46 CFR 143.300: Pressure vessels on towing vessels
Last reviewed: October 14, 2026
This section sets rules for pressure vessels. Pressure vessels over 5 cubic feet in volume and over 15 pounds per square inch MAWP must have a gauge and relief valves. All pressure vessels must be examined externally each year and must show their MAWP.
Applies toPressure vessels, with the gauge and relief valve requirements applying to those over 5 cubic feet in volume and over 15 pounds per square inch maximum allowable working pressure (MAWP).
What it says
Pressure vessels over 5 cubic feet in volume and over 15 pounds per square inch MAWP must have an indicating pressure gauge in a readily visible location and one or more spring-loaded relief valves.
46 CFR 143.300(a)“must be equipped with an indicating pressure gauge (in a readily visible location) and with one or more spring-loaded relief valves.”
For those pressure vessels, the total relieving capacity of the relief valves must prevent pressure from exceeding the manufacturer-established MAWP by more than 10 percent.
46 CFR 143.300(a)“The total relieving capacity of such relief valves must prevent pressure from exceeding the MAWP, as established by the manufacturer, by more than 10 percent.”
Pressure vessels must be externally examined annually.
46 CFR 143.300(b)“Pressure vessels must be externally examined annually.”
Relief valves must be tested in accordance with § 143.245.
46 CFR 143.300(b)“Relief valves must be tested in accordance with § 143.245.”
All pressure vessels must have the MAWP indicated by a stamp, nameplate, or other means visible to the crew.
46 CFR 143.300(c)“All pressure vessels must have the MAWP indicated by a stamp, nameplate, or other means visible to the crew.”
Pressure vessels installed after July 20, 2018, or the date the vessel obtains a Certificate of Inspection (COI), whichever date is earlier, must meet the requirements of § 143.545.
46 CFR 143.300(d)“Pressure vessels installed after July 20, 2018, or the date the vessel obtains a Certificate of Inspection (COI), whichever date is earlier, must meet the requirements of § 143.545.”
Common questions
How often must pressure vessels be examined?
Pressure vessels must be externally examined annually.
“Pressure vessels must be externally examined annually.”
How must the MAWP of a pressure vessel be shown?
The MAWP must be indicated by a stamp, nameplate, or other means visible to the crew.
“All pressure vessels must have the MAWP indicated by a stamp, nameplate, or other means visible to the crew.”
Which section governs testing of pressure vessel relief valves?
Relief valves must be tested in accordance with § 143.245.
“Relief valves must be tested in accordance with § 143.245.”
What rule applies to pressure vessels installed after July 20, 2018?
Pressure vessels installed after July 20, 2018, or the date the vessel obtains a COI, whichever is earlier, must meet § 143.545.
“must meet the requirements of § 143.545.”
The text of 46 CFR 143.300
Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR
Pressure vessels
(a) Pressure vessels over 5 cubic feet in volume and over 15 pounds per square inch maximum allowable working pressure (MAWP) must be equipped with an indicating pressure gauge (in a readily visible location) and with one or more spring-loaded relief valves. The total relieving capacity of such relief valves must prevent pressure from exceeding the MAWP, as established by the manufacturer, by more than 10 percent.
(b) Pressure vessels must be externally examined annually. Relief valves must be tested in accordance with § 143.245.
(c) All pressure vessels must have the MAWP indicated by a stamp, nameplate, or other means visible to the crew.
(d) Pressure vessels installed after July 20, 2018, or the date the vessel obtains a Certificate of Inspection (COI), whichever date is earlier, must meet the requirements of § 143.545.
Sections it refers to
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.