1. Scope

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Rationale

5.1 Water in liquefied petroleum gas (LPG) can cause operational issues in equipment and downstream processes, and create safety hazards during the storage, distribution, and use. Water can also lead to corrosion problems. 5.1.1 The moisture content of LPG can be critical to the use, transportation, or processing of LPG products, especially at cold ambient temperatures and during pressure throttling, when icing or hydrate formation, or both, are most likely to occur. In order to prevent ice or hydrate formation, or both, the water content has to be low enough to prevent the formation of free water in storage tanks and/or regulators over the entire range of operating conditions (temperatures, pressures, and compositions) encountered during normal service. For example, propane and propane-propene mixtures require moisture levels below the equilibrium saturation level of water at operating temperature and pressure for these hydrocarbons to meet specifications such as Specification D1835. [ASTM D8094] 5.1.2 The dryness of propane has typically been monitored with ASTM D2713 which is a “functional” valve freeze test but does not provide a direct measure of water content. 5.2 Methanol can be added as a de-icer to prevent freezing problems associated with excessive water. Methanol can attack some elastomers, degrading their performance, and elevating residue levels. Methanol can also affect the D2713 freeze vale results. [ASTM D1835] 5.2.1 The simultaneous monitoring of water and methanol can assist water mitigation efforts. 5.3 Regulations often require that LPG used for fuel purposes be odorized with a stenching agent such as ethyl mercaptan. 5.4 This analytical method directly measures water, methanol and ethyl mercaptan content in LPG and pressurized hydrocarbons and their mixtures and is suitable for LPG quality assessments.