New York Codes, Rules and Regulations › Title 16 - DEPARTMENT OF PUBLIC SERVICE › Appendices › Appendix 14-C

Current through Register Vol. 46, No. 28, July 10, 2024
END PREPARATION FOR BUTT WELDING SECTIONS HAVING UNEQUAL
THICKNESSES AND UNEQUAL SPECIFIED YIELD STRENGTHS
Explanatory Notes
General
1. The
			 sketches in Figure 523-B illustrate acceptable preparations for joining pipe
			 ends by butt welding for materials having unequal wall thicknesses and/or with
			 unequal strengths (minimum specified yield strength).
2. The thickness of the sections to be
			 joined, beyond the joint design area, shall comply with the design requirements
			 of this Part.
3. When the minimum
			 specified yield strengths of the sections to be joined are unequal, the
			 deposited weld metal shall have mechanical properties at least equal to those
			 of the section having the higher strength.
4. The transition between ends of unequal
			 thickness may be accomplished by taper or welding as illustrated or by means of
			 a prefabricated transition ring.
5.
			 Sharp notches or grooves at the edge of the weld where it joins a slanted
			 surface shall be avoided.
6. For
			 joining unequal thicknesses of equal specified yield strengths, the rules given
			 herein apply, except there is no minimum angle limit to the taper.
7. THE MAXIMUM THICKNESS t
			 d FOR DESIGN PURPOSES SHALL NOT BE GREATER THAN 1.5t.
Internal Diameters Unequal
A. For piping to operate at hoop stresses of
			 less than 20 percent of specified minimum yield strength, if the nominal wall
			 thicknesses of the adjoining ends do not vary more than 1/8 -inch, no special
			 treatment is necessary provided adequate penetration and bond is accomplished
			 in welding. If the offset is greater than 1/8-inch the following paragraphs
			 will apply.
FOR STRESS LEVELS ABOVE 20 PERCENT OF THE MINIMUM SPECIFIED
				YIELD STRENGTH.
B. If the
			 nominal wall thicknesses of the adjoining ends do not vary more than 3/32 inch,
			 no special treatment is necessary provided full penetration and bond is
			 accomplished in welding. See sketch (a).
C. Where the nominal internal offset is more
			 than 3/32inch and there is no access to the inside of the pipe for welding, the
			 transition must be made by a taper cut on the inside end of the thicker
			 section. See sketch (b). The taper angle shall not be steeper than 30 deg. nor
			 less than 14 deg.
D. Where the
			 nominal internal offset is more than 3/32 inch, but does not exceed 1/2 the
			 thinner section, and there is access to the inside of the pipe for welding, the
			 transition may be made with a tapered weld as shown in sketch (c). The land on
			 the thicker section must be equal to the offset plus the land on abutting
			 section.
E. Where the nominal
			 internal offset is more than 1/2 the thinner section, and there is access to
			 the inside of the pipe for welding, the transition may be made with a taper cut
			 on the inside end of the thicker section as shown in sketch (b), or by a
			 combination taper weld to 1/2 the thinner section and a taper cut from that
			 point as shown in sketch (d).
External Diameters Unequal
F. Where the external offset does not exceed
			 1/2 the thinner section, the transition may be made by welding as shown by
			 sketch (e), provided the angle of rise of the weld surface does not exceed 30
			 deg. and both bevel edges are properly fused.
G. Where there is an external offset
			 exceeding 1/2 the thinner section, that portion of the offset over 1/2t shall
			 be tapered as shown in sketch (f).
Internal and External Diameters Unequal
H. Where there is both an internal and an
			 external offset, the joint design shall be a combination of sketch (a to f,
			 i.e., Fig. g). Particular attention must be paid to proper alignment under
			 these conditions.
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