(213a) A Case Study of a TFE Explosion in a PTFE Manufacturing Facility

A 1999 explosion in the purification area of a fluorinated polymer manufacturing plant in the United States caused three fatalities to employees. An additional employee was also severely injured. The affected plant personnel were attempting to locate a suspected polymer plug in lines containing Tetrafluoroethylene (TFE) monomer in a section of the process upstream of the polymerization plant. In an attempt to dislodge a possible plug in an elbow leading off of a pressure vessel, one employee rapidly actuated a manually operated ball valve. High-pressure TFE upstream of the valve rushed into the downstream piping, which likely contained air at less than atmospheric pressure. Adiabatic compression caused temperatures sufficient to ignite a TFE-air deflagration. The initial deflagration provided sufficient energy for a self-sustaining decomposition reaction wave to propagate within the TFE line into a pressure vessel upstream. Liquid TFE had been collecting in the pressure vessel due to a deliberate increase in the flow of cooling brine associated with a separate process. The presence of liquid TFE in the pressure vessel allowed the decomposition to continue, causing a rapid increase in pressure inside the vessel, sufficient to fail the bolts on the upper flange, sending the top of the vessel through the ceiling. The four employees were exposed to burning TFE sprayed from the pressure vessel and were also injured by shrapnel created by the explosion. Exponent Failure Analysis Associates was retained to conduct an engineering investigation of the incident, including a technical analysis of the conditions leading to the explosion. We also reviewed the HAZOP performed by the employer that failed to note critical parameters that contributed to the incident. This paper discusses our findings as well as lessons on handling TFE that can be learned from the incident.