Aluminium starter motors often struggle to obtain ATEX approval. The latest ATEX guidelines strongly discourage its use:
“Friction impacts … involving … light metals (e.g. aluminium and magnesium) … may initiate an aluminothermic (thermite) reaction which can give rise to particularly incendive sparking.”
Aluminium is one of the primary fuels for creating a thermite reaction. It’s a chemical process that gives off so much heat it’s used to weld railway tracks. When aluminium is mixed with an oxidiser such as iron(III) oxide (known to you and me as rust) and is ignited by heat or a spark the reaction produces a molten metal at about 3000°C!
If water is used to try and extinguish the reaction, explosive hydrogen gas can be produced.
The chance of so many unfortunate coincidences happening is very remote. Unfortunately, when we review accident reports we often see that they happen because of just such a series of unhappy coincidences. Health and safety regulations like ATEX are designed to eliminate such risks.
With this in mind, ATEX regulations simply recommend against using aluminium. In many parts of the world, aluminium is actually banned from underground mines.This is certainly the case in the USA where thermite reactions were responsible for 11 mine explosions in the 1950s. It is inviting another disaster to put aluminium and rust together in a mine, on an oil platform or in any other potentially explosive atmosphere.
So, what’s the alternative to an aluminium starter motor when you need safe reliable starting in a hazardous environment? The answer is cast iron.
IPU’s ATEX approved starter motors are made from a cast iron construction to eliminate any external-facing aluminium. They are also pre-engaged, which means the starter motor waits until the pinion has engaged with the ring-gear before rotating and cranking the engine. This eliminates the risk of sparks being generated by traditional inertia engagement.
Many underground vehicles, wire lines and cranes use hydraulic starting systems because they have existing hydraulic systems in place on the vehicle or crane. Adding the hydraulic starter is straight-forward. Because hydraulic starting systems are self-contained and sealed they are ideal for use underground and in dusty environments.
Air starting systems are more popular where no hydraulic systems are in place, and many are used offshore and in marine and shipping industry where there is an abundance of air which can easily be used.