How to Connect FRL Units to Pneumatic Actuators

What an FRL Unit Does – The Three Functions

Some applications omit the lubricator (e.g., for instruments or clean service). Others add a shut-off valve and soft-start valve for additional control.

Connection Sequence – Correct Order Matters

The standard flow direction through an FRL is fixed:

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Compressed Air Supply → Filter → Regulator → Lubricator → Actuator

Why this order?

Critical: Never install the lubricator before the regulator. Oil in the regulator will cause drift, inaccurate output, and eventual failure.

Connection Methods – Piping Options

1. Direct Mount (Integral)

The FRL components are assembled as a single modular unit—typically with threaded ports on each side.

• Advantages: Compact; minimal leak points; factory-assembled alignment

• Typical connection: Female threads (BSPP, NPT, or G) on inlet and outlet

• Recommended for: Panel-mounted or space-constrained installations

2. Bracket Mount with Tubing

Components mounted separately on a bracket, connected with tubing or hose.

• Advantages: Flexible layout; easier component replacement; accommodates larger flow rates

• Typical connection: Push-to-connect fittings with nylon or polyurethane tubing

• Recommended for: Distributed systems or retrofits

3. Manifold Mount (Multiple Stations)

One FRL supplies multiple actuators via a common manifold.

• Advantages: Centralized conditioning; reduced hardware; consistent pressure to all stations

• Typical connection: Ported manifold block with individual outlet shut-offs

• Recommended for: Valve islands or cluster installations

Port Sizing – Matching Flow Capacity

The FRL ports must match or exceed the actuator's air consumption.

Rule of thumb: FRL port size should never be smaller than the actuator port. Undersizing causes pressure drop—especially during high-cycling operations.

Pressure Setting – Adjusting the Regulator

The regulator sets the operating pressure for the actuator—not the supply pressure.

Steps:

1. Fully close the regulator (turn counter-clockwise until no resistance)

2. Open the supply shut-off valve

3. Slowly turn regulator clockwise until the gauge reads the actuator's rated pressure

4. Cycle the actuator several times—observe pressure drop during stroke

5. Re-adjust to maintain rated pressure at the peak flow condition

Important: The actuator nameplate pressure is the maximum. Set to the minimum pressure required to move the load reliably—this reduces seal wear and air consumption.

Lubricator Adjustment – Getting the Oil Feed Right

Over-lubrication is as damaging as under-lubrication.

Typical setting method:

• Adjust the drip rate to 1–2 drops per 10–15 cycles for intermittent service

• For continuous cycling, set to 1 drop per 100–150 strokes

• Use the correct viscosity oil—typically ISO VG 32 or 46

Signs of incorrect lubrication:

Note: Some actuators have self-lubricating seals and do not require a lubricator. Check the manufacturer's recommendation before installing.

Mounting Orientation – Gravity Matters

FRL units must be mounted correctly for proper operation.

Always mount with the bowls pointing vertically downward.

Drain Management – Don't Forget the Filter Bowl

Filters collect water and debris. If not drained, contaminants re-entrain into the air stream.

Drain types:

Recommendation: For outdoor or inaccessible locations, always specify an automatic drain.

Connection Checklist – Before You Turn On Air

Common Connection Mistakes – And How to Avoid

When to Bypass the FRL – Special Cases

Some applications do not require a full FRL:

Maintenance After Connection – First 100 Hours

After initial connection and commissioning:

• Check filter bowl for water accumulation—drain if needed

• Re-tighten fittings—vibration can loosen connections

• Verify regulator set point under full flow conditions

• Check lubricator drip rate—adjust if too high or low

• Inspect for leaks at all threaded joints using soapy water

Document these baseline values for future reference.

Summary – Clean Air Is Cheap; Dirty Air Is Expensive

Connecting an FRL unit correctly is a small task with outsized consequences. One wrong sequence, undersized port, or forgotten drain can lead to:

• Sticking actuator spools—erratic valve response

• Worn seals—air leakage and reduced torque

• Corroded internals—complete actuator replacement

• Process upset from valve drift—production loss

Follow the sequence. Match the sizing. Mount with bowls down. Maintain the drain.

Do this, and your pneumatic actuator will deliver its rated performance and service life.

Quick Reference Card – FRL Connection

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