Cell Husbandry

Megangel1

Megangel1

Member
What IS the consensus on cell husbandry?

I was taught (if I recall properly)

1). remove cells from their shipping bag and expose to air for 24hrs to 'wake' up'
2). write month and year of install on the cells in perm marker
3). Calibrate/recalibrate when installed and then only when seen to drift
4). Discard after 12 months in service or if unreliable
5). Ideally stagger new cells on a 4 month basis
6). Set up a reminder to order new cells 1 month before needed
7). Regularly check dates written on cells ( I do this before every dive sequence )

What do people think is the best policy ?
a) If you have cell checker
b) If you don't

Please provide reasons for any departures from manufacturer's recommendations.
 
I was not taught that there were any limitations on calibration. More often is fine and if you can't recall when you calibrated then do it again. I have no idea why only calibrating "in moderation" would have been taught to anyone or why you need measurable drift before recalibrating.

I follow your list otherwise. I have a cell checker, but I bought it to check suspect cells not to check cells on a regular basis.
 
With the new vandie cells, I only recalibrate if the cells dont read .21.

I replace cells every year, but I replace mine all at the same time. Mainly because mixing every 4 months, you can wind up with difference responses on cells, based off of age or whatever. If the new age of cells werrent so good, I'd probably do the every 4 months rotation as well. But in several years now, I've seen no issues with all yearly replacement, but some issues from other divers rotating due to response rates, or other factors.

I only cell check if I get a cell that starts acting up. Then all cells are checked and evaluated.
 
I started putting installed dates on my cells in case I coped it on a dive and some arse pointed out my cells were two years old I wanted people to know they were only installed in the last 12 months.

I soak in pure 02 for an hour or two before putting them in the unit. I am not organised enough to prepair the cells the day before :D

Thats about it realy in terms of cells.

I replace May ish every year and stager each cell instalation but I am using the cells I baught a year ago and kept as spares.

I dont have a cell checker, but i do check my cells in air and 02 on asembly and I never calibrate over an error i always serch for the error first.

I always check to 1.6-1.8PP02 on water entry.

I always check against a known dill at max depth

I always spike my o2 at regular intervalls tomake sure my cells can read higer than the displayed value

I always dill flush and check cells if a cell goes significanly out of whack on a dive

I prefer to run my unit on low set point and manualy run set point via a needle valve and manual inject so I am in control of 02 addition

ECCR, voting logic and cells scare me a bit.

ATB

Mark
 
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I was really hoping this thread was instructions on how to create the right circumstances for two cells to make a third cell.
 
Darkness and excess alcohol. if it doesnt work for the cells, try it yourself....at least you'll see twice as many cells ;)
 
In addition to the date, I record the initial mv reading after the first calibration at 1.0. When it comes to replacing one cell every 4-6 months, it is not the oldest one I go for. It's the one that shows the largest % drop in mv from when it was new. I think that is a much better indicator of which one is likely to crap out first.
 
When traveling and checking your rebreather in the belly of the plane compartment, most likely the unit will be in a pelican type hard case, I recommend removing the cells/sensors from the unit and store them in a smaller plastic box with padding and bring this with you on the plane so that if the unit is dropped or thrown around, the sensors and cells will not absorb the heavy shocks and vibration from dropping the unit during transport from the belly compartment of the plane to the service area. In addition I'm sure that you have seen how the transportation workers off a load equipment from the conveyor belt of the plane and throw the luggage around.

Best regards,
Chett
 
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Mark Chase said:
I always check to 1.6-1.8PP02 on water entry.

I always check against a known dill at max depth

I always spike my o2 at regular intervalls tomake sure my cells can read higer than the displayed value

I always dill flush and check cells if a cell goes significanly out of whack on a dive.
Click to expand...

Good stuff, thanks for the input.

I do the first and third ones as above, likewise I can see the reasons for point four(verify whether it is one cell or two which is out of whack) but what about item two? Could you expand on why you do this?


Cheers
 
Megangel1 said:
Good stuff, thanks for the input.

I do the first and third ones as above, likewise I can see the reasons for point four(verify whether it is one cell or two which is out of whack) but what about item two? Could you expand on why you do this?


Cheers
Click to expand...


By Item 2 i am asuming you mean "I always check my cells against a known dill"


OK so I check in air and 02 on land and the cells appears to be reading OK and I spiked it so i know it can read at least 1.6+ but how accurate is it?

I jump in on low set point 0.7 and keep it on 0.7 to max depth

After my 02 spike ill vent fulley and suck in dill as i decend on the Schamerhorn slide.

By max depth I am prety much on pure diluient as the 02 wont be fireing and at that point i check my PP02 display.

Lets say i am on a 70m dive on 14/60

At the bottom of the shot I am expecting to see 1.1 ish on my display

If its displaying 0.8 something is wrong as I shouldent be able to drop below the dill PP02 value and i shouldn't have breathed down the 02 that quickly so ill flush fulley and re check

If its still showing 0.8 ill add a bit of 02.

Now its saying 1.2?

So my calibration must be a mile off as i know for sue I have 14/60 dill I filled from a J thats got noting else in it and I analised my gas.

If i ignored the low PP02 reading hiked the 02 to 1.3 id probably be runing 1.6 in the real world due to the calibration error

Scinario 2 is

I hit bottom and I am reading 1.3 ?

Dill flush and i am still reading 1.3?

turn 02 off Isolate 02 feed & dill flush and i am still on 1.3?

Its not going up so I dont have a 02 leek into the loop so my calibration is out. If I do the whole dive on the displayed 1.3 ill realy be doing it on 1.1 and my deco calculations will be out

This one has happened to me a couple of times on new cells reading high after they "woke up"

I have three choices.

I either

1, do the dive on a displayed 1.3 and use a back up computer runing deco on 1.1

2, I do the whole dive on 1.5 running a back up computer on 1.3

3, I abort the dive


Hope this clears it up for you.

ATB

Mark
 
Opinion here...

I believe that proper calibration and checks are more important during the placement of a new cell than changing a cell exactly on the 365th day.

Attention to detail with any calibration, attention to detail and thorough analysis of cell activity following a "voting" situation or other behavior is probably the biggest concern of mine.

I read a post from a student in a trimix course who posted that his second dive was called due to a cell failure of his instructor. I remember thinking while reading the post about what the failure could be, wonder how the cell failed, how they determined it was that cell, etc, then moved on to another post. A few days later I read that the instructor died on his rebreather from a suspected oxygen toxicity event.

Scary shit.

Cell husbandry or whatever you want to call it is as important or more important than any other task for a rebreather diver. How else are you going to know the most important thing...


Sent from my iPhone using Tapatalk
 
which reminds me its time for an incident report on that... the motto of this one though is, if a cell ****s up, replace it, just one cell and he'd be here today.

why Ron chose to move that cell instead of replace it still baffles me today.
 
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Jeff Pack said:
which reminds me its time for an incident report on that... the motto of this one though is, if a cell ****s up, replace it, just one cell and he'd be here today.

why Ron chose to move that cell instead of replace it still baffles me today.
Click to expand...


How would a good or bad cell kill / save somone?

Even if you dont do proper cell checks with dill at depth and 02 spikes, surely it would take three cells all reading an incorect PP02 and holding a stable 1.3 to kill a diver carrying out even the most rudamentory PP02 checks?
 
2 failed cells did him in, if he'd replaced the one that flared high, instead of moving it, he;d be alive today.

Classic case of 2 bad cells voting out a good one.
 
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