For compressed air to be safely and adequately delivered to pneumatic equipment, it must pass through a filter, a pressure regulator, and in some cases, a lubricator. Often packaged together, these devices are collectively known as FRLs.
Passing the air through a filter prevents dirt, moisture and compressor oil from damaging pneumatic devices. Air enters the filter and passes through louvers that direct it into a swirling pattern. Centrifugal force throws liquid droplets and dirt against the side of the filter bowl. "It's like a tornado inside that bowl," says John Lokken, technical support engineer with the Pneumatics Div. of Bosch Rexroth Corp. (Lexington, KY).