(a) Scope.

(1) This section contains requirements for pressure vessels and nonpressure vessel type tanks and associated secondary barrier, as defined in §38.05-4 and §154.7 of this chapter, and their parts constructed of carbon and alloy steels which are stressed at operating or hydrostatic test temperatures below 0 °F.

(2) The service temperature is the minimum temperature of a product at which it may be contained, loaded and/or transported. However, the service temperature shall in no case be taken higher than given by the following formula:

ts = tw−0.25(tw−tB)

Only temperatures due to refrigerated service usually need to be considered in determining the service temperature, except pressure vessel type cargo tanks operating at ambient temperatures must meet paragraph (d) of this section. “Refrigerated service”, as used in this paragraph, means a service in which the temperature is controlled by the process and not by atmospheric conditions.

(b) Specifications. Materials used in the construction of vessels to operate below 0 °F. (but not below the designated minimum service temperature) shall conform to a specification given in table UCS-23 in section VIII of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 54.01-1) and the following additional requirements:

(1)

(i) For minimum service temperatures not lower than −67 °F., ferritic steels shall be made with fine grain practice and shall have an austenitic grain size of 5 or finer, and shall be normalized. Consideration will be given to other heat treatments. Refer to §57.03-1(d) of this subchapter. Plate for pressure vessel applications shall conform to the requirements of ASTM A 20 (incorporated by reference, see §54.01-1). It may be produced by the open hearth, basic oxygen or electric furnace process and shall conform to the requirements of table 54.25-10(b)(1). (Other alloying elements may only be present in trace amounts.)

(ii) Mechanical properties shall be within the following limits:

(2) For minimum service temperature below −67 °F., but not below the designated minimum service temperature, ferritic steels shall be normalized, low carbon, fully killed, fine grain, nickel alloy type, conforming to any one of the specifications in table 54.25-10(b)(2). Consideration will be given to other heat treatments. Refer to §57.03-1(d) of this subchapter for quenched and tempered steels. The ultimate and yield strengths shall be as shown in the applicable specification and shall be suitable to the design stress levels adopted. The service temperature shall not be colder than the minimum specified in table 54.25-10(b)(2) for each steel.

(3) The materials permitted under paragraphs (b) (1) and (2) of this section shall be tested for toughness in accordance with and shall satisfy the applicable requirements of subpart 54.05.

(4) Welded pressure vessels or nonpressure vessel type tanks and associated secondary barriers, as defined in §38.05-4 of subchapter D (Tank Vessels) of this chapter shall meet the toughness requirements of subparts 57.03 and 57.06 of this subchapter with regard to weld procedure qualifications and production testing.

(5) The material manufacturer's identification marking required by the material specification shall not be die-stamped on plate material less than one-fourth inch in thickness.

(c) Design. Pressure vessels must meet the requirements for Class I-L and II-L construction. (See table 54.01-5(b) for applicable requirements). Except as permitted by §54.05-30, the allowable stress values used in the design of low temperature pressure vessels may not exceed those given in table UCS-23 of section VIII of the ASME Boiler and Pressure Vessel Code for temperatures of 0 °F. to 650 °F. For materials not listed in this table allowable stress values are determined in accordance with appendix P of section VIII of the ASME Boiler and Pressure Vessel Code.

(d) Weldments and all materials used in pressure vessel type cargo tanks operating at ambient temperatures and constructed of materials listed in table UCS-23 must pass Charpy impact tests in accordance with UG-84 at a temperature of −20 °F or colder, except as provided by paragraphs (d)(1), (d)(2), and (d)(3) of this section.

(1) Charpy impact tests are not required for any of the following ASTM materials if the thickness for each is 5⁄8 inch or less, unless otherwise indicated:

(i) A-182, normalized and tempered.

(ii) A-302, Grades C and D.

(iii) A-336, Grades F21 and F22 that are normalized and tempered.

(iv) A-387, Grades 21 and 22 that are normalized and tempered.

(v) A-516, Grades 55 and 60.

(vi) A-533, Grades B and C.

(vii) All other plates, structural shapes and bars, and other product forms, except for bolting, if produced to a fine grain practice and normalized.

(2) Charpy impact tests are not required for any of the following ASTM materials if the thickness for each is 11⁄4 inch or less:

(i) A-203.

(ii) A-508, Class 1.

(iii) A-516, normalized.

(iv) A-524.

(v) A-537.

(vi) A-612, normalized.

(vii) A-662, normalized.

(viii) A-724, normalized.

(3) Charpy impact tests are not required for any of the following bolt materials:

(i) A-193, Grades B5, B7, B7M, and B16.

(ii) A-307, Grade B

(iii) A-325, Type 1.

(iv) A-449.

[CGFR 68-82, 33 FR 18828, Dec. 18, 1968, as amended by CGFR 69-127, 35 FR 9977, June 17, 1970; CGD 73-133R, 39 FR 9178, Mar. 8, 1974; CGD 74-289, 44 FR 26007, May 3, 1979; CGD 77-069, 52 FR 31626, Aug. 21, 1987; CGD 85-061, 54 FR 50964, Dec. 11, 1989; USCG-1999-5151, 64 FR 67178, Dec. 1, 1999; USCG-2000-7790, 65 FR 58460, Sept. 29, 2000; USCG-2003-16630, 73 FR 65170, Oct. 31, 2008]