The moisture content of some LPG products can be critical to their use in cold climates. Special- Duty Propane and Commercial Propane require moisture levels below their saturation level at operating temperatures and pressures to meet specifications. In order to prevent ice and/or hydrate formation, the degree of water saturation must be low enough to prevent the formation of free water in storage tanks and/or regulators during normal service and even at very low ambient temperatures to which they may be exposed. The formation of ice and/or hydrates can lead to the blockage of vapor or liquid fuel lines, and disrupt the operation of pumps, meters, filters, valves, regulators and safety shut-off valves. Occasional process failures or contamination during transport can cause water contamination of LPG. The dryness of propane can be evaluated using D2713, Standard Test Method for Dryness of Propane (Valve Freeze Method). However, this test method is a performance test on a spot sample, that may be fooled by the presence of methanol added as an anti-icing additive. Method D2713 does not provide a quantitative measurement of water content. Method D2713 has environmental concerns due to the amount of propane that is released during the test. This method proposes use of an electronic hygrometer that measures the dew point of a flowing stream of LPG, and calculates the amount of water in a liquid sample based on the composition of the LPG, and its temperature.
The title and scope are in draft form and are under development within this ASTM Committee.