atmospheric pressure head is 9.7m at an altitude of 500m from the table; when the water temperature is 40℃, the saturated steam pressure head of the water is 0.752m;
calculated: [Hg]=9.7-0.752-3.29-1=4.658m
