- Introduction to ASME B31.3 – 2020
The newly released edition of the ASME B31.3-2020 has been issued on the 18th of June, 2021 and is set to become universally effective from 17th December 2021. This new edition provides many clarifications, updates, and changes to the 2018 edition of the code. This article will list down the 10 major changes that ASME B31.3-2020 will bring into effect.
- Major Changes in ASME B31.3-2020
- Requirements for Design and Fabrication: This section has been revised to include a new requirement for the design of pressure-containing and non-pressure-containing parts to be in accordance with the applicable construction codes.
- Requirements for Materials: The material requirements have been revised to clarify the requirements for welded joints, welding symbols, and welding processes.
- Requirements for Hydrostatic Tests: This section has been revised to include a new requirement for hydrostatic testing of piping systems that are in-service.
- Requirements for Pressure Relief Devices: The requirements for pressure relief devices have been revised to include a new requirement for pressure relief devices to be certified to the applicable standards.
- Requirements for Valves: This section has been revised to include a new requirement for valves to be inspected and tested prior to installation in order to ensure they meet the requirements of the code.
- Requirements for Piping Supports: The requirements for piping supports have been revised to include a new requirement for supports to be designed to resist forces and moments resulting from the design pressure and temperature of the piping system.
- Requirements for Piping Systems: The requirements for piping systems have been revised to include a new requirement for piping systems to be designed and constructed in accordance with the applicable codes and standards.
- Requirements for Examinations and Tests: This section has been revised to include a new requirement for examinations and tests to be performed on components, piping systems, and pressure vessels in order to ensure they meet the requirements of the code.
- Requirements for Special Services: The requirements for special services have been revised to include a new requirement for special services to be identified and analyzed to ensure they meet the requirements of the code.
- Requirements for Pipeline Transportation Systems: This section has been revised to include a new requirement for pipeline transportation systems to be designed and constructed in accordance with the applicable codes and standards.
Changes in Units of Measurement
Introduction to Changes in Units of Measurement
The ASME B31.3-2020 has added an additional clause 300.1.4– Units of Measurement stating that either SI or U.S. Customary units should be independently used as the stated values in the ASME B31.3-2020 are not exact equivalents. If It is required to convert from one system of units to another, conversion should be made by rounding the values to the number of significant digits of implied precision in the starting value but not less than four significant digits for use in calculations.
Previous Clause Renumbered
The earlier clause in the 2018 edition “300.1.4- Rounding” has been renumbered as clause 300.1.5 in ASME B31.3-2020.
Changes in Flexibility Factor and Stress Intensification Factor
Introduction to Changes in Flexibility Factor and Stress Intensification Factor
Appendix D that was providing the equations for the Flexibility Factor and Stress Intensification Factors of Table 300.4 Status of Appendices in B31.3 has been deleted from ASME B31.3-2020 edition. In the absence of more directly applicable data, the flexibility factor, k, and stress intensification factor, i, shown in ASME B31J shall be used for flexibility calculations described in para. 319.4. Flexibility factors and stress intensification factors for branch connections are defined for in-plane, out-plane, and torsion moments on both the run and branch legs. Branch leg calculations shall use the appropriate branch factor (i.e., kib, kob, ktb, iib, iob, and itb), and run leg calculations shall use the appropriate run factor (i.e., kir, kor, ktr, iir, ior, and itr).
Impact of Changes in Flexibility Factor and Stress Intensification Factor
This is the most significant change for piping stress engineers. Now using B31J or FEA will be mandatory. Earlier, the same SIFs were used in the stress analysis programs for headers and branches which in some cases becomes too conservative. Now that problem will be resolved.
Experimental Stress Analysis for Unlisted Components
ASME B31.3 2020 – Basic Allowable Stress for Experimental Stress Analysis
As per clause 304.7.2 sub-para (b) of the latest edition of ASME B31.3 2020, for experimental stress analysis of unlisted components following the equations from ASME BPVC, Section VIII, Division 2, Annex 5-F, the basic allowable stress from Table A-1 (or A-1M) of B31.3-2020 shall be used as allowable stress, S.
Proof Testing of Unlisted Components
For proof testing of unlisted components following the equations from ASME B16.9, MSS SP-97, or ASME BPVC, Sec VIII, Division 1, UG-101, the basic allowable stress from Table A-1 or Table A-1M shall be used in place of the allowable stresses, S and S2, in Division 1 where applicable.
Bending Stress Calculation in ASME B31.3
The American Society of Mechanical Engineers (ASME) B31.3 is a code of practice for process piping and tubing systems. It provides guidance on design, materials, fabrication, testing, inspection, and installation of piping systems. Clause 319.4.4 sub-paragraph (c) of ASME B31.3 2018 included equations 19 and 20 for calculating bending stresses in headers and branches. However, this clause was removed from ASME B31.3 2020 and equation 23-b2 was also deleted.
Impact Test Requirement for Weld Metals
The American Society of Mechanical Engineers (ASME) has revised the impact test requirement criteria for Weld Metal in Table 323.2.2 of ASME B31.3-2020. Previously, in code B31.3-2018, the impact test was an absolute requirement for design minimum temperatures lower than -29°C. In the latest edition of B31.3, the requirement for an impact test has been lowered to -18°C.
Additional Standards
ASME B31.3-2020 Table 326.1 Standards
The American Society of Mechanical Engineers (ASME) B31.3-2020 is a code of practice for pressure piping that includes requirements and guidelines for materials, fabrication, assembly, inspection, testing, and certification of piping systems. Table 326.1 of ASME B31.3-2020 contains standards for non-metallic piping systems. The 2020 revision of ASME B31.3 includes two new standards: ASTM F1476 and ASTM F1548. Additionally, AWWA C504 has been removed from Table 326.1. Standards ASTM D3309, D2310, D2447, and ASTM F1974 have also been deleted from Table A326.1 Component standards for non-metallic piping systems.
New Additions to ASME B31.3-2020
ASTM F1476 and ASTM F1548 have been added to Table 326.1 of ASME B31.3-2020. ASTM F1476 covers the requirements for the design, manufacture, testing and qualification of reinforced thermoplastic pipe and fittings for use in pressure applications. ASTM F1548 covers the requirements for the design, manufacture, testing and qualification of reinforced thermoplastic pipe systems for use in chemical process applications.
Deletions from ASME B31.3-2020
AWWA C504 has been removed from Table 326.1 of ASME B31.3-2020. Additionally, standards ASTM D3309, D2310, D2447, and ASTM F1974 have been deleted from Table A326.1 Component standards for non-metallic piping systems.
Use of ASME B31P for Preheating and Heat Treatment
ASME B31.3-2020 provides permission for the use of preheating rules from ASME B31P as an alternative to the general preheat requirements and also recommends the process and temperature control methods specified in ASME B31P for heat treatment purposes.
Consideration of Frictional Clamping Force for Supporting Non-Metallic Piping
ASME B31.3-2020 prohibits the use of frictional forces from clamping pressure as an anchor mechanism for supporting non-metallic piping systems, unless the support/anchor is specifically recommended by the manufacturer. Positive stops such as shear collars can be used as axial restraints. This was not the case in ASME B31.3-2018.
Revisions to Shear and Bearing Allowable for High-Pressure Piping System
ASME B31.3-2020 has made revisions to the allowable stress definition for shear and bearing in the case of high-pressure piping. The allowable stress in shear is now 0.57 times Syt, in place of 0.8 times as provided in B31.3-2018. Additionally, the allowable stress in bearing is now 1.0 times Syt, in place of 1.6 times as provided in B31.3-2018.
Changes to Other Materials for High-Pressure Piping System
ASME B31.3-2020 has also revised the basis for allowable stresses for other materials (other than bolting materials) for the high-pressure piping system. For details, refer to clause K302.3.2 sub-paragraphs (b), (c), and (d).
Revisions in ASME B31.3-2020 for High-Pressure and High-Purity Piping Systems
Most of the changes or revisions in ASME B31.3-2020 have been made for high-pressure and high-purity piping systems. These revisions provide a more secure and reliable piping system for high-pressure and high-purity applications.