40 x 40 mm Light Aluminium Profile for Mining Equipment

01What does an underground environment do that a workshop does not?

Three things, and only one of them is about load. The first is abrasive dust, which gets into every open profile in the first shift and does not come out. The second is impact, not from a designed load but from a rock, a bucket or a boot. The third is humidity, which in a deep mine is often close to saturation and stays there.

The structural consequence is that a frame designed for a calculated load is being asked the wrong question. It will not fail from the load. It will fail from a dent, a blocked slot, or a fixing that has corroded because water sat in it.

02Where does the 1.30 kg/m mass saving actually pay?

Not on a fixed guard. On a fixed frame the difference between 1.30 and 2.35 kg/m is about 6 kg over 6 m, and nobody notices 6 kg. The saving pays when the frame is on a moving part, because mass there is multiplied twice: once by the acceleration to move it, and again by the structure upstream that has to carry it.

A guard on a boom is the clear case. Every kilogram on the boom is a kilogram the boom hydraulics accelerate, and often a kilogram the boom section has to be sized for. Cutting the guard from 2.35 to 1.30 kg/m can take 6 kg off the end of an arm, which is worth more than 6 kg at the pivot.

• On a fixed frame, choose the section for stiffness and ignore the mass.
• On a moving part, choose the thinnest wall that meets the stiffness and impact requirement, then check the impact case separately.
• Remember that a thinner wall deforms earlier under impact. On a moving guard that is often acceptable because the guard is a consumable.
• Do not go to the thin wall for a member that carries another member. The saving is small and the stiffness loss is not.

03What happens to dust in an open slot?

It fills, it compacts, and then it holds water. A 10.2 mm groove with an 8 mm mouth will take a remarkable amount of fine dust in a single shift, and once compacted it does not drain. The result is a slot that no longer accepts a nut, and a pocket of moisture against the anodic film for the life of the frame.

Three practical responses, in order of cost. Orient the slots downward or sideways so dust falls out rather than in. Fit slot covers, which are cheap and removable. Or use the slot only where a fixing is needed and leave the rest covered, rather than treating the whole length as available.

04Why design the frame to deform rather than to resist?

Because the alternative is repairing it in place, and underground repair is the most expensive maintenance there is. A guard that dents and can be unbolted and replaced in twenty minutes costs far less over a mine’s life than a guard that resists the impact and transfers the load into the machine structure.

This is the argument for bolted extrusion over welded steel in this application, and it is a maintenance argument rather than a strength one. The bolted frame is a set of replaceable members; the welded frame is one object that has to be cut and re-welded.

05Is aluminium actually a problem underground?

The common claim is that aluminium sparks when struck, and that is mostly a myth in the form people repeat it: the sparking in the well-known demonstrations comes from a thermite reaction with rust particles, not from aluminium against steel alone. But the myth has produced real rules, and in coal mining some operations restrict aluminium components in defined zones for impact and friction ignition reasons.

So the honest position is not “aluminium is safe” or “aluminium is banned”. It is: check the mine’s own standard before specifying. For hard rock gold and platinum operations the concern is usually abrasion and corrosion rather than ignition, and aluminium guards are common. For coal, ask first.

06What five numbers should be on the enquiry?

For a mining application the environment is part of the specification, so the numbers include where the frame goes.

Mine type and zone

coal or hard rock, and whether the zone restricts aluminium

Fixed or moving

which decides whether the thin wall is worth having

Impact exposure

what hits it and how often, because it sets the replacement strategy

Washdown and chemistry

what the frame is cleaned with, because hypochlorite changes the finish

Span and load

the structural check, which still has to be done

Section

40 x 40 mm at 1.30 to 2.35 kg/m, or 40 x 80 at 3.60 kg/m for loaded guards

Related sections and categories

The 40 x 40 is listed under 40 Series Aluminium Profiles, and the heavier 40 x 80 mm section at 3.60 kg/m is the step up for a loaded guard. The full range is compared on the 40 mm profile range page.