GAGE VAPOR PRESSURE OF LPG: ASTM D1267
EXPLANATION
Information on the vapor pressure of LPG products under temperature conditions from 37.8 to 70° C is pertinent to selection of properly designed storage vessels, shipping containers, and customer utilization equipment to ensure safe handling of these products. For LPG, vapor pressure is an indirect measure of the most extreme low temperature conditions under which initial vaporization can be expected to occur. It can be considered a semi-quantitative measure of the amount of the most volatile material present in the product.
TEST SUMMARY
The test apparatus consisting of two interconnected chambers and equipped with a suitable pressure gage is purged with a portion of the sample which is then discarded. The apparatus is then filled completely with the portion of the sample to be tested. A 33.3 to 40 volume percent of the sample content of the apparatus is immediately withdrawn to provide adequate free space for product expansion. The apparatus is then immersed in a water bath maintained at the standard test temperature of 100° F or, optionally, at some higher test temperature up to and including a test temperature of 70° C. The observed gage pressure at equilibrium, after correcting for the gage error and correcting to a standard barometric pressure, is reported as the LPG vapor pressure at the selected test temperature.
TEST PRECISION
Repeatability: 12 kPa (1.8 psi)
Reproducibility: 19 kPa (2.8 psi)
This procedure has no bias because the value of vapor pressure is defined only in terms of this test method.
