Tag: air drier

Compressed Air System Equipment – What You Need To Know

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The use of compressed air in industry is so widespread that it’s long been called “the fourth utility” (along with electricity, water, and natural gas). As a function of energy consumption (running an air compressor) to energy generated (operation of pneumatic equipment), only 10-15% of the energy consumed is converted to usable energy stored as compressed air. Its “bang for the buck”, however, comes when you consider the total cost of ownership – yes, it costs a lot to generate, but:

  • It’s relatively safe, when compared to the risks of electrocution, combustion, and explosion associated with electricity & natural gas.
  • Air operated tools, equipment, and products are generally much cheaper than their electric, gas, or hydraulic powered counterparts.
  • Air operated products, like anything, require periodic maintenance, but oftentimes, that maintenance simply comes down to keeping the air supply clean and moisture free, unlike the extensive (and expensive) maintenance requirements of other industrial machinery.

Even with these advantages, though, it’s still critical to get all you can out of that 10-15% of the energy you’re consuming to make that compressed air, and that starts with having the right stuff in the right place. Now, all of the following “stuff” might not apply to every compressed air system. I once worked in a repair shop, for example, with a small compressor that was used for a couple of blow off guns, impact drivers, and a sidearm grinder. I’ve also done field service in facilities with hundreds of pneumatic cylinders & air motors that operated their machinery. Those places had even more “stuff” than I’m devoting space to in this blog, but here’s a list of the “usual suspects” that you’ll encounter in a properly designed compressed air system:

  • Air compressor. I mean, of course you need a compressor, but the size and type will be determined by how you’re going to use your air. The small repair shop I worked in had a 5HP reciprocating positive displacement compressor with a 50 gallon tank, and that was fine. The larger facilities I visited often had several 100 + HP dynamic centrifugal or axial compressors, which get more efficient with size.
  • Air preparation. This includes a number of components that can be used to cool, clean, and dry the air your compressor is generating:
    • Pressurizing a gas raises its temperature as well. Hot compressed air could cause unsafe surface temperatures and can damage gaskets, seals, and other components in the system. Smaller compressors might not have this problem, as the heat of compression is often dissipated through the wall of the receiver tank and the piping at a rate sufficient to keep the relatively low (and often intermittent) flow at a reasonable temperature. Larger compressors usually come with an aftercooler.
    • The air you compress likely has a certain amount of moisture in it…after nitrogen and oxygen, water vapor usually makes up more of the content of atmospheric air than all other trace gases combined. There are a number of air dryer types; selection will be dictated by the specifics of your facility.
    • Your air is going to have other contaminants in it too. We did welding & grinding in the repair shop where our compressor sat in the corner. We kept a few spare intake filters handy, and replaced them regularly. In conjunction with the aftercooler & dryer, larger industrial compressors will also have particulate filters for these solids. For extra protection, coalescing filters for oil vapor, and adsorption filters for other gases & liquid vapors, are specified.
  • Distribution. In the repair shop, we had a 3/4″ black iron pipe that ran across the ceiling, with a few tees & piping that brought the air down to the individual stations where we used it. The larger facilities I visited had larger variations of this “trunk and branch” type network, and some were even big enough to make use of a loop layout…these were especially popular when multiple air compressors were located throughout the facility. In addition to black iron, copper & aluminum pipe (but NEVER PVC) are commonly used too.
  • Condensate removal. The small repair shop compressor had a valve on the bottom of the tank with a small hose that we’d blow down into a plastic jug periodically. Larger systems will have more complex, and oftentimes automated condensate management systems.

So, that’s the system-wide “stuff” you’ll usually encounter in a properly designed compressed air system. After that, we’ll find a number of point-of-use components:

  • Air preparation, part 2. The compressor intake & discharge filtration mentioned above make sure that you’re putting clean air in the distribution piping. That’s fine if your distribution piping is corrosion resistant, like aluminum or copper, but black iron WILL corrode, and that’s why you need point-of-use filters. EXAIR Automatic Drain Filter Separators have 5 micron particulate elements, and centrifugal elements that ‘spin’ any moisture out. If oil is an issue, our Oil Removal Filters have coalescing elements for oil/oil vapor removal, and they provide additional particulate protection to 0.03 microns.
  • Pressure control. Your compressor’s discharge pressure needs to be high enough to operate your pneumatic device(s) with the highest pressure demand. Odds are, though, that not everything in your plant needs to be operated at that pressure. EXAIR Pressure Regulators are a quick & easy way to ‘dial in’ the precise supply pressure needed for specific products so they can get the job done, without wasting compressed air.
  • Storage. This could also be considered system “stuff”, but I’m including it under point-of-use because that’s oftentimes the reason for intermediate storage. Having a ready supply of compressed air near an intermittent and/or large consumption device can ensure proper operation of that device, as well as others in the system that might be “robbed” when that device is actuated. They’re good for the system, too, as they can eliminate the need for higher header pressures, which cause higher operating costs, and increased potential for leaks. EXAIR Model 9500-60 60 Gallon Receiver Tanks are an ideal solution for these situations.

For more information on proper installation and use of compressed air system “stuff” like this, the Compressed Air & Gas Institute’s Compressed Air and Gas Handbook has a good deal of detailed information. The Air Data section of EXAIR’s own Knowledge Base is a great resource as well.

Of course, all the attention you can pay to efficiency on the supply side doesn’t matter near as much if you’re not paying attention to HOW you’re using your compressed air. EXAIR Intelligent Compressed Air Products are designed with efficiency, safety, and noise reduction in mind. Among the other ways my fellow Application Engineers and I can help you get the most out of your compressed air system, we’re also here to make sure you get the right products for your job. To find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Intelligent Compressed Air: What You Need To Know About Deliquescent Dryers

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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

Compressed Air Supply Side: What Is A Deliquescent Dryer, And When Would You Use One?

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As we head in to the colder months here in Ohio, I will soon be getting my humidifier out of the basement and set up in my bedroom. The dry air that accompanies the onset of winter chaps my lips, cracks the skin on my knuckles, affects my nasal passages, and oftentimes makes me wake up with a sore throat…something I definitely don’t want to happen in the middle of a pandemic! So I put some water vapor in my home’s air, on purpose, to take care of all of that.

Moisture in an industrial compressed air system, however, isn’t good for anything.  It’ll corrode your pipes, get rust in your pneumatic tools, motors, and cylinders, and spit out of your blow off devices, all over whatever you’re using your air to blow off.  Depending on the type of compressor, where, and how, it’s used, there are different types of dryers.  Today, dear reader, we’re taking a look at one of the most basic moisture removal systems: the deliquescent dryer.  The principle of operation is as follows:

  • 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 a certain amount of free liquid 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.
  • The desiccant level has to be monitored (commonly via a sight glass) so it can be replaced as it’s consumed.
  • After the desiccant does its job, moisture free air flows out the top, and gets on with it’s work.

Deliquescent dryers, owing to their simplicity, are the least expensive air dryers.  They have no moving parts and no electricity, so the only maintenance involved is replacing the desiccant media as it’s consumed.  This makes them especially popular in mobile/on-site applications involving portable or tow-behind, engine driven compressors, since they don’t need power to run.

There are several disadvantages, also owing to their simplicity:

  • The deliquescent media has to be periodically replenished.  If you don’t stay on top of it, you can find yourself shut down while you go back to the shop to get a big bag of salt.  That’s time your boss can’t charge your customer for.  Also, the cost of the new media is a continual operating cost of the dryer…something you don’t have to account for with the regenerative desiccant models.
  • Disposal of the waste media can be a concern…you definitely want to check your local environmental regulations before dumping it in the garbage.  Your boss won’t like talking to the EPA about THAT either.
  • They have to be equipped with a particulate filter on the discharge to keep the deliquescent media (which, being a salt, is corrosive in nature) from entering your system.  That would be even worse than water moisture…which this is there to prevent in the first place.
  • They don’t get near as low of a dewpoint as other dryers – the best you can hope for is 20°F to 30°F.  Which is fine, given the above mentioned nature of applications where these are commonly used.  You just wouldn’t want to use them to supply a product like an EXAIR Vortex Tube…which can turn that in to -40°F cold air, causing the water vapor to turn to liquid, and then to ice.  In a hurry.

EXAIR Corporation is in the business of helping you get the most out of your compressed air.  If you want to learn more, please follow our blog.  If you have specific questions, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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(1) – Deliquescent Dryer Image: VMAC Air Innovated: The Deliquescent Dryer – https://www.vmacair.com/blog/the-deliquescent-dryer/

Refrigerant Compressed Air Dryer Systems

Published on by Russ BowmanLeave a comment

No matter what your use of compressed air entails, moisture is very likely an issue.  Air compressors pressurize air that they pull in straight from the environment and most of the time, there’s at least a little humidity involved.  Now, if you have an industrial air compressor, it’s also very likely that it was supplied with a dryer, for this very reason.

There are different types of dryer systems, depending on your requirements.

For practical purposes, “dryness” of compressed air is really its dew point.  That’s the temperature at which water vapor in the air will condense into liquid water…which is when it becomes the aforementioned issue in your compressed air applications.  This can cause rust in air cylinders, motors, tools, etc.  It can be detrimental to blow offs – anything in your compressed air flow is going to get on the surface of whatever you’re blowing onto.  It can lead to freezing in Vortex Tube applications when a low enough cold air temperature is produced.

Some very stringent applications (food & pharma folks, I’m looking at you) call for VERY low dew points…ISO 8673.1 (food and pharma folks, you know what I’m talking about) calls for a dew point of -40°F (-40°C) as well as very fine particulate filtration specs.  As a consumer who likes high levels of sanitary practice for the foods and medicines I put in my body, I’m EXTREMELY appreciative of this.  The dryer systems that are capable of low dew points like this operate as physical filtration (membrane types) or effect a chemical reaction to absorb or adsorb water (desiccant or deliquescent types.)  These are all on the higher ends of purchase price, operating costs, and maintenance levels.

For many industrial and commercial applications, though, you really just need a dew point that’s below the lowest expected ambient temperature in which you’ll be operating your compressed air products & devices.  Refrigerant type air dryers are ideal for this.  They tend to be on the less expensive side for purchase, operating, and maintenance costs.  They typically produce air with a dew point of 35-40°F (~2-5°C) but if that’s all you need, they let you avoid the expense of the ones that produce those much lower dew points.  Here’s how they work:

  • Red-to-orange arrows: hot air straight from the compressor gets cooled by some really cold air (more on that in a moment.)
  • Orange-to-blue arrows: the air is now cooled further by refrigerant…this causes a good amount of the water vapor in it to condense, where it leaves the system through the trap & drain (black arrow.)
  • Blue-to-purple arrows: Remember when the hot air straight from the compressor got cooled by really cold air? This is it. Now it flows into the compressed air header, with a sufficiently low dew point, for use in the plant.

Non-cycling refrigerant dryers are good for systems that operate with a continuous air demand.  They have minimal dew point swings, but, because they run all the time, they’re not always ideal when your compressed air is not in continuous use.  For those situations, cycling refrigerant dryers will conserve energy…also called mass thermal dryers, they use the refrigerant to cool a solution (usually glycol) to cool the incoming air.  Once the glycol reaches a certain temperature, the system turns on and runs until the solution (thermal mass) is cooled, then it turns off.  Because of this, a cycling system’s operating time (and cost) closely follows the compressor’s load – so if your compressor runs 70% of the time, a cycling dryer will cost 30% less to operate than a non-cycling one.

EXAIR Corporation wants you to get the most out of your compressed air system.  If you have questions, I’d love to hear from you.

Russ Bowman
Application Engineer
EXAIR Corporation
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