Pipeline Safety Interpretation PI-78-0107

Page 1PI-78-0107 November 08, 1978 H.R. Garabrant P.E. Gas Utilities Safety Engineer Utilities Division Southern Arizona O ffice 415 W. Congress Street Tucson, Arizona 85701 Dear Mr. Garabrant: This refers to your letter of August 7, 1978, to Mr. Frank Fulton suggesting that Section 192.321(d) be changed to eliminate the Implication that thermoplastic pipe of 0.090 inch wall thickness is acceptable for use under Part 192 regardless of pipe diameter. We have reviewed Section 192.321(d) in light of your suggestion, and do find that the Section may have the implication you suggest. The purpose of Section 192.321(d) is to prescribe the minimum wall thickness of thermoplastic pipe that may be used without encasement. It is not intended to override, and in our opinion does not conflict with the allowable wall thickness for thermoplastic pipe set forth in ASTM D2513, which is incorporated by reference in Section 192.59. Section 192.321(d) could be stated in a better manner to make its purpose clearer. The Section will be a subject for review during the course of our regulatory reform process, and it may be restated or otherwise changed as a result of that process. Meanwhile, we plan to publish in the Advisory Bulletin a clarifying interpretation of Section 192.321(d). Sincerely, Cesar De Leon Associate Director for Pipeline Safety Regulation Materials Transportation Bureau#

Page 2United States Government Department of Transportation Research and Special Programs Administration Date: August 16, 1978 SUBJECT: Interpretation of Section 192.321(d) FROM: Associate Director for Operations and Enforcement, DMT-10 TO: Associate Director for Pipeline Safety Regulation, DMT-30 By letter of August 7, 1978 (copy attached), the Arizona Corporation Commission indicates the existence of a variance between Section 192.321 and ASTM D2513 and requests a correction of Section 192.321. Thank you for a prompt interpretation of this regulation to facilitate a timely response to the Arizona Corporation Commission. Robert Paullin#

Page 3Arizona Corporation Commission 2222 West Encanto Blvd. Phoenix, Arizona 85009 August 7, 1978 Mr. Frank Fulton State Programs Office of Pipeline Safety Operations Department of Transportation Washington, D.C. 20590 Dear Frank: I have just noticed, after all these years, what I believe is a very serious and misleading flaw in Part 192. Please refer to 192.321 (d), this paragraph would lead one to believe that, except for pipe with an outside diameter of 0.875", which can have a minimum wall thickness of .062", that any size of plastic pipe could be used, as long as it had a minimum wall thickness of 0.090" and met the MAOP requirements. This, of course, is not true if you refer to ASTM D2513-75b, Paragraph 6,2,1,2 and Table 4, you will find that 0.090" minimum wall thickness is only acceptable in sizes up to 1 ½ inches. Pipe in sizes greater than that have progressively greater minimum wall thickness. I have just finished the investigation of a fatal accident, in which 2" ABS pipe with .090 walls was involved and one contributing factor I attribute to the high SDR ratio, although other factors were the primary cause, in my estimation. Although this pipe was selected before Part 192 was in effect, I believe that paragraph 92.321 (d) should be deleted or changed to reference ASTM 2513. to prevent someone in the thinking that .090 is ok for all sizes. Please confirm that my thinking in this matter is correct and turn this request over to the standards group for correction of Part 192, Sincerely, Arizona Corporation Commission H. R. Garabrant, P.E. Gas Utilities Safety Engineer Utilities Division#