49 C.F.R. § 179.400-8 Thickness of plates.
Title 49 - Transportation
(a) The minimum wall thickness, after forming, of the inner shell and any 2:1 ellipsoidal head for the inner tank must be that specified in §179.401–1, or that calculated by the following formula, whichever is greater: t = Pd / 2SE
Where: t = minimum thickness of plate, after forming, in inches; P = minimum required bursting pressure in psig; d = inside diameter, in inches; S = minimum tensile strength of the plate material, as prescribed in AAR Specifications for Tank Cars, appendix M, Table M1 (IBR, see §171.7 of this subchapter), in psi; E = 0.9, a factor representing the efficiency of welded joints, except that for seamless heads, E = 1.0. (b) The minimum wall thickness, after forming, of any 3:1 ellipsoidal head for the inner tank must be that specified in §179.401–1, or that calculated by the following formula, whichever is greater: t = 1.83 Pd / 2SE
Where: t = minimum thickness of plate, after forming, in inches; P = minimum required bursting pressure in psig; d = inside diameter, in inches; S = minimum tensile strength of the plate material, as prescribed in AAR Specifications for Tank Cars, Appendix M, Table M1, in psi; E = 0.9, a factor representing the efficiency of welded joints, except that for seamless heads, E=1.0. (c) The minimum wall thickness, after forming, of a flanged and dished head for the inner tank must be that specified in §179.401–1, or that calculated by the following formula, whichever is greater: t = [PL(3 + √(L/r))] / (8SE)
Where: t = minimum thickness of plate, after forming, in inches; P = minimum required bursting pressure in psig; L = main inside radius of dished head, in inches; r = inside knuckle radius, in inches; S = minimum tensile strength of plate material, as prescribed in AAR Specifications for Tank Cars, appendix M, table M1, in psi; E = 0.9, a factor representing the efficiency of welded joints, except that for seamless heads, E = 1.0. (d) The minimum wall thickness, after forming, of the outer jacket shell may not be less than Pc = [2.6E(t/D)2.5 ] / [(L/D) − 0.45(t/D)0.5 ]
Where: Pc = Critical collapsing pressure (37.5 psig minimum) in psig; E = modulus of elasticity of jacket material, in psi; t = minimum thickness of jacket material, after forming, in inches; D = outside diameter of jacket, in inches; L = distance between stiffening ring centers in inches. (The heads may be considered as stiffening rings located [Amdt. 179–32, 48 FR 27708, June 16, 1983; 49 FR 42736, Oct. 24, 1984; 64 FR 51920, Sept. 27, 1999, as amended at 66 FR 45390, Aug. 28, 2001; 68 FR 75763, Dec. 31, 2003]
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)
§ 179.400-8 Thickness of plates.