FRL

FRL 's are devices used in preparing compressed air for use in your plant air system or for air tools.

There is no shortage of information on this site about the water problems air compressors create while compressing air. See the section under Water on the site map page.The FRL is designed to reduce or eliminate some of these water problems.

FRL Acronym

The term FRL is an acronym for the three typical parts of the air compressor preliminary compressed air treatment; the Filter, the Regulator and the Lubricator.

In Order

If you are using a complete FRL assembly to prepare your compressed air, do make sure that the order in which the individual components are installed are as shown; filter first, then the regulator, and then the lubricator if one is needed.

The compressed air filter is installed first to remove particulates and free water before the dirty wet air gets to the regulator.

The regulator is next. Compressed air that will flow through the regulator has been filtered, then that same compressed air is pressure regulated before it flows to the lubricator, if one is required for the compressed air using tool, air motor, or air cylinder.

The conditioned and pressure-regulated compressed air will then flow through the lubricator and pick up the necessary lubricant for the tool or actuator.

You do not want to put the lubricator first, as all the liquid oil coming out of it would then be stripped from the air by the filter. The regulator wants to control clean air, so you would not install it first. Just remember FRL is the name of the air preparation set of equipment, and the order in which they are installed.

The picture shows a somewhat typical FRL. To the left is the filter, the regulator is in the middle, and the lubricator is to the right.

The filter will typically have a female NPT port for the air to flow in from the left and the lubricator will have the same female port for the air to flow out of into the air line, from the unit on the right.

Note The Arrows

Note the arrow on the filter and lubricator caps. The arrow shows the route for the air flow. None of the components in the FRL will work properly if the air flows against the flow design.

This filter has an automatic float type drain inside the bowl, though this is not visible from the picture. I know as I disassembled this particular unit after I took the photo.

There is a sight glass on both the filter and lubricator. The purpose is to show the liquid level inside the metal bowl on both the filter and lubricator, as the metal is opaque and cannot be seen through to detect the water level inside the bowl.

If the compressed air filter was a manual drain type, something I never recommend, the sight glass will indicate the level of fluid inside the bowl for the maintenance operator to help ensure that the filter bowl gets drained regularly. I do not recommend a manual drain on filters as they quite often get forgotten, the bowl overfills, and now, instead of pulling free water out of the air stream, the filter becomes a source of water to downstream air components.

Lubricator

The lubricator has a sight glass on the bowl as well, and this allows the maintenance operator to monitor the level of lubricant in the bowl, without having to remove it.

On top of the lubricator is another sight glass and an adjusting screw with which the maintenance operator can ensure that the lubricant is dripping into the air stream, and to see the results of flow adjustment by the turning of the adjustment screw.

When it comes to using a lubricator, less is more! Do not become one of the many who think that more lubricant is better than a little.

While lubricant rates are predicated on the device and the cycle time, a drop every 2-3 minutes should be adequate for all but most trying applications.

Regulator Orientation

The regulator can be installed in this modular type FRL as it shows in the picture, or it can be inverted so that the adjusting knob is at the top. The preference depends on the application.

The adjustment knob can also be ordered as a locking unit, to help prevent unauthorized pressure adjustment of the air circuit.

Precision regulators, offering tighter pressure setting accuracy and setting tolerance, are an available option if the application requires it. Regulator manufactures commonly offer general purpose and precision regulators.

Regulators are available with a variety of pressure ranges to suit any application.

Gauge

The pressure gauge shown in the photo above is of a general purpose design. They are cheap to build, yet reasonably effective in displaying the pressure of the regulator setting.

Other options for gauges include liquid filled, stainless steel, a variety of pressure read-out-ranges, gauge face size, among other options.