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Petzl ZigZag: how the game changed in 14-days

Richard Tregoweth - Sunday, April 21, 2013

Back in December 2012 Treetools offered 5 reasons why the Petzl ZigZag might change the rules of the game - see previous post here.

Treetools had one caveat for the success of the ZigZag; the apparent lack of extensive field trials. The question was posed: would the Petzl ZigZag stand up to the rigor of treework?

Well… the future may have looked promising back in December 2012 but the ZigZag field tests conducted by aerial arborists around the world since mid-February 2013 have shown the rigors of treework might be too much for it.

For all that, the ZigZag has certainly changed the rules of the game.

And much of the change is confined to the last 14-days.

So, for posterity sake, here is how things unfolded… in as many steps!

14) ISA endorses the Petzl ZigZag for use in the ITCC

Treetools cannot find an internet reference to this statement apart from the torrent of comments on Facebook and in tree climbing forums but we believe it to be true. Indignant tree climbers around the world felt the decision represented a double standard which led to Step 13.

CORRECTION: due to a lack of information regarding test procedures, the Petzl ZigZag was NOT cleared by the Technical Advisory Committee for use in the ITCC. Discussions were still underway with Petzl US when the initial accident reports surfaced. Move directly to Step 13.

13) Treetools Blog highlights lack of certification for Petzl ZigZag

The 'Certification Confusion for Petzl ZigZag' blog post was not a dig at Petzl per se.

All Treetools did was 'read the label' and then explain our conclusion.

At that time, Petzl ZigZag documentation made no reference to the 15kN figure mentioned in Step 6.

Treetools had in our possession a series of FAQ, noted verbally by a Petzl representative at the TCI launch of the ZigZag, where 15kN is listed along with other performance data, apparently based on the descender standard EN 12841.

As it happens the 'Certification' post seemed to touch a raw nerve internationally - Treetools phone ran red hot for two full days! These phone conversations might have led to Step 12.

12) NATCC precludes Petzl ZigZag from competition

Due to uncertainty surrounding the certification of the Petzl ZigZag the NATCC decided to withdraw the use of the Petzl ZigZag from their upcoming Tree Climbing Competition.

Talk about timing! The very next day Step 11 occurred.

11) German tree climber plummets to the ground using a ZigZag

Here was the power of social media in action.

The original post was in German yet news spread very quickly around the world. First thoughts went to the climber but when it appeared he was not seriously injured attention soon turned to the Petzl ZigZag.

10) Petzl issue first 'Caution' statement

Petzl moved quickly to acknowledge the incident and Petzl dealers internationally worked in unison to relay the 'no comment at this time' message across the internet. But… a lack of information can only lead to one thing!

9) FB and forums go wild with speculation

Without having anything much to go on, Facebook users and members of the international tree climbing forums worked themselves up into a frenzy.

Climbers familiar with the ZigZag felt there was more to the story. The top 'gold' attachment point would not simply break without reason.

Rational people took a deep breath, and adopted a wait-and-see approach until more information was forthcoming - see blog post here.

8) Petzl ZigZag accident photographs emerge

Just as the first report was a German translation, the source of the first photographs were equally obscure.

Was this the actual broken ZigZag? Or was the image something off a test bed? All the equipment in the photographs was brand-spanking new and somehow the pictures looked too contrived.

7) Questions raised about potential connector cross-loading

Now that photographs were available (whether the real ones or not) experienced climbers began to ask questions; had the device been seriously cross-loaded and in what circumstance did this come about? Was the ZigZag prone to cross-load?

And questions about the break strength re-surfaced.

6) Petzl announce 'Continue to Use' notice for ZigZag

In follow-up to the first announcement Petzl issue another statement giving more detail about the incident. The second notice includes some of their preliminary conclusions. Without saying as much, the accident could easily have been put down to user error.

At this point the Petzl ZigZag could still be used as long as climbers followed the recommendations in the ZigZag Technical Notice.

Under the heading Technical Reminders, the second notice mentions the 15kN strength test (officially for the first time as far as Treetools is aware).

5) 15kN break strength for Petzl ZigZag

No universal or harmonized standard exists for the testing of devices like the ZigZag. Petzl's test followed a philosophy of parts of the descender standard EN12841 hence the 15kN (static load applied for 3-minutes to a classic DbRT configuration with a stopper knot behind the pulley sheave).

As a point of reference the CE Climb system by the Treemagineers is designed to hold 23kN for 3-minutes. The CE Climb load is considered the benchmark for friction-hitch-style climbing systems.

It has to be said; the 15kN figure raised a few eyebrows. See tree climber PPE testing standard post here .

4) Steven Ibelings conducts drop and side-loading tests

Steven Ibelings and a team of guys drop-tested the Petzl ZigZag using the much maligned 'drop-the-100kg-log' method (yes… much maligned and simplistic …but it works).

Steven's test video were not published initially but Treetools managed a sneak preview. The DbRT drop test appeared not to break the ZigZag but the cross-loaded, side-loaded tests produced alarming results.

3) Treetools conducts static pull-test on ZigZag

Having observed the drop-test data Treetools decided to reproduce the static pull tests first noted in the Petzl ZigZag FAQ's and later repeated in the second notice.

Among other tests, two included a 3-minute hold at 4kN to ascertain device slippage and a 15kN hold for 3-minutes with the stopper knot behind the pulley sheave. The ZigZag passed both static load tests without an issue.

Treetools then completed a pull-to-destruction test; at 15.6kN the lower rivet containing the swivel shore off releasing the swivel - the test results and resulting photographs were posted on Treetools FB page.

2) Steven Ibelings releases drop-test videos

The video footage noted in Step 4 is released on the internet. Cross-loading of the top 'gold' eye reproduces the break to the ZigZag as seen in the Step 8 photographs.

Houston! We have a problem!

1) Petzl release a Stop Use Notice for ZigZag

As of the 19 April Petzl announced a 'Stop Use' notice for the Petzl ZigZag. The notice outlines clearly the serious consequences of cross-loading the carabiner on top 'gold' eye with breaks as low as 2kN.

Treetools is uncertain as to what will happen next in this saga - it's now a case of 'watch this space!' but these 14-steps, over as many days, pretty much outline how things evolved.

All credit should go to Petzl for moving so quickly. A product issue like this is bad enough - without it all being played out so publicly via social media - but that is the world we now live in.

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