Design concept of Howden Screw Compressors

Compression is achieved by the intermeshing of two helical rotors contained in a suitable casing. Figures 1–4 give details of the compression cycle.

The Howden twin screw compressor is a positive displacement rotary design. As such it has the characteristics and stability of reciprocating compressors but in addition offers particular advantages:

  • Reduced physical size.
  • Fewer moving parts.
  • Low vibration.
  • Extended operating life cycle.


Figure 1

Fig 1

Gas is drawn in to fill the interlobe space between adjacent lobes

Figure 2

Fig 2

As the rotors mesh, the gas is trapped between the rotors and the casing.

Figure 3

Fig 3

Continued rotation progressively reduces the space occupied by the gas, causing compression.

Figure 4

Fig 4

Compression continues until the interlobe space becomes exposed to the outlet port, through which the gas is discharged.

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