Opportunities for enhancing compressed air system performance

How to plan, install and operate a shop compressed air system

Different environments, different air treatment needs – What you use the air for determines the level of air quality needed and the environment directly impacts the type and degree of air treatment needed to reach that air quality. Here are some basic recommendations to achieve clean, dry air in different environments:

  • Moderate climate: Compressor, tank, refrigerated dryer (with built-in filtered separator) and a coalescing filter (if needed).
  • Hot, humid climate: Compressor, liquid separator, tank, refrigerated dryer (may need to be slightly oversized) and a coalescing filter (if needed).
  • Hot dusty environment: Compressor, liquid separator, tank, refrigerated dryer (may need to be slightly oversized), coalescing filter (if needed) and particulate filter.
  • Cold environments: If you have any hoses or lines going outside where it is cold (below 40 degrees F), you may benefit from putting a membrane or desiccant dryer on that line before it goes outside. This will further reduce moisture that might freeze up tools.

These dryers consume compressed air so you only want to use them for lines that get cold. If your main airline goes outside before branching to the users, you should consider a desiccant dryer sized for the whole system.

Compressor selection – Compressor selection impacts air quality. Rotary compressors operate much cooler than piston units, plus they have more effective after-coolers. They condense a lot of moisture into liquid as it’s leaving the compressor for easy removal.

Another consideration is compressor oil/fluid. The piston design allows much more oil to pass from the compressor. Rotary units have separation systems that clean and recirculate nearly all of their compressor fluid.

Liquid separators – Liquid separators remove moisture that has already condensed to liquid. These simple and inexpensive devices provide great first-stage moisture separation after the cooler on a rotary compressor.

With piston units, however, it is sometimes better to go into the air receiver tank before the separator.

Air tanks usually provide a bit of cooling that condenses some more moisture vapor to liquid before the air heads into the dryer. Most refrigerated dryers have liquid separators built-in.

Particulate filters – Systems in high-dust areas will benefit from particulate filters. Coalescing oil removal filters are recommended if there is a lot of oil carry-over and they are essential if the air is used for spraying paint or sensitive equipment.

Drains – Coolers, tanks, dryers and filters will separate contaminants from the air, but to actually remove them from the air system, they need drains. Spend the extra money for a high-quality automatic drain for liquid separators, receiver tanks and coalescing filters. Any decent refrigerated dryer has one built in.


Site considerations – Compressors are often installed where their noise, vibration and heat will least bother staff and customers, rather than where they’ll best perform and be easily serviced. Compressors need good, clean inlet air and ventilation to maintain proper operating temperature and long operating time, but they are commonly found in dark, dirty and hot rooms. This is not a recipe for success. Provide good lighting and good access for maintenance.

Compressor considerations – Though more expensive, rotary compressors run much cooler and quieter, presenting more flexibility in where you put them. Many air users opt for less expensive piston machines and then build special rooms for the compressors to isolate them. Before going this route, consider the cost of construction and lost floor space.


Consider all the facts when setting up a new shop or retrofitting an existing facility. Look at capacity and the potential for growth, and make your selections based on an honest evaluation of available technology.

There are formally trained compressed air professionals who can advise you on the right system for your applications and your day-to-day needs. We recommend you consult them, just as you would an HVAC company when putting in central heating and air conditioning.

After investing in the right equipment, make sure you have a preventive maintenance plan in place. Routinely check for leaks and replace filters as recommended.

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