Process, Controls & Plant Focus on: Compressed Air 18 | Plant & Works Engineering www.pwemag.co.uk October/November 2026 Housings and filter elements may not be the most visible part of a filtration system, but they are essential in managing compressed air and gas purity. The housing is the pressurised outer shell that directs the airflow and holds the internal components. Key features of housings include: The head - usually contains the inlet and outlet ports where the air enters and exits the filter. The bowl - the bottom part that collects the liquid (water and oil) captured by the filtration process. The drain - found at the bottom of the bowl. There are usually four types of condensate drains used on compressed air filters: 1) electronically level-controlled drain, 2) electrically time-controlled drain, 3) float drain, 4) manual valve. The electronically levelcontrolled drain does not release any compressed air from the filter, only the condensate. A filter element is the replaceable insert that sits inside the housing, trapping or separating contaminants. Elements are categorised based on what they are designed to capture, and include: Particulate elements - use a mesh or fibre media to catch solid dust, dirt and pipe scale. Coalescing elements - force small oil and water droplets to merge into larger drops, which then fall into the bowl. Adsorption (carbon) elements - use activated carbon to capture oil vapours and odours that coalescing filters miss. Well-configured filter housings and the right element therefore help capture contaminants such as particles, moisture, oil aerosols and oil vapour – The unsung filtration heroes of reliable compressed air Pure, reliable compressed air and gases help to keep industrial operations running smoothly. In compressed air and gas systems, including hybrid applications like air-driven hydraulic pumps and air-over-oil systems that rely on clean plant air to generate hydraulic force, filtration is an active part of process reliability. Wolfgang Bongartz, Global Product Manager Industrial Gases at Donaldson, explains further.
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