Vapor Pressure

The vapor pressure of a fluid is the pressure (at a given temperature) at which a fluid will change to a vapor and is expressed as absolute pressure (bar a). Each fluid has its own vapor pressure /temperature relationship. In pump sizing, vapor pressure can be a key factor in checking the Net Positive Suction Head (NPSH) available from the system.

In general terms vapor pressure:
-Is dependent upon the type of fluid.
-Increases at higher temperature.

-Is of great importance to pump inlet conditions.