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"David E. Smith" schrieb: > A partially open valve will act like an open valve. > A partially open valve will be more easily shut (whether intentionally or David, quite right, or ??? I remember a dive( air, singles, no bcs, single reg) 17 years ago like it was yesterday. Group of three + Instructor ( n+1 star). Fast dropdown to 15m to get under a surface current, exchange ok sign, everything ok, dropdown to 33m, exploration, swimming against a bit of current. My buddy signalled something's wrong and pointed to his back. Instructor looked for his valve, handled the knob, at the same moment he made the OOA sign, then spit out the reg, took a gulp of water and tried rocketing upwards. I grabbed him from behind, the other buddy shared his air with him, I prepared for sharing with the donator as well, just in case he would not let go. While we did the ascent, I looked at the reg ,there was no air. Valve was closed ! I opened it , and air was coming. So the Instructor had actually closed it, obviously he had turned it the wrong direction, and it was only open a turn. I did nothing about it so not to disturb the ascent, which went well, a safety diver came in the inflatable, and later we joined them on their safety stop. Of course a partially open manifold does not produce this immediate emergency, because the other tank only acts as a buffer, but I still regard it as bad practice. It may lead to complacency ( not opening fully for mixing) or the flow may be misjudged, the danger of sudden closure left aside. The idle play in a valve leads to a sudden blast of flow when opened, because the flow nils out the idle play of the threads and in the valve operating bearings, so one may think this is enough flow, and not open more. In fact, if demanded a high flow, areas of low pressure may occur and suck the seat closer, throttling the flow. This is a normal effect in pneumatics . Just open your valves, and turn them a tiny bit to protect the upper spindle. If turned ccw then, you will notice immmediately , and turn cc to close at once. Matthias -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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