Intelligent Compressed Air: Double-Acting Reciprocating Compressor

Evaluating all of the different types of compressors and which is right for you can seem like a daunting task. Today, I’d like to take some time to talk about the Double-Acting Reciprocating type of air compressor.

double acting compressor
Cut-out of a double-acting reciprocating compressor

Double-Acting Reciprocating compressors are a subset of the larger family of positive displacement compressor types. In positive displacement compressors, air is drawn into a chamber where the volume is then mechanically reduced. The energy used to displace the air volume is converted to an increase in air pressure. Dynamic compressors operate a little differently. They utilize an increase in air velocity to create the change in pressure. Air is accelerated to a high velocity through an impeller. The kinetic energy of the air is converted to an increase in potential (pressure) energy.

The Double-Acting Reciprocating compressor is a close relative to the Single-Acting Reciprocating compressor. In these types of compressors, an “automotive-type” piston driven by a crankshaft provides the compression. In a Double-Acting Reciprocating compressor, air is compressed as the piston moves in each direction. Hence the name, “double-acting”. In a Single-Acting Reciprocating compressor, air is only compressed on each full revolution of the piston. This makes the Double-Acting Reciprocating compressor much more efficient than its brethren.

Double Acting Recip
Double Acting Reciprocating Air Compressor

Double-Acting Reciprocating compressors are also available in much larger sizes. While Single-Acting compressors can be found up to 150HP, generally they’re much less common any larger than 25HP. Whereas a Double-Acting compressor is available from 10HP-1,000HP, making it a better choice for larger plants that require a significantly greater volume of compressed air. While they’re a bit more expensive due to the added mechanisms to produce the double-action compression, this cost is quickly offset by the increase in efficiency. At a performance of 15-16 kW/100 cfm, they’re 32% more efficient than a single-acting reciprocating compressor.

If you’re in the market for a new compressor and are struggling to determine the most suitable compressor, talk with your local compressor sales representative. Once you’re up an running, EXAIR has a wide-range of products that’ll make sure you’re using your compressed air safely and efficiently!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD
Image courtesy of Best Practices for Compressed Air Systems – second edition

 

About Single Acting Reciprocating Compressors

Whether you’re new to the field of compressed air, an experienced technician, or just in the market for a new compressor, you may find yourself coming into contact with various compressor types.  Within the world of compressed air supply there are two types of compressors: positive displacement and dynamic.  These two compressor types branch off into several different variations, as shown in the chart below.

Compressor types

Positive displacement compressors increase air pressure by reducing air volume within a confined space.  In a positive displacement compressor mechanical linkage is used to reduce the volume of air (the fluid), which results in a change to the air pressure.  To think of it another way, the energy which is used to displace the air volume is converted into an increase in air pressure.

Dynamic compressors, on the other hand, utilize an increase in air velocity to cause a change in air pressure.  For a dynamic compressor, the fluid (air) is accelerated to a high velocity through a rotor or impeller.  The kinetic energy of the air is then converted to an increased potential energy/static pressure by slowing the flow through a diffuser.  The air at the outlet of the diffuser is the compressed air which is used to perform work.

The internals of a single acting reciprocating compressor.

Within this vast field of compressed air generation, one of the most common types of compressors is the single acting reciprocating compressor.  The term “single acting” refers to manner in which the cylinder inside of the compressor motor interacts with the working fluid (the air).  When the fluid (air) acts only on one side of the piston, the motor is referred to as “single acting”.  This type of motor relies on the load of the motor, a flywheel, springs, other cylinders, or some other device/momentum to return the piston back to its original location.

Single acting compressors can be air-cooled or water cooled, lubricated or non-lubricated, and packaged to provide a wide range of pressure and flow capacities.  Because of this adaptability, single acting compressors are quite common and serve a variety of industrial needs.

No matter the type of compressor on the system’s supply side, having engineered products on the demand side improves overall system performance and efficiency.  If you’d like to discuss engineered solutions for your compressed air system, EXAIR Application Engineers are ready and waiting.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

 

Compressor internals image courtesy of h080, Creative Commons License.