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

[CuzzA]

You mean plug the second DIN opening?

No, I mean to eliminate the burst disk feature and consequently removing that failure point to prevent a tremendous loss of gas from ever being able to happen. I do not believe there are burst disk/plugs on H valves.

 

[CuzzA]

Here is an interesting concept I have not seen before. Not cheap either at $171.

SAS Valve - Beuchat

 

[tursiops]

No, I mean to eliminate the burst disk feature and consequently removing that failure point to prevent a tremendous loss of gas from ever being able to happen. I do not believe there are burst disk/plugs on H valves.

Yes, all the valves sold in the US have burst disks. No, I would not plug them, not if you want to get your tank filled. A LP hose burst or a second-stage run-away free flow will drain your tank just as fast - faster, probably -- as a burst disk failure, and is more likely.

 

[CuzzA]

Yes, all the valves sold in the US have burst disks. No, I would not plug them, not if you want to get your tank filled. A LP hose burst or a second-stage run-away free flow will drain your tank just as fast - faster, probably -- as a burst disk failure, and is more likely.

True. I suppose the stories I've heard of guys plugging their valves are probably filling their own tanks as well. Of course I doubt a fill operator is checking, but it would be unethical to not tell them.

FWIW, I am just researching the logistical challenges of diving doubles on smaller private boats. A well thought out system for independent doubles probably makes the most sense, setting that Beuchat valve aside, which appears impossible to find.

 

[tursiops]

Here is an interesting concept I have not seen before. Not cheap either at $171.

SAS Valve - Beuchat

View attachment 547999

View attachment 548000

I'm confused now. Is your goal to have two first stages, or to have a valve with no burst disk

 

[PfcAJ]

I know two people who have had burst disks start to leak following contact to the ceiling.

plenty o folks have had valve knobs break off.

I’ve seen bonnet o rings fail (both times on the surface, thankfully).

valve stems stripped so the knobs just spin freely.

An h valve is better than a K valve but still not good enough for overhead diving imo.

Maybe cavern dives I guess?

that said, virtually all of these issues are related to smackin’ the cave ceiling. In OW you don’t have that problem.

 

[CuzzA]

I'm confused now. Is your goal to have two first stages, or to have a valve with no burst disk

I started this conversation here in the tech forum because as I'm sure you know, redundancy is essential. The goal is maintaining redundancy without the disadvantages of doubles. So I am exploring different options and the H valve seems to be the next closest thing. However, the burst disk is a failure point that occurred to me after starting the thread. I'd be curious to hear other types of potential valve failures.

 

[BRT]

Was there a dip tube present? I know some people don't like them as they can unscrew and become a nuisance.

I don't know in either case but I assumed not. One case was a Mexican fisherman and the one I watched was with a dive boat, but the owner and guide was a fisherman too.

 

[CuzzA]

I know two people who have had burst disks start to leak following contact to the ceiling.

plenty o folks have had valve knobs break off.

I’ve seen bonnet o rings fail (both times on the surface, thankfully).

valve stems stripped so the knobs just spin freely.

An h valve is better than a K valve but still not good enough for overhead diving imo.

Maybe cavern dives I guess?

that said, virtually all of these issues are related to smackin’ the cave ceiling. In OW you don’t have that problem.

Thanks for the contribution, AJ. I certainly agree I don't think an H valve is suitable for caves. Would you agree in OW the risk is significantly less in the event of one of those types of failures you mentioned since you can obviously get shallower quicker than you can in a cave and be able to make a gas switch sooner? In other words, where do you put the H valve on your risk tolerance level (setting cave/penetration/big pinnacle dives aside).

 

[CuzzA]

I don't use an H-valve. If for example, you blow a LP hose at the insertion point into the first stage, how do you determine which side to shut off?

With an isolator doubles manifold, I assume you shut that down first?

Hope this is not too far off topic? I am curious what is best practice?

I have heard both schools of thought. Shut down isolator to ensure you retain at least half of your gas, then find the offending post. The other school of thought is you are wasting time shutting down the isolator and instead should shut down the primary first stage port you are breathing as it will be the most likely to have failed. All of this of course is assuming you can't identify which post has failed to begin with. Which I would think would be unlikely since one side would be louder than the other and if a second stage begins free flowing it is obvious which posts has failed.