Revo divers and their insane cell theories

[Paulo]

I saw this online today and was alarmed to say the least.

Given that the origin of the post has not been CCR diving long enough to have a cell expire on age, nevermind one reach 30 months, their blasé attitude must have been indoctrinated somewhere. I have seen similar mindsets from revo divers elsewhere. How are revo units the only ones that are immune to 12-18 month cell rotation plans?

That's the beauty of having 5 cells. With 3 you have to pre-emptively change them. With 5 you can see if one's failing and run them for longer.

[cathal]

These might be of help -

http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf

http://www.revo-rebreathers.com/wp-content/uploads/2017/01/Understanding-Oxygen-Sensors-part-II_the-complete-picture.pdf

Sent from my iPhone using Tapatalk

[Paulo]

These might be of help -

http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf

http://www.revo-rebreathers.com/wp-content/uploads/2017/01/Understanding-Oxygen-Sensors-part-II_the-complete-picture.pdf

Sent from my iPhone using Tapatalk

Not really but I know another man with very weird notions about CCRs that posts PDFs at every opportunity too.

I am not saying you need to change them all at the same time, even though it is a perfectly valid policy, but even your own referenced linknshows that cell failure incidence is markedly higher with age and is hugely higher as cells are over 18 months old, yet revo divers are quite content to have a 29 month old cell in use as "there are three good ones in there"

[dwhitlow]

I saw this online today and was alarmed to say the least.

Given that the origin of the post has not been CCR diving long enough to have a cell expire on age, nevermind one reach 30 months, their blasé attitude must have been indoctrinated somewhere. I have seen similar mindsets from revo divers elsewhere. How are revo units the only ones that are immune to 12-18 month cell rotation plans?

I think rule #2 covers this quite well

[Benfool]

I'm a rEvo diver and definitely wouldn't be happy running cells that are 29 months old. I personally use 4 cells, 3 for my predator and 3 for my n@90 HUD with 2 cell splitters.

I make sure that the 3 in my predator are less than 12 months old and I might allow the 4th to be up to 18 months old - but it depends on what I'm doing.

B

[cathal]

Not really but I know another man with very weird notions about CCRs that posts PDFs at every opportunity too.

I am not saying you need to change them all at the same time, even though it is a perfectly valid policy, but even your own referenced linknshows that cell failure incidence is markedly higher with age and is hugely higher as cells are over 18 months old, yet revo divers are quite content to have a 29 month old cell in use as "there are three good ones in there"

Page 16 - 18 of the first paper pretty much sums up the cell replacement paradigm. If you are still unsure just email the manufacturer directly.


Sent from my iPhone using Tapatalk

[Paulo]

I get that some people like the additional cells and the perception that it creates more info for them to be able to make decisions on. However, I do not get how keeping a cell for as long as people advocate is appropriate. If you want to have 5 cells fine, knock yourself out but why not replace one every 3 months? That way the oldest cell is less than 18 months.

Also if having more cells is the "best" approach, why do all of the other manufacturers, at least to my knowledge, only fit 3? I am not aware of a single other manufacturer designing more that 3 cells as part of the factory spec.

[dwhitlow]

I get that some people like the additional cells and the perception that it creates more info for them to be able to make decisions on. However, I do not get how keeping a cell for as long as people advocate is appropriate. If you want to have 5 cells fine, knock yourself out but why not replace one every 3 months? That way the oldest cell is less than 18 months.

Also if having more cells is the "best" approach, why do all of the other manufacturers, at least to my knowledge, only fit 3? I am not aware of a single other manufacturer designing more that 3 cells as part of the factory spec.

Perhaps the same logic as having a 6 wheel vehicle and not worrying about the unreliable tyres on the ASSumption there's enough to cover the failures?

[1st Ade]

Perhaps the same logic as having a 6 wheel vehicle and not worrying about the unreliable tyres on the ASSumption there's enough to cover the failures?

Or the divers we used to have in the good old days - "I don't need to surface with 50 bar - I have a Pony!"

[colinicky]

Or the divers we used to have in the good old days - "I don't need to surface with 50 bar - I have a Pony!"

But how do you know you have 50 bar left if you don’t have a gauge ?

[colinicky]

You could use the same arguement of why have scrubber monitors as to why have 5 cells . Manufacturers have recommended time intervals for changing scrubbers then give you a monitoring system that “allows” you to extend that time , it does not mean you will or should just that you can .
I have dived a rEvo for years with 5 cells, before that I dived an inspiration running 3 cells . At one point my inspo cells were between 18 months & 3 years old & still tracked fine . But I have had a cell fail 4 weeks after being fitted & it was only 2 months from manufacture date ( old days of Teledyne) so personally I will keep track of what my cells are telling me in comparison to the rest before throwing one away.
Going back to scrubbers how in the old days of AP recommendation of 3 hours would you have ever done long deep dives with masses of deco without going over the 3 hours unless you go open circuit or a “twinspiration”

[graham_hk]

If 5 is better than 3 why not have it 6 or 7 or 9 ... where does it stop? Sounds overly complicated for my liking - rather than three which I replace within 12mo of manufacture and I don't trust any one more than the other - any cell can fail at any time often in an insidious or hitherto unknown way.

[cathal]

From Page 14 of the first rEvo paper that I posted above "the system rEvo already advises for some time, ‘rotating sensors’: the system works as follows: as soon as the youngest of all sensors in your system (3, 4 or 5) reaches the age of 6 months, you replace the weakest (the one that reacts the slowest on PPO2 changes, or the one
that seems to become closest to current limiting, during the test at 6/7meters), or if you can’t find a ‘weakest’, then the oldest in your system"

This is the actual rEvo policy on cell changing, you are replacing the weakest cell not necessarily the oldest.

[cathal]

If 5 is better than 3 why not have it 6 or 7 or 9 ... where does it stop? Sounds overly complicated for my liking - rather than three which I replace within 12mo of manufacture and I don't trust any one more than the other - any cell can fail at any time often in an insidious or hitherto unknown way.

From the first rEvo paper posted above - "And, why not use more then 5 sensors then? 6 or 7… There seems no need to, as long as you can spread the sensors over different systems, the likelihood that more then 2 fail is very low anyway, but your total consumption of sensors/year will increase. And in most cases, when adding sensors every 6 months, and keeping more then 5 sensors in your system, the oldest sensors will have failed before they should be replaced because of lack of place"

[colinicky]

Why use more than 3 sensors ? So let’s step back a bit . Would DIR , GUE etc recommend doing any deep ( 100m for arguement) dive with only one computer ? Ie no back up ? Of course not . So why would we dive CCR with only one ? Now logically you may have your main controller then a back, but unless you plumb the back up in you are not going to have deco based on real Ppo2 readings so you have 2 options take a best guess or wire it in but that gives you 2 options again , do you use 3 cells & 3 cell splitters or do you add cells to give you a totally independent back up ? If you use cell splitters across 3 cells only & a cell fails then you are back to square one of dil flushes to be certain which cell is no correct .
Personally I run 5 cells with only one of them using a splitter . 3 to the Nerd 1 controller & 3 to the nerd 2 back up .