Intelligent Compressed Air: Deliquescent Dryers – What are They and How do They Work?

EXAIR has written blogs about the different types of dryers that are used to remove liquid from compressed air systems. In this blog, I will be discussing the deliquescent dryer. This dryer falls under the desiccant dryer category, and unlike the regenerative cousins, it is the least commonly used type of dryer. The regenerative desiccant dryers use a medium that will adsorb the water vapor, and the deliquescent dryers use a hygroscopic material that will absorb the water vapor. This salt-like medium has a strong affinity for water, and it comes in a tablet or briquette form. Placed inside a single unit pressure vessel, the “wet” compressed air passes through the bed to become dry. The size of the pressure vessel is determined by the compressed air usage which allows for the proper amount of contact time with the hygroscopic bed. Generally, the dew point will be between 20 to 50 deg. F (11 – 28 deg. C) less than the compressed air inlet temperature. Unlike most dryers, the dew point after deliquescent dryers will vary with the inlet air temperatures.

Vessel Design

The design of vessel is very important for the function of a deliquescent dryer. A grate is required to hold the medium off the bottom. The compressed air will flow from the bottom, up through the bed, and out from the top. The predetermined space between the bed and the bottom of the vessel is used for the liquid that is generated. When “wet” compressed air passes through the bed, the hygroscopic material will absorb the water and change the tablets from a solid into a liquid. Deliquescent dryers got the name from the definition of the verb, “deliquesce” which is “becomes liquid by absorbing moisture from the air”. Once the material is turned into a liquid, it cannot be regenerated. The liquid must be discarded periodically from the vessel and new solid material must be added. With the single tower design, the deliquescent dryers are relatively inexpensive.

Some advantages in using the deliquescent dryers are that they do not require any electricity or have any moving parts. So, they can be used in remote locations, rugged areas, or hazardous locations. They are commonly used to reduce the dew point in compressed air, natural gas, landfill gas and biogas systems. Without the ability for regeneration, no additional compressed air will be lost or used. In comparing the power requirement to other compressed air dryers, the deliquescent dryers have the lowest power requirement at 0.2Kw/100 cfm of air. (This energy rating is only due to the additional power required for the air compressor to overcome the pressure drop in the dryer).

Some disadvantages in using the deliquescent dryers is that the hygroscopic material degrades. The deliquesced liquid does have to be drained and disposed, and new material does have to be added. Even though they do not have any moving parts, they still require periodic maintenance. The deliquescent material can be corrosive. So, after-filters are required to capture any liquid or dust material that may carry over and damage downstream piping and pneumatic components. Also, the variation in the dew point suppression can limit locations and areas where it can be used.

If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Products, you can contact an Application Engineer at EXAIR. We would be happy to hear from you.

John Ball
Application Engineer
Twitter: @EXAIR_jb


Photos:  used from Compressed Air Challenge Handbook

Increasing Efficiency With EXAIR Super Air Nozzles

Earlier this morning I received a phone call from a gentleman in search of a more efficient compressed air solution.  The application was to remove thermoformed plastics from a mold immediately after the mold separates.  In the current state, the application is consuming ~40% of the available compressed air in the facility through the use of (9) ¼” open pipes, consuming a confirmed 288 SCFM at 60 PSIG.  Due to the use of an open pipe, this customer was facing a safety and noise concern through the existing solution.

After discussing the application need and the desire to reduce compressed air use, reduce noise, and add safety, we found a suitable solution in the 1101 Super Air NozzleInstalling (9) of these EXAIR nozzles will reduce the compressed air consumption by over 65%!!!  Calculations for this savings are below.

Existing compressed air consumption:  288 SCFM @ 60 PSIG

Compressed air consumption of model 1101 @ 60 PSIG:  11 SCFM

Total compressed air consumption of  (9) 1101 nozzles:

Air savings:

This is the percentage of air which the new EXAIR solution will consume.  To put it another way, for every 100 SCFM the current solution consumes, the EXAIR solution will only require 34.38 SCFM. Installing these EXAIR nozzles will result in lower operational cost, lower noise levels, and increased safety for this customer – all while maintaining or improving the performance of the blow off solution in this application.

EXAIR Application Engineers are well versed in maximizing efficiency of compressed air systems and blow off needs.  If you have an application with a similar need, contact an EXAIR Application Engineer.  We’ll be happy to help.

Lee Evans
Application Engineer

The Case For The Cold Gun

Albert Einstein famously said, “Nothing happens until something moves.” And unless it’s in a perfect vacuum when it moves, there’s gonna be friction. Especially if it’s in contact with something else besides air.  And where there’s friction, there’s heat. This pretty much applies to almost every single evolution in the manufacture of…well, just about everything.

I’m probably not telling you anything you don’t already know, but heat can be a BIG problem.  It can:

  • Shorten tool life. Not only do worn tools take longer to cut, they can also present safety issues.  You can get hurt WAY worse by a dull blade than a sharp one.
  • Cause thermal expansion. If you’re machining something to a precise tolerance, and friction heat causes it to grow, it won’t be the same size when it cools down.
  • Melt plastics. And even softer metals.  This isn’t good for the part…or the tool, either.

Those are just a few of the problems heat causes in manufacturing operations, and they’ve been traditionally addressed with mist (liquid) coolants.  And they work just fine…most of them are water-based, and if you want to get heat out of a solid piece of something, water will do the job VERY quickly.  Other additives in the coolant provide a measure of lubricity, corrosion control, emulsion prevention, etc.  It’s easy, well-known, and time-tested.  There are some drawbacks, however:

  • It can be messy.  When a part (or a tool) in motion gets sprayed down with liquid, it tends to fling that liquid all over the place.  That’s why most machines fitted with mist coolant have spray shields.
  • Not only is it a hassle to clean up, if you don’t stay on top of the clean-up, it can lead to slip hazards.
  • Speaking of hazards, if you can smell that mist (and you know you can,) that means you’re breathing it in too.  Remember the lubricants, corrosion inhibitors, emulsion preventers, etc., I mentioned above?  Yeah…they’re not all what you might call “good for you.”
  • Recirculation systems are common, which means the coolant sump is gathering solids, so the lines and/or spray nozzles can clog and be rendered useless.

EXAIR Cold Gun Aircoolant Systems not only address all of the above problems with heat, but eliminate all the problems associated with liquid coolant:

  • They incorporate EXAIR’s Vortex Tube technology to produce a stream of cold air.
  • They’re reliable.  There are no moving parts; if you supply them with clean, dry air, they’ll run darn near indefinitely, maintenance free.
  • They’re quick & easy.  With a built-in magnet for mounting and a flexible cold air hose, you can be be blowing cold air right where you want it as quickly as you can attach an air hose and open the valve.
  • Speaking of opening the valve, that’s all it takes to run a Cold Gun.  They’re producing cold air at rated flow and temperature, right away.  No “ramp up” time to get into operation.
  • They’re clean.  That cold air stream just becomes…well, air.  No mess.  No slip.  No clean up.  No smell.  No problem.

We’ve got four Models to choose from, depending on the nature of the application:

Both the standard and the High Power come with a Filter Separator, and are available with a one, or two, outlet cold air hose.

If you need to cool parts or tools down, and want it to be effective and clean, give me a call.

Russ Bowman
Application Engineer
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Adjustable Spot Cooler Keeps Cataract Lenses Cool and Dry During Machining

Neal Raker, International Sales Manager, and myself along with our Hungarian Distributor

During a recent visit with our Hungarian Distributor, I had the opportunity to take a look at an application using some EXAIR Adjustable Spot Coolers and Mini Coolers. The company manufactures cataract lenses and is using the coolers in a dry machining application. The previous process involved using a liquid coolant which caused a washing operation to remove the contaminants before the lenses could move on to the next step of the process. This was not only time consuming, but the solution they needed to use as a coolant was very expensive due to strict regulations that they had to adhere to.

EXAIR’s Adjustable Spot Cooler installed on the lathe

The lenses are set up on a lathe which are precisely cut. The Adjustable Spot Coolers were positioned with the cold airflow just at the point of cutting to keep the temperature at a specific point. If the lenses get too hot, the material becomes less rigid and begins to warp. When this happens, the lens cannot be reworked and must be scrapped. Immediately after coming off of the lathe, an inspector places the lens under a microscope for inspection. At this point, a Mini Cooler is installed to ensure that the temperature of the lens stays cold. If the lens passes inspection, it is immediately placed in a small freezer next to the operator. Temperature probes are in place at several points during the process to ensure that they do not go above the specified temperature.

Mini Cooler installed on the inspection station

By implementing a solution with the Adjustable Spot Cooler, this customer was able to boost productivity by removing a cleaning step from the process and also reduce costs by eliminating the need for the costly coolant solution that was required. If you’d like to replace messy coolant systems in your machining operation with a clean compressed air solution, give us a call. An Application Engineer will be happy to look at your process and recommend the most suitable solution.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD

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




2” Flat Super Air Nozzles Separate Sheets of Metal Film

Heat Exchanger plates

An overseas company manufactures brazed plate heat exchangers. This type of heat exchanger has a series of corrugated plates that are stacked onto each other. It is designed to create a turbulent flow for better heat transfer in a very compact size. The plates inside the heat exchanger are made of 321 stainless steel which is basically a 304 type of stainless steel but with a titanium stabilizer. This company would receive plain sheets of stainless steel material that were stacked on each other in a column. The dimensions of the plates were as follows: 305mm wide by 520mm long with a thickness of 0.5mm (12” Wide X 20.5” Long X 0.02” thick respectively). Each sheet weighed 635 grams (1.4 lbs.). They would set a stack of the stainless-steel sheets at the beginning of a press machine. The press machine would form the corrugated design into the face of the sheet. They were using a pick-and-place vacuum system to lift one sheet at a time to place inside the press. They started having problems with their process when occasionally two or three sheets would stick together. The underlying sheet could either fall onto the floor which would bend the sheet or be stacked inside the press which would cause an improper corrugation. Both issues were causing much scrap as well as downtime in their process .

They contacted EXAIR to find a way to improve the efficiency of their process. They wondered if static could be causing the “sticking” issues. Generally, static forces are really noticed with sheets made of plastic or non-conductive materials. The stronger the static force, the more issues with sticking and misalignment. EXAIR does offer Static Eliminators to remove static forces in applications just like this. But, with plain metal sheets, static is not a problem as the ions are able to balance themselves.

Typically, the main cause for metal sheets to “stick” together is surface tension. Liquid like water has a strong affinity to itself within the molecular structure, called cohesion, and to the surface that it lies on, called adhesion. The cohesion plus the adhesion to the metal surface can have a strong enough force to overcome the weight of the sheets. To break the surface tension, an additional force is required.  An example of surface tension is with nylon tent material. The surface tension of water is strong enough to keep rain drops from penetrating the fabric. If you break the surface tension by touching the tent material, the surface will start to leak water. The same goes for the thin sheets of metal. We just need to break the surface tension to allow the sheets to separate.

2″ Flat Super Air Nozzle

I recommended two pieces of the model 1122, 2” Flat Super Air Nozzles. This nozzle gives a flat air pattern to force air between the sheets. Surface tension is based on force over length. Once the sheets start to separate, the contact length will decrease thus reducing the “sticking” force caused by surface tension. In this application, the amount of cohesion and adhesion forces caused by surface tension were unknown. Oil, water, and other liquids have different surface tensions which would require different amounts of blowing forces. To ensure the proper amount to separate the sheets, I recommended the shim set, model 1132SS.

The shims have different thicknesses that can be installed easily into the 2” Flat Super Air Nozzle to change the amount of blowing force.  In conjunction with a regulator, this customer could “dial” in the proper amount of force required to counteract the surface tension from any type of liquid that may be on the surface of the sheets.  I had them mount one nozzle at two different corners to help “peel” the sheets apart. The customer also tied in a solenoid valve into the compressed air system to cycle on the 2” Flat Super Air Nozzles only during the time when the vacuum system wanted to grab the top sheet. This reduced the amount of compressed air needed for their operation.  After the installation, the procedure ran smoothly without downtime and scrap waste.

If your application is creating scrap and downtime caused by sheets sticking together, EXAIR has many types of products to help eliminate this. Whether the “stickiness” is caused from static or liquid adhesion, an Application Engineer can direct you to the best product to eliminate the “stickiness”. For the overseas company above, we were able to apply a sharp flat burst of air to overcome the surface tension between the sheets.

John Ball
International Application Engineer
Twitter: @EXAIR_jb


Heat Exchanger Plates by epicbeerCreative Common by 2.0


Heat of Compression Dryers

A Heat of Compression regenerative desiccant dryer for compressed air

Before compressed air can be realistically utilized, it needs to be delivered to the point of use with proper volume and pressure, and it should also be clean and have some moisture removed.  We have information available regarding cleaning compressed air, but how do you dry the compressed air?  And why do you dry the compressed air?

Drying compressed air is akin to removing the humidity in the air when using an air conditioning system.  If the moisture is not removed, the effectiveness of the system is reduced and the ability to use the output of the system is reduced as well.

But, from a functional standpoint, what does this really mean?  What will take place in the compressed air system if the air is not dried and the moisture is allowed to remain?

The answer is in the simple fact that moisture is damaging.  Rust, increased wear of moving parts, discoloration, process failure due to clogging, frozen control lines in cold weather, false readings from instruments and controls – ALL of these can happen due to moisture in the compressed air.  It stands to reason, then, that if we want long-term operation of our compressed air products, having dry air is a must.

So, how can we remove the moisture in the compressed air?  One of the most common methods to remove moisture is a regenerative dryer, specifically, heat-of-compression type dryers.  A heat of compression type dryer is a regenerative desiccant dryer which uses the heat generated by the compression of the ambient air to regenerate the moisture removing capability of the desiccant used to dry the compressed air.

When using one of these dryers, the air is pulled directly from the outlet of the compressor with no cooling or treatment to the air and is fed through a desiccant bed in “Tank 1” where it regenerates the moisture removing capabilities of the desiccant inside the tank.  The compressed air is then fed through a regeneration cooler, a separator, and finally another desiccant bed, this time in “Tank 2”, where the moisture is removed.  The output of “Tank 2” is supplied to the facilities as clean, dry compressed air.  After enough time, “tank 1” and “tank 2” switch, allowing the hot output of the compressor to regenerate the desiccant in “tank 2” while utilizing the moisture removing capabilities of the desiccant in “tank 1”.

Heat of compression dryers offer a lower power cost when compared to other dryers, but they are only applicable for use with oil free compressor and to compressors with high discharge temperatures.  If output air temperatures from the compressor are too low, a temperature booster/heater is needed.

If you have questions about your compressed air system and how the end use devices are operating, contact an EXAIR Application Engineer.  We’ll be happy to discuss your system and ways to optimize your current setup.

Lee Evans
Application Engineer


Heated Desiccant Dryer by Compressor1.  Creative Commons License