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
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