What Are Rotary Screw Air Compressors?

When most people think of air compressors, they picture reciprocating air compressors, also known as piston air compressors. These air compressors physically push air into a small space, using pistons, and then collect that compressed air in an air receiver tank.

Reciprocating air compressors are relatively inexpensive and have been around for decades.

By comparison, rotary screw air compressors are an innovative, compact, and powerful type of air compressor that has become more popular in recent years. They can be more expensive than traditional reciprocating models but have numerous benefits that are quickly making rotary screw air compressors the system of choice for service truck and van fleet managers around the world.

Rotary screw air compressors operate by trapping air between two meshed rotors and reducing the volume of that trapped air as it moves down through the rotors. This reduction in volume results in compressed air, which can then be used to power air tools, inflate tires, or in numerous other applications.

Oil-Injected vs. Oil-Free Rotary Screws

Rotary screw air compressors used on service trucks and vans are oil-injected, which means oil is used to lubricate and seal the rotors in the air end, and helps to cool the air compressor. This allows the rotors to create high pressures quite quickly and compress air in a single stage. The oil then gets separated out from the air before the air exits the system and is recycled back into the air end for reuse. Oil-injected rotary screws allow the compressor systems to provide high CFM and psi on a continuous basis.

Oil-free rotary screw models are used in industrial, production or medical applications when absolutely no oil can enter the airflow, like for food packaging or medical oxygen. Oil-free rotary air compressors are more expensive, as they require two stages of compression to reach the same pressures of an oil-injected rotary system.

Power Sources For Rotary Screw Air Compressors

All air compressors need a power source to run. Fortunately, mobile air compressors have several options: a separate air compressor engine, using a vehicle’s existing engine, or tapping into an auxiliary power source like a PTO or hydraulics.

The right power source depends on existing available power options and whether they will work with an air compressor to provide enough CFM and psi.

Advantages of Rotary Screw Air Compressors

Rotary screw air compressors have many benefits that make them ideal for both mobile and standalone applications. As a result, you’ll find rotary screw air compressors on vehicles and trailers, as well as in industrial, production and medical facilities, where high quality equipment is required.

The benefits of rotary screw air compressors over other compressor types typically mounted on service vehicles include:

• Continuous airflow/100% duty cycle
• Larger volume of air
• Smoother air delivery
• Higher CFM per hp
• Longer lifespan
• Better warranties
• Quieter
• Energy efficient
• Lower operating temperatures

Most people appreciate the longevity, reliability, and easy access to instant air. Because rotary screw air compressors can run continuously, there is no need to wait for an large air receiver tank to fill before you can start using the air. Those tend to be the most popular benefits of rotary screw air compressors.

Rotary screw air compressors’ lengthy lifespan is a huge advantage over reciprocating air compressors, which are jokingly referred to as “throw-away air compressors” because they are expected to fail after three to five years. Rotary screw air compressors can last four times as long with proper maintenance.

Disadvantages of Rotary Screw Air Compressors

Rotary screw air compressors have a lot of advantages, but they aren’t the right choice for everyone. Common rotary screw air compressor disadvantages are:

• Upfront cost
• Skilled maintenance required

The number one reason people choose a reciprocating air compressor over a rotary screw is the initial cost. Rotary screw air compressors sometimes cost more than reciprocating air compressors upfront, although they typically save money over the long term.

The other disadvantage to rotary screw air compressors is that they may require skilled maintenance. Every type of air compressor needs regular servicing, and oil and filter changes are straightforward. However, in the event of a complete compressor failure, rotary screw systems require a higher level of expertise due to their complex nature. Fortunately, manufacturer tech support teams can help alleviate any inconvenience.

About the Author: Melissa Vasey is a digital marketing specialist at VMAC, which designs and manufactures innovative rotary screw air compressor and multi-power systems. Visit www.vmacair.com to learn more.