Most Redundant OC SCUBA?

[John C. Ratliff]

Akimbo, that would be, in product safety lingo, a catastrophic single-point failure which would lead in this configuration to loss of gas supply. However, the safe second would still function as the gas supply diminished.

Also, you need to look at where in the sequence of events this is likely to occur. I have never seen it happen in 50+ years of diving. I have had "significant impacts" with the water during parascuba jumps, and never seen this happen too. You have seen it twice, as a result of what must be significant impact. By that description, it would most likely occur on the surface, either entering or exiting the water. Here, normal emergency procedures would be to drop weights and stay on the surface, perhaps with a snorkel in one's mouth. The likelyhood of this happening at depth is pretty low, IMO.

SeaRat

 

[victorzamora]

Akimbo, that would be, in product safety lingo, a catastrophic single-point failure which would lead in this configuration to loss of gas supply. However, the safe second would still function as the gas supply diminished.

Also, you need to look at where in the sequence of events this is likely to occur. I have never seen it happen in 50+ years of diving. I have had "significant impacts" with the water during parascuba jumps, and never seen this happen too. You have seen it twice, as a result of what must be significant impact. By that description, it would most likely occur on the surface, either entering or exiting the water. Here, normal emergency procedures would be to drop weights and stay on the surface, perhaps with a snorkel in one's mouth. The likelyhood of this happening at depth is pretty low, IMO.

SeaRat

I must say, what about in an overhead environment?

Sent from my SCH-I545 using Tapatalk 4

 

[John C. Ratliff]

Victorzamora, the operative word here is "significant impact." Overhead environments are underwater, and the "impact" would not be like jumping or rolling off a boat and hitting something on the way down. Or, like jumping out of a plane, having the regulator hose hang up on a part of the aircraft as the jumper bounced along the side of the aircraft (I have seen this out of an HC-130, but without damage to the scuba gear due mainly to the manifold guards we had on the scuba unit). Regulator LP hoses are very tough to damage, due in part to their need to absorb the "impact" of 140-160 psig air "hitting" them when the air is turned on.

A more likely scenario is if a hose is very old, decayed, and could come apart due to age and abuse over time. This is a concern of mine as I collect old dive gear, and I have had to decommission some LP hoses because of that. But I have never had one fail. This should be caught in normal maintenance of the gear, and these hoses replaced as needed.

SeaRat

 

[nimoh]

John

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

I never liked the use of the word "redundant" for backup breathing systems, even though I have used it. One of the most common definitions is:

adjective: redundant

1. not or no longer needed or useful; superfluous.

synonyms: unnecessary, not required, inessential, unessential, needless, unneeded, uncalled for;​

Probably not what you had in mind.

From Meriam-Webster, number 3 seems fairly applicable:

Full Definition of REDUNDANT

1
a : exceeding what is necessary or normal : superfluous
b : characterized by or containing an excess; specifically : using more words than necessary
c : characterized by similarity or repetition <a group of particularly redundant brick buildings>
d chiefly British : no longer needed for a job and hence laid off

2
: profuse, lavish

3
: serving as a duplicate for preventing failure of an entire system (as a spacecraft) upon failure of a single component
&#8212; re·dun·dant·ly adverb

 

[victorzamora]

John, I simply don't understand the need for this amount of complexity if you take certain possible failures out of the running. I'll admit that I think it's creative and unique, but by no means do I think that system is safer than Manifolded Doubles, Independant Doubles, or Sidemount.

For example, if one of your first stages lost an o-ring (has happened to me on two different, well maintained, nice brand 1st-stages) and they start providing full tank pressure instead of IP....your tank would drain due to the 2nd stage freeflowing. Due to the freeflow, wouldn't your demand lever from your other tank become depressed, emptying it as well? With ID or SM, you'd have no total loss of gas (max of 1/2 your gas) no matter what. With SM, you could easily feather the valve and breathe some of the rest of your tank. With MD, you would shut off that first stage and still have full access to both gases. I might be missing something, but I can't see it. In this case, how is it superior to any of the "standard" configurations?

All of the possible failure modes I can think of end with this being worse than the three "typical" configurations. As for gas demand, providing tons of gas shouldn't be an issue. I mean, if you're at great depth breathing hard enough to need more than a high performance set of regs can provide...you should reconsider a LOT of things about your diving (equipment AND planning).

I'm really not trying to be a jerk about this, I simply can't think of a scenario that would lend to this configuration being better in any way. Can you?

 

[Akimbo]

From Meriam-Webster, number 3 seems fairly applicable&#8230;

Yes, and the first two are not. That is the point. There are a number of other phrases that are unambiguous to non-engineering divers, especially if their native language is not English. It is not a question of incorrect usage, only a sub-optimal choice of words.

 

[nimoh]

Yes, and the first two are not. That is the point. There are a number of other phrases that are unambiguous to non-engineering divers, especially if their native language is not English. It is not a question of incorrect usage, only a sub-optimal choice of words.

point taken, although I have never met a diver (engineer or otherwise) that interpreted "redundant gas supply" as meaning it is superfluous or unnecessary...until now.

 

[lowviz]

...//... I simply can't think of a scenario that would lend to this configuration being better in any way. Can you?

It has a certain coolness to it, something was learned, you are talking to solo divers (maybe this would have been better in the solo forum), but the main reason is that John enjoys diving it. I think that due to the free-flow issue the configuration is sub-optimal but so what? I'm not answering for John, I really would like to hear his take on your question...

---------- Post added September 24th, 2013 at 04:55 PM ----------

I forgot a point, he makes people think. So what about a low pressure hose between the two secondary stages with a shut-off valve in the center? That really would take the nuisance out of ID's...

 

[John C. Ratliff]

Victorzamora, here is the quote in the op-ed:

I just put together perhaps the most advanced solo diving open circuit system available. I am using independent doubles, with two regulators (one a Scubapro first stage with a Dacor Olympic first stage on the other tank). These two regulators were set to the same IP (160 psig) and both hooked to a Scubapro A.I.R. I second stage. Because of the configuration, either tank could be independently turned off and the second stage would be fed from the other side. The Dacor Olypmic regulator had a Dacor safe second stage attached to it as an octopus.

I did use the word "redundant," but that was secondary. I dive in a river, in high current where regulator performance is crucial. The setup allows twice the air available at the second stage as other configurations. This is done with a regulator that I bought new in the 1980s. But the A.I.R. I would be hard to beat without this configuration by any of the newer regulators today. My point is that this is a redundant system, with the limitation of the O-ring/LP hose failure that has been pointed out. Yes, it is complex, and yes, probably unnecessary for most diving. My whole point was that it was a possibility that may not have been considered by any of you before, and it worked and worked well.

SeaRat

 

[Glenn08]

This question was intended for Akimbo:
What valves / regulator(s) are on your doubles ?