Cleverly formulated compressor oils are manufactured today by lubrication giants like Mobil, Fuchs and Shell. These built-for-purpose oils are designed to cope with extreme operating conditions, providing premium protection for parts subject to wear.
Due to the intense environments and pressures that compressor oils must function in, lubricants must be refreshed regularly to remain effective. Older oil that has degraded due to excess heat or a build-up of contaminants will lead to ineffective operation and damaged equipment.
How compressor oil differs from other lubricants
The oil for lubricating screw compressors is designed not only to protect internal surfaces from suffering wear, but also to perform many other jobs as well. By design, compressor oil differs greatly from oils more commonly used to lubricate machinery. For this reason, regular changes must be affected on schedule and your compressor’s maintenance intervals should never be stretched to make oil go further.
In many other types of machines, a variety of specially designed internal seals will typically protect the lubricants used from making contact with dirt, gasses, water and other unwanted contaminants that may impact its performance. However, in a screw compressor that has been lubricated, the oil comes into direct contact with both compressed air and the compressor inlet air.
When air has been compressed, any water vapour it contains is forced out of the air and forms as freely running water, which the oil will then pick up. Dust trapped in the air will also come out as the compression squeezes the miniscule molecules together. These contaminants are then ferried by the compressor oil to an oil filter, oil sump and cooler. The expended heat generated by the compression activity drives the water vapor off, and the machine’s filtration system will remove any other contaminants present.
Within the compressor itself, the oil works to seal any gaps present between the screw parts, assisting with compression. The heat created by the compression of air is then absorbed by the oil and taken away to the compressor’s dedicated lubricant cooler. During this vital process, both oxygen and heat contained in the air that’s been compressed will break down the lubricant’s properties. Operating under high temperatures, this can cause compressor oil to age prematurely.
Compressor oil that has lost its lubricating properties will also cause excessive wear, additionally forming a varnish that can coat a compressor’s innerworkings. This can reduce the efficiency of its heat exchangers and can heat the lubricants to undesirable temperatures, causing further damage.
Best practices for compressor oil changes
Specialist lubricant types will all have different change intervals recommended, so pay close attention to the manufacturer’s advice. These recommendations will also be impacted by the operating conditions and operating hours of the compressor.
If you’re concerned about the cost of frequent oil changes, have your oil tested. Manufacturers of compressor oil will provide a lubricant analysis service. It is never a wise practice to try to stretch an oil’s use beyond its manufacturer’s recommendation, as this can lead to compressor failure and substantial costs.