Sunday, July 21, 2013

Asme B31.8: Gas Transmission And Distribution Piping Systems


A pipeline or transmission line is defined as that pipe which transmits gas from a source or sources of supply to one or more large-volume customers or to a pipe used to interconnect sources of supply. ASME B31.8 prescribes requirements for the design, fabrication, installation, testing, and safety aspects of operation and maintenance of gas transmission and distribution piping systems, including gas pipelines, gas compressor stations, gas metering and regulation stations, gas mains, and service lines up to the outlet of the customer’s meter set assembly.

Also included within the scope of ASME B31.8 are gas storage equipment of the closed-pipe type, fabricated or forged from pipe or fabricated from pipe and fittings, and gas storage lines.

The requirements of ASME B31.8 also apply to the use of elements of piping systems, including but not limited to pipe, valves, fittings, flanges, bolting, gaskets, regulators, pressure vessels, pulsation dampeners, and relief valves.

The requirements of ASME B31.8 are applicable to operating and maintenance procedures of existing installations and to the update of existing installations.

ASME B31.8 does not apply to the following:
  • Design and manufacture of pressure vessels covered by the ASME Boiler and Pressure Vessel Code
  • Piping with metal temperatures above 450 F (232 C) or below 20 F ( 29 C)
  • Piping beyond the outlet of the customer’s meter set assembly (refer to ANSI Z223.1 and NFPA 54)
  • Piping in oil refineries or natural gasoline extraction plants, gas-treating plant piping other than the main gas stream piping in dehydration, and all other processing plants installed as part of a gas transmission system, gas manufacturing plants, industrial plants, or mines (see other applicable sections of the ASME Code for Pressure Piping, B31)
  • Vent piping to operate at substantially atmospheric pressures for waste gases of any kind
  • Wellhead assemblies, including control valves, flow lines between wellhead and trap or separator, or casing and tubing in gas or oil wells
  • The design and manufacture of proprietary items of equipment, apparatus, or instruments
  • The design and manufacture of heat exchangers
  • Liquid petroleum transportation piping systems (refer to ANSI/ASME B31.4)
  • Liquid slurry transportation piping systems (refer to ASME B31.11)
  • Carbon dioxide transportation piping systems
  • Liquefied natural gas piping systems (refer to NFPA 59 and ASME B31.3)

Effective Code Edition, Addenda, and Code Cases

To determine the effective edition, addenda, and code cases to be invoked for an application or piping systems within the jurisdiction of ASME B31.8, follow the criteria delineated for piping systems within the scope of ASME B3 1.1: 
No edition and addenda shall be applied retroactively to existing installations in so far as design, fabrication, installation, and testing at the time of construction are concerned. Further, no edition and addenda shall be applied retroactively to established operating pressures of existing installations, except as provided for in Chapter V of ASME B31.8.

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