Atmospheric pressure
In centrifugal pump technology, the term refers to the absolute atmospheric pressure at the installation site of the pump, averaged over an extended period of time. In most cases, the atmospheric pressure can be taken as equal for the elevations of both the inlet and outlet cross-sections of the pump system. As the altitude increases above mean sea level (MSL), the atmospheric pressure decreases. See Fig. 1 Atmospheric pressure
Altitude above MSL | Atmoshperic pressure | |
m | Pa | mbar = hPa |
0 | 101300 | 1013 |
500 | 95500 | 955 |
1000 | 89900 | 899 |
2000 | 79500 | 795 |
Fig. 1 Atmospheric pressure: Atmospheric pressure depending on altitude, based on 1013 mbar ("physical atmosphere") at 0 m above MSL
The averaged atmospheric pressure should only be substituted for the absolute atmospheric pressure (which varies by location and time) in rough calculations of the head, NPSH (net positive suction head), etc. The unit of atmospheric pressure is the Pascal (Pa); in centrifugal pump technology however, the unit of bar or mbar (= hPa) is generally used.
