VAPOR LIQUID RATIO TEMPERATURE OF FUELS: ASTM D5188
EXPLANATION
The tendency of a fuel to vaporize in automotive engine fuel systems is indicated by the vapor-liquid ratio of the fuel. Automotive fuel specifications generally include this ratio temperature. This test method is applicable to samples for which the determined temperature is between 36 and 80° C, and the vapor-liquid ratio is between 8:1 and 75:1. When the ratio is 20:1, the result is intended to be comparable to the results obtained by Test Method ASTM D2533. This test may also be applicable at pressures other than 1 atmosphere, but the stated precision may not apply.
TEST SUMMARY
This test method determines the temperature at which the vapor formed from a selected volume of volatile petroleum product saturated with air at 0 to 1 ° C produces a pressure of 1 atmosphere in an evacuated chamber of fixed volume. A known volume of chilled, air-saturated sample is introduced into an evacuated, thermostatically controlled test chamber of known volume. The sample volume is calculated to give the desired liquid-vapor ratio for the chamber volume in use. After injection, the chamber temperature is adjusted until a stable chamber pressure of 101.3 kPa is achieved.
TEST PRECISION
Repeatability: 0.6° C (1.1° F)
Reproducibility: 0.9° C (1.6° F)
Bias has not been determined.
