Well they didn't train us this way.
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2airishuman
Contributor
Though it isn't widely taught with single backmounted tanks, because not everyone can reach the valve, it is possible to feather the valve to deal with a freeflow.
For several years I have been teaching students how to reach back to close the valve and then open it. So far, all but one have been able to do it. I knew he would have a problem before the class started because he advised me of his shoulder surgery. The reason the success rate is high is because students learn to do this in a neutral head down position. If they are doing it while sitting on their knees the failure rate jumps way up.
Yes, but if you have a free flow from the first stage it will be at the cylinder pressure.
Even if the free flow starts in the second stage, if normally causes the first stage to fail in pretty short order (icing), especially in cold water.
The other issue is, if it is a first stage failure, the 2nd stage (demand valve), is the emergency pressure release. Most Scuba second stages are downstream valves, which means they vent excess pressure by free flowing. Poseidon are unusual in that most of their valves are upstream (e.g. the Jetstream). They solve this by having a spring mechanism where the intermediate hose meets the second stage, which vents excess pressure at this point.
If you stop the over pressure release working, then the over pressure will cause something else to fail, possibly the inflator, or resulting in a burst hose.
The only sensible solution is to shutdown the cylinder. You may be able to reopen the valve later. I have done this a number of times successfully.
Gareth
I don't use Miflex since they earned a reputation for de-laminating internally, and I've had a hard time, especially with the HP hoses. However, once I kink a hose severely, I trash it. That's from being a mechanic and seeing many brake hoses (even higher PSI) fail after they've been pinched.
I didn't see much of any positive reinforcement in this thread. You might have a different idea of "positive' than I have.
I guess that's a matter of why you are having the free flow.
Doesn't 200 bar exceed the burst pressure of most LP scuba hoses? I can't find the burst pressure for miflex, but my regular rubber hoses are stamped 27 bar. If your first stage wasn't regulating the pressure at all, I don't think it would matter if you could kink the LP hose or not. If you did, it should blow out the hose straight away.
Scuba systems are designed to protect the hose. On a downstream valve, the second stage is designed to open at over pressure, hence stopping the free flow by kinking the hose is attempting to override the protection offered by the 2nd stage.
Having a hose burst due to over pressure is quite dangerous, and a significant risk to the diver.
I can’t help wondering if your buddy’s regulator was even designed for cold water. Sounds like he described it as a known problem at depth, but if used beyond the design limits the problem is more with the user than the gear in my opinion. There are a lot of variables beyond just water temp that contribute to freezing open, and the increased breathing air density at depth is one of them.
Good job on the fast thinking and reaction.
Good job on the fast thinking and reaction.
OP
Hey guys, thanks for all of the replies, I have learned quite a bit already from this thread, and appreciate the feedback. I in no way shape or form felt like people were attacking me or deliberately pointing out what I had did wrong. In fact this board seems to be really good about not attacking the poster, that is the reason I posted it. I knew someone would come along with good advise. Going back through to answer some of your questions: He was diving a AL titian for a 2nd stage, not sure what he had on the 1st stage other that some AL. He didn't freeze the 1st stage, as it was only his primary that was free flowing, his octo was fine. Coms / hand signals were already agreed upon, again I had dived with him on 5 other dives (over the course of a few months). Do I wish things had gone differently, sure. But then again, I look at it as a learning experience and will adapt my setup to better prepared should this happen again.
Stoo
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Apart from being a complete CF, that was my takeaway as well. Why on earth would anyone buy or even use a regulator with that as a "known problem". I mean if Ford starts selling a car and the wheels regularly fall of so it becomes a "known problem", I'm pretty sure nobody would buy one. The liability for the manufacturer would be astronomical.
Just curious, what brand and model was it? In my neighborhood, 47° water isn't cold... "cool" perhaps, but not cold. I'm not aware of any brand of regulator that can't handle that temperature, especially at a moderate depth like this.
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