O2 sensors

A Place for Discussions On All The Various mCCRs, eCCRs, SCRs & Diving Profiles.

Postby Hoppy » Tue Feb 05, 2008 12:56 am

Im AM NOT a RB expert. Far from it. So take my comments with a grain of salt.

On home-build rebreathers. I seem to recall Pete referring to his home-build RB as 'the widow-maker'. It may have been tongue-in-cheek, or not :lol:

A RB is a task-orientated device. If you dont need it (or cant justify it), then is using one worth the greater risks involved?? That is just a question Im throwing in there for interest. Im not personally of the variety of diver who thinks RB divers are all going to die, I just dont personally feel the time/money/risk/requirements equation works for me. If it does for you, cool.

RBs do have some definite advantages in some applications, especially photography, as well as others like cheap mix (compared to oc mix), easier to support expeditions, the warmth factor, (and many others). I can also understand the allure, I like interesting shiny toys too :)

I believe mCCR's with constant mass flow have quite stable loops under normal workloads. But even given that, I dont think I would ever consider diving with 1 faulty PPO2 sensor out of 3. And I dont know if I would consider less than 3 to really be a viable option either.

For starters, if one is dodgy, its quite possible that one of the others is suspect too, if they are all the same age and run-time. Secondly, when you only have 2 sensors, you lose your 'voting logic'. Which of the two is correct??

Yes, if you have the capability, you can run diluent over the sensors and make a call as to which sensor to run off of. But in a task-loaded situation, are you going to read the right one? This is the sort of 'little thing' which can turn into a 'big thing' if the brown stuff hits the fan. IMHO, sweat the little things, and the big ones just tend to sort themselves out.

I guess to me that this sort of thing is more of a discipline question than anything else. A lack of discipline, and taking short-cuts, with RB's appears to be a really good way of needlessly putting yourself in harms way. If you take are willing to dive with known failures, then what's the problem with a missed pre-breathe? And from there on down the slippery slope of 'she'll be right'.

Packhorse. That was a generalized comment, NOT aimed at you, or in any way implying that you are un-disciplined, more just me generally musing and being philosophical, as I am often am at 1am (especially if Ive had a bourban or 2) :)
Hoppy
Member
 
Posts: 201
Joined: Thu Feb 22, 2007 2:33 am
Location: Auckland, NZ

Postby Packhorse » Tue Feb 05, 2008 8:54 am

Its the "voting logic" that I dont like about using 3 sensors. If 1 reads diffrent to the others it would to to easy to assume the one was faulty as opposed to verifing the loop PPO with a flush.
I guess what I am saying is that having 2 sensors forces you to be a bit more conservitive and pay more attention to the details.
Packhorse
 

Postby Andy » Tue Feb 05, 2008 10:03 am

Hoppy wrote:A RB is a task-orientated device. If you dont need it (or cant justify it), then is using one worth the greater risks involved?? That is just a question Im throwing in there for interest.


A valid point, Hoppy. I've recently made the decision to delay my buying a breather for at least another year. None of the units on the market are perfect (for what I want) and whilst they can be dived safely, I'm not sure the extra risks that are involved are justified given theat I'd be compromising on the functionality of the unit.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Postby Packhorse » Tue Feb 05, 2008 12:18 pm

Andy wrote: None of the units on the market are perfect (for what I want)

Care to eleborate?
What is it you want that they lack?
Perhaps you could join me any build your own. :lol:
There is a IDA 72 on TM at the mo
Packhorse
 

Postby plumb bob » Tue Feb 05, 2008 12:47 pm

Hoppy wrote:I like interesting shiny toys too :)


You know this is starting to become the battle cry of this forum..

:lol: :lol:
Account deactivated by administrator
User avatar
plumb bob
Banned
 
Posts: 398
Joined: Mon May 28, 2007 4:16 pm
Location: Christchurch

Postby Andy » Tue Feb 05, 2008 3:47 pm

Packhorse wrote:Care to eleborate?
What is it you want that they lack?


I'm having big bucket issues, namely the mCCR vs eCCR debate.

I like the simplicity of the mCCR, provided that there's a VR uplink to give live deco information. However, even with a VR and a HUD, the need to constantly monitor pp02 is a concern. I take a lot of photos, so would be prone to having pp02 creep. Of the mCCRs, the choice is a classic KISS, a RevoII or a Copis Meg. The Meg is the easiest to pick holes at - having the O2 injection on the inhale counterlung just worries me. I can see the benefit of having this on an eCCR, as the manual add could be used to increase pp02 very quickly in case of CO2 problems - but I don't like a leaky valve. The RevoII is a tidy unit, well designed and some nice feature - I don't like the tap control on the RevoDreams, and it needs more of a pedigree before I commit. The KISS is probably the strongest unit - I don't like the original triple ppO2 display, having to open it to calibrate doesn't make sense. If you go for the triple O2 block, HUD and display and C2R ppO2 pendant then it gets over this (at a cost), which just leaves some of the criticisms of the breathing loop/scrubber connectors which are supposedly not suitable for wreck diving.


From the eCCR stable, I could go APECS Meg, but figure that if you're going to go eCCR you might as well go with an onboard computer etc. This really just leaves the Vision - the problem that I have is that water and electronics really don't mix, and the more I dive with Inspo divers the more I see them all have problems. One argument given for buying an Inspo is "there's lots of them around now, so when something goes wrong it's easy to borrow a piece of someone else's unit"..... and boy, do there seem to be problems quite often.

The eCCR version of the RevoII is coming out next month, and once it's got some pedigree then it's going to be worth looking at, providing the Shearwaters going on it replace the tap control RevDreams.

Other than that, the only thing I'd consider would be retro-fitting a classic Inspo with a Hammerhead - I really like what they've done in controlling water issues in the head, particularly moving as mucha s possible into the wrist units. If I then fitted a KISS BOV, shifted the counterlungs onto the back, strengthed the case and got the weight distribution right.... I'd have a unit I'd consider diving - also, by coincidence, identical to SilentSolutions unit, I think?

Perhaps you could join me any build your own. :lol:
There is a IDA 72 on TM at the mo


I don't have the patience, and a list of DIY projects always grows longer.....
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Postby petemes » Wed Feb 06, 2008 10:11 am

Interesting topic of discussion and obviously something that is very close to home for me.

I used to think that every person should have a breather and the future was seeing dive stores with breathers on the shelves alongside the open circuit gear. But the more I dived a breather the more it became apparent that rebreathers are NOT for most divers. Put quite simply - most divers just dont have the discipline needed to safely operate a breather and not just that, but also to constantly have the discipline over time too.

Rebreathers DO kill people and WILL kill people. They have taken the lives of very accomplished divers who slipped up once which cost them their life. Plain and simple you really need to have specific objectives to use a braether. .

Hoppy, nice post. some very valid points and comments.

Now building your own (or modifying a) breather is again a completely different story. The danger associated with messing around with something that is not right could be fatal in itself.

Most of the time it is people who dont have the money who start to try and convert a shopping trolley into a formula 1. This is becoming more dangerous as time goes by. Simply because there is much more information in the net about pimping some submarine escape breather into a "functioning" expedition breather and the "home builders" dont really understand the acute fundamentals in rebreather design. They simply purchase pimped out pieces of kit from those who have done all the testing and managed to stay alive because of their infinate knowledge of breathers because they "Designed the items"

Again this really concerns me. Having already been down this road myself converting a Dolphin into a fully manual CCR I manufactured every piece of kit myself (had it made by a fitter to my spec) Before I started messing arround with the unit I did a full course in the dolphin first and completed about 60-80 hours on my unit to understand more about breather diving on a functioning proven unit.

So to paraphrase

You can read all about diving on breathers, design and build as much as you like but without getting into the water and safely gaining REAL dive time in these specialized pieces of gear you are pissing against a gale fore wind (with your life)

The best way to gain this theoretical and inwater experience is to get trained on a proven unit. That way you arent playing with your life every time you are getting into the water. Wouldnt that be the safest way?

Noone can tell anyone what to do in life, hell you can do whatever the hell you like. But you have to have the right reasons for doing what you are doing, and most of the time they arent good enough to risk your personal
welfare on. If you want to dive breathers then for god sake get one that is has been proven by proper testing and man hours. Doesnt matter which breather you get. But all I am saying is REALLY know what you are doing before you put your life at massive risk. If you cant afford it - then save! If you dont want to pay the money for specialized gear then you arent committed enough for rebreather diving. If you like making things - then make model aeroplanes. They wont kill you if you do a sh1t job!


Respectfully yours

Pete
"A little less talk a little more action" Elvis Presley
User avatar
petemes
Site Sponsor
 
Posts: 550
Joined: Sun Feb 18, 2007 2:52 pm
Location: Auckland

Postby petemes » Wed Feb 06, 2008 10:27 am

Hi Andy,

Valid comments too. If you buy a rebreather then EXPECT a lot of maintenance.

Electronics and salt water dont mix but most of the time problems in the electronics are caught in the start up diagnostic. There is so much to look out for ,cells, sorb, proper assembly, etc etc again that is why more expertise and dedication is needed.

I have very strong views on manual "leaky valve" units, some say its the best thing, some say you dont have any control as to what is going into the loop.

Just let it be said, what ever breather is chosen by anyone, expect that you will lose diving days because of dodgy cells, and expext to send the electronics back for service.
There is no ultimate breather out there 'by now never have to get it fixed"

You just need to pick one that will do what you want it to do and go with it.


With over 9000 inspos, maybe 600 megs,2000 odd Kiss units round the world, and a handful of Revo's For me it isnt a difficult choice to see what company has the best back up and service and the most amount of R&D dedicated to making the breather better, safer and less proned to malfunction. But then some conspiricy theorists think I only say that because I sell and dive and train on the Inspo (ever wondered why?)

Pete




Andy wrote:
Packhorse wrote:Care to eleborate?
What is it you want that they lack?


I'm having big bucket issues, namely the mCCR vs eCCR debate.

I like the simplicity of the mCCR, provided that there's a VR uplink to give live deco information. However, even with a VR and a HUD, the need to constantly monitor pp02 is a concern. I take a lot of photos, so would be prone to having pp02 creep. Of the mCCRs, the choice is a classic KISS, a RevoII or a Copis Meg. The Meg is the easiest to pick holes at - having the O2 injection on the inhale counterlung just worries me. I can see the benefit of having this on an eCCR, as the manual add could be used to increase pp02 very quickly in case of CO2 problems - but I don't like a leaky valve. The RevoII is a tidy unit, well designed and some nice feature - I don't like the tap control on the RevoDreams, and it needs more of a pedigree before I commit. The KISS is probably the strongest unit - I don't like the original triple ppO2 display, having to open it to calibrate doesn't make sense. If you go for the triple O2 block, HUD and display and C2R ppO2 pendant then it gets over this (at a cost), which just leaves some of the criticisms of the breathing loop/scrubber connectors which are supposedly not suitable for wreck diving.


From the eCCR stable, I could go APECS Meg, but figure that if you're going to go eCCR you might as well go with an onboard computer etc. This really just leaves the Vision - the problem that I have is that water and electronics really don't mix, and the more I dive with Inspo divers the more I see them all have problems. One argument given for buying an Inspo is "there's lots of them around now, so when something goes wrong it's easy to borrow a piece of someone else's unit"..... and boy, do there seem to be problems quite often.

The eCCR version of the RevoII is coming out next month, and once it's got some pedigree then it's going to be worth looking at, providing the Shearwaters going on it replace the tap control RevDreams.

Other than that, the only thing I'd consider would be retro-fitting a classic Inspo with a Hammerhead - I really like what they've done in controlling water issues in the head, particularly moving as mucha s possible into the wrist units. If I then fitted a KISS BOV, shifted the counterlungs onto the back, strengthed the case and got the weight distribution right.... I'd have a unit I'd consider diving - also, by coincidence, identical to SilentSolutions unit, I think?

Perhaps you could join me any build your own. :lol:
There is a IDA 72 on TM at the mo


I don't have the patience, and a list of DIY projects always grows longer.....
"A little less talk a little more action" Elvis Presley
User avatar
petemes
Site Sponsor
 
Posts: 550
Joined: Sun Feb 18, 2007 2:52 pm
Location: Auckland

Postby Andy » Wed Feb 06, 2008 5:27 pm

petemes wrote:With over 9000 inspos, maybe 600 megs,2000 odd Kiss units round the world, and a handful of Revo's For me it isnt a difficult choice to see what company has the best back up and service and the most amount of R&D dedicated to making the breather better, safer and less proned to malfunction. But then some conspiricy theorists think I only say that because I sell and dive and train on the Inspo (ever wondered why?)



The inspo definitely has the pedigree, Pete. In reality, it's probably the only eCCR I'd consider - I think the RevoII has some nice features, but I'd want to see a lot more units in the water before committing to it.... and that's going to take a while.

The classic with HH looks like the closest to what I'd want right now - taking the electronics into the handsets is such a great idea, it must result in less condensation in the head which to my mind makes it a bit more robust?

The other side of the coin at the moment is that 90% of my diving is with the other half, and she's on single tank with normally a maximum dive time of around 60 minutes. That's the biggest reason why a breather is not the right choice for me - the maintainance and the overhead would become a hassle, and put me off diving it.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Postby petemes » Wed Feb 06, 2008 10:30 pm

Hey mate,

Having seen the Revo at Oztek it really is innovative. Proof will be in how it is manufactured and supported. Also how it performs in the field. I am also looking cloesly at Col's Eagle from Ozz.

Must reinstate the week ending drinks!!

Pete


Andy wrote:
petemes wrote:With over 9000 inspos, maybe 600 megs,2000 odd Kiss units round the world, and a handful of Revo's For me it isnt a difficult choice to see what company has the best back up and service and the most amount of R&D dedicated to making the breather better, safer and less proned to malfunction. But then some conspiricy theorists think I only say that because I sell and dive and train on the Inspo (ever wondered why?)



The inspo definitely has the pedigree, Pete. In reality, it's probably the only eCCR I'd consider - I think the RevoII has some nice features, but I'd want to see a lot more units in the water before committing to it.... and that's going to take a while.

The classic with HH looks like the closest to what I'd want right now - taking the electronics into the handsets is such a great idea, it must result in less condensation in the head which to my mind makes it a bit more robust?

The other side of the coin at the moment is that 90% of my diving is with the other half, and she's on single tank with normally a maximum dive time of around 60 minutes. That's the biggest reason why a breather is not the right choice for me - the maintainance and the overhead would become a hassle, and put me off diving it.
"A little less talk a little more action" Elvis Presley
User avatar
petemes
Site Sponsor
 
Posts: 550
Joined: Sun Feb 18, 2007 2:52 pm
Location: Auckland

Postby Andy » Thu Feb 07, 2008 8:45 am

petemes wrote:Must reinstate the week ending drinks!!



Yes! Could do Friday at the C&B for a quick one... will call you later.
Andy
Serial Poster
 
Posts: 4628
Joined: Thu Feb 01, 2007 1:29 pm
Location: Auckland

Postby Hoppy » Thu Feb 07, 2008 10:59 pm

Andy wrote:
petemes wrote:Must reinstate the week ending drinks!!

Yes! Could do Friday at the C&B for a quick one... will call you later.

Let me know if you feel like company. I havent done a DiveHQ GL drinkies for ages (like 5 or 6 years). Would be good to catch up.
Hoppy
Member
 
Posts: 201
Joined: Thu Feb 22, 2007 2:33 am
Location: Auckland, NZ

Postby petemes » Thu Feb 07, 2008 11:32 pm

What say tomorrow.?

Hoppy wrote:
Andy wrote:
petemes wrote:Must reinstate the week ending drinks!!

Yes! Could do Friday at the C&B for a quick one... will call you later.

Let me know if you feel like company. I havent done a DiveHQ GL drinkies for ages (like 5 or 6 years). Would be good to catch up.
"A little less talk a little more action" Elvis Presley
User avatar
petemes
Site Sponsor
 
Posts: 550
Joined: Sun Feb 18, 2007 2:52 pm
Location: Auckland

Postby Hoppy » Fri Feb 08, 2008 4:11 pm

petemes wrote:
Hoppy wrote:
Andy wrote:
petemes wrote:Must reinstate the week ending drinks!!

Yes! Could do Friday at the C&B for a quick one... will call you later.

Let me know if you feel like company. I havent done a DiveHQ GL drinkies for ages (like 5 or 6 years). Would be good to catch up.

What say tomorrow.?

Could be a plot? What sort of time? Would have to pass it past the kitchen strife.
Hoppy
Member
 
Posts: 201
Joined: Thu Feb 22, 2007 2:33 am
Location: Auckland, NZ

Previous

Return to Rebreather Diving

Who is online

Users browsing this forum: No registered users and 1 guest

cron