ASME B16.25:2017 pdf download

ASME B16.25:2017 pdf download ButtweldingEnds
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 conformance 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 steeper than those indicated for the respective regions,and includes the proper surface for backing rings ifspecified.
3 WELDING BEVEL DESIGN
3.1 Bevels for Other Than GTAW Root Pass
(a) Components having nominal wall thicknesses of 3mm (0.12 in.) and less shall have ends cut square orslightly chamfered.
b) Components having nominal wall thicknesses over3 mm (o.12 in.) to 22 mm (0.88 in.) inclusive shall havesingle angle bevels as illustrated in Figure 2.
(c) Components having nominal wall thicknessesgreater than 22 mm (0.88 in.) shall have compoundangle bevels as illustrated in Figure 3.
3.2 Bevels for GTAW Root Pass
(a) Components having nominal wall thicknesses of 3mm (0.12 in.J and less shall have ends cut square orslightly chamfered.
(b) Components having nominal wall thicknesses over3 mm (0.12 in.) to 10 mm (0.38 in.) inclusive shall have371-deg ± 212-deg bevels or slightly concave bevels (seeFigure 4).
(c) Components having nominal wall thicknesses over10 mm (0.38 in.) to 25 mm (1.0 in.) inclusive shall havebevels as shown in Figure 5.
(d) Components having nominal wall thicknessesgreater than 25 mm ( 1.0 in.] shall have bevels asshown in Figure6.
3.3 Outside Diameter at Welding Ends
Dimension A shall be either that specified in the applic-able component standard or that specified in the purcha-ser”s component specification. In the absence of a
requirement for dimension A in a component standardor a purchaser’s specification, the values for dimension
A in Table 1 or Table l-1 may be used.
4 PREPARATION OF INSIDE DIAMETER OFWELDING END
4.1 General
Preparation of the inside diameter at the end of acomponent shall be in accordance with one of thefollowing, as specified by the purchaser:
(a) components to be welded without backing ringsshall meet the requirements of the standard or specifica-
tion for thecomponent.
(b] Components to be welded using split or noncontin-uous backing rings shall be contoured with a cylindricalsurface at the end as shown in Figure 2, illustration (b) andFigure 3, llustration (b). If the backing ring contour is other than rectangular, details must be furnished by thepurchaser.
(c] Components to be welded using solid or continuousbacking rings shall be contoured with a cylindrical ortapered surface at the end as specified by the purchaser.End preparation is illustrated in Figure 2, illustration (c)and Figure 3, illustration (c) for rectangular ends and inFigure 2, illustration (d) and Figure 3, illustration (d) fortapered ends.
(dy Components to be welded using consumable insertrings or GTAw root pass shall be contoured with a cylin-drical surface at the end as shown in Figures 4 through 6.4.2 Dimension c
Values for dimension C shown in Figure 2, illustrations(c)and (d); Figure 3,illustrations (c) and (d); and Figures 5and 6 can be determined by the following equations:(sl Units)
c= A -o.D. tolerance – 2 ×tmin – 0.25(1(u.s. Customary Units)
c- A – 0.D. tolerance – 2 ×tmin – 0.010(2]where
A = specified outside pipe diameter atwelding end (see para.3.3)
o.D. tolerance = undertolerance on the pipe o.D. from
the applicable piping specificationLmin = t – manufacturing tolerance for pipe
wall thickness per applicable pipespecification, mm (in.)
t = nominal wall thickness of pipe, mm
(in.)
0.25 (0.010)= plus machining tolerance on bore c,
mm (in.J
Based on tolerances specific to ASTM A106[50 ≤ DN ≤1200 (2≤ NPS≤48)] and A335 [50≤ DN ≤300 (2≤ NPS≤12)] pipe, including an undertolerance on wall thickness of12.5%o,eqs. ([1) and (2) can be defined as follows:
(Sl Units)
c = A – 0.79- 2×0.875t- 0.25
(U.S. Customary Units)
C=A – 0.031- 2×0.875t – 0.010
Tables 1 and l-1 list the Cvalues for pipe with an under-tolerance on A of 0.79 mm (0.031 in.) and 12.5% on wallthickness for DN 50 to DN 1500 (NPs 2 to NPS 60) pipe.Anundertolerance on A of 0.4 mm (0.015 in.) and wall thick-ness of 12.5% was used for DN 40 (NPS 11/z) and smallerpipe.For pipe with an A or pipe wall thickness underto-lerance other than the above, do not use the C data fromTables 1 and l-1 [see para.4.3(a]].