The new edition of B31.3 is scheduled to be issued December 2022. As usual, there are many clarifications, updated references to codes and standards, updates to basic allowable stresses and additional listed materials. These types of changes are not described here.
There are some substantive changes as well, the most significant of which are:
Stress Range Factor (§302.3.5)
The slope of the curve for the stress range factor (f) was changed from a slope of 5:1 to a slope of 3:1 based on the ASME Pressure Vessel and Piping paper PVP-61871 authored by Hinnant & Paulin. They showed that Markl’s original slope was based on a small amount of fatigue test data and a very small amount of data in the multimillion fatigue cycle range. Further test data, based on Markl’s original testing protocol, weld profiles, and test stand, shows that the using a fatigue curve with a slope of 3:1 is more accurate than the Code’s previous fatigue curve with a slope of 5:1.
Double-Seated Valves (§307.2.3)
For double seated valves larger than NPS 2, the Code requires that the designer determine if a change in fluid temperature or a change in fluid phase could result in a pressure between the valve seats above the rating of the valve. If so:
- Valve cavity must be designed to take the increased pressure, or
- Valves must be equipped with a means to relieve the internal body cavity pressure
Fillet Welds (§328.5.2)
Added permission for any fillet welds greater than 5 mm be undersized by up to 1.5 mm for a small portion of the circumference of the weld.
Fabricated Laps (§ 328.5.5)
Added more specific requirements including minimum weld size and the requirement that welds be full penetration.
Attachment Welds (§328.7 & §341.4)
Added permission to use stud welding for attachments. Added the requirement that when removing temporary attachments that the surfaces be blended smoothly into the surrounding base metal. Added examination requirements for surfaces where attachment welds have been removed.
Postweld Hydrogen Bakeout (§300.2 & §331.1.2)
Defined postweld hydrogen bakeout and noted that separate procedure qualifications are not required when performing it.
Progressive Sampling for Examination (§341.3.4)
Revised the text to require progressive sampling only for examination of joints. Also made it clear that when defects are found, the progressive sampling applies only to the work of the same welder, brazer, bonder, or operator.
Weld Acceptance Criteria (Table 341.3.2)
Added a limitation for cumulative length of linear indications of 8% of total weld length.
Examination Personnel Qualification (§342.1)
Broadened the ways in which the employer’s written practice for the qualification program can be developed.
Leak Test Gauges (§345.2.2(d))
Added requirements for leak test pressure gages.
Pneumatic Leak Test Preliminary Check (§345.5.5)
Changed the requirement for a check of mechanical joints during the preliminary leak check to a requirement of checking all joints, including welded and bonded joints.
Weld Coupon Examination (§U341.4.5)
Revised the list of situations that require a coupon to be made and examined.
External Loads on Flanges (§F312.1)
Added a reference to ASME BPVC, Section VIII, Division 1, UG-44(b) as an acceptable method for qualifying piping external loads on ASME B16.5 and ASME B16.47 welding neck flanges.
Allowable Stresses for High Pressure Piping (Appendix K)
Added Table K-1M, allowable stresses in MPa.
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