Membrane Compressed Air Dryers Technology

Learn how membrane compressed air dryers work

Membrane Air Dryer Working Principle

Membrane dryers are especially suitable as point-of-use dryers or in areas where there is no electrical power supply available. In this article, we're explaining the working principle of membrane air dryers. These dryers make use of a small quantity of compressed air as purge air. The quantity of purge air depends, among others, on the desired pressure dew point. In the HMM series, the membrane bundle is in a pressure-resistant housing. This construction offers the possibility to interrupt the purge air flow by means of an optionally mounted solenoid valve, which can be operated from the compressor on-off contact.

Membrane dryers eliminate water suspended in compressed air using a selectively permeable membrane. This separation membrane is composed of microtubules that retain water when air is circulated through them:


A stream of “wet” compressed air is passed through the membrane leading to water retention with a “dry” stream of air emerging from an outlet on the other side of the membrane dryer:

Water vapour diffuses caused by different partial pressure through the membrane and will be steered out through a wet air outlet. This purge air – saturated with water vapour – is dispersed freely in the environment without any noise and without the need for condensate management.

Typical Purge Air consumption vs pressure dew point of Membrane dryers

Pressure dew point °C 3 -10 -20 -40
Purge air consumption appr.% 15 17 22 24

The membrane air drying technology is an excellent alternative to refrigerant and adsorption dryers. These dryers can be selected independently from the desired pressure dew point and need no maintenance. To protect the delicate membrane surface, particle and oil-fine filtration are required. The appropriate filter combinations are available in our Hankison filter program:

Typical Applications of Membrane Compressed Air Dryers

  •   Control & Instrument Air for outside installations
  •   Ventilation in electr. control cabinets
  •   Laboratory applications where small flows needed
  •   Ex-proof applications
  •   Supply of air for purged bearings (Turn tables)
  •   Point-of-use installations

Criteria to Choose Membrane Compressed Air Dryers

  • Small flows in combination with high-quality pressure dew points
  • No electrical supply is available
  • Ex-proof application in combination with low capital investment
  • Reliability (no rotating parts)