ASME B31.1-2018: Power Piping Changes

Worker in orange jumpsuit climbing to change power piping to ASME B31.1-2018

Power piping, unsurprisingly, is found in electric power generating stations, such as industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems. This places an exuberant amount of stress and pressure on the need to specify and adequately operate these systems, even beyond the stresses and pressure by which the piping intrinsically functions. These interests are reflected in the content of and changes made to ASME B31.1-2018: Power Piping, the standard for these systems.

Since any failure in power piping systems not only inhibits the piping’s performance locally but can also result in numerous people losing their power, heat, and air conditioning, it is crucial that they adhere to code. ASME B31.1-2018 is this code. As a section of the B31, the overall American Society of Mechanical Engineers Code for Pressure Piping, ASME B31.1-2018 exists as its own document for power piping.

Specifically, it details the design, materials, fabrication, erection, test, inspection, operation, and maintenance of piping systems. Piping used with the Code includes pipe, flanges, bolting, gaskets, valves, pressure-relieving valves/devices, fittings, and the pressure-containing portions of other piping components.

ASME B31.1-2018 revises the 2016 edition of the same standard code for power piping, and, as the key document for the industry, it contains numerous changes crucial for keeping the standard current. In fact, there were so many changes made to this edition that, when listed at the beginning of the current document, the referenced locations of each change comprise three pages.

Some featured changes made to the ASME B31.1-2018 revision include:

  • Clarification that, where service requirements necessitate measures beyond those addressed in the code, such measures are to be specified by the engineering design.
  • New definitions for austenitizing, heat treatments, subcritical heat treatment, and heat treatments, tempering.
  • Revisions to figures for code jurisdictional limits for piping examples to better convey the information they represent.
  • New figure on “Code Jurisdictional Limits for Piping – HRSG – Desuperheater Protection Devices.”
  • Revised equation for the minimum wall thickness of straight pipe under internal pressure (including seamless, longitudinal welded, or spiral welded and operating below the creep range). In the section featuring this equation, nomenclature has also been alphabetized and W, the weld strength reduction factor, has been added.
  • Removed section 104.1.4 from ASME B31.1-2016, which covered equations specific to longitudinal-welded or spiral-welded pipe operating in the creep range.
  • Updates to the equation to stress due to occasional loads, which now includes the defined term Po representing the pressure coincident with the occasional load being evaluated in psi (kPa).
  • Inclusion of carbon-molybdenum steel in the list of steels in the carbide phase that may be converted to graphite upon prolonged exposure to high temperatures.
  • New subparagraph in the steel section discussing how carbon and low alloy steels can be susceptible to flow-accelerated corrosion (FAC) under certain conditions.
  • Inclusion of nickel alloys in the calculations for the forming strains of cold-formed areas of components.
  • Substantial updates to the section covering inspection and qualification of authorized inspectors for boiler external piping.
  • Removed Mandatory Appendix J, “Quality Control Requirements for Boiler External Piping (BEP)” from ASME B31.1-2016.
  • New figure displaying the winding angle of filament-wound thermosetting resin pipe.
  • New Mandatory Appendix O, “Use of Alternative Ultrasonic Acceptance Criteria.”
  • New Mandatory Appendix P, “Metallic Bellows Expansion Joints.”
  • Removed Nonmandatory Appendix VI, “Approval of New Materials.”

As you can see, these changes are plentiful, and they touch the many facets of power piping covered by the standard document. Users can easily find any alteration made to the ASME B31.1-2018 revision by noting the number (18) in the margin.

ASME B31.1-2018 is part of the following standards packages:

Power and Process Piping Package

Piping Package

ASME B31.1-2018: Power Piping is available on the ANSI Webstore.

3 thoughts on “ASME B31.1-2018: Power Piping Changes
  1. Thanks ANSI for enriching an engineer’s knowledge. Sincerely appreciate the blog.
    Request pls enroll my email so to receive update, without missing and refer it when required. My I’d given below.

  2. Dear All,

    As per the latest ASME B31.1 2018 edition, there is a update in occasional stress equation due to occasional loads, which now includes the defined term Po representing the pressure coincident with the occasional load being evaluated in psi (kPa).

    I request can someone elaborate this and how we can evaluate this stress calculation.

  3. Hi Damanpreet,

    Initially, we were combining by scalar addition, the pure occasional stresses (wind / seismic/ PSV / steam hammer etc.) with Design sustained stress (W+P1+H). Since design pressure is not coincident at the time when the earthquake or wind strikes, thus now with this new Codal update, we can combine pure occasional load cases with Operating pressure (W+P2+H) sustained stresses to get our total code compliant occasional stresses. This would be of good help as the pressure component has quiet a lot longitudinal stress which is quiet significant.

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