Three-way loading of carabiners.
This issue is often presented as black-and-white and is rarely given much consideration. Most users know that manufacturers warn against certain loadings but what does this really mean? Carabiner manufacturers show that is acceptable to clip a “basket sling” however there must be a relationship between the sling angle and the impact this has on the ultimate strength of the carabiner.
There is a relationship between sling angle and carabiner strength. This relationship can be measured, quantified, and translated into simple terms to allow users to de-rate carabiners accordingly.
In November 2014, 34 aluminium carabiners of differing shape were placed in varying configurations on a slow-pull hydraulic test bed and pulled to destruction. The results were recorded and supplemented with three previous straight-pull tests (zero sling angle) using the same equipment.
An improvised galvanised steel rigging plate was used to separate 10mm mallions and provide a fixed sling angle during the pull. Other options for this were considered however stretch in the sling legs would result in a change of angle with applied tension.
Results…. Membership Required… Well worth the investment
An annual RopeLab membership will increase our capacity to explore and will give you:
access to detailed reports on our tests.
the ability to participate in constructive online discussions.
the ability to request new tests and have design input to these and, where possible, participate in these tests.
a 10% discount on workshops hosted by RopeLab and anything else we may sell.
membership of an online community of rope technicians with a real commitment to professional development.
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Purchase an annual RopeLab membership from their store here.
About The Author
Richard Delaney has worked professionally with ropes since 1992 as a multi-pitch rock-climbing instructor, technical rescue instructor and rope access technician. Understanding and teaching the Physics of Rigging is a core passion of Richard’s, one based on his experience, and his prior professional life as a qualified engineer.
© Richard Delaney, RopeLab, 2014