Closed 2 Beuchat Y-Valves

[Teknadv3x]

Valves are in great shape
Only been in fresh water.
$225 Total for both valves....
S&H included to the lower 48 states.

Remember The key to underwater survival is Redundancy ,Redundancy Redundancy

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[Teknadv3x]

Valves sold .

 

[Angelo Farina]

These are probably the best valves available for a single tank... I never recommend using an octopus, always better to have two completely separate regs.
And with these valves you get not only separates valves, but truly independent air paths, including two independent dip pipes.
The resulting redundancy and safety are almost the same as using twin tanks. In a certain sense they are even safer, as there is no manifold with O-rings which could fail..

 

[tursiops]

The resulting redundancy and safety are almost the same as using twin tanks. In a certain sense they are even safer, as there is no manifold with O-rings which could fail..

Come mai?
Trying to express polite disbelief....

 

[Schwob]

Come mai?
Trying to express polite disbelief....

So, this is a thread on a sold product, but I may have never truly understood:

Ignoring overall gas volume, so why is it that a modern day doubles set-up with manifold is considered safer (=less failure prone?) & / or more redundant than a single tank with such a separate air path Y-valve?
I just seem to be missing something that seems obvious to everyone else...

Should I get treated to a comparison from a failure likelihood and recovery option point of view... can we add independent doubles into the comparison as well?

 

[Angelo Farina]

Come mai?
Trying to express polite disbelief....

These Y-valves with fully separate air paths are less safe than a double as you cannot separate the tanks, as modern manifolds allow to do. In some cases, separating the two tanks can be advantageous, for example in the rare event that air leaks from the O-ring between the valve and the cylinder. I have seen this happen (and the post mortem analysis did show that this was due to the usage of a low-hardness O-ring, not rated for 300 bars).
But they are also safer than a double, as there is no risk that the manifold starts leaking gas, as I have seen a couple of times (in both cases due to mishandling).

 

[Angelo Farina]

These Y-valves with fully separate air paths are less safe than a double as you cannot separate the tanks, as modern manifolds allow to do. In some cases, separating the two tanks can be advantageous, for example in the rare event that air leaks from the O-ring between the valve and the cylinder. I have seen this happen (and the post mortem analysis did show that this was due to the usage of a low-hardness O-ring, not rated for 300 bars).
But they are also safer than a double, as there is no risk that the manifold starts leaking gas, as I have seen a couple of times (in both cases due to mishandling).

Independent doubles also have their advantages and disadvantages. Without a communicating manifold, if one of the two regs fails, you loose all the air trapped in that cylinder... On the other hand, there is no risk of air leakage from the manifold.
For maximum safety and ultimate redundancy the better solution would be to have two independent cylinders, each equipped with one of these Y-valves, and each cylinder mounting two completely independent regulators (which means a total of FOUR regs). I have never seen this being done, but if you search maximum redundancy this is the way!

 

[tursiops]

I think of more and less safe as being correlated with more and less risk in the configuration.
The risk is typically assessed as the product of the likelihood of the event, times the impact of the event, should it happen.
High likelihood is usually associated with low impact, and vice-versa.

For example, failure of a neck o-ring on a tank is high-impact, but is quite rare, whereas failure of a second stage is much more common, but low impact...especially if it is mitigated by an alternative second stage.

What we normally do is try and mitigate with equipment and training and procedures all those "likely" things -- some of which have relatively higher impact, such as loss or non-availability of breathing gas; examples are alternate 2nd stages, dual first stages, and SPGs. We may also wish to try and mitigate some of the unlikely things (because they are usua;y high-impact), such as neck o-ring blowouts, dip-valve clogging, and manifold failures.

What we CAN'T validly do is simply count o-rings and say that fewer is safer. It is all trade-offs; if adding o-rings means adding risk-mitigation measures -- such as an alternate 2nd stage -- then it is OK to have those extra o-rings, because their unlikely failure is more than balanced by the usefulness of the alternate 2nd.

So, is an H-valve safer than a Y-valve? No....it only has one dip-tube and shares an air path for both second stages.
Is either safer on a single tank? Yes, because two first stages is better than just one.
Is a single tank with a H- or Y-valve safer than (a) manifolded doubles, or (b) independent doubles?
No, because there is only one air-supply with a single tank. That is such high-impact that the low likelihood of failure of the single-tank o-ring is no longer important; you need to mitigate this possibility, however remote. (b) is safer than (a), because the manifold is part of (a). However, manifold failures are rare, and isolation solve the problem in situ. That is why training with manifolded doubles emphasizes using the isolation valve.

@Angelo Farina says he has seen several failures of Y-valves and manifolds, both due to poor maintenance or handling. I would suggest the proper approach to mitigating those kinds of failures is better training, procedures, maintenance, handling, and NOT trying to have fewer o-rings.

We each have to decide where our own risk-tolerance is. Mine is with Sidemount for a high-jeopardy dive; total redundancy, no manifold, and I can see the valves and all the regs.

 

[tursiops]

For maximum safety and ultimate redundancy the better solution would be to have two independent cylinders, each equipped with one of these Y-valves, and each cylinder mounting two completely independent regulators (which means a total of FOUR regs). I have never seen this being done, but if you search maximum redundancy this is the way!

Yes, but then you have to consider the likelihood of more than one regulator failing at the same time. VERY low probability. Not worth trying to mitigate. If it is important to you, why not 3, or 4 regs on a cylinder?

 

[Angelo Farina]

This topic is becoming interesting....
Tursiops, I agree entirely with what you wrote. In fact I see that some configurations have advantages but also disadvantages.
Regarding the failures I have seen (manifolds and the O-ring between the cylinder and the valve), they all occurred with doubles. Two manifolds and one valve O-ring, for the precision. Never seen an O-ring failure on a single. But once, on a single (rented), with H-valve and two independent regs, I experienced myself occlusion of the dip pipe due to rust, and it was not pleasant...
So I am a big fan of these Beuchat Y-valves with two separate dip pipes.
Then, when possible, of course using two separate cylinders in side mounting is much safer. Unfortunately this is not always possible, in many places you are given just a single cylinder, 12 liters, and no H or Y valve, just a single valve and a regulator with an octopus, which is less safe than two independent regs. Possibly even with a Yoke, instead of DIN. And an old-style jacket BCD with rear mounting of the single bottle. When you are forced to travel light, you cannot use your own equipment, and you have to survive with what is available in a remote location...