Air dryers: FAQs

Air dryers: FAQs

Air dryers remove any condensation from the air compressed by your air compressor. Questions about them? Find answers to the most frequently asked questions here. 

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Estimated time to read: 3 minutes

September 12, 2022

Air dryers: Frequently Asked Questions

Air dryers: Isn't air dry?

Air has moisture and water vapor in it. When your air compressor compresses this air, the air – and the moisture – are heated. As it cools, the air has less ability to hold this moisture. Eventually, the air reaches a ‘dew point’. This is the temperature where the water vapor condenses into droplets. Known as condensation, these droplets are basically just water, but still have the potential to cause great damage as they flow through your compressed air line, machines and tools. 

Air dryers: Do you need one?

We recommend using an air dryer to remove condensation and moisture from your compressed air. Why? The condensation will result in: 

• extra maintenance and downtime;

• a greater likelihood of corrosion and rust in boilers and piping;

• oil and lubricants in pneumatic tools and cylinders becoming contaminated and even washed out;

• blasting materials like sand clumping together;

• a kind of fogginess on surfaces you spray with compressed air.

A compressed air dryer removes the unwanted condensed water. The result? Dry air. No condensation. Less downtime. And one less worry to keep you awake at night.

What types of air dryers are there?

The most common type of air dryers are cooling air dryers and adsorption air dryers

How do cooling air dryers work?

ALUP ADQ Air Dryer

Cooling air dryers, also known as refrigerated compressed air-dryers, circulate a cooling gas around your system, dropping temperatures to 3ºC or lower. This causes condensation; the dryers then remove it from the air before causes any damage. The process may sound familiar: it’s what domestic air conditioners do.

Worried about the effects of these cooling gases on the environment? Good news: Our ALUP dryers use R134a, R410A or R45A cooling gases. They have no influence on the ozone layer and less environmental impact than any other cooling gases. 

How do adsorption air dryers work?

ALUP adsorption dryer AD1300

Adsorption dryers are also known as desiccant dryers and ‘getters’. They blast moist air over hygroscopic material that removes the moisture from the compressed air. An obvious question: What’s hygroscopic material? The answer: Any material, whether it’s a solid or a liquid, that attracts moisture to it. This material will ‘get’ and hold the moisture. (Now you see why they’re known as ‘getters’.) However, this material needs to be replaced; otherwise, it will become saturated and stop removing moisture from the air. For this reason, adsorption dryers are usually used after a cooling air dryer when most of the moisture has already been removed. 

Adsorption dryers easily reach temperatures below 0ºC. In fact, they’ll reach dew points of -20ºC, -40ºC or -70ºC. Cool, huh?

Which compressed air dryer should you choose?

The choice of a compressed air dryer depends on what you’re using the compressed air for. There are often regulations involved (such as BRC, BCAS, IFS and Pharmacopoeia to name a few).

A cooling dryer is the most commonly used dryer for compressed air. By cooling the temperature to around 3ºC, most of the moisture condenses and is removed, leaving the compressed air suitable for 90% of applications. ISO 8573-1: 2010 purity class 4 is met by using a cooling dryer.

However, an adsorption dryer is a must if you need to reach a lower dew point. Adsorption dryers have pressure dew points of -20ºC, -40ºC and -70ºC. Adsorption drying is often used in the food, pharmaceutical, medical and chemical sectors.

Any other questions about air dryers or compressed air? Wondering which air dryer is best for your specific needs? Get in touch with ALUP for help, advice and expert insights.