CONAM Inspection, Inc. — Pipeline Safety Interpretation

Page 1April 20, 1972 Mr. David A. Warren CONAM Inspection, Inc. 1115 West 41st Street Tulsa, Oklahoma 74105 Dear Mr. Warren: This is in reply to your letter of March 6, 1972, to Mr. Lance Heverly. With regard to your question on general corrosion, if the transmission line's operating pressure is equal to the pipeline design pressure in accordance with the design formula contained in Section 192.105, Section 192.485 gives the operator two choices when an area of general corrosion causes reduced wall thickness: 1. Replace the generally corroded segment of pipe; or 2. Reduce the operating pressure commensurate with the strength of the remaining pipe wall thickness. In the case of localized corrosion pitting, it is the operator's responsibility to determine if the remaining wall thickness, taking into account the reinforcing strength provided by the pipe wall surrounding the pit, will withstand his maximum operating pressure. If the strength of the pipe has been reduced by the corrosion, then the operator must either replace or repair the segment involved or assure that his operating pressure is commensurate with the strength of the remaining pipe wall thickness. As a result of the evaluation of the information presented at the Public Hearing held on July 20, 1971, and other data available to this office, it was decided to withdraw the Notice of Proposed Rule Making (Notice 71-3; Docket No. OPS-5) and leave the regulations in the performance language as contained in the regulations covering corrosion control requirements issued June 25, 1971. Consideration is being given to the recommendations presented at the hearing for a possible new Notice of Proposed Rule Making relating the acceptability of the pipe to a combination of localized corrosion pit depth, width, and length. As Mr. Heverly told you in his telephone conversation, we have no time schedule set for this notice. dal\192\105\72-04-20 1#

Page 22 Your company has been added to our mailing list for receiving copies of our regulations. Thank you for your interest in our pipeline safety program. Sincerely, Joseph C. Caldwell Director Office of Pipeline Safety dal\192\105\72-04-20 2#

Page 3March 6, 1972 Mr. Lance Heverly Corrosion Engineer Office of Pipeline Safety Department of Transportation 400 Seventh Street, S.W. Washington, D.C. Dear Sir: Thank you very much for your call on 3-1-72 and the information on the current status of 49CFR Part 192. I should like to ask your opinion of a suggested interpretation of Section 192.485 of the present regulation. In the case of general corrosion or localized corrosion pitting, corrosion could exist to the extent that 28% of the nominal wall thickness was missing and the operator could continue operating at maximum design pressure since that pressure would be 72% SMYS as per B31.8. It is my understanding that there is at present no dimensional criterion for pits, but that a change will be made in the regulation probably this spring, which will define pitting in terms of combined depth and diameter measurements in terms of wall thickness. Does the Department of Transportation have a mailing list for announcements, regulations, etc? If so, we would appreciate having our name added for mailings related to pipeline safety. Sincerely, CONAM INSPECTION, INC. David A. Warren dal\192\105\72-04-20 3#