:: Air Compressor Parts ::

FRL is an acronym for Filter, Regulator and Lubricator, devices used to “condition” the compressed air from a compressor before it gets to your application be that through an air valve to air cylinders, powering air tools and so on.

When called in to troubleshoot a complaint from a client that their compressed air filter, regulator or lubricator wasn’t working, the first response is to ask the symptoms. Common complaints are, “the regulator is not working, and it’s leaking oil”, or “my air filter fills up too quickly”. Have you ever had these problems?

The acronym FRL is placed in this order deliberately.

These air treatment units, whether they are an assembly (combination FR + L) or a number of single components - Filter + Regulator + Lubricator - installed in a row, must always be installed with the Filter first, the Regulator next, and the lubricator last.

The filter must ’see’ the air coming from the compressed air supply line first, as it’s the defense against compressed air-borne water and particulates. If you think about it, you would want the filter to remove contaminants and free water from the compressed air before that air gets to more sensitive down-stream components, including the regulator and the lubricator.

The regulator is installed after the filter to ensure that the air getting to the regulator is as clean as that type of compressed air filter will allow, thus increasing the life span and mean-time-between-failures for the regulator.

The regulator’s purpose is to regulate a lower pressure to the downstream application. Some folks are of the opinion that the regulator can be used to “dial-up” the pressure. This is true, as long as it’s understood that the pressure that’s being selected is at a level below the upstream supply pressure. You cannot use a regulator to increase the pressure downstream higher than the supply pressure upstream of that regulator.

Compressors are usually cyclic, meaning that the air pressure in the lines from them varies according to where the pressure is in the compressor receiver. When the air pressure in the compressor receiver falls to the low level set point, the compressor will kick in, and bring the pressure in the receiver up to the high level set point, at which point the compressor will stop. This cycle repeats, sometimes quite quickly, depending on the compressed air demand in the shop. A regulator will dampen the pressure swings from the system as the compressor kicks on and off, ensuring that your application, if the regulator pressure is set at the correct level, will see a constant, steady pressure.

If the regulator is incorrectly installed, upstream from the filter instead of after it, not only is the regulator not protected from air-borne water and particulates, it will negatively affect the flow of air to the filter, decreasing its effectiveness.

The lubricator’s purpose is to provide a steady, metered stream of the appropriate lubricant to the downstream application, be that an air tool, or an air valve / cylinder combination.

The lubricator is installed last in the FRL series to ensure that the lubricant has ready access to the components desired to be lubricated though many modern pneumatic circuits may not need a lubricator at all, what with the high cycle type lubricants that are commonly used by air actuator manufacturer’s.

If the lubricator is incorrectly installed after the filter and before the regulator, the lubricant flow will negatively affect the operation of the regulator. The regulator may be over lubricated to the point where it doesn’t work properly. This may be the cause of the “lubricator’s all gummed up and not working properly” complaint. Most compressed air regulators are relieving type, and if the lubricator is “feeding” lubricant to the regulator, lubricant will wick from the relieving port, hence the “regulator’s leaking oil” complaint.

If the lubricator is installed upstream from the filter and the regulator, the lubricant stream from the lubricator will simply be intercepted by the filter, and not get downstream to the application at all. Thus the filter is “filling up too quickly” complaint.

In the absence of the lubricator, the correct installation if filter first, then regulator.

If the unit you have is a combined filter regulator, it’s internally plumbed to have the air filtered through the filter ‘half’ before the compressed air gets to the regulator.

Remember, it’s FRL on purpose!

Bill Wade is a former sales representative, sales manager, marketing manager and president of companies that use and sell compressed air, along with other equipment and supplies. His sales agency currently represents a select group of companies. Mr. Wade writes about understanding compressed air, how it’s compressed, how it’s treated, and how it’s used at http://www.about-air-compressors.com.

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If you are one of the many folks that have purchased or are considering purchasing a home compressor, you do want to have a bit of information about compressed air filters.

Compressing air generates a reservoir (receiver / air tank) full of wet, dirty, hot compressed air.

As the air leaves the tank, it carries the crud and free water along with it. It also carries a great deal of water vapour. As the compressed air travels to your appliance (air drill / air grinder / blow gun / air brush - what have you?) the compressed air in the air line cools, and some of the water vapour will condense into free water.

That’s why just having a small compressed air filter at the discharge of the compressor tank may not be enough. Even though the unit at the compressor will take much of the debris and free water from the air there, it can’t remove the vapour. Even though you think your air is being filtered, by the time the air gets to your application, water may flowing out of the exhaust ports and onto your work piece, along with the used compressed air.

Of course, if water flowing or blowing onto your work bothers you just a tad :~} , you’ll want to add another compressed air filter just before you use the air.

Many standard compressed air filters have 5 micron filter elements. If you want to know how big that is, check out the details in the Filter page on my web site.

You can purchase compressed air filters with much finer elements, and you can purchase elements that are coarser, allowing much larger particulates through. Much larger is a relative term. We’re still dealing with pretty small bits here.

If you decide that your application needs extensive air filtration, get a micro-filter element for the additional air filter you will need. The new one might filter particulates down to .005 micron, and if you don’t have a 5 micron unit upstream from it to take out the larger bits, the finer element will plug up really quickly, which is why you’ll need the additional filter housing.

You can purchase compressed air filter elements that will strip oil from the compressed air, these known as coalescent filters. Some piston / reciprocating, and other types of compressors too, let oil “blow by” the piston seals into the compressed air tank, and this oil will get blown downstream as you use compressed air. Compressor oil is not good for most tools that have Buna-N type seals. The compressor lubricating oil might ‘eat’ the seals.

Each compressed air filter you install has a negative affect on the available air pressure at your tool. Pressure drop is a reality in compressed air plumbing. You could supply compressed air at 100 PSI into the discharge air line from your tank, and by the time it gets to your tool, all you have available might be 85 PSI. The flow of compressed air through the air lines, the elbows, the ‘T’s and yes, the air filters, all create pressure drop.

If you are using your compressor a lot (make sure you know it’s duty cycle so that you don’t burn it out) then it would be beneficial to have an auto-drain of some sort on the air filter. A float type will open up and let water and crud flow out when the water in the bowl gets to a certain level. An electric auto-drain will be plugged into a 120 Volt outlet, and will open the bowl drain at preset intervals for a preset length of time. You set the electric auto-drain to the interval necessary to keep the filter bowl fairly empty.

If the water and debris in the filter bowl gets above a certain level in the bowl of the filter, it floods the element, and now your compressed air supply is pumping water and debris through the element downstream to your tool.

Did you know that water rusts metal air tool innards, and that water droplets on your work piece will not allow the beautiful paint job you are air brushing on to it to adhere? Of course you did! That’s why you need a compressed air filter.

One more thing. If your air consumption is great enough then even a filter at your tool may not stop the water vapour streaming along with your compressed air from condensing onto your work piece or in your air tool as the air cools. If that is a problem for you, you will need an air line dryer.

Drop me a email from my site if you have any questions. I’ll be happy to respond.

Bill Wade’s experience in compressed air and other industries spans decades; from field sales positions through to the corporate presidential office. His sales agency represents a select group of industrial firms. Mr. Wade writes about all facets of compressed air at http://www.about-air-compressors.com.

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Have you considered your air compressor as a potential bomb?

If you have not, then you better!

Although air compressors are built to withstand high pressures,
and will have all the necessary relief valves to take care of
normal occurring overpressures, explosion involving fire
propagation is another matter.

How can a fire occur in an air compressor?

In order to understand the phenomenon of explosion, we
have to understand the nature of fire, because, after all, an
explosion is a very rapid propagation of fire.

A fire will only start whenever three conditions are met - fuel,
oxygen and heat.

An air compressor when operating will have a very rich supply of
oxygen already in place - pressurized oxygen.

Where do we get the fuel?

If you use oil lubricated air compressors, the lubricating oil
can become the source of fuel. It can also be in the form of
carbon dust. Carbon is formed when oil is heated to high
temperatures.

How is it possible to have high temperatures to ignite the
combustible mixture?

There can be a lot of reasons - lack of lubrication due to oil
deterioration, reduced lubricating quality of the oil, oil pump
mechanism fault, oil filter choked, worn out parts leading to
lessen oil pressures, etc. Whenever there is a hotspot sufficient
to ignite the combustible mixture an explosion will occur. That
is the extreme case.

Let’s see what can happen that can lead to that extreme case of
an explosion.

All the above reasons for lubrication failure or deterioration
will gradually cause the machine to operate poorly, wear out the
moving parts, cause oil spills and carry over of the oil in the
air passages and increased heat built-up.

Now comes the cooling part. Is there a lack of cooling? If the
high temperatures due to rubbing of parts from the above are not
cooled down sufficiently, the heat will build up. The
intercoolers play a very important role in removing the heat?

There are also many other reasons for the lack of cooling.

When the heat transfer surfaces have been coated by films of
scale or carbon it will definitely affect the cooling process.
The heating surfaces may have been reduced due to choked passages
for the cooling medium in the heat exchanger. The cooling medium
itself may be too hot probably due to a fault in another machine
like the cooling tower where the heat can be taken away to the
atmosphere.

The flow of coolant can sometimes be the culprit. When the
cooling pump fails, or the driving belt snaps there will be a
lack of coolant flow. One must also find out whether the valves
for coolant have been accidentally closed or not.

Very often, the effects build upon one another in a vicious cycle
- poor heat transfer leads to more heat that carbonizes more oil
which coats the heat transfer surfaces more…which leads to
worse heat transfer…

Therefore use oil lubricated air compressors with caution. If
your air compressors have been running for a long time, chances
are, your air compressor pipelines may have already accumulated a
sizable amount of oil carried over together with the air flow
during operation.

Does your air compressor work non-stop? Is the inter-cooler or
the after-cooler efficient? Is your compressed air hot? These are
the questions you have to ask yourself.

The oil film in the pipes turns to carbon with heat. The
oxygen-rich and moist atmosphere inside the pipes can turn the
oil into acids that can further deteriorate the oil to form other
organic compounds, perhaps some highly flammable products.

It just needs a spark or a hot spot to ignite this.

Boom!!

Did I frighten you?

What you need is good preventive maintenance. An air compressor
working at peak condition with good cooling, good lubricating
pressures, and good lubricant and good parts should give
trouble-free performance throughout its lifetime.

Sometimes the compressor may have reached the point of no return
- coated coolers leading to high temperatures that lead to more
coated cooling surfaces that lead to higher temperatures… In
this case it is safer to discard the compressor altogether and
obtain an entirely new compressor unit. It could be more
economical - and safer!

If you do that, do ensure that preventive maintenance is done
regularly to keep the unit at peak operating conditions all the
time.

An explosion in an air compressor can have grave consequences.
Don’t take any chances. Perform regular preventive maintenance or
buy a new unit before an explosion occurs.

Until next time

Locate good air compressors for your garage and workshop here:

Eastwood

Many years of working experience in Marine, Facilities,
Construction has given the author material for writing e-books
and articles related to engineering, and management.

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