Foaming Characteristics of Lubricating Fluids

Description

A comprehensive assessment of the oil's tendency to foam and the foam's ability to collapse quickly at 24°C and 93.5°C to prevent oil starvation.

Foam is air, and air, as is known, cannot be compressed and does not lubricate parts. The presence of foam in your hydraulic system or turbine leads to so-called «spongy» control (pressure drops), cavitation destruction of pumps, and accelerated oxidation of the oil itself. Foaming characteristics analysis by the ASTM D892 method at the RENA laboratory will mathematically precisely show how effectively the anti-foam additive (defoamer) in your product works. This test is a guarantee that the lubricant will not splash out through breathers during intense agitation, and the equipment will operate smoothly and without jerking. The standard ASTM D892 test is extremely strict and consists of three consecutive stages (Sequence I, II, III) that simulate different temperature regimes of equipment operation. The process is performed on a specialized AD0892-540 apparatus. In the first stage (Seq I), 190 ml of oil is poured into a graduated cylinder at 24 °C. Dry, clean air is blown into the fluid through a calibrated spherical diffuser at a rate of 94 ml/min for exactly 5 minutes. After stopping the flow, the volume of foam generated is immediately measured (Tendency). Then the cylinder is left at rest for 10 minutes, after which the foam is measured again (Stability). The second stage (Seq II) repeats the procedure but on a new sample strictly heated to 93.5 °C. The third stage (Seq III) is the most difficult for anti-foam additives: the sample after the hot test is cooled back to 24 °C and blown with air again. This allows checking whether the defoamer (e.g., silicone) has not broken down from the previous heating.