Membrane dryers for compressed air from a compressor
Membrane dryers are a compact solution for drying air using semi-permeable membranes. In design terms they are a cylindrical cartridge (tube) containing a bundle of hundreds of hollow fibres that form the membrane. These fibres let water vapour molecules pass through their walls, while the remaining gaseous components (dry air) do not get through. When moist compressed air enters the membrane dryer, it flows inside the fibres towards the outlet. Driven by the difference in concentration, the water vapour penetrates the micropores of the membranes and escapes into the surrounding space of the dryer. A small part of the dry air is sacrificed as a purge (“regeneration”) stream through that outer space, which carries the removed moisture away through the exhaust port. What leaves the fibres at the outlet is therefore markedly drier air. Membrane dryers can lower the pressure dew point of the air to roughly –20 °C to –40 °C (depending on the purge rate and the membrane length).
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Advantages
- Very compact dimensions and low weight – membrane dryers are cartridge-shaped and fit even into cramped spaces or directly into the air distribution pipework.
- Simple installation and operation: the unit contains no moving parts and no electrical components, and needs no power supply (it uses only the pressure of the air itself).
- Quiet running and instant readiness – no warm-up phase and no cyclic switching as with twin-tower desiccant dryers.
- Long membrane service life when used correctly; suitable for continuous drying of smaller air volumes with no operator intervention.
Disadvantages
- Part of the inlet air is consumed as purge (typically 10–20 % of the flow, and up to around 30 % when aiming for the lowest dew point), which reduces the total usable volume of air delivered.
- Limited flow capacity: higher air volumes would require many membrane modules connected in parallel, which is expensive – for medium and large compressors other dryer types are therefore more economical.
- Lower achievable drying quality compared with top-end desiccant dryers. Membranes usually do not reach extremely low dew points (below –40 °C) as efficiently as an active desiccant.
- Sensitivity to contamination: to prevent damage or clogging of the membrane fibres, high-quality filtration of the inlet air must be ensured (dirt and oil aerosols could damage the membrane irreversibly).
Applications
Membrane air dryers are ideal for smaller applications and for drying right at the place of use (point-of-use), where dry air is required but the flow is not high. They are often used in laboratories, with analytical and medical instruments, with precision pneumatic equipment or in explosive atmospheres (ATEX), where electrical devices are undesirable. Thanks to their compactness they can be installed right next to individual machines or processes – for example at packaging lines, optical instruments, dosing equipment or robotic workstations that need consistently dry air. They also find use in mobile compressor sets and service vehicles, where there is no mains supply to power a refrigeration or desiccant dryer.
Comparison with other dryer types
Compared with other dryers, membrane units are distinctive in their simplicity and in what they are meant for. Against refrigeration dryers they need no electricity at all and reach a lower dew point, yet for larger air volumes refrigeration drying is far more efficient (membranes come into their own where the flow is too small for effective cooling). Against desiccant dryers, membranes offer a lower initial investment and simpler operation at small capacities, but they reach neither such extreme drying nor such large flows. A membrane dryer can be a sound alternative to a small desiccant unit wherever a dew point of around –20 °C to –40 °C is enough and maintenance is to be kept to a minimum. For maximum air purity, a further filtration stage can be placed downstream of the membrane dryer – for example an activated carbon tower to remove any residual oil vapour, much as in other systems.
Remember: membrane dryers need very clean inlet air to work properly. Always install a suitable compressed air filter ahead of the membrane – ideally a combination of a coalescing and a fine dust filter. Only then will you achieve the declared membrane life and a stable dew point. Also allow for the fact that a small amount of air will leave downstream of the membrane dryer into the surroundings as a carrier of moisture.
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RDP condensation dryers; pressure dew point +3 °C
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Condensation dryers WDF; dew point +3°C with filters
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HDI air dryers; pressure dew point +4°C
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RDL condensing dryers; pressure dew point +5°C
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ADRY air dryers; smaller adsorption -40°C
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BDRY air dryers; large adsorption -40°C
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MADRY air dryers; membrane -40°C
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Activated carbon columns; activated carbon separation
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Product sorting
List of products
MADRY-12 membrane dryer with compressed air flow up to 12 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-123 membrane dryer with compressed air flow up to 123 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to...
MADRY-18 membrane dryer with compressed air flow up to 18 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-180 membrane dryer with compressed air flow up to 180 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to...
MADRY-24 membrane dryer with compressed air flow up to 24 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-3 membrane dryer with compressed air flow up to 3 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-32 membrane dryer with compressed air flow up to 32 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-44 membrane dryer with compressed air flow up to 48 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-6 membrane dryer with compressed air flow up to 6 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-63 membrane dryer with compressed air flow up to 63 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-9 membrane dryer with compressed air flow up to 9 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
MADRY-90 membrane dryer with compressed air flow up to 90 m³/hr up to 12 bar. Including 2 filters through the dryer and filter cartridge clogging indication. Designed to supply...
Replacement diaphragm for MADRY-12M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-123M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-3M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-180M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-24M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-44M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-63M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-18M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-32M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-6M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-90M compressed air dryer from compressor working on the principle of water separation by means of hollow fibre diaphragm.
Replacement diaphragm for MADRY-9M compressed air compressor membrane dryer working on the principle of water separation using a hollow fibre membrane.