[Code of Federal Regulations] [Title 46, Volume 2] [Revised as of October 1, 2004] From the U.S. Government Printing Office via GPO Access [CITE: 46CFR64.59] [Page 321] TITLE 46--SHIPPING CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PART 64_MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS--Table of Contents Subpart C_Pressure Relief Devices and Vacuum Relief Devices for MPTs Sec. 64.59 Spring loaded pressure relief valve. A spring loaded pressure relief valve must-- (a) Be set at a nominal pressure of 125 percent of the maximum allowable working pressure; (b) Have a minimum normal venting capacity that is sufficient to prevent the tank pressure from exceeding 137.5 percent of the maximum allowable working pressure; (c) Close after discharge of a pressure not lower than 115 percent of the maximum allowable working pressure; and (d) If closed, remain closed at any pressure less than 115 percent of the maximum allowable working pressure.