Tag: rotary compressor

Should You Consider Rotary Screw Air Compressors For Your Process?

Published on by jasonkirbyLeave a comment
Rotary Screw

Rotary screw compressors are efficient, positive-displacement machines specifically engineered for continuous industrial air supply. Utilizing two interlocking helical rotors, these compressors provide a 100% duty cycle, operate quietly, and require less maintenance than traditional piston compressors. They are particularly well-suited for high-demand environments such as manufacturing and construction.

Rotary air compressors are positive displacement devices engineered for continuous, high-capacity industrial applications, employing rotational motion to capture and compress air. The primary types include rotary screw, sliding vane, scroll, root blower, and liquid ring compressors. These machines are categorized based on their cooling methods, which can be either air-cooled or water-cooled, as well as their efficiency control mechanisms.

Rotary screw compressors, characterized by their two interlocking helical rotors, are the most prevalent type used in various industrial settings. These compressors effectively trap and compress air, making them highly efficient for continuous operation. Their robust design ensures exceptional durability, which is essential for meeting the demands of industrial applications.

Sliding vane compressors operate by utilizing a rotor equipped with several sliding vanes that extend radially. This design facilitates the formation of air pockets between the rotor and the housing, which effectively reduces the volume of air and simultaneously increases its pressure.

Scroll compressors utilize two interleaved spiral scrolls—one stationary and the other orbiting—to compress air without any rotational movement. This design is particularly suited for smaller applications where quiet operation and energy efficiency are essential.

Lobe compressors operate by utilizing two precisely matched lobes to move air from the intake to the discharge port. This mechanism ensures a steady and continuous flow of low-pressure air (4.4 to 14.5 psig).

Liquid ring compressors are a specialized rotary compressor that utilizes a liquid, typically water, as the sealing medium to compress gas. This design is particularly advantageous in applications where it is essential to avoid oil contamination in the process.

Advantages: Rotary compressors, especially screw models, are known for their exceptional energy efficiency, achieving savings of up to 60%. They are designed for continuous operation around the clock, which makes them suitable for demanding industrial, HVAC, and refrigeration applications. With fewer moving parts, these compressors require minimal maintenance and operate quietly with low vibration levels. This combination ensures a consistent and reliable airflow while minimizing oil carryover, making them an excellent choice for environments that prioritize efficiency and performance.

Disadvantages: Rotary compressors, especially the rotary screw variety, entail significant upfront costs and require specialized maintenance. Their efficiency tends to decrease during periods of low air demand, which can result in condensation if the units do not operate at sufficiently high temperatures. Although these compressors are engineered for continuous use, they can incur substantial repair expenses in the event of a failure, particularly due to the high costs associated with air end replacements.

If you have questions about the rotary compressors, or anything regarding EXAIR and our products, please do not hesitate to reach out.

Jason Kirby
Application Engineer
Email: jasonkirby@exair.com
Twitter: @EXAIR_jk

Air Compressors: Rotary Type

Published on by John BallLeave a comment

What is an air compressor? In simple terms, it is a machine that increases fluid pressure.  It works by either changing the volume of air, positive displacement, or by changing the velocity of the air dynamics.  Many industries use air compressors to operate pneumatic equipment.  In this blog, I wish to cover the Rotary Compressor.

The Rotary Screw Compressor is a very common type of air compressor. This compressor uses dual rotors with meshing lobes that trap air while rotating. The rotation continues to push air toward a discharge port while decreasing the space the air takes up, thus increasing pressure. The rotary type of air compressor has five different sub-categories, reference image above.  This style of air compressor has some clear advantages and disadvantages:

Advantages:

  • Quiet Operations
  • Durability and Low Maintenance
  • High Efficiency
  • Continuous duty Cycle

Disadvantages:

  • High initial cost
  • Specialized maintenance

No matter the type of air compressor you use, they are very costly to operate.  To help you use them efficiently and safely, EXAIR offers a range of products that can clean, cool, blow, 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 costs no matter what size air compressor you have, you can contact an Application Engineer at EXAIR.  We will be happy to help. 

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

Images Courtesy of the Compressed Air Challenge

Air Compressors: Rotary Scroll type

Published on by John BallLeave a comment

My colleague, Eric Kuhnash, wrote a blog “About Rotary Screw Air Compressors”, and I wanted to expand that conversation to a close cousin; Rotary Scroll type Air Compressors.  As you see in the chart below, this type of compressor falls within the same family as positive displacement compressors.

Positive displacement air compressors raise air pressure by reducing the volume of air within a confined space.  The scroll compressors use two intermeshing scrolls, where one scroll is moving and the other scroll is stationary (reference photo below).  Ambient air will get trapped at the inlet side, and as the orbiting scroll moves, the spiral volume gets smaller and smaller.  When volume decreases, the pressure will increase.  The Rotary Scroll type of air compressors is less common in the rotary family, as they are limited in capacity.    

What they lose in capacity, they make up for in simplicity.  They are compact and can fit into small areas.  They require very little maintenance; and the majority of them are oil-free.  They were initially used in refrigeration systems because they were compact, inexpensive, and required little maintenance.  Since they are quiet and oil-free, they work great in doctor’s offices and medical fields. 

No matter the type of air compressor that you use, they are very costly to operate.  To help you use them efficiently and safely, EXAIR offers a range of products that can clean, cool, blow, 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 costs no matter what size air compressor you have; you can contact an Application Engineer at EXAIR.  We will be happy to help. 

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

Image Courtesy of the Compressed Air Challenge

Rotary Scroll GIF:  used from  Public Domain

Intelligent Compressed Air: What You Need To Know About Rotary Scroll Compressors

Published on by Russ BowmanLeave a comment

Humans have been using compressed air for just about as long as we’ve been using fire. The discovery of fire’s usefulness likely only slightly predates the discovery that blowing air on those flames increases their size, temperature, and intensity. Technically, our respiratory systems are single-stage, diaphragm operated air compressors!

Over the ages, engineer-type humans came up with mechanical methods to perform this task, which was primarily used to stoke fires. This was critical to the development of metalworking, which was key to the Industrial Revolution, which brought on more needs for compressed air, which led to better-equipped engineer-type humans developing the modern methods by which we compress air.

One of the most recent inventions to do this is the rotary scroll compressor. Similar to other rotary type compressors, they use a rotating shaft to decrease the space occupied by a specific amount of gas. By decreasing the space occupied without letting any of that gas out, the pressure increases. The “tricky” part about rotary scroll compressors is the incredibly tight tolerances needed to make it function effectively. In fact, the first patent for one (issued in 1905) predates the machining technology needed to make one by about forty years. And it was the 1970’s before they started to be manufactured for commercial use. Here’s how they work:

Two spirals, or scrolls, are intermeshed. The rotating (black) one orbits eccentrically with the fixed one, continually decreasing the volume for the gas to flow through (from the outer left & right sides) as it is pushed to the center, where it is fully compressed according to the compressor’s rating.

Key advantages/benefits of this design are:

  • Oil free air – no metal to metal contact of the scrolls means no lubrication is needed in the airend.
  • Pulsation free delivery – since the flow from suction to discharge is one continuous motion, the outlet pressure is constant and even.
  • Quiet operation – the lack of metal to metal contact, and continuous motion eliminate the mechanical noise inherent in, for example, the reciprocating pistons and slamming check valves in a piston type compressor.
  • Low maintenance – as in most cases, less moving parts = less to maintain.
  • Wide range of duty cycle – their design makes them particularly conducive to single & two-stage units, and efficient operation with modulating variable speed drives, meaning they handle low loads just as effectively as high loads.

Some disadvantages/drawbacks are:

  • Higher price tag – the precision machine tools, and their skilled operators, are not cheap, and neither are rotary scroll compressors.
  • Size restrictions – larger rotating scrolls generate higher centrifugal force. Because the tolerances are so tight, those higher forces necessarily limit the mass of the rotary element, which limits the size, and hence, the air flow they can push out. As a result, they’re limited to the neighborhood of 100 SCFM capacity.

This combination of pros & cons makes rotary scroll compressors especially popular in the medical and laboratory settings. A supply of clean air at a constant pressure, with the ability to handle constantly changing loads matter a LOT in those settings. 100 SCFM is a LOT of air flow in most of their applications, and relatively speaking, the air compressor generally isn’t even close to the highest priced piece of equipment in such facilities.

At EXAIR Corporation, we’re committed to help you get the most out of your compressed air system. To do that, it’s important to have a better understanding of these systems, from generation to end use. If you’d like to find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook

Rotary Scroll GIF:  used from  Public Domain
Images Courtesy of  Compressor1 Creative Commons.