At a research facility engaged in pyrometallurgical activities for the purpose of developing or improving metal fabrication processes, an overflow occurred around 7 am at the time of pocket casting during a pilot run to free phosphorus from manganese ore. The molten slag (at 1,200°C) spilled into a channel and ignited the plastic sheathing of instrumentation cables, as well as grease from the pocket carriage traction chain. The 4 technicians suspended the energy intake lines to the installations and removed the casting walkway. Municipal first responders extinguished the fire in 90 minutes using 2 of the site’s 50-kg powder extinguishers. Testing resumed around 8 pm once the equipment had been refurbished.

According to the facility operator, a process problem had been diagnosed 36 hours earlier: formation of “benches” (a solid and hard layer) on top of the metal bath. The technicians were ready to plug the casting hole when the volume and flow rate of the jet stream suddenly spiked. After 3 fruitless attempts at plugging the hole, the pocket overflowed as its capacity proved insufficient. An unfastened “bench” in the electrical furnace placing pressure on the molten liquid bath was one hypothesis forwarded.

Subsequent to the incident, several organisational and technical measures were adopted: introducing a procedure to better control the process (“return to steady-state operations in case of malfunction”), implementing a retention basin to handle spill incidents, removing cables running below the casting pockets and spouts, and improving training for technicians and foremen regarding operating incidents. An emergency protocol for plugging the casting hole and new blast furnace monitoring indicators were also evaluated.