Plant-supplied compressed air often travels along and varying paths from the air compressor to where it is connected to a machine or piece of equipment.

Along this path, there are many opportunities for contamination via dirt, dust, oil, water, and other impurities. Therefore, compressed air must be filtered at the supply point, and it must also be safely controlled, filtered, regulated, and sometimes lubricated—all in the proper order—at the machine level.

A steady flow of clean and dry air is a common requirement to operate and protect pneumatic components in machines, processes, and equipment. Any pneumatic-actuated motion—such as clamping, gripping, lifting, positioning, and pushing—requires clean and dry air supplied at sufficient flow and pressure. To supply this clean and dry air, and air prep unit provides filtering, regulating, and sometimes lubricating (FRL) of the compressed air.