Types Of Compressed Air System Dryers

Many times, when discussing product selection with a customer, we commonly reference supplying as clean and dry air as possible to promote peak performance. In iron piping systems for example, when moisture is present, rust can develop which can reduce the performance of end use compressed air operated devices like air tools or cause issues on the exhaust side as you could exhaust unwanted mist onto a surface, like in a painting operation.

Example of a desiccant dryer

Typically, an efficient and properly installed industrial compressed air system will include some type of dryer to remove any moisture that may be present in the supply.

Let’s take a look at the various types of dryers available.

Refrigerant and desiccant dryers are two of the more commonly used types of dryers.

Refrigerant based systems have several stages. The compressed air first passes through an air to air heat exchanger  which initially cools the air. The air is then delivered to an air to refrigerant exchanger where an external source of liquid refrigerant further cools the air and sends it to a separator, where the water vapors condensate and are removed through a drain trap. Now that the air is dry, it is then cycled back to the air to air exchanger where it is heated back to ambient temperature and exits the system.

Desiccant dryers typically incorporate 2 tanks containing a porous desiccant which causes the moisture to sort of “cling” to the surface. In these systems, compressed air flows through one tank, while, using it’s own regeneration cycle, heated or unheated air is blown through the desiccant in the other tank to remove the moisture and dry the air.

Membrane Dryers are typically used at the end use product. These types of systems utilize membranes to dissipate water vapor as it passes through the material, while allowing a small amount of the dry air to travel the length of the membrane to sort of “wipe” the condensate and remove it from the system.

Deliquescent Dryers use a drying agent which absorbs any moisture in the air. As the vapors react with the desiccant, like salt, the desiccant liquefies and is able to be drained at the bottom of a tank. These are the least expensive dryers to purchase and maintain because they have no moving parts and require no power to run.

When a dryer is being considered for a particular setup, there are 3 common reference points used when determining the dryers rating – an inlet air temperature of 100°F, supply pressure of 100 PSIG and an ambient air temperature of 100°F. Changes in supply pressure or temperature could change the performance of a particular dryer. You want to follow the manufacturer’s recommendations when dealing with variances as they will typically provide some type of conversion.

For help with this or any other topics relating to the efficient use of compressed air, please give us a call, we’d be happy to help.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

 

Heated Desiccant Dryers image courtesy of Compressor1 via creative commons license

Contaminated Air Supply Leads To Unwanted Results

IMG_5570
Rust from the air supply found inside a compressed a Reversible Drum Vac.

One of the greatest attributes of EXAIR products is their ability to stay in operation for years on end without any maintenance.  With no moving parts to wear out, there really is little-to-no upkeep required.  So, when we receive notice from a customer that an EXAIR product is not working properly, we most always seek to establish the pressure, volume, and quality of the compressed air supply.  By examining these three variables, we can usually pinpoint the source of the performance discrepancy.

I had an exercise in this routine a few days ago with a Reversible Drum Vac (RDV).  The RDV had arrived at EXAIR after the customer noticed a drop in performance.  The RDV went from operating normally to gradually loosing strong vacuum when vacuuming liquids out of a coolant sump.

The end user and I discussed the air supply pressure, line size, and available volume of compressed air to operate the RDV which all seemed to be in order.  Compressed air supply pressure was 80 PSIG, they were using the EXAIR supplied (properly sized for the product) compressed air hose, and the unit had functioned in this exact setup for some time, so we were confident in the ability of the compressed air system to supply adequate volume.

In most cases, when an RDV gradually loses vacuum, or experiences a change in performance without a change in application parameters, contaminants from the compressed air system can be found inside of the RDV.  And, that is exactly what happened here.

IMG_5565
Reversible Drum Vac “plug” – notice the rust on the everything below the O-ring (everything in contact with the compressed air supply)

I first tested the RDV for vacuum level and flow, both of which were low.  When I disassembled the RDV I noticed what looked like rust on all surfaces which are in contact with the compressed air stream (photo above).

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Internals of the Reversible Drum Vac “body”; littered with rust

Then, I peered into the body of the drum vac and saw the root of the problem – dirt and rust from the compressed air system had accumulated within the RDV, restricting compressed air flow and causing the decay in performance.

IMG_5568
Rust and shim as they were dumped out of the Reversible Drum Vac body
IMG_5569
Another photo of the rust

After a quick cleaning of the RDV, performance was perfect and the RDV was ready to go back into operation.  The end user and I discussed my findings along with proper air filtration to prevent a similar occurrence in the future.  They were glad to know their RDV was in working order, and we were both glad to confirm the root cause.  With a new filter separator installed at the compressed air line feeding this RDV, trouble-free and maintenance-free performance can be expected for a long time to come.

If you have a similar application need, or think an EXAIR solution may benefit your process, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Vacuuming Fe2O3 with an EXAIR Heavy Duty HEPA Vac System

In late Fall of 2013 I traveled to Mexico to meet with our Central and South American distributors.  We spent several days together, discussing products, applications, varying business climates in differing countries, marketing, selling, and a variety of other topics.  It was great to meet face-to-face, and after returning to the States, it’s been a pleasure to see these distributors work through applications and solve problems for their customers using EXAIR products.  The problems solved with our products range from blow-off and cooling needs, to scrap removal and vacuuming.

The photos below, taken by our distributor in Colombia, show Ferric Oxide (Fe₂O₃), a fairly benign form of rust, accumulating around large wire spools.  These spools are stored outside, and the rust is not detrimental to any processes, per se, but the accumulation around the spools is problematic.  The end user needed a way to vacuum the debris that was not only effective, but reliable for long-term use – the electrically driven vacuums they had been using on-site were failing after a short time.

steel dust vacuum 1
Large flakes which need to be vacuumed
steel dust vacuum 3
Steel fines which need to be vacuumed
steel dust vacuum 2
Problematic area of this application

As I discussed the application with our distributor, we went over the variables which would ultimately determine the correct system and model number.  The larger, more flakey material (shown in the first photo above) is suitable for use with a Chip Vac, Heavy Duty Dry Vac, or Heavy Duty HEPA Vac system.  But, the second photo showing the finer steel dust led us to refine this list to only the Heavy Duty HEPA Vac.

The reason for omitting our other vacuum systems and focusing solely on the HEPA unit, was the potential for airborne dust and a desire to offer the end user a removable and cleanable component to the vacuum system.

The HEPA filter of our Heavy Duty HEPA Vac system will filter the incoming material to 0.3 micron level with a 99.97% efficiency rate.  Filtration at this level is suitable for small particles such as the steel dust in this application.  And, the Heavy Duty HEPA Vac system uses a serviceable pre-filter which can be cleaned and reused as necessary.

These features, coupled with the longevity found in our vacuum systems (no moving parts = no wear points or components to break down over time), provided an excellent solution for this customer.

If you have an application in need of a compressed air based solution, give us a call.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE