Lubricant Aeration Testing to Determine Gas Entrainment Level in Oils

Aeration properties of lubricating oils

DEFINITION: Aeration or entrained air is a natural characteristic of an oil to retain free air above the absorption limit

    • Oil aeration is an important property of oil for good mechanical operation, it impairs mechanical performance because of:
        1. Cavitation in components and wear by irregular (potholed) oil film
        2. Oil compressibility (“sponginess”) affects response in hydraulically driven component operation
        3. Oxidation reactions in a larger area of contact with oxygen and pressure cycles affects drain cycle and deposit/varnish formation
    • Previous test methods for aeration testing:
        • ASTM D-8047 Engine oil aeration resistance in CAT C13 heavy-duty diesel engine. COAT replaces D6894 as part of the PC-11
        • Air release ASTM D-3427 and foaming ASTM D-892 are not the eye of the storm of air/oil interaction in performance drivetrain components
        • ISO 12152 Flender foaming test, stops test to measure increased volume in a ruler

New test method to measure Oil Aeration

    • Measures dynamic gas holdup in lubricating oils
    • Principle of operation/test description
      • Aeration by simulation of a air vortex into the oil
    • Aeration measured in steady agitation
        • 700 ml test fluid; Sample heating (25°C – 120°C temperature control), time 30 minutes
        • Turbine mixer develops vortex action to entrain air, Peristaltic pump moves a slipstream to test cell
        • OILPAS Optical imaging device measures bubbles in the test cell
        • The OILPAS algorithm evaluates online the dispersed gas ratio % in oil
        • Deaeration measured in time to release and speed of release
    • Repeatability demonstrated