Filter-Regulator-Lubricators (FRLs) are available in several different configurations:

• - individual components
• - combination filter-regulator ("piggyback"shown below)
• - two-unit modular combinations
• - three-unit modular combinations

Filter, regulator, lubricator (FRL) assemblies are pre-packaged or modular assemblies of common configurations of air filters, regulators, lubricators, and gauges.  Important specifications to consider when searching for filter, regulator, and lubricator assemblies include regulator type, media, performance specifications, adjustment control, connectors or pipe size, body material, features, and environmental parameters.

The piggyback (fig. FRL1-1) and modular FRL's (fig. FRL1-2) have space-saving designs. The piggyback has a filter and a regulator stacked on top of each other. Modular design allows for easy installation and removal of components.

The filter itself may be for depth filtration, edge filtration, or coalescing. Regulators may be of the piston or diaphragm design. FRLs are used in compressed air systems in various industries for numerous applications.

• - Medical: dental equipment, oxygen concentrators/enrichers, respirators, hospital air systems, hospital lab air systems, drug manufacturing and packaging
• - Electronics: console controls, testing equipment, circuit board manufacturing, silicon water handling/manufacturing, assembly computers
• - Packaging: filling equipment, sealers, boxers, coders, wrapping, palletizers, can and bottle manufacturing, labelers, cleaners, glue dispensing
• - Textiles: industrial sewing machines, industrial laundry equipment, dry cleaning equipment, looms
• - Printing: presses, ink flow regulators, photocopier equipment, carton loaders, stencil transfer machines, engraving machines
• - Food: beverage dispensing equipment, produce sorting, meat processing, canning/bottling
• - Automotive: tire changing equipment, lifts, pneumatic tools, paint spraying, sand blasting
• - General manufacturing: actuators, pneumatic tools, air hoists, automation equipment, instrumentation

FRL Filters: Filters (fig. FRL1-3) eliminate pipe scale, dirt, rust, and moisture from compressed air lines. Proper filtration is critical to maximize the dependability and longevity of a compressed air system. Do not install a filter with a finer rating than necessary. Although it will not hurt downstream equipment, it will drive up the system operating cost.

Particle-removal filters should be chosen based on the following factors:

• - scfm
• - acceptable pressure drop
• - pipe connection size

A filter with bigger body size will create less initial pressure loss and provide longer operating life than a smaller filter with the same removal ratings.

Coalescing filter elements are available based on micron size.

Choose a coalescing filter and element based on the following factors:

• - acceptable oil carryover
• - expected airflow rate
• - pipe connection size

Absorption-type filters, used in food processing or breathing air, normally contain activated carbon granules, which absorb and hold hydrocarbon vapors.

Install an appropriate number of drains valves upstream of the filter. These drain valves will assist in the removal of excess condensate and contaminants, as well as provide additional protection for the filters.

Filter bowls will collect condensate and require drain valves. The majority of filter bowls are made from polycarbonate or metal.

CAUTION:
Polycarbonate bowls are suitable for use in normal industrial environments, but should not be located in areas where they could be subjected to direct sunlight, an impact blow, nor temperatures outside of the rated range. Polycarbonate bowls should not be exposed to chlorinated hydrocarbons, ketones, esters and certain alcohols. They should not be used in air systems where compressors are lubricated with fluids such as phosphate ester and di-ester types.

Metal bowls are good to use where ambient and/or media conditions are not compatible with polycarbonate bowls. Metal bowls can resist the effects of most solvents, but should not be subjected to salt laden atmospheres or used where strong acids or bases are present. Metal bowl guards are recommended for all applications, and can even protect a polycarbonate bowl from damage.

FRL Regulators: Regulators (fig. FRL1-4) govern line pressure changes and deliver a constant outlet pressure to the downstream air components. There are relieving and non-relieving types of regulators. Relieving regulators let air escape should the downstream pressure surpass the desired regulated pressure. In this event the excess pressure will cause the diaphragm to move upward against the control spring, open the vent hole, and vent the excess pressure to the atmosphere through the hole in the bonnet. One type of regulator uses a balanced-poppet-style valve. As downstream pressure increases, it pushes on the bottom side of the diaphragm, balancing against the force of the spring. The poppet throttles the orifice to restrict flow and produce the desired downstream pressure. A spring under the poppet ensures that the valve closes all the way when there is no flow present. (Because the poppet is pressure-balanced to maintain good stability, the effects of output pressure fluctuations cancel out, which upgrades sensitivity and response and lessens droop, or loss of pressure.)

Larger capacity regulators include their own separate diaphragm chamber, which has an aspirator tube exposed to the output pressure. As the flow increases through this regulator, the aspirator tube provides a slightly lower pressure in the diaphragm chamber. The diaphragm is pushed downward and opens the orifice without reducing the output pressure. Therefore, this kind of regulator has minimal droop (output pressure decay) as supply pressure varies.

Lubricators: Lubricators (fig. FRL1-5) provide a constant oil-air mixture to lubricate downstream air equipment for reduced friction and wear. High-velocity air passes through a venturi, and draws the oil through a capillary, then drips it into the air-stream. The moving air breaks up the oil into a mist or fog, which is then transferred downstream into the air-powered machine. There are also micro-mist lubricators, which lubricate through tiny holes, creating a fine mist. They are usually chosen based on pipe connection size, oil reservoir capacity, and acceptable pressure loss versus flow rate. Inside the lubricator are bowls to collect accumulated liquid condensate. These bowls are made from either polycarbonate or metal.

CAUTION:
Polycarbonate bowls are suitable for use in normal industrial environments, but should not be located in areas where they could be subjected to direct sunlight, an impact blow, nor temperatures outside of the rated range. Polycarbonate bowls should not be exposed to chlorinated hydrocarbons, ketones, esters and certain alcohols. They should not be used in air systems where compressors are lubricated with fluids such as phosphate ester and di-ester types.

Metal bowls are good to use where ambient and/or media conditions are not compatible with polycarbonate bowls. Metal bowls can resist the effects of most solvents, but should not be subjected to salt laden atmospheres or used where strong acids or bases are present. Metal bowl guards are recommended for all applications, and can even protect a polycarbonate bowl from damage.

FRL Installation and Maintenance Requirements

• If the filter's purpose is to remove moisture, an automatic float-type drain should be installed to periodically remove condensate from the filter bowl. These bowls are normally transparent, allowing for easy visual inspection of the sump level. If a filter could be subjected to conditions where pressure is above 150 psig (10.3 bar), temperatures are below 40°F (4.44°C), or temperatures are above 120°F (48.89°C); a metal bowl rather than the polycarbonate bowl is required. This also holds true when synthetic compressor lubricants are present, as these often contain chemicals that are harmful to polycarbonate.

• Always install a filter upstream from a regulator to protect its internal passages. It is crucial to set the regulator's desired output pressure under normal flow conditions.

• In a lubricator, a manual adjusting valve sets the oil drip-rate, and a sight glass allows the operator to monitor the output. A fill plug provides access to refill the reservoir.

• In combination units, interconnections are often made through modular face connectors. These connectors allow simple removal of components for servicing or cleaning.