The recent prosecution of Renishaw by the Health and Safety Executive has brought back to light the dangers present for engineering businesses from the mixture of fine dusts which they can create.
It would be true to say that the dangers of mixing metal powder and water would be lost on most staff within these businesses, accidents are typically followed by a moment when those concerned remember from the dim and distant past what could occur. For this reasons it is worth re-examining the risks and exploring what situation could give rise to a fire.
Worker injured in fire and explosion caused by metal dust
In the case of Renishaw the incident involved aluminium powder and a specialist vacuum cleaner (but this could just as easily have been a simple wet and dry vacuum which could be present in almost any engineering business).
A worker had used the vacuum to remove some fine aluminium dust from a workbench. Water was present in the waste container of the vacuum and the worker may or may not have been aware of this fact. The container was not emptied but left to stand over a weekend, during which time the aluminium powder reacted with the water to give off hydrogen gas.
When the machine was switched on it ignited the hydrogen gas cause a fire and explosion which resulted in a two week hospital stay for the employee.
Mixing of other metal dusts which could lead to fire and explosion
Combustible metals that are common in manufacturing and machining operations include aluminum, lithium, magnesium, niobium, tantalum, titanium, zirconium, and cold rolled steel.
One particularly vigorous reaction which you must seek to avoid is aluminium and steel. Their combination produces a ‘thermite’ like reaction (thermite is actually iron oxide and aluminium) which is very difficult to control and results in a huge amount of heat energy.
Situations which could give rise to fires in engineering and manufacturing businesses which you may not have considered
One area which is often overlooked is the build up of aluminium and steel within the extract system itself, particularly if it is heavily used or if maintenance has been lacking. The mixture of the steel and aluminium dusts can start a ferocious fire.
If you’ve got questions or need support on safety in the industrial, contracting or construction sectors please contact us for sensible and proportionate advice on 01453 800100