Incident Report

1906-03-06The diver was some 40m into the rising of Gods Bridge in an extremely low passage when his demand valve (a Manta ST5000) failed to deliver gas. The diver checked the cylinder tap and manometer and tried the purge button but no gas was forthcoming. Considerable difficulty was experienced in changing to his reserve set because the lowness of the passage made it impossible to turn his head. The diver was therefore force to squeeze forward (off the line) to a slightly bigger area where the changeover was successfully accomplished. A somewhat shaken diver managed to reverse the squeeze rejoin the line and make his way out.1) The valve failed because the housing had become unscrewed from the valve body. This lead to the actuation lever moving out of range of the diaphragm. The underlying reason was poor service - the diver had conducted a routine service on the demand valve the day before and presumably didnt screw the components up tightly enough. Stick to a fixed service routine and double check! 2) where possible dont use newly serviced equipment on a challenging dive. Test it in open water or in easy territory first. 3)In very constricted territory think carefuly about whether you can actually physically change regulator. A factor which made the situation worse was a bulky helmet with several quite large torches fitted. Smaller torches possibly arm mounted would have been more suitable equipment.