summitseeker
04-03-2013, 07:30 AM
Biner Block Failure
I am leaving the details of this event vague to avoid placing blame.
My canyoneering party came upon a group of four in a canyon very recently. We caught up to them at one of the larger rappels after two of their group members had descended and a third had just gone on rappel. The group leader remained at the top. The anchor was an existing piece of webbing, unequalized, and tied to two mini arches. The webbing had a large rap-ring through which the group had threaded a rope with a“biner block”. The block had a pull cord attached with a figure eight follow-through and was setup for a toss. We informed the group leader we could retrieve their rope if it would help them and they agreed. The leader untied the pull cord and stored it in their pack. The rappeller was a novice and taking their time on the rappel. As we were waiting we noticed movement and slippage on the rope. Trying not to pry, we inquired about the chosen anchor set-up and got a closer look. The leader explained that the rap-ring was really big and the biner block was pulling through so they had set an additional carabiner to the block in order to add friction and prevent the biner block from pulling through. The leader’s account did not jive with the known physicsof a biner block and raised some flags in our minds. We looked at the biner block and the knot and found it to be an incorrectly tied clove-hitch in the form of an overhand type hitch. I started to suggest that we backup the setup by clipping in the end of the rope but before we could take a second look, the rope started to slowly slip through the block and the ring. With the pullcord knot removed from the end of the rope, and an improper clove-hitch, the whole system was about to fail with someone still on rappel. I grabbed the rope and my partner quickly clipped the free rope end through his ATC to prevent slippage. The rappeller was on the ground safely shortly after, unaware they almost suffered a different fate.
Analysis:
Inspection of the knot yielded an incorrectly tied clove-hitch. The group must have thought the knot to be correct and attributed the slippage to lack of friction on the ring. This explanation showed a lack of understanding of the block fundamentals. We educated the leader about tying the clovehitch. The leader seemed embarrassed and recognized the error and potential severity.
As canyoneers we must remember that everyone is responsible for safety checks and double checks. If something looks wrong or feels wrong, it should be redone or reevaluated. As outsiders to the group weall agreed that we felt like we were imposing and were afraid to speak up when the initial warning signs arose. However, when it became apparent that we were witnessing a dangerous situation our group effort and quick actions prevented an accident due to a knot failure. All backcountry adventures should feel empowered to lend a hand and assist others. If people are writing their names on the canyon walls, educate them. If kids are too close to an edge, speak up. If an anchor is inches away from catastrophic failure, fix it immediately. We all have a duty to prevent injury to others and the environment.
I am leaving the details of this event vague to avoid placing blame.
My canyoneering party came upon a group of four in a canyon very recently. We caught up to them at one of the larger rappels after two of their group members had descended and a third had just gone on rappel. The group leader remained at the top. The anchor was an existing piece of webbing, unequalized, and tied to two mini arches. The webbing had a large rap-ring through which the group had threaded a rope with a“biner block”. The block had a pull cord attached with a figure eight follow-through and was setup for a toss. We informed the group leader we could retrieve their rope if it would help them and they agreed. The leader untied the pull cord and stored it in their pack. The rappeller was a novice and taking their time on the rappel. As we were waiting we noticed movement and slippage on the rope. Trying not to pry, we inquired about the chosen anchor set-up and got a closer look. The leader explained that the rap-ring was really big and the biner block was pulling through so they had set an additional carabiner to the block in order to add friction and prevent the biner block from pulling through. The leader’s account did not jive with the known physicsof a biner block and raised some flags in our minds. We looked at the biner block and the knot and found it to be an incorrectly tied clove-hitch in the form of an overhand type hitch. I started to suggest that we backup the setup by clipping in the end of the rope but before we could take a second look, the rope started to slowly slip through the block and the ring. With the pullcord knot removed from the end of the rope, and an improper clove-hitch, the whole system was about to fail with someone still on rappel. I grabbed the rope and my partner quickly clipped the free rope end through his ATC to prevent slippage. The rappeller was on the ground safely shortly after, unaware they almost suffered a different fate.
Analysis:
Inspection of the knot yielded an incorrectly tied clove-hitch. The group must have thought the knot to be correct and attributed the slippage to lack of friction on the ring. This explanation showed a lack of understanding of the block fundamentals. We educated the leader about tying the clovehitch. The leader seemed embarrassed and recognized the error and potential severity.
As canyoneers we must remember that everyone is responsible for safety checks and double checks. If something looks wrong or feels wrong, it should be redone or reevaluated. As outsiders to the group weall agreed that we felt like we were imposing and were afraid to speak up when the initial warning signs arose. However, when it became apparent that we were witnessing a dangerous situation our group effort and quick actions prevented an accident due to a knot failure. All backcountry adventures should feel empowered to lend a hand and assist others. If people are writing their names on the canyon walls, educate them. If kids are too close to an edge, speak up. If an anchor is inches away from catastrophic failure, fix it immediately. We all have a duty to prevent injury to others and the environment.