Should You Consider Rotary Screw Air Compressors For Your Process?

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

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

Supply Side Review: Heat of Compression-Type Dryers

The supply side of a compressed air system has many critical parts that factor in to how well the system operates and how easily it can be maintained.   Dryers for the compressed air play a key role within the supply side are available in many form factors and fitments.  Today we will discuss heat of compression-type dryers.

Heat of compression-type dryer- Twin Tower Version

Heat of compression-type dryers are a regenerative desiccant dryer that take the heat from the act of compression to regenerate the desiccant.  By using this cycle they are grouped as a heat reactivated dryer rather than membrane technology, deliquescent type, or refrigerant type dryers.   They are also manufactured into two separate types.

The single vessel-type heat of compression-type dryer offers a no cycling action in order to provide continuous drying of throughput air.  The drying process is performed within a single pressure vessel with a rotating desiccant drum.  The vessel is divided into two air streams, one is a portion of air taken straight off the hot air exhaust from the air compressor which is used to provide the heat to dry the desiccant. The second air stream is the remainder of the air compressor output after it has been processed through the after-cooler. This same air stream passes through the drying section within the rotating desiccant drum where the air is then dried.  The hot air stream that was used for regeneration passes through a cooler just before it gets reintroduced to the main air stream all before entering the desiccant bed.  The air exits from the desiccant bed and is passed on to the next point in the supply side before distribution to the demand side of the system.

The  twin tower heat of compression-type dryer operates on the same theory and has a slightly different process.  This system divides the air process into two separate towers.  There is a saturated tower (vessel) that holds all of the desiccant.  This desiccant is regenerated by all of the hot air leaving the compressor discharge.  The total flow of compressed air then flows through an after-cooler before entering the second tower (vessel) which dries the air and then passes the air flow to the next stage within the supply side to then be distributed to the demand side of the system.

The heat of compression-type dryers do require a large amount of heat and escalated temperatures in order to successfully perform the regeneration of the desiccant.  Due to this they are mainly observed being used on systems which are based on a lubricant-free rotary screw compressor or a centrifugal compressor.

No matter the type of dryer your system has in place, EXAIR still recommends to place a redundant point of use filter on the demand side of the system.  This helps to reduce contamination from piping, collection during dryer down time, and acts as a fail safe to protect your process.  If you would like to discuss supply side or demand side factors of your compressed air system please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Heat of compression image: Compressed Air Challenge: Drive down your energy costs with heat of compression recovery: https://www.plantservices.com/articles/2013/03-heat-of-compression-recovery/