Views: 3000 Author: Site Editor Publish Time: 2023-12-25 Origin: Site
Centrifugal pump is one of the most commonly used pumps in water transportation. The floor elevation in the pump room depends on the installation height of the pump. Accurately calculating the maximum allowable installation height of the pump is of great significance to ensure safe water supply and save construction costs for the pump station.
In order to avoid the occurrence of cavitation, the installation height of the centrifugal pump needs to be carefully checked and calculated. The schematic diagram of the water pump inlet side device is as follows:
The allowable geometric installation height of the pump is related to various conditions, and the formula is as follows:
In the formula:
[Hg] - allowable geometric installation height of the pump, m; (The calculation results are for use in design, and the actual installation height should be lower than the allowable installation height)
PE - Water absorption surface pressure, Pa; (For the atmospheric pressure on the water surface, the higher the altitude, the lower the pressure) pv - saturated vapor pressure, Pa; (Related to water temperature, the higher the water temperature, the higher the saturated steam pressure) ρ— Density of fluid, kg/m3; G - Gravitational acceleration, 9.81m/s2; [NPSHr] - allowable cavitation margin of the water pump, m; (Related to the performance of the water pump, provided by the water pump manufacturer) hw - Head loss in the suction pipeline, m. (Related to the design of the suction pipeline, to be determined by the designer)
As can be seen from the above equation:
The higher the altitude, the higher the water temperature, the greater the allowable cavitation margin, the greater the head loss of the inlet pipeline, and the smaller the allowable geometric installation height.
The atmosphere and corresponding head heights at different altitudes are shown in the table below
| Altitude (m) | Atmospheric pressure (KPa) | Headheight (m) |
-600 | 110.85 | 11.3 |
0 | 101.32 | 10.3 |
200 | 99.08 | 10.1 |
500 | 95.16 | 9.7 |
1000 | 90.25 | 9.2 |
1500 | 84.36 | 8.6 |
2000 | 79.46 | 8.1 |
3000 | 70.63 | 7.2 |
4000 | 61.8 | 6.3 |
5000 | 53.95 | 5.5 |
The corresponding head height for the saturated vapor pressure of water at different temperatures is shown in the table below:
Water temperature(℃) | Saturated vapor pressure(KPa) | Head height(m) |
| 10 | 1.23 | 0.125 |
| 20 | 2.34 | 0.238 |
| 30 | 4.24 | 0.433 |
| 40 | 7.37 | 0.752 |
| 50 | 12.33 | 1.272 |
| 60 | 19.92 | 2.066 |
| 70 | 31.16 | 3.249 |
| 80 | 47.36 | 4.97 |
| 90 | 70.10 | 7.406 |
| 100 | 101.32 | 10.786 |
Example: A certain brand of IS100-315-55/2 water pump has a NPSHr of 3.29m and is intended to operate at an altitude of 500m. The highest summer water temperature in this area is 40 ℃. If the head loss of the suction pipe is 1m, the geometric installation height of the pump in the local operation [Hg] is calculated as follows:
Assume that the pressure on the water intake surface is the local atmospheric pressure, and the atmospheric pressure head at an altitude of 500m is 9.7m according to the table; When the water temperature is 40 ℃, the saturated vapor pressure head of water is 0.752m;
Calculated: [Hg]=9.7-0.752-3.29-1=4.658m