Twinsets, redundancy, and what problem are we solving...

[sourdough]

With a twinset, you still have mechanical redundancy, but unless you isolate your tanks from one another, it is still possible to find yourself in an OOA situation with no reserve gas available.

I think that's an interesting subject, with traditional doubles it's one big store of gas being depleted simultaneously and if the diver fails to monitor for reserve or min gas, they end up in an oog incident the same as a singles diver, right? Instead of mechanical redundancy you're thinking about backup gas, yeah?

How common is diving with a pony bottle? I've only heard the term vaguely associated with technical diving.

 

[Wibble]

As an aside, all rebreather divers carry a "pony" which they refer to as their bailout gas. The difference with CCR training is that you constantly plan for the failure of the main unit and must carry more than enough gas to get you to the surface whilst completing all your decompression obligations. The planning is rigorous and often the whole maximum dive time and depth is constrained by the amount of bailout gas available.

I used my bailouts for real a couple of weeks ago. No issues as it was well planned for; was thoroughly practised; was thoroughly checked. I reached the surface with more than enough gas in reserve, shaken but not stirred as it were.

 

[PfcAJ]

Manifolded doubles require you to do something in event of a leak.

The benefit is that you have access to all the gas in event of the most common failure - a regulator issue.

If you just sit there catatonic and don’t act when there is a leak, then all you gas will leak out.

 

[Cthippo]

Yes. You practice closing this at the first sign of problems, i.e. if you suddenly get a cloud of bubbles around you, you calmly reach back and close the centre manifold to preserve at least half your gas (yes, a bit leaked out, don't be a pedant!) Then work out what to do; which side is leaking, so shut down one side and see if it abates; if not turn it back on and shut down the other side***.


***Most people who do the shutdown drills will inadvertently shut down both sides at the same time. Do it once; learn.

I get that, but I am not talking about an equipment failure but rather a user failure. In a situation where all equipment is fully functional, but for some reason the user exhausts their gas supply.

It seems to me that an alternate air source such as a pony (or sidemount) can mitigate this. What I'm asking is can a twinset mitigate this, and if not, is that considered a problem?

It sounds like the answer is no, it cannot, but that is not a risk that people feel needs to be mitigated through equipment.

 

[parzdiver]

I get that, but I am not talking about an equipment failure but rather a user failure. In a situation where all equipment is fully functional, but for some reason the user exhausts their gas supply.

Independent doubles, whether it is back mount, side mount, or a sling bottle, with make the diver more conscious of their gas consumption, but you are using an equipment change to fix a diver issue.

I'm in IT and have managers ask me to block certain web pages for certain individuals. "Joe spends too much time on YouTube." Me blocking YouTube for Joe doesn't fix the problem.

 

[Marie13]

But is a twinset redundant if the isolation valve is open? I understand the need for redundancy in hardware but does that redundancy still exist if we are creating essentially a single air source?

I guess what I'm really getting at is does the redundancy afforded by doubles do anything to mitigate user error? Does gear configuration reduce the chances, or in this case the consequences of a diver using up all their air because they are task saturated, narced, exerting themselves harder than they expected, or just not paying attention?

You’re really overthinking this. Tech divers go very deep and very far back in caves with doubles. The isolator is open.

 

[eelpout]

It has already mentioned above but more gas is the reason I even thought of putting twins on my back. The best visibility we could get on a consistent basis was Lake Superior. The best diving that you could do was on Shipwrecks. After diving the shallow one you yearned to dive the deeper ones. That required more gas (Boyles Law). Pony bottles were for emergency, small convenient but you still had to have enough gas to get to and from the wreck. As mentioned already above, diving with twin tanks requires training and experience.

 

[Wibble]

I get that, but I am not talking about an equipment failure but rather a user failure. In a situation where all equipment is fully functional, but for some reason the user exhausts their gas supply.

It seems to me that an alternate air source such as a pony (or sidemount) can mitigate this. What I'm asking is can a twinset mitigate this, and if not, is that considered a problem?

It sounds like the answer is no, it cannot, but that is not a risk that people feel needs to be mitigated through equipment.

Someone absolutely could drain a twinset with complete negligence. Failure to check your gas supplies is punishable by death.

Sidemount means they'd need to actively drain both sides -- would they bother to check their gas when switching?

 

[jadairiii]

A pony bottle/bailout bottle or doubles still require you to monitor you gas. 99% of all OOA emergencies are caused by poor gas management not equipment failure.

IF you have a catastrophic regulator failure on your singles rig, how fast can you deploy your pony rig? And are you 100% sure it will function when you need it?

 

[divad]

I get that, but I am not talking about an equipment failure but rather a user failure. In a situation where all equipment is fully functional, but for some reason the user exhausts their gas supply.

It seems to me that an alternate air source such as a pony (or sidemount) can mitigate this. What I'm asking is can a twinset mitigate this, and if not, is that considered a problem?

It sounds like the answer is no, it cannot, but that is not a risk that people feel needs to be mitigated through equipment.

Now yer just wanking.........................grasshopper