CCR Selection priorities

[king_of_battle]

1. Fathom MKII CCR .... Definitely a “Mercedes”

Hey now - don't badmouth the Fathom like that - its more like a Toyota - I can mostly fix it myself and it doesn't have to spend one week a month at the dealer getting fixed!

 

[hroark2112]

There are plenty of units that look great on paper, but after a couple hours in the water you ask the instructor why your diaphragm is sore and they respond with “well, your trim is too flat, it breathes best at about 30 degrees”.

If a unit doesn’t breathe it’s best when you’re in perfect trim, that’s a huge problem!! Run fast from that unit.

 

[kierentec]

Hey now - don't badmouth the Fathom like that - its more like a Toyota - I can mostly fix it myself and it doesn't have to spend one week a month at the dealer getting fixed!

haha, touché. Been a Toyota guy forever myself

 

[sea_ledford]

One thing I have learned in diving 2 different units (in several different configurations) is that WOB can be significantly impacted by the divers trim and positioning. At least one of my units breathes very easily if I am horizontal (which fortunately is 90%+ of the time) but breathes poorly if I'm in or near a vertical position, like on the surface. It makes waiting for a boat to come pick me up less than fun. Another unit I dive regularly does not have this issue, but one configuration of counterlungs is significantly easier to breathe and is much more comfortable than another.

I don't want to be too pedantic here, but WOB is NOT affected by position. Delta P is affected by position, which affects our perception of WOB. WOB is just the resistance caused by the specifics of the gas flow in the loop.

This really only matters if you are looking at a stated WOB value and trying to compare it to another WOB value. So, making up nonsensical numbers here, say an SF2 with a backmounted, bottom of the scrubber CL has a tested WOB of 257. An optima with front mounted CL has a WOB of 248. Pretty close values, but when you try them both, the Optima is awesome while you are head up and the SF2 is horrible. The WOB for each unit didn't change, the Delta P did.

I only say that to say don't get too caught up in the WOB battles, you probably aren't going to be able to tell anyway because it is masked by delta P. What you DO want to pay attention to is where the CL are vs your mouth and lungs when in diving position, or at the surface, or upside down, or on your back, or whatever position you want to be your deciding factor.

 

[rddvet]

thanks Brad, figured you’d show up.
.

Like a hemorrhoid you can't get rid of it. A pain in the ass and comes with a lot of sh!t

 

[rjack321]

Can anyone send me the published third party testing for the KISS Sidewinder?

Good luck with that lol
It'll fail miserably (at least in some orientations)

But I'm not sure any other SM CCR is demonstratively better

 

[oya]

I would like it if someone would tell me how well my rebreather breathed as measured by a machine for me.

 

[Brad_Horn]

One thing I have learned in diving 2 different units (in several different configurations) is that WOB can be significantly impacted by the divers trim and positioning. At least one of my units breathes very easily if I am horizontal (which fortunately is 90%+ of the time) but breathes poorly if I'm in or near a vertical position, like on the surface. It makes waiting for a boat to come pick me up less than fun. Another unit I dive regularly does not have this issue, but one configuration of counterlungs is significantly easier to breathe and is much more comfortable than another.

I think as mentioned above you are cross-patching your understanding of a rebreathers WOB with its Hydrostatic imbalance.

The WOB of the unit will never vary from that designed and tends to be tested in better quality units in both vertical and horizontal orientations throughout all testing criteria.
Hydrostatic imbalance is tested in all orientations, requires the unit to be rotatable and is a completely separate requirement for CE.

Examples:
WOB https://www.opensafetyglobal.com/Safety_files/DV_OR_WOB_Respiratory_C1_101111.pdf
Hydrostatic https://www.opensafetyglobal.com/Safety_files/DV_DLOR_HydroImbal_101116.pdf
With testing methodology, calibration requirements and results. This unit passes all testing; in comparison for alternative results see below Hollis testing report that they published.

Do you think that there would be any practical difference in the WOB? What about the same situation, except there’s just different electronics on the unit. This is essentially what I’m talking about, the variables just aren’t relevant to the testing, especially considering the testing criteria used for CCRs.

Neither will likely impact the WOB but they could and likely would impact in a measurable manner the units scrubber duration and PPO2 control as required for EN14143…. and life support.

Get the scrubber design wrong and it could have considerable impact on the WOB at the end of a dive if using granular sorb and it gets wet https://www.opensafetyglobal.com/Safety_files/Effect_of_flooding_with_granules_061027.pdf
Which I grant you is testing you will never see for granular rebreathers: that of the WOB towards the end of a dive compared to at the start…. And neither does CE testing currently require it. Unfortunately.

There are plenty of units that look great on paper, but after a couple hours in the water you ask the instructor why your diaphragm is sore and they respond with “well, your trim is too flat, it breathes best at about 30 degrees”.

If that’s the outcome they likely fail CE testing. And even if CE marked may not actually meet all requirements required of the standard. So fail the paper check before planning the dive….

But the reality is you can’t compare the performance of very many rebreathers on paper; because the testing suitable for direct comparative purposes simply doesn’t exist. And I don't just mean published testing either.
And hence the outcome you have experienced!

As a simple example that highlights this lack of ability to safely substitute different components between rebreathers or allow direct comparison on paper, feel free to compare the WOB in OC and CC modes of 3 different BOVs… I’ll give you one as a freebie:
1)OSELs ALVBOV
0.89J/L to EN250 50m/Air/62.5lpm in OC mode https://www.opensafetyglobal.com/Safety_files/DV_DL_ALVBOV_Breathing_Params_A3_100318.pdf
0.57J/L to EN14143 40m/Air/75lpm n CC mode https://www.opensafety.eu/datasheets/ALVBOV_40m_75lpm_air_081014.pdf

2)

3)

Care to share the extensive testing that the good people from Deep Life conducted on the optima as an expert witness for the Skiles case? That’s a good example of how relevant a lot of the third party testing is.

I guess that’s fair as no testing is available from DiveRite. See https://www.opensafetyglobal.com/Safety_files/DV_O2_cell_study_E4_160415.pdf Where they “Added explanation of how cells work, after discovery that some manufacturers were not aware of the fact that O2 must flow in and out of the cells freely, and if blocked by water, then the cell will continue to show the same PPO2 as before the water block occurred. See Sections 9.1.1, 9.1.2 and 10.1.8”

Any CCR is a critical life support system and your extrapolation equates to designing and building a new helicopter from other helicopter components and that because all of the components were previously tested in other helicopters then the new helicopter does not need testing.

Just to quibble this I’d suggest that while CCRs ought to be considered critical life support systems very few have been tested to ensure there is sufficient verification and validation of their capability of providing this function.

Great analogy with the caveat that you ought to be able to specify things like the engine in your new helicopter and get a variety of suitable options from different manufacturers with known and tested performance. Assuming all couplings are interchangeable if the performance of one engine is better than another and the weight/power etc etc doesn’t exceed the airframe design limits, you ought to be able to upgrade with no effect on your certification.
CE works this way. But the only single component CE certified on the market that you can actually do it with is the ALVBOV. As this has been proven to offer higher breathing performance than any other BOV/DSV on the market; so won’t adversely impact any rebreathers performance under CE testing when fitted. Indeed it will significantly improve a number.

I understand that CE testing is expensive and the "one and only one" configuration on the certificate is somewhat limited. I realize the value of CE testing, but I also do not use it as the be-all-end-all.

Why would there be a one and only configuration certification? CE is quite flexible. As long as you test it and there’s no degradation in performance in the units technical file it can be an approved configuration…

The Hollis P2 is an excellent example of this offering 3 different configurations and WOB outcomes: (reference Hollis published “Results from the testing of two Hollis Prism closed-circuit rebreathers” Feb 2019, QinetiQ)
FMCL DSV 1.67J/L vertical
FMCL BOV 1.90J/L horizontal
BMCL DSV 1.68J/L vertical
all at 40m on Air at 75Lpm albeit as noted the BOV was only tested in horizontal position and the higher worst case WOB result when vertical was not included. But by extrapolation would be somewhere in the order of 2.0J/L.

With the caveat for direct paper comparison that in Rear-mounted counterlung configuration
“It was noted that the movement of the rear-mounted counterlungs during ventilation could be restricted by the position of the wing buoyancy compensator (WBC), particularly if inflated. It was also of concern that the function of the exhalation counterlung variable exhaust valve (VEV) could also be compromised. Therefore, to ensure that any influence was kept to a minimum, the WBC was never inflated during testing.”
and notification that
“Throughout this report table cells shaded in green means that a particular test complied with the requirements of BS EN 14143: 2013, whereas red shading means that a particular test did not comply with the requirements of BS EN 14143: 2013.”

 

[kierentec]

I guess that’s fair as no testing is available from DiveRite. See https://www.opensafetyglobal.com/Safety_files/DV_O2_cell_study_E4_160415.pdf Where they “Added explanation of how cells work, after discovery that some manufacturers were not aware of the fact that O2 must flow in and out of the cells freely, and if blocked by water, then the cell will continue to show the same PPO2 as before the water block occurred. See Sections 9.1.1, 9.1.2 and 10.1.8”

Cool PDF. I guess you weren’t able to track down the actual video of the testing conducted to “prove” the point as expert witness testimony. No worries, I’ve got it right here for those in the audience who are unaware of the type of testing conducted by “deep life” and “open safety”.

 

[hroark2112]

That’s some high quality cell phone in a bad video!’ All we need now is some sticky water.