Saturday, 30 May 2009

Testing Old Carabiners and Slings

The Strength of Old Climbing Equipment

I am often asked about climbing equipment - what equipment people should buy, should people buy second hand equipment, does minor damage affect equipment etc. This article is taken from my website Rock Climbing Company

DMM recently received an old quickdraw from a customer who wanted to know how strong their old quickdraw would be.

The quickdraw consisted of 2 DMM Lynx carabiners - one plain gate and one bent gate that the customer said were about 20 years old plus a Petzl quickdraw sling that was also difficult to age.

The plain gate carabiner (1) generally seemed to be in reasonable condition with the key exception of the latch end of the gate. The end of the gate had suffered from salt corrosion at some point in its life and now was visibly corroded and the metal was exfoliating slightly,

The second image shows this in more detail - on the Rock Climbing Company page you can roll the mouse over the image for even more detail. This was considered serious damage as this part of the gate holds the rivet that locates into the latch in the nose and is structurally very important.

The bent gate carabiner was in quite good condition with very little visible damage and no visible corrosion.

The sling was slightly faded and had some abrasion damage at the end that held the plain gate carabiner. The fibres around the abrasion were quite fluffy, but there was no obvious cutting of the fibres. Again this is a bad place to have damage because quickdraws virtually always break at the apex where the load is applied

Initially we tensile tested the complete quickdraw using the standard carabiner test.

The first item to break was the sling (2) - this broke at the low figure of 9.23kN. It broke as expected at the apex with the abrasion damage - the 'slight fluffing' has cause a strength decrease of almost 60%.

We then pulled the individual carabiners.

The plain gate with corrosion damage (1) broke as expected at the gate as the rivet pulled free from the corroded gate. This carabiner broke at 12.55kN - when new it was rated 24kN, thus it had been substantially weakened, but was still suprisingly strong considering the extent of the corrosion.

The last carabiner was reassuringly strong and made a massive 27.90kN - cruising past its rating of 24kN more than 20 years after it was first made.

The morale is "visible damage relates to actual weakness - especially with fabric items".

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