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At 20:21 26.07.98 +0000, Case E. Harris wrote: >I've also found, however, that when descending on an anchor line (something >rarely found in caves....I think!) the line itself can slip between the right >post valve and the cylinder and roll off the right side as well. Granted, >break off would be nearly impossible in this situation, and anyone smart >enough to dive long hose on the right post would know within a few breaths >that they had been shutoff. > >I guess this is just a bit more support for the practice of CHECKING your >valves ANYTIME they some near something that could roll them off. > >Just my two-bits worth. I'll go back to lurking, reading, and learning >now.... Slightly off-topic... My diving is all open water (ocean or fjord diving) including limited penetration wreck diving. Rolling off the left valve post is an unrealistic concern, I believe, unless you brush against the ceiling of a cave. Wrecks provide plenty of entanglement but rarely long passages with smooth ceilings that may roll a valve off. However, in colder water there's another reason to operate valves underwater. Regs may freeze and free-flow. Your backup may free-flow the moment you jump into the water. However, when a freeze-up presents itself well into the dive it's obviously the reg you're breathing from that freezes. For this reason it's a good idea to start a cold water dive (air or water temp below 40F/4C) using your backup reg. I'll take my short hose (backup) 5 min into the dive and switch to my primary. At that point my primary has thawed up and is ready to go. Usually, freeze-ups start on the surface and progress due to the cooling of depressurization. Still, deep freshwater dives in the summer (think more like Lake Ontario than Ginnie Springs) may initiate freezing at depth. You pump humid summer breeze into your tanks and take it to the frigid depths of a lake. The combination of humidity, ambient low temperature and pressure drop within the regulator may cause a freeze-up. In any event, valve close-down is a useful skill. You'd also want to know which one to close down... For this reason it's paramount to set a standard for yourself and your team. Left post, short hose & right post, long one -- breathe the long one primarily -- is my choice (sounds familiar?). My breathing a little on each reg may seem to contradict this concern, but switching really helps ensure that no particular reg turns into a block of ice. If you stay on the main reg (right post/long hose) most of the time and use the backup for descent only there should be no mix-up. If so, everybody knows intuitively that a free-flow at depth means it's time to close the right valve. Cave divers may roll valves off -- Scandinavians may turn them off on purpose -- in the winter :-) regards, Hans Norway -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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