Most Redundant OC SCUBA?

[John C. Ratliff]

John, what's the circular yellow thing next to your fins in the photo.

Redundant and redundancy typify the opposite meanings in the engineering environment I lived in. Redundancy is a backup system where redundant implies performing a function already served by another system and is by implication unnecessary. I never said it should not be used, only that there probably is a better choice of words, especially in an international forum where English isn't everyone's first language.

Back to that circular device...

I still prefer the term "redundant" rather than "backup" as both systems are being used simultaneously. In the event of a failure on one side, the other can be used without removing my mouthpiece simply by turning off the valve. And, according to the manufacturer and basic physics, air flow is potentially doubled into the second stage (not that I'm going deep, but that was the idea).

If you'll look at this NASA website, they do use the word "redundant" quite often. I grew up with NASA, and was a USAF Pararescueman during the Apollo era. I was one of the rescue crewmembers on standby alert for the Apollo 13 mission, and if something would have happened within their first minute of flight, it would have been our mission. As it was, their emergency happened on the way to the moon, and they came back, landing in a different ocean than the one my squadron was covering.

SeaRat

 

[lowviz]

...//... The A.I.R. I have a unique feature, which is a button which puts about a two-inch water pressure tension on the demand lever, which would stop runaway free flow in all but complete icing situations. ...//...

Ah.

Or you could put a Schrader coupling in each LP hose and then be able to hot-swap the entire main secondary at depth. But you might take some flack for that complication...

Keep thinking, I love it! Just don't kill yourself in the process.

 

[John C. Ratliff]

How do you deal with a second stage failure? The quick response of course is to switch to the alternate, but if both tanks are flowing through the primary second stage could you not have a scenario where you go OOA on both tanks?

From my perspective, I simply surface. I'm diving shallow, and solo. I would flip the second stage to the pre-dive configuration (lever up) to see whether that would counter any free flow situation, then if not I would surface. I'm to the age that I'm not pushing any limits in my diving.

SeaRat

 

[John C. Ratliff]

Not sure I understand all of that, but I personally do not like hoses sticking straight up out of the first stage. I am way too clumsy when going under stuff for that to be a good idea.

Agreed...I only did that after my initial configuration did not have the hose length I needed to make the dive. Here is what the original configuration looked like.

SeaRat

 

[John C. Ratliff]

John

What is that circular yellow thing hanging next to your fins?..

Akimbo, that is my "diving" helmet. It is a converted bicycle helmet that I have attached a snorkel to and dive. My reasoning is that it is yellow, on my head and therefore provides visibility for others to see me diving in a river with some jet boat traffic (I also dive a float, also yellow, with a diving flag saying "Diver Down.") The helmet might also provide some limited protection when I'm exiting the river, as I need to climb over slippery rocks and wear it over my 8mm neoprene hood.

SeaRat

 

[tamas970]

A relevant, rather lengthy discussion on redundant vs manifold systems: http://www.scubaboard.com/forums/basic-scuba-discussions/318285-twin-tanks-manifold-redundant.html

I'd rather go manifold and carry a 4L/30cuFt pony.

 

[chrpai]

View attachment 167066

(Weird, photo doesn't show. Banned?)

 

[Glenn08]

I have twin 50's mounted valves down with a Selpak manifold = 2 regulators, one on each valve.
What is your valve / first stage / second stage configuration ?

 

[John C. Ratliff]

I have twin 50's mounted valves down with a Selpak manifold = 2 regulators, one on each valve.
What is your valve / first stage / second stage configuration ?

Glenn, as you can see, the rig is independent with two J-valves, two regulator first stages which are connected to one Scubapro A.I.R. I second stage. Because they are tied together at the second stage, and both first stages have the same interstage pressure, my system uses air equally from each cylinder.

SeaRat

 

[Akimbo]

Maybe I missed it but what happens in the unlikely event of a regulator supply hose failure? I have seen hoses snap off at the first stage twice due to impact. One was on a bailout in the early days when we still wore them valve-up and the other was on Scuba.