Compressed air can carry liquid water, oil aerosol, pipe scale, compressor residue, and fine particles into pre-stretch, pressure forming, air eject, and control circuits. Contamination may leave surface marks, obstruct small passages, swell seals, or make valves respond inconsistently.
Samples should be taken at the machine under production flow, not only at the compressor room. Filter differential pressure, drain operation, dryer performance, pipe condition, and point-of-use filtration should be checked. A clean-looking line can still release accumulated condensate when demand changes.
Air treatment must match the sensitivity of the product and pneumatic components. Filters and drains require documented maintenance; excessive filtration pressure drop must also be avoided. Oil should never be introduced into a product-contact air stream unless the machine design explicitly requires and isolates it.