Three Common Filtration Strategies Used In Compressed Air Systems

Posted on: 4 May 2017

Compressed air needs to be kept clean to protect equipment, end products and users, too. The provision of clean air is accomplished through several means, such as the practice of preventative maintenance, but one important way to keep compressed air clean is by the use of filtration.

Compressed air filtration isn't a one-size, fits-all approach; instead, there are several filtration strategies that should be implemented depending on user processes and production functions. Below are a few of the most common air filtration systems in current use.

Particulate Filtration

Particulates, which are fine-sized solid particles, pose a serious threat if permitted to become suspended in the compressed air stream. Particulates can cause several types of harm, including equipment and product damage.

For example, solid particulates can be abrasive and wear down internal components inside a compressed air system. In addition, particulates may affect gauges and metering equipment and skew measurements as a result. Worse, particulates can contaminate end products and render them unfit or unsafe to use.

To handle the threats posed by particulates, air compressors are fitted with particulate filtration devices. Many particulate filters can also remove water droplets from a line, which can pose dangers of its own.

When choosing a particulate filter, be sure the flow rate and micron ratings are compatible with your system. If these parameters aren't properly matched, the compressed air flow could be either restricted too much or be inadequately cleaned.

If you are chaining filtration systems together, which is a common practice in compressed air systems, particulate filters are usually placed before any other type of filter.

Coalescing Filtration

In some compressed air systems, coalescing filtration is necessary to provide a satisfactory level of protection. A coalescing filter removes aerosols that become suspended in the air stream; these extremely small particles of oil or water cannot be captured by particulate filters, but they still pose a threat to equipment and downstream operations.

As with particulate filters, coalescing filters are rated by flow rate and the particle size permitted to pass. However, since the particles captured by a coalescing filter are so minute, the micron rating will be much lower than a particulate filter's rating.

Coalescing filters will need to be drained on a periodic basis. As aerosols collect inside the filter, they become visible as liquid droplets and will continue to accumulate until they are released. Many coalescing filters use automatic drains that release accumulated liquids, but be sure to understand how to drain any filters that are utilized in your compressed air system.

Coalescing filters follow particulate filters when placed in a series arrangement of filtration.

Adsorption Filtration

As the particle size decreases, the need for filtration often decreases depending on the specific application. However, in many cases, there are still a sufficient number of contaminants that must be removed before a compressed air stream can be rendered usable.

That is why adsorption filtration is often implemented in compressed air systems. Adsorption filters remove invisible particles that are usually only detectable by smell. Noxious fumes are a possible byproduct of compressed air production, and oily odors are unacceptable in many environments, particularly those involving breathable air.

An adsorption filter removes these vapors through the use of special media and may incorporate multi-stage filtration. For example, adsorption filters are often equipped with activated carbon that attaches itself to microscopic particles responsible for causing odors.

To finish the filtration process, adsorption filters may also contain fiber media that capture larger particles that make it past carbon media.

Unlike particulate and coalescing filters, adsorption filters are rated on a matrix based on parts-per-million (PPM). This scale measures how many particles are suspended in a given volume of air rather than size of the particle; the lower the PPM rating, the more capable an adsorption filter is of stripping all the noxious particles from the air.

In a chained filtration system, adsorption filters are the final stage in the process of overall filtration. Talk to your air compressor rental company for more tips.