49 CFR 192.313
Bends and elbows.
(a)Each field bend in steel pipe, other than a wrinkle bend made in accordance with § 192.315, must comply with the following:#
(1)A bend must not impair the serviceability of the pipe.#
(2)Each bend must have a smooth contour and be free from buckling, cracks, or any other mechanical damage.#
(3)On pipe containing a longitudinal weld, the longitudinal weld must be as near as practicable to the neutral axis of the bend unless:#
(i)The bend is made with an internal bending mandrel; or#
(ii)The pipe is 12 inches (305 millimeters) or less in outside diameter or has a diameter to wall thickness ratio less than 70.#
(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.#
(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).#
(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.#