Accidents and Incidents
The Medical Advisor to British Cave Rescue Council (BCRC) makes reference in his report for 1995 to ". . . a steady two or three falls per year when cavers (all novices) using a Petzl Stop descender have panicked, squeezed the handle vigorously and then plummeted. We have had no fatalities yet but a fair number of fractures". A few years ago a novice halted part-way down a pitch, moved about, accidentally knocking in the handle of the Petzl Stop, and dropped several metres before the Stop held again - sustaining compressed vertebrae. Petzl literature advises specifically "The lever is for on/off safety controls. When abseiling the speed of descent must be controlled by holding the free end of the rope below the descender".
An incident has recently been reported to NCA Equipment Committee in which a rack became detached from the karabiner linking it to the harness - the caver fell the last 20ft. of the 3rd. pitch in Knotlow, leaving the rack still hanging on the rope 20ft. up. Luckily there were no injuries other than shock and severe embarrassment and there was apparently no damage or distortion to either rack or karabiner. (In this case the karabiner was checked before descending the 1st. pitch and the rack was left attached whilst moving between the pitches, short distances involving some stooping and scrambling, but was not checked before descending the 2nd. or 3rd. pitches.) In 1982 a novice at SRT attempted to descend the main shaft of Gaping Gill - unsure how to deal with the weight of rope preventing him moving, he took out the 3rd. bar of the rack and effectively "free fell" to his death. (Following this most racks now have a device which prevents the 3rd. bar being taken out.)
In addition to the accidents and incidents noted above, there are many other "near misses" which are not recorded, either because there was no injury sustained, or because the caver concerned effected a self-rescue It is important that these "near misses" are reported to the Equipment Committee as the knowledge obtained enables modifications to equipment and techniques which may prevent accidents in the future.
Training and Safeguarding
Both Petzl Stops and racks are devices which need some training in their use if they are to be used safely and to the best of their capabilities. You need to practice on the surface, where you can see what's happening and can get down safely if it all goes pear-shaped! The "training" may be from Fred, your mate in the club, who's been doing it for years and he'll show you how . . . But does he really know what he's doing, or has he been using unsafe practices for years and just been lucky to get away with it? If you rely on a club-mate to show you how, be sure that he has sufficient experience to under stand not only how the device works, but also what can go wrong if it is accidentally misused. Alternatively you could decide your life is worth a little money and attend one of the SRT beginners' workshops now widely available. Your Regional Council Training Officer will be pleased to help and can offer advice on suitable courses or clubs can arrange their own with a grant from NCA.
Safeguarding an abseiler underground is not always easy. Top-roping is seldom practicable due to constrictions at the pitch head and in any case, is really only feasible for short and simple pitches with no obstructions or re-belays. Using a shunt is really for the expert and hence isn't the answer for a novice caver. The safest system is a "bottom belay" - a caver standing at the foot of the pitch ready to pull the rope tight if the abseiler starts to descend too fast. However the belayer is in a vulnerable position at the foot of the pitch and, again, it only works on a single pitch with no rebelays. It is a technique worth knowing but it needs some practice on the surface to be sure you can use it effectively.
Harness Attachments
The most common approach to SRT is for a caver to "kit up" and keep the harness on whilst caving, detaching only descender and foot-loops whilst travelling between pitches; the harness can then be taken off for crawls or if there are no more pitches to negotiate. There are only two devices which can be used to attach descenders safely: maillon or screw-gate karabiner. Which you prefer is a personal choice but there are some points to be aware of:
Your Choice?
Maillon ?
it should be minimum diameter 10mm Probably the most suitable is an alloy 10mm long-series oval.
Karabiner ?
screw-gate "D". Make sure the gate opening is pointing downwards so that, if the sleeve is loosened, it will tend to screw itself shut.
Whichever you use, if you leave the descender attached to your harness, always check the security of your system before you descend a pitch.
References:
1. "SRT" by Dave Elliot, published by Troll, 1986.
2. The current Petzl catalogue (Contact Lyon Equipment, Dent, Sedbergh, Cumbria, LAIO 5QL.) Includes detailed diagrams and advice on use of their equipment. Every item of Petzl equipment sold has an accompanying safety leaflet.
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