Air Compressors 101

It’s important you match the right air compressor to your work needs.

By Jeremy Bailey

Air compressors are used every day on worksites in a variety of industries.

Volume and pressure are the two most important variables when selecting an air compressor. Volume is noted in terms of cubic feet per minute or cfm. Pressure is referenced in terms of pounds per square inch or psi.

For groundwater professionals drilling water wells, the depth and diameter of the hole is going to determine the size of air compressor you need.

Air Compressor Types

So, what type of compressors are out there? Once you’ve determined the volume and pressure needs of an air compressor, it’s important to consider the type of machine you need. There are three main types of air compressors used every day in a variety of trade industries, including groundwater—centrifugal, rotary screw, and reciprocating.

Centrifugal air compressors

Centrifugal air compressors are dynamic machines, meaning they deliver large volumes of air at low pressure. Centrifugal air compressors create a rise in pressure by adding velocity to a continuous flow of air through a rotating impeller at higher speeds than other types of air compressors.

Because the flow through centrifugal air compressors is continuous, they are designed for higher capacity needs than rotary screw or reciprocating styles.

Centrifugal air compressors are typically associated with turbo machinery and natural gas pipelines. They are generally not portable and may involve a high initial investment, making them incompatible for most compact equipment needs.

And so, the two most common types of air compressors for the compact equipment or tool carrier industry are rotary screw and reciprocating compressors.

Rotary screw air compressors

Rotary screw air compressors are known as positive displacement machines. This means air is forced into a chamber where the capacity is reduced to compress the air. Essentially, as airflow is forced into a smaller area, the pressure increases.

A rotary screw air compressor works by rotating two helical screws or rotors that guide air into a cavity where the volume or space decreases as the screws turn.

Reciprocating air compressors

Reciprocating air compressors are also positive displacement machines, meaning they increase air pressure by reducing volume. Reciprocating air compressors use the constant motion of pistons to force air into a chamber where it becomes compressed.

Comparing Air Compressors

Although rotary screw and reciprocating air compressors belong to the same air compressor classification, there are a number of differences between the two styles.

Usage: Rotary screw air compressors are able to provide consistent air for a sustained period of time, making them a better fit for jobsites that require constant air or run multiple shifts. Reciprocating air compressors provide intermittent air and are best suited for jobs with occasional air needs.

Reciprocating air compressors are popular for smaller shops and home uses that don’t require continuous air and may allow more than 15 minutes to pass between uses.

Noise level: Noise reduction is also a consideration when selecting the right air compressor, especially in urban areas where contractors can face fines for noise pollution. In response to this issue, most rotary screw air compressors are contained in sound-restricting enclosures that lower the operating dBA, or noise level.

While sound-restricting enclosures could be used with reciprocating air compressors, the majority remain exposed without noise-control features.

Maintenance: As with any equipment purchase or rental—big or small—the long-term cost of maintenance must be taken into account. While the cost of routine maintenance for a rotary screw air compressor will be higher than reciprocating air compressors, it is scheduled on a less frequent basis. Reciprocating air compressors are generally due for an oil change every three months, yet rotary screw air compressors usually require only one or two oil changes each year.

When compared over the long term, a reciprocating air compressor will experience greater wear and tear due to heavy vibration and open exposure, eventually requiring a major service or repair. So, while rotary screw air compressors have more maintenance points and higher initial costs, they experience much less wear, which translates to a longer machine life.

In addition to a longer lifespan, rotary screw air compressors offer a number of advantages that include consistent airflow for a sustained period of time, noise reduction features, and ease of operation. It’s these advantages and the machine’s inherent versatility that continue to drive demand for rotary air compressors in the compact equipment industry.

Telematics in Air Compressors

Like in a variety of aspects of the groundwater industry, telematics technology is being incorporated into air compressors.

With a telematics package, machine performance can be monitored remotely through customizable data feeds that can be viewed on laptops or mobile devices. Available data varies by the telematics system but ranges from general operating status to alerts and warnings, as well as service reminders.

Telematics makes it possible to know almost instantly if a machine stops operating. But perhaps more importantly, it can communicate the potential for a shutdown that can then be averted. Downtime is minimized with fast response times, and in some instances, a replacement machine may be provided to avoid downtime altogether.

Telematics data makes it possible to more effectively manage fuel services by providing an accurate status of a machine’s current fuel level. Having a precise understanding of the fuel consumption of a machine cuts the operational cost of sending a refueling truck to a machine that has not been in operation, saving time and costs.

Cost-Saving Technologies

People want machines that consume less fuel. With advances in engine technology, it is now possible for air compressor manufacturers to use an engine with a smaller footprint to generate levels of horsepower that in the past would have required a larger, less efficient engine.

Another cost-saving trend is a dual pressure/dual flow air compressor that delivers the pressure and flow options typical of two units in a single air compressor. A dual pressure/dual flow air compressor changes from a low-pressure to a high-pressure setting with a simple flip of a switch, accomplishing a wide range of applications.

In addition to the obvious cost savings of one machine versus two, the ability to switch modes instead of switching out machines also saves time and transport costs. Separate air compressors on a jobsite often leave one machine sitting idle. With a dual pressure/dual flow air compressor, you can have one compressor on site that can accomplish high- and low-pressure applications.

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With all the new technology and options designed to improve reliability and durability, the support of a trusted, knowledgeable dealer is crucial when it comes to selecting an air compressor.

A good dealer will act as a consultant throughout the sales process and provide aftermarket support. They will match the specific air compressor to your intended applications, taking into consideration appropriate innovations and features to help you reach your end goal.


Jeremy Bailey is the director of product and project management at Doosan Portable Power in Statesville, North Carolina. For more information about Doosan Portable Products, visit www.doosanportablepower.com.