49 CFR §192.309

1. (a)Each imperfection or damage that impairs the serviceability of a length of steel pipe must be repaired or removed. If a repair is made by grinding, the remaining wall thickness must at least be equal to either:
   1. (1)The minimum thickness required by the tolerances in the specification to which the pipe was manufactured; or
   2. (2)The nominal wall thickness required for the design pressure of the pipeline.
2. (b)Each of the following dents must be removed from steel pipe to be operated at a pressure that produces a hoop stress of 20 percent, or more, of SMYS, unless the dent is repaired by a method that reliable engineering tests and analyses show can permanently restore the serviceability of the pipe:
   1. (1)A dent that contains a stress concentrator such as a scratch, gouge, groove, or arc burn.
   2. (2)A dent that affects the longitudinal weld or a circumferential weld.
   3. (3)In pipe to be operated at a pressure that produces a hoop stress of 40 percent or more of SMYS, a dent that has a depth of:
      1. (i)More than 1/4 inch (6.4 millimeters) in pipe 12 3/4 inches (324 millimeters) or less in outer diameter; or
      2. (ii)More than 2 percent of the nominal pipe diameter in pipe over 12 3/4 inches (324 millimeters) in outer diameter.
3. (c)Each arc burn on steel pipe to be operated at a pressure that produces a hoop stress of 40 percent, or more, of SMYS must be repaired or removed. If a repair is made by grinding, the arc burn must be completely removed and the remaining wall thickness must be at least equal to either:
   1. (1)The minimum wall thickness required by the tolerances in the specification to which the pipe was manufactured; or
   2. (2)The nominal wall thickness required for the design pressure of the pipeline.
4. (d)A gouge, groove, arc burn, or dent may not be repaired by insert patching or by pounding out.
5. (e)Each gouge, groove, arc burn, or dent that is removed from a length of pipe must be removed by cutting out the damaged portion as a cylinder.