49 CFR §192.313

1. (a)Each field bend in steel pipe, other than a wrinkle bend made in accordance with § 192.315, must comply with the following:
   1. (1)A bend must not impair the serviceability of the pipe.
   2. (2)Each bend must have a smooth contour and be free from buckling, cracks, or any other mechanical damage.
   3. (3)On pipe containing a longitudinal weld, the longitudinal weld must be as near as practicable to the neutral axis of the bend unless:
      1. (i)The bend is made with an internal bending mandrel; or
      2. (ii)The pipe is 12 inches (305 millimeters) or less in outside diameter or has a diameter to wall thickness ratio less than 70.
2. (b)Each circumferential weld of steel pipe which is located where the stress during bending causes a permanent deformation in the pipe must be nondestructively tested either before or after the bending process.
3. (c)Wrought-steel welding elbows and transverse segments of these elbows may not be used for changes in direction on steel pipe that is 2 inches (51 millimeters) or more in diameter unless the arc length, as measured along the crotch, is at least 1 inch (25 millimeters).
4. (d)An operator may not install plastic pipe with a bend radius that is less than the minimum bend radius specified by the manufacturer for the diameter of the pipe being installed.