What Makes A Compressed Air System “Complete”?

It’s a good question.  When do you know that your compressed air system is complete?  And, really, when do you know, with confidence, that it is ready for use?

A typical compressed air system. Image courtesy of Compressed Air Challenge.

Any compressed air system has the basic components shown above.  A compressed air source, a receiver, dryer, filter, and end points of use.   But, what do all these terms mean?

A compressor or compressed air source, is just as it sounds.  It is the device which supplies air (or another gas) at an increased pressure.  This increase in pressure is accomplished through a reduction in volume, and this conversion is achieved through compressing the air.  So, the compressor, well, compresses (the air).

A control receiver (wet receiver) is the storage vessel or tank placed immediately after the compressor.  This tank is referred to as a “wet” receiver because the air has not yet been dried, thus it is “wet”.  This tank helps to cool the compressed air by having a large surface area, and reduces pulsations in the compressed air flow which occur naturally.

The dryer, like the compressor, is just as the name implies.  This device dries the compressed air, removing liquid from the compressed air system.  Prior to this device the air is full of moisture which can damage downstream components and devices.  After drying, the air is almost ready for use.

To be truly ready for use, the compressed air must also be clean.  Dirt and particulates must be removed from the compressed air so that they do not cause damage to the system and the devices which connect to the system.  This task is accomplished through the filter, after which the system is almost ready for use.

To really be ready for use, the system must have a continuous system pressure and flow.  End-use devices are specified to perform with a required compressed air supply, and when this supply is compromised, performance is as well.  This is where the dry receiver comes into play.  The dry receiver is provides pneumatic capacitance for the system, alleviating pressure changes with varying demand loads.  The dry receiver helps to maintain constant pressure and flow.

In addition to this, the diagram above shows an optional device – a pressure/flow control valve.  A flow control valve will regulate the volume (flow) of compressed air in a system in response to changes in flow (or pressure).  These devices further stabilize the compressed air system, providing increased reliability in the supply of compressed air for end user devices.

Now, at long last, the system is ready for use.  But, what will it do?  What are the points of use?

Points of use in a compressed air system are referred to by their end use.  These are the components around which the entire system is built.  This can be a pneumatic drill, an impact wrench, a blow off nozzle, a pneumatic pump, or any other device which requires compressed air to operate.

If your end use devices are for coating, cleaning, cooling, conveying or static elimination, EXAIR Application Engineers can help with engineered solutions to maximize the efficiency and use of your compressed air.  After placing so much effort into creating a proper system, having engineered solutions is a must.

Lee Evans
Application Engineer

Intelligent Compressed Air: Membrane Dryers – What are they and How Do they Work?

Recently we have blogged about Compressed Air Dryers and the different types of systems.  We have reviewed the Desiccant and Refrigerant types of dryers, and today I will discuss the basics of  the Membrane type of dryers.

All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air.  At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation.  When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form.  Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.

Membrane Dryers are the newest type of compressed air dryer. Membranes are commonly used to separate gases, such as removing nitrogen from air. The membrane consists of a group of hollow fiber tubes.  The tubes are designed so that water vapor will permeate and pass through the membrane walls faster than the air.  The dry air continues on through the tubes and discharges into the downstream air system. A small amount of ‘sweep’ air is taken from the dry air to purge and remove the water vapor from inside the dryer that has passed through the membrane tubes.

Membrane Dryer
Typical Membrane Dryer Arrangement

Resultant dew points of 40°F are typical, and dew points down to -40°F are possible but require the use of more purge air, resulting in less final dry compressed air discharging to the system.

The typical advantages of Membrane Dryers are-

  1.  Low installation and operating costs
  2.  Can be installed outdoors
  3.  Can be used in hazardous locations
  4.  No moving parts

There are a few disadvantages to consider-

  1. Limited to low capacity systems
  2. High purge air losses (as high as 15-20% to achieve lowest pressure dew points
  3. Membrane can be fouled by lubricants and other contaminants, a coalescing type filter is required before the membrane dryer.

If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Membrane Dryer Schematic – From Compressed Air Challenge, Best Practices for Compressed Air Systems, Second Edition




Intelligent Compressed Air: Refrigerant Dryers and How They Work

We’ve seen in recent blogs that Compressed Air Dryers are an important part of a compressed air system, to remove water and moisture to prevent condensation further downstream in the system.  Moisture laden compressed air can cause issues such as increased wear of moving parts due to lubrication removal, formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates.  The three main types of dryers are – Refrigerant, Desiccant, and Membrane. For this blog, we will review the basics of the Refrigerant type of dryer.

All atmospheric air that a compressed air system takes in contains water vapor, which is naturally present in the air.  At 75°F and 75% relative humidity, 20 gallons of water will enter a typical 25 hp compressor in a 24 hour period of operation.  When the the air is compressed, the water becomes concentrated and because the air is heated due to the compression, the water remains in vapor form.  Warmer air is able to hold more water vapor, and generally an increase in temperature of 20°F results in a doubling of amount of moisture the air can hold. The problem is that further downstream in the system, the air cools, and the vapor begins to condense into water droplets. To avoid this issue, a dryer is used.

Refrigerated Dryer
Fundamental Schematic of Refrigerant-Type Dryer

Refrigerant Type dryers cool the air to remove the condensed moisture and then the air is reheated and discharged.  When the air leaves the compressor aftercooler and moisture separator (which removes the initial condensed moisture) the air is typically saturated, meaning it cannot hold anymore water vapor.  Any further cooling of the air will cause the moisture to condense and drop out.  The Refrigerant drying process is to cool the air to 35-40°F and then remove the condensed moisture.  The air is then reheated via an air to air heat exchanger (which utilizes the heat of the incoming compressed air) and then discharged.  The dewpoint of the air is 35-40°F which is sufficient for most general industrial plant air applications.  As long as the compressed air stays above the 35-40°F temperature, no further condensation will occur.

The typical advantages of Refrigerated Dryers are-

  1.  – Low initial capital cost
  2.  – Relatively low operating cost
  3.  – Low maintenance costs

If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Intelligent Compressed Air: Desiccant Dryers – What are they and How Do they Work?

Desiccant dryer
Heat of Compression Desiccant Dryer

No matter where you are in the world, the atmospheric air will contain water vapor. As this air cools to the saturation point, also known as dew point, the vapor will condense into liquid water. The amount of this moisture will vary depending on both the ambient temperature and the relative humidity. According to the Compressed Air Challenge, a general rule of thumb is that the amount of moisture air can hold at a saturated condition will double for every 20°F increase in temperature. In regions or periods of warmer temperatures, this can create a significant problem. Some problems that can be associated with moisture-laden compressed air include:

  • Increased wear of moving parts due to removal of lubrication
  • Formation of rust in piping and equipment
  • Color variation, adherence, and finish of paint that is applied using moisture-laden compressed air
  • Create unstable conditions for processes that are dependent upon pneumatic controls. Malfunctions due to rust, scale, or clogged orifices can damage product or cause costly shutdowns
  • In colder temperatures, moisture in the compressed air flow can freeze in the control lines

To remove moisture from the lines, a dryer must be installed. One of the most commonly found dryers in a facility are referred to as desiccant dryers. There are three variations of desiccant dryers: Regenerative-Desiccant Dryers, Heat Reactivated Desiccant Dryers, and Heat of Compression Desiccant Dryers.

A Regenerative-Desiccant Dryer uses a porous desiccant that collects and adsorbs the moisture. This allows for large amounts of water to be retained with a minute amount of desiccant. Most regenerative-desiccant dryers consist of two towers. One where wet, moisture-laden compressed air flows through a desiccant bed. A second tower contains desiccant that is being regenerated. A controlled amount of dry air flows through the tower being regenerated, which causes the moisture to release from the desiccant and flow out with the purge flow. This saturated air exhausts to atmosphere. After a set time, the towers will switch and continue this cycle of drying/regenerating.

Another, and more efficient, regenerative-desiccant dryer uses heat to assist in removing water from the desiccant. As the tower is heated, the moisture is no longer adsorbed by the desiccant and is purged through the flow. This style is more efficient than the other styles of dryers because less compressed air is wasted removing the moisture in the tower.

The third type of desiccant dryer is the Heat of Compression dryer. This style utilizes the heat that is generated during compression to accomplish the regeneration of the desiccant. Typically, the heat that is generated from the air compressor is exhausted to atmosphere and wasted. With a heat of compression dryer, this heat is captured and used to regenerate the desiccant. The compressed air passes through the drying section of the desiccant bed, is dried, and exits through the discharge. A portion of the captured heat flows through the opposite side of the dryer to regenerate the desiccant. Afterwards, this hot air passes through a regeneration cooler and is combined with the main air stream. This results in ZERO loss of purge air, making this style of dryer the most efficient available.

If you have questions about how to optimize your compressed air system, contact EXAIR. An Application Engineer is standing by ready to assist you!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD


Heated Desiccant Dryer by Compressor1.  Creative Commons Attribution-NoDerivs 2.0 Generic.

Safety Air Gun Improves Aluminum Extruding Machining Process

I was doing some work around the house Saturday when I heard my wife shouting out from our laundry room….”Something is wrong with our dryer. This is the 3rd time I’ve restarted it and the clothes are still wet!”. Now having been in this situation before, I knew this meant that the exhaust was probably clogged with lint (again).

See, our laundry room runs parallel to our family room and the exhaust ducting goes up and then across the laundry room, across the family room and then exhausts on the side of the house. (I would like to find the person who thought this was a good idea!). I have thought about re-routing the ducting but the only other option would be to have the exhaust on the front of the house which will “never happen” (per my wife). So I usually end up taking my vacuum and attaching as many extensions as possible to reach as much of the ducting as I can. I have tried a few other methods with no success – like taking my leaf blower and, from the outside of the house, blow the lint back towards the laundry room and into a garbage can. (hint: make SURE your wife is not in the laundry room when attempting this…. They don’t react too well when they get covered in lint!)

This made me think of an application I worked on last week with an aluminum extrusion company. The customer cuts lengths of aluminum siding from 1’ up to 10’ in length and, standing at one end of the material, are using a standard blow gun to try and blow out the chips but are unsuccessful. They reviewed our website but were still unsure what product may fit their needs best, so they gave us a call.

We discussed their application and the customer was able to email pictures. After reviewing the pictures I recommended using one of our Soft Grip Safety Air Guns with our Model # HP1125, 2” Flat High Power Super Air Nozzle and a 72” extension.  The Soft Grip Safety Air Gun is constructed of cast aluminum and includes a hook for hanging in a convenient location. The Model # HP1125, 2” High Power Flat Super Air Nozzle, produces 2.2 lbs. of force @ 80 PSIG and utilizes 37 SCFM with a sound level of 83 dBA. This would also meet or exceed the OSHA standards for safety, per Standard 1910.242(b) for 30 psi dead end pressure, and allowable noise exposure per Standard 29 CFR – 1910.95(a).

An EXAIR model HP1230 Soft Grip Safety Air Gun

To discuss your application or help with selecting the right product, contact an application engineer.

Justin Nicholl
Application Engineer

Dirty Compressed Air Consequences Are Avoidable

I would like to discuss the importance of clean and dry filtered air.  This all comes from some discussions I have had with customers over my time here at EXAIR, as well as from my time in the machine tool industry. It is notable to state that we simply ask for clean/dry air to run through our products, not “instrument” or “process” air which is typically held at a different pressure, temperature, or volume and can be more expensive to generate. All of EXAIR’s products use general plant air and can be cleaned up with simple point of use filters.

Clean and dry compressed air is essential for ensuring a long and easy life of almost any compressed air product.   One product in particular that I have some data on is the EXAIR Line Vac.  The pictures below show the inside wall of a Stainless Steel Line Vac.  This unit was used in a harsh outdoor environment.   The compressor was not maintained and did not have any form of filtration on the lines feeding the Line Vac unit. The first picture shows where all the dirt and particulate were impacting the internal generator wall as it entered the air chamber.

Damaged Generator

The two dark grey marks are actually the impact points on the unit.   There is only one air inlet on the Line Vac, this means that the unit was taken apart during the two months and actually inspected then put back together and the generator was rotated slightly during this process.  These spots are similar to what sandblasting does to metal, just to illustrate how much particulate was in the air stream. Since the air has not yet reached its full velocity within the Line Vac, it has left only those visible surface blemishes.

As the air begins to exit the array of small generator holes it begins to rapidly increase in velocity while it is trying to expand to atmospheric conditions.  Because of this increased velocity, the wear the generator holes experience is greater and as seen below it is causing some extreme wear.

Worn Generator Holes

To give you an idea of what a new generator should look like is below. Here you can see uniform holes that go precisely through the generator.


To prevent a disaster like this from happening to your end-use compressed air products, all you need are some simple, low maintenance filters.   EXAIR offers dirt / water filter separators that will filter your compressed down to 5 micron particulate size.   The will catch the good majority of rust, water, and dirt within your compressed air system.   Then you can also install an oil removal filter which will filter all oils and particulate out of your compressed air system down to 0.03 micron particulate level.

Each of these units are great point of use filtration to keep any of your processes from experiencing what this Line Vac experienced.   If you have any questions about the quality of your compressed air or why you are seeing failures in product on your compressed air system, contact us.

Brian Farno
Application Engineer

Excellent Customer Service Is The Only Way To Live

I have recently had a few dealings with other companies recently which has left me with two reactions: 1) How they are still in business? and 2) They really have their customer service running well.  The first company was, of course, a large conglomerate that provides our home internet service. The second company was a web-based company providing clothes dryer repair parts.


So the first company, it is a local supplier of internet service.   I called to try and upgrade my service to higher speeds and see when I could get it changed.   I have had their service for over 8 years and haven’t had a whole lot of issues with them, everything has been pretty good.   That is until I tried to use their live chat feature on the website where I was told one price for the service, I then questioned why that price didn’t match the one on their site and was told in order to get that price I would need to call a certain number and speak with a representative.   I thanked the person and made the call.  It took me about 15 minutes or so to get to an actual human and then ended up the price still wasn’t the same and got a little run around on features, so I decided I would look at competitive service.

I spoke to their competitor in my area, which was very straightforward with pricing and answered every question I had directly and gave me a very speedy installation date of the next day, but were about 5 dollars more expensive.  So I called my current provider back and got yet another different price but did finally get some straight answers… and then we got to the installation date – 3 weeks out.   I asked if the fact I was a long-standing customer that was upgrading mattered and found out that is actually hurt my installation date.   Since I was merely an upgrade it was extremely low ranking, but if I signed up for additional services then I would get someone to install it within 3 days. When I expressed my concern for this practice I was greeted with silence and sorry that is just how it is followed by when would you like me to schedule this.

So, needless to say, I contacted their competitor, laid everything out and got the service installed the next day, today I call to cancel my existing service and will hopefully never have to look back.   The moral of the story here is, even though I was a long-standing customer the provider saw no merit in that and actually ranked me even lower than a new account.   They were very cumbersome in how they answered questions which left me feeling uncomfortable and I couldn’t get even the same bad answer from the three different people I spoke with.   Ultimately I left them as a customer and am glad to be with another provider.

As for the second instance, I needed to fix the clothes dryer because it was making some funny noises.   So I took a few pieces off, moved stuff around, didn’t see a whole lot wrong and put it back together.   It started making the noise again so I gave it “The Fonz” treatment (hit it hard) and all was good.   The next time I went to dry something my wife then accused me of not starting the dryer because everything was still wet.   I took a look into it yet again and this time I took the dryer all the way apart thanks to an informal video from the manufacturer. The problem seemed to be some bad preventative maintenance on my part and hair/lint wrapping around a roller guide which cause the  roller to stop and the drum to start going slower, as well as a lot of burnt crud around the heating element. So then the parts search began.   I found a company online whose site was easy to navigate, had lots of pictures, even used their live chat which I got quick responses from, and even found videos of how to fix the exact problem I was having.  So I ordered the parts late at night on Monday, their site showed in stock and shipping the next day.   Tuesday I end up getting a confirmation that the parts will be shipped.  Wednesday I received the parts as well as a follow-up e-mail confirming that the parts had been delivered.


The moral of this interaction as a customer is that I experienced what I hope our customers at EXAIR experience everyday.   All the information I needed was in one place and easy to find,  all the parts were in stock, I got quick responses that were truthful, and in the end even after I ordered the part  I still got great customer service.  Needless to say I have bookmarked their site and will be returning.

Here at EXAIR, you don’t get greeted by a robot when you call during business hours, you get greeted by a human.  We do our best to ensure all information you need is accessible from our site, as well as back that support up with our Application Engineering staff being available by phone, e-mail, chat, fax, visits to EXAIR, and even mail if need be.   Then if you decide to order something from us, if it is standard stock, we ship it same day as long as we get the order by 3 PM EST and are shipping within the United States.  Then, we offer helpful videos, as well as support after you have made your purchase.  On top of all that, we stand behind our products with a 30 day guarantee and a 5 year built to last warranty.

30 Day Guarantee

So no matter how small a project you have, or if you are having any issues with your existing supplier for compressed air products, contact us and see if you notice a difference.

Brian Farno
Application Engineer Manager