ASME B16.25:2003 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-wallcomponents,and for preparation of internal ends(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 pass.Details 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 quali-fied, but does not prescribe specific welding processesor procedures. Unless otherwise specified by the pur-chaser, it does not apply to welding ends conformingto ASME B16.5 or B16.9.
1.3 Standard Units
The values stated in either metric or inch units are tobe regarded separately as standard. Within the text, theinch units are shown in parentheses. The values statedin each system are not exact equivalents; therefore, eachsystem must be used independently of the other. Combining values from the two systems may result in nonconformance with the Standard.
1.4 Size
NPS followed by a dimensionless number, is the des-ignation for nominal fitting size. NPS is related to thereference nominal diameter, DN, used in internationalstandards. The relationship is typically as follows:
For NPS 2 4, the related DN is: DN = 25 x NPS
1.5 Referenced Standards
Standards and specifications adopted by reference inthis Standard are shown in Mandatory Appendix Iwhich is part of this Standard. It is not considered practi-cal to identify the specific edition of each standard andspecification in the individual references; instead, thespecific edition is identified in Mandatory AppendixII. An end preparation made in conformance to thisStandard in all other respects will be considered to bein conformance to the Standard even though the editionreference may be changed in a revision of the Standard.
1.6 Quality Systems
Nonmandatory requirements relating to the manufacturer’s quality system program are described in Non-mandatory Appendix A.
1.7 Convention
For the purpose of determining conformance withthis Standard, the convention for fixing significant digitswhere limits,maximum or minimum values, are specified shall be “rounding off” as defined in ASTM PracticeE 29. This requires that an observed or calculated valueshall be rounded off to the nearest unit in the last right-hand digit used for expressing the limit Decimal valuesand tolerances do not imply a particular method of mea-surement.
2 TRANSITION 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 inner surfaceof the component must lie. Except as specified in Note(5) to Fig. 1 and as otherwise specified by the purchaserthe exact contour within this envelope is the manufacturer’s option, providing it maintains the specified mini-mum wall thickness, has no slopes steeper than thoseindicated for the respective regions, and includes theproper surface for backing rings if specified.