In a factory that produces food dips, a worker decided to open a machine cover to clean out an area of the production line. The area of the production line to be cleaned had a conveyor belt which fed consumer-size containers of the dip to a roller that applied and sealed a thin clear film. The containers of dip would then drop down to get a lid placed on top and exit the line via a lower conveyor belt. The roller was spinning well above 60 rpm, and the conveyor belt was moving the containers at an equal linear pace. The worker opened the machine cover while the line was running, stuck his hand inside and was struck by the rotating roller causing a severe hand injury.
Based on the evidence inspection, the entire production line was enclosed and guarded with plexiglass access doors. The doors were interlocked to the production line controller, such that opening any of the doors would halt the line.
There were no reports of a failure of the interlocks and no history of maintenance on the interlocks.
The interlocks worked by the stationary sensor sensing a magnet attached to the door. The only way the worker could have accessed the area where the incident occurred was to have tested several magnets in order to find one that could fool the stationary sensor. Furthermore, even if one were to assume that an interlock somehow failed, the worker could visually see the line running, yet chose to stick his hand in the pinch/collision point. Additionally, there were several emergency stop buttons available around the machine, as well as a machine lock-out/tag-out station that the worker could have engaged if he wished to stop the line in order to access an area he wanted to clean.