Pollution
Humain
Environnement
Economique

A potassium cyanate bath used to treat parts in a surface treatment workshop boiled over and flowed into a bund located directly underneath. The potassium cyanate reacted with the water in the bund, releasing hydrogen cyanide fumes. The 74 people in the workshop were evacuated. The power supply was cut off to make the bath stop overflowing and natural ventilation was used to draw the fumes outdoors. One employee inhaled some of the fumes. Activities on the rest of the site resumed a few hours after the firefighters arrived.

The bath overheated because the bath’s fuse rod became damaged when parts were added to the bath. In addition, in order to add the parts, the temperature sensor had to be removed from the bath. The technician who did this was still in training and failed to put the sensor back in the bath. As a result, the temperature of the bath was not controlled.

The operator planned to resume the technician’s training and implement a quarterly maintenance check of fuse rods in addition to a weekly visual check. It also planned to fit a better fuse rod protection system and install an interlock which would prevent heating unless the sensors and fuse rods were in the baths. Ultimately, the technical difficulties related to implementing these solutions in an ageing workshop and the start-up of a new surface treatment line led the operator the shut the workshop down. However, it revised the training plan, added special training for the new workshop’s operators, and implemented a problem reporting tool.