49 CFR §180.411

1. (a)Corroded or abraded areas. The minimum thickness may not be less than that prescribed in the applicable specification.
2. (b)Dents, cuts, digs and gouges. For evaluation procedures, see CGA C-6 (IBR, see § 171.7 of this subchapter).
   1. (1)For dents at welds or that include a weld, the maximum allowable depth is 1/2 inch. For dents away from welds, the maximum allowable depth is 1/10 of the greatest dimension of the dent, but in no case may the depth exceed one inch.
   2. (2)The minimum thickness remaining beneath a cut, dig, or gouge may not be less than that prescribed in the applicable specification.
3. (c)Weld or structural defects. Any cargo tank with a weld defect such as a crack, pinhole, or incomplete fusion, or a structural defect must be taken out of hazardous materials service until repaired.
4. (d)Leakage. All sources of leakage must be properly repaired prior to returning a tank to hazardous materials service.
5. (e)Relief valves. Any pressure relief valve that fails to open and reclose at the prescribed pressure must be repaired or replaced.
6. (f)Liner integrity. Any defect shown by the test must be properly repaired.
7. (g)Pressure test. Any tank that fails to meet the acceptance criteria found in the individual specification that applies must be properly repaired.