ASME B31.1-2020: Power Piping Changes

Worker in orange jumpsuit climbing to change power piping to ASME B31.1-2020.

What is Power Piping?

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 enormous 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 B31.1-2020: Power Piping, the standard for these systems.

What is ASME B31.1?

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 B31.1-2020 is this code. As a section of the B31, the overall American Society of Mechanical Engineers Code for Pressure Piping, ASME B31.1-2020 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.

Changes to B31.1-2020

ASME B31.1-2020 revises the 2018 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 the list of updates in the beginning of the document comprises six pages.

Some featured changes made to the ASME B31.1-2020 revision include:

  • Either U.S. Customary (USC) or International System (SI, also known as metric) units may be used with this edition. To emphasize this, the standard contains numerous revisions to SI equivalencies in figures throughout.
  • New definitions added for ferrous material, linear indication, rounded indication, maintenance, nonferrous, postweld hydrogen bakeout, and volumetric examination.
  • New section 101.2.6 specifies for provision to be made to safely contain or relieve any expected pressure to which the piping might be subjected.
  • Design minimum temperature may establish special design requirements and material qualification requirements.
  • New sections state that consideration shall be given to how ambient temperature conditions impact the displacement stress analysis and that piping shall be designed, arranged, and supported so as to withstand reaction forces due to fluid pressure and momentum effects during normal operations and anticipated transients.
  • New section 101.9, “Reduced Ductility Effects.”
  • In-process examination is now covered.
  • New section 137.4.6 outlines special provisions for testing piping components and subassemblies, closure welds, and flanged joints.
  • New procedures were added as an alternative to hydrostatic and pneumatic testing in new section 137.1.
  • The standard now specifies that the repair of covered piping systems (CPS) is to be conducted in accordance with the ASME B31.1 code used for the original construction or to a later edition as agreed by the owner and the jurisdictional authority, if applicable.
  • New section 149 outlines rerating piping systems.
  • Figure 100.1.2-8, “Code Jurisdictional Limits for Piping — Firetube Boiler,” and Figure 104.8-1, “Equations (15 [Stress Due to Sustained Loads]), (16 [Stress Due to Occasional Loads]), and (17 [Stress Due to Displacement Load Ranges]),” were added, and several other figures were revised.

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 B31.1-2020 revision by noting the number (20) in the margin.

Get ASME B31.1-2020

ASME B31.1-2020: Power Piping is available on the ANSI Webstore. Since this is the first part in the series of ASME B31 standards, some might benefit from acquiring the Piping Package, which contains all parts of the ASME Code for Pressure Piping, B31.

ASME B31.1-2020 is also bundled with ASME B31.3-2020: Process Piping as the Power and Process Piping Package.

Changes to ASME B31.1-2018

The previous iteration of the standard for power piping, which was released in 2018, was also a sizable revision. If you are interested in the major changes made to ASME B31.1-2018 from the 2016 edition, we have listed them below:

  • 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.”
3 thoughts on “ASME B31.1-2020: 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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