Incident Report

2006-01-04Both of the divers usual demand valves were away being serviced so an elderly and previously little-used (by this diver) Cyklon 300 was pressed into service for a short (20m) sump dive in the company of others. On entering the water immediately prior to diving the diver noticed a ring of metal wire some 55mm in diameter lying on the floor. Puzzled as to why it was not previously trampled into the sump pool bed by the previous divers and not recognising its significance the diver placed the ring to one side and dived. The diver dekitted on the other side of the sump and carried out work. Some time later the diver was the last to return but on carrying out a test breath before committing to the sump the diaphragm shield and diaphragm fell onto the sump entrance pool floor. A diver returning to retrieve other kit found the offending items and a return was made by manually holding the diaphragm in place. The found ring was later shown to be the retention circlip for the diaphragm cover. It is considered that adhesion due to age had kept the diaphragm in place for the inward dive but exposure to water and breathing loads had loosened this grip.1. A piece of equipment failed above water but this was not managed to make the situation safe. 2. Know your equipment. An unidentified item might be someones lifesaver or more pertinently your own. 3. Be obsessive about finding out where an item that you dont know has come from. 4. A single 3 litre cylinder was used because that was what was to hand and it was easy to carry in the cave. In the light of other incidents which have occurred that was silly: during the return the diver contemplated just how long a 20m sump would be had the valve failure occurred in mid-sump with no backup. 5. Refitting the circlip did not inspire the diver with confidence that it would remain in place on its next outing and the valve has returned to the bottom of the kit box. 6. Given that this sump can be bypassed via a readily-accessibly passage the sanity of electing to dive using a dodgy valve rather than walking has to be questioned. 7. On the good side the practice of testing and checking all equipment on entering but before committing to the sump proved to be a useful one and is recommended in all circumstances.