Regulator Necklace as it relates to Sidemount

[Kevrumbo]

Same way as in every sidemount config that is not explicitly cave related.

But what about overestimated lifetime of hoses on your back in that scenario?

I'll let you know if that scenario ever happens. More likely to inadvertently snag/cut one of my tank supply hoses inside the tight forward confines of the I-169 Japanese Submarine Wreck at 36m here in Truk Lagoon (where a Backmount Doubles Dive Guide would be delayed & held up at a few aft restrictions before getting to me).

I would shut down that cylinder, and if the other cylinder catastrophically "OPV's" open, I would then try to feather/modulate the tank valves of either cylinder as a last resort while making my way back aft to the Dive Guide, or if I'm stuck in a hatch restriction, hopefully waiting 'til the Dive Guide makes his way to me.

And in addition, what about a total siltout with a Primary & Secondary Light Failure to go along with all that? And quadruple failures all happening at the same time???

 

[AfterDark]

deleted

 

[decompression]

Raz, hoses do fail, whether BM or SM, although in thousands of dives I've only seen a few and never on my gear. The difference being usually in SM it's more noticeable depending on the failure. If it's on Z system near the manifold, a) odds are it's noticeable, follow protocol and b) if it's not noticeable instantly, it will be by your team or when checking your SPG (protocol) then follow protocol. Not quite as catastrophic as I think you're making it out.


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[SanDiegoSidemount]

Raz, hoses do fail, whether BM or SM, although in thousands of dives I've only seen a few and never on my gear. The difference being usually in SM it's more noticeable depending on the failure. If it's on Z system near the manifold, a) odds are it's noticeable, follow protocol and b) if it's not noticeable instantly, it will be by your team or when checking your SPG (protocol) then follow protocol. Not quite as catastrophic as I think you're making it out.

Especially non-catastrophic with the isolation manifold:

1. Isolate.
2. Keep breathing off the good side.

And if the failure is between the QC-6 and manifold, then:

3. Gas switch to plug the other tank on the good side when the first source runs out.

 

[Razorista]

Now, don't get me wrong you two (or three).
I am already convinced that in practice the manifolded system is more interesting than in theory.
Wouldn't think of using it myself, but I would certainly not be as nervous with a divepartner using it anymore as I was a few month ago (and the dive did not go that well for his regulators, but that seems to have been bad luck and insufficient training, I now think).

But:
You have two hoses running from first stage to manifold.
Those cannot be isolated from each other, can they?
They also can be disconnected from the tank, but not from the manifold, right?
If one of those breaks you have the manifold flooded or bubbling and useless and also every hose connected to it, don't you?

Also: solid brass or steel objects like the manifold are prone to production errors.
In theory you could get one that just breaks in half one day.
Remote chance, of course, but stranger things have happened.

 

[SanDiegoSidemount]

You have two hoses running from first stage to manifold.
Those cannot be isolated from each other, can they?

Yes they can. It's just like backmount doubles: one gas supply (input) per side. The output hoses are: long hose from the right side, necklace from the left. BCD inflate from the right, drysuit from the left. Isolator valve closed makes the two sides independent.

They also can be disconnected from the tank, but not from the manifold, right?

The tank connections are also one per side, left & right. The disconnect is an LP fitting (QC-6) between manifold & each first stage.

If one of those breaks you have the manifold flooded or bubbling and useless and also every hose connected to it, don't you?

No, only one side is rendered inoperable. Similar to a single post failure in back mount doubles.

So with an LP failure upstream from the QC-6 connector and isolator closed, you would have either long hose & BC inoperable (right side failure), or necklace & drysuit inoperable (left side failure), but never all of them.

 

[Razorista]

Yes they can. It's just like backmount doubles: one gas supply (input) per side. The output hoses are: long hose from the right side, necklace from the left. (Also BCD inflate from the right, drysuit from the left.) Isolator valve closed makes the two sides independent.

Oh, sorry, I misunderstood. I was told both tanks stay accessible when isolated, than both regulators do, now only one in both cases.
It sure seems complicated

But that also seems even more 'disturbing':

So the procedure will have you react to a freeflow by shutting of that side, but again if something happens behind your back you have to guess and might even shut off all of your gas for a second if guessing wrong (which will not happen in backmount, normaly).

The tank connections are also one per side, left & right. The disconnect is an LP fitting (QC-6) between manifold & each first stage.

But that's leaving you with about a foot of hose you cannot see on those in addition to the regulator hoses (in contrast to only the outermost loop of the longhose down the right sided tank in conventional sidemount, or even none at all with shorthoses only).

No, only one side is rendered inoperable. Similar to a single post failure in back mount doubles.

When I asked that a few weeks ago I misunderstood or got that reversed somehow.
I never dove both myself. Only with someone using the non-isolating distribution block once or twice.

So with an LP failure upstream from the QC-6 connector and isolator closed, you would have either long hose & BC inoperable (right side failure), or necklace & drysuit inoperable (left side failure), but never all of them.

Leaving also one tank inoperable until you reconnect the quick connect from one side to the other, right this time?
This will happen every time you isolate, for whatever reason, even a simple second stage freeflow, right?
That leaves you without any source of air while reconnecting, not that dangerous I am sure, but also not 'good procedure'.

 

[SanDiegoSidemount]

Oh, sorry, I misunderstood. I was told both tanks stay accessible when isolated, than both regulators do, now only one in both cases.
It sure seems complicated

But that also seems even more 'disturbing'

I don't find it overly complicated, especially if you practice your failures. Honestly, it's one of those things that's more complicated to explain than it is to use.

So the procedure will have you react to a freeflow by shutting of that side, but again if something happens behind you back you have to guess and might even shut of all of you gas for a second if guessing wrong.

We're talking about isolating first. So nothing's "shut off", you've just isolated left from right. Valve shutdown is a related issue, but that comes next after you've figured out the bad side.

But that's leaving you with about a foot of hose you cannot see on those in addition to the regulator hoses (in contrast to only the outermost loop of the longhose down the right sided tank in conventional sidemount, or even none at all with shorthoses only).

Yes, true. But assuming you are UTD trained as well, it means you would always have a buddy to help you assess the problem and find the "bad side" if the failure was around back. UTD divers don't dive solo.

Leaving also one tank inoperable until you reconnect the quick connect from one side to the other, right this time?
This will happen every time you isolate, for whatever reason, even a simple second stage freeflow, right?
That leaves you without any airsource while reconnecting, not that dangerous I am sure, bat also not 'good procedure'.

Procedure here is to share gas with your buddy during your switch.

A similar LP failure in independent sidemount would render the tank useless unless you do a first stage regulator swap. That would also involve a gas share with your buddy as well, right? And somewhat riskier to swap first stages than cross-plugging a tank.

In my opinion, IndySM and Z both have strengths and weaknesses. I've chosen the latter, trained thoroughly, and I'm comfortable with the potential failures and the procedures for handling them.

I'm sure you feel the same about IndySM.

Our opinions may differ, and that's fine with me. We're both well trained and comfortable with our gear. I'd be happy to dive with you on IndySM and me on Z, and I'm pretty certain we'll have a great time and nobody's "gonna die" from their gear choices. ;-)

 

[Razorista]

Actuality the way you explained it the only weakness seems to be for the solo or isolated diver with a lot of bad luck at once.
On the other hand, I was that guy often enough and I am not even cave diving yet.

Thanks for explaining. I will never like it, but I dislike it much less, as I already said.
Since z-systems are very rare here this was very interesting for me.

And sorry to the threadopener for taking part in the off-topic discussion that much, but it was a related topic at least.:blinking:

 

[SanDiegoSidemount]

And back to the OP's question...

As you can see, there are lots of options for regulator configuration in sidemount. All of the safer solutions from an OOG perspective pretty much involve a necklace.

Those of us who use the Z system like the fact that we breathe from a donateable long hose all the time, with a necklace backup, just like in backmount. The left/right failure cases and resolutions are quite similar to backmount doubles as well.

Many IndySM configurations also use a long+necklace setup. The safest of those IMO use a long hose on both sides, and a breakaway necklace so either second stage is easily donateable from the mouth.

Easy, no-questions-asked, no-thought-required donation using the regulator in your mouth is a primary tenet of DIR and a benefit the Z system as well, so I like this IndySM configuration as well. The shortcoming here is that your backup after you donate is not always around your neck. Sometimes it's clipped to your right shoulder, but that's not a huge deal.

Other configurations keep the necklace hose short, and use a breakaway clip on the long-hose second stage so it can be grabbed from the shoulder D-ring in an emergency. In this case the necklace is "no-donate".

The dilemma here is that if you're donating, you need to think about which regulator you're breathing before you donate to an OOG buddy. You may be able to donate from the mouth, or you may need to donate from your right shoulder. And in zero-vis, your buddy can't always rely on tap-tap-tap-taking the reg that's in your mouth.

If you don't care about sharing gas with your buddy, then none of this matters one bit.

Of course there are plenty of other ways to rig it, these just seem to be the most popular and safety-minded ways, most likely to get you and your buddy out alive if things go sideways.