Self-belay: introduction

Petzl does not recommend using only one ascender for self-belaying.

Using a single ascender is technically feasible, however, accidents have been reported despite user expertise.
The risks are real in the field, so Petzl recommends using a system with a secondary belay.

In effect:

• You are moving alone over dangerous terrain
• Mishandling is always possible
• Ascenders are not specifically designed for self-belayed climbing
• It must be understood that all systems are flawed, because this means there is a risk, however minor.

Introduction to the principle of redundancy of the belay

Considering the possible malfunction of a single belay system, the usage of a secondary system is strongly recommended.
The secondary system is "redundant", it is installed as a backup to the first system.
The redundancy of the belay should not be understood as a supplementary constraint, but as a necessary precaution.

Major characteristics of a secondary belay system:

• No interference with the working of the primary system.
  Example: contact between the two devices while climbing must be impossible.
• Continuous belay
  Example: a lanyard for occasionally resting on a point of protection is not a continuous belay system.

Recommended characteristics:

• The primary and secondary systems should be different, to limit the risk of repeating the same error.
  Example: if the primary system is a MINI TRAXION, the secondary system should be another device.
• No increase in complexity of installation or functionality, ease of use at least equal to primary system.
  Example: if the primary system slides along the rope without the need for manual intervention, the secondary system cannot require manually pulling slack through the device.

Solutions following the principle of redundancy:

Diverse solutions have been proposed by climbers practicing self-belaying.
Redundancy in belay systems is generally arrived at by consensus of regular practitioners, by making knots in the rope, or by using a second ascender to "double-up" the primary ascender.
The user is responsible for his or her choice among the many possible belay systems. To guide this choice, it is necessary to envision not only standard falls, but also falls made worse by a malfunction of the primary belay system.

Solution with a single ascender on only one rope

Results of a test series done by Petzl:

Test scenario: simulation of primary device malfunction. Cam intentionally deactivated for the test Fall onto the knot with an 80 kg dummy attached to the ascender.
The start of the fall is fixed at 2 m from the anchor, so an "average" position: closer to the anchor, the fall factor will be higher and the impact more severe.

Two fall heights were envisioned:

• "Standard" fall height = 2 m fall above the knot (factor 0.5).
• Fall height of a climber required to climb through a sustained section = 5 m fall above the knot (factor 0.71).

The same falls were repeated on 11 mm diameter dynamic, semi-static, and static ropes.

During these tests, the knot stopped the fall each time.
However, stopping the fall is not a "sufficient" result to validate these tests, because the climber is then faced with other problems.

- The impact force is high: always greater than 4 kN, and up to more than 8 kN for falls on static and semi-static ropes.

 

- The rope is sometimes damaged (sheath torn, several core strands broken): when the cam re-engages during the fall, or when impacting the knot.

 

- The device is damaged by the impact in most cases:
> MINI TRAXION: bent side plates and axle. The device is no longer usable, the climber must use another ascender, or descender, to escape.
> MICRO TRAXION: bent moving side plate and axle. The device might be usable for the escape, but must be retired immediately afterward.
> ASCENSION: bent frame in the most severe cases. The device might be usable for the escape, but must be retired immediately afterward. The knot jams between the carabiner and the body of the device. In case of a poor attachment, the rope will come free.

 

 Petzl does not recommend this solution as its effectiveness is uncertain.

Solution with a single ascender on two ropes

Solution with two ascenders on two ropes

Solution with two ascenders on one rope

Example of premature wear on a fixed rope