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Just not enough dive time.
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Going on from the TANKS thread, what happens when an 02 clean cylinder gets contaminated, unkowingly obviously and you get the now non-02 clean filled with Nitrox.

Anyone had it happen?

Matt
 

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<font color='#000080'>Erm, I've done it a hell of a lot. I often ill me tanks on the club compressor, and I've never had a problem. Ever. Our club compressor is nearly clean as I understand it, and I've really not given much notice to the O2 cleaning argument. I get my tanks cleaned because otherwise they won't fill them with Nitrox.

The tank doesn't go bang, the world doesn't explode, but then I know who's looking after the club compressor, and I know how often the filters etc. get changed. I'd be less keen to do it on a compressor at a random dive centre I didn't know the staff from, or who did the maintenance.
 

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Finless: You couldn't invent him...
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In theory your cylinder would no longer be considered useable for anything other than air and would need to be O2 cleaned before use with EANx again.

I think the rules and regulations are more for the protection of the the "fillers" who might be adding 100% O2 to a bottle before topping it off with air to get the correct mix required -for example.
 

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A short fat well off crap cave diver. Likes wrecks
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[b said:
Quote[/b] (MATTBIN @ Feb. 12 2004,17:22)]Going on from the TANKS thread, what happens when an 02 clean cylinder gets contaminated, unkowingly obviously and you get the now non-02 clean filled with Nitrox.

Anyone had it happen?

Matt
Your balls drop off your hair falls out you blow up like a baloon you dribble muter utter giberish most of the time and things grow out of your head.




If you think I am kidding just take a look at Howard the Dive Dude. He was DIR before that dodgy gas fill in 1997

A very sad case

Mark Chase


 

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Duvet Diver
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Worst case you get a fire or a bang, however you'd need to have one hell of a contamination (if I recall 10cc of hydrocarbon) before you exceeded the safety limit of the tank's lines etc.

Simon A
 

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[b said:
Quote[/b] (Simon A @ Feb. 12 2004,19:23)]Worst case you get a fire or a bang, however you'd need to have one hell of a contamination (if I recall 10cc of hydrocarbon) before you exceeded the safety limit of the tank's lines etc.

Simon A
IIRC someone came up with some evidence that that for there to be a sufficient level of hydrocarbons to actually cause a cylinder to explode it would be extremely toxic to breathe

Daz
 

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[b said:
Quote[/b] ]Your balls drop off your hair falls out you blow up like a baloon you dribble muter utter giberish most of the time and things grow out of your head.
Fcuking Hell Chase - Now I've got coffee everywhere!

Does it make you post reams and reams of funny numbers on the internet too?


Good thread - I've wondered what would happen and whether this was some HSE theoretical wet dream.

I too thought it was to protect fillers from explosion when topping off with pure O2.  However, I've always been told that's crap since Welders use pure O2 all the time, in bottles which are topped off and not necessarily purged and refilled, and certainly not O2 cleaned as we would know it.  Not seen many welders go pop...

Anyone done any testing (Faber etc)?
 

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Ginger, Irish, sometimes stroppy
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I always thought it was a combination of two things;

Explosive contaminents (of which hydrocarbons are only one), and I agree it is only an issue really at higher O2 levels so it would present a risk to fillers potentially.....but bear in mind the explosive potential would be increased by pressure also for most gases. I also have a vague reccollection that the HSE would set standards for the 'whole' system, so some of the same standards that apply to the compressor etc would have to apply to the cylinder before it could be attached.

The other aspect would be tank corrosion, as higher O2 would increase the rate of corrosion within the cylinder and so the checks etc would need to be more frequent/thorough to prevent any other failure.

usual disclaimer applies; these are just my own pseudo-scientific ramblings which may or may not be accurate and may or may not make any sense at all.
 

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<font color='#000F22'>A far as I can remember, it's largely a factor of the pressure increase in the cylinder being filled.

Ex. a cylinder with 60bar o2 being topped off with air. The fill station cracks open the bank and in comes a rush of air, what happens when it all gets to the bottom of the cylinder? Can't go any further, so all the air molecules pile in to each other and jostle about, creating a large amount of heat, (as we've all seen when we collect bottles.) At the initial stages of the fill you still have a large o2% say 60% - 80% as we've only just started filling, but now we have a very hot spot at the bottom of the cylinder from the air top up, just where the high o2 is & add into this equation hydrocarbons,

Remember the fire triangle, heat/fuel/oxygen well we have all 3 concentrated in a small area. This is where the risk of catastrophic failure presents itself.


On a lighter note, there's a large factor of safety built in to these and have a buddy who fills his nitrox cylinders in work & dives sole often who has and uses cylinders that are out of test, as well as long out of o2. Come to think of it I'm not sure they were marked up and have ever been cleaned.

But again they only use Acetone so as long as your careful when reassembling the threads you could do it yourself. I seem to remember it was hydrochloric acid used to clean pillar.
 

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Just not enough dive time.
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Discussion Starter · #10 ·
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Mark you bstd.  

I'm at home and its MY laptop that now needs a cleanup.

So it looks like another case of you need a ticket (read sticker) or you dont get a fill, seen that somewhere else I think. No scientific proof just another rip-off.
Good.

Matt
 

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Small, yet perfectly formed...
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it's all one of those theoretical risks that no-one has ever heard of actually causing a problem.
Same as Mobile phones blowing up the petrol station...you have read the urban legends but where are the pictures?
 
G

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IMPORTANT

It's got nothing to do with blowing up filling stations.

Any contaminent in the cylinder may react with 100% O2 during partial pressure filling - the most used filling method in the UK.

This reaction would most likely result in a tiny puff of smoke as hydrocarbons combust within the tank. You (or the person filling) will not know that this has taken place.

During your dive you will be breathing toxic gas at an elevated partial pressure - this may kill you without warning.

Please dive safe.

Kev
 

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Kev, given the volumes of gas involved, do you think a puff of diesel fumes will make that much difference?

Having said that, we are all taught to "sniff" the air as part of the checks.

Mine smells rubbery  










(Ah...fank you velly much...)
 
G

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Volume of toxic gas at the surface does not matter as much as how it affects you under pressure.

The deeper you go the more likely it is going to become poisonous.
 

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Just not enough dive time.
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Discussion Starter · #16 ·
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Kev
given that people on here and I suppose other divers too have had their cylinders 'contaminated' we dont know of any deaths is this again just urban myth? Dont get me wrong I dont think its a good idea to be casual with what gas you breath hence my suggestion I only fill my tanks with 02 clean air or Nitrox.
Are there any autopsies that have shown diver death due to breathing 'toxic' gas due to a less than clean fill.

Matt
 

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Try breathing the gas from a car exhaust, and then decide if you would really not notice contaminants present from oxidised hydrocarbons
 

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[b said:
Quote[/b] (CPT. CRACK @ Feb. 13 2004,18:23)]During your dive you will be breathing toxic gas at an elevated partial pressure - this may kill you without warning.

Please dive safe.

Kev
<font color='#0000FF'>I don't know if it's an urban myth, however what price would you put on being safe.  If I had to have a cyclinders filled from an unrealiable source then I would have them cleaned again just to be on the safe side.  

Only my opinion.  


Fiona
 

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Not as tall in real life
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[b said:
Quote[/b] (FionaB @ Feb. 16 2004,10:48)]
[b said:
Quote[/b] (CPT. CRACK @ Feb. 13 2004,18:23)]During your dive you will be breathing toxic gas at an elevated partial pressure - this may kill you without warning.

Please dive safe.

Kev
I don't know if it's an urban myth, however what price would you put on being safe.  If I had to have a cyclinders filled from an unrealiable source then I would have them cleaned again just to be on the safe side.  

Only my opinion.  


Fiona
I would not disagree with your premise but ultimately it comes down to risk vs cost.

How do we assess whether it is a real risk or a perceived risk.?

At what point do we decide that the cost outweighs the risk?  For instance if we were absolutly paranoid about safety, we would either not dive or have a safety diver or two in the water with us, plus full medical teams on standby.  (Probably beyond the budget of most of us  
)

Also a reputable/reliable source, is only reliable until they give a bad fill and it can happen to the best of them.  Admittedly in the main the reliable/reputable sources would have less instances of this, so less risk.

Personally I am happy to evaluate the risks and where evidence exists I will make an informed decision.

Just out of interest,  how many people actually do a smell and taste test on their air?  Or do they neglect this on the basis it has come from a reliable source?

Daz
 

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<font color='#000F22'>
[b said:
Quote[/b] (daz @ Feb. 16 2004,14:53)]
[b said:
Quote[/b] (FionaB @ Feb. 16 2004,10:48)]
[b said:
Quote[/b] (CPT. CRACK @ Feb. 13 2004,18:23)]During your dive you will be breathing toxic gas at an elevated partial pressure - this may kill you without warning.

Please dive safe.

Kev
I don't know if it's an urban myth, however what price would you put on being safe.  If I had to have a cyclinders filled from an unrealiable source then I would have them cleaned again just to be on the safe side.  

Only my opinion.  


Fiona
I would not disagree with your premise but ultimately it comes down to risk vs cost.

How do we assess whether it is a real risk or a perceived risk.?

Just out of interest,  how many people actually do a smell and taste test on their air?  Or do they neglect this on the basis it has come from a reliable source?

Daz
As far as perceived risk verses actual risk you have to apply a little common sense. Using my LDS I have no quarms regarding the quality of the fills, and am not aware of any bad fills to myself or anyother customer & I know them well.

If when I dive and require fills at sites I don't know, then it's an evaluation of the shop. If it looks good etc, if in doubt I put my own personnnel filter on the tank. I think I paid £80 for it - It's just a charcoal filter that can be refilled.

gareth
 
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