NTSB Safety Recommendation Letter P-85-029

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. I S S U E D : November 27, 1985 Mr. Michael J. Kammerer President Dresser Manufacturing Division Dresser Industries, Inc. 41 Fisher Avenue Bradford, Pennsylvania 16701 i SAFETY RECOMMENDAT l O N ( S ) P-85-29 - A t 2:40 a.m., on February 22, 1985, a police patrolman on routine patrol smelled strong natural gas odors as he crossed railroad tracks while heading south on North Sixth Street in Sharpsville, Pennsylvania. He radioed this information to the Sharpsville Police Department dispatcher a t 2:42 a.m.; the dispatcher relayed the information to the National Fuel Gas Company (gas company) by telephone at 2:43 a.m., and a gas serviceman was ordered to the scene. A t 3:15 a.m., before the serviceman arrived a t the site of the reported leak, a tavern and a connecting building exploded and burned, killing two persons. Firefighters arriving onscene moments later encountered a second, smaller explosion which injured one firefighter. Gas company personnel shut off the gas to the leak site at 4:15 a.m. - 11 Company maps showed that there was a 6-ineh-diameter, high-pressure, polyethylene plastic gas main under North Sixth Street at the railroad track crossing. After the relighting process was begun, a gas company crew began t o excavate in North Sixth Street south of the railroad tracks where the blowing gas had been observed. The plastic gas main was uncovered. A coupling used t o join the lengths of plastic pipe was located 37 inches south of the open end of an 8-inch-diameter steel casing pipe in which the 6-inch-diameter plastic gas main was installed under the railroad tracks. The plastic pipe had pulled 3/4 inch out of t h e north end of the coupling. The Dresser 700 "posi-hold" coupling involved in this accident was manufactured in 1975 through 1978 in 2-, 3-, 4-, and 6-inch diameters and employed a plain roller-grip gasket in each end. The 6-inch-diameter, 7-inch-long coupling involved in this accident was intended for joining steel piping or plastic piping interchangeably when installed in accordance with the manufacturer's installation instructions and product ratings. The Dresser 700 "posi-hold" couplings were sold only t o the Columbia Gas Company (Columbia Gas) and National Fuel. A total of 4,389 2-inch-diameter couplings, 5,553 3-inch- diameter couplings, 6,629 4-inch-diameter couplings, and 821 6-inch-diameter couplings were sold t o these two companies. The couplings were not designed t o restrain plastic pipe until the pipe failed; the coupling involved in this accident was rated to restrain plastic pipe up t o 2,700 pounds of tensile force (pull). - 11 For more detailed information, read Pipeline Accident Report-"National Fuel Gas Company, Natural Gas Explosion and Fire, Sharpsville, Pennsylvania, February 22, 1985" (NTSBIPAR-85/02). 4121Bl299#

Page 2-2- Dresser salespersons did not have occasion to point out the fact that the coupling had limitations, because they did not solicit the sale of the coupiings to any company other than Columbia Gas. National Fuel bought these couplings directly as a result of talking with Columbia Gas, because, it also saw the advantage of using one type of coupling t o eliminate the possibiJity of an error in selecting the correct coupling t o join different types of pipe. Dresser's advertisement that its "joint will restrain pullout until the pipe fails outside the coupling" applied only t o one style of coupling and not to the 700 "posi-hold" coupling with plain roller-grip gaskets involved in this accident. National Fuel should have been concerned about the stresses caused by contraction in the plastic pipe and should have made the appropriate calculations. The gas company could have requested information about the limitations of the coupling from Dresser's Technical Services Department; it did not avail itself of this service. In turn, had Dresser's sales organization been made aware of the sale of the coupling t o National Fuel, it is likely, given Dresser's practices, that Dresser would have contacted the gas company t o describe the coupling's capabilities and limitations. The gas company engineering department never calculated the contraction forces which would be caused by predictable temperature drops in the area where the plastic pipe was to be installed. Moreover, it did not calculate the forces or potential forces that would be exerted on the coupling; it assumed that the coupling would hold the pipe against all forces, and as a result, the gas company installed 1,500 feet of 6-inch-diameter plastic pipe with five couplings that it assumed would hold so long as the forces did not exceed the rating of the pipe. However, the contraction forces of the plastic pipe exceeded the restraining force of the coupling, and a pullout resulted. In an era when the use of plastic pipe is expanding rapidly in the gas distribution industry, it is imperative that gas companies become completely familiar with the forces that act upon pipe and the limitations of using couplings with the pipe. Company engineers must consider these factors carefully in their design calculations. Also, coupling and plastic pipe suppliers should make available to gas companies the full range of information on their products' limitations, as well as their products' virtues, so that there will be no question of what the products can and cannot do. The availability of information about product capabilities and product limitations becomes even more important as product changes and innovations are made by the supplier. The new information must be made available promptly t o the ultimate user, and the user must install t h e product only after careful consideration of its capability. in this case the new coupling's limitation (the fact that it might pull out before pipe failure) should have been evaluated fully by the gas company; the gas company also should have calculated t h e forces of contraction on the plastic pipe to determine if the pipe would need anchoring t o prevent pullout. The calculation was not made; the gas company apparently concluded--based on Dresser's statement related t o another line of couplings--that this coupling would hold until the pipe failed. Therefore, the National Transportation Safety Board recommends that t h e Dresser Manufacturing Division of Dresser Industries, Inc.: Review its intercompany communication practices, and revise them where necessary t o ensure that customers ordering a new or modified product will be advised of the product's limitations. (Class 11, Priority Action) (P-85-29)#

Page 3-3- The National Transportation Safety Board is an independent Federal agency with the statutory responsibility 'I. . . to promote transportation Safety by conducting independent accident investigations and by formulating safety imprOVement recommendations" (Public Law 93-633). The Safety Board is vitally interested in any actions taken as a result of its safety recommendations and would,appreciate a response from you regarding action taken or contemplated with respect to the recommendation in this letter. Please refer to Safety Recommendation P-85-'29 in your reply. BURNETT, Chairman, GQLDMAN, Vice Chairman, and BURSLEY, Member, concurred in this recommendation.#