ASTM D892 Standard Test Method for Foaming Properties of Lubricating Oils

The standard "ASTM D892 Standard Test Method for Foaming Properties of Lubricating Oils," published by the American Society for Testing and Materials (ASTM), describes a test method for determining the foaming properties of lubricating oils at 24°C and 93,5°C. These tests experimentally evaluate foaming tendency and foam stability.

Mercury is designated by many regulatory agencies as a hazardous substance that can cause central nervous system, kidney, and liver damage. Mercury or its vapors can be harmful to health and corrosive to materials.

The tendency of oils to foam can be a serious problem in systems such as high-speed gears, high-volume pumping, and splash lubrication. Inadequate lubrication, cavitation, and lubricant overflow can lead to mechanical failure. This test method is used to evaluate oils for these operating conditions.

For the purposes of this standard, the following terms and definitions apply:

Diffuser: A device used to disperse a gas into a fluid. In this test method, the diffuser can be made of metallic or non-metallic materials.
Entrained air (or gas): In liquids, a two-phase mixture of air (or gas) dispersed in a liquid in which the liquid is the major volumetric component. Entrained air (or gas) can form micro-sized bubbles that are not uniformly distributed in liquids and can rupture or foam by coalescing to form larger bubbles at or below the surface.
Foam: A collection of bubbles formed in or on the surface of a liquid in which air or gas is the main volumetric component.
Lubricant: Any material placed between two surfaces that reduces friction or wear between them. In this test method, the lubricant is oil, which may or may not contain additives such as foam inhibitors.
Maximum pore diameter: In gas diffusion, the diameter of the circular cross-section of a capillary tube. It is equivalent to the largest pore of the diffuser in question.
Dynamic bubble: In the maximum pore diameter test, this is the initial bubble that passes through the diffuser, followed by a continuous train of bubbles. When a diffuser is immersed in a liquid, air can become trapped in the pores. This air can eventually escape when the diffuser is pressurized. In the maximum pore diameter test, the escape of such a bubble should be ignored.
Foam stability: In a foam test, the amount of foam remaining at a specified time after the air supply is cut off. In this test method, foam stability is determined by measurements taken 10 minutes plus/minus 10 seconds after the air supply is cut off. If the foam settles to 0 mL before the 10-minute settling time has elapsed after the air supply is cut off, the test may be terminated and the foam stability result recorded as 0 mL.
Foaming tendency: In the foam test, it is the amount of foam determined from the measurements taken immediately after the air flow is cut off.

During the test, two portions of the sample are held in the diffuser at two predetermined temperatures (24°C plus/minus 5°C and 93,5°C plus/minus 0,5°C). A controlled and constant airflow of 94°C plus/minus 5 mL/min is applied to the sample for 5 minutes and allowed to settle for 10 minutes. At the end of each period, the foam height and volume are measured. The foaming tendency and stability are reported.

High surface tension contaminants in lubricants and air contained in in-service oils create bubbles and foam. Foam creates incomplete oil films, leads to low oil pressures, and accelerates oil degradation, including additive depletion. The resulting effects include inadequate lubrication, metal parts failure, cavitation in pumps, and overall mechanical failure. A necessary step to minimize these effects is to precisely and objectively determine the foaming characteristics of lubricant formulations. This can be used as a diagnostic tool for wear control and optimal PM programs for engines and machinery, saving operating costs and downtime.

ASTM D892 is a critical procedure used to evaluate the foaming tendency and stability of lubricating oils under specific conditions. Foaming in lubricating oils can cause serious operational problems in systems such as high-speed gears, high-volume pumping, and splash lubrication, and can lead to mechanical failure by causing insufficient lubrication, cavitation, and flooding. Lubricating oils are essential for reducing friction and wear in mechanical systems. However, the tendency of oils to foam can negatively impact their performance, leading to:

Inadequate lubrication: Foam reduces the oil's ability to form a consistent lubricating film, increasing wear.
Cavitation: Air bubbles in the oil can collapse under pressure, damaging components.
Overflow loss: Excessive foam can lead to lubricant loss, reducing system efficiency.

The ASTM D892 test method is widely used to evaluate oils in applications where foam control is critical and to ensure reliability and performance in industrial and automotive systems.

ASTM D892 standard includes a method for determining the foaming tendency and foam stability of lubricating oils. The test measures:

Foaming tendency: The volume of foam formed when air bubbles are passed through the oil sample.
Foam stability: The time it takes for the foam to collapse after air injection stops.

The ASTM D892 test method includes these basic steps:

Sample preparation: A sample of lubricating oil is placed in a graduated cylinder.
Air injection: Air is bubbled through the oil at a controlled rate, usually at 24 degrees for Row I and 93,5 degrees for Row II, using a diffuser made of metallic or non-metallic materials.
Foaming tendency measurement: The foam volume formed immediately after air injection is recorded.
Foam stability measurement: After the air flow is stopped, the time it takes for the foam to collapse or the foam volume remaining after a certain period of time is measured.
Rows III and IV (optional): Additional tests may be performed to evaluate foam properties after cooling or at higher temperatures (e.g., 150 degrees according to ASTM D6082).

The test apparatus typically includes a test bath, graduated cylinders, and a gas diffuser, as specified in the standard. Results are reported as foam volume for trend and stability, providing a quantitative measure of the oil's performance.

The ASTM D892 test method is critical to industries involved in the production and use of lubricating oils. These include:

Automotive: Evaluation of engine oils and transmission fluids.
Industrial: Evaluation of oils for high-speed gears, hydraulic systems and turbines.
Aviation and marine: Ensuring lubricants meet performance standards in harsh conditions.

Ultimately, the ASTM D892 standard test method provides a robust framework for evaluating the foaming properties of lubricating oils, helping to ensure their suitability for demanding applications. By measuring foaming tendency and stability at specific temperatures, the test helps prevent mechanical failures caused by foam-related problems. Despite some limitations in reproducibility, this standard remains a staple in lubricant testing due to its alignment with international standardization principles and its applicability across a variety of industries.

Our organization, which has been serving for many years and meticulously following global developments in science and technology, employs a skilled team and extensive infrastructure to conduct testing, measurement, and analysis in a wide range of areas for businesses across all sectors. In this context, we also provide testing services in accordance with ASTM D892, Standard Test Method for Foaming Properties of Lubricating Oils.