RBW Traitor

mempilot · 22nd March 2008, 23:32

Quote: (Originally Posted by dz3866)

after reading Rons last post, and seeing that Alex bought a used Meg and dove it without any training on that unit ,really puts him in a diffrent light with me, how can you preach safe reabreathers and safe rebreather diving and then break one of the biggest rules.

To add to this, they were flogging the Meg for shutting down inadvertantly. After much debate about the quality of the on/off switches in the head, they realized that the unit had dirt/debris in the channel that the switch detents into. Not only was there a misunderstanding of how the switches worked because there was no training completed, whoever owned the unit wasn't properly maintaining the unit. This is not a design flaw. I don't know about others, but one could eat off the inside of my unit.

SeaBass · 23rd March 2008, 00:16

Quote: (Originally Posted by dz3866)

after reading Rons last post, and seeing that Alex bought a used Meg and dove it without any training on that unit ,really puts him in a diffrent light with me, how can you preach safe reabreathers and safe rebreather diving and then break one of the biggest rules.

Good point.

When you purchase a new Meg (or get ISC's approval to use one) you sign as a Liability Waiver. Some view this as a "cover your assets" document but for the user it also is a very sobering read stating the inherent un-reliability of ANY type of equipment used in a Marine environment as well as the commitment by you to be carefully trained and responsible for it's safe use. Believe me I know I just signed one.

Alex, what measures and or commitment have you taken to make sure you were/are using this rebreather safely. (Big deal was made about this by many on this forum when Dave S started diving a rEvo before he was trained *even though* HE had Pauls approval.) I am sure you are no dummy and have familiarity with many different units.

But:

Have you ever allowed anyone else to borrow or dive your Meg or any other rebreather you owned without them being properly trained on it by a factory authorized trainer? If that were the case, who would have been responsible if something happened to them?

If you are willing to go on the stand as an expert witness (I have) expect to have your credibility brought into question by being asked these type of questions.

Thom

***jradomski*** · 23rd March 2008, 08:11

Quote: (Originally Posted by RonMicjan)

1. The O2 sensors must be as close as possible to the injector, otherwise the PPO2 control loop is the same as having a set of slow response sensors.

I dont know why this is so, it hasnt been explained, however, I find that there is no problem with my unit keeping SP, nor have there been any complaints and according to all testing (HSE for CE cert) so far, there is no problem. note, the new units have a adaptive alogrithm that is better at keeping up sp during fast ascents,Alex was diving an old unit he picked up second hand and was diving with no training on the unit.

I have to agree with Alex here.. Putting o2 injection before the stack slows down response time.. Its a design decision whether you want a "mixed" value or an immediate value.. Both have pluses and minuses.. The larger the volume before the sensors the slower the response time.. If you put the sensors at the injection point, you might not actually get to the setpoint unless you implement a full PID controller, but that has its own issue.. If you put it well before the sensors, you can overshoot the sp because you can get multiple injections if the diver has a slow respiratory rate.. I don't see it as a true manufacture falt, but a choice with positives and negatives.. I personally would rather have it near the sensors..

Quote:

2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass.

There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit

While in practice there shouldn't be a problem, I have seen sensors fall apart.. I had one fall apart on my inspiration and it was fine before the start of the dive.. No big deal here but if it was need to prevent bypass there could be an issue.. I will grant is statistically very low, but there is no way a diver would know it fell apart until they got a co2 hit... The sensor body and the checmical chamber has a very poor bond.. This is one point I have been asking Kevin to change on the HH CCR.. This arrangement started on the CIS as far as I know..

Quote:

8. User replaceable primary cells have no role in running an unstable life support system
Are you suggesting rechargables? Why is it unstable? Use the checklist, monitor the battery voltage, dont dive with low batteries, if one side fails, end the dive on the other. Thats why there is a secondary.

I would prefer to see secondary cells myself (specifc batch tested rechargable cells are much easier to characterize and you can really get meaningful life left measurement.. There are too many variations (in both batch and by manufacturer) for primary (no rechargeable) cells.

Quote:

10. No auto turn on. It can be dived easily with the unit turned off if someone is dumb enough, and they may not have enough time on hitting the water to realise what they have done if the sun is bright enough to obscure the HUD.

Design decision, you must open the head and turn the unit on prior to donning it. If you are soo stupid to turn the unit on before you strap it on, you are too stupid to not look at the PO2 before you put the loop in your mouth, checked the HUD, looked at the handsets??...sorry, no sympathy there, you should not be a CCR diver, or any diver for that matter.

This is one point I am a strong supporter of... Wetswitches are an easy option, although they do have some negatives.. I would prefer to see both wetswitch activation and continual monitoring of the loop.. if it goes below ambient pressure multiplied by air, oxygen should be injected (this allows for sleep at altitude)...

I think a 2 pronged check is a good idea.. If the ws threshold is reached turn the unit on, if not periodically sample the po2.. this way there is no single pint of failure.. There have definately been deaths on rbs prevented if a WS was implemented.. A third level of protection could be added by checking the pressure as well.. so you would need 3 failures for someone submerging or 2 if someone was on the surface... This is something thats easy to implement and I feel should be mandatory on all rebreathers..

I agree a prebreath is necessary but people do stupid things, but I don;t feel they should die because of a brain fart..

AD_ward9 · 23rd March 2008, 11:53

Quote: (Originally Posted by SeaBass)

Alex, what measures and or commitment have you taken to make sure you were/are using this rebreather safely. (Big deal was made about this by many on this forum when Dave S started diving a rEvo before he was trained *even though* HE had Pauls approval.) I am sure you are no dummy and have familiarity with many different units.

To answer your questions:

Safety measures taken:

1. I fitted a three cell independent PPO2 monitor before using it.

2. I had a buddy, it turned out a very good one.

3. We got in the Meg to understand what the failure modes were, simply because the accident rate was high and if there was a lesson there, we do not want to find it out the hard way (i.e. accidents on things we design). I did not get it in for recreational diving.

4. We put it on a breathing machine first.

I emphasise this is different from doing a training course: we test a unit as it comes. For example, if the unit does not have positions for integral weights, I test dive it with a normal weight belt and see my (abysmal) attitude in the water throughout a dive - it tells me why divers are putting weights onto tanks with cam bands.

A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't. Also the level of training is very variable, and test dives are about finding out what divers can foul up on.

Alex

AD_ward9 · 23rd March 2008, 11:57

Quote: (Originally Posted by mempilot)

To add to this, they were flogging the Meg for shutting down inadvertantly. After much debate about the quality of the on/off switches in the head, they realized that the unit had dirt/debris in the channel that the switch detents into. Not only was there a misunderstanding of how the switches worked because there was no training completed, whoever owned the unit wasn't properly maintaining the unit. This is not a design flaw. I don't know about others, but one could eat off the inside of my unit.

I differ on the design flaw. It is a design flaw as it is a single common mode of failure. Just fitting a battery compartment in opposite direction would fix this.

Remember we tested the unit as it was received, from an instructor. We did not clean it, or fix it. We did not dirty it either.

Our purpose is to understand fault modes, and we found one we did not expect. There is nothing in any manual I have seen about cleaning out those springs (that are not visible even).

This is highlighted very well by Ron: he lists why things should be OK, but the fact is they are not. For example, there can be insufficient O2 injected on an uncontrolled ascent - Ron's answer is that it meets CE test by the HSE. The HSE are generally involved after a fatal accident: ANSTI would be the people to go to get a test done. The CE test Ron refers to is I assume the EN14143:2003 test: this tests at one breathing rate only and with only a slow ascent rate - it does not test for a panicked diver in an uncontrolled ascent. After I reported my finding that the PPO2 setpoint fell to 0.36, another Rebreather World user reported they had it become hypoxic on the same set point. There is an issue here, and the response is not to explain why it is OK, the proper response is to find the cause of this confirmed problem and fix it, before it kills someone. Most of the rest of Ron's comments take the same vein.

Alex

***EBT*** · 23rd March 2008, 11:59

Quote: (Originally Posted by AD_ward9)

A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't.

With respect, is that the manufacturers fault? Its a whole other debate though, so I'll leave the comment at that.

AD_ward9 · 23rd March 2008, 13:07

Quote: (Originally Posted by EBT)

With respect, is that the manufacturers fault? Its a whole other debate though, so I'll leave the comment at that.

According to EN61508 it is: the manufacturer must manage the entire product life cycle, not just design and sell it.

There are two ways to handle this:

1. Do what Steam Machines did with the Prism and require people to sell it back before it is sold on, so they can check the buyer is trained and the unit is not faulty. Or how CCR Ltd manage things, with a timer counting down a year to factory service.

2. Eliminate failure modes that would cause an experienced eCCR user to die on their unit.

Doing (2) is probably a good idea anyway.

Alex

diverklondike · 23rd March 2008, 13:29

Quote: (Originally Posted by AD_ward9)

A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't.

Alex

Alex,

You do not have the right to speak for what a manufacture may and or not expect and or require as it applies to any type of training on their units. If and when you deliver a unit and or a unit is delivered with your electronics then you can make your own determination. Is that what your saying here? That if and when your electronics are delivered on a unit there will be no requirement for cross over training if you have an CCR certification?

As it applies to the HH CCR, I completed a cross over course for the unit reguardless of the hundreds of hours that I already have with the electronics. It was part of the terms underwhich I purchased the unit from the MFG. I can also say that I did find the class valuable.

The only loose area in this equation in my mind is the second hand marketplace. That is obviously totally unregulated. I am not suggesting at all that there should be an control but only that it isn't.

The other partially controling party here is the dive operator that "should" be asking for proof of certification but that's another story...

Dive Safe....

Mark

**kevin stone** · 23rd March 2008, 13:53

Quote: (Originally Posted by RonMicjan)

We want to hear about the ones you determined were diver error, because on your website you state “Nobody dies on a rebreather from user error, unless they take the mouthpiece out of their mouth and do not replace it with something.” as your objective. So in your opinion, a CCR should be completly tolerant of anything a diver does to it including no/poor maintainance.

well here is your list on failure points for the meg, including the one that states "its too heavy" along with my previous arguments on said points, how well does this jive with the above statement, especially since you have never had day one of training on the meg and a bunch of your critisisms are addressed by the checklist (which apparantly you have never seen) and training.
Now of course mike is going to accuse me of sleeping with my meg and showing favoritism, but folks, please keep in mind, I am an instructor on the KISS and Meg, not anything else, so of course I am only capable of defending something I actually know something about, not like alex who has never been trained or used a checklist on the meg.

Ok, I found the original list of Meg supposed faults and have added comments below from a Meg diver/instructor point of view. As kevin has stated, I believe ultimate safety is in the hands of the responsible diver, although the designer should do the best possible job, end safety is in the divers hands. All of alex's notes in red.

1. The O2 sensors must be as close as possible to the injector, otherwise the PPO2 control loop is the same as having a set of slow response sensors.

I dont know why this is so, it hasnt been explained, however, I find that there is no problem with my unit keeping SP, nor have there been any complaints and according to all testing (HSE for CE cert) so far, there is no problem. note, the new units have a adaptive alogrithm that is better at keeping up sp during fast ascents,Alex was diving an old unit he picked up second hand and was diving with no training on the unit.

2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass.

There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit

3. It should not allow users to set a PPO2 set point below 0.7: it allows 0.4, which given its poor setpoint control, is an issue.
Easy, dont set your rig on 0.4 if you dont think its a good idea, I never use that setting myself. There is a manual setting of .20 that allows the unit to be on w/o the solenoid firing away, nice to have for bench work, but not a diving setting. I would like to see this setting disabled when the unit is under water, maybe next gen. not a bad point and I have asked ISC to make the software change myself

4. It needs to meet EN61508 SIL 3 or 4, but does not meet any SIL level at all. This requires major redesign. Do not trust the electronics until then: not to update the display, or the HUD or anything else. Incidentally, a KISS PPO2 monitor would meet SIL 3.

I do not know these specifications, so cannot argue the point. However, the meg has a secondary display that is passive, similar to the KISS unit, so if the KISS units meet sil3, then the meg does too. The SP software was written by a ex boeing embedded software designer (Steve) and we tend to do what we know, so why wouldnt steve design to the level required for jets, since that is where he came from? why not ask steve? What major redesign do you suggest? Specifics, not generalizations.

5. The unit can definitely switch itself off underwater without warning. HUD went off. Batteries were 6.9V, 6.0V under load.

Discussed ad nauseum, but no real data, and this is the first report of a meg switching off on its own, unless the diver was not replacing batteries in a timely fashion. We know Alex was reading voltage off the primary when the problem was with the secondary. (based on a previous discussion)User error due to lack of training.

6. No warning buzzer, at least on the ISC handsets on the unit here.

Design choice, whats wrong with the diver watching the HUD and taking responsibliity for thier own actions. I hate buzzers, beepers etc, wouldnt have one on a unit I own.

7. Needs a decent backlight on the handsets here - I know the Meg has too many different handsets, which adds to the problem.

Im guessing that this is why the unit shut off, batteries were low, no backlight, unit shut off. reason: No training, not using checklist, ignorant of safety features like low battery warnings. Too many different handsets???? there has been ONE since the introduction of the unit. Not including the shearwater system. The backlights work just fine, I have never heard anyone complain about them.

8. User replaceable primary cells have no role in running an unstable life support system
Are you suggesting rechargables? Why is it unstable? Use the checklist, monitor the battery voltage, dont dive with low batteries, if one side fails, end the dive on the other. Thats why there is a secondary.

9. PPO2 setting should be automatic near surface, to increase PPO2: diver can use a dangerously low PPO2 set point.
Part of the pre jump in the water is for the diver to check setting and then again when reaching the target depth. There is a HUD, and handsets, and the Meg if turned on, will not allow a loop SP of under 0.20. We expect OC divers to monitor thier tank pressure...should we expect less of better trained CCR divers?

10. No auto turn on. It can be dived easily with the unit turned off if someone is dumb enough, and they may not have enough time on hitting the water to realise what they have done if the sun is bright enough to obscure the HUD.

Design decision, you must open the head and turn the unit on prior to donning it. If you are soo stupid to turn the unit on before you strap it on, you are too stupid to not look at the PO2 before you put the loop in your mouth, checked the HUD, looked at the handsets??...sorry, no sympathy there, you should not be a CCR diver, or any diver for that matter.

11. HUD is not always visible, depending on the mask.

DUH, buy the right mask or adjust the position of the HUD. Do you drive with cardboard over your speedometer in your car and then complain to the judge that the speeding ticket was undeserved?

12. Weight is excessive, and fitted up exceeds 25kg CE limit for lifting equipment (i.e. gives you back ache). Needs pouches at the top to improve the trim underwater. They weight is enough to hinder recovery in some cases.
OMG, If you cant handle the weight of the unit, DONT BUY ONE! or get a mini, or stay on the porch. the unit ends up neutral underwater, there is plenty of room to stash trim weights at the top of the counterlungs attached to the D ring there. I suppose we need to ban all doubles because CE says they are too heavy? Sorry, this one just slays me, Patti, at 125lbs can dive a mini meg with 2 stages, a student of mine who weighs 145 dives a full size unit.

13. Hoses have Thiram in them (a toxic softener in the EPDM), and only just withstand the 25kg pull test (they do not when old).

Dont know what Thiram is, but I have hung my own body from my assembled loop, plastic bits and all and done a pullup. Im over 100kilos. More BS.

14. Hoses need weighting: they are long and float too far away from the diver. In a dry suit getting them back involves a move that some divers would not manage.

Try attending training, we show you how to recover hoses in 3 different methods and I have never had a student, drysuit or not, be unable to do any of the three. the loop can not get away from the diver like a BMCL unit can, this is just plain ignorance of the unit and lack of training, not to mention nit picking. Also, if you had trouble with finding the hoses, perhaps your instructor didnt do a very good job of fitting the unit to you...oh, wait, you didnt have an instructor did you?

15. There is no mouth strap to retain the mouthpiece with an unconcious diver. This is in EN14143 (I know, it is not applied, but safety standards should be applied whereever a unit is sold, when they represent good practice).
If a diver wants a strap, they can go buy one, silly critique.

16. The solenoid can freeze shut too easily, and without warning.
Sure there is a warning, Watch your PO2, thats what the HUD is for, listen for the solenoid. I had an instructor pull my O2 feed line, I heard the difference in the sound. Run the unit like you were instructed to manually with the electronics as a backup, you will find the bad solenoid on the next predive, but probably sooner. All part of the training and checklist use

17. The solenoid has excessive amounts of combustible material in it.
Right, stainless steel can burn with enough heat and pure O2 around at high pressure.

18. There can be insufficient O2 injection on an uncontrolled ascent.

not according to the CE testing done by HSE, which it has passed and the new adaptable injection algorithm.

19. Handsets hard to read: PPO2 values are too small, with too low a contrast, on the handsets fitted to the unit here.

Opinion. If you cannot read the displays, buy a correcting mask or dont buy the meg, certainly not a failure point, again with the speedometer and ticket argument.

20. Counterlungs can come loose because harness is not fully integrated (people can change it), or they can float away from the diver, causing a large WOB increase.
Yes and fastex buckles break continously, thats why everyone in the industry uses them. Design decision, personally I prefer to be able to remove my CL and dunk them in a cleaning solution, certainly not a safety issue. and the nylon harness can be eaten by a shark too and if the unit floats away, what do you do then.

OK, so out of 20 comments, one or maybe two are relevant and could be improved upon but all are neglegible if the diver is doing the checklist and diving like they were trained.

Alex, why dont you go buy a brand new unit, take it in to an independent tester and have a full CE test done on it, please forward the results to us, enquiring minds want to know. Remember that Leon wont sell you a unit w/o training so let me know if you would like to hire me for that.

The above was pulled from an earlier post on Rebreather World, after Alex posted his failure point list on the meg, this is a distinct contrast to his statement
"If a manufacturer does not have any single points of failure in a eCCR, and the overall product has been designed well, the chance of my finding any fault will be very low indeed"

Now, I did say I was done posting, but hypocrisy brought me back to the fold.

There have been some interesting points, great discussions and a lot of fun going on here but I think I need to apologize for using the word Traitor in the title, as that brought a little too much passion into the argument. It is quite possible that Alex does have all of our best interest and our safety in mind, but I still have some reservations on that subject, time will tell, as will Alex bringing a perfect CCR to market. Seeing the list would be nice too, eh mempilot?

So what was the ISC response to any of these items when they were brought up?
I think that is the real issue, all manufactures have issues it's how they are addressed when identified that I think is the main concern.
Did ISC have a recall?
Send a letter?

Not to pick on any unit, just wondering how another manufacturer delt with issues.
I dont dive a Meg so I have no comment.

Thanks
Kevin

divetheworld · 23rd March 2008, 14:44

Quote: (Originally Posted by RonMicjan)

2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass.

There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit

Constructively speaking;
I'm not sure that there hasnt been some confusion in the difference between the WOB and the differential pressure accros the scrubber. The WOB is a factor of all the components including the counterlungs and loop, the differential pressure would be measured between the inhale and exhale port of the scrubber.
To illustrate my point, assemble a scrubber and breathe off it through one port, pendulum fashion. You will be unpleasanlty surprised at the WOB through the stack alone. This WOB is dissapated through the system when it is integrated into a loop.
Although we have absolutely no empirical data relating to the actual differential pressure that is encountered when in use, it would be an interesting experiement to put a differential pressure monitor accross the inhale and exhale ports to determine the effect on the cells when breathed.
John and I have been working on some interesting projects that have parallels to this particular problem and have considered carrying out this test.
the WOB for a complete unit is related to the sum of its parts. To analyse each component means we can target individual components to reduce the overall WOB for a specific unit.

Brent

22nd March 2008, 23:32	#231 (permalink)
mempilot Eric Stadtmueller Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,717	Re: RBW Traitor Quote: (Originally Posted by dz3866) after reading Rons last post, and seeing that Alex bought a used Meg and dove it without any training on that unit ,really puts him in a diffrent light with me, how can you preach safe reabreathers and safe rebreather diving and then break one of the biggest rules. To add to this, they were flogging the Meg for shutting down inadvertantly. After much debate about the quality of the on/off switches in the head, they realized that the unit had dirt/debris in the channel that the switch detents into. Not only was there a misunderstanding of how the switches worked because there was no training completed, whoever owned the unit wasn't properly maintaining the unit. This is not a design flaw. I don't know about others, but one could eat off the inside of my unit. __________________ Eric Stadtmueller, otherwise known as, MEM "Da Pilot"
(Offline)

23rd March 2008, 00:16	#232 (permalink)
SeaBass Thom Susko Current Rebreather/s: Megalodon Ray Home Build Other Rebreather/s: Not Bought Yet Ray Home Build Join Date: Jul 2006 Location: San Clemente, CA Posts: 259	Re: RBW Traitor Quote: (Originally Posted by dz3866) after reading Rons last post, and seeing that Alex bought a used Meg and dove it without any training on that unit ,really puts him in a diffrent light with me, how can you preach safe reabreathers and safe rebreather diving and then break one of the biggest rules. Good point. When you purchase a new Meg (or get ISC's approval to use one) you sign as a Liability Waiver. Some view this as a "cover your assets" document but for the user it also is a very sobering read stating the inherent un-reliability of ANY type of equipment used in a Marine environment as well as the commitment by you to be carefully trained and responsible for it's safe use. Believe me I know I just signed one. Alex, what measures and or commitment have you taken to make sure you were/are using this rebreather safely. (Big deal was made about this by many on this forum when Dave S started diving a rEvo before he was trained even though HE had Pauls approval.) I am sure you are no dummy and have familiarity with many different units. But: Have you ever allowed anyone else to borrow or dive your Meg or any other rebreather you owned without them being properly trained on it by a factory authorized trainer? If that were the case, who would have been responsible if something happened to them? If you are willing to go on the stand as an expert witness (I have) expect to have your credibility brought into question by being asked these type of questions. Thom Last edited by SeaBass : 23rd March 2008 at 03:00.
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23rd March 2008, 08:11	#233 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,133	Re: RBW Traitor Quote: (Originally Posted by RonMicjan) 1. The O2 sensors must be as close as possible to the injector, otherwise the PPO2 control loop is the same as having a set of slow response sensors. I dont know why this is so, it hasnt been explained, however, I find that there is no problem with my unit keeping SP, nor have there been any complaints and according to all testing (HSE for CE cert) so far, there is no problem. note, the new units have a adaptive alogrithm that is better at keeping up sp during fast ascents,Alex was diving an old unit he picked up second hand and was diving with no training on the unit. I have to agree with Alex here.. Putting o2 injection before the stack slows down response time.. Its a design decision whether you want a "mixed" value or an immediate value.. Both have pluses and minuses.. The larger the volume before the sensors the slower the response time.. If you put the sensors at the injection point, you might not actually get to the setpoint unless you implement a full PID controller, but that has its own issue.. If you put it well before the sensors, you can overshoot the sp because you can get multiple injections if the diver has a slow respiratory rate.. I don't see it as a true manufacture falt, but a choice with positives and negatives.. I personally would rather have it near the sensors.. Quote: 2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass. There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit While in practice there shouldn't be a problem, I have seen sensors fall apart.. I had one fall apart on my inspiration and it was fine before the start of the dive.. No big deal here but if it was need to prevent bypass there could be an issue.. I will grant is statistically very low, but there is no way a diver would know it fell apart until they got a co2 hit... The sensor body and the checmical chamber has a very poor bond.. This is one point I have been asking Kevin to change on the HH CCR.. This arrangement started on the CIS as far as I know.. Quote: 8. User replaceable primary cells have no role in running an unstable life support system Are you suggesting rechargables? Why is it unstable? Use the checklist, monitor the battery voltage, dont dive with low batteries, if one side fails, end the dive on the other. Thats why there is a secondary. I would prefer to see secondary cells myself (specifc batch tested rechargable cells are much easier to characterize and you can really get meaningful life left measurement.. There are too many variations (in both batch and by manufacturer) for primary (no rechargeable) cells. Quote: 10. No auto turn on. It can be dived easily with the unit turned off if someone is dumb enough, and they may not have enough time on hitting the water to realise what they have done if the sun is bright enough to obscure the HUD. Design decision, you must open the head and turn the unit on prior to donning it. If you are soo stupid to turn the unit on before you strap it on, you are too stupid to not look at the PO2 before you put the loop in your mouth, checked the HUD, looked at the handsets??...sorry, no sympathy there, you should not be a CCR diver, or any diver for that matter. This is one point I am a strong supporter of... Wetswitches are an easy option, although they do have some negatives.. I would prefer to see both wetswitch activation and continual monitoring of the loop.. if it goes below ambient pressure multiplied by air, oxygen should be injected (this allows for sleep at altitude)... I think a 2 pronged check is a good idea.. If the ws threshold is reached turn the unit on, if not periodically sample the po2.. this way there is no single pint of failure.. There have definately been deaths on rbs prevented if a WS was implemented.. A third level of protection could be added by checking the pressure as well.. so you would need 3 failures for someone submerging or 2 if someone was on the surface... This is something thats easy to implement and I feel should be mandatory on all rebreathers.. I agree a prebreath is necessary but people do stupid things, but I don;t feel they should die because of a brain fart.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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23rd March 2008, 11:53	#234 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,080	Re: RBW Traitor Quote: (Originally Posted by SeaBass) Alex, what measures and or commitment have you taken to make sure you were/are using this rebreather safely. (Big deal was made about this by many on this forum when Dave S started diving a rEvo before he was trained even though HE had Pauls approval.) I am sure you are no dummy and have familiarity with many different units. To answer your questions: Safety measures taken: 1. I fitted a three cell independent PPO2 monitor before using it. 2. I had a buddy, it turned out a very good one. 3. We got in the Meg to understand what the failure modes were, simply because the accident rate was high and if there was a lesson there, we do not want to find it out the hard way (i.e. accidents on things we design). I did not get it in for recreational diving. 4. We put it on a breathing machine first. I emphasise this is different from doing a training course: we test a unit as it comes. For example, if the unit does not have positions for integral weights, I test dive it with a normal weight belt and see my (abysmal) attitude in the water throughout a dive - it tells me why divers are putting weights onto tanks with cam bands. A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't. Also the level of training is very variable, and test dives are about finding out what divers can foul up on. Alex
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23rd March 2008, 11:57	#235 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,080	Re: RBW Traitor Quote: (Originally Posted by mempilot) To add to this, they were flogging the Meg for shutting down inadvertantly. After much debate about the quality of the on/off switches in the head, they realized that the unit had dirt/debris in the channel that the switch detents into. Not only was there a misunderstanding of how the switches worked because there was no training completed, whoever owned the unit wasn't properly maintaining the unit. This is not a design flaw. I don't know about others, but one could eat off the inside of my unit. I differ on the design flaw. It is a design flaw as it is a single common mode of failure. Just fitting a battery compartment in opposite direction would fix this. Remember we tested the unit as it was received, from an instructor. We did not clean it, or fix it. We did not dirty it either. Our purpose is to understand fault modes, and we found one we did not expect. There is nothing in any manual I have seen about cleaning out those springs (that are not visible even). This is highlighted very well by Ron: he lists why things should be OK, but the fact is they are not. For example, there can be insufficient O2 injected on an uncontrolled ascent - Ron's answer is that it meets CE test by the HSE. The HSE are generally involved after a fatal accident: ANSTI would be the people to go to get a test done. The CE test Ron refers to is I assume the EN14143:2003 test: this tests at one breathing rate only and with only a slow ascent rate - it does not test for a panicked diver in an uncontrolled ascent. After I reported my finding that the PPO2 setpoint fell to 0.36, another Rebreather World user reported they had it become hypoxic on the same set point. There is an issue here, and the response is not to explain why it is OK, the proper response is to find the cause of this confirmed problem and fix it, before it kills someone. Most of the rest of Ron's comments take the same vein. Alex Last edited by AD_ward9 : 23rd March 2008 at 12:07.
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23rd March 2008, 11:59	#236 (permalink)
*EBT* Apprentice Luddite Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: UK, Brighton Posts: 2,147	Re: RBW Traitor Quote: (Originally Posted by AD_ward9) A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't. With respect, is that the manufacturers fault? Its a whole other debate though, so I'll leave the comment at that. __________________ Eagles May Soar, but weasels don't get sucked into jet engines! RBW Terms of service
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23rd March 2008, 13:07	#237 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,080	Re: RBW Traitor Quote: (Originally Posted by EBT) With respect, is that the manufacturers fault? Its a whole other debate though, so I'll leave the comment at that. According to EN61508 it is: the manufacturer must manage the entire product life cycle, not just design and sell it. There are two ways to handle this: 1. Do what Steam Machines did with the Prism and require people to sell it back before it is sold on, so they can check the buyer is trained and the unit is not faulty. Or how CCR Ltd manage things, with a timer counting down a year to factory service. 2. Eliminate failure modes that would cause an experienced eCCR user to die on their unit. Doing (2) is probably a good idea anyway. Alex
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23rd March 2008, 13:29	#238 (permalink)
diverklondike RBW Member Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Oct 2005 Location: Delaware, USA Posts: 1,785	Re: RBW Traitor Quote: (Originally Posted by AD_ward9) A manufacturer should not expect SCR or eCCR divers to do conversion courses to another SCR or another eCCR, because many divers don't. Alex Alex, You do not have the right to speak for what a manufacture may and or not expect and or require as it applies to any type of training on their units. If and when you deliver a unit and or a unit is delivered with your electronics then you can make your own determination. Is that what your saying here? That if and when your electronics are delivered on a unit there will be no requirement for cross over training if you have an CCR certification? As it applies to the HH CCR, I completed a cross over course for the unit reguardless of the hundreds of hours that I already have with the electronics. It was part of the terms underwhich I purchased the unit from the MFG. I can also say that I did find the class valuable. The only loose area in this equation in my mind is the second hand marketplace. That is obviously totally unregulated. I am not suggesting at all that there should be an control but only that it isn't. The other partially controling party here is the dive operator that "should" be asking for proof of certification but that's another story... Dive Safe.... Mark
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23rd March 2008, 13:53	#239 (permalink)
kevin stone Supporting Member Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: us ct. Posts: 231	Re: RBW Traitor Quote: (Originally Posted by RonMicjan) We want to hear about the ones you determined were diver error, because on your website you state “Nobody dies on a rebreather from user error, unless they take the mouthpiece out of their mouth and do not replace it with something.” as your objective. So in your opinion, a CCR should be completly tolerant of anything a diver does to it including no/poor maintainance. well here is your list on failure points for the meg, including the one that states "its too heavy" along with my previous arguments on said points, how well does this jive with the above statement, especially since you have never had day one of training on the meg and a bunch of your critisisms are addressed by the checklist (which apparantly you have never seen) and training. Now of course mike is going to accuse me of sleeping with my meg and showing favoritism, but folks, please keep in mind, I am an instructor on the KISS and Meg, not anything else, so of course I am only capable of defending something I actually know something about, not like alex who has never been trained or used a checklist on the meg. Ok, I found the original list of Meg supposed faults and have added comments below from a Meg diver/instructor point of view. As kevin has stated, I believe ultimate safety is in the hands of the responsible diver, although the designer should do the best possible job, end safety is in the divers hands. All of alex's notes in red. 1. The O2 sensors must be as close as possible to the injector, otherwise the PPO2 control loop is the same as having a set of slow response sensors. I dont know why this is so, it hasnt been explained, however, I find that there is no problem with my unit keeping SP, nor have there been any complaints and according to all testing (HSE for CE cert) so far, there is no problem. note, the new units have a adaptive alogrithm that is better at keeping up sp during fast ascents,Alex was diving an old unit he picked up second hand and was diving with no training on the unit. 2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass. There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit 3. It should not allow users to set a PPO2 set point below 0.7: it allows 0.4, which given its poor setpoint control, is an issue. Easy, dont set your rig on 0.4 if you dont think its a good idea, I never use that setting myself. There is a manual setting of .20 that allows the unit to be on w/o the solenoid firing away, nice to have for bench work, but not a diving setting. I would like to see this setting disabled when the unit is under water, maybe next gen. not a bad point and I have asked ISC to make the software change myself 4. It needs to meet EN61508 SIL 3 or 4, but does not meet any SIL level at all. This requires major redesign. Do not trust the electronics until then: not to update the display, or the HUD or anything else. Incidentally, a KISS PPO2 monitor would meet SIL 3. I do not know these specifications, so cannot argue the point. However, the meg has a secondary display that is passive, similar to the KISS unit, so if the KISS units meet sil3, then the meg does too. The SP software was written by a ex boeing embedded software designer (Steve) and we tend to do what we know, so why wouldnt steve design to the level required for jets, since that is where he came from? why not ask steve? What major redesign do you suggest? Specifics, not generalizations. 5. The unit can definitely switch itself off underwater without warning. HUD went off. Batteries were 6.9V, 6.0V under load. Discussed ad nauseum, but no real data, and this is the first report of a meg switching off on its own, unless the diver was not replacing batteries in a timely fashion. We know Alex was reading voltage off the primary when the problem was with the secondary. (based on a previous discussion)User error due to lack of training. 6. No warning buzzer, at least on the ISC handsets on the unit here. Design choice, whats wrong with the diver watching the HUD and taking responsibliity for thier own actions. I hate buzzers, beepers etc, wouldnt have one on a unit I own. 7. Needs a decent backlight on the handsets here - I know the Meg has too many different handsets, which adds to the problem. Im guessing that this is why the unit shut off, batteries were low, no backlight, unit shut off. reason: No training, not using checklist, ignorant of safety features like low battery warnings. Too many different handsets???? there has been ONE since the introduction of the unit. Not including the shearwater system. The backlights work just fine, I have never heard anyone complain about them. 8. User replaceable primary cells have no role in running an unstable life support system Are you suggesting rechargables? Why is it unstable? Use the checklist, monitor the battery voltage, dont dive with low batteries, if one side fails, end the dive on the other. Thats why there is a secondary. 9. PPO2 setting should be automatic near surface, to increase PPO2: diver can use a dangerously low PPO2 set point. Part of the pre jump in the water is for the diver to check setting and then again when reaching the target depth. There is a HUD, and handsets, and the Meg if turned on, will not allow a loop SP of under 0.20. We expect OC divers to monitor thier tank pressure...should we expect less of better trained CCR divers? 10. No auto turn on. It can be dived easily with the unit turned off if someone is dumb enough, and they may not have enough time on hitting the water to realise what they have done if the sun is bright enough to obscure the HUD. Design decision, you must open the head and turn the unit on prior to donning it. If you are soo stupid to turn the unit on before you strap it on, you are too stupid to not look at the PO2 before you put the loop in your mouth, checked the HUD, looked at the handsets??...sorry, no sympathy there, you should not be a CCR diver, or any diver for that matter. 11. HUD is not always visible, depending on the mask. DUH, buy the right mask or adjust the position of the HUD. Do you drive with cardboard over your speedometer in your car and then complain to the judge that the speeding ticket was undeserved? 12. Weight is excessive, and fitted up exceeds 25kg CE limit for lifting equipment (i.e. gives you back ache). Needs pouches at the top to improve the trim underwater. They weight is enough to hinder recovery in some cases. OMG, If you cant handle the weight of the unit, DONT BUY ONE! or get a mini, or stay on the porch. the unit ends up neutral underwater, there is plenty of room to stash trim weights at the top of the counterlungs attached to the D ring there. I suppose we need to ban all doubles because CE says they are too heavy? Sorry, this one just slays me, Patti, at 125lbs can dive a mini meg with 2 stages, a student of mine who weighs 145 dives a full size unit. 13. Hoses have Thiram in them (a toxic softener in the EPDM), and only just withstand the 25kg pull test (they do not when old). Dont know what Thiram is, but I have hung my own body from my assembled loop, plastic bits and all and done a pullup. Im over 100kilos. More BS. 14. Hoses need weighting: they are long and float too far away from the diver. In a dry suit getting them back involves a move that some divers would not manage. Try attending training, we show you how to recover hoses in 3 different methods and I have never had a student, drysuit or not, be unable to do any of the three. the loop can not get away from the diver like a BMCL unit can, this is just plain ignorance of the unit and lack of training, not to mention nit picking. Also, if you had trouble with finding the hoses, perhaps your instructor didnt do a very good job of fitting the unit to you...oh, wait, you didnt have an instructor did you? 15. There is no mouth strap to retain the mouthpiece with an unconcious diver. This is in EN14143 (I know, it is not applied, but safety standards should be applied whereever a unit is sold, when they represent good practice). If a diver wants a strap, they can go buy one, silly critique. 16. The solenoid can freeze shut too easily, and without warning. Sure there is a warning, Watch your PO2, thats what the HUD is for, listen for the solenoid. I had an instructor pull my O2 feed line, I heard the difference in the sound. Run the unit like you were instructed to manually with the electronics as a backup, you will find the bad solenoid on the next predive, but probably sooner. All part of the training and checklist use 17. The solenoid has excessive amounts of combustible material in it. Right, stainless steel can burn with enough heat and pure O2 around at high pressure. 18. There can be insufficient O2 injection on an uncontrolled ascent. not according to the CE testing done by HSE, which it has passed and the new adaptable injection algorithm. 19. Handsets hard to read: PPO2 values are too small, with too low a contrast, on the handsets fitted to the unit here. Opinion. If you cannot read the displays, buy a correcting mask or dont buy the meg, certainly not a failure point, again with the speedometer and ticket argument. 20. Counterlungs can come loose because harness is not fully integrated (people can change it), or they can float away from the diver, causing a large WOB increase. Yes and fastex buckles break continously, thats why everyone in the industry uses them. Design decision, personally I prefer to be able to remove my CL and dunk them in a cleaning solution, certainly not a safety issue. and the nylon harness can be eaten by a shark too and if the unit floats away, what do you do then. OK, so out of 20 comments, one or maybe two are relevant and could be improved upon but all are neglegible if the diver is doing the checklist and diving like they were trained. Alex, why dont you go buy a brand new unit, take it in to an independent tester and have a full CE test done on it, please forward the results to us, enquiring minds want to know. Remember that Leon wont sell you a unit w/o training so let me know if you would like to hire me for that. The above was pulled from an earlier post on Rebreather World, after Alex posted his failure point list on the meg, this is a distinct contrast to his statement "If a manufacturer does not have any single points of failure in a eCCR, and the overall product has been designed well, the chance of my finding any fault will be very low indeed" Now, I did say I was done posting, but hypocrisy brought me back to the fold. There have been some interesting points, great discussions and a lot of fun going on here but I think I need to apologize for using the word Traitor in the title, as that brought a little too much passion into the argument. It is quite possible that Alex does have all of our best interest and our safety in mind, but I still have some reservations on that subject, time will tell, as will Alex bringing a perfect CCR to market. Seeing the list would be nice too, eh mempilot? So what was the ISC response to any of these items when they were brought up? I think that is the real issue, all manufactures have issues it's how they are addressed when identified that I think is the main concern. Did ISC have a recall? Send a letter? Not to pick on any unit, just wondering how another manufacturer delt with issues. I dont dive a Meg so I have no comment. Thanks Kevin Last edited by kevin stone : 23rd March 2008 at 18:17. Reason: spelling
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23rd March 2008, 14:44	#240 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,661	Re: RBW Traitor Quote: (Originally Posted by RonMicjan) 2. There should be no differential pressure across the O2 sensors. They will fail early if there is. The sensors are not tested adequately by the unit. Also if the sensor falls out, then there will be excessive CO2 scrubber bypass. There is no differential pressure across the sensors during use. The only differential value is caused by the resistance of the scrubber, which is well within CE values. And any differential pressure cannot be more than the total WOB. During the predive, the diver is asked to record mv outputs of the sensors and its the divers job to track age and output changes, there is a table provided on the checklist. Agreed if the sensor falls out there will be a problem, however part of the predive is snugging the sensors and checking the o ring on them, and checking the molex is firmly seated. Something you would know if you had been trained on the unit Constructively speaking; I'm not sure that there hasnt been some confusion in the difference between the WOB and the differential pressure accros the scrubber. The WOB is a factor of all the components including the counterlungs and loop, the differential pressure would be measured between the inhale and exhale port of the scrubber. To illustrate my point, assemble a scrubber and breathe off it through one port, pendulum fashion. You will be unpleasanlty surprised at the WOB through the stack alone. This WOB is dissapated through the system when it is integrated into a loop. Although we have absolutely no empirical data relating to the actual differential pressure that is encountered when in use, it would be an interesting experiement to put a differential pressure monitor accross the inhale and exhale ports to determine the effect on the cells when breathed. John and I have been working on some interesting projects that have parallels to this particular problem and have considered carrying out this test. the WOB for a complete unit is related to the sum of its parts. To analyse each component means we can target individual components to reduce the overall WOB for a specific unit. Brent __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
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