MYTH: "Carabiners are susceptible to hair-line fractures if they are dropped. These fractures cannot be seen by the naked eye, but can drastically weaken a carabiner. So NEVER DROP YOUR CARABINER. If you do, it is best to discard it immediately and replace it with a new one." (source:
http://www.cbcnsw.org.au/docs/AbseilGuidelines.pdf)
REALITY: This is NOT TRUE of modern carabiners. First, the "grain" of the aluminum runs parallel to the stock, not perpendicular, so undetectable hairline fractures spontaneously causing carabiner failure just isn't true. Steve Nagode, a quality assurance engineer with REI, conducted an experiment in which carabiners were dropped six times from a distance of 10 meters onto a concrete floor. The breaking strength of the carabiners was then determined with a 50-kN load cell. The results: no reduction in strength was observed when comparing the dropped carabiners with carabiners that had not been dropped.
Black Diamond's website says this: "It's best to inspect dropped gear for dings and significant trauma. If only light scratching is visible and gate action is still good, there is a good chance it is fit for usage."
Taken from ..
http://www.geir.com/mythbuster.html
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