Compressor types

• Single stage piston compressor

  • air compressed to required pressure in single stroke
• Single stage piston compressor

  • downward movement of piston increases volume, creating a lower pressure than that of atmosphere
  • allows air to enter cylinder through inlet valve
• Single stage piston compressor

  • At the end of the stroke, the inlet valve closes and the pressure of the air being compressed forces the outlet valve open
  • Air is discharged into a receiver tank
• Single stroke piston compressor

  • Typically used in systems which require air with a pressure range of 3-7 bar
• Two-stage piston compressor

  • Air is compressed in one cylinder before being fed into an inter-cooler
  • Air temperature is greatly reduced by inter-cooler before being fed into second cylinder
  • The final temp of air is typically around 120 Celsius
• Two-stage piston compressor

  • Can achieve delivery pressure of 700 bar
  • Can be loud and produces pulsating air
  • Requires strong foundation supports
• Rotary sliding vane compressor

  • Rotary and vanes are only moving parts
  • Air is trapped between rotor and casing and gradually compressed into a smaller space as the rotor rotates
• Rotary sliding vane compressor

  • Contains a built-in pressure ration, dependant on delivery part
• Rotary sliding vane compressor

  • Rotor is a simple cylinder, which contains longitudinal slots
  • Vanes are cut from plate material
  • 3 forms of vane available - lubricated, oil-free, and oli-floored
• Rotary sliding vane compressor

  • Lubricated type vanes can either inject an oil mist into oncoming air stream OR oil is fed from a shaft directly into cylinders
  • This helps dissipate heat from the air being compressed
• Rotary sliding vane compressor

  • Vanes are made of either steel or a synthetic fiber material
  • The synthetic fiber has a lower mass, meaning a lower centrifugal force is needed for sealing
• Rotary sliding vane compressor

  • Oil free types of compressors require self-lubricating vanes made of carbon
  • These are used for applications such as in the food industry
• Rotary sliding vane compressor

  • Have low speeds to stop centrifugal forces causing frictional failure
• Rotary sliding vane compressors


  Main advantages are:
• Rotary sliding vane compressor

  • Oil-injected, single stage compressors can operate at pressures up to 12 bar with a flow rate of 0.2-40 m^3 per minute
  • Oil free types operate at pressures up to 3.5 bar but provide lower delivery rates
• Rotary screw compressor

  • Most common type of rotary positive displacement compressor is the helical screw compressor
• Rotary screw compressor

  • Uses 2 intermeshing rotors with helical lobes
  • Space between the rotors increases as they rotate, and air is air is admitted through the inlet valve
  • The air becomes sealed in the casing when the 2 rotors pass the inlet valve
• Rotary screw compressor 


  screw compressors can be either oil-floored or oil-free
• Rotary screw compressor

  • Oil-floored types rely on substantial volumes of oil injected into the compressor space
  • This oil seals gaps between screws and casing, lubricates the drive between male and female screws and assists in the dissipation of heating during compression
• Rotary screw compressor


  These compressors offer several advantages over reciprocating compressors, including:

  • They produce pulsation free air
  • They can operate without a receiver
  • Produce minimal noise and vibration