How to Choose a Compressed Air Dryer

Compressing air also concentrates the water vapour in it. As the air cools in the pipework, that water drops out as liquid and ends up in your tools, paint and machinery. A dryer removes most of it before it gets that far.

Why you might need one

• Water spitting from tools or hoses
• Fisheyes and blotches when spraying
• Rust inside pipework and receivers
• Pneumatic cylinders and valves wearing early

Refrigerated dryers

These cool the air to a low temperature, usually around 3 degrees Celsius, so most of the moisture condenses and is drained off. The air is then reheated slightly so pipework does not sweat.

• Suit most workshops, garages and general industrial use
• Lower running cost and simple to maintain
• Not suitable where pipework runs below freezing

Desiccant dryers

These pass air through a drying material that absorbs moisture, giving a much lower dew point.

• Suit outdoor lines, cold stores and sensitive processes
• Need more upkeep and use some purge air

How to size a dryer

• Match the dryer's flow rating to your compressor's free air delivery, or to your peak air use if it is higher
• Check the rating is at your actual operating pressure and inlet temperature, as hot or low pressure air reduces capacity
• Allow a margin if you plan to add equipment

Get the most from it

• Fit a filter before the dryer to remove oil and particles
• Give the dryer room to breathe and keep its condenser clean
• Check the condensate drain works

Common questions

Is a water trap enough?

A water trap only catches liquid water that has already formed. A dryer lowers the dew point of the air itself, so the water does not form further down the line.

Refrigerated or desiccant?

Refrigerated suits most workshops and is cheaper to run. Choose desiccant if your pipework sees freezing temperatures or your process needs very dry air.

Where does the dryer go in the air line?

Usually straight after the compressor and its receiver, with a filter ahead of it. Our workshop air line guide shows the full layout, and FRL units go at the point of use.

Tell us your compressor model and what you are using the air for and we will recommend a dryer. Call 021 435 5424 or visit us in Little Island, Cork. Browse our refrigerant dryers and air compressors.