ASTM D4056-01(2006)

1.1 This test method covers a procedure for estimating the equilibrium solubility of water and its vapor in hydrocarbon and aliphatic ester lubricants, at temperatures between 277 and 373 K. The test method is limited to liquids of low to moderate polarity and hydrogen bonding, with predicted solubilities not over 1000 ppm by weight in hydrocarbons, or 30000 ppm by weight in oxygenated compounds, at 298 K.

1.2 Specifically excluded are olefins, nitriles, nitro compounds, and alcohols.

1.3 This test method is recommended only for liquids not containing widely different chemical species. This excludes blends of esters with hydrocarbons, and lubricants containing detergents, dispersants, rust preventives, or load carrying additives.

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Knowledge of the water content is important in lubrication, as large amounts of water can cause corrosion fatigue in steel bearings, and the complete absence of water can cause metal scuffing.

High water content has an accelerating effect on oxidation of lubricants, and can also contribute to foaming, especially at high altitude or temperature, or both.