1. Scope

Marine System Pressure Vessels should comply with the additional requirements specified herein, in addition to “Specification - Pressure Vessels”, for the design and fabrication.

When designated on the pressure vessel data sheet as a MARINE SYSTEM pressure vessel, such pressure vessels will also be required to meet the requirements as described in 46 CFR Part 54.

Part 54 requires that pressure vessels be designed, constructed and inspected in accordance with ASME VIII, Division 1 except as limited, modified, or replaced by specific requirements in 46 CFR Part 54.

The requirements listed in 46 CFR Part 54 vary depending on the design conditions of the pressure vessel, primarily service, pressure, and temperature.

  1. The most common conditions for offshore facility applications under US Coast Guard (USCG) jurisdiction are described in this scope.
  2. For requirements of other Marine System pressure vessels, refer to Part 54 in its entirety.
  3. The below section “Pressure Vessel Types” describes the design conditions covered by this scope.

Should there be a conflict between this and other pressure vessel specifications, the ASME Code and/or this Appendix, the more stringent should apply. Buyer should be notified of all conflicts.

2. Pressure Vessel Types

To delineate the applicability of various sections of the USCG requirements, this paragraph describes several types of pressure vessels.

Refer to 46 CFR Part 54 in its entirety if the pressure vessel design conditions do not fit within the limitations of one of these types.

Limitations of Conditions
Type USCG Definition

Pressure/Temperature Limits

Volume Services

Class II Hazardous Material

Gas - 30 to 600 psig from 00 to 7000F

Liquid - 200 to 600 psig from 00 to 4000F

No Limits

Diesel or helicopter fuel (classification of other materials as hazardous must be approved by Buyer and based on USCG definition).

A Class II Hazardous Material

Gas - up to 30 psig from 00 to 2750F

Liquid - up to 200 psig from 00 to 2500F

No Limits

Diesel or helicopter fuel (classification of other materials as hazardous must be approved by Buyer and based on USCG definition).


Class II Non-hazardous Material

Gas - 30 to 600 psig from 00 to 7000F

Liquid - 200 to 600 psig from 00 to 4000F

Over 5 cu. ft.

Air, Seawater, or Freshwater (classification of other materials as non-hazardous must be approved by Buyer and based on the USCG definition).

C Same as Type B Same as Type B

Equal to or less than 5 cu. ft.

Same as Type B

3. Requirements for Type A and Type B Pressure Vessels

3.1 Drawings and Plans

Supplier should develop detailed drawings and plans for Buyer review in accordance with 46 CFR, Subpart 54.01-18 and 54.01-5e. These documents should be sent to Buyer for review with the other Supplier data requirements. These plans may need to be submitted to the USCG for review (see sections 4 and 5 below). These plans must be certified by a registered professional engineer as meeting the design requirements of this Specification, this Appendix and the ASME Code. The certification must appear on all drawings and analyses.

3.2 Pressure Vessel Identification

In addition to the identification stamping information listed in Section 9.0 of “Specification - Pressure Vessels”, pressure vessel identification should include the USCG class (see section 2.0 or Table 54.01-5B in 46 CFR Part 54 for the listing of Class). The USCG symbol and number should be stamped on the pressure vessel by the Marine Inspector, either at the shop for Type A vessels or at the installation location for Type B vessels

3.3 Reports

The Supplier should complete and certify the data reports required by 46 CFR Subpart 54.10-25.

4. Additional Requirements for Type A Vessels

Type A pressure vessels will require USCG plan approval. The detailed plans developed in accordance with paragraph 3.1 should be submitted by Supplier in accordance with 46 CFR Part 50.20.

Type A vessels will require USCG shop inspection and stamp by USCG Marine Inspectors as described in 46 CFR Subparts 54.10-3, 54.10-10, and 50.30-20. Supplier should notify the Officer in Charge of Marine Inspection of the intended fabrication of vessels that will require Coast Guard inspection.

  • Type A vessels will require hydrostatic testing in accordance with CFR Subpart 54.10-10.
  • Type A Vessels will be designed and fabricated for MAWP in accordance with 46 CFR Subpart 54.10-5.

Fabrication and welding for Type A vessels should be in accordance with 46 CFR Subpart 54.20 and 46 CFR Part 57.

Type A vessels also require USCG field inspection at the installation site.

5. Additional Requirements for Type B Vessels

For Type B pressure vessels, the Supplier will not be required to submit the documentation, as described in Section 3.1, to the USCG for approval prior to fabrication. In addition, the USCG does not require a shop inspection, but will perform a field inspection of the vessels and plans. The USCG visual field examination of the vessels and review of the plans will be made prior to installation, according to 46 CFR Subpart 54.10-3c. Following satisfactory USCG field inspection, Type B vessels will receive a USCG stamp.

6. Requirements for Type C Vessels

Type C pressure vessels do not have any additional requirements of 46 CFR Part 54. These vessels should comply with this Specification and the ASME Code.