Explosion in a metals processing plant due to unexpected hydrogen production

An explosion occurred in the venting system of a metal grinding CNC-unit. The explosion has been attributed to the unexpected reaction between the water used for the cooling of the grinding and the powder produced by the unit, with the production of hydrogen. The powder consisted in aluminium, magnesium and silicium.
The local fire brigade intervened (6 vehicles and 27 persons). The clearing of the emergency required to extract the hydrogen-air mixture from the venting system. The fire department deployed an explosion-proof suction device.
Nobody was injured.

The INITATING CAUSE was the unintended hydrogen production from a reaction between metal powder and cooling water.

The ROOT CAUSE cannot be identified (yet). It can be assumed that this was a unique case, and that the unit had worked before without this type of incidents. It is unknown if and which modifications to the usual process could have brought to the electrolysis of water in presence of dust.

grinding machine

Nothing known on the amount of damage. Probably, only the vent duck or system was affected.

No specific Lesson Learnt possible, in absence of details on the process, its procedures, the possible changes occurred on the day of the incident and the process parameters. It is known that very fine metal powder, possibly in a dust cloud, is very reactive to explosive oxidation. The assumption made by the fire brigade to explain the explosion is the occurrence of an oxidation reaction between water and the metallic powder, with production of hydrogen which then ignited and exploded. The report, however, does not mention a direct confirmation of presence of hydrogen.