An explosion followed by a filter fire occurred at around 2:30 p.m. in a tin powder manufacturing workshop in a metallurgical company. The powder is produced by atomising molten tin with high-pressure air and then drying it in a cyclone separator. Dust is then removed from the releases by a cartridge filter. The maintenance manager interrupted the building’s gas and electricity supplies, and the public emergency services were alerted. The establishment’s 45 employees were evacuated and the firefighters established a safety perimeter of 100 m and closed off the compressed air supply valve at the back of the filter. All containers and hoppers containing tin power were removed from the workshop. The decision was then made to allow the filter to burn out completely. The fire was put out at around 4:30 p.m. No injuries were reported; only the filter system was damaged.
According to the operator, an electrostatic phenomenon consisting of the source of ignition and a saturation of the filter cartridges with metallic dust (replacement scheduled in April 2014) may have been the origin of the accident. It was noted that on the day of the event, the filters were heavily clogged. This excess dust, despite the automatic unloading operations, would have been aggravated by the high degree of humidity in the outside air used in the process.
Following the accident, the operator planned the following:
- heating of the workshop 24/7, whereas up until now it had only been operating during the two shifts (2 x 8 hours) and use of the hot air from the building’s compressors in the process,
- monthly visual inspection of filter clogging and annual replacement of the filter cartridge,
- installation of a flow meter on the filter outlet,
- installation of emergency stop buttons on the utilities on the outside of the workshop and control of the opening of the explosion vents above the filter when the utilities are switched off,
- a study, with the manufacturer, to improve the cyclone’s efficiency.