Coalescing filter

Coalescing filters capture submicron liquid aerosols from compressed air. The air flows from inside-out (or outside-in) through a fibrous filter element; small droplets stick to the fibers, merge with neighbors, and run down to a drain at the bottom of the housing. Particulate captured along the way is held mechanically.

What it is

Compressed air leaving a typical industrial compressor carries water aerosols, oil aerosols (from oil-flooded units), and solid particulates from intake and wear. Coalescing filters address the liquid fraction down to fractions of a micron. Filtration grades follow ISO 8573 numbering: general purpose (1.0 micron, 1 ppm), high efficiency (0.01 micron, 0.01 ppm), oil-removal / oil-vapor (activated carbon, sub-ppm hydrocarbons).

Why it matters

Without coalescing filtration, liquid water and oil migrate down the distribution system, fouling tools, damaging instruments, and contaminating product. Pressure dew point and air quality class both depend on adequate filtration upstream of the dryer (to protect the dryer) and downstream (to deliver the spec to the point of use). Coalescer cartridges are consumables and must be on a calendar replacement schedule.

How it is used in our catalog

Coalescing filters are listed in the filtration section, indexed by flow rating, micron rating, and oil carry-over. They pair with every compressor and every dryer in the dryer catalog. Browse installers for filtration-train design services.

Common questions

Inside-out or outside-in flow?

Modern coalescers are inside-out: dirty air enters the inside of the cylindrical element, clean air leaves the outside, and coalesced liquid drains down the outside surface. Outside-in designs are older and less efficient.

How often do cartridges need to change?

Annually for most plant-air duty, or when differential pressure rises above 8-10 psi, whichever comes first. Oil-loaded service may halve that.