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

[CuzzA]

Well that rig looks to require 4 independent regulators - all back mounted. I guess your idea would be to drop the H-valve aspect?

I don't know. Just trying to explore options and the risk that comes with them. I was able to nail down my rec rig by having a good open conversation here. Hoping to do the same here with a tech rig.

 

[tursiops]

You are beginning to be over-constrained.
You want redundancy, low risk, small size, nothing on your sides, maybe something slung, no manifolded doubles, small boat....

Maybe you need to decide what is on your must-have list and what is just nice-to-have.
And what sort of dive profiles are you contemplating.
And whether you REALLY want to do deco.

 

[GG1]

Looks like two DIN tank valves on the steel tank. Is that how we get to four independent 2nd stages? Appears to be an Al 40 on the left, and an Al 30 on the right (with the 1st stage outboard). Seems it could be additionally streamlined. Would this work with a singles wing?

 

[CuzzA]

Looks like two DIN tank valves on the steel tank. Is that how we get to four independent 2nd stages? Appears to be an Al 40 on the left, and an Al 30 on the right (with the 1st stage outboard). Seems it could be additionally streamlined. Would this work with a singles wing?

Yeah, a right side handle valve would make more sense on the right side tank to protect and streamline the first stage. As long as the wing has the lift and you can swim the rig up I don't see why not as you can move the tank mounts toward the back to give the wing the room for expansion.

 

[kensuf]

Modern manifold failures are rare, if they even happen at all. Twice I've seen sets of doubles fall off a bench at Ginnie and land manifold side down. Both manifolds were fine and held gas. I've heard stories of doubles falling out of the back of a truck on the highway. Again, no problems.

OTOH, the older Sherwood Selpac manifolds that were held together by a compression nipple instead of barrel o-rings, did have problems. However that design hasn't been made since the 1980s (and it was yoke only). I tend to believe that the "manifold failure myth" is based on those Selpac manifolds.

 

[PfcAJ]

Modern manifold failures are rare, if they even happen at all. Twice I've seen sets of doubles fall off a bench at Ginnie and land manifold side down. Both manifolds were fine and held gas. I've heard stories of doubles falling out of the back of a truck on the highway. Again, no problems.

That was me! #legend

 

[Doby45]

With the size of that setup, just go with doubled LP50s.If you can get a shop to fill them to just 3K that is 120cuft of gas, redundancy, small package. Ticks pretty much all the "needs". And if by chance you can get them filled to 3600 then you have almost 150cuft of gas, in some tiny doubles that you could easily spearfish in.

Right, no drysuit or scooter.

I think you make a good point about identifying the offending reg from a catastrophic loss of gas with an H valve. Perhaps a more practical approach would be just dive a single jacked up steel and tank mount AL 40's on either side. One being the redundant bottom gas and the other being deco gas. Of course gas planning will need to be done right to make sure you have the gas to complete the dive considering all of the different types of gas failures.

I found this photo from SpearBoard. The removable 40's seem to makes this a much more practical setup for small vessels.

View attachment 548383

 

[RyanT]

That was me! #legend

Now you know what tailgates are for!

 

[KevinNM]

Now you know what tailgates are for!

He wanted a new regulator anyhow...

 

[Germie]

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.

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.