255.309 Repair of steel pipe.

(a)Each imperfection or damage that impairs the serviceability of the length of steel pipe must be repaired or removed.#

(b)If a repair is made by grinding, the remaining wall thickness must at least be equal to either:#

(1)the minimum thickness required by the tolerances in the specification to which the pipe was manufactured; or#

(2)the nominal wall thickness required for the design pressure of the pipeline.#

(c)Each of the following dents must be removed from steel pipe to be operated at a pressure of 125 psig (862 kPa) or more, unless the dent is repaired by a method that reliable engineering tests and analyses show can permanently restore the serviceability of the pipe:#

(1)a dent that contains a stress concentrator such as a scratch, gouge, groove or arc burn;#

(2)a dent that affects a longitudinal weld or a circumferential weld;#

(3)a dent that has a depth of more than one-quarter inch in pipe 12¾ inches (324 millimeters) or less in outer diameter; or#

(4)a dent that has a depth of more than two percent of the nominal pipe diameter in pipe over 12¾ inches (324 millimeters) in outer diameter.#

(d)For the purpose of this section, a dent is a depression that produces a gross disturbance in the curvature of the pipe wall without reducing the pipewall thickness. The depth of a dent is measured as the gap between the lowest point of the dent and a prolongation of the original contour of the pipe.#

(e)Each arc burn on steel pipe to be operated at a pressure of 125 psig (862 kPa) or more must be repaired or removed. If a repair is made by grinding, the arc burn must be completely removed.#

(f)Complete removal of the metallurgical notch created by an arc burn can be determined by grinding away the visible evidence of the arc burn and then swabbing the ground area with a 20 percent solution of ammonium persulfate. A blackened spot is evidence of a metallurgical notch and indicates that additional grinding is necessary.#

(g)A gouge, groove, arc burn or dent may not be repaired by insert patching or by pounding out.#

(h)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.#

(i)Notches or laminations on pipe ends shall not be repaired on pipe to be operated at a pressure of 125 psig (862 kPa) or more. The damaged portion shall be removed as a cylinder and the pipe end rebeveled.#