What air treatment equipment is recommended for industrial compressors?

Ensuring the quality of compressed air in industrial settings is no trivial matter. As air compressors compress ambient air, unwanted elements like dust, dirt, and oil are also concentrated, necessitating their removal to varying degrees, depending on the end use of the compressed air. 

Inadequately cleaned compressed air can hinder manufacturing processes and affect the efficiency of air-fed equipment. This post delves into the heart of this matter, discussing the equipment recommended for air treatment in the context of industrial compressors. 

Air Treatment in an Industrial Setting

Industrial air compressors are available in various types, depending on the need and sought-after specifications. The primary choice when selecting one is between an oil-injected compressor (which benefits from added filtration) and an oil-free compressor. Both are covered in a little more detail further into this article.

While we may think of industrial air compressors as the main equipment, they’re only roughly two-thirds of the capital investment. The other one-third goes into filtration and drying systems relating to air treatment, rather than compressing the air.

Air Flow and Pressure Rate

Air pressure and flow capacity are important factors to consider. While your business may choose between a rotary screw or piston-based air compressor, it also must be sized properly to produce the necessary airflow and pressure levels to ensure it is fit for purpose.

UK ISO Standards for Compressed Air

Looking beyond that, the next consideration is the air quality and reliance on a dependable air treatment process.

In the UK, they developed ISO standards for air quality in an industrial setting. The ISO-8573-1 standard provides specifics on compressed air purity classes, in respect of oil, water (or vapour), and particulate matter (dust, dirt, etc.).

It depends on the need and purpose for using compressed air as to what classification is applicable, and the air treatment equipment required to achieve and maintain that standard.

Oil-free Compressors vs Oil-injected Compressors for Clean Air

Returning to the subject of compressed air classes for a moment, these are relevant for UK businesses because needs must match purpose.

Compressed air used in a food factory, big pharma, or electronics production is necessarily cleaner and requires cleaner air systems. Other uses for compressed air need not be as exacting, which is relevant when selecting an industrial air compressor system.

Oil-free Compressors

Specific industries rely on compressed air that’s free from oil vapour or other forms of oil-based contaminants.

To achieve adequate performance without oil used as a lubricant, the compressor element of oil-free compressors is treated with a coating. It does make the OF compressor considerably more expensive than an oil-injected compressor, which also requires additional air filters.

Oil-free compressors use a particulate filter, but an oil coalescing filter is most often not required. The particulate filter is unavoidable – it removes particulate and dust from the input of ambient air. Fewer filters help avoid as many potential reductions in air pressure as possible.

Oil-injected Compressors

Oil-injected compressors are far more common in facilities requiring compressor air systems. Their affordability from a capital investment standpoint sets them apart.

Oil is added as a lubricant, sealant, and to assist with cooling too. Both a particulate filter and an oil coalescing filter are required. Multiple filters do reduce the air pressure levels for an oil-injected compressor, sometimes requiring higher pressure settings to compensate for it, adding to energy costs.

Furthermore, oil condensate management is required to remove oil from wastewater, making it possible and legal to dispose of into a foul drain. A UK trade effluent consent authorisation is needed for this.

With proper filtration and other systems applied, it may reduce oil contaminants to 0.01 of a micron. This is sufficient for many compressed air uses. Below this contaminant level, or to remove hydrocarbon vapours, carbon filters are effective.

Of course, additional pressure drops might occur with additional filters, and this may reduce compressed air quality. Ultimately, it’s a trade-off.

Dryers to Remove Moisture from Compressed Air

Compressed air systems rely on a drying process to remove moisture. These operate in different ways depending on the selected dryer type.

High moisture levels are problematic with compressed air. Water vapour within moist air may ultimately transform into a liquid form. As such, it’s referred to as one of the potential contaminants.

Water within compressed air potentially damages pneumatic tools when levels are excessive. Also, in some other scenarios, the driest air is required to complete the manufacturing processes.

Air compressors include a centrifugal process – or other approaches to moisture separation – to extract droplets from the air. While it works well, it does not remove all H2O. Dryers are needed to remove the remaining moisture from compressed air.

Dryers fall into two types — Refrigerated Dryers and DesiccantDryers:

Refrigerated Dryers

Refrigerated dryers are lower cost, perform well, and are the most common.

This type of dryer uses a refrigerant – like a fridge – to chill the air. The refrigerant dryer causes water vapour to become liquified and the water removed through the drainage system.

There are limitations to this dryer type. Only dewpoints at or above +3°C are valid for the dryer to operate. Furthermore, when temperatures reach near the freezing point, there is a significant risk of frozen pipes and the refrigerant not working as expected. Therefore, locations that drop steeply in temperature during certain seasons might find a refrigerant dryer less than optimal.

Desiccant Dryers

Desiccant dryers are more adaptable. However, the capital investment is far more than for refrigerated dryers.

These dryers use desiccant media beds to collect and remove H2O molecules. The desiccant is used to cleverly attract water molecules from the air. The materials used include silica gel, activated alumina, among other types.

Pressure dewpoints reaching down to minus 70°C are possible by using regenerative dryers. Found mainly within UK industries that either need to operate outdoors or in varied, somewhat extreme temperatures, regenerative dryers have their place.

The downsides to regenerative dryers are several. They use two beds – one that’s drying, and the other regenerates by removing collected water molecules. As a result, it reduces its capacity and consumes generated compressed air as part of its operation.

Lastly, blowers and heaters are further options to remove water from compressed air. This is done at the expense of additional capital investment and higher energy requirements.

Get in Touch with Anglian Compressors

To ensure you are selecting the right product, call the Anglian Compressors team for expert air treatment guidance.

Contact us below.