JJ CCR newbie questions

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doctormike

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Hi,

I just certified on the JJ CCR (mod 1) on a rental unit, and I'm getting ready to pull the trigger on ordering one. I have a few questions, maybe some of you have some insights.

1) I know that this is a design choice made by JJ, but I'm wondering about the benefit of a constant flow O2 system on an eCCR (i.e., an hCCR). There must be a downside to that right? I'm assuming that a leaky valve theoretically could have been added to the JJ, so I'm just wondering about the argument against it. Is it that inattention could lead to hyperoxia with PO2 spikes?

I could also fly the JJ manually, like in my training, I just wouldn't have that constant flow backup, I would only have the solenoid as a parachute. Is the idea that an orifice is less likely to fail than a solenoid?


2) I have seen this discussed here before, and I understand that it's somewhat controversial. I'm confused about safety certification levels, specifically the difference between CE and SIL / EN61508 / Functional Safety, which I haven't been able to sort out with google. I'm not sure if this is a question of a competing standard and a market share issue. I am referring specifically to the material published by Deep Life, including the rebreather fatality database.

I notice several times in the database that the functional safety of the Shearwater controller has been questioned. I'm not sure that I understand this point, it seems that they are saying that the controller doesn't pass CE certification. This may be dated information - I understand that it took a while for the new DiveCAN Petrel controller to pass CE, but to the best of my knowledge it now has.

Here are a few excerpts from this document - I do understand about that 0.19 set point issue, and I agree that it would be good to be able to remove that option.

All prior JJ-CCR fatalities have been using Shearwater eCCR controllers which are not certified Functionally Safe and appear to cause the diver to have gone Hypoxic on descent; though the specific cause of this fatality has yet to be determined.

Hypoxia in this eCCR may be due to lack of oxygen in the cylinder, the valve turned off, a faulty solenoid, corroded solenoid, low power supply or faulty electronics / flawed oxygen injection programming, faulty design of the diver display ergonomics limiting monitoring visibility at all times and/or faulty/damaged oxygen cells. It is noted the Shearwater controllers have a very dangerous mode, where it allows set points of less than 0.7 atm. For example, divers often set 0.19 atm on the surface to save the battery, just because the unit does not have a reliable detector to switch the unit on when the diver starts breathing. With a PPO2 controller controlling PPO2 to within +/-0.1atm, it does not take much for a diver to become hypoxic on one of these units. Recently another failure mode with the Shearwater controllers has become apparent that may explain these cold accidents: if the diver is shallow and the controller isn’t even on – does it then not turn on if its cold….Petrel won't turn on in water


4th near identical JJ-CCR fatality (diver either on surface or submerging, in cold water) on this particular model of rebreather which is fitted with a non functionally safe Shearwater eCCR controller

Further on current failure of the Shearwater eCCR controller to pass CE certification at http://www.jj-ccr.com/media/30198/ce-letter_2014-07-10.pdf


Any thoughts?

Thanks!

Mike
 
2) I have seen this discussed here before, and I understand that it's somewhat controversial. I'm confused about safety certification levels, specifically the difference between CE and SIL / EN61508 / Functional Safety, which I haven't been able to sort out with google. I'm not sure if this is a question of a competing standard and a market share issue. I am referring specifically to the material published by Deep Life, including the rebreather fatality database.

*** My noob view ***
Forget about Deep Life and that "database". If you look up the Wes Skiles case, you'll understand why I'm saying that. (and even before that case actually, but well.). Their "super duper up to date list" has not been updated to reflect that the guys behind Deep Life (don't know if it's Brad or his buddies, it doesn't really matter, all that is needed is to know they're linked) have lost that court case. However, they had already claimed everywhere there is a design fault. That pretty much says it all about that "company", Brad Horn or any of his buddies imnho.

That database can imo only be used to know that there's been accidents on rebreathers, which, AFAIK, everybody was aware of.

I'm not qualified to answer the other "real" questions though :wink:
 
There's several threads on SB calling into question the credibility of deep life's analyses. I thought I even remember accusations of conflicts of interest, but maybe I'm mistaken.
 
*** My noob view ***
Forget about Deep Life and that "database". If you look up the Wes Skiles case, you'll understand why I'm saying that. (and even before that case actually, but well.). Their "super duper up to date list" has not been updated to reflect that the guys behind Deep Life (don't know if it's Brad or his buddies, it doesn't really matter, all that is needed is to know they're linked) have lost that court case. However, they had already claimed everywhere there is a design fault. That pretty much says it all about that "company", Brad Horn or any of his buddies imnho.

That database can imo only be used to know that there's been accidents on rebreathers, which, AFAIK, everybody was aware of.

I'm not qualified to answer the other "real" questions though :wink:

Thanks!

I mean, there are obviously rebreather accidents. I guess I was just wondering about the specific conclusions about the Shearwater controller, which didn't make sense to me.
 
1) I know that this is a design choice made by JJ, but I'm wondering about the benefit of a constant flow O2 system on an eCCR (i.e., an hCCR). There must be a downside to that right? I'm assuming that a leaky valve theoretically could have been added to the JJ, so I'm just wondering about the argument against it. Is it that inattention could lead to hyperoxia with PO2 spikes?

I could also fly the JJ manually, like in my training, I just wouldn't have that constant flow backup, I would only have the solenoid as a parachute. Is the idea that an orifice is less likely to fail than a solenoid?

I dive a KISS, which uses a constant mass flow orifice.

With a leaky valve you will either need to block off the IP compensation on the O2 feed regulator, or have a mechanism to adjust the flow rate "on the fly" (such as a needle valve). If you don't, the amount of O2 (in molecules) that is injected into the loop will go up as you descend, causing O2 spikes.

The downside of having a fixed IP on your O2 feed is that you will become depth limited. Once you go past a certain depth, your O2 stops flowing. That depth is basically 1ATM less than the IP of the regulator -- if the IP of your O2 regulator is fixed at 11BAR, you're basically limited to 10ATA, which works out to 297' before your O2 stops flowing, probably suitable for most people.

There are tricks you can do to get a constant mass flow system deeper, such as using smaller orifices and increasing your fixed IP, but it really will boil down to what you want to use the system for.

FWIW, I'm looking at pulling the trigger on an eCCR sometime this fall. The JJ is one of the units I'm looking closely at. I will not be making it into a hybrid, I plan to just dive it as a straight eCCR.
 
I dive a KISS, which uses a constant mass flow orifice.

With a leaky valve you will either need to block off the IP compensation on the O2 feed regulator, or have a mechanism to adjust the flow rate "on the fly" (such as a needle valve). If you don't, the amount of O2 (in molecules) that is injected into the loop will go up as you descend, causing O2 spikes.

The downside of having a fixed IP on your O2 feed is that you will become depth limited. Once you go past a certain depth, your O2 stops flowing. That depth is basically 1ATM less than the IP of the regulator -- if the IP of your O2 regulator is fixed at 11BAR, you're basically limited to 10ATA, which works out to 297' before your O2 stops flowing, probably suitable for most people.

Thanks! Yes, I should have posted my typical diving profile. I'm aware of the depth limitation, it just was never an issue with me because I have no interest in very deep dives. I currently dive mid range wrecks (up to 120-160 fsw), and I do a lot of photography (was interested in the sea life interaction issue of the CCR).

FWIW, I'm looking at pulling the trigger on an eCCR sometime this fall. The JJ is one of the units I'm looking closely at. I will not be making it into a hybrid, I plan to just dive it as a straight eCCR.

That's good to hear! I don't think that you can make the JJ into a hybrid (which implies some sort of constant flow, right?), but you can fly it manually. What is your thinking there?
 
I could make it into a hybrid if I really wanted to. Replace the O2 MAV with one with a leaky valve, and viola! :)

But I'd just fly it manually and leave the solenoid as a parachute. That's what I've done the very few times I've been on an eCCR.
 
I could make it into a hybrid if I really wanted to. Replace the O2 MAV with one with a leaky valve, and viola! :)

But I'd just fly it manually and leave the solenoid as a parachute. That's what I've done the very few times I've been on an eCCR.

Thanks...
 
I wouldn't trust a damn thing that came out of Alex Deas or any of his cronies. He was tapped as the "expert witness" in the Wes Skiles case. Turns out his witness testimony consisted of putting an unmanned O2ptima at the bottom of a pool and filming it with an iPhone in a plastic baggy while one of his associates tried to fabricate evidence through a variety of forum posts on this and other rebreather-centric sites.

It's not the first time either. Back in the early "aughts" he was as witness for a plaintiff trying to sue APD because a dude died on an Inspo. He was shut down years ago, but he keeps trying to weasel his way back so that he can sell units. Read this article: Rebreather Firm Wins Its First U.S. Lawsuit: Undercurrent 02/2009

When your business plan is to try and have your competitors sued off the marketplace.......let's just say that any info you receive from anything associated with Deep Life, Alex Deas, Brad Horn, or the APOC rebreather should be suspect at best.

Shearwater got rid of the .19 setpoint option. Easier to do that and make divers replace batteries more frequently than deal with guys who can't be bothered to actually follow procedure. I know my Meg checklist has a setpoint check in it, so does my Pelagian. If I am willing to ignore those and jump in the water with a computer that isn't on, isn't ready to dive, valves off, I deserve whatever comes my way, and there's no piece of gear that is capable of saving me. "Functional Safety" won't turn on an O2 valve, no matter how angry the computer is. You cannot engineer out human stupidity, no matter how hard you try.

As for making a hybrid, make sure you understand the implication of a constant O2 injection into the loop. I'm not a fan of CMF, I am however a fan of an adjustable orifice a la needle valve. Using the electronics as a parachute is desirable, and using the needle valve plus manual injection to maintain setpoint keeps you aware. There are arguments both for and against, personally I'm a fan. Just remember that the goal isn't to match your metabolic rate, it's to adjust it to be slightly below so that you get PO2 decay which you compensate for, not PO2 spike. Theoretically, a hyperoxic loop spike shouldn't be possible if the injection rate is set correctly. You'd do something like keep your setpoint at .7 and manually fly it at 1.2, or you'd keep your electronics setpoint at 1.2, and just use the needle valve to maximize time between solenoid firing, letting the electronics handle the addition. However, I'm not aware of how the manufacturers require instruction on the hybrid units.

Whether or not the JJ has an O2 t-piece MAV option would be something you'd need to investigate. You'd probably just have to swap out the standard MAV for a needle valve unit like Chris Kennedy makes. Shouldn't be too difficult but I'm not very familiar with the JJ units.
 
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what Ken said.

Advantages of some sort of leaky valve, either a fixed orifice a la KISS or a needle valve, is it saves the battery on your solenoid, and if for some reason your solenoid fails, you can just keep going on mCCR mode. Disadvantage is with the KISS valve you are depth limited by IP, but if you plan on diving deeper you just fly it in full manual or in the case of hCCR let the solenoid do the driving. The bigger disadvantage of the KISS valve in an hCCR is the fact that you need dual O2 regulators because one has to have a fixed IP to keep the leaky valve happy, and if you want to go deeper, you need one that is compensating. Needle valve has the advantage of being able to be driven off of the same O2 regulator and is literally as simple as swapping your O2 MAV for one with a needle valve and voila instant hCCR. Needle valve is a little finicky in terms of requires user input to keep tabs on your O2 addition since you get more O2 coming in due to higher IP at depth, but you can always shut it off for descent, and crack it open once you stabilize at depth.

Chris Kennedy has an affordable high quality needle valve MAV and you can find him on the CCR forums
 
https://www.shearwater.com/products/swift/

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