ASME B31.4 – What Is Piping

What is ASME B31.4? Developed and maintained by ASME, ASME B31.4 is the design code for pipelines transporting liquids and slurries between facilities, production, and storage fields, plants, and terminals, and within terminals and pumping, regulating, and metering stations associated with liquid pipeline systems. What is ASME B31.8? ASME B31.8 is the design code for pipelines for Gas Transmission and Distribution Piping Systems. This means this code provides design guidelines for piping transporting products that are predominately gas between sources and terminals, including compressor, regulating, and metering stations, and gas gathering pipelines. Fig. 1: A Typical Pipeline ASME B31.4 vs ASME B31.8 So, both the codes, ASME B31.4 and ASME B31.8 are pipeline design codes that cover the design, fabrication, installation, inspection, and testing of pipeline facilities. But, ASME B31.4 deals with pipelines transporting liquids and slurries whereas ASME B31.8 deals with gas transmission and distribution. Now the question is whether both can be used interchangeably and if not then what are the differences between ASME B31.8 and ASME B31.4. The liquid is incompressible while gas can be easily compressed, So the behavior of both fluids is different under pressure and temperature conditions. Hence, the ASME B31 committee devised two different codes for liquid and gas pipelines. Refer to the following image (Fig. 2) which lists down the expansion stress range results for the same stress system with the same parameters analyzed in Caesar II-2018. Fig. 2: Expansion Stress output for the same system based on ASME B31.8 and ASME B31.4 Results show that the expansion stress ratio for the system is around double (26.5%) for code ASME B31.8 as compared to ASME 31.4 (13.7%) which means code ASME B31.8 is more stringent from stress analysis consideration. In this article, we will list down a few of the major differences between B31.8 and B31.4 in a tabular format. There may be more that we have missed. Kind request to the readers to list those in the comments section and We will add them to the table in due course. ParameterASME B31.4ASME B31.8ScopeThe code ASME B31.4 governs the design requirements for pipeline systems that transports liquid or aqueous slurries of non-hazardous materialsThe ASME B31.8 code governs the design requirements for pipeline facilities used for the transportation of gasExclusionsBuilding services piping, such as water, air, or steam pressure vessels, heat exchangers, pumps, meters, and other such equipment, including internal piping and connections for piping casing, tubing, or pipe used in oil wells and wellhead assemblies are not part of ASME B31.4Cryogenic piping systems, vent piping to operate at substantially atmospheric pressures for waste gases of any kind, piping in oil refineries or natural gasoline extraction plants, etc are excluded from the scope of ASME B31.8.Minimum Temperature RangeASME B 31.4 covers pipelines with a temperature above -30 Deg C.Minimum design temperature as per ASME B31.8 can be reduced further subject to the inclusion of a proper fracture control program for that material.Maximum Temperature RangeThe maximum metal temperature limit for B31.4 is 120 Deg C.ASME B31.8 covers piping with metal temperatures up to 232°C.Allowable StressAs per ASME B31.4, the allowable stress is dependent only on specified minimum yield strength of pipe material.The allowable stress in ASME B31.8 is dependent on specified minimum yield strength and temperature derating factor which reduces the allowable values when the temperature is more than 120 Deg C.Design Factor FThe Maximum Value of Design Factor F in thickness calculation following ASME B31.4 is 0.72. Lower values can be used as service and location may dictate.Depending on location class, the value of F in code ASME B31.8 varies from 0.4 to 0.8Toughness RequirementThe toughness requirement criteria in B31.4 is comparatively less Stringent.ASME B31.8 provides more Stringent toughness requirements.Table-1: ASME B31.8 vs ASME B31.4 Few more useful Resources for you..Few Important points for Stress Analysis based on ASME B 31.4Pipeline Virtual Anchor Length CalculationPipeline wall thickness calculation with exampleComparison between Piping and Pipeline EngineeringA short presentation on Offshore Pipeline SystemsDifference between Tee and Barred TeeA Presentation on Pipelines – Material Selection in Oil & Gas IndustryCorrosion Protection for Offshore PipelinesStartup and Commissioning of the Pipeline: An ArticleDesign of Cathodic Protection for Duplex Stainless Steel (DSS) PipelineAn Article on Micro Tunneling for Pipeline InstallationAn article on Software-Based Pipeline Leak DetectionA small presentation on OFFSHORE PIPELINE DESIGNA small briefing about “PIPELINE CONSTRUCTION