Pipeline Safety Interpretation PI-82-0110

Page 1PI-82-0110 November 18, 1982 Mr. B.H. Blackmon President, Cook Inlet Pipe Line Company P.O. Box 900 Dallas, TX 75221 Dear Mr. Blackmon: Your letter dated October 25, 1982, concerned the maximum operating pressure for a segment of the Cook Inlet pipeline system and asked whether a reduction in operating pressure is an acceptable remedy for corrosion pitting. You referred to an interpretation of §§195.416(f) and (g) given to Williams Pipe Line Company on August 16, 1982, and asked whether your understanding of that interpretation is correct. The referenced interpretation says in rather lead-footed terms that a reduction in operating pressure, commensurate with the remaining pipe thickness, is an acceptable remedy for general corrosion under §195.416(f) as well as isolated corrosion pitting under §195.416(g). Your understanding of that interpretation is correct as given in your letter. Please be advised, however, that maximum operating pressure is limited by all of the requirements of §195.406. Sincerely, Original signed by Richard L. Beam Richard L. Beam Associate Director for Pipeline Safety Regulation Materials Transportation Bureau#

Page 2October 25, 1982 COOK INLET PIPE LINE COMPANY P. O. BOX 900 DALLAS, TEXAS 75221 Mr. Richard L. Beam Associate Director for Pipeline Safety Regulation Materials Transportation Bureau U.S. Department of Transportation 400 Seventh Street, S.W. Washington, D.C. 20590 Dear Mr. Beam: We would like to establish an understanding relative to the repair of the Cook Inlet pipeline system, which was discussed by our representative, Mr. Dale Wilson, at the API-DOT meeting on September 8. A 20-mile segment of the Cook Inlet pipeline system was surveyed for corrosion pitting this summer and no corrosion indications more severe than "moderate" (30% to 50% wall loss) were disclosed. The maximum operating pressure of this system based on 20" O.D., .250" WT, Grade X52 has been established at 936 psi. It is our understanding that the DOT's August 16, 1982 Pipeline Safety Regulatory Interpretation granted to Williams Brothers will allow us to reestablish the maximum operating pressure at 468 psi for this pipeline segment. This is based on using the remaining wall thickness at the bottom of a moderate pit of maximum depth in the pressure formula of Section 195.106 (liquid regulations). Please let us know if our understanding is correct. Yours very truly, B. H. Blackmon President#