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T7--TLE 8 DIVISION OF INDUSTRIAL ° .FETY 58 02.1 UNFIRED PRESSURE VESSEL SAID KY ORDERS Surface area = total outside surface area of container in square feet. When the surface area is not stamped on the nameplate or when the marking is not legible, the area can be calculated by using one of the following formulas: (1) Cylindrical container with hemispherical heads. Area = overall length in feet times outside diameter in feet times 3.1416 (2) Cylindrical containers with other than hemispherical heads. Area = (overall length in feet plus 0.3 outside diameter in feet) times outside diameter in feet times 3.1416 (3) Spherical container. Area = outside diameter in feet squared times 3.1416 Flow rate—CFM Air = cubic feet per minute of air required at standard conditions, 60 degrees Fahrenheit and atmospheric pressure (14.7 psia). The rate of discharge may be interpolated for intermediate values of surface area. For containers with total outside surface area greater than 2,500 square feet, the required flow rate can be calculated using the formula: Flow Rate CFM Air = 22.11A°'82, where A = outside surface area of the container in square feet. The minimum required rate of discharge of safety relief valves for anhydrous ammonia DOT cylinders shall be in accordance with the regulations of the Bureau of Explosives. (c) Safety relief valves shall be so designed and installed that the possibility of tampering will be minimized. If the pressure setting is external, the relief valves shall be provided with acceptable means for sealing the adjustment. �� relief (d) Shutoff valves shall not be installed between the safety retieF valve and tank, except that a shutoff valve may be used where the arrangement of this valve is such as always to provide full required capacity flow through sufficient relief valves to properly protect the tank. [This exception is intended to permit 3-way valves, mechanically interconnected valves, etc., to be installed between the tank and safety valve where the installation and arrangement will always permit the required number of valves to be in communication with the tank to provide the relief capacity required by (b) above.] The flow capacity of the relief valve shall not be restricted by any connection to it on either the upstream or downstream side. (e) Each safety relief valve used on anhydrous ammonia tanks shall be plainly marked with the following information: (1) With the letters "AA." (2) The pressure in poundsper square inch gage (psig) at which the valve is set to start to discharge. (3) The rate of discharge of the valve at its full open position in cubic feet per minute (cfm) of air.