Harco Corporation — Pipeline Safety Interpretation

Page 1Mr. B. Husock, P.E. Harco Corporation Corrosion Engineering Division 4600 East 71st Street Cleveland, Ohio 44125 Dear Mr. Husock: This is in reply to your letter dated May 31, 1972, regarding an interpretation of Section 192.467(a), 49 CFR. Your specific question was regarding Section 192.467(a) which states, in part, "....each buried or submerged pipeline must be electrically isolated from other underground metallic structures...." You inquired whether this requirement applied to all gas distribution systems under all circumstances whether or not cathodic protection is eventually applied. Section 192.467(a) does not apply to all gas distribution systems. It is intended to apply to all new pipelines. Existing distribution systems are covered by Section 192.467(b), which requires insulation wherever electrical isolation of a portion of a pipeline is necessary to facilitate the application of corrosion control. However, existing distribution lines must be cathodically protected only in areas in which active corrosion is found (Section 192.457(b)(3)). Isolation assures an insulating barrier between metals of different anodic potentials, facilitating corrosion control. Accordingly, electrical isolation of existing distribution lines is not required under all circumstances, but only where necessary to facilitate the application of corrosion control required by Section 192.457(b)(3). We trust that this will answer your specific question. If we can be of further service, please let us know. Sincerely, /signed/ Joseph C. Caldwell Director Office of Pipeline Safety DB C:\WP51\INTERPRT\192\467\72-07-14 1#