Basics of Coalescing Filtration

coalescing filter is used to remove water and oil aerosols from compressed air.

These contaminates are usually compressor lube oils, residual cutting oils and pipe dope from the pipe joints, condensed moisture, carbonized oils and solutions of dissimilar oils.

Coalescing filters should always flow from the inside of the filter element to the outside of the filter element. This allows for the oil and water droplets to collect on the fibers of the filter element and meet at crossover points and become larger and larger droplets (the process of coalescing) as they travel downward and outward to the base of the filter element. The large droplets drop off the base of the filter element into the sump area of the filter housing and ultimately into an automatic float drain where the liquids are drained out of the system.

A coalescing filter by nature will also remove all solid contaminates from the compressed air system as well as liquids. It is the solid contaminates such as rust particles, dust, solder particles, welding flash etc. That will determine the useful life of the filter element as these particles are permanently trapped in the filter element blocking off the filter media and creating a restriction of flow and an increasing differential pressure drop in the compressed air system.