Mountain Fuel Supply Company — Pipeline Safety Interpretation

Page 1December 31, 1975 Mr. F. F. Bassani Mountain Fuel Supply Company 625 Connecticut Avenue Rock Springs, WY 82901 Dear Mr. Bassani: This is in response to your request for an interpretation of Section 192.505. You asked, "After performing a hydrostatic test of a portion of a new pipeline to 125 percent of M.A.O.P., would it then be permissible to conduct a pressure test of a section of a new pipeline, which includes the above-mentioned section hydrostatically tested, to a test pressure near 80 percent of SMYS using natural gas as the testing medium?" Your letter states that the section to be hydrostatically tested is located within 300 feet of four houses and the entire pipeline to be tested is in a Class 1 location. As Lloyd Ulrich of our Office notified you by telephone on December 2, 1975, Section 192.505 implicitly prohibits a test with natural gas to a hoop stress of 30 percent or more of SMYS in a Class 1 or Class 2 location where buildings intended for human occupancy are located within 300 feet of a pipeline. In such locations, Section 192.505 requires a hydrostatic test to a level of at least 125 percent of maximum operating pressure. However, if the buildings are evacuated while the hoop stress exceeds 50 percent of SMYS, air or inert gas may be used as the test medium. Natural gas is not included in Section 192.505 as an allowable test medium to protect the public where buildings intended for human occupancy are located within 300 feet of a pipeline. Further, as indicated by Mr. Ulrich, the highest stress allowed in the pipeline at such a location as described above while it contains natural gas is 72 percent of SMYS, and that stress is allowed only when that segment of the pipeline has been successfully tested hydrostatically to a minimum of 90 percent of SMYS. A test to that stress level would qualify that segment of the pipeline to operate at a stress level of 72 percent of SMYS in a Class 1 location. Since 125 percent of 72 percent is 90 percent, the test would also satisfy the requirement in Section 192.505 concerning testing so at least 125 percent of maximum dal\192\505\75-12-31 1#

Page 2operating pressure where buildings for human occupancy are located within 300 feet of the pipeline. I trust this answers your question. Thank you for your interest in pipeline safety. Sincerely, Cesar DeLeon Acting Director Office of Pipeline Safety Operations dal\192\505\75-12-31 2#