Why it is important to dry compressed air and how to do it

Getting the right pressure and flow of air for your requirements is only part of the picture.  Ensuring compressed air has the right level of moisture content is vital to ensure maximum uptime of your air powered equipment and ensure an efficient performance.


Where does the water come from?

All atmospheric air contains a level of water vapour, and the amount of water vapour varies according to the ambient temperature of the intake air.  At higher atmospheric temperatures air carries more water vapour and at lower temperatures it carries less.

When the intake air is compressed it is warm, however as it cools the moisture within the air condenses into a liquid.  The point at which this happens is called the saturation point – or ‘dew point’ and this can lead to liquid building up in the compressor pipework.


Why do I need to remove water from the compressed air?

If water is not removed from the compressed air it can cause a number of problems further down the line for the air powered tools or pneumatics:

  • It can wash away any lubrication on moving parts which can lead to rust damage
  • It can cause scale to build up and clog parts leading to poor performance and downtime
  • It can freeze in cold weather causing the equipment to fail
  • The water can carry dust, oil and particulates leading to a sludge building up on moving parts such as valves reducing efficiency and performance
  • On assembly lines where compressed air is used, for example in bottling plants to blow bottles clean and dry, any water present may lead to germs or toxins developing, such as legionnaires disease which could ultimately contaminate the bottled products


What drying options are there?

The most common types of dryers used are:

Refrigerated Dryers – These are the most common and used for situations where the dew point is between +2˚C to +10˚C. A benefit of these dryers is that they do not use purge air (or in other words require the use of any of the output compressed air flow to operate) therefore they are ideal for situations where the air tools require the maximum flow output of the compressor

Desiccant Dryers – These are used for situations when a high standard of air is required for the end use application.  They are ideal for more extreme conditions where the dew point is around -40.  In order to operate however they can consume up to 25% of the output air flow of the compressor.

Membrane Dryers – These are very efficient. They dehumidify and depress the dewpoint as air enters the system.  They are easy to maintain and are quiet however these also too require up to 25% of the total compressed air flow to operate.


How do I select the right dryer?

  • Identify if the total compressed air flow is enough to meet both the air tool requirement and any dryer purge air requirement, to ensure maximum efficiency
  • Identify the required pressure dew point for the application. This can usually be found in the air tool specifications
  • Know the end use of the air and any particular moisture requirements for example a bottling plant or team blowing fibre optic cable into ducts will have different moisture requirements to a hand-held tool operator.
  • Know the ambient temperatures in which the air powered tool will operate


It is often best to consult a compressed air engineer to identify the best dryer option for your requirements.  The Vert team are on hand to answer any questions you may have and to help specify the correct dryer option for your application.  Give us a ring or drop us an email at sales@vertrotors.com

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