At around 2.40 p.m., a fire broke out on a propellant disc during an operation of cutting to length a propellant block for a rocket motor in an arms factory. The propellant block that reacted is a double-base nitrocellulose and nitroglycerin propellant, with the presence of a lead-base organometallic compound. The component on fire fell into the swarf scrap bin. The unit was inerted and the pyrotechnic products in progress were evacuated.

The disc cut out by cutting to length was not removed correctly, and it remained blocked under the cutter gang, thereby causing a cutter attack on the unclamped cut-out disc: excessive friction causing fire initiation. As regards the manufacturing in progress, the propellant block to be machined was shorter than usual and a recent tool change had resulted two days earlier in discs blocked under the cutter gang (poor removal). The information had indeed been reported in a production supervision meeting on the very morning of the incident, but had not given rise to immediate action or a production stoppage.
Moreover, when inerting the unit, another problem was highlighted at the level of the machining swarf removal system which showed an abnormal presence of cut-out discs with a phenomenon of accumulation at the level of the exhaust flue.

Following the event, the operator took the following actions:

• improvement in acting on information feedback;
• tool change to prevent the phenomenon of potential disc blockage;
• addition of a physical barrier preventing the exhausting of these cut-out discs by the exhaust system reserved exclusively for machining swarf;
• modification of the disc recovery chute.