Petroleum oils. Determination of air-release properties. Impinger method

2Scope / Description

1.1 This standard is a method for determining the ability of steam turbine oils and other petroleum-based oils to release entrained air. Notes: 1. This method uses an impact absorber to determine the ability of an oil sample to release air. Air bubbles dispersed in the oil can affect its compressibility and may cause equipment failure. This method is not suitable for evaluating the quality of oils used under conditions of short residence time and high gas content in equipment. 2. Mixing of lubricating oil and air in equipment (such as bearings, couplings, gears, pumps, and return lines) can result in dispersed air bubbles in the oil. If the residence time in the tank is insufficient for the bubbles to escape to the oil surface, the air-oil mixture will circulate in the lubrication system. This can lead to insufficient oil pressure (especially in centrifugal pumps), oil film rupture in bearings and gears, and malfunction or failure of the hydraulic system. 3. Under specified test conditions, this method can determine the time required for the entrained air content to decrease to a relatively low value (0.2% volume fraction), thus allowing comparison of the ability of oils to release entrained air under conditions with separation time. Although the validity of the test results has not been fully established, insufficient sensitivity of some turbine control systems may be related to the characteristics of air release from the oil. System structure and system pressure may also differ. 4. In this standard, "% volume fraction" is used to express the volume fraction of a substance.