At approximately 4:30am on Oct. 4, 1971, a woman who resided in a small frame house at 2109 Amanda Street in Fort Worth, lit a gas stove in her kitchen. A violent explosion blew off the roof and blew out the four walls of the house. The roof fell back into the burning rubble and the house was completely destroyed. The woman suffered severe burns.
The Fort Worth Fire Department arrived on the scene at 4:38am and the fire was extinguished shortly therafter. The gas company employees arrived at 5:10, initiated a leak search, and discovered five ruptures in the plastic pipe distribution system that served the area. Each of these ruptures had a 1/8 inch wide crack which extended across the top half of the pipe circumfrance. The rupture which caused the accident was in the service line which supplied has to the house across the street.
We determined that the probable cause of the explosion and fire was the ignition of an accumulation of natural gas which had migrated under a pressure of 20 p.s.i.g. from a failed plastic service saddle-tapping nipple connection into the house.
Contributing to the failure of the connection were its improper installation, previously imposed load stresses which resulted from the repeated operation of heavy construction equipment over the connection, and heavy rainfall which caused the soil to exert pressure on the pipe.
As a result of this investigation, we made the following safety recommendations.
To the Office of Pipeline Safety of the Department of Transportation: Undertake a study in the field of heat fusion of plastics and, as a result of that study, issue regulations for the heat-fusion welding of plastic piping system in 49 CRF Part 192, fusion welding, in as much detail as is contained in the existing welding specification for steel piping systems. (P-73-63)
To the American Society of Mechanical Engineers Gas Piping Standards Committee:
- Develop guidelines for the use of reinforcing sleeves at plastic service lin-gas main connections and incorporate them in the "Guide for Gas Transmission and Distrubution Piping Systems" (P-73-64)
- Develop guidelines for the requirements concerning reinforcement, special backfill, and tamping of mains and service lines where their installatino will be subjected to external forces due to anticipated road, curb, or sidewalk construction, as well as unstable conditions. (P-73-65)
To the Lone Star Gas Company:
- Revise its plastic pipe constuction specifications to include the specific type and size reinforcing sleeve to be used with each type of service saddle-tapping nipple connection. (P-73-66)
- Educate its construction inspectors as to the necessity for correct installation plastic piping systems.(P-73-67)
- Undertake a program actable to the Railroad Commission of the State of Texas, to inspect on a random sample basis the plastic service line-gas main connections, similar to those at the accident site to determine the present condictoin of and the existing stress on the piping. The results should be forwarded to the Railroad Commission of the State of Texas and the Office of Pipeline Safety of the Department of Transportation. (P-73-68)
