NTSB Safety Recommendation Letter P-76-042

Page 1Official PDFWASHINGTON, D.C. CORRECTED COPY I S S U E D : August 5, 1 9 7 6 REISSUED: August 2 0 , 1 9 7 6 Mrihr. FrankN. Ikard President American Petroleum Institute 2101 L. Street, N.W. Washington, D. C. SAFETY RECOMMENDATION (S) A t 12:28 p.m. on May 12, 1975, an 8-inch pipeline, which was closed in under pressure and which was awned by Dow Chemical U.S.A and operated as the Bronco Pipe Line Company, ruptured near Devers, Texas. Natural gas liquids a t 1,425 psig pressure e r q t e d from a fracture near the top of the pipe. The liquids vaporized, mixed w i t h air, and formed a cloud which drifted to the smthwest over U. S. Highway 90. An automobile entered the vapor cloud and ignited the ethane-propane vapors. The resulting explosion and f i r e killed the four persons i n the a u t m b i l e , m l t e d telephone and electric power lines, warped railroad tracks, burned and scorched ad,jacent woodlands, and interrupted rail and highway traffic. The National Transportation Safety Board determines that the probable cause of the accident was the rupturing of the 8-inch pipe i n an area of stress concentration caused by a gouge in the pipe; the pipe was gouged by a backhoe when valve a s s d l i e s were installed in the line. The failure was caused by a combination of reduction i n w a l l thickness, residual bending and tensile stresses, and fatigue due to the cylic loading of the pipe. The escaping LFG vapors were ignited by an automobile which entered the vapor rich zone. DOW had not inspected the line adequately during construction; consequently, it was not aware that the line had been gouged when valves were installed on the Texas Division's section. WW also had not pruvided for rapid shut- of the system in the event of an emrgency, it did not have equipnmt to transmit pressure data to the dispatchers in accordance w i t h 49 CFR 195, and it did not utilize the total systems concept to design or operate t h i s pipeline. 1850#

Page 2- 2 - Tlle Safety Board, on May the American Petroleum Insti Systemtic Approach to Pipe1 the development of guideline pipeline operators. Tlds is Board's reccwnendatiori was of the techniques of syst which led to t h i s accident. Therefore, the Nati that the American Petrolem Institute: 1. InrpleoEnt Special Study on "A Systematic Approach to P Safety." (P-76-42) (Class 11, Priority Fol TODD, L- , McADAMS, HELIE, BURGESS, arid HALEY, M-?rs, concurred in the above recormtendation. NAIIONAL IIUNSPORIAIION SAFETY BOARD WASHINGTON. D C 20294 OFFICIAL DUSINESS PENALTY FOR PRIVATE USE. 8300#