Glossary · Pneumatics and hydraulics
Filter-regulator-lubricator unit (FRL)
Also known as: FRL unit, Air preparation unit, Service unit
German: Wartungseinheit (FRL)
In pneumatics, a filter-regulator-lubricator unit (FRL) is an air preparation assembly at the machine inlet that filters compressed air, sets it to the working pressure and, where required, adds oil mist; modern units often combine it with a shut-off valve and soft-start valve.
- Fluid power
In one sentence
An FRL unit prepares compressed air at the machine: it filters it, sets the pressure and, if needed, adds lubricating oil.
Example
The machine's FRL unit has a lockable shut-off valve, a filter with automatic drain, a regulator set to 6 bar and a soft-start valve.
How it applies
- Engineering: Many modern components are designed for unlubricated air; once air is oiled, it usually must stay oiled. Shut-off and exhaust valves in the FRL line support energy isolation.
- Commissioning: Pressure is set to the value in the technical data; soft-start valves prevent abrupt movements when air is switched on.
- Maintenance: Filter elements, drains and oil levels are checked at defined intervals.
- Documentation: Show the FRL unit in the pneumatic diagram and in the manual with its controls. Describe the lockable shut-off valve as part of the Lockout/tagout (LOTO) procedure and explain that it vents the system downstream; residual pressure in parts held by check valves must be addressed separately.
FRL vs. pressure regulator
A Pressure regulator is one part of the FRL unit. The FRL adds filtration and, where used, lubrication.