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ASME B31.3-2016 <br /> 311.2 Specific Requirements shall not be considered as contributing any strength to <br /> 311.2.1 Welds for Category D Fluid Service. Welds the joints. <br /> that meet the requirements of para. 311.1,but for which <br /> examination is in accordance with para. 341.4.2, and 312 FLANGED JOINTS <br /> acceptance criteria are those in Table 341.3.2 for Category 312.1 Joints Using Flanges of Different Ratings <br /> D Fluid Service, may be used only in that service. <br /> Where flanges of different ratings are bolted together, <br /> 311.2.2 Welds for Severe Cyclic Conditions. Welds the rating of the joint shall not exceed that of the lower <br /> for use under severe cyclic conditions shall meet the rated flange. Bolting torque shall be limited so that <br /> requirements of para. 311.1 with the exceptions that excessive loads will not be imposed on the lower rated <br /> examination shall be in accordance with para. 341.4.3, flange in obtaining a tight joint. <br /> and acceptance criteria shall be those in Table 341.3.2 <br /> for severe cyclic conditions. 312.2 Metal to Nonmetal Flanged Joints <br /> 311.2.3 Welds for Elevated Temperature Fluid Where a metallic flange is bolted to a nonmetallic <br /> Service. Weld joints for Elevated Temperature Fluid flange,both should be flat-faced. A full-faced gasket is <br /> Service shall meet the requirements for Normal Fluid preferred. If a gasket extending only to the inner edge <br /> Service, unless otherwise specified. of the bolts is used, bolting torque shall be limited so <br /> 311.2.4 Backing Rings and Consumable Inserts that the nonmetallic flange is not overloaded. <br /> (a) If a backing ring is used where the resulting crevice 312.3 Flanged Joint Assembly (16) <br /> is detrimental (e.g., subject to corrosion, vibration, or See para. 335.2.5. <br /> severe cyclic conditions),it should be removed and the <br /> internal joint face ground smooth.When it is impractical <br /> to remove the backing ring in such a case,consideration 313 EXPANDED JOINTS <br /> shall be given to welding without backing rings or to (a) Expanded joints shall not be used under severe <br /> the use of consumable inserts or removable nonmetallic cyclic conditions. For other services, adequate means <br /> backing rings. shall be provided to prevent separation of the joint. If <br /> (b) Split backing rings shall not be used under severe the fluid is toxic or damaging to human tissue, safe- <br /> cyclic conditions. guarding is required. <br /> 311.2.5 Socket Welds (b) Consideration shall be given to the tightness of <br /> (a) Socket welded joints (para. 328.5.2) should be expanded joints when subjected to vibration,differential <br /> avoided in any service where crevice corrosion or severe expansion or contraction due to temperature cycling,or <br /> erosion may occur. external mechanical loads. <br /> (b) Socket welded joints shall conform to the <br /> following: 314 THREADED JOINTS <br /> (1) Socket dimensions shall conform to ASME B16.5 <br /> for flanges and ASME B16.11 or MSS SP-119 for other 314.1 General <br /> socket-welding components. Threaded joints are suitable for Normal Fluid Service <br /> (2) Weld dimensions shall not be less than those except as stated elsewhere in para. 314. They may be <br /> shown in Figs. 328.5.2B and 328.5.2C. used under severe cyclic conditions only as provided in <br /> (c) Socket welds larger than DN 50 (NPS 2) shall not paras. 314.2.1(c) and 314.2.2. <br /> be used under severe cyclic conditions. (a) Threaded joints should be avoided in any service <br /> (d) A drain or bypass in a component maybe attached where crevice corrosion,severe erosion,or cyclic loading <br /> by socket welding,provided the socket dimensions con- may occur. <br /> form to Fig. 4 in ASME B16.5. (b) When threaded joints are intended to be seal <br /> 311.2.6 Fillet Welds welded, thread sealing compound shall not be used. <br /> (c) Layout of piping employing threaded joints <br /> (a) Fillet welds in accordance with para. 328.5.2 may <br /> should, insofar as possible, minimize stress on joints, <br /> e used as primary welds to attach socket welding com- <br /> b <br /> be use s and slip-on flanges. giving special consideration to stresses due to thermal <br /> ponentexpansion and operation of valves (particularly a valve <br /> (b) Fillet welds may also be used to attach reinforce- at a free end). Provision should be made to counteract <br /> ment and structural attachments, to supplement the forces that would tend to unscrew the joints. <br /> strength or reduce stress concentration of primary welds, (d) Except for specially designed joints employing <br /> and to prevent disassembly of joints. lens rings or similar gaskets,threaded flanges in which <br /> 311.2.7 Seal Welds. Seal welds (para. 328.5.3)may the pipe ends project through to serve as the gasket <br /> be used only to prevent leakage of threaded joints and surface may be used only for Category D Fluid Service. <br />