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Compressed Air Filter

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What's The Compressed Air Filter?

A Compressed Air Filter or air line filter is a important device to filter impurities from atmospheric air or the compressed air.

Air leaving a standard screw or piston compressor will generally contain high water mist, as well as a high concentration of oil and other particles.

And make compressed air aviable for usage. Normally we installe it downstream of the compressor output port or in the compressed air line. And we also assemble on the machinery, or the pneumatic system. When we assemble the filer, regulator and an oiler to a aggregation, it is called air set or air source treatment.
Similar with the air dryers, they are a crucial part of the air treatment process to make sure your compressed air is clean and safe to use. Therefore increase your equipment’s life span.

The Structure Of The Compressed Air Filter

The Following figure shows a typical air filter’s structure.

Components Found In Compressed Air Filter

Inlet:

The air compressor intake or inlet is where air enters the filter. There is an internal plastic ring with the small slant vane that forces air downward into a spiral. It’s important to get the right size inlet rather than using a filter smaller than the line.

Filter cap:

This component directs airflow through the filter. Normally you will find the direction mark on the outside of the filter. The ttention to that will prevent you from installing it backward.

Air path:

This is the actual path the air follows as it spins like a cyclone and passes through the air filter itself.

Compressed Air Filter discharge:

This orifice allows air to leave the filter, and it should match the inlet size. If the filter discharge is too small, it will restrict the flow of air.

Filter element:

The filter itself is what takes contaminants out of the air, catching particulates over time. Eventually, filters become clogged and we should cleaned or replace it. Normally the filtration precision is 40um. But there are other types to choose according your request.

Air compressor filters catch particles so small even measured in microns. One micron is one-millionth of a meter. For scale, the width of a human hair is usually at least 70 microns. Fine particulate filters can remove particles as small as five microns. While a general-purpose filter will catch particles down to 30 or 40 microns in size.

Particulate filter:

When using a fine particulate filter, the risk of immediate clogging is significant. To keep air flowing while still capturing minuscule particles, it’s a good idea to use a fine particulate filter. The particulate filter in tandem with a general-purpose filter up-stream is a great method. That way, we could wipe off the larger particles before they can clog the finer filter.

Filter bowl:

The bowl is the biggest part of the filter that you can see. we insert it to the cap and thread or twiste and fianlly lock into place.

Filter Pending Space:

The contaminants, water and oil collected by the filter all end up in the pending space. You will usually find a barrier hanging from the filter bottom, preventing debris from back into the air.

Drain Valve

What's the drain valve?

Drain the collected contaminants and debris out of the cup. For most filters, we need to drain manually, but others have float-operated or electric auto drains.

Internal Float Drains valve start with the least expensive variety of auto drain, the internal float drain. Internal float drains insert into the bowl of a coalescing filter or moisture separator. To know more detailed information about the auto drain valve.

How The Compressed Air Filter Work?

First: the compressed air come into the filter from the inlet. The air come through the flow deflector, and become the rapidly rotating air stream.

Second: The rotating air stream will thrown off the water and part of the particles due to the centripetal force. The contamination attach on the inner wall of the cup. And finally fall into the pending space.

Third: The air traverse the filter element, and the rest of the tiny dust will be blocked outside of the filter element.

Fouth: The clean air get out from the inner side of the filter element, and flow to the outlet.

Types of compressed air filter

Particulate filters

Particulate filters remove particulates from the air stream by trapping contaminants on the media. The filter element design and material determine the size of the particles it can trap. So particulate filters have varying degrees of filtration.

Coalescing filters

Coalescing filters remove water and aerosols of liquids like oil by coalescence. Coalescence is the process of trapping smaller droplets until they combine into larger drops. The big drops will fall out of the air flow. The structure and type of media determine how much aerosol can be remove. So they also have varying degrees of filtration.

Vapor Removal Filters:

Vapor removal filters are typically used to remove gaseous lubricants that will go through the coalescing filter. Because they use an adsorption process, vapor removal filters should not be used to capture lubricant aerosols. Aerosols will quickly saturate the filter, rendering it useless in a matter of hours. Sending air through a coalescing filter prior to the vapor removal filter will prevent this damage. The adsorption process uses activated carbon granules, carbon cloth or paper to capture and remove contaminants. Activated charcoal is the most common filter media. It has a large open pore structure; a handful of activated charcoal has the surface area of a football field.

Dry Particulate Filters:

Dry particulate filters are usually employed to remove desiccant particles after an adsorption dryer. They can also be implemented at point of use to remove any corrosion particles from the compressed air. Dry particulate filters operate in a similar manner as a coalescing filter, capturing and retaining particles within the filter media.

Activated carbon or steam filters

They are used to remove odors and impurities through the process called “adsorption”. Adsorption is the chemical process by which the activated carbon filter naturally attracts oil vapors. These filters are very expensive however.
They also require a dust filter to prevent small particles of coal from bursting and entering the airflow.

Compressor Intake Filter

The intake area of any compressor is an essential part of air pressure and flow. It draws in air from the surrounding environment through the pump for compression.
To ensure reliable performance, you should have an intake filter. Many models come with one already installed, but some smaller compressors don’t include. If your compressor doesn’t have one, installing one is essential.

Intake filters pull out some of the harsher particulates, protecting the internal components of your processor. By doing so, they protect your equipment from dirt and debris. It prevents the contaminant to clog anything, or stick to the interior elements or inhibit. Intake filters also protect your other filters. By providing an initial round of particulate removal, you’ll increase the longevity of your other filters. Also prevent clogging and provide better air pressure with fewer filter replacements.

How to Select a Compressor Air Filter?

Selecting the best compressor air filter will go a long way to guarantee system efficiency.
You can consider the following factors when selecting a compressor air filter:

Type of Application

Different applications require different types of compressor air filters.
Each filter has a different set of filtration requirements and fittings. It’s better to refer to the requirements of your filtration. Or consult a reputable company before settling for a given type of filter.

Filter Micron Rating

Similarly, the cleanliness required for the compressed air will determine the micron rating of the filter you select.
You should select a filter that will achieve the desired level of cleanliness and still maintaining good service intervals.

Flow Rate

The size and of the filter you select will depend on the application level of airflow.
Understanding the maximum allowable pressure drop will assist you to decide on the best size of a filter to select.
The manufacturers will provide a chart showing the pressure drop versus the supply flow.
These charts indicate the performance of a filter at a given intake pressure.
Look through the chart and select the models whose port size and other features meet your system requirement.

Efficiency and Quality

You should choose a filter that will effectively remove the contaminants at the desired level and with a minimum pressure drop.
Note that filters might have similar micron and flow rate rating but significantly differ in their effectiveness in removing contaminants.
High-performance filters might cost you more initially but will give you better results compared to ordinary filters.

Temperature

At what temperature will your compressed air filter operate?
High performance filters are available for high temperatures (over 450°C).

Environmental standards

Compressed air filter is subject to the ISO 8573 standard. That specifies the purity classes of compressed air for the presence of solid particles, water and oil, regardless of their location in the compressed air system.
This standard also provides general information on pollutants in compressed air systems. Also refers to other parts of ISO 8573 with regard to the specification of compressed air purity requirements.
Lastly, the ISO 8573-1:2010 standard also identifies gaseous and microbiological pollutants.

When to Replace Your Compressed Air Filter?

For comppressed air filter to work efficiently and provide the best purification possible, they require regular maintenance and replacement. There are general guidelines you can follow. But no specific designated operational period.
Your operators should create a routine of checking, draining and replacing filters based on use. If they use the compressors for long periods daily, the maintenance schedule should be more frequent. The daily checks and regular cleanings is essential.

Two of the most significant signs are changes in air output and signs of wear or oversaturation. Checking them regularly will help them determine how much longer their filters will last to order a new one.

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