What makes a unit safe?
- Thread starter Garth
- Start date
Jdailey777
New Member
The answer is very simple. We make it safe or we don't. You can base this on how we train, dive, and each decision we make as we start the process to prep the unit for our next dive. Although sh** hits the fan sometimes we should have trained to deal with most any situation we put ourselves into.
The decisions we make in the moment make the difference in wether we survive or not. do you dive conservative or do you through caution to the wind.
As a pilot I always have read that general aviation is the safest or most dangerous form of transportation depending on the type of pilot you are. Is your life important, do you operate with conservatism or are you always trying to push the limit. If you are cautious and follow and continue to practice your training you have gone through you should be able to get through most any emergency. If you are always pushing the limit sooner or later you will find it! I think this is why I was so drawn to diving rebreathers.
Safe diving friends
The decisions we make in the moment make the difference in wether we survive or not. do you dive conservative or do you through caution to the wind.
As a pilot I always have read that general aviation is the safest or most dangerous form of transportation depending on the type of pilot you are. Is your life important, do you operate with conservatism or are you always trying to push the limit. If you are cautious and follow and continue to practice your training you have gone through you should be able to get through most any emergency. If you are always pushing the limit sooner or later you will find it! I think this is why I was so drawn to diving rebreathers.
Safe diving friends
megdiver792
Fake Diver
Build a RB only a fool cant use, and only a fool will use it.
lizardland
Active Member
Write a useful test standard and test standards become useful. Is there anyone who actually thinks they are about safety rather than manufacturers trying to shut each other out? The benefit should be to the end user.
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Ben Field
All IMVHO obviously...
Small point- CE isn't a brand ;-) But you knew that
By even mentioning CE you have opened the thread up to trouble, so many people misunderstand it.
A manufacturer (of anything) can display a CE mark if the product was built, tested and audited to meet an EN standard (most things are as most people want to sell in Europe)
Is your question- "Do you believe EN14143:2013 makes a unit safe, if not what does?"
The standard contains some sensible stuff but EN's are not (as a rule) about safety specifically, safety might be a by product buts its not the total aim.
The Big issue with CCR's is that the standard explicitly lists some requirements that almost all units do not have (despite claiming the standard) and those are the simple things you can see, the more esoteric factors no user could distinguish without paying to test it are up to us to trust the manufacturer to have achieved. There also remains the option to use PPE and technical file routes to achieve the same mark allowing some flexibility in what is and isn't achieved.
Outside of the standard nonsense is the aloof concept of Safety, is it ever safe to submerge ourselves in a non-life supporting aqueous solution while weighted to sink?
With or without a CE mark the diver is still in the majority control of their personal safety, sadly we all live in a world where personal responsibly is outmoded concept and everyone wants protecting and to blame others for whatever happens to them.
You could argue that CE forces the manufacturer to remove the majority of the issues that might provide instant, unavoidable death even if you are doing things right, except that it can't, won't and never will.
As an engineer I have too much experience with electronics to trust small, cheap and niche electronics with life support operations, why would anyone trust them? We cannot trust multibillion £ businesses making cars, airliners and nuclear reactors to get hardware and software right so why trust low-run count CCR electronics?
The possibilities presented when diving are well outside the scope of what a ECCR can control, in extremis they are beyond the capability of OC too- diving is dangerous- either don't do it, get over it or MTFU and accept it.
I for one am fairly sick of divers expecting or demanding the unit to do the diving for them, if you can't dive- don't. :moon:
My opinion en 14143 is largely made up of bollocks, BUT all rebreathers should be machine tested to prove they do what the manufacturer says they do. If you have that test data the unit is potentially "safer" than one without any test data. But more importantly its the diver that should be tested, thats the dangerous bit!!
Walt Stearns
Member
What makes a unit safe? Hmmm.... IMHO, a truly safe unit would feature every conceivable warning system that actually worked, with redundant backup systems to get the diver out of any situation they get in, ragardless how much the F up, and is currently not available for purchase.
Remember the meaning of the term safe is something completely without risk.
Remember the meaning of the term safe is something completely without risk.
Captain Starfish
New Member
Not available for purchase now, and never will be. Not to say that the pursuit of the unattainable goal isn't worthwhile - every bit safer is to be commended. But there will always be a new scenario.
To me, what makes the unit safe is the mumpty strapped into it. Know that your unit can and will fail despite best efforts to keep this misbehaviour to a minimum, be prepared to deal with it, and don't allow yourself to fall into that happy complacent state where the breather is just another bit of dive kit.
To me, what makes the unit safe is the mumpty strapped into it. Know that your unit can and will fail despite best efforts to keep this misbehaviour to a minimum, be prepared to deal with it, and don't allow yourself to fall into that happy complacent state where the breather is just another bit of dive kit.
I'm a big believer in engineering out as much stupid as you can. For instance having Orings in a contrasting color from the part they sit in so that their absence is more obvious. Or using left and right handed threads on similar but not identical pieces to avoid putting parts together wrong. The ability to positive and negative check all critical orings during assembly, etc. To my knowledge, CE marking has zero standards for these "best engineering" practices.
Otherwise you might as well ask what is dangerous. Is it 1 fatality per 10,000 events or 1 per 100,000, or 1 per 1,000,000? Everyone has their own measuring stick for dangerous vs. safe.
Otherwise you might as well ask what is dangerous. Is it 1 fatality per 10,000 events or 1 per 100,000, or 1 per 1,000,000? Everyone has their own measuring stick for dangerous vs. safe.
Capt Morgan
Member
What makes a unit safe?
Existing only in pdf form
Existing only in pdf form
No, for two controversial reasons: 1) A couple of manufacturers have proven that you can CE mark a rebreather and successfully sell it, without it meeting any standard and 2) there is no (longer a) requirement in achieving CE to actually do a check on the actual rebreathers functional safety to identify any un-safe features of its design.
In addition as Dave mentioned, there is actually nothing in EN14143 that addresses how safe a rebreather is. It is purely a level of minimum performance levels that the unit should meet if it is certified to that level! WOB and scrubber duration are but 2 of the 50 odd requirements.
In my personal opinion to have some surety its safe, you as an individual have do your own due diligence to identify exactly what testing has been done on it and what standard that testing has been done to and identify what about its design COULD kill you! Examples of the last are multiple reports of elecs rebooting underwater, unit able to be mis-assembled, flooded without recovery or made from parts (such as delrin, Lithium batteries or PVC wiring in the loop) that aren’t allowed in more serious kit by the likes of the USN. Will it kill you if you make one mistake or do you need to make several mistakes sequentially?
Safe to me, is if a failure occurs either the unit as a whole or the particular sub-assembly fails-safe and should not kill me…..
Examples of not safe to me as far as a rebreather design goes, means a unit that has been deliberately designed such that: I can mis-assemble, leave an o-ring out of during normal assembly, it has a CL not ruggered enough for the use, one that I can’t flood recover, has a BOV with too high an WOB, will get a caustic cocktail on, will provide too much or too little O2 without notification or that will kill me if a normal failure mode like two cells going current limited occurs…
If something fails, I want that failure to be obvious and not insidious!!!
I would also expect the individual manufacturer to broadcast any identified element of the design that caused a fatality or near miss safety related incident; to take appropriate steps for that safety critical design failing to not occur again to others…..
Dave, taking the second part onboard where all bar one section relate to machine testing requirements that provide comparable data, what parts of EN14143 do you consider are bollocks and why?
Dave, should they consider the unit they are diving to be fundamentally safe and then build from there to be safer themselves?
Walt, why? That would appear to address how to make things safer for the diver but doesn’t seem to actually address what makes a unit safe!
Brad i dont necessarily think the actual tests are bollocks except maybe a couple but what i really dont like is the amount of "interpretation" that is allowed from one notified body to another and from one manufacturer to another. I still strongly believe all rebreathers should be machine tested i would just like to see uniformity. My comment about the diver still holds as an example how does a diver die by going in the water with his o2 switched off? He must have missed so many tests to even get that far!!! But i know your going to say it can be engineered out and maybe it can but you cant engineer the divers responsibility out
Dave, Roger that; your not alone in your thinking!
Dave, your right I don't think the kit should be designed to let the diver get in that situation in the first place but on the responsibility front, fully agree. I just personally think the divers actions are a secondary layer over and above those of the kit. Trust but verify!
Thanks for the clarification.
Regards
Brad
Inversely proportional works better for me!
The simpler something is to use as a system, the less there is to go wrong or the easier to see it has gone wrong.
Take the Poseidon BOV: it combines a DSV, ADV and second stage. So compared to having those parts individually distributed around the rb you now reduce the number of hoses, o-rings and separate parts that could have a failure, reduce the total bulk and weight of the rig and everything is to hand in one place in case of an issue! What is less complex for the diver? What engineers 'stupid' out more!
If you had said "complexity of the design and testing behind the unit is directly proportional.....", now that is something different. Sometimes the simplest things are the hardest to design....
I could give you my CCR field stripped as a box of bits. It might take you a while to figure out where everything goes, but there is only one way you could put it together that allows it to be dived!
Mark Chase
ATB=AlwaysTalkingBollocks
A safe unit is indipendantly tested for WOB & scrubber duration and has totaly seporate power and eectronics for the two displays (hand set and HUD) IMHO the HUD should display real time PP02 for each cell
I think it should have an ADV and manual inject for dill and 02
I strongly beleive it should have a BOV
Flood recovery is a bonus feature
Abuility to conect off board gas is a bonus feature and I am happy with the BOV having access to off board gas I can use in the loop
At this point in time the poor relaibuility of all the other crap they bolt on to CCRs is enough for me to consider them more dangerous than they are worth
However I have to admiut that i am liking the idea of having my needle valve on my ECCR. If the Eccr fails I can just run the needle valve. Very usefull. If required the needel valve can be left off or very low so the unit runns ECCR all the time.
Simple mechanical device. The kind I like
I also very much like rjaks ideas for unit asembly.
ATB
Mark
I think it should have an ADV and manual inject for dill and 02
I strongly beleive it should have a BOV
Flood recovery is a bonus feature
Abuility to conect off board gas is a bonus feature and I am happy with the BOV having access to off board gas I can use in the loop
At this point in time the poor relaibuility of all the other crap they bolt on to CCRs is enough for me to consider them more dangerous than they are worth
However I have to admiut that i am liking the idea of having my needle valve on my ECCR. If the Eccr fails I can just run the needle valve. Very usefull. If required the needel valve can be left off or very low so the unit runns ECCR all the time.
Simple mechanical device. The kind I like
I also very much like rjaks ideas for unit asembly.
ATB
Mark
Doole
Member
Well rumours are that the design of the poseidon bov, killed a guy who acted very wrong.
So I don't think it's such a great example
Garth
Tunnel Vision
Yes not a very good example.
PLUS the actual unit of the poseidon is not exactly simple. I suppose the operation is intended to be simple but that is only because there is little to do to "fix" anything and the choice is to bailout or bailout of anything occurs.
That may work for some diving.
The poseidon is not simple.
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Didn't someone take a CO2 hit on a Poseidon (supposedly) due to a dog hair in a critical Oring on the scrubber? I thought I read about it on TDS a few years ago but perhaps I'm mistaken.
As the owner of 2 Newfoundland dogs (if you don't know the breed they are hairy!) any unit which is so sensitive to hair is "unsafe" to me. Sorry, but being required to assemble a unit in a veritable clean room is a really foolish assumption which should be engineered out through better sealing surface/o-ring design.
As the owner of 2 Newfoundland dogs (if you don't know the breed they are hairy!) any unit which is so sensitive to hair is "unsafe" to me. Sorry, but being required to assemble a unit in a veritable clean room is a really foolish assumption which should be engineered out through better sealing surface/o-ring design.