Section 56.15-1 - Pipe joining fittings(a) Pipe joining fittings meeting the standards specified in this part and certified in accordance with subpart 50.25 of this subchapter are acceptable for use in piping systems.(b) Threaded, flanged, socket-welding, butt-welding, and socket-brazing pipe joining fittings, made in accordance with the applicable standards in tables 1 and 2 to § 56.60-1 and of materials complying with subpart 56.60, may be used in piping systems within the material, size, pressure, and temperature limitations of those standards and within any further limitations specified in this subchapter. Fittings must be designed for the maximum pressure to which they may be subjected, but in no case less than 50 psig.(c) Pipe joining fittings not accepted for use in piping systems in accordance with paragraph (b) of this section must meet the following:(1) All pressure-containing materials must be accepted in accordance with § 56.60-1 .(2) The maximum allowable working pressure may be determined by-(i) Calculations comparable to those of ASME B31.1 (incorporated by reference; see § 56.01-2 ) or Section VIII of the ASME BPVC (incorporated by reference; see § 56.01-2 );(ii) Subjecting a representative model to a proof test or experimental stress analysis described in paragraph A-22 of Section I of the ASME BPVC (incorporated by reference; see § 56.01-2 ); or(iii) Other means specifically accepted by the Marine Safety Center.(3) Fittings must be tested in accordance with § 56.97-5 .(4) If welded, fittings must be welded in accordance with subpart 56.70 and part 57 of this chapter or by other processes specifically approved by the Marine Safety Center. In addition, for fittings to be accepted for use in piping systems in accordance with this paragraph, the following requirements must be met: (i) For fittings sized three inches and below-(A) The longitudinal joints must be fabricated by either gas or arc welding;(B) One fitting of each size from each lot of 100 or fraction thereof must be flattened cold until the opposite walls meet without the weld developing any cracks;(C) One fitting of each size from each lot of 100 or fraction thereof must be hydrostatically tested to the pressure required for a seamless drawn pipe of the same size and thickness produced from equivalent strength material, as determined by the applicable pipe material specification; and(D) If a fitting fails to meet the test in paragraph (c)(4)(i)(B) or (C) of this section, no fitting in the lot from which the test fitting was chosen is acceptable.(ii) For fittings sized above three inches-(A) The longitudinal joints must be fabricated by arc welding;(B) For pressures exceeding 150 psig, each fitting must be radiographically examined as specified in Section VIII of the ASME BPVC;(C) For pressures not exceeding 150 psig, the first fitting from each size in each lot of 20 or fraction thereof must be examined by radiography to ensure that the welds are of acceptable quality;(D) One fitting of each size from each lot of 100 or fraction thereof must be hydrostatically tested to the pressure required for a seamless drawn pipe of the same size and thickness produced from equivalent strength material, as determined by the applicable pipe material specification; and(E) If a fitting fails to meet the test in paragraph (c)(4)(ii)(C) or (D) of this section, no fitting in the lot from which the test fitting was chosen is acceptable. (d) Single welded butt joints without the use of backing strips may be employed in the fabrication of pipe joining fittings of welded construction provided radiographic examination indicates that complete penetration is obtained.(e) Each pipe joining fitting must be marked in accordance with MSS SP-25 (incorporated by reference; see § 56.01-2 ).CGFR 68-82, 33 FR 18843, Dec. 18, 1968, as amended by USCG-2003-16630, 73 FR 65176 , Oct. 31, 2008