NTSB Safety Recommendation Letter P-76-039 through P-76-041

Page 1Official PDFWASHINGTON, D.C. CORRECTED COPY 1SSUED: August 5, 1976 REISSUED: August 2 0 , 1976 _______________I_________l_________l____ Forwarded to: Mr. w. L. mmtt Major Manager Dm Chemical U. S .A. SAFETY RECOMMENDAT I ON (5) Freeport, Texas 77541 P-76-39 thrauph P-76-47 A t 12:28 p.m” on May 12, 1975, an 8-inch pipeline, which was closed i n under pressure and which was m e d by Em Chemical U.S.A and operated as the Bronco Pipe Line Canpany, ruptured near Devers, Texas. Natural gas liquids at 1,425 psig pressure errupted 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 southwest over U. S. Highway 90. An automobile entered the vapor cloud and ignited the ethane-propane vapors. The resulting explosion and fire killed the four persons in the automobile, melted telepbne and electric pmer lines, warped railroad tracks, burned and scorched adjacent woodlands, and interrupted rail and highway traffic. The National Transportation Safety Board detemines 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 i n the pipe; the pipe w a s gouged by a backhoe when valve assemblies were installed in the line. The failure was caused by a c d i n a t i o n of reduction in wall thickness, residual bending and tensile stresses, and fatigue due t o the cylic loading of the pipe. The escaping L E 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 awae that the line had been gouged when valves were installed on the Texas Division’s section. naJ alsohad not provided far rapid shutdm of the system in the event of an e r g e n c y , it did not have equipment t o transmit pressure data to the dispatchers in accordance w i t h 49 CFR 195, and it did not utilize the total system concept to design or operate this pipeline.#

Page 2- 2 - Therefore, tbe National Transportation Safety Board recorrmends that the Dow Chemical U.S.A. : Initiate necessary equipnerit changes to provide data necessary for the safe operation of the pipeline continuously t o the dispatch centers. (P-76-39) (Class 11, Priority Followup) Review periodically with local f i r e departments and other interested agencies the pipeline location, bas pipeline operations, materials transported, hazards encountered and procedures to follow during leaks (P-76-40) ( C l a s s 11, Priority Followup) Use the total system concept t o review day-to-day operations, new projects, and maintenance-operations in order t o assist in recognizing and controlling potentially hazardous conditions. (P-76-41) ( C l a s s 11, Priority Follmn~p) TODD, L h i m , McADAMS, HOGUE concurred in the above rercmendati ESS, AND "i, Members By: NAIIONAL IRANSPORPAIION SAFETY BOARD WASHINGTON D C ?OS94 OFFICIAL nU51NESS PENALTY FOB PRIVAIE USE. 1300 POSTA(10 I X D TEES PI10#