i know some people back up their harness belay loops, i was cruising the BD website and came across an article by their QC man, unfortunately they use pounds (3372 pounds is 15kn, the CE requirement for belay loops):Some Unofficial, Incomplete, One-Data Point, For-Curiosity-Only Experiments
To satisfy my own curiosity I decided to test several belay loops with different levels of wear: cut approx 50% through, cut up to 80% through, cut close to 90% through, two tacks cut, all tacks heavily abraded on a file surface, structural web heavily abraded on a file surface, etc. By no means are these experiments complete or conclusive as there are many variables that were not, but could be looked at like: belay loop construction (2 tacks vs. 4 tacks, protective non-structural layer over top of the tacks), material used (nylon vs. polyester), UV degradation, environmental, wear, etc, etc. Basically, the results were what I was expecting. Belay loops are burly—really burly. To have one fail at body weight loads, or even small shock loads which could happen during rappelling is possible, but the belay loop would have to be SO worn through that it seems very unlikely.
Below are some photos of the different belay loops I tested (before they were pulled to failure) and their tested values.
50% cut through—one side —3480 lbf:
~75% cut through—both sides (not the best photo)—2918 lbf:
~ 90% cut through—one side—777 lbf:
2 of 4 tacks cut—3970 lbf:
All tacks heavily abraded across file surface—5280 lbf:
Structural webbing heavily abraded across file surface—4805 lbf:
All tacks heavily abraded across file surface—5338 lbf:
All tacks heavily abraded across file surface—7429 lbf:
A Final Word
Is this incident going to cause every climber out there to start wanting two belay loops, or tying a backup webbing belay loop in their current harness or throw their harness away altogether and buy a new one immediately? It shouldn't. Reputable manufacturer's make burly harnesses—bottom line—and don’t forget that there are some negatives/concerns about using two belay loops at once in some situations (i.e. tri-axial loading carabiners, etc.)—not good.
Harnesses, and belay loops in particular are super strong for sure, but we can't forget that gear does wear out. Every climber is responsible to know the history of his or her gear and act accordingly. When people ask me about worn gear, or gear that's been dropped, or has undergone a strange or peculiar event, I always have to play the conservative card of "when in doubt, retire it"—because the last thing you want to be thinking of in the back of your mind when you're 20 feet above your last piece of sketchy gear is... "geez, I wonder if that's that biner that I dropped that time," or "I sure hope my harness is in good enough shape to withstand this monster whipper I'm about to take." It's not worth having to worry about—I personally have a hard enough time worrying about trying NOT to fall…
Kolin Powick (KP) is a Mechanical Engineer hailing from Calgary, Canada. He has nearly 20 years of experience in the engineering field and has been Black Diamond's Director of Global Quality since 2002. Kolin oversees the testing of all of Black Diamond's gear from the prototype phase through continual final production random sample testing
the full article can be found at http://www.blackdiamondequipment.com/en ... elay-loops