Centrifugal Compressor Introduction

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Centrifugal machines can be single stage or multi stage. Large volumes of gas are compressed to moderate pressures in centrifugal
machines.

  1. Centrifugal compressors use a rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas.
  2. A diffuser (divergent duct) section converts the velocity energy to pressure energy.
  3. They are primarily used for continuous, stationary service in industries such as oil refineries, chemical and petrochemical plants and natural gas processing plants.
  4. Their application can be from 100 horsepower (75 kW) to thousands of horsepower.
  5. With multiple staging, they can achieve extremely high output pressures greater than 10,000 psi (69 MPa).
  6. Many large snowmaking operations (like ski resorts) use this type of compressor.
  7. They are also used in internal combustion engines as superchargers and turbochargers.
  8. Centrifugal compressors are used in small gas turbine engines or as the final compression stage of medium sized gas turbines.
  9. Sometimes the capacity of the compressors is written in NM3/hr. Here ‘N’ stands for normal temperature pressure (20°C and 1 atm ) for example 5500 NM3/hr.

Horizontal Split Case Compressors

  1. The selection of a single-stage or multistage horizontal split case compressor may depend on the design of the compressor or preference of the nozzle location to suit a particular layout.
  2. If a grade mounted compressor is planned, the side or top orientation may be selected, whereas the bottom connections are generally used for elevated compressors.
  3. During maintenance, the top half of the compressor case is removed by lifting it vertically and away from the bottom assembly.
  4. This configuration is used for chemical, petrochemical, industrial and process air, refrigeration and high-volume and low to medium pressure gas service applications.
  5. Variations of horizontal split case compressor are shown below.

Vertical Split Case Compressors

  1. Following figure shows how this application can come with top or bottom orientations on then nozzles.
  2. Layout preference dictate the selection.
  3. Removal of the rotor assembly is through the front end of the compressor, away from the driver; the compressor vendor supplies the removal distance to the play layout designer.
  4. This design is used for catalytic reforming, gas conversion and repressurizing, processing services, refrigeration and high-pressure, low volume or high volume, low pressure gas service applications.
  5. More than one compressor may be hooked in tandem.

 

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