Examples, Stories, Anecdotes of Tank Valve Failures. (Side Topic H-Valve Single Tank Diving)

[CuzzA]

Do doubles have disadvantages when diving? You must bring 2 cylinders to test, but I don't know any disadvantage while using them.

I have done 18 liter single tank double valve decompression dives without decogas, up to 20 minutes of deco with a max depth of 51m on air, sometimes also solo. Why? I wanted technical diving when I did my open water course, but everybody adviced me to start with sportsdiving equipment. So I started with a 10 liter single tank. As advanced open water diver, I started by doing decompression diving on my own, and I needed a bigger cylinder as everybody said don't start technical diving, you are not experienced enough. (read: I had in 10 months after open water 200 dives and was divemaster). So I have used it.
Failures had? No, nothing, even no frozen regulator (I dive also under ice). BUT: some friends had frozen regulators and with single tank and drysuit you cannot close valves on your own. Also I have seen the O-ring between valve and cylinder popped out and then you cannot do anything to stop it. I also had 2 weeks ago an HP hose bursting on a bailout cylinder. Now no problem, but you won't want it on a single tank and you cannot close valves.
I was really happy when I finally bought my twin12 liter after 200 dives. More stable, more gas, not more heavy, I could do valvedrills. So I increased safety.
And I am still a little bit angry because people 'adviced' me to start with sportsdiving equipment as I could buy all over again after only 10 months. If they had listened to my wishes and motivated me, then I never did the single tank solo decompressiondives as self trained diver (knowledge from books). I would have increased safety by doint it with a twinset, maybe started earlier with the right courses, etc.

Oh: I own that Beuchat double valve. I have it now on a 10 liter tank. Even my recreational sportsdiving regulators are 2 DIN-first stages, longhose, DIR equipment.

My advice: DON'T DO decompression dives with a single tank. And don't plan decompressiondives with only backgas. Use a decogas. It is not only the risk of a freeflow, it is also about handling the valves, stability in the water (twinset is way much more stabile), etc. There is NO CHEAP TECHNICAL DIVING.

Germie, thanks for sharing your stories. It's not about being cheap, it's about being safe. Deep spearfishing, albeit with short bottom times, and lots of gear is a recipe for disaster. Perhaps I should have alluded to why I'm exploring non traditional options, but I didn't want the thread to go off track.

I believe a twin set and a slung deco bottle is certainly the best way to do most decompression dives, setting perhaps CC aside. But you have to imagine trying to manage several sets of doubles on a sub 10 meter boat for over a couple days doing deep dives catching fish in the 50-100lbs. class. This includes managing a gun, stringer, the environment and predators. Lots of bottles, hoses and regs can also be a negative. So that's why I'm trying to explore ways to balance a fair level of streamlining and limited clutter, yet maintain a reasonable amount of safety in a gas loss scenario. Admittedly I am happy to hear deep stops are not what people thought they were, thus a a leaner deco mix expands their utility of deeper gas redundancy.

I recognize this site is mostly comprised of cave divers, so the issues I'm describing may not register from their experience or training, but diving is diving and there's always something to learn as we don't know what we don't know. There are a lot of deep water Florida spearfishermen and from my research over the course of several days it appears many are conducting single tank dives, some with h valves, some without, and tank mounted bailouts and deco bottles. Which certainly has it's own deficiencies, but also has it's advantages given the activity. Keep in mind, most of these dives are around five minute max bottom times and limited to around twenty minutes of deco. Certainly not huge pinnacle dives, but definitely big enough to kill someone if they don't have their shít together. There's a lot of Gulf Coast cowboy style divers, I want to maintain a bit more sophistication than a Jesus take the wheel approach to diving.

Do you want to sell that Beuchat SAS valve?

 

[tursiops]

Germie, thanks for sharing your stories. It's not about being cheap, it's about being safe. Deep spearfishing, albeit with short bottom times, and lots of gear is a recipe for disaster. Perhaps I should have alluded to why I'm exploring non traditional options, but I didn't want the thread to go off track.

I believe a twin set and a slung deco bottle is certainly the best way to do most decompression dives, setting perhaps CC aside. But you have to imagine trying to manage several sets of doubles on a sub 10 meter boat for over a couple days doing deep dives catching fish in the 50-100lbs. class. This includes managing a gun, stringer, the environment and predators. Lots of bottles, hoses and regs can also be a negative. So that's why I'm trying to explore ways to balance a fair level of streamlining and limited clutter, yet maintain a reasonable amount of safety in a gas loss scenario. Admittedly I am happy to hear deep stops are not what people thought they were, thus a a leaner deco mix expands their utility of deeper gas redundancy.

I recognize this site is mostly comprised of cave divers, so the issues I'm describing may not register from their experience or training, but diving is diving and there's always something to learn as we don't know what we don't know. There are a lot of deep water Florida spearfishermen and from my research over the course of several days it appears many are conducting single tank dives, some with h valves, some without, and tank mounted bailouts and deco bottles. Which certainly has it's own deficiencies, but also has it's advantages given the activity. Keep in mind, most of these dives are around five minute max bottom times and limited to around twenty minutes of deco. Certainly not huge pinnacle dives, but definitely big enough to kill someone if they don't have their shít together. There's a lot of Gulf Coast cowboy style divers, I want to maintain a bit more sophistication than a Jesus take the wheel approach to diving.

Do you want to sell that Beuchat SAS valve?

As suggested earlier, a set of small steel doubles and a slung deco bottle is your best bet. Proved system, true redundancy. I see no significant value added by an H or Y valve on a single. That adds only a redundant first stage, which is not your major concern. Once you've taken care of the back-gas redundancy, your next major problem is gas/deco/profile planning.

 

[johndiver999]

For the spearfishing deco dives, perhaps it makes sense to carry three (independent) bottles. Since the deco is relatively short, would it make sense to carry a deco mix of 50 or 60 % that you could presumably get on at 75 ft or so (while ascending). If your deco mix was lean, you would not need a lot of gas to ascend from the bottom to the deco mix range.

Would a 13 cu-ft bottle of air work for an ascent bottle and a 30 work for a deco bottle? Maybe a 40 if you filling it off a larger deco bottle and will not have it filled for each dive. That would be smaller than doubles and a stage bottle. I assume you would want to "arrive alive" if you were to completely lose any single bottle?

If you can manage to spearfish with one slung bottle, the configuration is not so different than a more typical recreational set up. A 13 or 19 bottle of air tucked under your arm may not be so terrible to deal with, but it might take a little practice to carry it and load the gun.

That would mean you would basically have enough gas in the two bottles to do deco with no deco mix bottle, or handle the situation where you lose the main tank completely.

I can completely understand why you want to avoid using doubles - if possible.

Also, you would have to be doing some pretty quick repetitive dives to do a 5 min bottom time and get a 20 minute deco, what depths are you considering?

 

[kensuf]

OK, I have a better idea of what you're trying to do.

I did a fair amount of deep ocean diving (150-180') with a steel 95 that had an H-valve and a 40 of 50%. Yeah, there's a risk of a burst disk problem or neck o-ring, but I still feel the rig served its purpose well.

I still think a set of double 80s would be better, but hunting is a different beast.