Pneumatic Filters

Designed to take particulates and moisture out of air distribution lines, pneumatic filters are the first line of defense in protecting pneumatic tools, regulators and other downstream air consumers from water, rust, debris, and other macroscopic and microscopic agents of destruction.  They fall into two major groups, “particulate” and “coalescing” where the former removes water and entrained particulates and the latter removes microscopic impurities including oil aerosols.  Particulate filters consist of a body with inlet and outlet connections, a bowl with a baffle, a filter element, and a bowl drain.  Air enters from the inlet through a deflector which forces the air into a cyclone around the bowl, throwing the heavier water molecules against and down the outside wall.  The baffle creates a “quite zone” where the water collects prior to being expelled through the drain.  Above the baffle, the air leaves through the sintered filter element rated at 5, 20 or 40 microns (millionth of a meter) which traps anything larger than its rating.  Sizes range from 1/8” to 2.5” NPT pipe.
A coalescing filter operates in reverse.  Pre-filtered (with a particulate filter above) air enters inside the element and travels through multiple layers of filter media of differing materials and traps very small contaminants and liquids in its fibers.  As liquids get forced to the outside of the element by pressure differential, they “coalesce” or form together and drop into the bowl by gravity.  These filters can remove particles down to 0.01 micron but obviously restrict airflow significantly.