VAPOR PRESSURE:
For finding vapor pressure of some important process fluids please refer to below Chevron appendix. {Chevron}
- 6.2 If pump handles a liquid near its boiling point, the pressure in the mechanical seal chamber shall be sufficiently above the inlet pressure, or the temperature in the immediate vicinity of the seal shall be sufficiently below vaporization temperature to prevent vaporization at the seal faces. {Phase 13 spec.}
- 8.16 (New) Dual un-pressurized seals shall be provided on pumps handling hydrocarbons with a vapor pressure greater than 1.03 bar at the higher of either 38 °C or the pumping temperature. The secondary seal in all dual un-pressurized seal installations shall be equipped with a pumping ring. In all cases the secondary seal must be of a balanced design. {Kermanshah spec.}
- 8.14 ( Addition ) Unless otherwise specified in the individual data sheet, dual ( Pressurized or Unpressurized) seals shall be provided if any of the following condition are specified : {Shahzand spec.}
- Dangerous services.
- C4 or more light hydrocarbon pump fluid
- Vapor press. of pump fluid greater than 5 bar (abs) on each operation temperature in seal chamber.
- For services that the H2S composition of the fluid leakage rate shall probably exceed 1g/s when the seals fail.
Vapor press. is the specific pressure that the bobbles of a fluid appear in that pressure and a given temperature. Whatever the vapor press. of the fluid is greater, the fluid intend to vaporize more likely. Vapor press. of each fluids is only a function of temperature.
The most application of vapor press. is in the calculation of NPSHA and for selecting a suitable mechanical seal.