Using a single rope clamp?
A single rope clamp is not trustworthy; it is recommended to use two rope clamps together and/or to use a backup belay system.
- Carefully read the Instructions for Use used in this technical advice before consulting the advice itself. You must have already read and understood the information in the Instructions for Use to be able to understand this supplementary information.
- Mastering these techniques requires specific training. Work with a professional to confirm your ability to perform these techniques safely and independently before attempting them unsupervised.
- We provide examples of techniques related to your activity. There may be others that we do not describe here.
1. A single rope clamp is not trustworthy
Trusting the belay to a single rope clamp in motion on the rope is risky.
There is a risk of the rope clamp coming off the rope:
Accidental opening of the safety catch is possible while ascending.
There is a risk of the rope clamp slipping on the rope:
Excessive mud or ice on the rope, holding the cam open due to poor hand positioning, foreign objects interfering with the cam (branches, pack straps or clothing), worn teeth...
There is risk of disconnecting the rope clamp's lanyard, if the carabiner opens (rubbing).
Breaking strength is not an issue when a single rope clamp is used by one person.
All of the certification tests, and Petzl's internal tests, are done on a single rope clamp.
When a rope clamp is on the rope and loaded, it is nearly impossible to cause it to disengage or slip. It's when the rope clamp is unloaded and/or moving on the rope that there is a risk of slippage or detachment from the rope.
2. Differences between a ventral rope clamp and a rope clamp on a lanyard
Ventral rope clamp
The ventral rope clamp is connected directly to the harness without extension. Its stable position allows for good rope glide.
With a minimum of precautions, the user can ensure that a loop of slack is not created while progressing, thus maintaining a very low potential fall distance.
Rope clamp on a lanyard (or hand rope clamp)
A lanyard offers more freedom of movement to the user, who can mistakenly find themself above the rope clamp, or with a slack lanyard. This creates the potential for a free fall. As with the ventral rope clamp, one must also monitor the tension in the rope between the rope clamp and the anchor. Any loop of slack is dangerous.
The EN 12841 type B standard (rope clamps for work): fall test on a dynamic lanyard, rope clamp on a semi-static rope at 1 m from the anchor. Test using the mass marked on the rope clamp (140 kg for ASCENSION, BASIC, CROLL on compatible rope diameters greater than 10 mm).
EN 567 standard (rope clamps for sport): no fall test.
Petzl's internal tests complement the requirements of the standards by being based on realistic usage scenarios.
These tests help ensure that the rope clamps do not tear the rope under the most unfavorable conditions (fall distance equal to the lanyard length, 1 m from the anchor, 80 kg dummy, ropes of compatible diameters).
3. Different modes of rope clamp use
The user is hanging on a progression rope.
The recommended rope ascent system includes a ventral rope clamp (CROLL) and a rope clamp on a lanyard (BASIC, ASCENSION).
The main risks occur at particular moments, when attaching / removing the rope clamps: start of the ascent, passing a knot, passing an intermediate anchor, arriving at the anchor station.
As a single rope clamp is not trustworthy, it is recommended to use two rope clamps, both attached to the harness.
Progression along a fixed rope
The user has their weight on the feet, using one or more rope clamps for self-belay and as an aid to progression.
The user has their hands free to slide the rope clamps along the safety rope, in order to always keep slack out of it.
If there is a low probability of a fall, using a single rope clamp is possible; the user must always keep slack out of the rope between the rope clamp and the anchor.