1. (a) This part contains requirements for pressure vessels. Table 1 to § 54.01-5 gives a breakdown by parts in this subchapter of the regulations governing various types of pressure vessels, boilers, and thermal units.
2. (b) Pressure vessels are divided into Classes I, I-L (low temperature), II, II-L (low temperature), and III. Table 2 to § 54.01-5 describes these classes and sets out additional requirements for welded pressure vessels.

3. (c) The requirements for pressure vessels by class are as follows:

   1. (1) Class I-L and II-L pressure vessels must meet the applicable requirements in this part.
   2. (2) Pressure vessels containing hazardous materials as defined in § 150.115 of this chapter must meet the requirements of this part or, as applicable, the requirements in 49 CFR parts 171-177, or part 64 of this subchapter.
   3. (3) Except as provided in paragraph (c)(4) of this section, Classes I, II, and III pressure vessels not containing hazardous materials must be designed and constructed in accordance with the requirements in Section VIII of the ASME BPVC (incorporated by reference; see § 54.01-1) and must be stamped with the ASME “U” symbol. These pressure vessels must also comply with the requirements that are listed or prescribed in paragraphs (d) through (g) of this section. Compliance with other provisions in this part is not required.
   4. (4) Classes II and III pressure vessels that have a net internal volume of less than 0.14 cubic meters (5 cubic feet) and do not contain hazardous materials must be stamped with either the ASME “U” or “UM” symbol. Compliance with other provisions in this part is not required.

4. (d) Pressure vessels described in paragraph (c)(3) of this section must—

   1. (1) Have detailed plans that include the information required by § 54.01-18;
   2. (2) Meet §§ 54.01-35, 54.20-3(c), and 54.25-3;
   3. (3) Have pressure relief devices required by subpart 54.15;
   4. (4) Meet the applicable requirements in §§ 54.10-3, 54.10-20, and 54.10-25 for inspection, reports, and stamping;
   5. (5) If welded, meet the post weld heat treatment and minimum joint and radiography requirement in table 2 to § 54.01-5; and
   6. (6) If a steam generating pressure vessel, meet § 54.01-10.
5. (e) The plans required by paragraph (d)(1) of this section must be certified by a registered professional engineer to meet the design requirements in paragraph (d) of this section and in Section VIII of the ASME BPVC. The certification must appear on all drawings and analyses. The plans must be made available to the Coast Guard prior to the inspection required by § 54.10-3(c).
6. (f) If a pressure vessel has more than one independent chamber and the chambers have different classifications, each chamber must, as a minimum, meet the requirements for its classification. If a single classification for the entire pressure vessel is preferred, the classification selected must be one that is required to meet all of the regulations applicable to the classification that is not selected. For example, if one chamber is Class I and one chamber is Class II-L, the only single classification that can be selected is Class I-L.

7. (g) The design pressure for each interface between two chambers in a multichambered pressure vessel must be—

   1. (1) The maximum allowable working pressure (gauge) in the chamber with the higher pressure; or

   2. (2) If one chamber is a vacuum chamber, the maximum allowable working pressure (absolute) in the other chamber minus the least operating pressure (absolute) in the vacuum chamber.

      Table 1 to § 54.01-5—Regulation Reference for Boilers, Pressure Vessels, and Thermal Units

      Service and pressure temperature boundaries	Part of subchapterregulatingmechanicaldesign	Part of subchapterregulatingautomaticcontrol
      Main (power) boiler: All	52	62
      Pressure vessel: All	54	NA
      Fired auxiliary boiler 1 (combustion products or electricity):
      (1) Steam:
      More than 103 kPa (15 psig)	52	2 62 or 63
      Equal to or less than 103 kPa (15 psig)	53	63
      (2) Hot water heating:
      More than 689 kPa (100 psig) or 121 °C (250 °F)	52	63
      Equal to or less than 689 kPa (100 psig) and 121 °C (250 °F)	53	63
      (3) Hot water supply:
      More than 689 kPa (100 psig) or 121 °C (250 °F)	52	63
      Equal to or less than 689 kPa (100 psig) and 121 °C (250 °F)	53	63
      Other:
      (1) Fired thermal fluid heaters: All	52	63
      (2) Unfired steam boiler:
      More than 206 kPa (30 psig) or 454 °C (850 °F) 3	52	NA
      Equal to or less than 206 kPa (30 psig) and 454 °C (850 °F)	54	NA
      (3) Evaporators and heat exchangers: More than 103 kPa (15 psig) 4	54	NA
      (4) Unfired hot water supply or heating boiler: More than 103 kPa (15 psig) 4	54	NA
      1 Including exhaust gas types.
      2 Boilers with heat input ratings ≥12,500,000 Btu/hr. must have controls that meet part 62 of this subchapter. Boilers with heat input ratings <12,500,000 Btu/hr. must have controls that meet part 63 of this subchapter.
      3 Temperature of working fluid.
      4 Relief device is required even if designed for less than 103 kPa (15 psig).

      Table 2 to § 54.01-5—Pressure Vessel Classification

      Class	Service contents	Class limits onpressure andtemperature	Joint requirements 1 6 7	Radiographyrequirements,Section VIII of theASME BPVC(incorporatedby reference;see § 54.01-1) 3 7	Post-weld heat treatmentrequirements 5 7
      I	(a) Vapor or gas(b) Liquid(c) Hazardous Materials 2	Vapor or gas: Over 600 psi or 700 °FLiquid: Over 600 psi or 400 °F	(1) For category A; (1) or (2) for category B. All categories C and D must have full penetration welds extending through the entire thickness of the vessel wall or nozzle wall	Full on all butt joints regardless of thickness. Exceptions listed in table UCS-57 of Section VIII of the ASME BPVC do not apply	For carbon- or low-alloy steel, in accordance with table UCS-56 of Section VIII of the ASME BPVC, regardless of thickness. For other materials, in accordance with Section VIII.
      I-L Low Temperature	(a) Vapor or gas, or liquid(b) Hazardous Materials 2	Over 250 psi and service temp. below 0 °F	(1) For categories A and B. All categories C and D must have full penetration welds extending through the entire thickness of the vessel wall or nozzle wall. No backing rings or strips left in place	Full on all butt joints regardless of thickness. Exceptions listed in table UCS-57 of Section VIII of the ASME BPVC do not apply	For carbon- or low-alloy steel, in accordance with table UCS-56 of Section VIII of the ASME BPVC, regardless of thickness. For other materials, in accordance with Section VIII.
      II	(a) Vapor or gas(b) Liquid(c) Hazardous Materials 2 3 6	Vapor or gas: 30 through 600 psi or 275 through 700 °FLiquid: 200 through 600 psi or 250 through 400 °F	(1) Or (2) for category A. (1), (2), or (3) for category BCategories C and D in accordance with UW-16 of Section VIII of the ASME BPVC	Spot, unless exempted by UW-11(c) of Section VIII of the ASME BPVC	In accordance with Section VIII of the ASME BPVC.
      II-L Low Temperature	(a) Vapor or gas, or liquid(b) Hazardous Materials 2	0 through 250 psi and service temp. below 0 °F	(1) For category A; (1) or (2) for category B. All categories C and D must have full-penetration welds extending through the entire thickness of the vessel wall or nozzle wall	Spot. The exemption of UW-11(c) of Section VIII of the ASME BPVC does not apply	Same as for I-L except that mechanical stress relief may be substituted if allowed under subpart 54.30.
      III	(a) Vapor or gas(b) Liquid(c) Hazardous Materials 2 3 6	Vapor or gas: Under 30 psi and 0 through 275 °FLiquid: Under 200 psi and 0 through 250 °F	In accordance with Section VIII of the ASME BPVC	Spot, unless exempted by UW-11(c) of Section VIII of the ASME BPVC	In accordance with Section VIII of the ASME BPVC.
      1 Welded joint categories are defined under UW-3 of Section VIII of the ASME BPVC. Joint types are described in table UW-12 of Section VIII of the ASME BPVC, and numbered (1), (2), etc.
      2 See § 54.20-2.
      3 See §§ 54.25-8(c) and 54.25-10(d).
      4 See §§ 54.01-15 and 54.10-3 for exemptions.
      5 Specific requirements modifying table UCS-56 of Section VIII of the ASME BPVC appear in § 54.25-7.
      6 See § 54.20-3(c) and (f).
      7 Applies only to welded pressure vessels.
      Note 1 to table 2 to § 54.01-5: All classes of pressure vessels are subject to shop inspection and plan approval. See §§ 54.01-15 and 54.10-3 for exemptions.

      (Approved by the Office of Management and Budget under OMB control number 2130-0181)

[CGFR 68-82, 33 FR 18828, Dec. 18, 1968, as amended by CGFR 69-127, 35 FR 9976, June 17, 1970; CGD 77-147, 47 FR 21809, May 20, 1982; 55 FR 696, Jan. 8, 1990; CGD 88-057, 55 FR 24236, June 15, 1990; CGD 85-061, 55 FR 41917, Oct. 16, 1990; CGD 95-027, 61 FR 26000, May 23, 1996; USCG-2000-7790, 65 FR 58460, Sept. 29, 2000; USCG-2003-16630, 73 FR 65165, Oct. 31, 2008]