ASTM D4953 Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends
ASTM D4953 Standard Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
3. Summary of Test Method
3.1 The liquid chamber of the vapor pressure apparatus is filled with the chilled sample and connected to the vapor chamber at 37.8°C (100°F). The apparatus is immersed in a bath at 37.8°C (100°F) until a constant pressure is observed. The pressure reading, suitably corrected, is reported as the vapor pressure.
3.2 Procedure A utilizes the same apparatus and essentially the same procedure as Test Method D323 with the exception that the interior surfaces of the liquid and vapor chambers are maintained completely free of water. Procedure B utilizes a semi-automatic apparatus with the liquid and vapor chambers identical in volume to those in Procedure A. The apparatus is suspended in a horizontal bath and rotated while attaining equilibrium. Either a Bourdon gage or pressure transducer can be used with this procedure. The interior surfaces of the liquid and vapor chambers are maintained free of water.
4. Significance and Use
4.1 Vapor pressure is an important physical property of liquid spark-ignition engine fuels. It provides an indication of how a fuel will perform under different operating conditions. For example, vapor pressure is a factor in determining whether a fuel will cause vapor lock at high ambient temperature or at high altitude, or will provide easy starting at low ambient temperature.
4.2 Petroleum product specifications generally include vapor pressure limits to ensure products of suitable volatility performance.
NOTE 3 - Vapor pressure of fuels is regulated by various government agencies.
