Using the NAJA friction saver with single rope (SRT/SRS)
The NAJA friction saver was designed for use on doubled rope (DdRT/MRS), but it has also been tested and certified with a specific setup for use on single rope (SRT/SRS).
Warnings
- 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.
The setup certified for SRT is as follows, as specified in the Instructions for Use:
- a figure-eight knot blocked against the pulley, with a carabiner (required) attached to the loop of the knot.
- the knot is on the side opposite the MINO retrieval accessory-carabiner.
Single-rope setup
The double overhand knot has also been tested in this configuration. The results show that it should not be used: it deforms under load and passes through the device at low loads, attainable in use (5 to 10 kN depending on the ropes tested).
The figure-eight knot and the butterfly knot were tested to more than 12 kN without failure. However, as knot behavior under load is not always repeatable, Petzl recommends always attaching a carabiner to the loop of the knot, as a backup.
Certain techniques for access, work and retrieval can be more effective if the knot is blocked against the retrieval link.
WARNING: tests have shown that in this case, the MINO is likely to be damaged in normal use by a single person, without presenting a risk to the user: even when the MINO is damaged the system strength is not affected because the stopper knot is blocked against the frame of the NAJA.
For this usage, Petzl recommends replacing the MINO with a GO 7 mm quick link. Before using any other quick link, verify its compatibility with the retrieval ball.
Example with setup in accordance with the Instructions for Use
- The stopper knot does not interfere with the MINO
- No removal of the rope from the ZIGZAG during setup and retrieval.
- The deviations made during work help brake the friction saver's fall during retrieval.
- During retrieval, the friction saver will follow the same path that was taken during work: there is a risk of jamming in the deviations.
- For retrieval, you must first lower the stopper knot to untie it, install the retrieval ball, then finally retrieve the friction saver.
Setup
Retrieval
Example with the knot pressing on the retrieval link
- Faster retrieval with no need to lower the knot to untie it
- The stopper knot can be attached to the access system (not shown in the drawings) for joint retrieval.
- During retrieval, the friction saver does not pass through the deviations made while working.
- The ZIGZAG must be removed from the rope for the retrieval.
- The retrieval ball is attached to the end of the rope behind the ZIGZAG, by a clove hitch if the end does not have a splice.
Setup
Retrieval
