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ASME B31.3-2016 provided the size of the branch does not exceed DN 50 when the branch does not intersect the longitu- (NPS 2)nor one-fourth the nominal size of the run. The dinal weld of the run,the basic allowable stress, minimum wall thickness of the coupling anywhere in S, for the pipe may be used in determining the reinforcement zone (if threads are in the zone,wall th for the purpose of reinforcement calculation thickness is measured from root of thread to minimum only.When the branch does intersect the longi- outside diameter) shall be not less than that of the tudinal weld of the run, the product SEW (of unthreaded branch pipe. In no case shall a coupling the stress value, S; the appropriate weld joint or half coupling have a rating less than Class 3000 in quality factor,Ej,from Table A-113;and the weld accordance with ASME 1316.11. joint strength reduction factor, W; see (c) the branch connection utilizes an unlisted branch para. 302.3.5) for the run pipe shall be used in connection fitting (see para. 300.2),provided the fitting the calculation.The product SEW of the branch is made from materials listed in Table A-1 or Table A-IM shall be used in calculating tb. and provided that the branch connection is qualified as 6 = smaller angle between axes of branch and run required by para. 304.7.2. (b) Required Reinforcement Area. The reinforcement (16) 304.3.3 Reinforcement of Welded Branch area,&required for a branch connection under internal Connections. Added reinforcement is required to meet pressure is the criteria in paras. 304.3.3(b) and (c) when it is not inherent in the components of the branch connection. Ai = thdi(2 -sin 8) (6) Sample problems illustrating the calculations for branch reinforcement are shown in Appendix H. For a branch connection under external pressure, area (a) Nomenclature. The nomenclature below is used in Ai is one-half the area calculated by eq. (6),using as th the pressure design of branch connections. It is illus- the thickness required for external pressure. trated in Fig.304.3.3,which does not indicate details for (c) Available Area. The area available for reinforce- construction or welding. Some of the terms defined in ment is defined as Appendix J are subject to further definitions or varia- tions, as follows: Az +A3 +A4>-Ai (6a) b = subscript referring to branch di = effective length removed from pipe at branch. These areas are all within the reinforcement zone and For branch intersections where the branch are further defined below. opening is a projection of the branch pipe inside (1) Area Az is the area resulting from excess thick- diameter (e.g.,pipe-to-pipe fabricated branch), ness in the run pipe wall di = [Db - 2(Tb - c)]/sin d2 = "half width" of reinforcement zone Az = (2dz -di)(Th-th-c) (7) = di or (Tb - c) + (Th - c) + d1/2, whichever is (2) Area A3 is the area resulting from excess thick- greater,but in any case not more than Dh ness in the branch pipe wall h = subscript referring to run or header L4 = height of reinforcement zone outside of run A3 = 2L4(Tb-tb-c)/sin(3 (8) pipe = 2.5(Th - c) or 2.5(Tb - c) + T„whichever is less If the allowable stress for the branch pipe wall is less Tb = branch pipe thickness (measured or minimum than that for the run pipe, its calculated area must be in accordance with the purchase specification) reduced in the ratio of allowable stress values of the except for branch connection fittings (see branch to the run in determining its contributions to para. 300.2). For such connections the value of area A3. Tb for use in calculating L4i d2, and A3 is the (3) Area A4 is the area of other metal provided by thickness of the reinforcing barrel (minimum welds and properly attached reinforcement. [See per purchase specification), provided that the para. 304.3.3(f).] Weld areas shall be based on the mini- barrel thickness is uniform (see Fig. K328.5.4) mum dimensions specified in para. 328.5.4,except that and extends at least to the L4 limit (see larger dimensions may be used if the welder has been Fig. 304.3.3). specifically instructed to make the welds to those T, = minimum thickness of reinforcing ring or sad- dimensions. dle made from pipe (use nominal thickness if (d) Reinforcement Zone. The reinforcement zone is a made from plate) parallelogram whose length extends a distance, d2, on = 0,if there is no reinforcing ring or saddle each side of the centerline of the branch pipe and whose t = pressure design thickness of pipe, according width starts at the inside surface of the run pipe (in its to the appropriate wall thickness equation or corroded condition) and extends beyond the outside procedure in para. 304.1. For welded pipe, surface of the run pipe a perpendicular distance, L4.