Air Compressor Terminology 101

Posted on: May 28, 2014

Estimated Reading Time: 2 min(s)


Commonly used words in the compressed air world

  • Compressor – machines designed from compressing air or gas from an initial intake pressure to a higher discharge pressure
  • Vacuum Pumps – machines for compressing air or gas from an initial pressure which is below atmospheric to a final pressure which is near atmospheric
  • Intercoolers – devices for removing the heat of compression of the air or gas between consecutive stages of multistage compressors
  • Aftercoolers – devices for removing the heat of compression of the air or gas after compression is completed. They are one of the most effective means of removing moisture from compressed air
  • Load Factor – ratio of the average compressor output during period of actual use to the continuous rated output of the machine
  • Absolute Pressure – gauge pressure plus atmospheric pressure.  At sea level the gauge pressure in pounds per square inch (psi) plus 14.7 gives the absolute pressure in pounds per square inch (psia)
  • Low Pressure – Orifice Test is a method of accurately measuring the air delivered by a compressor. It is in the method recognized by ASME, ANSI (International Standards).
  • Unload (No Load) – Air compressor continues to run (usually at FULL RPM), but NO air is delivered because intake is either  “closed off” or “modified”, NOT allowing inlet air to be trapped
  • “Modulating” Unload – air compressor continues to run and air supply is matched to demand by  “partial unloading”. This is usually accomplished by a “regulator controlled floating inlet”.
  • Start-Stop Control: Air supply is matched to demand by actual starting and stopping of the unit
  • Cut-in/Cut-off Pressure – The settings on a pressure switch used to either “load or unload” the air compressor on “constant speed” application. The “cut-out” pressure is also referred to as “maximum pressure”, the point at which there is NO AIR DELIVERED. The “cut-in” pressure is also referred as “minimum pressure” – the pressure that the system is allowed to fall to before additional air volume is called for. The compressor runs at full load between cut-in and cut-out.
  • Variable Displacement Controls: Also called “Rotor Length Adjustment” in oil cooled Rotary Screw controls. Particularly efficient in holding constant speed from 60% to 100% capacity variable speed control. Below this usually goes to “blow down” and idle.
  • Rated Pressure: The operating pressure at which the air compressor’s performance (CFM and BHP – Horsepower required) is measured
  • Specific Power: Used to compare air compressor efficiency unless otherwise stated. Usually in form of BHP/100 ACFM or CFM/HP
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Author

Ashley Gates

With over 19 years of experience in the compressed air industry, Ashley Gates brings deep expertise and a passion for innovation to her role as Vice President of Marketing and Communications at Quincy Compressor. Quincy, a trusted leader since 1920, is renowned for designing and manufacturing high-performance reciprocating and rotary screw air compressors, vacuum pumps, and a full range of air treatment solutions. Ashley is proud to represent a brand built on rugged reliability and trusted by customers in the most demanding industries. Throughout her career, she has championed strategic marketing initiatives that drive growth and strengthen industry partnerships. In addition to her role at Quincy, Ashley is honored to serve as co-chairwoman of Women In Compressed Air and Vacuum. She is excited to help expand the organization’s reach, foster meaningful connections, and empower more women to thrive in the compressed air and vacuum industry.

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