Tag: air dryers

Compressed Air Pipe

The Power of Deliquescent Driers in Compressed Air Systems

Published on by Jordan T ShouseLeave a comment

In industrial manufacturing, compressed air is the unsung hero powering tools, machinery, and processes across manufacturing, painting, blasting, and beyond. But here’s the catch: moisture. That sneaky water vapor lurking in your compressed air lines can wreak havoc, causing corrosion, freezing, and contaminating sensitive equipment. Deliquescent driers are low-maintenance systems designed to tackle humidity head-on. In this blog, we’ll dive into what makes these driers tick, their pros and cons.

What Are Deliquescent Driers, Anyway?

Picture this: a simple tank packed with hygroscopic (water-loving) salt tablets that dissolve into a brine as they absorb moisture from compressed air. That’s the 1000-foot view of a deliquescent drier. Unlike refrigerated or desiccant dryers that rely on complex refrigeration cycles or regeneration, deliquescent driers use chemistry to do the heavy lifting. The process is elegantly straightforward:

  • Incoming air enters the bottom of the vessel, preheated from compression and loaded with water vapor.
  • It flows upward through a bed of deliquescent desiccant—typically formulated from salts like calcium chloride, lithium chloride, or potassium chloride.
  • The salts “deliquesce” (hence the name), attracting and dissolving water vapor into a liquid brine that collects at the base.
  • Dry air exits the top, with a pressure dew point suppressed by about 15-20°F below the inlet temperature, depending on conditions.

No electricity, no moving parts—just pure, passive drying. These driers have been a staple since the 1940s, especially in rugged settings like petrochemical plants, outdoor blasting ops, or mobile equipment where reliability is the largest concern.

Why Choose Deliquescent Driers? The Pros (and a Few Cons)

Deliquescent driers aren’t for every scenario, but when they fit, they’re a game-changer. Let’s break it down:

The Advantages:

  • Zero Energy Consumption: No power required means lower operating costs and no electrical hazards in wet or explosive environments. Ideal for remote sites or intermittent use.
  • Rugged and Portable: Mount them indoors or outdoors—they thrive in extreme temps, even subzero conditions, with the right setup. Perfect for mobile contractors in painting or abrasive blasting.
  • Low Maintenance: Just drain the brine every 8-hour shift and top up the desiccant a few times a year. A sight glass lets you monitor levels at a glance.
  • Cost-Effective Upfront: Cheaper to buy and install than high-tech alternatives, with no filters or separators to fuss over.

The Drawbacks:

  • Limited Dew Point Control: They suppress dew point by a fixed amount (e.g., 20°F), so hot inlet air means warmer outlet air—fine for many apps but not ultra-dry needs.
  • Corrosion Potential: The brine is salty and corrosive, so vessels need robust coatings, and downstream lines require after filters to catch salt carryover.
  • Pre-filtration Required: Oil from compressors can foul the desiccant, so a coalescing pre-filter is a must.

In short, if you’re blasting in humid conditions, painting in the field, or running air tools in cold weather, deliquescent driers deliver freeze-proof, reliable performance without the fuss.

At EXAIR Corporation, we’re keen on compressed air efficiency. The attention to detail we pay to our products – from design, to manufacturing & assembly, to availability, and right on through to technical support – bears out our commitment to helping you get the most out of your compressed air system. If you’ve got questions, Give me a call.

Jordan Shouse, CCASS

Application Engineer

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Image courtesy of Brian S. Elliott, Wikimedia Commons Creative Commons Attribution-Share Alike 4.0 International License

Refrigerated Air Dryers

Published on by John BallLeave a comment

Whenever air gets compressed, it reduces the space for the water molecules to remain as a vapor; which causes condensation.  For this, compressed air dryers are an important part of a compressed air system.  They are designed to remove moisture to prevent condensation further downstream in the system.  The three main types of dryers are refrigerated, desiccant, and membrane. For this blog, I will cover the refrigerant-type compressed air dryers.

Compressed air dryers are rated with a dew point rating.  A dew point is the temperature at which the air has a relative humidity of 100%.  Since the air cannot become more saturated with water than 100%RH, water will condense and fall out like “rain”.  You can see this effect during the cool mornings when dew forms on the grass.  Compressed air dryers are designed to reduce the dew point temperature of your compressed air.  For a refrigerant type, they are near the dew point temperature of 38oF (3oC).  Like a refrigerator, they use refrigerant to cool the compressed air.  We cannot go below this temperature as it could form ice inside the dryer.  But, as long as the ambient temperature does not go below 38oF (3oC), liquid water will not be present in the pneumatic system. 

There are two main types of refrigerated air dryers; cycling and non-cycling.  Cycling type refrigerant air dryers will cool a liquid mass, generally a glycol-water mixture, to a set-point and turn off.  The liquid will go through an air-to-liquid heat exchanger to remove the heat from the compressed air.  Referring to the cycling action, when the liquid mass goes above the set point, the refrigeration system will restart and cool the liquid mass again.  The cycling refrigerant air dryers are more expensive, but they are more efficient. 

Non-cycling refrigerant air dryers are more common.  The refrigeration system continues to run through an air-to-air heat exchanger to cool the compressed air.  It is similar to your AC system in your car.  With this type of system, they are more susceptible to the environment, i.e., temperature, elevation, and humidity.  So, adjustments are required for proper installation. 

With both types of refrigerant dryers, the internal compressed air section is very similar.  They will have a filter separator to remove the liquid that is created from the condensation from the cold temperatures.  They also have an additional air-to-air heat exchanger.  This will provide two important features for the refrigerated air dryers.  As the cold air leaves the refrigerant section, it helps to cool the incoming compressed air.  This will make the system more efficient.  And as the hot incoming compressed air helps to warm the cold air leaving the dryer, it will stop the condensation of liquid water on the outside of the pipes.  Like the dew forming on the grass during cool mornings, the same will occur with the compressed air piping system. 

Moisture-laden compressed air can cause issues such as increased wear on the pneumatic tools, the formation of rust in piping and equipment, quality defects in painting processes, and frozen pipes in colder climates.  Regardless of what products you’re using at the point-of-use, a compressed air dryer is undoubtedly a critical component of the compressed air system.  Delivering clean, dry air to your EXAIR Products or other pneumatic devices will help to ensure a long life out of your equipment.  If you wish to discuss more about your compressed air system or how EXAIR can provide a more efficient way to use that compressed air, an Application Engineer will be happy to assist you. 

John Ball, CCASS


Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Photo: Grass morning dew by RuslanSikunov.  Pixabay License

Intelligent Compressed Air: What You Need To Know About Deliquescent Dryers

Published on by Russ BowmanLeave a comment

Moisture free air is a “must” for industrial use, for a number of reasons:

  • An awful lot of distribution systems incorporate iron pipe. It’s inexpensive, readily available, easy to work with, rated for pressure, and has a long history of successful installations. Iron pipe will also oxidize (make rust) in the presence of water:
Here’s what we find a lot of the time inside a Reversible Drum Vac that’s been sent in for refurbishment because it’s not drawing effective vacuum anymore.
  • Regardless of what your distribution lines and components are made of, water droplets can erode them. Compressed air itself is a gas; it follows the curves in elbows, and flows around valve discs & regulator diaphragms. Water droplets, on the other hand, run full speed INTO those things, often at high velocity. This eventually causes pitting, which is bad enough…those pits, though, are little pockets for salts, acids, or alkalines to effect their destructive little chemical reactions.
  • When used for blow off applications, anything in your compressed air will get on anything you’re blowing off. If the intent is to remove moisture from a surface, moisture in your compressed air supply decidedly works against your goal.
  • Water can freeze as it is carried along with air flow through orifices. This can quickly block the flow of air. The US Navy lost a submarine, USS Thresher (SSN-593) and all hands in 1963. A number of factors contributed to the sinking, but a significant one was that compressed air being blown into the ballast tanks (to create negative buoyancy) had higher than permissible moisture content, and froze in orifice plates in the lines. The ballast tanks stayed full of water, and 129 sailors & shipyard personnel died as the boat passed crush depth.

There are a number of types of air dryers that are commonly fitted to industrial air compressors to take care of moisture problems. The least expensive one of these is the Single Tower Deliquescent Dryer. Here’s how they work:

Deliquescent dryer: how it works (1)
  • Incoming compressed air enters near the base, where a form of mechanical separation occurs…the air flows back & forth, around trays of desiccant.  The simple act of changing direction causes some of the water to just fall out and collect in the bottom.
  • The air then flows upwards through the desiccant bed. The desiccant in a deliquescent dryer absorbs moisture (as opposed to the adsorption that occurs in a regenerative desiccant dryer) until they get so wet, they dissolve.
  • After the desiccant does its job, moisture free air flows out the top, and gets on with it’s work.

In addition to the low price tag, other things to like about them are:

  • Low pressure drop.
  • No moving parts or electrical components.
  • Can be used outdoors, and in hazardous, mobile, dirty, or corrosive environments.

Of course, there are things to NOT like about them as well:

  • Limited suppression of dew point – because they are drying the air to a specific relative humidity, as opposed to a specific dew point, the attainable dew point is dependent on the incoming air temperature, the chemical composition of the desiccant salt, and the ambient temperature where it’s installed. Unless you use some sort of specialty salt desiccant, the typical dew point is only 20-25ºF lower than the air inlet temperature.
  • Desiccant carryover – speaking of those specialty salts, they’re even more corrosive than the basic sodium chloride that’s often used. Any carryover will wreak havoc on your distribution system and air operated devices.

Deliquescent dryers’ particular set of “pros and cons” presents challenges for their use in industrial settings, for sure. But if the primary concern is preventing pipes from freezing up, then their low cost, low maintenance, and simplicity make them a great choice.

At EXAIR Corporation, we’re keen on compressed air efficiency. The attention to detail we pay to our products – from design, to manufacturing & assembly, to availability, and right on through to technical support – bears out our commitment to helping you get the most out of your compressed air system. If you’ve got questions, we can talk about this all day long…and most of the time, we do. Give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Image courtesy of Brian S. Elliott, Wikimedia Commons Creative Commons Attribution-Share Alike 4.0 International License

Supply Side Review: Deliquescent Type Dryers

Published on by Brian FarnoLeave a comment

As mentioned in my post last week.  The supply side of compressed air systems within a facility is critical to production.  The quality of air produced by your compressor and sent to the demand side of the system needs to be filtered for both moisture and particulate.  One method to dry the air, that is the topic for this blog, is deliquescent type dryers.

These dryers operate like an adsorbent dryer such as a desiccant medium dryer.  The main variance is that the drying medium (desiccant) actually undergoes a phase change from solids to liquids.  Because of this the material is used up and cannot be returned to its original state for reuse.   The liquids formed by the desiccant dissolving in the removed water vapor are then filtered out of the air stream before it is passed on to the demand side of the air system.

There are many compounds that are used to absorb the moisture in the wet compressed air.  A few options are potassium, calcium, or sodium salts and many that contain a urea base.  The desiccant compound must be maintained at a minimum level for the dryer to contain enough media to successfully dry the air.

These dryers are generally a single tank system that is fed with compressed air from a side port near the bottom of the tank.  The air then travels up past drip trays where the desiccant and water mixture fall and ultimately ends up in the bottom of the tank.  The air then goes through a material bed that must be kept at a given level in order to correctly absorb the moisture in the air.  The dry air is then pushed out the top of the tank.

As the desiccant material absorbs the liquid from the compressed air flowing through the tank it falls onto the drip trays and then into the bottom of the tank where it is drained out of the system.  This process can be seen in the image below.

 

Deliquescent type compressed air drying system
How a deliquescent air dryer works – 1(VMAC Air Innovated, 2017)

 

The dew point that this style dryer is able to achieve is dependent on several variables:

  • Compressed air temperature
  • Compressed air pressure / velocity
  • Size and configuration of the tank
  • Compression of the absorption media
  • Type of absorption media and age of media

These dryers are simplistic in their design because there are no moving parts as well as easy to install and carry a low startup cost.

Some disadvantages include:

  • Dewpoint range 20°F – 30°F (Again this is according to the media used.)
  • Dissolved absorption material can pose a disposal issue as it may not be able to be simply put down a drain
  • Replacement of the absorption material

Even with disadvantages the ability to supply the demand side of a compressed air system for a production facility is key to maintaining successful operations.  If you would like to discuss any type of compressed air dryer, please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

1 – Deliquescent Dryer Image: VMAC Air Innovated: The Deliquescent Dryer – https://www.vmacair.com/blog/the-deliquescent-dryer/