Code of Federal Regulations Title 49. Transportation § 49.178.338–12 Shear section

Unless the valve is located in a rear cabinet forward of and protected by the bumper (see § 178.338–10(c)), the design and installation of each valve, damage to which could result in loss of liquid or vapor, must incorporate a shear section or breakage groove adjacent to, and outboard of, the valve. The shear section or breakage groove must yield or break under strain without damage to the valve that would allow the loss of liquid or vapor. The protection specified in § 178.338–10 is not a substitute for a shear section or breakage groove.