Accident at work: explosion in a grain mill
What happened: the grain mill underwent reconstruction work, during which it was necessary to remove some metal structures. Gas cutting was used to remove the structures. When the cable ladders under the ceiling were cut open, the grain dust accumulated on them began to fall. From the flame of the gas cutter, grain dust ignited and then exploded. As a result, the worker operating the gas cutter suffered burns to both their head and hands.
Why it happened: apparently the falling grain dust in the air formed a mixture of air and dust with a concentration in the explosion range, which caused an explosion in addition to ignition. Prior to the start of the work, the floor and other details had been moistened with water, but the danger posed by the removal of the dust layer accumulated on the structures and the dispersion in the air when moving the structures had not been taken into account.
An occupational safety plan was prepared for the works. It listed the dangers of gas welding. These included ignition and explosion. Measures to reduce the risk were also planned, but there were no measures to prevent ignition or explosion. Pre-work irrigation of surfaces with water was not sufficient to avoid the risk of ignition.
There were other shortcomings in the occupational safety plan. For example, the risk of ignition was assessed as probable and the possible consequences as severe. Despite the likelihood of serious injury, the risk of ignition was only assessed as moderate and work began.
In grain mills, the risk of explosion due to grain dust must be assessed very thoroughly. In addition to the use of a gas cutter and a disc cutter, sources of ignition may include, for example, an overheated bearing and electrical equipment and installations.