Section 143.300 - 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 .USCG-2006-24412, 81 FR 40101, June 20, 2016; 81 FR 47312, July 21, 2016