Pipeline Safety Interpretation PI-83-0107

Page 1PI-83-0107 August 4 1983 Mr. Charles L Poole, P.E. O'Malley & Clay, Inc. P.O. Box 1976 505 Green Street Brenham, TX 77833 Dear Mr. Poole: Your letter 04 July 19, 1983, asks three specific questions concerning 49 CFR Section 192.469, External corrosion control: Test stations, as it applies to a catholically protected steel natural gas distribution system. These questions are as follows: 1. Do the services provide "sufficient" test stations? 2. If not, at what frequency, or spacing, should additional test stations be installed? 3. If the services were not electrically connected to the main, or were widely scattered, what should the test station spacing be? If the service lines are electrically continuous with the mains, they may be used as test stations. Spacing of test stations along the pipeline system will vary widely depending upon the type of soil, moisture, quality of pipe coating, size of pipe, type of cathodic protection system, level of cathodic protection, etc. Whatever the number and spacing of test points along a cathodically protected pipeline, they must be adequate to show that the cathodic protection level along the entire length of pipeline meets the requirements of Section. 192.463. With so many variables involved, the distance between test stations must be based on the judgment of a person qualified by experience and training in pipeline corrosion control methods for the specific installation and conditions. We hope this provides the information you are seeking. Sincerely, Richard L. Beam Associate Director for Pipeline Sanity Regulation Materials Transportation Bureau#

Page 2O’Malley & Clay, Inc. P.O. Box 1976 505 Green Street Brenham, Texas 77833 July 19, 1983 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 Re: 49 CFR 192.469 External Corrosion Control: Test Stations. Dear Mr. Beam: We wish to quantify the term "sufficient" contained in the referenced paragraph. Enclosed is a typical print of a portion of a cathodically protected steel natural gas distribution system owned by a client. There is electrical continuity between gas services and mains. Pipe-to-soil potential readings can be made at meter risers. Our questions are these. Do the services provide "sufficient" test stations? If not, at what frequency, or spacing, should additional test stations be installed? If the services were not electrically connected to the main, or were widely scattered, what should the test station spacing be? We are most appreciative of any information or assistance you can provide. Sincerely, Charles I. Poole, P.E.#