Taboo GUE

[MXGratefulDiver]

The failure is "not paying attention". If you run out of gas solo because you're stupid, you still have gas on you if you have isolated cylinders. Manifolded, when you're out, you're out.

Not so far fetched ... this was posted recently on another board ...

To end all speculation, this is what really happened on that day. I failed to clearly set in my mind, a maximum depth for the dive. I was looking for the barge in front of Salty's and came under the effects of nitrogen narcosis and was swimming on "autopilot". I had no intention to go past 190 ft that day. When I swam back to 190ft and came back to my senses I realized to my great dismay, that I was breathing the last of the air from my dual 100's. I had 53% in 1 40cf and 100% in my other 40cf and knew that I couldnt breathe it at that depth, so I had to make a rapid ascent to 80 ft but, I did so in a controlled manner, did not suffer an expansion injury. I was able to make my switches and even made the switches on my computer but I had a hard time with bouyancy due to my empty tanks and air expansion in my suit and bc from the rapid ascent. I did not have enough weight to compensate for the empty tanks. I have never had an empty tank... always come up with at least 1000psi... when I was forced to the surface I knew that I only had minutes before DCS symptoms took over. By the grace of God the Water Taxi was there when I came up. I was able to flag them down and yell what was happening to me and swam to the back of the boat before I passed out. The next thing I remember was two weeks later and I was being wheeled out of the critical care unit headed to ICU. I am going to have a permanent vision disability due to hypoxia in the optic nerve. But otherwise I'm making a full physical recovery. Thanks again for all the prayers and support!

... Bob (Grateful Diver)

 

[Doc Harry]

GUE does not advocate solo.... But I know of at least one GUE diver who regularly solos.

 

[rx7diver]

You could (and should IMO) learn proper gas shutdown procedures, which would prevent you from losing all your back gas in that situation.

I think he's he refers to simultaneous oring failures on both sides of the manifold. In that specific situation, you would lose all back gas. IMO that is such an improbable situation that the benefits of soloing with a manifold outweigh the risk of having that failure happen.

Yeah, I guess I see what you mean, but that, to me anyway, is pretty far-fetched and borders on ridiculous.

James_R and Slamfire,

Consider this: While diving you bump your manifold hard against something which thereby simultaneously causes your manifold to leak and prevents your isolation valve from being able to isolate your manifolded back tanks. Does this seem unlikely to you?

One brief story: One sunny, hot afternoon I was packing my sports car to go diving. I loaded my HP doubles, but uncharacteristically did not cover them with the foil-type windshield sun screen I usually used to protect them from the direct sunlight which otherwise would shine full on them through the hatchback backlight. When after about 30 minutes I returned to my car with more stuff, I was greeted with a loud hissing noise. No, it wasn't the burst disk(s)! After the tanks drained, I disassembled the manifold and discovered that two of its four isolation valve O-rings had evidently become so hot that they had softened and become partially extruded and became the source of the gas leak. These two O-rings were on opposite sides of the isolation valve component. An otherwise properly functioning isolation valve could *not* have prevented the total loss of gas. It occurred to me that if I had returned to my car a few minutes earlier, before the O-rings had become sufficiently softened, I might never have known how compromised the manifold had become, and I might have dove those doubles just as they were. And the two O-rings might have failed during the dive!


Problem is, sometimes our intuition fails to consider all possible failure modes and, consequently, fails to correctly assess likelihood of failure.

Safe Diving,

Ronald

 

[sylpha]

You could (and should IMO) learn proper gas shutdown procedures, which would prevent you from losing all your back gas in that situation.

i know about 80 people who dive with manifolded twins, of those i think that 2 would be quick enough to get to the isolation valve before the back gas was exhausted. Those 2 did all the same training as the others, but they practise the skils on every dive so it's on autopilot. when something happens you automatically go into shock & hesitate - that could kill you.

 

[cbrich]

James_R and Slamfire,

Consider this: While diving you bump your manifold hard against something which thereby simultaneously causes your manifold to leak and prevents your isolation valve from being able to isolate your manifolded back tanks. Does this seem unlikely to you?

One brief story: One sunny, hot afternoon I was packing my sports car to go diving. I loaded my HP doubles, but uncharacteristically did not cover them with the foil-type windshield sun screen I usually used to protect them from the direct sunlight which otherwise would shine full on them through the hatchback backlight. When after about 30 minutes I returned to my car with more stuff, I was greeted with a loud hissing noise. No, it wasn't the burst disk(s)! After the tanks drained, I disassembled the manifold and discovered that two of its four isolation valve O-rings had evidently become so hot that they had softened and become partially extruded and became the source of the gas leak. These two O-rings were on opposite sides of the isolation valve component. An otherwise properly functioning isolation valve could *not* have prevented the total loss of gas. It occurred to me that if I had returned to my car a few minutes earlier, before the O-rings had become sufficiently softened, I might never have known how compromised the manifold had become, and I might have dove those doubles just as they were. And the two O-rings might have failed during the dive!


Problem is, sometimes our intuition fails to consider all possible failure modes and, consequently, fails to correctly assess likelihood of failure.

Safe Diving,

Ronald

I see your point, regarding the bumping your manifold, but since this is in Solo Diving Thread, you should not be Solo diving in an overhead environment. I took the SDI solo course, and they recommend solo diving in a recreational environment, no overhead environment. If you go outside of teaching will the infamous Scuba Police come after you, off course not, but Murphy might tho.

How hot did the manifold get when sitting in your car for 30 minutes? I ask because EPDM o-rings restist temperature up to 200*F, and Viton o-rings restist temperature up +400*F. I have left my double HP100s, AL80 of 50%, and AL80 of 100% sit in my car all day long, outside temperature getting in the 100+*F. I have never had a problem with the manifold o-rings extruding due to heat. However, I use 90 durometer Viton o-rings for all of o-rings on my cylinders. I have cut several manifold o-rings because of the fit between the valve, and manifold (or tolerance between shaft and hole); but that only happens when I forgot to lube the o-rings with Christolube.

Also do you replace the manifold o-rings every year, when you VIP cylinders, and replace all o-rings on your valve?

i know about 80 people who dive with manifolded twins, of those i think that 2 would be quick enough to get to the isolation valve before the back gas was exhausted. Those 2 did all the same training as the others, but they practise the skils on every dive so it's on autopilot. when something happens you automatically go into shock & hesitate - that could kill you.

I am kinda confused by your response, everyone that dives doubles should do a valve shutdown drill on every dive for the practice, and the manifold isolation valve should not be obstructed at all. The isolator valve should be in easy reach, and should also turn easily too. I can personally do a complete valve shut down drill in under 15 seconds, this is closing and opening each valve (but if I am shutting down just the isolator, that is only a few seconds). If you take worst case scenario a free flow reg, or a cut hose, you could be losing gas anywhere from 60 cfm to 300 cfm. (but you would not go for the isolator first, you go for the right or left post valve) So at 300 cfm, I would lose 30 cubic feet of gas in 10 seconds. For my double HP100s that is 1/2 of my reserve. My next course of action would be to "Thumb the Dive" and get the hell out of Dodge.

All of my dive planning is based on rule of thirds for Solo, and Decompression dives.

Can I have a cylinder neck o-ring that leaks, of course. Can I get a leak from any o-ring of couse. However I try to minimizing leaks from o-rings by replacing them everyear, and lubing them properly. When I dive Trimix and spend $100 on a fill the last thing I want to happen is lose the gas to an o-ring that was not replaced because I was too cheap to replace a $0.05 o-ring.

We can spend all day long discussing the "What Ifs", but all we can do, is do our best to minimize the "What Ifs", and accept the risk of the "What Ifs." If these "What Ifs" pose too much of a risk, then you should stop what you are doing, and do something else.

 

[rx7diver]

... [You] should not be Solo diving in an overhead environment. I took the SDI solo course, and they recommend solo diving in a recreational environment, no overhead environment.

Cbrich,

I think you'll find that many solo divers do not limit their solo diving to only non-overhead, recreational environments--regardless of what is taught in the SDI Solo Diving certification course.

How hot did the manifold get when sitting in your car for 30 minutes? I ask because EPDM o-rings restist temperature up to 200*F, and Viton o-rings restist temperature up +400*F. I have left my double HP100s, AL80 of 50%, and AL80 of 100% sit in my car all day long, outside temperature getting in the 100+*F. I have never had a problem with the manifold o-rings extruding due to heat. However, I use 90 durometer Viton o-rings for all of o-rings on my cylinders. I have cut several manifold o-rings because of the fit between the valve, and manifold (or tolerance between shaft and hole); but that only happens when I forgot to lube the o-rings with Christolube.

Also do you replace the manifold o-rings every year, when you VIP cylinders, and replace all o-rings on your valve?

The tanks and manifold were pretty d---ed hot from lying prone enclosed in the back of my car under direct sunlight. This was the original Sherwood Genesis Double-DIN Isolation Manifold (introduced in the late 1980's shortly after the Genesis HP cylinders appeared on the market). It was almost brand new when this incident happened. (I still own it, though I haven't used it in many years; I've got some photos of it somewhere in one of my posts from a few months ago.) I had never disassembled it up till then. IIRC, these O-rings appeared to be urethane.

Re your last question: I personally only occasionally (i.e., rarely) disassembled and rebuilt my manifolds/valves, replacing their internal O-rings and high-pressure seats. Certainly, I did not do this routinely. My oxygen-compatible valves that might see high octane Nitrox, I oxygen cleaned initially, but then thereafter made sure they only saw clean gas.

Safe Diving,

Ronald

 

[sylpha]

I am kinda confused by your response, everyone that dives doubles should do a valve shutdown drill on every dive for the practice, and the manifold isolation valve should not be obstructed at all. The isolator valve should be in easy reach, and should also turn easily too. I can personally do a complete valve shut down drill in under 15 seconds, this is closing and opening each valve (but if I am shutting down just the isolator, that is only a few seconds). If you take worst case scenario a free flow reg, or a cut hose, you could be losing gas anywhere from 60 cfm to 300 cfm. (but you would not go for the isolator first, you go for the right or left post valve) So at 300 cfm, I would lose 30 cubic feet of gas in 10 seconds. For my double HP100s that is 1/2 of my reserve. My next course of action would be to "Thumb the Dive" and get the hell out of Dodge.

We can spend all day long discussing the "What Ifs", but all we can do, is do our best to minimize the "What Ifs", and accept the risk of the "What Ifs." If these "What Ifs" pose too much of a risk, then you should stop what you are doing, and do something else.[/QUOTE]

Sorry, but it's human nature, just like i promise myself i will do 50 sit ups every morning & by the time i get to bed i'm too tired to even think about it, but i'll do them tomorrow. there are those who simply did the course to get the ticket so they can buy trimix and they have been diving for ever so long so they know what they are doing (yeah right). When a hose blows the first thing that happens is that you hesitate & think 'what the hell happened' unless you go into autopilot and do your shutdowns that hesitation is a killer. it's not a what if, it's something i have seen happen and happily we both came out OK. if you choose manifold it's your choice, we could argue the pros & cons forever, but i believe for the type of diving i do my system works best for me.