Anti-reverse pulleys were developed for crevasse rescue, pulley blocks and self-rescue. Every now and then you can see experienced alpinists belaying with the Micro Traxion. But how dangerous is this application?
An article by Max Berger and Robert Kniewasser - first published in the journal mountaineering
After seeing that some people are already using the Micro traxion We have carried out tests in this regard and found that this application is possible if certain criteria are met.
Basically, the Micro Traxion is a backstop reel and not a belay device. The product is certified as a rope clamp according to EN567 for kernmantle ropes from 8 to 11 millimeters.
"The main danger when using the Micro Traxion for belaying is overloading the rope sheath and possible tearing of the sheath, which could result in the second climber falling."
Basically, products are to be used according to the instructions for use. The instructions for use expressly do not recommend belaying people. The product was developed and certified for the following applications:
- towing loads
- pulley systems
- Climbing the rope
The following knowledge of this technique is a prerequisite for using it safely
The Micro Traxion is fixed to the stand so that it can move freely. Pulling in the rope tightly must be possible at all times. A slack rope formation must never occur. Climbing over the Micro Traxion must be ruled out. The belayer must always hold the rope in his hand. If the second climber notices that the rope is not pulled in tightly, he must stop immediately.
«Caution: belaying in snow and ice at temperatures below freezing is dangerous, as under certain conditions the clamp can ice up. This application is therefore to be avoided!»
Certain situations are particularly difficult to handle with the Micro Traxion and increase the risk. The belayer must have rope skills to control these situations:
- Fall and free hanging of the second climber: It is not possible to lower the second climber alone using the Micro Traxion! In this case, the belayer should consider pulling the climber up to help them complete this passage.
- Traverse at the end of a pitch: This can lead to a pendulum fall and thus to a higher load on the system.
- Rope maneuvers at the belay. Attention: The second climber must not climb over the Micro Traxion!
Tests performed to better understand the risks of this technique
The fall tests were carried out with a flexible (comparable to the behavior of the human body) dummy.
Attention: The results of these tests are to be understood as guidelines only; various factors could cause results to deteriorate. Falls should generally be avoided.
Note: During these tests, there was only one complete rope break on a badly worn rope (result marked in red). The results marked in orange represent a tear in the rope sheath and one or more core strands severed, which in itself represents a particularly dangerous situation for the climber.
Comparison of results using a worn rope
Attention: The behavior of worn ropes (degree of wear, type of wear) is not repeatable. The results are given as a guide (the tests were carried out on a heavily worn rope at the end of its life).
It's important to know that when belaying with the Micro Traxion, a worn rope requires even more vigilance than a new rope.
Tests in a pendulum fall
In the case of a traverse at the end of the rope length, the risk of pendulum movement cannot be ruled out. The tests were conducted in a realistic scenario involving a fall down a two meter rope. The climber is 1,80 m away from the fixed point at the same height. The tests were carried out exclusively with a new rope.
The conclusion
In summary, this means that if the Micro Traxion (reverse lock activated) is subjected to a load of more than 4 kN, the cover of a dynamic mountaineering rope will tear and individual core threads can also be damaged.
Only a permanent tightening of the rope can prevent you from not reaching the load limits of the materials. If this rule is followed and the rope used is still in good condition, experienced users can use the Petzl Micro Traxion for belaying.
About the authors
Max Berger is well known to bergundsteig readers. The mountain and ski guide and all-round alpinist runs Petzl Austria.
Robert Kniewasser is a mountain and ski guide and works for Petzl Austria.
About the magazine bergundstieg
Bergundstieg is an international magazine for safety and risk in mountain sports and illuminates the topics of equipment, mountain rescue, rope technology, accident and avalanche knowledge. Bergundstieg is published by the Alpine Associations of Austria (PES), Germany (DAV), South Tyrol (AVS) and Switzerland (Customer Service).
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Credits: Title picture and images/graphics in the text bergundsteig.com