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ASTM D3427 - Method for Air Release Properties of Hydrocarbon Based Oils

Significance and Use

5.1 Agitation of lubricating oil with air in equipment, such as bearings, couplings, gears, pumps, and oil return lines, may produce a dispersion of finely divided air bubbles in the oil. If the residence time in the reservoir is too short to allow the air bubbles to rise to the oil surface, a mixture of air and oil will circulate through the lubricating oil system. This may result in an inability to maintain oil pressure (particularly with centrifugal pumps), incomplete oil films in bearings and gears, and poor hydraulic system performance or failure.

5.2 This test method measures the time for the entrained air content to fall to the relatively low value of 0.2 % volume under a standardized set of test conditions and hence permits the comparison of the ability of oils to separate entrained air under conditions where a separation time is available. The significance of this test method has not been fully established. However, entrained air can cause sponginess and lack of sensitivity of the control of turbine and hydraulic systems. This test may not be suitable for ranking oils in applications where residence times are short and gas contents are high.

1. Scope

1.1 This test method covers the ability of turbine, hydraulic, and gear oils to separate entrained air.

NOTE 1: This test method was developed for hydrocarbon based oils. It may be used for some synthetic fluids; however, the precision statement applies only to hydrocarbon based oils.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

Extracted, with permission, from ASTM D3427-19 - Method for Air Release Properties of Hydrocarbon Based Oils, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International,