ASME B16.25-2017 pdf download
ASME B16.25-2017 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 processes 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 equivalents; 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.
1.5 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 references. Instead, the specific edition reference is iden- tified in Mandatory Appendix II. A product made in confor- mance with a prior edition of referenced standards will be considered to be in conformance, even though the edition reference may be changed in a subsequent 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 Figure 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
4.3 Exceptions (a) For pipe or tubing varying from the ASTM A106 and A335 types, having different wall thickness and/or outside diameter tolerances (such as forged and bored pipe), the foregoing equations may be inapplicable. Equations (1) and (2) may be used to determine C for these applications. The purchaser shall specify the C dimension when Tables 1 and I-1 data do not apply. (b) For components in smaller sizes and lower sched- ule numbers, it may be necessary to deposit weld metal on the inside diameter (I.D.) or use thicker wall materials in order to machine the backing ring while maintaining required wall thickness. This condition may also arise when using material whose nominal dimensions indicate sufficient metal but whose actual I.D., considering toler- ances, is large enough to require additional metal. 5 TOLERANCES See Figures 2, 3, 5, and 6. 5.1 Dimension B Values for the I.D. at the welding end [see dimension B, Figure 2, illustrations (a) and (b) and Figure 3, illustrations (a) and (b)] shall be as specified in the applicable standard or specification for the component. 5.2 Welding Bevels, Root Face, and Dimension C Values of welding bevels, root face, and dimension C shall be as indicated in Figures 2 through 6.
