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ASME B31.3-2016 Table 314.2.1 Minimum Thickness of 315 TUBING JOINTS External Threaded Components 315.1 General Notch- Size Range Min.Wall [Note(1)] In selecting and applying flared, flareless, and com- Fluid Sensitive Thickness pression type tubing fittings,the designer shall consider Service Material DN NPS [Note (2)] the possible adverse effects on the joints of such factors Normal Yes [Note (3)] <40 s1'/' Sch. 80 as assembly and disassembly,cyclic loading,vibration, 50 2 Sch. 40 shock, and thermal expansion and contraction. 65-150 2'/z-6 Sch. 40 315.2 Joints Conforming to Listed Standards Normal No [Note (4)] <50 <2 Sch. 40S 65-150 2'/z-6 Sch. 40S Joints using flared,flareless,or compression type tub- ing fittings covered by listed standards may be used in Category D Either <300 <12 In accordance Normal Fluid Service provided that with para. (a) the fittings and joints are suitable for the tubing 304.1.1 with which they are to be used (considering maximum and minimum wall thickness) and are used within the GENERAL NOTE: Use the greater of para.304.1.1 or thickness shown pressure—temperature limitations of the fitting and the in this Table. NOTES: joint (1) For sizes>DN 50 (NPS 2), the joint shall be safeguarded (see (b) the joints are safeguarded when used under severe Appendix G) for a fluid service that is flammable,toxic, or dam- cyclic conditions aging to human tissue. (2) Nominal wall thicknesses is listed for Sch. 40 and 80 in 315.3 Joints Not Conforming to Listed Standards ASME B36.10M and for Sch. 40S in ASME 1336.19M. Joints using flared,flareless,or compression type tub- (3) For example, carbon steel. ing fittings not listed in Table 326.1 may be used in (4) For example, austenitic stainless steel. accordance with para. 315.2 provided that the type of fitting selected is also adequate for pressure and other loadings. The design shall be qualified as required by para. 304.7.2. 314.2 Specific Requirements 316 CAULKED JOINTS 314.2.1 Taper-Threaded Joints. Requirements in (a) Caulked joints such as bell type joints shall be limited through (c) below apply to joints in which the threads to Category D Fluid Service and to a temperature not of both mating components conform to ASME B1.20.1. over 93°C (200°F). They shall be used within the pres- (a) External threaded components may be used in sure—temperature limitations of the joint and pipe. Pro- accordance with Table 314.2.1 and its Notes. visions shall be made to prevent disengagement of joints, (b) Internal threaded components shall be at least to prevent buckling of the piping,and to sustain lateral equivalent in strength and toughness to threaded com- reactions produced by branch connections or other ponents listed in Table 326.1 and otherwise suitable for causes. the service. (c) Threaded components of a specialty nature that 317 SOLDERED AND BRAZED JOINTS are not subject to external moment loading, such as 317.1 Soldered Joints thermometer wells, may be used under severe cyclic conditions. Soldered joints shall be made in accordance with the (d) A coupling having straight threads may be used provisions of para. 333 and may be used only in only for Category D Fluid Service,and only with taper- Category D fluid service. Fillet joints made with solder threaded mating components. metal are not permitted.The low melting point of solder shall be considered where possible exposure to fire or 314.2.2 Straight-Threaded Joints. Threaded joints elevated temperature is involved. in which the tightness of the joint is provided by a seating surface other than the threads(e.g.,a union com- 317.2 Brazed and Braze Welded Joints prising male and female ends joined with a threaded (a) Brazed and braze welded joints made in accor- union nut, or other constructions shown typically in dance with the provisions in para. 333 are suitable for Fig. 335.3.3) may be used. If such joints are used under Normal Fluid Service.They shall be safeguarded in fluid severe cyclic conditions and are subject to external services that are flammable, toxic, or damaging to moment loadings, safeguarding is required. human tissue.They shall not be used under severe cyclic