Dead in 7 minutes

[Curt Bowen]

http:/www.advanceddivermagazine.com/articles/leaky/leakyvalve.html

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---------- Post added August 31st, 2015 at 07:12 AM ----------

Dead in 7 Minutes - The importance of a constant flow oxygen orifice • ADVANCED DIVER MAGAZINE • By Curt Bowen

Clickable link

 

[dreamdive]

Very interesting and certainly another argument for diving a rEvo. I am curious why you chose a starting PPO2 of 0.7.

 

[Superlyte27]

Ever dove a revo to 300'? That leaky valve doesn't work at that depth. Enjoy SCR mode on your 3liter bottle.
Oh, unless you're going to modify the 1st stage beyond manufacturers recommendations to supply gas beyond 140psi. But I'd argue that that's more dangerous than a solenoid not firing and a diver not catching it and adding Oxygen with a manual add button.

And lets not even mention the dangers that come in with CO2 buildup from a 7 hour dive with bad WOB.
Yeah, I think I'll stick to my solenoid. (Oh, and I dove a rEvo for 3'ish years)

 

[dreamdive]

Ever dove a revo to 300'? That leaky valve doesn't work at that depth. Enjoy SCR mode on your 3liter bottle.
Oh, unless you're going to modify the 1st stage beyond manufacturers recommendations to supply gas beyond 140psi. But I'd argue that that's more dangerous than a solenoid not firing and a diver not catching it and adding Oxygen with a manual add button.

And lets not even mention the dangers that come in with CO2 buildup from a 7 hour dive with bad WOB.
Yeah, I think I'll stick to my solenoid. (Oh, and I dove a rEvo for 3'ish years)

Not only do I dive the rEvo to 300+ consistently, but I took it as far as 460. Yes, you are correct that the constant mass flow does not work, neither will the solenoid nor your oxygen addition and that is a good thing! Now if you dove your rEvo to those depths, you would know that. How are you diving SCR in that situation?
I also dive a Meg/pathfinder to those depths and I will shut my O2 off! Do you seriously not??? Have you considered what happens with a stuck solenoid firing pure O2 at 350+ft ??? Then again, the caves in Florida are not that deep anyway.

When you start diving those depths consistently, you might also want to consider taking an expedition CCR course.

In any event, I don't think your post matters much regarding what Curt has posted here. At least, that is my opinion.


Regards,

Claudia Roussos MD

 

[PfcAJ]

Rekt.

 

[Superlyte27]

Well, let's start piece by piece...

We'll take the SCR comment...
The people I watch taking the revo to 300' and beyond are doing so by matching their DIL to their maximum depth. So when the solenoid and leaky valve quit functioning, they hit the DIL button. The 1st stage on the DIL side is not capped, so it's depth compensating. I believe it remains 140psi over depth the whole way down. So, at 300' they're still able to pump DIL into the loop. So, let's say they have a common gas of 10/65. They're able to pump enough oxygen to survive, but their also pumping in a bunch of helium, even though they are already at depth. Their body is consuming the oxygen, requiring more and more button pushes. A 3 liter bottle of Oxygen lasts quite a while, but how long do you think 3 liters of 10/65 lasts when you need to keep pushing the manual add button on your DIL to sustain life? That's a question for Nathan S. who got to figure it out twice in the back of Indian. The answer is: Not very long. Sure, it's not exactly SCR, but you are adding O2 to live, but loop volume is increasing, so your venting, but then adding more O2 to live. So, it's not exactly SCR, but you should be able to get the point. No, I have no idea what side effects are caused by steroid use in SCR mode. That might be a question for another guy whose name also starts with P

So, back to my comments, which may or may not be relevant... Which is the lesser evil? Diving a poor WOB machine beyond 300' and circumventing the natural characteristics of the leaky valve? Or just diving a unit that can go that deep right out the box. There's a number of them available, all that come with better WOB. Yes, I do know the other two ways you guys are overcoming the limitations of the rEvo at depth. Take away this point... you buy a 12k unit, then got to modify it against Paul's recommendations to dive it to 300'. Awesome. No thanks.

 

[Curt Bowen]

Very interesting and certainly another argument for diving a rEvo. I am curious why you chose a starting PPO2 of 0.7.

I picked it as a mid range between a set point of .4 and 1.1. No other reason.

 

[tstormdiver]

Just paying attention to one's PPO2 on the wrist unit, & HUD, goes a long way. Having your head tucked away & not paying attention to your unit, is not a proper way to dive a CCR. When in doubt, bailout. It's really that simple.

 

[pickens_46929]

Take my comment here for what it is worth ($0.02) but I could easily have entitled that article / paper "Dead in 24 mins or less"... both resulted in PO2 level that were hypoxic after a period of time, albeit the one option provided a much greater time period which to happen. I agree that it would provided a buffer under which you might correctly manually add 02 to the loop or complete a short dive. However, if a diver failed to do anything, they would still wind up dead.

 

[wedivebc]

Take my comment here for what it is worth ($0.02) but I could easily have entitled that article / paper "Dead in 24 mins or less"... both resulted in PO2 level that were hypoxic after a period of time, albeit the one option provided a much greater time period which to happen. I agree that it would provided a buffer under which you might correctly manually add 02 to the loop or complete a short dive. However, if a diver failed to do anything, they would still wind up dead.

Not exactly a true comparison. I diver losing consiousness but retaining mouthpiece would lower their O2 metabolism to the point where the leaky valve would likely keep up to and posssibly exceed the O2 requirements and therefore survive for much, much longer. A rebreather with no O2 flow is going to kill the diver pretty much at the rate Curt has predicted. Mind you anyone who goes 7 minutes without checking their PPO2 is an idiot anyway.