What is a filter regulator lubricator FRL

What is a Filter Regulator Lubricator (FRL)?


An FRL consists of three elements - a filter (F) to, generally, remove particles above 40 micron in size and water, a regulator (R), which controls pressure and a lubricator (L), to provide a controlled quantity of oil into the system.

They are also known as…

We often call the assembly a "box set". A box set can also include a shut-off valve and gauge. The box set helps reduce installation times and labour costs and can be a lower cost option compared to the individual parts.

How does a Filter Regulator Lubricator (FRL) work?

Here, we must consider the basic working principles of the individual elements of the FRL:

  • Filter: The filter body has a construction that creates a cyclonic action for the incoming air. This action works to deposit water and heavier particles to the bottom of the bowl. A baffle, under the filter element, prevents the deposited water and debris being sucked back into the output air flow. Air is then forced through a filter element, the mesh size determining the minimum size of particle removed from the air flow. So, for example, a 40 micron filter will remove all particles greater than 40 micron in size. 5 micron elements are also available, as are oil and vapour removal filters.
  • Regulator: The control knob works against a spring which, in turn, places load against a diaphragm assembly. The diaphragm pushes down on a valve pin connected to the valve seat and the seat drops; this allows downstream air flow from the inlet port (P1) out of the outlet port (P2). As air passes down P2, a breathe hole lets air into a chamber below the diaphragm; once pressure either side of the seat is equal, the seat closes with the aid of the spring. Downstream demand will cause a pressure drop in the chamber, opening the seat and allowing air to flow again until pressure is once more equalised and the seat closes. The process is continuous, maintaining P2 at a set value.
  • Lubricator: A lubricator is designed to introduce a controlled quantity of oil into the downstream air flow. IMI Norgren offer two types. The standard oil-fog lubricator passes all droplets created into the air flow. The micro-fog lubricator atomizes the droplets before they enter the air flow; the typical particle size is <2 micron and only around 10% of the particles seen in the site dome are passed downstream.
How do I select a Filter Regulator Lubricator (FRL)?

There are a number of considerations in choosing an FRL combination.

  • What is the flow rate required for a process or system? This will determine the port size of the FRL.
  • What level of filtration is required and to what level of dryness? The general purpose filter is 40 micron, but 5 micron is also available. As a rule, air would be filtered to 40 micron first, before applying the 5 micron filtration. A 40 micron filter will typically remove 95% of the water content; putting the filters in series means 95% of the remaining 5% will be removed, giving water removal approaching 99%. After 5 micron removal, oil, then vapour removal filters can be applied.
  • What is the pressure requirement to operate downstream equipment and what is the supply pressure? This will be the task of the pressure regulator. It is important to note that a quantifiable pressure drop will occur through the FRL combination.
  • What degree of lubrication is required? Oil fog lubricators are ideal for heavy requirements over short distances and level runs; micro-fog lubricators are best suited to complex systems, with multiple components, over long and often non-level runs.
Typical applications of a Filter Regulator Lubricator (FRL)

Simply put, you are likely to find an FRL combination in any compressed air system. They can be found in the main supply line and in branch lines supplying specific components that may require, for example, different pressure supply, higher grade filtration, etc.

Do I need anything else to make a Filter Regulator Lubricator (FRL) work?

FRL's need connection into the system, so fittings and tubing are a necessity.


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