= (O.D. of saddle - Dob)tr
A6 = pressure design area expected at the end of service life
= (tmh - A)d1
Portions of the reinforcement area may be composed of materials other than those of the run pipe, but if the allowable stress of these materials is less than that for the run pipe, the corresponding calculated reinforcement area provided by this material shall be reduced in the ratio of the allowable stress being applied to the reinforcement area. No additional credit shall be taken for materials having higher allowable stress values than the run pipe.
(D.2.4) Reinforcement Zone. The reinforcement zone is a parallelogram whose width shall extend a distance d
2 on each side of the centerline of the branch pipe, and whose altitude shall start at the inside surface of the run pipe and extend to a distance L4 from the outside surface of the run pipe.
(D.2.5) Reinforcement of Multiple Openings. It is preferred that multiple branch openings be spaced so that their reinforcement zones do not overlap. If closer spacing is necessary, the following requirement shall be met. The two or more openings shall be reinforced in accordance with (D.2), with a combined reinforcement that has a strength equal to the combined strength of the reinforcement that would be required for the separate openings. No portion of the cross section shall be considered as applying to more than one opening, or be evaluated more than once in a combined area.
When more than two adjacent openings are to be provided with a combined reinforcement, the minimum distance between centers of any two of these openings should preferably be at least 1½ times their average diameter, and the area of reinforcement between them shall be at least equal to 50% of the total required for these two openings.
(D.2.6) Rings, Pads, and Saddles. Reinforcement provided in the form of rings, pads, or saddles shall not be appreciably narrower at the side than at the crotch.
A vent hole shall be provided at the ring, pad, or saddle to provide venting during welding and heat treatment. Refer to para. 127.4.8(E).
Rings, pads, or saddles may be made in more than one piece, provided the joints between pieces have full thickness welds, and each piece is provided with a vent hole.
(D.2.7) Other Designs. The adequacy of designs to which the reinforcement requirements of para. 104.3 cannot be applied shall be proven by burst or proof tests on scale models or on full size structures, or by calculations previously substantiated by successful service of similar design
(E) Branch Connections Subject to External Pressure Requiring Reinforcement. The reinforcement area in square inches (square millimeters) required for branch connections subject to external pressure shall be
0.5tmhd1 (2 - sin a)
where tmh is the required header wall thickness determined for straight pipe under external pressure, using procedures outlined in UG-28, UG-29, UG-30, and UG-31 of Section VIII, Division 1, of the ASME Boiler and Pressure Vessel Code.
Procedures established heretofore for connections subject to internal pressure shall apply for connections subject to external pressure provided that Doh, Dob, and tr are reduced to compensate for external corrosion, if required by design conditions.
(F) Branch Connections Subject to External Forces and Moments. The requirements of the preceding paragraphs are intended to assure safe performance of a branch connection subjected only to pressure. However, when external forces and moments are applied to a branch connection by thermal expansion and contraction, by dead weight of piping, valves, and fittings, covering and contents, or by earth settlement, the branch connection shall be analyzed considering the stress intensification factors as specified in Appendix D. Use of ribs, gussets, and clamps designed in accordance with para. 104.3.4 is permissible to stiffen the branch connection, but their areas cannot be counted as contributing to the required reinforcement area of the branch connection.
(G) Extruded Outlets Integrally Reinforced
(G.1) The following definitions, modifications, notations, and requirements are specifically applicable to extruded outlets. The designer shall make proper wall thickness allowances in order that the required minimum reinforcement is assured over the design life of the system.
(G.2) Definition. An extruded outlet header is defined as a header in which the extruded lip at the outlet has an altitude above the surface of the run which is equal to or greater than the radius of curvature of the external contoured portion of the outlet; i.e., ho = r
o. See nomenclature and Fig. 104.3.1(G).
(G.3) These rules apply only to cases where the axis of the outlet intersects and is perpendicular to the axis of the run. These rules do not apply to any nozzle in which additional nonintegral material is applied in the form of rings, pads, or saddles.
(G.4) The notation used herein is illustrated in Fig. 104.3.1(G). All dimensions are in inches (millimeters).
D = outside diameter of run
d = outside diameter of branch pipe
db = corroded internal diameter of branch pipe
dc = corroded internal diameter of extruded outlet measured at the level of the outside surface of the run
dr = corroded internal diameter of run
ho = height of the extruded lip. This must be equal to or greater than ro, except as shown in (G.4.2) below.
L8 = altitude of reinforcement zone
To = corroded finished thickness of extruded outlet measured at a height equal to ro above the outside surface of the run
tb - A = actual thickness of branch wall, not including corrosion allowance
th - A = actual thickness of run wall, not including the corrosion allowance
tmb - A = required thickness of branch pipe according to wall thickness eq. (3) or (3A) in para. 104.1.2(A), but not including any thickness for corrosion
tmh - A = required thickness of the run according to eq. (3) or (3A) in para. 104.1.2(A), but not including any allowance for corrosion
r1 = half width of reinforcement zone (equal to dc)
ro = radius of curvature of external contoured portion of outlet measured in the plane containing the axes of the run and branch. This is subject to the following limitations:
(G.4.1) Minimum Radius. This dimension shall not be less than 0.05d except that on branch diameters larger than NPS 30, it need not exceed 1.50 in. (38 mm).
(G.4.2) Maximum Radius. For outlet pipe sizes 6 in. (150 mm) nominal and larger, this dimension shall not exceed 0.l0d + 0.50 in. (0.l0d + 12.7 mm). For outlet pipe sizes less than NPS 6, this dimension shall be not greater than 1.25 in. (32 mm).
(G.4.3) When the external contour contains more than one radius, the radius of any arc sector of approximately 45 deg shall meet the requirements of (G.4.1) and (G.4.2) above. When the external contour has a continuously varying radius, the radius of curvature at every point on the contour shall meet the requirements of (G.4.1) and (G.4.2) above.
(G.4.4) Machining other than grinding for weld cleanup shall not be employed in order to meet the above requirements.
(G.5) Required Area. The required area is defined as
A7 = K (tmh - A) dc
where K shall be taken as follows.
For d/D greater than 0.60,
K = 1.00
For d/D greater than 0.15 and not exceeding 0.60,
K = 0.6 + 2/3 d/D
For d/D equal to or less than 0.15,
K = 0.70
The design must meet criteria that the reinforcement area defined in (G.6) below is not less than the required area.
(G.6) Reinforcement Area. The reinforcement area shall be the sum of areas
A1 + A2 + A4
as defined below.
(G.6.l) Area Al is the area lying within the reinforcement zone resulting from any excess thickness available in the run wall.
A1 = dc(tn – tmh)
(G.6.2) Area A2 is the area lying within the reinforcement zone resulting from any excess thickness available in the branch pipe wall.
A2 = 2L8(tb – tmh)
(G.6.3) Area A4 is the area lying within the reinforcement zone resulting from excess thickness available in the extruded outlet lip.
A4 = 2ro [To – (tb – A)]
(G.7) Reinforcement of Multiple Openings. It is preferred that multiple branch openings be spaced so that their reinforcement zones do not overlap. If closer spacing is necessary, the following requirements shall be met. The two or more openings shall be reinforced in accordance with (G) with a combined reinforcement that has a strength equal to the combined strength of the reinforcement that would be required for separate openings. No portion of the cross section shall be considered as applying to more than one opening, or be evaluated more than once in a combined area.
(G.8) In addition to the above, the manufacturer shall be responsible for establishing and marking on the section containing extruded outlets, the design pressure and temperature. The manufacturer's name or trademarks shall be marked on the section.
104.3.3 Miters. Miter joints, and the terminology related thereto, are described in Appendix D. A widely spaced miter with
shall be considered to be equivalent to a girth buttwelded joint, and the rules of this paragraph do not apply. Miter joints, and fabricated pipe bends consisting of segments of straight pipe welded together, with q equal to or greater than this calculated value may be used within the limitations described below.
(A) Pressure shall be limited to 10 psi (70 kPa) under the following conditions:
(A.1) The assembly includes a miter weld with
q > 22.5 deg, or contains a segment which has a dimension
B < 6tn
(A.2) The thickness of each segment of the miter is not less than that determined in accordance with para. 104.1.
(A.3) The contained fluid is nonflammable, non-toxic, and incompressible, except for gaseous vents to atmosphere.
(A.4) The number of full pressure cycles is less than 7,000 during the expected lifetime of the piping system.
(A.5) Full penetration welds are used in joining miter segments.
(B) Pressure shall be limited to 100 psi (700 kPa) under the conditions defined in (A.2), (A.3), (A.4), and (A.5) above, in addition to the following:
(B.1) the angle q does not exceed 22.5 deg
(B.2) the assembly does not contain any segment which has a dimension
B < 6tn
(C) Miters to be used in other services or at design pressures above 100 psi (700 kPa) shall meet the requirements of para. 104.7.
(C.1) When justification under para. 104.7 is based on comparable service conditions, such conditions must be established as comparable with respect to cyclic as well as static loadings.
(C.2) When justification under para. 104.7 is based on an analysis, that analysis and substantiating tests shall consider the discontinuity stresses which exist at the juncture between segments; both for static (including brittle fracture) and cyclic internal pressure.
(C.3) The wall thickness, ts, of a segment of a miter shall not be less than specified in (C.3.1) or (C.3.2) below, depending on the spacing.
(C.3.1) For closely spaced miter bends (see Appendix D for definition)
(C.3.2) For widely spaced miters (see Appendix D for definition)
(The above equation requires an iterative or quadratic solution for ts.)
104.3.4 Attachments. External and internal attachments to piping shall be designed so as not to cause flattening of the pipe, excessive localized bending stresses, or harmful thermal gradients in the pipe wall. It is important that such attachments be designed to minimize stress concentrations in applications where the number of stress cycles, due either to pressure or thermal effect, is relatively large for the expected life of the equipment.
104.4 Closures
