Air oil separator in a Compressor and How Does it Work?

What is air oil separator

What is Air Oil Separator?

An air oil separator, also known as an oil demister, is a kind of oil filter used in compressed air systems, screw compressors, engines, and vacuum pumps to remove oil from the oil-infused air. These separators are an integral part of the compressed air system and play a crucial role in ensuring the efficient and safe operation of the intake system. All major OEM including Atlas Copco, Boge, Kaeser etc uses Air Oil separator in their product design. For more information on air oil separators, including accurate dimensions, light-weight design, and easy installation, please see the product details below.

In this article, we will explore the basics of air oil separators, their functions, and why they are essential components in any compressed air system

What Does an Air Oil Separator Do?

An air oil separator in a compressor is a device that separates the oil from the compressed air. Its primary function is to ensure that the compressed air is free from oil and other contaminants. This is important because oil and other contaminants can damage equipment and tools that use the compressed air. The air oil separator works by using a series of filters and baffles to separate the oil from the compressed air.

As the air enters the separator, it passes through the filters, which capture the oil and other contaminants. The clean air then exits the separator and is ready for use. Overall, the air oil separator is an essential component of any compressor system, as it helps to ensure that the compressed air is clean and free from harmful contaminants.

Why do we Need an Air Oil Separator Cartridge?

An air oil separator separates the oil vapor present in compressed air and returns it to the compressor's oil sump where it is ready to be used as coolant again. The purpose of the separator is to prevent oil carry over and oil (coolant) consumption by removing the oil mist (oil vapor) in the compressed air through the process of compression, allowing it to recycle back to the air compressor to maintain lubrication. Why do we need an air oil separator? Because it ensures the proper functioning and longevity of the compressor, making it an essential component for efficient operation. Use a trusted brand for oil separators to get high quality and reliability.

This ensures that the compressed air remains free of oil droplets at air intake of production equipment , which can cause contamination and damage to equipment that uses the compressed air.

air oil separator

How Does an Air Oil Separator Work?

An air oil separator works by creating a centrifugal force that separates the residual oil from the compressed air. The compressed air enters the separator through a tangential inlet, causing it to spin rapidly. The residual oil in the compressed air is almost completely separated by an air/oil separator, also known as an oil filter, within the pressure vessel or a spin-on separator outside of the pressure vessel through application of the coalescence effect.

The separated oil collects on the outer surface of the separator, also known as a catch can, made of high quality filter media such as glass fiber, filter paper, and glass woven sheet. This efficient combination of filter media minimizes oil flow and losses in the compression system, ensuring a smooth running compressor.

The clean air is then expelled from the separator, while the collected cleaner oil is returned to the compressor's oil sump through a pcv.

Types of Air Oil Separators

There are two main types of air oil separators: cartridge and spin-on. The cartridge type separator uses a replaceable cartridge to filter the oil mist from the compressed air.

The spin-on type separator has a threaded end that allows it to be replaced when it becomes clogged. Both types of separators are available in flange style and cartridge style configurations, making them suitable for a wide range of compressed air systems and vacuum pumps.

How To Install An Air Oil Separator filter?

Installing an air oil separator is a relatively simple process, but it's important to follow the instructions specific to your machine. First, you'll need to remove the old separator by removing the mounting bolts and disconnecting all hoses and electrical connections.

Once removed, clean the area of any debris or sludge, making sure it is free from dirt or contaminants before installing the new unit. Now you're ready to install the air oil separator. Begin by attaching all hoses and electrical connections according to your machine's specific procedure.

Then attach the mounting bolts, checking that they are tight and secure with the bracket before connecting power and filling with oil. This will ensure proper operation of your new air oil separator for many years to come. Although procedures may differ depending on your machine, following these steps should get you started in properly installing an air oil separator.

air oil separator installation
air oil separator replacement

Are air oil separators necessary for air compressors?

Yes, air oil separators are necessary for air compressors. They help to separate out any oil that is present in the compressed air and keep it from entering the system. This helps to ensure that the equipment runs more efficiently and safely i.e. increased engine performance.

Air oil separators also help to reduce maintenance costs by removing oil from the system before it accumulates and causes damage. Additionally, they can prevent corrosion and rust buildup in the compressor itself due to condensation, which can cause premature failure of the unit.

Air oil separators are an essential part of any air compressor setup and should be regularly inspected and maintained for optimal performance.

What happens when an air oil separator fails in Screw Compressor?

When an air oil separator fails, it can cause a variety of problems. It can lead to increased oil consumption, increased exhaust emissions, reduced fuel efficiency, pcv system failure, and even compressor element failure and engine damage. To prevent these issues from occurring, it is important to ensure that air oil separators are regularly inspected and maintained in order to ensure optimal performance and fuel efficiency.

One important aspect to check during maintenance is the differential pressure of the separator, which should not exceed 0.2 to 0.3 bar when the compressor is running loaded. If the differential pressure is higher, it may be time to replace the air oil separator to avoid potential issues.

How Does a Air Oil Separator Increases the efficiency of Intercooler?

The air oil separator is a critical component in an intercooler system that helps increase the efficiency of the intercooler. The air oil separator removes any oil particles from the air entering the intercooler and returns to oil pan, which increases the overall efficiency of the unit.

By separating out oil particles and returning it to the oil pan or oil sump, it reduces the amount of heat generated by the compressor and prevents these particles from clogging up or blocking off any part of the intercooler system. This helps reduce compressor temperatures, reducing pressure drops and increasing overall cooling power. 


Air oil separators are essential components in any compressed air system. They play a crucial role in preventing oil carryover and loss, ensuring that the compressed air remains free of oil droplets and free from contamination. They also play a critical part in maintaining internal systems line the pcv system and the compressor elements working efficiently.

Whether you are using a cartridge type separator or a spin-on type separator, it is important to regularly check and maintain your separator to ensure that it is functioning properly and providing the necessary protection for your compressed air system.

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