ASME B16.25:2012 pdf download

ASME B16.25:2012 pdf download.Buttwelding Ends
1 SCOPE
1.1 General
This Standard covers the preparation of buttwelding ends of piping components to be joined into a piping system by welding. It includes requirements for welding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and tolerances). Coverage includes 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 be specified when ordering the component.
1.2 Application
This Standard applies to any metallic materials for which a welding procedure can be satisfactorily qualified but does not prescribe specific welding pro- cesses or procedures. Unless otherwise specified by the purchaser, it does not apply to welding ends conforming to ASME B16.5, 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 be regarded separately as standard. Within the text, the U.S. Customary units are shown in parentheses or in a separate table that appears in Mandatory Appendix I. The values stated in each system are not exact equiva- lents; therefore, it is required that each system of units be used independently of the other. Combining values from the two systems constitutes nonconformance with the Standard.
1.4 Size
Nominal pipe size (NPS), followed by a dimensionless number, is the designation for nominal fitting size. NPS is related to the reference nominal diameter (DN) used in international standards. The relationship is typically as follows:
1.5 Referenced Standards
Standards and specifications adopted by reference in this Standard are shown in Mandatory Appendix II. It is not considered practical to identify the specific edition of each standard and specification in the individual ref- erences. Instead, the specific edition reference is identi- fied in Mandatory Appendix II. A product made in conformance with a prior edition of referenced stan- dards will be considered to be in conformance, even though the edition reference may be changed in a subse- quent revision of the standard.
1.6 Quality Systems
Nonmandatory requirements relating to the manufac- turer ’s quality system program are described in Nonmandatory Appendix A.
1.7 Convention
For determining conformance with this Standard, the convention for fixing significant digits where limits (maximum and minimum values) are specified shall be as defined in ASTM E29. This requires that an observed or calculated value be rounded off to the nearest unit in the last right-hand digit used for expressing the limit. Decimal values and tolerances do not imply a particular method of measurement.
2 TRANSITION CONTOURS
Figure 1 delineates the maximum envelope in which transitions from welding bevel to the outer surface of the component and from the root face to the inner surface of the component must lie. Except as specified in Note (5) to Fig. 1, and as otherwise specified by the purchaser, the exact contour within this envelope is the manufacturer’s option, provided it maintains the specified minimum wall thickness, has no slopes steeper than those indi- cated for the respective regions, and includes the proper surface for backing rings if specified.
4.1 General
Preparation of the inside diameter at the end of a component shall be in accordance with one of the follow- ing, as specified by the purchaser: (a) Components to be welded without backing rings shall meet the requirements of the standard or specifica- tion for the component. (b) Components to be welded using split or noncon- tinuous backing rings shall be contoured with a cylindri- cal surface at the end as shown in Fig. 2, illustration (b) and Fig. 3, illustration (b). If the backing ring contour is other than rectangular, details must be furnished by the purchaser.