Centrifugal Compressor Piping Layout: A brief presentation

Considerations for Centrifugal Compressor Piping Layout

This article is intended to serve as a guide in the development of equipment layout and piping layout for centrifugal compressors and their associated equipment, with the goal of producing safe, operable, economical and maintainable installations.

Compressors are machines, which are used to increase the pressure of a gas by mechanically reducing its volume within the compressor casing.

Basic type of compressors:

  • Positive Displacement Compressors
  • Reciprocating compressor
  • Screw Compressors
  • Centrifugal compressors
  • Pipeline compressors

Type of Compressor Drives:

Following are the various types of Compressor drives:

  • Electric Motor Drives
  • AC Squirrel Cage Induction Motor
  • Synchronous AC Motor
  • Gas Turbines
  • Steam Turbines
  • Variable Speed Drives
  • Variable Frequency Drive
  • Variable speed (Hydraulic Coupling) Drives

Auxiliary Equipment’s:

  • Lube Oil Cooler (Supplied by Compressor Vendor)
  • Lube Oil / Seal Oil Console (Supplied by Compressor Vendor)
  • Surface Condenser
  • Condensate Pump
  • Inlet Air Filters (Supplied by Compressor Vendor)
  • Suction Scrubber (Upstream of Compressor)
  • Air Cooler (Downstream of Compressor)
  • Discharge Scrubber (Downstream of Air Cooler)

Compressor Layout:

  • When locating compressors, consideration must be given to accessibility, maintenance and loss prevention requirements.
  • There must be Vehicular (Crane / Fork Lift Truck) Access-way on at least one side of the installation. Refer Fig. 1
Figure showing the requirement of Crane Access
Fig. 1: Figure showing the requirement of Crane Access
  • Compressor is generally located inside Shed with provision of Mono-Rail or EOT Crane for Maintenance. The capacity of crane to be decided based on 150% of highest weight of component to be lifted. To be checked with compressor vendor.
  • Compressor can be installed in Series and Parallel arrangement.
  • Minimum Distance between two Adjacent Compressors shall be 10m.
  • Generally Compressors are Grade Mounted (Fig. 2). But Process criteria / requirement will decide if it should be grade mounted or elevated
Grade mounted Centrifugal Compressor
Fig. 2: Grade mounted Centrifugal Compressor

Compressor Piping Layout:

Suction & Discharge Piping (Fig. 3):

  • Compressor Suction Piping Shall be as Short as Possible.
  • Compressor Suction Piping should have Inlet Filter / Strainer. It can be Temporary or Permanent
  • Suction Piping should be sloping / free draining towards Inlet Scrubber
  • Suction lines require a minimum straight run of piping upstream of the Suction nozzle which varies between 3 and 8 times the normal pipe size. (Vendor requirement)
  • All operating valves must be readily accessible, preferably from grade.
  • All line to Compressor shall be provided with break-up flanges for Maintenance.
  • Compressor Suction Line Flowmeter : Suction routing shall be such that Upstream and Downstream straight length shall be sufficient for the performance of Flowmeter
  • Isometrics – Both Suction and Discharge piping should have note for “Pickling and Passivation” i.e. Chemical cleaning of Lines before commissioning.
Suction and Discharge Piping
Fig. 3: Suction and Discharge Piping
  • Anti-Surge Valve Is Designed and Supplied by Compressor Vendor.
  • Input to Compressor Vendor for Designing / Sizing the Anti-Surge Valve is given by piping, by providing suction and discharge length.
  • Anti-Surge Valve is located on Anti-Surge line which is basically a by-pass / recirculation line between Compressor Suction and Discharge Piping for Surge control
  • Anti-Surge Valve shall be located at Highest Point and shall be free draining on both side

Lube Oil Cooler & Piping (Fig. 4):

  • Lube Oil Cooler Shall be Accessible from Road.
  • Lube Oil Cooler Shall be located as close to Compressor as Possible.
  • Lube Oil Cooler Piping Should Not Interfere with Access and Maintenance space.
  • Lube Oil Cooler line must be Free Gravity flow requirements.
  • Lube Oil Cooler Piping Should have Break-up Flanges for Maintenance purpose.
  • Lube Oil Cooler Isometric should also have note for “Pickling and Passivation” i.e. Chemical cleaning of Lines before commissioning.

Supporting:

  • First support from Compressor Suction and Discharge nozzle are either Spring support or Adjustable support for Alignment during Construction / Erection.
Lube Oil Cooler
Fig. 4: Lube Oil Cooler
  • Compressor piping should never be supported from the Compressor foundation. Pipe supports must be provided with independent foundations to avoid transmission of vibration.
  • Compressor Suction / Discharge Piping should be routed in such way that it has enough flexibility to accommodate Thermal Expansion and to Reduce Nozzle Load.
  • Compressor Suction / Discharge Piping should be adequately supported as per Stress Engineers Support requirements.
  • Process Should be consulted for any possibility of two phase flow / slug flow and line should be supported accordingly
  • As Compressor are meant for Gaseous fluid, the Hydro-test load on supports may be very high for big bore line. Hence we can recommend Temporary supports to be erected during Hydro-testing with the help of Stress Engineer.

Utility Requirements:

Following are the utilities required for the Compressor:

  • External Fuel gas for seal gas system
  • Instrument Air for the Instruments/Control system/Seal gas system

COMPRESSOR APPLICATION:

  • Refineries
  • Natural Gas Compression & Transportation Services
  • Oil Exploration – Gas Reinjection, Gas lift, etc.
  • Gas Liquefaction
  • Air Compression service
  • Refrigerant compression service
  • Refuelling applications

 

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