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The risks of compressor oil ageing and how to avoid them

The risks of compressor oil ageing and how to avoid them

Fast 5: compressor oil circuit maintenance

When it comes to operating a fluid-injected (or oil-injected) rotary screw compressor, selecting the right cooling fluid and ensuring its on-going integrity are both essential to the continuing reliability, efficiency and overall lifetime of the compressor and its wearing parts. In this blog post we share more information around our maintenance tip of the month – #1 regularly check and maintain your oil levels and oil quality.

1. What function does a compressor oil serve?
A compressor cooling fluid is a mixture of oils and additives that perform various necessary functions inside a fluid-injected rotary screw compressor. This includes;
–  Lubrication of the screw compressor block bearings
–  Screw compressor block rotor gap sealing
–  Internal cooling of the compressor package
–  Cleansing of the air

KAESER, compressor, lubricant, oil, fluid
Compressor oil functions

2. Are there different types of compressor oil?
At a basic level the oils used are either mineral or synthetic blends. The additives mixed with them are designed to assist and improve the compressor oils function. The additives assist with:
–  Anti-oxidation
–  Anti-wear
–  Anti-foaming
–  Dispersion of moisture
–  Detergents for circuit cleaning

3. What happens to the compressor oil during prolonged use?
During prolonged use these additives are effectively ‘used up’. This changes the characteristics of the oil. Essentially this results in the oil not performing its core tasks as it should. This is called oil ageing.


The below image visually demonstrates the oil ageing process with the Kaeser Sigma Fluid MOL. The change of oil colour indicates minor changes in the additives. Fresh oil is very light-coloured but will change its colour very quickly. After approximately 100 operating hours, the oil will have a reddish hue. It then begins to turn mauve before finally towards the end of its service life turning a brown colour.

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Kaeser Sigma Fluids – colour change MOL during operation time

Oil ageing can create a number of issues within the compressor from; overheating and lubrication problems to premature mechanical wear and tear. Ultimately this will lead the compressor to breakdown creating – what could have been avoidable – downtime to your business. In addition, premature wear and tear of course impacts the overall lifetime of the compressor.
When the oil characteristics change significantly, all of the above outcomes are very likely.

4. What can I do to avoid this scenario from happening?
There are a couple of key ways you can prevent the above scenario from happening to you. The first is to opt for the lubricant recommended by the Original Equipment Manufacturer (OEM). As an example as to why this is so important, when a Kaeser end-user opts for genuine Kaeser lubricants, they can be assured that they have been rigorously tested with Kaeser compressed air equipment to ensure their durability, performance, efficiency and safety.

Secondly, follow the OEMs recommended oil change service schedule. In addition, make sure you keep an eye on the oil level. You will be able to get advice on all of these suggestions by referring to the operating instructions manual that came with your compressor.

Finally, selecting a service provider that delivers an oil-sample analysis* as part of their standard service scope will also help to avoid such potential issues from occurring. By periodically taking oil samples and sending them away for analysis, it is possible to see if any issues are occurring that need to be addressed.

5. Which oil is right for me?
Again, refer to the OEMs operating instructions which will provide guidance on the recommended lubricant type for your compressor. Generally speaking, mineral based cooling fluids are good in lower duty cycle installations with smaller compressors, whereas synthetic based cooling fluids work well in larger compressor units that have high duty cycles.

The compressor cooling fluid represents a significant machine element for oil-fluid rotary screw compressors. Opting for a high quality cooling fluid and following the OEMs recommended service intervals will go a long way to ensuring the economic operation, availability and long service life of your investment.

For further advice or simply to schedule in your next service click here to contact KAESER AIR SERVICE today.

*KAESER AIR SERVICE provide an oil-sample analysis as part of its standard service scope.


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