Adaptor for single tank regulator redundancy?

[bdives85]

@Outbound check out this thread: XT1 1st stage failed CLOSED at depth

@rongoodman - Overthinking? Probably so. But isn't that part of learning?

@MarkA - I agree, the lack of an isolation mechanism on the T-valve seems like a deficiency.

That said, I suppose out of the two potential scenarios: (a) having a single 1st stage that fails in closed position versus (b) having two first stages and one fails in the open position with no way to isolate it--- scenario b would be preferable. At least then I would have air.

 

[inquis]

Do you have experience with this T-adaptor? Works well? Issues? Weird looks from charter operators?

No experience with it, but it's a pretty simple device. Yes, I think you can count on those looks from charter operators.

I don't know of any modern reg that doesn't fail open, but I'm not a reg expert by any means. As others have astutely pointed out, there are various issues that your T-adapter will simply not address.

If you're still concerned, a 19 cuft bottle can be carried on flights and will handle an ascent from anywhere in recreational depths. Take a transfill whip and you can fill it from your normal AL80, equalizing at ~2400 psi (165 bar). There are many reasons a pony bottle is the standard for recreational solo divers.

 

[Tassie_Rohan]

@Outbound check out this thread: XT1 1st stage failed CLOSED at depth

That said, I suppose out of the two potential scenarios: (a) having a single 1st stage that fails in closed position versus (b) having two first stages and one fails in the open position with no way to isolate it--- scenario b would be preferable. At least then I would have air.

The XT1 failing closed really is a one in a million failure due to a manufacturing defect or incorrect assembly. If you are doing the first dive on a brand new reg, or a reg back from service, then make the dive an easy one and/or keep a buddy on hand for that one dive.

For your scenario B: whats the point of having two first stages with one free flowing that cant be turned off? You are still going to loose air. Its normal procedure to breath off your free flowing reg to use some of the escaping air as you ascend.

The only times I've heard of a regulator failing to deliver air is when someone jumps in with their air off or, very rarely, unmaintained tanks with a lot of rust and water inside that blocks the tank valve dip tube or first stage. It takes a lot of neglect to get a tank to that point.

More common are free flows due to cold water (ie <10C) or due to a hose or O ring becoming loose. Under such circumstances you need to either turn off the free-flowing regulator and switch to another, or switch to a separate tank, depending on where the leak is.

The device you suggest has no shut off valves, so is useless in all of the above cases: all it does is add a few failure points without any benefit.

Below are test results for the time to empty a tank based on the more common failures: in the worse case scenario you still have plenty of time to head over to your buddy, and/or start an ascent. If still concerned then stress buddy contact for any depths your not comfortable doing an emergency ascent from, or bring proper redundancy.

Cheers
Rohan.

 

[Nick_Radov]

Regulators are designed to fail safe, meaning they will fail open and not closed. Unless I’m not understanding what you’re saying.

That's almost always true. Modern first stage regulators are pretty bulletproof. There are some weird old Poseidon upstream regulators that can fail closed in rare circumstances. And Aqua Lung had to recall some regulators because the Auto Closure Device (ACD) could fail closed.

A Catastrophic Regulator Failure: Undercurrent 04/2019

While second stages usually fail open in a way that you can still breathe, they can become completely unusable due to debris getting inside or mechanical failure. I had an old Scubapro G250 crack in half once. A backup second stage is sufficient to handle those failures.

A more common scenario with badly maintained rental tanks is that interior corrosion debris blocks gas flow through the valve or gets stuck inside the first stage. If you want to protect against that then you need good team skills or another tank of some sort.

This Nautilus T- Adapter seems rather silly. It introduces more failure points and doesn't solve any real world problem.

 

[bipolarbear]

I understand what you're trying to achieve, but I would go about it a different way.

If you're thinking about redundancy, that's great, and you're already well ahead of the curve. You're already a safer diver than most in the water.

As long as you're only conducting dives within your NDL, H and Y valves don't really achieve much. These are more aimed at cold water / ice diving, where you might have a hard ceiling and a temperature-induced free flow. For dives within NDL, I think that diving with a trusted buddy and/or slinging say an AL30 or AL40 is the appropriate solution.

If you are looking to exceed NDLs (yes, even 5 minutes of 'planned backgas deco') then you really should be looking at doubles or side mount.

90% of my diving is open circuit tech/decompression diving. When I travel to locations where I'm doing recreational profiles, I will take a twinset if they are available. If not, then I'll just dive a single tank standard regulator configuration, dive conservatively within my NDL, and always maintain a clear path to the surface.

 

[bdives85]

Thanks for all the feedback. You have convinced me that it is indeed a silly idea.

I think it’s safe to say that the incidence of free flows events is much higher than the incidence of failure-to-closed events. While putting two first stages on a T-valve could help protect against the low probability scenario, it would effectively double the risk of the higher probability scenario, while also adding additional potential failure points on top of that. All around bad idea.

Oh well.

 

[grantmac]

That's almost always true. Modern first stage regulators are pretty bulletproof. There are some weird old Poseidon upstream regulators that can fail closed in rare circumstances. And Aqua Lung had to recall some regulators because the Auto Closure Device (ACD) could fail closed.

A Catastrophic Regulator Failure: Undercurrent 04/2019

While second stages usually fail open in a way that you can still breathe, they can become completely unusable due to debris getting inside or mechanical failure. I had an old Scubapro G250 crack in half once. A backup second stage is sufficient to handle those failures.

A more common scenario with badly maintained rental tanks is that interior corrosion debris blocks gas flow through the valve or gets stuck inside the first stage. If you want to protect against that then you need good team skills or another tank of some sort.

This Nautilus T- Adapter seems rather silly. It introduces more failure points and doesn't solve any real world problem.

This information isn't correct regarding Poseidon regulators and hasn't been for at least 40 years.

For the OP: that bar device would actually impede getting to the valve handle in the case of a tank partially closed, offering if anything a worse outcome to the most common gas emergency.

 

[jborg]

I was going to say surely that T adapter is for splitting a fill whip for multiple tanks and not for diving with, but I then I did see at least one scuba shop listing it as for twin first stages on a tank...