NTSB Safety Recommendation Letter P-76-048 through P-76-055

Page 1Official PDFNATIONAL TRANSPORTATION SAFETY BOARD WASHINGTON, D.C. I S S U E D : September 15, 1976 Mr. Oliver Peden President Nebraska Natural Gas Company 340 East Military Fremont, Nebraska 68026 SAFETY RECOMMENDAT I O N ( S I P-76-48 through P-76-55 A t 9:32 a.m. on January 10, 1976, gas which w a s leaking into the Pathfinder Hotel, in Frerrmnt, Nebraska, ignited. The gas was leaking frcm a 2-inch plastic pipe which had pulled out of its can- pression coupling; the gas seeped into the hotel because it had been capped above by frozen earth and a concrete road surface. The hotel exploded and fire ensued; the explosion and f i r e destroyed the hotel, damaged nearby buildings, and broke windaws within a one-block radius. Thirty-nine persons were injured and 20 persons were killed. - l/ A 348-foot-long 2-inch plastic main was inserted in an existi % 4-inch steel main on June 26, 1974, when the air temperature was 86 and the minimm g r d temperature was interpolated fran engineering handbooks to be 609. A t the time of the accident, the g r m d tem- perature was 36OF. This 24OF temperature change caused the pipe t o contract. If the pipe had been unrestrained, it could have contracted. up to 94 inches the f i r s t year. Hmever, the seven service lines attached to it and the restraints of the compression coupling allowed the plastic pipe t o move only 14, inch within one of the couplings during the first winter after installation. W i n g the second win- ter, the plastic pipe pulled completely out of this coupling which was in front of the hotel, and caused the accident. The plastic pipe mufacturer r e c m n d s that proprietary tran- sition fittings or pipe-to-casing anchors be used t o l i m i t the con- - l/ For more detailed information on this accident, read "Pipeline Accident Report -- Nebraska Natural Gas Carpany, Pathfinder Hotel Explosion and Fire, Fremont, Nebraska, January 10, 1976." NTSB- PAR-76-6. 174lA#

Page 2- 2 - traction of plastic pipe inserts which are over 100 feet long. Nebraska Natural Gas Company did not have any detailed procedures for constructing plastic pipe-compression coupling joints. The Persons detected gas over 4 hours before gas company personn arrived a t the hotel. Because two of the three servicemen who were on c a l l for the weekend were away from their telephones, there was an exceptionally long delay of 1 hour before the gas company responded t o the emrgency c a l l from the hotel. On-call s e r v i c e n had not been trained to classify leaks as t o the degree of hazard or traine with regard t o emrgency procedures. Delays i n locating the leak were also created because the vehicles of the on-call emergency servicemen were not equipped with combustible gas indicators, blo cards t o show gas facilities, or distribution system maps. Since there were not enough high-pressure distribution valves and since their locations were unknown, there was a 5-hour delay in shutting d m gas service to the accident area after the hotel ex- ploded, and half of Fremont had to be shut down to isolate the hotel area Therefore, the National Transportation Safety Board reccxmnds that the Nebraska Natural Gas Company: Use m u f a c t u r e r ' s proprietary transition fittings, in- stalled i n accordance with written procedures, or use pipe-to-casing anchors to l i m i t contraction of plastic pipe, until a compression coupling is verified by tests to be as strong as the plastic pipe being joined. (P-76-48) (Class 11, Priority Foll~w~.~p) Develop written procedures and an inspection program to insure that a l l plastic pipe joints m e t the &sign and installation provisions of 49 CFR 192(F), "Joining of materials by mans other than welding." (P-76-49) (Class 11, Priority Follauup) Revise the company's written procedures t o include the maxinnrm length of plastic pipe to be used with compre couplings, the nuher of foot-pounds of torque requir for each size of compression coupling, a time interva during construction between retorquing of couplings, the type of stiffener to be used w i t h each brand of c pling (P-76-50) (Class 11, Priority Followup) Uevelop written procedures to handle gas leak aner and evacuation, and instruct operating and mainten employees as t o their roles in carrying out these proce d u e s . (P-76-51) (Class 11, Priority Follauup)#

Page 3- 3 - Develop a procedure to shut down the system during emer- gencies. As part of this procedure, develop distribution system maps shming valve locations, determine o p t b spacing of high-pressure valves in each of the NNC, dis- tribution systems, and install additional valves, if neces- sary, to reduce the time required to shut down a section of main i n an emergency (P-76-52) ( C l a s s 11, Priority Followup) Develop a method of receiving anergency telephone calls in order t o assure inmediate response to emergencies. The method should include logging of a l l emrgency calls. (P-76-53) (Class 11, Priority Followup) Improve the customer education program and liaison between the gas company, the police, and the f i r e departments. Include in written procedures the mthods for notifying police and f i r e depar-ts of gas emergencies and the planned responses to them. (P-76-54) (Class 11, Priority Followup) Equip emergency vehicles w i t h c d u s t i b l e gas leak detec- tors, distribution maps, and other necessary work tools. (P-76-55) (Class 11, Priority Followup) TODD, Chairman, MCADAMS, HOC;LlF,, BURGFSS, andHAIEY, Members, concurred in the above recmndations. BV: Chairman I io342#