Meg Cell Bypass issue

Dive!Dive! · 22nd June 2008, 10:08

Folks
It seems well accepted that the cell configuration in a Meg offers the potential for bypass of CO2 in the event of a cell failure.
I dont want to get into a debate about how much of a problem it may or may not be, weather ISC should do a recall etc etc.
What I'd like to think about is what can we do about it.
Yes, theres the obvious answers like ' dive another unit' , but although I would like another unit (in additon to the Meg...!) thats not going to happen this year, and its in any case a shame as the Meg has plenty of positive points.
I have thought of a couple of things:
1. Redesigned sensor carriage with some sort of enclosure for the sensors. It would be a tight fit and this is beyond (way beyond) what I could do at home. Any of the 3rd party guys thinking about this ?
2. Doing something about the cells. Looking at them its really only the joint between the body and base plate of the casing thats the issue (I realise its possible the membrane could fail also, but you would have a warning of that on the unit). How about encasaing the cell in shrink wrap to physically reinforce the joint ? I dont know if there's space but it could work ?

Any other ideas?

Steve

teomannaskali · 22nd June 2008, 10:40

Talking completely out of mi arse here but shrinkwrap may solve that problem but the cell wont like being heating. Some people tape the cell...

A bit of bicycle inner tube, if it fits could make the cell stronger.

Another approach might be to put something in the back of the cell to hold it in place.
Try to find a bit of tube, or a bit of hose that fits exactly the extrusion on the butt of the cell, put a small hole in it for the cable and squeeze it between the assembly.

I think that would be the easiset diy solution....

PS: Only fiddled with a meg for a very very short time.

**wedivebc** · 22nd June 2008, 16:49

Here is my solution. Since the potential bypass involves the guts of the cell coming loose and bypassing through the large hole where the molex connectors go through, why not replace the cells with R17Ds and then if the guts of the cell come loose there will be no open path for CO2 to travel through. The phono jack connectors could even be installed with a little sealant if you're really paranoid.

Drmike · 23rd June 2008, 03:47

Quote: (Originally Posted by wedivebc)

Here is my solution. Since the potential bypass involves the guts of the cell coming loose and bypassing through the large hole where the molex connectors go through, why not replace the cells with R17Ds and then if the guts of the cell come loose there will be no open path for CO2 to travel through. The phono jack connectors could even be installed with a little sealant if you're really paranoid.

wont help. look at the pics of failed cell - thats not the way they fail

mempilot · 23rd June 2008, 03:58

Quote: (Originally Posted by Drmike)

wont help. look at the pics of failed cell - thats not the way they fail

After searching for this, the only threads I can find have to do with cell functionality failure and not physical failure.

Can you please link to the post with these pictures? I would like to see them.

Thanks!

AM · 23rd June 2008, 05:02

Quote: (Originally Posted by Dive!Dive!)

Folks
It seems well accepted that the cell configuration in a Meg offers the potential for bypass of CO2 in the event of a cell failure.
I dont want to get into a debate about how much of a problem it may or may not be, weather ISC should do a recall etc etc.

That is precisely the wrong attitude that is serving rebreather manufacturer's interests and not users.

Quote: (Originally Posted by Dive!Dive!)

What I'd like to think about is what can we do about it.
Yes, theres the obvious answers like ' dive another unit' , but although I would like another unit (in additon to the Meg...!) thats not going to happen this year, and its in any case a shame as the Meg has plenty of positive points.

Those positive points in my view are irrelevant if a user still has the fault that is capable of rendering a user impaired by severe CO2 without warning and no mitigation path by inspection/maintenance.

It is not within most users' remit nor professional scope to suggest alternative design ideas for potentially life-threatening failure modes. Furthermore, in doing so, you are completely undermining any effort to make ISC accountable for immediately taking the appropriate actions in relation to the number of current units still affected by this problem.

Quote: (Originally Posted by Dive!Dive!)

I have thought of a couple of things:
1. Redesigned sensor carriage with some sort of enclosure for the sensors. It would be a tight fit and this is beyond (way beyond) what I could do at home. Any of the 3rd party guys thinking about this ?
2. Doing something about the cells. Looking at them its really only the joint between the body and base plate of the casing thats the issue (I realise its possible the membrane could fail also, but you would have a warning of that on the unit). How about encasaing the cell in shrink wrap to physically reinforce the joint ? I dont know if there's space but it could work ?

NO. How about the manufacturer of the unit, which, let's not forget, is held out as life-support equipment by the general use of a solenoid and electronics, facilitates a safety notice/recall to all affected users. The onus is unquestionably upon the manufacturer to decide how to proceed, NOT the users.

Your solutions won't work in any case (don't mitigate the failure path) and do not provide scope for proper integration of sensor architecture alteration with the rest of the unit's functionality.

Regards

AnneMarie

**wedivebc** · 23rd June 2008, 05:06

Quote: (Originally Posted by Drmike)

wont help. look at the pics of failed cell - thats not the way they fail

Yeah but I thought that was an anomoly due to bad batch of cells. Joe Radomski mentioned a failure mode that involved the circuit board coming loose inside. This would at least reduce that risk. I do realize it was R17Ds which you had fail as well.

**wedivebc** · 23rd June 2008, 05:17

Quote: (Originally Posted by mempilot)

After searching for this, the only threads I can find have to do with cell functionality failure and not physical failure.

Can you please link to the post with these pictures? I would like to see them.

Thanks!

http://www.rebreatherworld.com/gener...tml#post112542

lancsman · 23rd June 2008, 10:18

Quote: (Originally Posted by am)

That is precisely the wrong attitude that is serving rebreather manufacturer's interests and not users.

NO. How about the manufacturer of the unit, which, let's not forget, is held out as life-support equipment by the general use of a solenoid and electronics, facilitates a safety notice/recall to all affected users. The onus is unquestionably upon the manufacturer to decide how to proceed, NOT the users.

Your solutions won't work in any case (don't mitigate the failure path) and do not provide scope for proper integration of sensor architecture alteration with the rest of the unit's functionality.

Whilst I agree that the manufacturer is responsible to provide a fix, if you have invested many thousadns of dollars on a unit and find an issue that the manufacturer is not doing any thing about then self help might be the only solution.

Since it seems the users voice is not working to get changes made it either sell the unit (and pass on a known fault to an other user) and buy one with out a fault or fix it yourself. I for one would prefare to fix it and then ensure I advise others not the buy that unit.

Mark

Drmike · 23rd June 2008, 11:34

http://www.rebreatherworld.com/rebre...tml#post180859

22nd June 2008, 10:08	#1 (permalink)
Dive!Dive! RBW Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2006 Location: Somerset, UK Posts: 101	Meg Cell Bypass issue Folks It seems well accepted that the cell configuration in a Meg offers the potential for bypass of CO2 in the event of a cell failure. I dont want to get into a debate about how much of a problem it may or may not be, weather ISC should do a recall etc etc. What I'd like to think about is what can we do about it. Yes, theres the obvious answers like ' dive another unit' , but although I would like another unit (in additon to the Meg...!) thats not going to happen this year, and its in any case a shame as the Meg has plenty of positive points. I have thought of a couple of things: 1. Redesigned sensor carriage with some sort of enclosure for the sensors. It would be a tight fit and this is beyond (way beyond) what I could do at home. Any of the 3rd party guys thinking about this ? 2. Doing something about the cells. Looking at them its really only the joint between the body and base plate of the casing thats the issue (I realise its possible the membrane could fail also, but you would have a warning of that on the unit). How about encasaing the cell in shrink wrap to physically reinforce the joint ? I dont know if there's space but it could work ? Any other ideas? Steve
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22nd June 2008, 10:40	#2 (permalink)
teomannaskali RBW Member Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 421	Re: Meg Cell Bypass issue Talking completely out of mi arse here but shrinkwrap may solve that problem but the cell wont like being heating. Some people tape the cell... A bit of bicycle inner tube, if it fits could make the cell stronger. Another approach might be to put something in the back of the cell to hold it in place. Try to find a bit of tube, or a bit of hose that fits exactly the extrusion on the butt of the cell, put a small hole in it for the cable and squeeze it between the assembly. I think that would be the easiset diy solution.... PS: Only fiddled with a meg for a very very short time.
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22nd June 2008, 16:49	#3 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,508	Re: Meg Cell Bypass issue Here is my solution. Since the potential bypass involves the guts of the cell coming loose and bypassing through the large hole where the molex connectors go through, why not replace the cells with R17Ds and then if the guts of the cell come loose there will be no open path for CO2 to travel through. The phono jack connectors could even be installed with a little sealant if you're really paranoid. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die Last edited by wedivebc : 22nd June 2008 at 16:51.
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23rd June 2008, 03:47	#4 (permalink)
Drmike RBW Member Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,378	Re: Meg Cell Bypass issue Quote: (Originally Posted by wedivebc) Here is my solution. Since the potential bypass involves the guts of the cell coming loose and bypassing through the large hole where the molex connectors go through, why not replace the cells with R17Ds and then if the guts of the cell come loose there will be no open path for CO2 to travel through. The phono jack connectors could even be installed with a little sealant if you're really paranoid. wont help. look at the pics of failed cell - thats not the way they fail __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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23rd June 2008, 03:58	#5 (permalink)
mempilot Eric Stadtmueller Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,708	Re: Meg Cell Bypass issue Quote: (Originally Posted by Drmike) wont help. look at the pics of failed cell - thats not the way they fail After searching for this, the only threads I can find have to do with cell functionality failure and not physical failure. Can you please link to the post with these pictures? I would like to see them. Thanks! __________________ Eric Stadtmueller, otherwise known as, MEM "Da Pilot"
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23rd June 2008, 05:02	#6 (permalink)
AM Banned Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Earth. Posts: 964	Re: Meg Cell Bypass issue Quote: (Originally Posted by Dive!Dive!) Folks It seems well accepted that the cell configuration in a Meg offers the potential for bypass of CO2 in the event of a cell failure. I dont want to get into a debate about how much of a problem it may or may not be, weather ISC should do a recall etc etc. That is precisely the wrong attitude that is serving rebreather manufacturer's interests and not users. Quote: (Originally Posted by Dive!Dive!) What I'd like to think about is what can we do about it. Yes, theres the obvious answers like ' dive another unit' , but although I would like another unit (in additon to the Meg...!) thats not going to happen this year, and its in any case a shame as the Meg has plenty of positive points. Those positive points in my view are irrelevant if a user still has the fault that is capable of rendering a user impaired by severe CO2 without warning and no mitigation path by inspection/maintenance. It is not within most users' remit nor professional scope to suggest alternative design ideas for potentially life-threatening failure modes. Furthermore, in doing so, you are completely undermining any effort to make ISC accountable for immediately taking the appropriate actions in relation to the number of current units still affected by this problem. Quote: (Originally Posted by Dive!Dive!) I have thought of a couple of things: 1. Redesigned sensor carriage with some sort of enclosure for the sensors. It would be a tight fit and this is beyond (way beyond) what I could do at home. Any of the 3rd party guys thinking about this ? 2. Doing something about the cells. Looking at them its really only the joint between the body and base plate of the casing thats the issue (I realise its possible the membrane could fail also, but you would have a warning of that on the unit). How about encasaing the cell in shrink wrap to physically reinforce the joint ? I dont know if there's space but it could work ? NO. How about the manufacturer of the unit, which, let's not forget, is held out as life-support equipment by the general use of a solenoid and electronics, facilitates a safety notice/recall to all affected users. The onus is unquestionably upon the manufacturer to decide how to proceed, NOT the users. Your solutions won't work in any case (don't mitigate the failure path) and do not provide scope for proper integration of sensor architecture alteration with the rest of the unit's functionality. Regards AnneMarie
(Offline)

23rd June 2008, 05:06	#7 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,508	Re: Meg Cell Bypass issue Quote: (Originally Posted by Drmike) wont help. look at the pics of failed cell - thats not the way they fail Yeah but I thought that was an anomoly due to bad batch of cells. Joe Radomski mentioned a failure mode that involved the circuit board coming loose inside. This would at least reduce that risk. I do realize it was R17Ds which you had fail as well. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
(Offline)

23rd June 2008, 05:17	#8 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,508	Re: Meg Cell Bypass issue Quote: (Originally Posted by mempilot) After searching for this, the only threads I can find have to do with cell functionality failure and not physical failure. Can you please link to the post with these pictures? I would like to see them. Thanks! http://www.rebreatherworld.com/gener...tml#post112542 __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
(Offline)

23rd June 2008, 10:18	#9 (permalink)
lancsman New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Megalodon Not Bought Yet Join Date: Oct 2005 Location: UK, Flitwick Posts: 64	Re: Meg Cell Bypass issue Quote: (Originally Posted by am) That is precisely the wrong attitude that is serving rebreather manufacturer's interests and not users. NO. How about the manufacturer of the unit, which, let's not forget, is held out as life-support equipment by the general use of a solenoid and electronics, facilitates a safety notice/recall to all affected users. The onus is unquestionably upon the manufacturer to decide how to proceed, NOT the users. Your solutions won't work in any case (don't mitigate the failure path) and do not provide scope for proper integration of sensor architecture alteration with the rest of the unit's functionality. Whilst I agree that the manufacturer is responsible to provide a fix, if you have invested many thousadns of dollars on a unit and find an issue that the manufacturer is not doing any thing about then self help might be the only solution. Since it seems the users voice is not working to get changes made it either sell the unit (and pass on a known fault to an other user) and buy one with out a fault or fix it yourself. I for one would prefare to fix it and then ensure I advise others not the buy that unit. Mark
(Offline)

23rd June 2008, 11:34	#10 (permalink)
Drmike RBW Member Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,378	Re: Meg Cell Bypass issue http://www.rebreatherworld.com/rebre...tml#post180859 __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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