Single Acting Reciprocating Air Compressor

With all the options when it comes to air compressors, I wanted to take a deeper diver into Single acting Reciprocating compressors and see why they are so popular across all industry.

First, What is a Single acting Reciprocating air compressor, and how does it work? A single-acting compressor is a type of air compressor that uses only one end of the piston for the suction and compression. So the first stroke of the piston sucks the air inside the compressor while the air compression occurs in the second stroke.

To explore the internals a bit closer, a mechanical linkage, or connecting rod, is attached to a piston and a crankshaft.  For every rotation of a motor, the piston will move up and down.  Air is being drawn into the cylinder and then compressed.  The volume of the cylinders, the number of cylinders, and the rotations per minute will determine the amount of compressed air that can be produced.  The advantages with reciprocating compressors are that they can produce high pressure, compress different types of gases, and have a cheap and rugged design.  The disadvantages would be high vibration and noise levels as well as being oversize as compared to capacity.  (See the photo below)

Piston goes down: air draws in. Piston goes up: air is pushed out.

Let’s expand on the advantages and disadvantages a bit to see if that explains the heavy use of this style air compressor!


  • Cost! Single acting Reciprocating air compressors just cost less than other styles of air compressors!
  • They are typically easy to maintain.
  • They work great for medium duty applications
  • They require less traveling of the compressed air.


  • The piston only works in one direction at a time
  • The piston spring takes up space limiting the cylinders working stroke.
  • They are less efficient than centrifugal type compressors

No matter the type of air compressor that you use, they are very expensive to use.  Air compressors are considered to be the fourth utility within a manufacturing plant.  To help use it efficiently and safely, EXAIR offers a range of products to clean, cool, blow, clean, conserve, and convey.  This would include our Super Air Knives, Super Air Nozzles, Safety Air Guns, Cabinet Coolers, and much more.  If you want to save energy, increase safety, and cut overhead costs, you can contact an Application Engineer at EXAIR.  We will be happy to help. 

Jordan Shouse
Application Engineer

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Compressor internals image courtesy of h080Creative Commons License.

Understanding Deliquescent Dryers

Deliquescent Dryer

Deliquescent dryers can sometimes be confusing. Some compressed air dryer vendors use the terms deliquescent and desiccant synonomously as if they were interchangeable in describing their equipment. The deliquescent dryers are not a complex drying system and found most commonly in the petrochemical industry.

Unlike any other dryer, a deliquescent dryer is also used to reduce or remove moisture before it turns to liquid water. These dryers can be installed indoors, outdoors, offshore or any remote location. They do not require electric for operational purposes or have any moving parts, making them easy to maintain and economically more efficient. In a deliquescent dryer, moist air (gas) passes over a layer of deliquescent tablets which absorb moisture from the air. The pressure dew point lowers as the tablets slowly dissolve, the condensation falls into the drain area, and the drier air flows through the outlet into the piping system.

The best deliquescent materials are salts with a strong attraction for moisture. Deliquescent desiccants (drying tablets) are formulated from calcium chloride, magnesium chloride, potassium chloride and lithium chloride. Not all deliquescent desiccants are equal. The final formulation and properties of the desiccant can have significant impact on the design of a dryer tank. That is, the surface of the desiccant chemical, often beads or pellets, will liquefy, and the resulting liquid will flow to the bottom of the vessel. There is either a drain (manual or auto) at the base of the deliquescent dryer which is used to expel the collected fluid.

Some factors that will affect the consumption of the desiccant are the type of adsorbent, type of adsorbate, the size of the adsorbent bead or pellet, the concentration of the adsorbate in the compressed air stream, and the temperature of that air stream.

You will want to have a water trap, also known as a general purpose compressed air filter plumbed in line just upstream from the deliquescent dryer. Otherwise, any liquid water flowing with the compressed air into the air dryer will make short work of the desiccant chemical, requiring a more frequent – and expensive – recharge.

The compressing of air generates heat. That hot, moist compressed air will consume the desiccant chemical in the deliquescent dryer much more quickly. Best practice is to ensure the air flow to the dryer is as cool as possible with, if possible, a long air line and a dwell tank prior to the deliquescent dryer to allow the air to cool and have water saturate out naturally.

A deliquescent dryer can be expected to reduce the compressed air dew point by 20 – 30 deg. F, or so. The degree of drying depends how saturated the airflow is going in and on the type of deliquescent chemical used.

Unlike other forms of compressed air dryers, a deliquescent unit doesn’t guarantee the air will reach a certain dew point. The amount of water vapor in the air that exits the dryer is completely predicated on how much water vapor is in the air going into the dryer.

I hope this helps increase your understanding of deliquescent dryers. EXAIR has many Intelligent Compressed Air tools and accessories. We would love to help you learn more about our products. Please contact us as we are eager to help.

Eric Kuhnash
Application Engineer
Twitter: Twitter: @EXAIR_EK

Porous and Non-Porous E-vac Generators

Having an injection molding background I saw many uses for parts pickers using many different sizes from 90 – to 3000 ton injection molding machines and a vast amount of part sizes and shapes that varied from items as small as dinner plates to as big as municipal refuse containers. I dealt mainly with non-porous applications but EXAIR offers both porous and non-porous E-vacs to accommodate wide range of part sizes and weights.

EXAIR has High Vacuum Generators for Non-Porous Applications with high vacuum units up to 27″ Hg (91 kPa) with vacuum flows up to 15.8 SCFM (447 SLPM). The plastic products I was moving were all non-porous, meaning air or liquids would not permeate into the surface of my product. Other examples of non-porous material including plastic sub-straights include glass, steel sheet, ceramics, vinyl, sealed tiles and varnished wood.

Porous applications use a low vacuum generator. Low vacuum units up to 21″Hg (71kPa) with flows up to 18.5 SCFM (524 SLPM) are typically used for porous materials such as corrugate, wood, fabrics, cinder block, etc… The relatively lower level vacuum for porous materials prevents warping, marring, dimpling or disfiguring of the surface due to excessive vacuum. This style generates more vacuum flow to overcome porosity and leakage while maintaining control over the object being handled.

Referencing the previously mentioned refuse container application, I performed the weight and movement analysis and determined that four of our model 900754 vacuum cups and two of our model 810006M Non-porous E-vacs would have been more than adequate to unload and lift my 95 gallon refuse container lids from the injection molding machine and move them to the hot stamp center. I recall the vacuum cup system we had in place back then, would frequently drop out and lose control over the product. This was not only a real process headache, but also made for a legitimate safety issue as well.

EXAIR E-vacs actually have other interesting uses. They have been used in applications for bag and package opening, label placement, vacuum forming, leak testing and many other applications.

EXAIR also has accessories to round out vacuum cup systems including vacuum cups themselves, mufflers, check valves, vacuum tubing and fittings. We would have interest to discuss your application. If you have questions regarding which E-vac style and size is proper for your project please contact any of our Application Engineers to help you with selection and design of your system.

Eric Kuhnash
Application Engineer
Twitter: Twitter: @EXAIR_EK

EXAIR’s Safety Air Guns are the Ergonomic Answer

In addition to a variety of engineered Air Nozzles, you can customize your EXAIR Safety Air Gun with Chip Shields, Extensions, Stay Set Hoses, etc., to meet the particular needs of a specific application.

EXAIR has a nice selection of Safety Air Guns. The VariBlast Precision and Compact, Soft Grip, Heavy Duty and Super Blast Safety Air Guns are available with a variety of air nozzles, chip shields and pipe extensions. They are durable and comfortable and ergonomic to use.

These Safety Air Guns are designed with durability and comfort in mind while also ergonomically safe to use. Safe operation is assured along with low air consumption and noise levels.

EXAIR Engineered air nozzles are available in Type 316 stainless steel for superior corrosion resistance and mechanical wear, Type 303 stainless steel for corrosion resistance, PEEK thermoplastic for non-marring and chemical resistance or zinc/aluminum alloy for general purpose applications.

Flying Debris? – Chip Shields are durable polycarbonate shields that protect the operator from risk of flying debris often seen when blowing off chips from machined parts. They are also useful to prevent coolant from splashing back, creating a mess during drying processes.

The Chip Shields are available for EXAIR’s VariBlast, Soft Grip and Heavy Duty Safety Air Guns. The Chip Shield can be used on Safety Air Guns with or without an aluminum extension. They may be purchased as part of a new air gun system, or retrofitted as a Chip Shield Kit.  Consult an Application Engineer for selection assistance.

If you have a blow-off process where the air is to be directed at a distance away from the operator, or into a hard to reach location an extension is the solution. Available in lengths from 6″ (152mm) to 72″ (1829mm), with sizes as to meet most requirement can be found. To add an extension to an air gun, simply add -xx to the current part number..

EXAIR’s Stay Set Hoses are available from 6”-36” in lengths with ¼ NPT male threads on each end, or a ¼ NPT male on one end and 1/8 NPT female on the other. The Stay Set Hoses are rigid and allow you to maintain precise positioning of the blow off nozzle. The hoses have “memory” and will not creep or bend.

 If you need a 12′ coiled air hose, to use with your Safety Air Gun, we have them available and in stock. Available with 1/8 NPT, 1/4 NPT or 3/8 NPT male end swivel connections. Avoid tangled and messy air lines and keep things neat!

If you have ab application and need help deciding which EXAIR Safety Air Gun and/Nozzle you need. Please contact us and ask for any Application Engineer. We are always happy and eager to help.

Eric Kuhnash
Application Engineer
Twitter: Twitter: @EXAIR_EK