In a plant producing MS polymer (silane polyoxypropylene)-based mastics, the malfunction of an electronic box between the temperature probe and the numerical display caused a loss of the current manufacturing run. The production process actually needed to be heated to 110°C in order to obtain a good dispersion of both carbon black and calcium carbonate in the mastic. Once this phase had been achieved, the temperature should have been maintained, by means of regulating the heat of the mixer’s double shell, for 90 min to ensure complete homogenisation. Since the temperature probe was blocked at 110°C, no regulation was applied and the mix continued to heat until a temperature estimated at 250°C.

The engineer present on the platform realised the anomaly and activated an internal procedure that called for contacting the HSE Director, who gave the following instructions:

• introduction of an inert nitrogen atmosphere to avoid any ignition risk, cooling with carbon ice, and then immersion of the mix in water by the site response team along with permanent monitoring until a temperature of 30°C
• simultaneous notification of the fire department to allocate the requisite resources and skills
• monitoring of the 8 individuals present in the workshop.

Following medical exams, all workshop personnel were certified as capable of resuming work immediately. The toll of this incident amounted to: loss of the current batch (1.5 t of mastic), time spent cleaning the tank, and cost of waste disposal.