Herbert Schroeder, Jr. — Pipeline Safety Interpretation

Page 1April 13, 1976 Mr. Byrd L. Minter, Manager Sealants Department Ford, Bacon & Davis P.O. Box 1762 Monroe, Louisiana 71201 Dear Mr. Minter: This refers to your letter of March 26, 1976, in which you ask whether Section 192.619(c) or Section 192.621(a) governs the maximum allowable operating pressure of a steel distribution pipeline with an inlet pressure of 170 psig. For a steel or plastic high-pressure distribution pipeline the maximum allowable operating pressure is governed by Section 192.619, subject to the applicable limitation of Section 192.621. Under these requirements, a person may not operate a pipeline at a pressure permitted by Section 192.619(c) if that pressure would exceed the applicable limitation of Section 192.621. If we may be of further assistance, please let us know. Sincerely, Cesar DeLeon Acting Director Office of Pipeline Safety Operations dal\192\619\76-04-13 1#

Page 2March 26, 1976 DOT Pipeline Safety Policy Office of Safety Affairs 400 7th Street SW Washington, DC 20590 Gentlemen: I need clarification regarding the maximum allowable operating pressure of a natural gas distribution feeder line. The line is welded ERW and does not have any service lines connected to it. Elements of the system have been installed over the past thirty years. Elements were tested at varying pressures between 100 psig and 275 psig. Two elements of the system have a different history, prior to July 1, 1970, of maximum operating pressure prior to their being connected and becoming a continuous system. One element of the system has a history of maximum operating pressure of less than 100 psig. Another element of the system has a history of maximum operating pressure of approximately 150 psig. Recently an element with a history of operating pressure of approximately 300 psig and test pressure of 500 psig has become part of the system. The maximum inlet pressure to the system is now approximately 170 psig. The basic question is which section of the rule applies to this type of line (system), paragraph 192.619 or 192.621. As I understand: If 192.619 applies, then paragraph (c) governs the MAOP even though certain elements of the system were only tested at a lower design pressure in accordance with (a)(2)(ii). If paragraph 192.621 applies, and a design pressure in accordance with paragraph (a)(1) is less than the history of the maximum safe operating pressure, then paragraph (a)(1) applies. Your clarification of the interpretation of these two paragraphs would be appreciated as this is a typical question that comes up many times during discussions of MAOP's of gas distribution feeder lines operating in the less than 200 psig range. Sincerely, Byrd L. Minter, Manager Sealants Department dal\192\619\76-04-13 2#