49 C.F.R. § 179.500-4 Thickness of wall.
Title 49 - Transportation
(a) Minimum thickness of wall of each finished tank shall be such that at a pressure equal to (b) Calculations to determine the maximum marked test pressure permitted to be marked on the tank shall be made by the formula: P = [10S(D2 − d2 )] / [7(D2 +d2 )]
Where: P = Maximum marked test pressure permitted; S = U / 3.0
Where: U = Tensile strength of that specimen which shows the lower tensile strength of the two specimens taken from the tank and tested as prescribed in §179.500–7(b). 3 = Factor of safety. (D2 − d2 /(D2 + d2 ) = The smaller value obtained for this factor by the operations specified in §179.500–4(c). (c) Measure at one end, in a plane perpendicular to the longitudinal axis of the tank and at least 18 inches from that end before necking-down:
d = Maximum inside diameter (inches) for the location under consideration; to be determined by direct measurement to an accuracy of 0.05 inch. t = Minimum thickness of wall for the location under consideration; to be determined by direct measurement to an accuracy of 0.001 inch. Take D = d + 2t. Calculate the value of (D2 −d2 )/(D2 + d2 ) (1) Make similar measurements and calculation for a corresponding location at the other end of the tank. (2) Use the smaller result obtained, from the foregoing, in making calculations prescribed in paragraph (b) of this section. [29 FR 18995, Dec. 29, 1964. Redesignated at 32 FR 5606, Apr. 5, 1967, and amended by Amdt. 179–31, 47 FR 43067, Sept. 30, 1982; 66 FR 45391, Aug. 28, 2001]
Title 49: Transportation
PART 179—SPECIFICATIONS FOR TANK CARS
Subpart F—Specification for Cryogenic Liquid Tank Car Tanks and Seamless Steel Tanks (Classes DOT-113 and 107A)
§ 179.500-4 Thickness of wall.