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Ensure the compressed air dryer is suitable for Australian conditions

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article image Air Dryer

Southern Cross Compressors Australia Pty Ltd  advises its clients on selecting the most suitable air drying products tailored to Australian conditions to enable them to get the most out of their compressed air systems.

Though air dryers are rated at the worldwide standard of 25°C ambient air temperature, they need to be re-rated for Australian conditions. 

This can mean that one may need to buy an air dryer that will handle double the flow of compressed air to that shown on the brochure.

Typical correction factors used to rate air dryers include:

  • Nominal air dryer flow rate
  • FC1 = Air pressure correction factor (typically most compressors operate at 7 Bar)
  • FC2 = Ambient air temperature (for the hottest working days of the year)
  • FC3 = Air dryer inlet temperature (generally 10ºC above the ambient air temperature)
  • FC4 = Load factor (Pressure dewpoint at which water vapour condenses to form water: 3ºC dewpoint)
Southern Cross offers air dryers built for Australian conditions and are rated based on the formula: Real Flow Rate = Nominal air dryer flow rate * FC1 * FC2 * FC3 * FC4.

For instance, an air compressor with a 10 Bar output, sized to 40ºC ambient temperature, with a properly setup aftercooler on the compressor, which will result in 10ºC above the ambient, equalling 50ºC with a 3ºC dewpoint will have a formula as follows:

  • FC1 = 1.18 for a compressor system running at 10 Bar
  • FC2 = 0.85 for ambient temperature of 40ºC where the air dryer will be sited
  • FC3 = 0.87 for air dryer inlet temperature (where the aftercooler is correctly sized)
  • FC4 = 1.00 at 3ºC at which most of the water drops out of compressed air
Therefore, Real Air Dryer Flow Rate = Nominal air dryer flow rate from brochure * 1.18 * 0.85 * 0.87 * 1.00, or Nominal air dryer flow rate from brochure * 0.87261.

This example shows that the brochure rated air dryer is only capable of handling a flow of 87.261% of air flow shown in the brochure. 

Southern Cross therefore advises clients to upsize their air dryers to the hottest day operating conditions expected to allow most of the condensate to be removed from their air compressors.

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