Monday, 22 October 2012

Hardware part 1

First of all, is it karabiner or carabiner, after a day on the ropes and over a few beers this one can go on forever! I have over the years read, heard and discussed every argument, statement and fact. The vast majority will call this piece of bent metal a carabiner, for me it’s a karabiner. The bottom line is that what ever you call it, the thing must be appropriate for your task without compromising safety.

Aluminium or steel, which is best? That depends on your application. If you were an Alpine climber, racked out with lots of kit, including 30+ karabiners, then you would appreciate the weight involved and opt without question for aluminium. For rescue and industrial applications you will find yourself on the other side of the fence, steel being your principal choice. Just to confuse the whole issue, climber or rescuer you will have use for both.

Most aluminium karabiners are forged into their desired shape, then heat treated to arrange the molecules like the grain in hard wood. It’s in these aluminium karabiners that we see the most variation in shape, being designed primarily for the sports climbing market (ref:pic 1).

Pic 1

I read a hefty article about the metallurgy of aluminium karabiners, and the one thing that I clearly remember is that the material, when being forged, takes on a crystalline structure, immensely strong but it can be brittle. So what happens if one is dropped from a height onto a hard surface? Aluminium karabiners do not “witness damage” very well, in other words it will look fine, until it is shock loaded whereupon it may fracture and fail with disastrous results. To get round this problem, if you drop it, bin it! A steel karabiner, if dropped, will invariably be visibly marked and thus will “witness damage”, also steel karabiners will distort out of shape if over loaded. So don’t panic, failure of karabiners is virtually unheard of, it’s the failure of the user, that is the point to watch out for!

Regardless of construction material, all karabiners used in rescue should have a breaking strain of at least 28kN for aluminium
(ref:pic 2)

Pic 2

and 42kN for steel (ref:pic 3), in addition they should all have spring loaded gates with screw locks. I am never comfortable with twist lock gates, however for industrial users or occasional users I do recommend them. Some manufacturers offer a twist lock with an independent lock system, push button or pull and twist options. (ref:pic 4) these are excellent.

Pic 3

Pic 4


For the vast amount of applications my own preference is a large steel screw gate karabiner that is rated at 42kN, made by DMM in North Wales. UK. (ref pic 5)

Pic 5

Corrosion will always be worth looking out for (ref:pic 6). Steel (Iron and Carbon) used in the manufacture of Karabiners is an alloy that may include Sulphur, Manganese and Phosphorous. Karabiners are then plated with a process that puts several layers on the surface. As the top layer is worn away by abrasion or friction the remaining layers will keep corrosion under control. Aluminium karabiners are made from an alloy containing Aluminium, Magnesium and Silica that has good corrosion resisting properties and most are also anodised. Corrosion, either rust on steel components or oxides from aluminium, (we have all rubbed down wood with aluminium oxide paper) will not do our lines or webbing kit any good if it is allowed to build up. Surprisingly the one item left off most kit lists is a washing machine or at least access to one for our ropes and slings etc.

Pic 6
I had an interesting conversation with a representative of the Health and Safety Executive on the for’s and against’s regarding karabiners and was intrigued to hear that the HSE would prefer the use of Maillon Rapides in most applications as they have an unparallelled safety record. I tried it and liked it, used as the item of choice by many Police tactical teams; Maillons will be used without exception when rigging. They now form part of my standard kit and I have found myself recommending them more and more. Delta Maillon (triangle shape) or Pear shaped (ref: pic 7) in 10mm stainless steel, they are certificated as PPE and have an EN reference number.

Pic 7.
Being able to take a load on three axes against only two for a karabiner, they are perfect for use when rigging or establishing anchor points (ref: pic 8). Secured finger tight or nipped up with a 13mm spanner or a multi tool, they have a 100% safety record.

When used appropriately they will be superior to a Karabiner, but I must add never replace them, both Karabiners and Maillons will be found in my kit.


Pic 8.
We clean harness, lines, and tapes but often disregard Karabiners assuming they can look after themselves. Hinges and springs become clogged with dirt and threads on screw gates become stiff with dirt. A good scrub in warm soapy water, a toothbrush to clean threads and hinges comes in handy. The most positive part is handling and taking a close look at this often-neglected item. I once witnessed Karabiners being lubricated with WD40! Shock and horror, the oil will accumulate more dirt while the solvent base will contaminate lines and tapes slowly destroying their molecular structure! A good Karabiner that is clean and dry will need nothing or at most a touch of Silicon spray on the hinge and thread.

The bottom line is; if you are in any doubt about the integrity of your Karabiners be they Steel or Aluminium then retire them, they are a cheap item, but crucial to any line rescue system.

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