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Air Compressor Oil Change: Lifespan, Roles and How to do It

Compressor oil is an extremely important part of the daily maintenance of air compressors. This article will take you through the importance of compressor oil’s life span and focuses on the factors why you should change the oil regularly.

When it comes to compressors, maintenance is vital. This is a factor many people consider during their compressor purchasing process as they calculate the life cycle cost of compressor. However, when considering oil replacement frequency for oil-injected air compressors, many people incorrectly underestimate the importance of regularly changing the oil as its lifetime directly affects the total operating cost and efficiency of the user's equipment.

What is the role of compressor oil?

Oil plays a critical role in oil-cooled rotary screw air compressors. Let’s quickly have a look at what compressor oils do.

1. The most important task of oil is to cool the compressor

oil-cool-the-element
A crucial role of compressor oil is to absorb the generated heat in the compressor, which makes sure that the compressor keeps running at optimal temperature conditions. If the temperature of the compressor is too high, the element or all rotating parts would be excessively stressed and the service life would be shortened.

2. Compressor oil against wear

oil-for-lubricating
Compressor oil also serves to reduce wear on all rotating parts. The oil forms a protective layer over all rotating parts, to make sure that there is no metal to metal contact which could lead to operational issues and early breakdown.

3. Sealing of oil-injected compression chambers

Oil-to-seal
Oil-injected compressors use the oil to seal the compression chamber. The sealing function of oil ensure that there is no back pressure which would lead to a back flow of air and in the end results in a lower free air delivery.

4. Clean the compressor with oil

Oil-to-clean
Cleaning happens in two different ways: the oil will solve a certain concentration of contamination particles and the bigger dust or metal particles will be carried along with the oil to the oil filter to be filtered out of the fluid.

The ultimate function of compressor oil is to keep compressors moving and maintaining optimum performance of compressors.

What is the impact of operating conditions on the oil lifetime?

Ambient temperature, air humidity level and air intake quality (dust level) are the 3 main factors which impact the overall oil lifetime. Based on years of experience and in-depth analysis of connected machines, Atlas Copco developed a world heat map where regions are categorized as being mild, demanding or extreme.

Middle East, which is characterized by hot summers with high humidity (as high as 90% in some areas) and frequent sandstorms during periods of seasonal change, is categorized as being an extreme region.

What does this mean for the oil? The sweltering and humid heat can decrease oil life expectancy and change the characteristics of the oil. Overtime this can result in the oil not performing its core tasks as it should.

compressor-working-condition-comparison

Find here the temperature histograms of a list of connected machines. Left side is the profile for machines running in Belgium (a mild country), right side is the profile for compressors installed in Middle East (an extreme country).

How long is the compressor oil lifespan?

The lifetime of an oil, and consequentially, the specified oil drain interval depends of the operating conditions in which the oil is used. Oil ageing is happening due to the process of oxidation of the oil. The rate of oxidation is closely linked with the operating conditions (read temperatures, air quality and humidity level).

Due to the process of oxidation, particle formation happens. It starts with small solvable particles but overtime these particles will stick to each other and form larger particles. Within a certain size, these particles will still be filtered out by the oil filters & separators.

At a certain moment the specified oil drain interval is reached, and it is time to change the oil

By doing so, it is avoided:

  • even larger harmful particles are being formed.
  • the oil becomes too acid attacking weaker materials in the oil circuit like seals and gaskets.
  • the oil becomes too thick as a result of viscosity increase blocking smaller channels in your oil circuit

As a result of changing the oil at its specified oil drain interval, you are sure the next oil drain interval is also guaranteed!  By doing so, the machine remains in optimal condition, reliability is secured, and performance remains as it should be.

Result-of-extending-lifetime-of-oil

Example picture of extend the lifetime of oil.

What if the oil lifespan is exceeded?

comparison-with-generic-oil
In case the oil life is stretched, and the recommended oil drain interval has been exceeded, the medium sized particles will react further and form bigger particles which cannot be solved in the oil anymore. The particles will settle down in the machine under the form of hard carbon deposits, lacquer or sludge formation, all depending how far the oil drain interval was exceeded. A list of consequences this will have: - Deposit formation in areas like coolers and valves but also on the oil vessel & element. - The vicious oil will be more acid and will start attacking metals & rubber materials. Important extra effect is that the oil life of fresh oil poured in such a machine will be much lower! This due to the deposits which will still be present in different areas of the machine and the completely overaged residue of the old oil. Depending on the situation, the oil life could be reduced easily by 50% and in some cases much more to even just a couple of 10 hours!

How often should I change compressor oil?

Atlas Copco lubricants are a unique blend of chemical properties, engineered for optimal performance in their dedicated functions. These carefully selected additives interact in the right proportion to obtain optimal overall performance from your compressor. Also, we are having an oil to match the requirement of each condition of compressor.

Herewith you can find an overview of the lubricant portfolio for oil injected screw compressors. For extreme conditions, which is the case for machines running in the Middle East region, the Atlas Copco synthetic portfolio is the way forward.

Apart from the non-foodgrade, premium lubricants, like Rs Ultra & Rs Xtend Duty, a NSF-H1 approved oil is available which is an oil specifically designed for OIS machines running in food and beverage, pharmaceuticals & packaging industries. 

Atlas-Copco-lubricant-portfolio

Get in touch with us. Describe your air compressor application, ambient conditions, workflow pattern and maintenance intervals to our experts and they will identify the Compressor Oil from our portfolio that will meet your needs.

Lubricants

Air Compressor Oil Change: Lifespan, Roles and How to do It

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