Failing +/- Sensor Carriage test

Freak214 · 27th August 2007, 15:03

Well its been just a little short of one year and my Meg finally had to sit a dive out... It was sad jumping in without it.

About midway through a week of diving in the Bahamas my Meg started to fail the positive/negative sensor carriage assembly test. While troubleshooting the problem I removed each of the o2 sensors and found that I could blow through cell 2 and 3.

Now, I have gone back and read the posts concerning this as a potential failure point but all I was able to locate were posts where this occurred with new cells or fairly new cells. Nothing about 11 month old cells

Is this just one of the failure modes of the sensors or did I do something to bring about this issue?

Thanks
JohnL

mempilot · 9th October 2007, 22:49

When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact.

Thanks,

Eric

**Monkey** · 10th October 2007, 02:56

Quote: (Originally Posted by mempilot)

When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact.

Thanks,

Eric

some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2..

basically you hold the carriage up to your mouth and blow with your hand over the other side...

mempilot · 10th October 2007, 03:05

Quote: (Originally Posted by Monkey)

some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2..

basically you hold the carriage up to your mouth and blow with your hand over the other side...

That's what I thought. Is this supported by ISC? Couldn't you actually be prematurely destroying your O2 sensor membranes by putting that kind of pressure on them? I've heard of people having pinholes in the membranes, saying they recognized the failure after doing this +/- sensor carriage test. Seems the test might be related to the failure?

**Monkey** · 10th October 2007, 03:15

Quote: (Originally Posted by mempilot)

That's what I thought. Is this supported by ISC? Couldn't you actually be prematurely destroying your O2 sensor membranes by putting that kind of pressure on them? I've heard of people having pinholes in the membranes, saying they recognized the failure after doing this +/- sensor carriage test. Seems the test might be related to the failure?

boy did this thread just ask for some people to throw in some opinions....

I do not have a good answer for that question.

Monkey

**Steve** · 10th October 2007, 03:28

Quote: (Originally Posted by Monkey)

some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2..

basically you hold the carriage up to your mouth and blow with your hand over the other side...

Everyone should be doing this. Lines 19 and 20 an your pre dive checklist.

http://www.customrebreathers.com/checklist.pdf

It is a bypass test, we aren't trying to blow the thing apart an a comensurate amout of pressure should be applied.

mempilot · 10th October 2007, 03:32

Quote: (Originally Posted by Steve)

Everyone should be doing this. Lines 19 and 20 an your pre dive checklist.

http://www.customrebreathers.com/checklist.pdf

It is a bypass test, we aren't trying to blow the thing apart an a comensurate amout of pressure should be applied.

That is the old checklist, which I use due to version, to check the water trap tube. That is not what we are talking about here and not valid for the majority of Megs out there. Blowing and sucking on that tube does not check the sensors or o-rings. It checks the check valve on the older Megs.

**Steve** · 10th October 2007, 03:48

Quote: (Originally Posted by mempilot)

That is the old checklist, which I use due to version, to check the water trap tube. That is not what we are talking about here and not valid for the majority of Megs out there. Blowing and sucking on that tube does not check the sensors or o-rings. It checks the check valve on the older Megs.

I believe you are mistaken. It does indeed assess the O rings, the water drain if fitted and the sensors.

Everyone should be doing this on every pre dive.

**wedivebc** · 10th October 2007, 04:17

Quote: (Originally Posted by mempilot)

When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact.

Thanks,

Eric

Official ISC meg checklist:

step 19 positive pressure test sensor carriage assembly (one-way water check valve)

step 20 negative pressure test sensor carriage assembly

These steps are very specific and should carried every pre-dive.

mempilot · 10th October 2007, 04:26

You are talking about two completely seperate things here. Some Megs don't even have the one-way water check valve, but that is another matter. What Monkey is talking about pertains to sealing off one end of the head with your hand and blowing through the other end of the head with your mouth to see if the o-ring or sensors have failed. That has nothing to do with the one-way water drain check valve test.

27th August 2007, 15:03	#1 (permalink)
Freak214 New Member Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: Jun 2005 Location: USA, Virginia Posts: 46	Failing +/- Sensor Carriage test Well its been just a little short of one year and my Meg finally had to sit a dive out... It was sad jumping in without it. About midway through a week of diving in the Bahamas my Meg started to fail the positive/negative sensor carriage assembly test. While troubleshooting the problem I removed each of the o2 sensors and found that I could blow through cell 2 and 3. Now, I have gone back and read the posts concerning this as a potential failure point but all I was able to locate were posts where this occurred with new cells or fairly new cells. Nothing about 11 month old cells Is this just one of the failure modes of the sensors or did I do something to bring about this issue? Thanks JohnL
(Online)

9th October 2007, 22:49	#2 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Failing +/- Sensor Carriage test When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact. Thanks, Eric __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
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10th October 2007, 02:56	#3 (permalink)
Monkey Supporting Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2006 Location: Lauderdale By The Sea Florida Posts: 400	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by mempilot) When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact. Thanks, Eric some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2.. basically you hold the carriage up to your mouth and blow with your hand over the other side...
(Online)

10th October 2007, 03:05	#4 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by Monkey) some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2.. basically you hold the carriage up to your mouth and blow with your hand over the other side... That's what I thought. Is this supported by ISC? Couldn't you actually be prematurely destroying your O2 sensor membranes by putting that kind of pressure on them? I've heard of people having pinholes in the membranes, saying they recognized the failure after doing this +/- sensor carriage test. Seems the test might be related to the failure? __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
(Offline)

10th October 2007, 03:15	#5 (permalink)
Monkey Supporting Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2006 Location: Lauderdale By The Sea Florida Posts: 400	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by mempilot) That's what I thought. Is this supported by ISC? Couldn't you actually be prematurely destroying your O2 sensor membranes by putting that kind of pressure on them? I've heard of people having pinholes in the membranes, saying they recognized the failure after doing this +/- sensor carriage test. Seems the test might be related to the failure? boy did this thread just ask for some people to throw in some opinions.... I do not have a good answer for that question. Monkey
(Online)

10th October 2007, 03:28	#6 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,100	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by Monkey) some trainers do a pressure test on the carriage... there is an o ring that can slip.. and pass CO2.. basically you hold the carriage up to your mouth and blow with your hand over the other side... Everyone should be doing this. Lines 19 and 20 an your pre dive checklist. http://www.customrebreathers.com/checklist.pdf It is a bypass test, we aren't trying to blow the thing apart an a comensurate amout of pressure should be applied. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
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10th October 2007, 03:32	#7 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by Steve) Everyone should be doing this. Lines 19 and 20 an your pre dive checklist. http://www.customrebreathers.com/checklist.pdf It is a bypass test, we aren't trying to blow the thing apart an a comensurate amout of pressure should be applied. That is the old checklist, which I use due to version, to check the water trap tube. That is not what we are talking about here and not valid for the majority of Megs out there. Blowing and sucking on that tube does not check the sensors or o-rings. It checks the check valve on the older Megs. __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
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10th October 2007, 03:48	#8 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,100	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by mempilot) That is the old checklist, which I use due to version, to check the water trap tube. That is not what we are talking about here and not valid for the majority of Megs out there. Blowing and sucking on that tube does not check the sensors or o-rings. It checks the check valve on the older Megs. I believe you are mistaken. It does indeed assess the O rings, the water drain if fitted and the sensors. Everyone should be doing this on every pre dive. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
(Offline)

10th October 2007, 04:17	#9 (permalink)
wedivebc FIGJAM 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: 1,410	Re: Failing +/- Sensor Carriage test Quote: (Originally Posted by mempilot) When you say it failed the +/- sensor carriage test, could you explain what you mean or are talking about? My ISC checklist does not have anything related to what I think you mean other than ensuring the o-rings are intact. Thanks, Eric Official ISC meg checklist: step 19 positive pressure test sensor carriage assembly (one-way water check valve) step 20 negative pressure test sensor carriage assembly These steps are very specific and should carried every pre-dive. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die Last edited by wedivebc : 10th October 2007 at 04:19.
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10th October 2007, 04:26	#10 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Failing +/- Sensor Carriage test You are talking about two completely seperate things here. Some Megs don't even have the one-way water check valve, but that is another matter. What Monkey is talking about pertains to sealing off one end of the head with your hand and blowing through the other end of the head with your mouth to see if the o-ring or sensors have failed. That has nothing to do with the one-way water drain check valve test. __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
(Offline)

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