Full disclosure: cell failure rate

teksimple

Some of you may know that I started CCRsense.com, primarily because I did not feel there were any web sites from which one could easily purchase replacement rebreather cells in 30 seconds or less. Nowadays there is plenty of excellent competition and for that reason CCRsense has shuttered its cyber storefront.

One thing I have not seen come from a cell manufacturer (nor anyone else who's business is selling oxygen sensors) is the statistical rate of failure or otherwise degradation of their oxygen sensors.

Slightly more than one in every ten cells CCRsense.com sold suffered a degradation or otherwise variance from output specification or linearity, as reported by the customer. And this is all in the 6 months that CCRsense was open. Now I did not test most of these cells, as the majority of them were sent directly back to the manufacturer for warranty replacement. Nor did I do extensive interviews with the customers to see if they had put them on the barbecue or exposed them to a loop flood or afternoon sun on the patio.

But nonetheless that number for me is quite surprising. Perhaps not to some of you who spend more time underwater than I do. It tells me that cell failure or degradation is not a rare event, and should be expected. It would be nice if that rate could be quite a bit lower. I have no idea what the reported cell failure rate of another manufacturer's might be, and other than rare studies like that by Rebreather World member Alex from Deep Life, I am not sure if there will ever be consistent efforts to objectively determine that rate. There are a lot of posts on this board describing cell failures from all manufacturers.

Is there a way to manufacture an oxygen cell with a significantly lower failure rate? I don't know for sure, but suspect that there probably is--for a price. Until there is full disclosure on failure rates from ALL parties, I doubt that market pressures will ever force manufacturers to make a better cell. All they have to do is make a cell that is as reliable as the other guy's. When we closed circuit divers cry rip off on a $75 cell, I doubt any manufacture could sell a $300 cell unless they could prove that it was that much better.

Rebreather oxygen sensors are assembled by hand, and tested before they leave the factory. I have attached some photos from a factory visit, showing just that, below. But I am not aware of any manufacturer that does statistically significant field testing with in-house teams of rebreather divers.

The manufacturers leave the field testing up to us. Just keep that in mind when you are diving with a cell on which your life depends, and balking at the price of a Narked @ 90 cell checker.

It is my opinion that every rebreather facility should have a cell checker. Split the cost among many CCR divers, and perhaps there may just be fewer "vitally challenged rebreather diver" posts.

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"I don't know the percentage of the Internet that's valid, do you? Jesus, it's scary." - Hunter S. Thompson

Mark Chase

I am fortunate enough to have a base point for a group of CCR divers localy. I am considering aproaching Pete to see if as a group we can purchase a cell tester.

However I am interested to know the cycle for cell testing.


Is this something we do on just new cells or is it a regular health check. If so whats the recommendation for checking periods?

ATB

Mark

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divetheworld

There are two failures on cells; degredation and "DOA". DOA doesnt necasarily mean straight out of the bag but might mean after first use or very early in its life. As each cell may degrade at a different rate, I would suggest a test 'out of the bag' with a saturation test at 1.3bar for a number of hours. Then periodic testing with a veiw to catching a cells degradation before it becomes a problem. The frequency of this test id dependant on the type of cell but every two months is not too frequent.

B

p.s.
Mark, if you need the latest software installing on your Pursuit, let me know and I will do it for you.

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Mark Chase

Thanks M8 Ill have a word with Pete later on as well.

ATB

Mark

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Is it supposed to make that noise ?

I took my unit to the dive shop and demanded they bolt on every thing that would fit.

Join my elite diving teem and get a Tshirt

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gathan

I made the move to the AIs last Spring after using the teledynes for many years, after reading the report previously mentioned. I personally am disapointed with the performance of the AIs:

- one cell was dead right out of the blocks;
- another has been inconsistent for a while now; and
- I find that they are much slower in response than the teledynes.

I probbly have been luckier than some others with the teledynes, but I have never had issues with them at all. I'm seriously thinking about going back to them.

Andre

Peter Piemonte

Andre: I agree. Though I have not had cell failures with the AI's, the response time is very much slower than the Teledynes. After using Teledynes for about 4 years, I have experienced only one that was DOA. I had very good performance from all the rest. Normally I change them out every 12-14 months anyway.
I have been using a mix of AI's and Teledynes in my KISS for about a year now.
Peter

Jonathan

Interesting stuff,

I've had a Telyd. cell fail within 2 dives (about a 2 years ago) and in the last 3 months another (from a different source), with approx 28 dives, 7 months use go do-da also. The second could be a case of 'past it's usage' but the other 2 cells, in for 4 months more and still holding steady...

They're clearly not standardly (hard-core) robust, henece 3.

Here's a slight change of track...
Not being a hard core technical electonics wize, how does the new cis-lunar poseidon Rebreather electonics deal with this... "end your dive"... I kinda like 3 cellls, just means you carry on knowing 1 cell is down.

[Not meaning to change focus on a strand - just 2 pints and a rum & coke kicking in].

Cheers,

J.