Foam may seem harmless in the oil, but if unaccounted for, it can lead to serious issues in a machine or an engine. Foam finds its way into the oil volume’s headspace after the oil has initially become aerated. Small amounts of air in oil isn’t uncommon, particularly if the oil is expected to become agitated, such as in a gear system. However, as oil becomes more aerated, air bubbles will rise to the surface. Depending on the surface tension, these bubbles will either burst or stay intact in the form of foam.

Additives such as defoamants help to destabilize the foam bubbles and keep overall foam levels low. If air entrainment is not controlled, the defoamants may not be sufficient. The surface tension can be compromised by contaminants such as water, solid particles, grease or other soaps and detergents. The system’s design can also encourage further aeration.

Small amounts of foam may not be cause for concern. However, when foam levels rise and do not return to normal or the foam leads to a drop in the oil level, there may be a bigger issue brewing. Once these concerning foam levels are observed during an inspection, report it and then be sure to follow up. When investigating the root cause, three possibilities should be considered: contamination, defoamant additive levels and mechanical issues.

Visual observation or oil analysis should be performed to determine if there has been an increase in any specific contaminant. Rising water content or particle counts are often the No. 1 reason why foam propagates. Trending this data over time will pinpoint if an increase in the contamination levels correlates to the foaming issue.

The defoamant additive levels may also have depleted or become ineffective. This can be measured through oil analysis by comparing the results from air release and foam stability tests to those from a baseline sample. “Please note that defoamant additives are carefully homogenized in the original oil’s formulation, so additive levels that are too high or low can lead to an increase in foam.”

Finally, keep in mind that air entrainment is worsened when oil is heavily agitated. Suction lines positioned ahead of a hydraulic pump can also pull in air from connector leak points, suction inlet points or any other ingression point.

If you have noticed that your system is starting to having foam, it may be a good time to check when it was changed last. If unknown a simple and quick sample can be pulled and sent to the lab to test to see if there is any issues with the oil. With the price of costly breakdowns of your equipment, you should not ignore foaming oil on these machines. 

We would be happy to come to your shop and assist you with getting the sample and get it shipped off to the lab. We are not looking to sell you some of our products, we are looking to help you protect your investments. If there is issues identified in the test results we will review them with you and offer some solutions. That is what we offer, yes we do sell various lubrication products. But we don’t believe in high pressure sales tactics, we rather educate our customers and allow them to decide based on facts and what they can afford. lubricating oil analysis hydraulic oil gear oil