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Air Compressor Basics

by Nick Calvo on May 03, 2020

The Basics of Air Compressors

Depending on what air is used for will determine the type of air compressor that is best matched for the task. There are several different uses for compressed air. Most common are to operate handheld pneumatic tools such as grinders, impact wrenches, or nail guns. Other applications require air to act as hydraulics like to move parts of equipment or an assembly line. Direct uses of air include blowing down tanks for cleaning or filling things like tires. Some applications have a much greater demand of air, for example, using compressed air for paint spraying, sand blasting, or blow-off cleaning.

Choose the right equipment for your application.

Reciprocating Air Compressor

Reciprocating or Piston-Type

Reciprocating or Piston-Type compressors pump air by action of pistons. Drawing in air on the down stroke and discharging air on its upstroke. Reciprocating compressors can be single-stage or two-stage, while two-stages of compression creates greater efficiency. These compressors are designed to run for a period, and then have down time to cool.

Rotary Screw

Rotary Screw uses two helical screws that rotate with close clearances next to each other. Air travels through the grooves and is compressed as the channels volume decreases, which increases pressure. Rotary compressors have fewer moving parts and excellent cooling capabilities, meaning they can run 100% of the time without needing down time to cool. Oil is used to cool, lubricate, and seal the screws – which must be separated from the air after the compression cycle.

Rotary Vane

Rotary Vane compressors use an electrically spun rotor with slots to guide air into a discharge chamber, discharging a fixed volume of air at a higher pressure. Oil is used to cool, lubricate, and seal the bearings and vane – which must be separated from the air after the compression cycle.

Centrifugal

Centrifugal compressors use high speed impellers to rotate at up to 60,000 rpm and accelerate the air, causing an increase in pressure. Centrifugal compressors are not positive displacement, but rather dynamic compression. Between stages, intercoolers cool the air and drain condensate to minimize impeller damage.


Reciprocating Rotary Screw Rotary Vane Centrifugal
Advantages
  • Simple design
  • Two - stage more efficient
  • Low initial cost
  • Excellent cooling capabilities
  • Quiet Operation
  • Designed to run 100% of the time
  • Simple design
  • Few moving parts
  • Low maintenance cost
  • High efficiency
  • Cost effective for larger size
  • Higher pressures
Disadvantages
  • Loud operation
  • Heat from friction requires down time to cool
  • Higher maintenance cost
  • Not designed to run 100% of the time
  • High rotational speeds
  • Oil injected - oil carryover
  • Difficulty in dirty environments
  • Oil injected - oil carryover
  • Oil - free not avaliable
  • Difficulty with pressure over 200 psi
  • High initial cost
  • High rotational speeds
  • Complicated control systems

1 comment
by Patrick M. on July 27, 2020

I’ve always had a recip at my shop, but the more and more I look at them, I may just have to check into getting a rotary screw!

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