ASME B16.25:2017 pdf free download – Buttwelding Ends
1.1 General
This Standard covers the preparation of buttweldingends of piping components to be joined into a pipingsystem by welding. lt includes requirements forwelding bevels, for external and internal shaping ofheavy-wall components,and for preparation of internalends (including dimensions and tolerances). Coverageincludes preparation for joints with the following:
(a) no backing rings
(b) split or noncontinuous backing rings
(c) solid or continuous backing rings
(d) consumable insert rings
(e) gas tungsten arc welding (GTAW) of the root passDetails of preparation for any backing ring must bespecified when ordering the component.
1.2 Application
This Standard applies to any metallic materials forwhich a welding procedure can be satisfactorily qualifiedbut does not prescribe specific welding processes orprocedures. Unless otherwise specified by the purchaser,it does not apply to welding ends conforming to ASMEB16.5.B16.9,or B16.47.
1.3 Relevant Units
This Standard states values in both SI (Metric) and U.S.Customary units. These systems of units are to beregarded separately as standard. Within the text, theU.s.Customary units are shown in parentheses or in aseparate table that appears in Mandatory Appendix l.The values stated in each system are not exact equivalents;therefore, it is required that each system of units be usedindependently of the other. Combining values from thetwo systems constitutes nonconformance with theStandard.
1.4 Size
Nominal pipe size (NPS), followed by a dimensionlessnumber, is the designation for nominal fitting size. NPS isrelated to the reference nominal diameter (DN) used ininternational standards.The relationship is typically asfollows:
1.5 Referenced Standards
Standards and specifications adopted by reference inthis Standard are shown in Mandatory Appendix l1. Itis not considered practical to identify the specificedition of each standard and specification in the individualreferences. Instead, the specific edition reference is iden-tified in Mandatory Appendix l1.A product made in confor-mance with a prior edition of referenced standards will beconsidered to be in conformance, even though the editionreference may be changed in a subsequent revision of thestandard.
1.6 Quality Systems
Nonmandatory requirements relating to the manufac-turer”s quality system program are described inNonmandatory Appendix A.
1.7 Convention
For determining conformance with this Standard, theconvention for fixing significant digits where limits(maximum and minimum values) are specified shall beas defined in ASTM E29.This requires that an observedor calculated value be rounded off to the nearest unit in the last right-hand digit used for expressing the limit. Decimalvalues and tolerances do not imply a particular method of measurement.
2TRANSITION CONTOURS
Figure 1 delineates the maximum envelope in whichtransitions from welding bevel to the outer surface ofthe component and from the root face to the innersurface of the component must lie. Except as specifiedin Note (5) to Figure 1, and as otherwise specified bythe purchaser, the exact contour within this envelopeis the manufacturer’s option, provided it maintains thespecified minimum wall thickness,has no slopes steeper than those indicated for the respective regions,and includes the proper surface for backing rings ifspecified.