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


Heated Desiccant Dryers image courtesy of Compressor1 via creative commons license

Static Problem in Plastic Tube Manufacturing is Solved

A common question that we get about Static Eliminators is “Where is the best place to install them within our process?” While there is a definite strategy to mount the Static Eliminator at the last possible point before the application problem occurs, in some instances, you still may have to use more than one Static Eliminator in different locations.

A customer was working with plastic tubes for packaging that were roughly 1” (25mm) in diameter by 6” (152mm) long. At the beginning of the process, an operator would remove the plastic tubes from boxes and manually stack them in a hopper.  They had a model 111012 Super Ion Air Knife mounted at the top of the hopper blowing down on the tubes.  This helped to remove the “shock” hazard that previously existed in loading the hopper.  To continue with the process from the hopper, the tubes are moved into an elevator and raised up to a feed chute in single file.  They would roll down a feed chute before they would be dropped onto a conveyor belt.  Just as the plastic tube would drop, static created from friction generated by the rolling action would cause one side of the plastic tube to “stick” to the prior tube, causing a jam in the system.

Jamming Area of Plastic Tubes
Jamming Area of Plastic Tubes

The customer was looking for a solution to stop the jamming. He had already mentioned that he was using the model 111012 Super Ion Air Knife at the hopper and wondered if it was working properly.  A quick question quickly verified its operation.  I asked if the operators were getting shocked from loading the plastic tubes into the hopper.  He stated that they were not.  So, the Super Ion Air Knife was removing the static charges as intended to keep the operators safe. The customer also sent pictures of the operation so I could better understand his process.  From the photos, the plastic tubes were right up against each other lengthwise in the chute.

Static charges were re-generating through the movement of the parts going through the loading elevator, moving up to the feed chute, and sliding down to the conveyor; the plastic tubes were rubbing and rolling against each other.  As with any non-conductive materials that are rubbed, slide against one another, or peeled, static electricity has a very good possibility to be generated or re-generated as in this case.  Even though the static was being removed at the hopper, the friction between the plastic tubes caused the static to regenerate.

Since static was affecting the feed of plastic tubes onto the conveyor, we needed to re-focus our attention in this area. The problem area in this application has now become the feed chute. After talking things over with the customer, model 111006 Super Ion Air Knife  was mounted above the end of the feed chute to provide an ionized airflow.  It would be facing the length of the plastic tube and angled upward along the incline of the chute, setting up a good counter flow between the parts and the ionized air.  Because static is a surface phenomenon, the ions have to hit the exposed surfaces to neutralize the charge. This arrangement would blanket the top surfaces of all the plastic tubes in the feed chute with ions as they roll by, neutralizing the charges before they became a problem at the end of the chute.

Super Ion Air Knife
Super Ion Air Knife

This is only one example of EXAIR Static Eliminators reducing a static charge in packaging applications. The product works well at eliminating the jamming, feeding, tearing, discharges to operators and other similar problems encountered within the packaging environment. Do you have a similar feeding application that you feel could use some help from static elimination?  If so, we’d love to hear from you. Contact us with your application questions today!

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