In a chemical plant specialising in basic plastic materials, a fire broke out at around 9:25 a.m. on a grease extraction hopper in the “grease recovery” section downstream from the polymerisation reactor and on a line in the polyethylene workshop. This workshop, which produces copolymers, had been running for 5 hours after a period of work. The flames in the area around the grease hopper were billowing black smoke (slick on fire). The unit’s technicians attempted to put out the fire with ball-type extinguishers, but the fire increased in intensity at 9:42 a.m. (shooting flame). The facility operator initiated the internal contingency plan, secured the unit by releasing the pressure in the line and stopped the flow of thermal fluid. The unit’s 6 technicians were evacuated to the control room. The emergency services were notified, although the site’s fire brigade was able to bring the fire under control at 10:05 a.m. The heart of the fire was finally extinguished at 11:44 a.m. A cubic metre of thermal fluid and just less than 3 t of ethylene were burned. No victims were reported, but the hopper and neighbouring equipment suffered significant material damage, estimated at 3.6M Euros. The production line was shut down for 4 months.
The operator’s investigation showed that insulation impregnated with hot heat transfer fluid probably caught fire. The ignition of the heat transfer fluid at 180 °C (temperature of the fluid line’s operating conditions), although lower than its self-ignition temperature (500 °C) was caused by the insulation being impregnated with fluid, which lowers its self-ignition temperature. The heat released by the fire resulted in deformation and leakage of equipment containing pressurized ethylene, which in turn ignited, increasing the intensity of the initial fire (shooting flame).
The operator reinforced inspections during restart operations after the gas system is opened, with continuous monitoring of the area before and several hours after the restart (once stable operation has been reached) using state-of-the-art cameras and fire detectors. The heat transfer fluid system was also simplified and the insulation on the flanges of the thermal fluid line removed (the most likely leakage zone).