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ASME B31.3-2016 K308.2 Specific Flanges K311.2 Specific Requirements K308.2.1 Threaded Flanges. Threaded flanges may K311.2.1 Backing Rings and Consumable Inserts. be used only within the limitations on threaded joints Backing rings shall not be used. Consumable inserts in para. K314. shall not be used in butt welded joints except when K308.2.2 Other Flange Types. Slip-on,socket weld- specified by the engineering design. ing, and expanded joint flanges, and flanges for flared K311.2.2 Fillet Welds. Fillet welds may be used laps, are not permitted. only for structural attachments in accordance with the K308.3 Flange Facings requirements of paras. K321 and K328.5.2. The flange facing shall be suitable for the service and K311.2.3 Other Weld Types. Socket welds and seal for the gasket and bolting employed. welds are not permitted. K308.4 Gaskets K312 FLANGED JOINTS Gaskets shall be selected so that the required seating Flanged joints shall be selected for leak tightness,con- load is compatible with the flange rating and facing,the strength of the flange, and its bolting. Materials shall sidering the requirements of para. K308, flange facing b finish, and method of attachment. See also para. F312. e suitable for the service conditions. Mode of gasket failure shall be considered in gasket selection and joint K312.1 Joints Using Flanges of Different Ratings design. Paragraph 312.1 applies. K308.5 Blanks Blanks shall have a marking, identifying material, K313 EXPANDED JOINTS pressure—temperature rating, and size, that is visible after installation. Expanded joints are not permitted. K309 BOLTING K314 THREADED JOINTS Bolting,including bolts,bolt studs,studs,cap screws, K314.1 General nuts, and washers, shall meet the requirements of the Except as provided in paras. K314.2 and K314.3, BPV Code, Section VIII, Division 2, Part 3, para. 3.7; threaded joints are not permitted. Part 4, para. 4.16; and Part 5, para. 5.7. See also (a) Layout of piping shall be such as to minimize Appendix F,para. F309, of this Code. strain on threaded joints that could adversely affect sealing. PART 4 (b) Supports shall be designed to control or minimize FLUID SERVICE REQUIREMENTS FOR PIPING JOINTS strain and vibration on threaded joints and seals. K310 GENERAL K314.2 Taper-Threaded Joints Joints shall be suitable for the fluid handled, and for (a) Taper-threaded joints shall be used only for instru- the pressure—temperature and other mechanical load- mentation,vents,drains,and similar purposes,and shall ings expected in service. be not larger than DN 15 (NPS %). Factors such as assembly and disassembly(if applica- (b) External-threaded components shall be at least ble),cyclic loading,vibration,shock,bending,and ther- Schedule 160 in nominal wall thickness. The nominal mal expansion and contraction of joints shall be thickness of Schedule 160 piping is listed in considered in the engineering design. ASME B36.10M for DN 15 (NPS 1/2)and in ASME B16.11 for sizes smaller than DN 15 (NPS K311 WELDED JOINTS K314.3 Straight-Threaded Joints K311.1 General K314.3.1 Joints With Seal Formed by Projecting Welds shall conform to the following: Pipe. Threaded joints where the threads are used to (a) Welding shall be in accordance with para. K328. attach flanges or fittings, and in which the pipe end (b) Preheating and heat treatment shall be in accor- projects through the flange or fitting and is machined dance with paras. K330 and K331,respectively. to form the sealing surface with a lens ring, cone ring, (c) Examination shall be in accordance with the mating pipe end, or other similar sealing device, para. K341.4, with acceptance criteria as shown in may be used.Such joints shall be qualified in accordance Table K341.3.2. with para. K304.7.2(a) or (b).