What's lubricant oxidation and how does it affect my oil?

Lubricant oxidation is a gradual breakdown of an oil, which leads to ineffective lubrication of equipment and machines. Over time, this can lead to significant problems within industrial applications, as well as major damage to companies’ critical assets.

As a result, preventive maintenance tasks that revolve around oil changes and lubricant testing are extremely important to an overall maintenance program.

What Happens During Oxidation

When oxidation begins to happen, the chains of hydrocarbons begin to break down. Although initially, this is not noticeable, over time, oxidation will begin to affect the lubrication of bearings and other components. When the chain breaks down, the molecules within the oil change the way they are able to deal with the friction between two moving components.

According to Machinery Lubrication, you can imagine this as a floor covered with a single layer of same-sized marbles with a flat board on top of them. The board can move easily, as the marbles function like bearings. When oxidation occurs, it’s like adding a few ping-pong balls under that board. These larger balls change the way the board moves across the marbles to be less effective and more heat-generating.

Common Lubricant Oxidation Tests

Since good lubrication is so important to the proper operation of machinery and equipment, many equipment manufacturers, third-party organizations, and internal maintenance programs will test for signs of oxidation.

For instance, you can use a viscometer to check the viscosity of oil. Oxidation causes the viscosity of oil to increase or get thicker and this can prevent the proper functioning of equipment. Companies may also want to check the amount of moisture, which can result in plugged filters or accelerate the oxidation of acids that will eventually corrode metal. These situations can increase oxidation. You can use infrared spectroscopy to check moisture levels. Some organizations also test for the total acid number and the total base number, which monitors oxidation and oil breakdown.

Often, a maintenance technician may see metallic particles in the oil, notice that the color is darker than normal, or detect a foul odor. These visual signs can also indicate oxidation.

If the company is using additives within its lubricants, there are also more specific tests that can detect breakdown occurring within those additives. For example, a magnetometer measures the mass of ferrous material, and a laser beam can help count and measure the size of particles.

Preventive Maintenance Considerations

By incorporating lubricant testing as one component of equipment maintenance, companies can better monitor overall asset condition and take corrective steps before downtime or damage occurs.

Although many companies may schedule regular oil changes, this task alone does not necessarily optimize equipment performance. Without lubricant testing, you may be changing the oil too frequently, wasting both labor and oil. However, if oil changes take place too infrequently, you may damage your equipment or cause other problems.

By conducting an in-service lubricant analysis, you're able to get to the root cause of potential issues. For instance, if you can identify contaminants as a cause of oxidation, you can reduce or eliminate those contaminants and improve the longevity of your lubricants.

It's also important to note that you may need to use more than one test to draw a complete picture of lubricant oxidation. Collect data points from your technicians who work regularly with equipment. Additionally, gather information from sensors that monitor viscosity through flow rates, as well as conduct appropriate oil condition tests. This data in sum can then help you see when lubricants must be changed and possibly the cause of oxidation. These components add to a holistic maintenance history of how frequently, and under what conditions, your equipment may require lubrication services.