Types of Air Compressor Filters and How They Work
Air compressors use ordinary atmospheric air to power tools and processes in diverse industries. However, although we breathe air without a second thought, your compressed air system will need filtration. Contaminants from the air, even water vapour, can cause problems for your compressor, reducing efficiency, contaminating products, and damaging your compressed air system.
Every compressed air system will need some filtration, and some users will have strict quality standards, such as ISO 8573-1, that they must meet. Whatever end of the air purity scale you need to be on, choosing the right filters is critical, not an optional extra.
Contaminants and compressed air
Compressed air can contain a range of contaminants. Some, like dust, water vapour, and microorganisms, will come from the intake air. Other contaminants, like oil, can come from the compressor itself.
Because gas is highly compressible, even microscopic contaminants form a bigger proportion of the compressed air, creating a risk for products and potentially damaging tools. Water vapour, which condenses as the compressed air cools, is one of the worst contaminants, causing corrosion and harbouring microbes.
Types of compressed air filters
The level of filtration you need will depend on your operational needs; just powering pneumatic tools will not require highly pure air, but some filtration will still be needed.
Particulate filters
As the name suggests, these capture dry particles like dust, rust, and pollen. They are typically micro-fibrous media that allow small air molecules to flow through while capturing larger particles.
Typically, they are the first filters in the compressed air system after compression and help protect equipment downstream from potential damage. They can also be used as part of the air intake if the air is particularly contaminated, for example, if you are drawing air from an area where polluting processes occur.
Coalescing filters
Coalescing filters help remove vapours and aerosols that have not been captured by the particulate filters. As the name suggests, they work by using filters that cause small droplets and aerosols to merge, forming larger droplets that fall and can be drained away.
They also help further purify the air because the drops capture smaller particles that got through the initial filtration. Coalescing filters are essential if you need highly pure air, but their ability to remove aerosol droplets means they can protect any system.
Adsorption filters
Usually, a final stage of filtering, adsorption filters capture the oil vapours, hydrocarbons, and even the odours that have made it through the previous filters. Activated carbon filters are the most common; they adsorb the remaining contaminants using a granular media with a large surface area.
The filters are highly effective, meaning that the air that passes is highly pure. However, that effectiveness requires prior filtration to avoid the adsorption filters becoming rapidly clogged.
Other filters
Your system may also have oil filters and mist eliminators, which help capture oil and liquids. But, although they sound like coalescing filters, they should not be confused with them.
Oil filters are used in the compressor itself. They capture oil and metal fragments, helping to protect the compressor and prolong the oil life.
Mist eliminators use pads or vanes to separate larger droplets mechanically. They are often used with coalescing filters to manage larger volumes of liquids without a pressure drop.
Types of Air Compressor Filters and How They Work
How different types of compressed air filters work together
For most compressed air systems, filtration works as a process. It is not a case of placing a single filter but a series of filters to achieve the required standards.
Particulate filters are used to capture the largest contaminants, coalescing filters are used to trap vapours and aerosols, and adsorption filters are used to capture any contaminants that are left.
As well as each stage handling a specific type of contaminant, proper sequencing helps prolong filter life, avoid unnecessary pressure drops, and produce high-quality air.
Getting the air quality you need
Ensuring you have the quality of air you need, as well as the pressure and flow rate your processes use, will dictate the filtration requirements of your compressed air system and whether you need ancillary devices like compressed air dryers or separators to help you meet your quality requirements.
ISO 8573-1 will help you identify the exact standards you must meet for your use. Other factors, like intake quality and ambient conditions, will dictate measures you might want to take to protect your system.
Getting your air filtration right is about clean air and maintaining your compressor and the compressed air system to make it as cost-effective as possible.
How to maintain air compressor filters
Filters are consumable items. The contaminants will block and clog the filters over time, and the efficiency of adsorption materials will gradually degrade. There is often no obvious sign until symptoms like pressure drops signal that changes are overdue.
Manufacturer guidance will give indicative change frequencies, but you will also need to factor in your usage patterns, ambient conditions, and sometimes even things like the weather – a hot and humid summer can be bad news for an air compressor.
Choosing the best air compressor filters for you
Getting the right filtration means balancing filters, your needs, and cost. The best solution gets you the purity you require, but no more, so you can avoid the costs of over-specified air, making your compressor work harder, and requiring more frequent servicing and changes.
Search Air works with compressors that produce the purest air possible and hard-working compressors where power, rather than purity, is paramount. Whether it is a new or existing system, our expert engineers can help you find the right filtration. Once in place, we can offer regular servicing, assuring you that your filters perform exactly as they should.
If you want to know your filters are working exactly as hard as they should, just contact us for a consultation, and we can show you why thousands of compressors rely on Search Air.