ASME B16.25:2017 pdf download.BUTTWELDING ENDS.
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 1-1 data do not apply.
(b) For components in smaller sizes and lower schedule 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 sufilcient metal but whose actual l.D., considering tolerances, is large enough to require additional metal.
5 TOLERANCES
See Figures 2, 3, 5, and 6.
5.1 Dimension B
Values for the ID. 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 ot welding bevels, root face, and dimension C shall be as indicated in Figures 2 through 6.
Large diameter pipe and fittings with a relatively thin wall have a tendency to spring out-of-round after removal from the machining fixture. For this reason, the measured diameters may vary with orientation. A tolerance of +0.25 mm (+0.0 10 in.) applies to the average C diameter in Figures 2 and 3, illustrations (c) and (d). A tolerance of +0.25 mm, —1.02 mm (+0.0 10 in., —0.040 in.) applies to the average C diameter for Figures 5 and 6.
5.4 WaLL Thickness
The maximum thickness at the end of the component is
(a) greater of t, + 4 mm (0.16 in.) or l.lSt, when ordered on a minimum wall basis.
(b) greater of tmin + 4 mm (0.16 in.) or 1.10 times the nominal wall thickness when ordered on a nominal wall basis. See ASME B36.1OM and ASME B36.19M for a tabulation of nominal wall thicknesses.
The minimum thickness, tmin, shall be as specified in the applicable standard or specification for the component (see Figure 1).ASME B16.25 pdf download.