ASME B16.25:1997 pdf download BUTTWELDING ENDS
1 SCOPE
1.1 General
This Standard covers the preparation of buttweldingends of piping components to be joined into a pipingsystem by welding.It includes requirements for weldingbevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends(including dimensions and tolerances). Coverage in-cludes 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 rootpass.Details of preparation for any backing ring must bespecified in ordering the component.
1.2 Application
This Standard applies to any metallic materials forwhich a welding procedure can be satisfactorily quali-fied, but does not prescribe specific welding processesor procedurcs. Unless otherwise specified by the purchaser, it does not apply to welding ends conformingtO ASME B16.5，B16.9,r B16.28.
1.3 Standard Units
The values stated in either metric or inch units areto be regarded separately as standard. Within the text,the inch units are shown in parentheses. The valuesstated in each system are not exact equivalents; thereforeeach system must be used independently of the other.Combining values from the two systems may result innonconformance with the Standard.
1.4 Referenced Standards
Standards and specifications adopted by reference inthis Standard are shown in Annex C. which is part ofthis Standard, It is not considered practical to identifythe specific edition of each standard and specificationin the individual references; instead the specific editionis identified in Annex C. An end preparation made in conformance to this Standard in all other respects, willbe considered to be in conformance to the Standardeven though the edition reference may be changed ina subsequent addendum to or revision of the Standard
1.5 Quality Systems
Nonmandatory requirements relating to the manufacturer’s Quality System Program are described inAnnex B.
1.6 Convention
For the purpose of determining conformance withthis Standard, the convention for fixing significant digitswhere limits, maximum or minimum values, are speci-fied shall be “rounding off” as defined in ASTMPractice E 29. This requires that an observed or calcu-lated value shall be rounded off to the nearest unit inthe last right-hand digit used for expressing the limit.Decimal values and tolerances do not imply a particularmethod of measurement.
2 TRANSITION CONTOURS
Figure I delineates the maximum envelope in whichtransitions from welding bevel to the outer surface otthe component and from the root face to the innersurface of the component must lie. Except as specifiedin Note (5) to Fig. l and as otherwise specified bythe purchaser, the exact contour within this envelopeis the manufacturer’s option, providing it maintains thespecified minimum wall thickness, has no slopes steeperthan those indicated for the respective regions,andincludes the proper surface for backing rings if specified
3 WELDING BEVEL DESIGN
3.1 Bevels for Other Than GTAW Root Pass
(a) Components having nominal wall thicknesses of3 mm (0.12 in.) and less shall have ends cut squareor slightly chamfered.(b) Components having nominal wall thicknessesover 3 mm (0.12 in.) to 22 mm (0.88 in.) inclusiveshall have single angle bevels as illustrated in Fig. 2

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