Updated:
By: Brad Taylor

How to use and maintain inline filters for you air compressor

Do you need an inline filter for your air compressor? Chances are, the answer is yes! Inline filtration is the key to clean, reliable compressed air. Here’s everything you need to know about selecting, installing, and maintaining inline air filters for your air compressor.

What Is an Inline Air Compressor Filter and Why Do You Need One?

The inline air compressor filter removes oil and particulates from your compressed air supply. Compressed air contains contaminants when it leaves the compressor including oils, particulates, and even microorganisms. The inline compressor filter captures these contaminants before the compressed air meets your production environment. This ensures that the air that is used to power your machines and processes is as clean as required.

The quality of compressed air is important. Contaminants in compressed air can build up within pneumatic equipment and in the compressed air system itself. This can lead to early failure of valves, cylinders, and other moving parts in pneumatic equipment. For some applications, such as paint lines or food processing, contaminants in the compressed air supply can lead to quality issues or even health and safety concerns. Contaminant buildup in compressed air piping will reduce the overall efficiency of the system.

Removing Contaminants from Compressed Air

The air coming directly out of the air compressor needs clean up to a level required by your process.

  • Particulates enter the air compressor with the intake air. The higher the particulate concentration in your ambient air, the more will end up in your compressed air supply. Contaminants may include dust from manufacturing processes as well as pollen, microorganisms, and other materials brought in from the outside. Your air compressor may already come equipped with an intake filter to capture larger solids before they enter the compressor, but these filters do not capture everything. In addition to contaminants that make it past the intake filter, a certain amount of particulate comes from the air compressor motor itself.
  • Oil in the airstream comes from compressor lubricant. Due to the heat involved in the compression process, some of this oil vaporizes during normal compressor operation. This vaporized oil coalesces back into a liquid as the air cools. The oil that is allowed to accumulate inside the compressed air system or pneumatic tools can provide a breeding ground for microorganisms.
  • Compressed air may also contain large amounts of water vapor. As air is compressed, moisture is squeezed out of it. Air dryers are the most efficient way to remove excess moisture. Read more: Getting Rid of Moisture in Your Compressed Air System.
    However, they do not remove oil and particulates. For that, you need an inline filter.

The inline compressed air filter sits between the air compressor and the point of use. The inline filter captures the remaining particulate that makes it through the intake filter as well as oils and contaminants produced by the compressor motor.

  • Standard particulate filters rely on filter media that captures solid particulate and lets air flow through. Particulate filtration efficiency will depend on the filter media. Most particulate filters capture particulate down to 1 micron in size. However, these filters are not designed for oil mists. If you have high levels of oily contaminants, these filters can quickly become overloaded.
  • Coalescing filters remove aerosolized oil mists from compressed air as well as dry particulate. They use multiple layers of a very fine mesh to trap liquids and fine particulates. Coalescing filters are generally preferred for inline filtration for compressed air because they remove both oil and dry particulate and have superior overall filtration performance.
  • Activated carbon filters remove oil mists and vapors and have a higher level of filtration efficiency than coalescing filters. They also remove many other types of gases and vapors in the air, making them ideal for environments with chemical vapors in the intake air or applications that require a high degree of purity. These filters are not designed to remove dry particulate, so they should be used in combination with a coalescing filter for maximum efficiency. A 2-in-1 inline filter provides both types of filtration.

How Clean Does Compressed Air Need to Be?

Clean, dry compressed air is a benefit for any operation, but the tolerance for contaminants in compressed air varies widely by application. Filtration efficiency is measured by two parameters: the size of solid particulates captured (measured in microns) and the amount of oil carryover in the filtered air (measured in parts per million, or PPM).

  • If you are using air for pneumatic purposes (to power tools, machinery, and conveyors), then a standard particulate filter may provide sufficient filtration. Choose a basic coalescing inline filter to also remove oil mists.
  • Paint lines and similar applications require a higher degree of purity, with particulate removal down to 0.1 micron and very low levels of oil carryover. High-efficiency coalescing inline filters can provide this level of purity.
  • Processes such as food processing, pharmaceuticals and nutraceuticals, and medical applications require compressed air of very high purity. Adding activated carbon filtration will remove gases and vapors from the air.

How to Install an Inline Air Filter for an Air Compressor?

Inline compressed air filters can be placed anywhere in the compressed air piping systems. Some of the most common placements are the following:

Depending on your application and air purity requirements, you may install multiple inline filters at different places in your system. Inline filtration can be easily configured to your specific needs.

Filtering compressed air before it enters the main distribution piping is usually the most efficient solution. Point-of-use inline filtration can be costly to install and maintain. Efficient inline filtration of air before it enters the compressed air distribution system can usually eliminate the need for point-of-use filtration.

How Often Should You Change the Inline Filter for Your Air Compressor?

As a general industry rule, it is recommended that you change your inline air compressor filter at least once a year or after 8,000 hours of operation. Like all filters, inline air compressor filters require regular maintenance to ensure that they maintain their filtration efficiency. If you do not change your filters frequently enough, you will notice increased pressure drop as the filter becomes more loaded. This will reduce the efficiency of your compressed air system and drive up energy costs. An overloaded filter will also impact the quality of your compressed air.

Aire Tip: Keep an eye on the differential pressure gauge to know when it is time to change your inline filter.

There are a few variables that will impact filter life and necessitate more frequent filter changes. These include:

  • High oil carryover from the compressor equipment, causing the inline filter to become saturated faster than usual
  • Increased amounts of particulate due to corrosion within the piping and/or equipment
  • Improperly sized filtration

Need an inline filter or still have questions? Call us and our professional team will help you out!

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