Clearance Management Screw Compressor

Oil-free twin screw compressor Clearance management whitepaper


This paper describes the theory behind oil-free compressor operations, clearances and conventional methods of clearance management. It details the improved clearance management methods that have been developed and integrated into Howden’s current oil-free screw compressor range. Furthermore, this paper will explain the key benefits that customers will gain from these methods.

In the whitepaper you will learn about:

  • Twin screw compressor operation
  • Leakage paths
  • Manufacture and assembly tolerances
  • Bearing clearance
  • Thermal distortion
  • Pressure distortion
  • Rotordynamics
  • Impact of clearances
  • Conventional clearance management methods
  • Howden’s improved clearance management methods
  • Customer benefits




When handing hazardous or corrosive gases, gases with high levels of liquid, dirt or particulates, or when contamination of the gas being processed is an issue, the use of oil-free twin screw compressors is often the best approach.

Howden's oil-free twin screw compressor range is involved in a wide range of industries and processes, such as: Chemical, Foundry, Mining, Oil & Gas, Petrochemical, Power Generation, Refinery.

Download the whitepaper and in Appendix 1 you will find more detailed information on the fields of application where oil-free compressors are used. In these industries, Howden are experienced in compressing a high diversity of different gases of varying molecular weights, including polymer forming and unpredictable gases. Appendix 2 lists multiple project references where oil-free compressors have been installed.

Oil-injected twin screw compressors operate with oil injection into the rotor chamber, which is used for cooling, sealing of the clearance gaps and lubrication of the rotors – in which, the directly driven male rotor drives the female rotor using the injected oil as a hydrodynamic film to maintain efficiency and prevent wear.

Oil-free screw twin compressors are designed to operate using a timing gear setup to synchronise the rotors and therefore negate the need for oil injection. Although this allows the handling of gases possible in an oil-injected compressor, it adds a more complex challenge in the clearance management process during the design stage.

This is due to the higher temperatures experienced within the compressor and the lack of clearance gap sealing via injected oil. The image above on this page shows a dissected view of a Howden oil-free screw compressor.

This paper will demonstrate that, although complex, the management of these critical clearances has been achieved in the Howden oil-free screw compressor range. This has been realised through extensive research and development, and has been successfully applied into the current screw compressor range.


Oil-free twin Screw Compressor: Clearance management

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