ASTM D1267 Test Method for Gage Vapor Pressure of Liquefied Petroleum (LP) Gases (LP-Gas Method)
4. Summary of Test Method
4.1 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. Thirty-three and one-third to forty volume percent of the sample content of the apparatus is immediately withdrawn to provide adequate free space for product expansion.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 37.8°C (100°F) or, optionally, at some higher test temperature up to and including a test temperature of 70°C (158°F).
4.2 The observed gage pressure at equilibrium, after correcting for gage error and correcting to a standard barometric pressure, is reported as the LPG Vapor Pressure at the selected test temperature.
5. Significance and Use
5.1 Information on the vapor pressures of liquefied petroleum gas products under temperature conditions from 37.8 to 70°C (100 to 158°F) is pertinent to selection of properly designed storage vessels, shipping containers, and customer utilization equipment to ensure safe handling of these products.
5.2 Determination of the vapor pressure of liquefied petroleum gas is important for safety reasons to ensure that the maximum operating design pressures of storage, handling, and fuel systems will not be exceeded under normal operating temperature conditions.
5.3 For liquefied petroleum gases, 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.
