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Screw compressors

Screw compressors are positive displacement compressors which deliver gas flows without pulsation. This simplifies the pipe work around the compressor. Screw compressors come in two forms:
 

  • a.) oil injected screw compressors where the same oil is used for the cooling, sealing and lubrication of bearings.
  • b.) screw compressors where lube oil does not contact with the compression chamber and therefore with compressed medium. These are called “dry screw” compressors.
     

Such equipment works best at low to medium discharge pressure and low to medium gas flows. Compressor stations may be equipped with either an electric motor or a gas engine which can be installed in a modular container.
 

Screw compressors have many applications from production of instrument air to booster compressors for gas turbine power units. This equipment is also used for compression of associated petroleum gas after separation, flare gas and other gases with variable gas composition.
 

Screw compressors are compact and relatively light, easy to transport to remote areas.

Principal features of screw compressor units:
Capacity, m3/h Up to 18,000
Compression ratio Up to 15
Power, kW Up to 7,500

 

Oil-injected screw compressors

In oil-injected screw compressors, the same oil is used for the lubrication of bearings, for sealing between screws and cooling of compressed medium. Such compression process is applicable only in cases where the oil content in gas or oil contamination from gas components is not critical.
 

Oil-injected screw compressors are traditionally used in refrigerating units, treated natural gas boosters and for small scale plant air stations.
 

Screw compressors with a separate lubrication system

In most compression processes the absence of gas/oil contact is vital.
 

The problem of gas/oil contact is solved by using a compressor with a separate lubrication system where oil has no contact with gas. The main design feature of the compressor’s screw block is that the rotation of the rotors is synchronized by a timing gear  which allows screws to rotate without mechanical contact during operation. That’s not require any additional lubrication for safe operation.
 

Advantages of screw compressors with a separate lubrication system

  • Liquids (cheap light oil, water) may be used for cooling. With low compression ratios where temperature at discharge does not exceed the allowable limits, the compressor may operate “dry”, without the injection of a cooling liquid.
  • Possibility of compressing untreated gases with high content of liquid or solids. The special shape of the rotors provides for protection against accumulation of scale on walls of the housing of the screw block.
  • High reliability due to quality lubrication of bearings and lack of contact between the rotors.
  • Ability to handle any media including gases with high content of H2S and other aggressive components.
  • Rotors and the housing are made of stainless steel.
  • Low operating costs.