255.485 Remedial measures: transmission lines.

(a)Each segment of transmission line with general corrosion and with a remaining wall thickness less than that required for the maximum allowable operating pressure of the pipeline must be replaced or the operating pressure reduced commensurate with the strength of the pipe based on actual remaining wall thickness. However, if the area of general corrosion is small, the corroded pipe may be repaired by a method that reliable engineering tests and analyses show can permanently restore the serviceability of the pipe. Corrosion pitting so closely grouped as to affect the overall strength of the pipe is considered general corrosion.#

(b)Each segment of transmission line pipe with localized corrosion pitting to a degree where leakage might result must be replaced or repaired or the operating pressure reduced commensurate with the strength of the pipe based on the actual remaining wall thickness in the pits.#

(c)Under subdivisions (a) and (b) of this section, the strength of transmission line pipe based on actual remaining wall thickness may be determined by the procedure in ASME B31G (as described in section 10.3 of this Title), or the procedure PRCI PR 3-805 (R-STRENG) (as described in section 10.3 of this Title). Both procedures apply to corroded regions that do not penetrate the pipe wall, subject to the limitations prescribed in the procedures.#