Changes to ASME B31.3, "Process Piping"
By Vince Carucci
The 2014 edition of ASME B31.3 is a revision of the 2012 edition, was
officially issued February 27, 2015, and became effective six months after
that date. As with previous editions, it includes several pages at the
beginning that highlight where changes were made, and these are further
identified by a margin note (14) in the body of the code placed next to
the affected area.
This article highlights several, but not all, of the technical changes.
Please refer to ASME B31.3 for complete details.
- Para. 300.2b. Definition of Category M fluid service revised to
also require the owner to determine that the requirements for Normal
Fluid Service do not provide sufficient assurance of leak tightness.
- Table 300.4. Entry for Appendix P, “Alternative Rules for
Evaluating Stress Range” deleted to be consistent with deletion of
- Para. 302.3.5d. Added definition of SL, stress due to sustained
loads, which was inadvertently left out of the 2012 code although SL
was included in the equation for calculating the allowable
displacement stress range. In doing so, the definition acknowledges
that supports may be active in some conditions and inactive in others,
and the maximum value of SL considering all support conditions must be
- Table 304.1.1. Revised by adding two new temperature break points
for determining coefficient Y in the required wall thickness equation:
1200°F, and 1250°F and above.
- Para. 305.2.3 that specifies pipe that may be used for severe
cyclic conditions has been simplified by referring to pipe listed in
Tables A-1A and A-1B, and specified quality factors, rather than
listing the pipe specifications here.
- Para. 306.6 covering thermowells has been added.
- Para. 319.2.3b covering displacement stress range has been edited
to recognize that supports may be active in some conditions and not in
others, and this must be considered in the analysis. I have had to
point out this active vs. inactive support situation to contractors
many times while auditing their piping system analyses.
- Para. 319.5 covering reactions has been revised and expanded in
several respects. For example, it recognizes that the potentially
beneficial effect of cold spring in reducing reaction loads cannot be
assured, and design calculations must consider this. Some companies
have recognized this situation in their engineering standards for many
years and limited the potential use of cold spring.
- Para. 328.5.4b and c have been revised and Para. 328.5.4i has been
added to cover requirements for integrally reinforced branch
connection fittings. There is also a new Fig. 328.5.4F that provides
acceptable details for such fittings.
- Para. 328.7 is new and covers requirements for structural
- Para 330 and Table 330.1.1 covering preheat temperatures have been
revised. For example: weld metal analysis “A-No” has been eliminated,
carbon percent has been added as a criterion for carbon steels, at
least some preheat temperatures have been changed, etc.
- Para. 331.1 and Table 331.1.1 covering heat treatment requirements
have been revised. For example in the table: “A-No” was eliminated and
Group Nos. are added, maximum Brinell hardness was deleted, etc.
- Table 331.1.2 was added and provides alternate PWHT requirements
for carbon and low alloy steels, P-Nos. 1 and 3.
- Table 331.1.3 was added and covers possible exemptions to
mandatory PWHT. This identifies additional requirements or limitations
that must be used (e.g., higher preheat temperature, multiple layer
- Para. 342.1 covering NDT personnel qualifications revised to
require certification per ASME Code Section V. It previously referred
to SNT-TC-1A for guidance.
- Paras. 344.3 and 344.4 covering magnetic particle and liquid
penetrant examinations, respectively, completely revised and expanded
to include methods and acceptance criteria.
- Para 345.2.1a covering limitations on test pressure. Revised to
clarify that the pipe stress cannot exceed the material yield strength
based on minimum pipe wall thickness. This
recognizes that pipe may be supplied thinner than the nominal
thickness up to its under thickness tolerance (typically 12 1/2 %).
- Para 345.2.2a regarding examination for leaks. Revised to permit a
reduction in test pressure to not less than the design pressure while
the examination is being done.
- Para. 345.4.2 covering hydrostatic test pressure has been revised.
- The maximum value of (ST/S) is no longer limited to 6.5.
- If the piping system is made up of equivalent lengths of more
than one material, the minimum calculated value of (ST/S) must be
- Para. 345.5.4b covering pneumatic test pressure has been revised
to clarify that the pipe stress cannot exceed 90% of the material
yield strength based on minimum pipe wall
- Numerous revisions have been made to the requirements for piping
in Category M fluid service contained in Chapter VIII. Refer to ASME
B31.3 for details. For example:
- Para. M302.2.4 does not permit allowances for pressure and
- Para. M306.4.2 now states that flared laps shall not be used.
They were previously permitted if they met certain requirements.
- Para. M320 has been added to require the analysis of sustained
loads per Para. 320. Its prior omission was probably an
- Para. M321 has been revised to clarify that only supporting
elements that are welded to the pipe must be of listed material.
The prior wording required that all pipe supporting elements must
be of listed material.
- Para. M322.6.3 was revised to refer to the ASME Code Section
VIII for overpressure protection requirements.
- Para. M335.10 has been added to cover pipe identification
- Numerous other revisions were made in Chapter IX (High Pressure
Piping), Chapter X (High Purity Piping), Appendix A (Allowable Stress
and Quality Factors for Metallic Piping and Bolting Materials). Refer
to ASME B31.3 for details.
©2010 Carmagen Engineering, Inc.