ASME B31.2 Fuel Gas Piping and B31.3 Process Piping sope of work


In 1955 a decision was made to publish separate code sections of B31, Code for Pressure Piping. Consequently, Section 2 of B31.1-1955 was updated and revised to publish as USAS B31.2—1968, Fuel Gas Piping. No edition of this code section was published after 1968. This code was withdrawn in 1988.

USAS B31.2 covers the design, fabrication, installation, and testing of piping systems for fuel gases such as natural gas, manufactured gas, and liquefied petroleum gas (LPG); air mixtures above the upper combustible limit; LPG in the gaseous phase; or mixtures of these gases.

This code applies to fuel gas piping systems both within and between the build¬ings, from the outlet of the consumer meter assembly, and to and including the first pressure-containing valve upstream of the gas utilization device.

This code does not apply to:

  • Vacuum piping systems.
  • Fuel gas piping systems with metal temperatures above 450°F or below -20°F.
  • Fuel gas piping systems within petroleum refineries, loading terminals, natural gas processing plants, bulk plants,
  • compounding plants, or refinery tank farms, and so forth within the scope of USAS B31.3.
  •  Fuel gas piping systems in power and atomic energy plants within the scope of USAS B31.1
  •  Fuel gas piping systems within the scope of USAS B31.8
  •  Fuel gas piping systems within the scope of USAS Z21.30
  •  Piping systems within the scope of USAS Z106.1
  •  Proprietary items of equipment, apparatus, or instruments, such as compressors, gas-generating sets, and calorimeters
  •  Design and fabrication of pressure vessels covered by the ASME Boiler and Pressure Vessel Code
  • Support structures and equipment such as stanchions, towers, building frames, pressure vessels,mechanical equipment,and foundations
  • Piping systems for conveying premixed fuel gas-air mixtures which are in the combustible or inflammable limits or range


This code prescribes requirements for the materials, design, fabrication, assembly, erection, examination, inspection, and testing of piping within the property limits of facilities engaged in the processing or handling of chemical petroleum or related products. Figure A4.4 provides an illustration of the scope of ASME B31.3. The requirements of ASME B31.3 apply to piping for all fluids, including raw, intermediate, and finished chemicals; petroleum products, gas, steam, air, and water; fluidized solids; and refrigerants.

In case of packaged equipment, the interconnecting piping with the exception of refrigeration piping shall be in compliance with the requirements of ASME B31.3. The refrigeration piping may conform to either ASME B31.3 or ASME B31.5.

The requirements of ASME B31.3 do not apply to piping systems designed for internal gauge pressures at or above 0 but less than 15 (100 kPa gauge) psig provided the fluid handled is nonflammable, nontoxic, and not damaging to human tissue and its design temperature is from -29°C (-20°F) through 180°C (366°F).

The following piping and equipment are not required to comply with the require¬ments of ASME B31.3:
  • Power boiler and the boiler external piping
  • Piping covered by ASME B31.4, B31.8, or B31.11, although located on the company property.
  • Piping covered by applicable governmental regulations.
  • Piping for fire-protection systems.
  • Plumbing, sanitary sewers, and storm sewers.
  • Tubes, tube headers, crossovers, and manifolds of fired heaters which are internal to the heater enclosures.
  • Pressure vessels, heat exchangers, pumps, compressors, and other fluid-handling or processing equipment, including internal piping and connections for external piping.
ASME  B31.1 Power Piping code scope of Work check here
ASME B31.4 Fluid Transportation and ASME B31.5 Refrigeration Piping code scope of work 

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