180.509—Requirements for inspection and test of specification tank cars.

(3) A written report as specified in § 180.517(b) must be prepared for each tank car that is inspected and tested under this section.
Where:
i is the inspection and test interval.
t1 is the actual thickness.
t2 is the allowable minimum thickness under paragraph (g) of this section.
r is the corrosion rate per year.
Allowable Shell Thickness Reductions
Damage type Class DOT 103, 104, 111, and 115 tank cars Class DOT 105, 109, 112, and 114 tank cars
Top shell and tank head Bottom shell Top shell and tank head Bottom shell
Corrosion 3.17 mm (0.125 inch) 1.58 mm (0.063 inch) 0.79 mm (0.031 inch) 0.79 mm (0.031 inch).
Corrosion and mechanical 3.17 mm (0.125 inch) 1.58 mm (0.063 inch) 0.79 mm (0.031 inch) 0.79 mm (0.031 inch).
Corrosion, local 4.76 mm (0.188 inch) 3.17 mm (0.125 inch) 1.58 mm (0.063 inch) 1.58 mm (0.063 inch).
Mechanical, local 3.17 mm (0.125 inch) 1.58 mm (0.063 inch) 1.58 mm (0.063 inch) 1.58 mm (0.063 inch).
Corrosion and mechanical, local 4.76 mm (0.188 inch) 3.17 mm (0.125 inch) 1.58 mm (0.063 inch) 1.58 mm (0.063 inch).
Notes: 1. The perimeter for a local reduction may not exceed a 60.96 cm (24 inch) perimeter. Local reductions in the top shell must be separated from other reductions in the top shell by at least 40.64 cm (16 inches). The cumulative perimeter for local reductions in the bottom shell may not exceed 182.88 cm (72 inches).
2. Any reduction in the tank car shell may not affect the structural strength of the tank car so that the tank car shell no longer conforms to Section 6.2 of the AAR Specifications for Tank Cars (IBR, see § 171.7 of this subchapter).
3. Any reduction applies only to the outer shell for Class DOT 115 tank cars.
4. For Class DOT 103 and 104 tank cars, the inside diameter may not exceed 243.84 cm (96 inches).
[Amdt. 180-8, 60 FR 49079, Sept. 21, 1995, as amended by Amdt. 179-50, 61 FR 33256, June 26, 1996; 62 FR 51561, Oct. 1, 1997; 63 FR 52851, Oct. 1, 1998; 66 FR 45391, Aug. 28, 2001; 68 FR 75765, Dec. 31, 2003; 71 FR 54398, Sept. 14, 2006]