The Northey Advantage

The following briefly demonstrates the whole life cost savings of a Northey Oil-free machine in the utilities market, using information gathered by one of our customers who wished to reduce their man hours involvement with regards to servicing and regular maintenance.


Oil Free

  • Oil free working environment
  • No contamination of process gas from lubricating oil
  • Non contact rotors – no wear or contamination of process gas
  • Minimal maintenance requirements
  • No on-going oil costs
  • Less site personnel involvement
  • No need for sump tank
  • No requirement for oil separators in the discharge line
  • No requirement for environmental disposal of waste oil
  • Auto drain capability
  • Robust build and design – Wet and dirty gas is not a problem
  • Clean working area
Oil lubricated

  • Potential Health and Safety and Environmental issues arising from oil spillage and trip/slip hazards
  • High Risk of foaming from oil contamination
  • High Maintenance to check and replenish oil tanks
  • High and continuous oil costs
  • High service intervals to replace vanes
  • Oil separators and recovery vessels required
  • High risk of ground contamination
  • Strict environmental controls for disposal of waste oil



The Working Principle

Northey compressors and vacuum pumps are purely rotary machines, yet they possess the positive action of the piston type due to the unique principles of design and operation, and must not be confused with either reciprocating or other rotary machines.

Pistons, piston rings, connecting rods, sliding vanes, eccentric drums, valves and other often troublesome components producing friction, vibration, noise, inertia forces, and wear have been eliminated.

The diagrams clearly illustrate the cycle, and it should be noted that during the transition from position 4 to position 1, when the rotors “mesh”, the ports are closed, and the whole of the working chamber is at uniform pressure.

There is therefore no need to maintain a “seal” between the rotors. Clearances are accordingly provided here, so that the rotors cannot touch and wear each other.

 Working Principle



(a) Commencement of Cycle. Inlet port about to open into induction space I (a) Induction well advanced in space I
(b) Compression commencing into space C (b) Delivery commencing from space C




(a) Induction complete. Inlet port shut off from space 1 (a) “Change over” position. Seal broken between rotors, freeing undelivered air into induced charge
(b) Delivery complete. Small portion of compressed charge trapped in space C (b) Cycle recommences at (1), with induced charge now transferred to “compression side” of rotor tips