Figure 1 — A modular air preparation unit (FRL): filter, regulator, and lubricator stages in F→R→L sequence, with transparent bowls and an integrated regulator gauge. How an FRL Unit Works: Filter, Regulator and Lubricator Principles for Pneumatic Systems If you walk into a well-run pneumatic line, the first thing you find upstream of every valve … Continue reading How an FRL Unit Works: Filter, Regulator and Lubricator Principles for Pneumatic Systems