Air service unit: complete guide for pneumatic systems

◆ VPC Official Spanish Language Website

Does your pneumatic equipment often have problems such as slow air cylinder movement, stuck solenoid valves, and worn seals?

These problems are mainly caused by moisture, impurities, and unstable pressure in the compressed air.

The air service unit effectively removes pollutants in the air, stabilizes system pressure, extends equipment life, and reduces maintenance costs through triple processing of filtration, pressure regulation, and lubrication.

1. What is an air service unit?

An air service unit, also known as an FRL unit, is an integrated module made up of an air filter, pressure regulator, and lubricator. 

Its main function is to clean, regulate, and lubricate compressed air before it reaches pneumatic components like solenoid valves and pneumatic cylinders, ensuring a reliable air supply that meets equipment requirements.

2. What does the air service unit consist of?

① Air Filter

• Function

Removes solid particles (dust, debris) and liquid contaminants (water, oil mist) from compressed air.

• Features
  

Filter element: Captures contaminants and debris.

Filter bowl: Separates and collects moisture to keep it out of the system.

Manual or automatic drain: Removes built-up water and particles from the filter housing.

• Why it matter?

Dirty air can damage sensitive pneumatic components, cause blockages, and reduce system efficiency.

② Pressure Regulator

• Function

Receives high-pressure, unstable air from the compressor and reduces it to a constant, precise working pressure, ensuring the pneumatic system operates at the required pressure.

• Features

Adjustment knob: Allows the operator to set the desired pressure.

Pressure gauge: Displays the current system pressure for monitoring.

Relief valve: Releases excess pressure to protect downstream components.

• Why it matter?

Consistent performance: Ensures cylinders deliver the same force every time.

Energy saving: Too much pressure wastes energy. Setting pressure just right reduces operating costs.

Safety: Prevents damage to system components or risks to operators from overpressure.

③ Lubricator

• Function

The lubricator atomizes special lubricating oil into tiny droplets that mix evenly with the airflow, providing continuous lubrication to pneumatic components like pneumatic cylinders and solenoid valves.

• Features

Oil reservoir: Stores the lubricating oil.

Adjustment mechanism: Controls the amount of oil entering the system.

Atomizing device: Converts oil into a fine mist and mixes it with air.

• Why it matter?

Reduces friction and wear, extending equipment life and improving efficiency.

3. What does an air service unit do?

Air service unit is a pneumatic component used to improve air quality and protect pneumatic equipment.

① Purify compressed air: remove moisture, dust, and rust particles to keep the air clean.

② Stabilize air pressure: measure and regulate pressure to prevent damage from overpressure.

③ Reduce wear: lubrication minimizes wear caused by oxidation and friction.

④ Extend service life: increases the lifespan of pneumatic components by 40–60%.

⑤ Lower maintenance costs: reduces maintenance expenses by 35%.

⑥ Improve energy efficiency: boosts system efficiency by 15–25%.

⑦ Enhance system reliability: increases overall reliability by up to 80%.

4. How to select air service unit (Frl unit)?

Determine port size*1	Confirm the thread size of the FRL inlet/outlet port. Common sizes: M5, G1/8", G1/4", G3/8", G1/2", G3/4", G1".
Calculate required flow rate	Ensure the FRL rated flow ≥ the system's maximum required flow to prevent pressure loss due to insufficient flow.
Specify pressure range	The adjustable range of the regulator should cover the working pressure required by the equipment.
Filtration accuracy	5 - 50μm	Suitable for protecting pneumatic motors, large cylinders,  and pneumatic tools in applications with low requirements.
	1 - 5μm	Standard choice, suitable for protecting solenoid valves, booster regulators,  precision cylinders, and most general applications.
	0.01 - 1μm	Used in industries with high cleanliness requirements, such as  semiconductor manufacturing, food, and pharmaceuticals.
Drain type*2	Automatic drain type / Manual drain type
Combination type	FRL	Only used to clearly indicate equipment that requires external lubrication.
	FR	Basic type. Suitable for all self-lubricating components.

*1) The port size should not be smaller than the main pipeline size to avoid extra flow resistance.

*2) If maintenance staff cannot check frequently or the FRL unit is installed in a hard-to-see location, the automatic drain type is recommended.

5. Air service unit installation and maintenance

① Installation

• Direction: Install according to the airflow direction arrow on the unit (usually in the order F → R → L). The filter is always first.

• Position: Install as close as possible to the air-using equipment and ensure the pressure gauge, drain cup, and oiler are easy to access.

• Support: For larger units, use brackets to fix in place and avoid excessive load on the piping.

② Maintenance

• Filter element replacement: Replace every 2 years or when pressure drop exceeds 0.1 MPa (1 Bar).

• Regular draining: Check and drain the water trap daily or weekly.

• Pressure adjustment: Regularly check and adjust the regulator to maintain consistent output pressure.

• Oiler oil level: Ensure the oil reservoir is filled with the correct type and amount of oil to avoid dry running.

Air service units provide clean, stable, and lubricated compressed air through FRL components (filters, regulators, and lubricators) to ensure efficient operation of the system. They are widely used in manufacturing, automotive, food and beverage, pharmaceutical, and textile industries, and are an important guarantee for industrial automation.

We offer a variety of high-performance FRL units. If you have any questions about selection or matching, please contact VPC Pneumatic!

FAQ

1. What do you mean by FRL unit?

FRL unit is the abbreviation for air preparation units, consisting of three core components: Filter, Regulator, and Lubricator.

2. Does a pneumatic system need lubrication?

Use an "L" (Lubricator) only if your equipment manual specifically requires external lubrication. If your downstream equipment is self-lubricating, you should choose the FR combination (Filter + Regulator) without the Lubricator. We offer both combinations for your convenience.

3. Why can't my pressure regulator hold pressure?

• Check the lock mechanism: Make sure the adjustment knob is in the "unlocked" position (usually by pulling up or turning).

• Check the inlet pressure: Ensure the upstream pressure going into the FRL is high enough. Regulators can only reduce pressure, not increase it. Your set pressure must be lower than the supply pressure.

• Check for flow overload: If the downstream air consumption is too high and exceeds the FRL's rated flow, the pressure may drop quickly when the equipment starts. Try shutting off some downstream devices to see if pressure stabilizes.

• Internal failure: If all the above is fine, the issue may be a damaged diaphragm, broken spring, or blockage from debris. In this case, contact your supplier for a repair kit or replace the regulator.

4. How often should I change the filter element?

This depends on your air quality and frequency of use. Generally, it is recommended to change it every 6 to 12 months, or when you notice a significant pressure drop on the pressure gauge when the unit is not in use.

5. What oil should be put in the air service unit?

You should use lubricants designed specifically for pneumatic systems (usually ISO VG32 or similar viscosity). Do not use ordinary motor oil or hydraulic oil.