Yes or No?

[MaryS]

from personal experience I've never been asked to leave the valve open, just prove the cylinder is empty (quick turn on & off and explain that if it doesnt hiss its empty)

even if it was open - packed in a bag for that short duration I wouldnt worry about it.

[Rovingshark]

Whether it is our diving cylinders or not all i know is that certain cylinders dont completely discharge...

Err..........how do they get the valve out (eg for O2 cleaning) if there's still pressure in the cylinder?

Even if they manage to unscrew it, I think it might be a bit 'lively' when the pressure finally vents.

RS

[nigelH]

It would take a hell of a lot of oil inside to explode a cylinder.

And how.

Back in the days before YD when uk.rec.scuba was the place to discuss UK diving on the web we calculated the quantity of octane (chosen as a nasty, volatile hydrocarbon) it would take in a cylinder that when ignited explosively would take the thing from its working pressure to its test pressure.

It was more than the lethal dose if inhaled and octane isn't particularly poisonous. A cylinder that could do no more than go thump and get hot would kill the user if you dived it.

The problem with O2 is not O2 clean but O2 service. You do need the right materials and a reasonably clean system. However people confuse not dripping with oil with surgically clean standards. The classic idiocy is the "You've touched it so it has to be re-cleaned" line. What goes for a scalpel contaminated with bugs that can reproduce exponentially does not apply to simple chemicals.

[baldeagle]

Panic not everyone...either tonight or tomorrow morning the answer will be provided to show you that Baldeagle isnt completely talking out of his arse knowing my luck itll probably be a cylinder of tyre weld or something!!!!!

[RogerViking]

of course its clean ..sure it says so on the sticker..

only air could have gotten in not under pressure.

[baldeagle]

Modern medical,breathing,and diving grade "J"(50litre)cylinders are the little herberts...i knew there were some cylinders somewhere that didnt drain down...it has what is called a "residual gas valve"....so thats my twin 50s safe to take on a plane!!!!

[Wing Nut]

JamesP “How many atmospheres do you reckon the pressure will drop by?”
3.246 – roughly.
As I said, assuming the hold isn’t pressurised. Also assuming you ascend to around 35,000 feet and with a standardised sea level temperature of 59F. When you put your bit of sticky tape on the tank valve at sea level you would be doing so at a pressure of roughly 29.92 in/Hg (say 14.69 psi). As you ascend to 35,000 feet the ambient pressure drops to around 7.04 in/Hg (say 3.46 psi). Therefore, (14.69 psi/3.46psi) – 1 ata = 3.246 ata
Even with a pressurised hold it could drop around 1.39 ata. In this case assuming you are flying at around the same height and using the standardised minimum recommended cabin pressure of 10.9 psi . Dropping now only 3.79 psi. In either case I still would not rate your sticky tape’s chances of providing a seal.
Normalising all references to atmosphere at an assumed sea level is, in my experience, a convention that is common only in diving and some of the more basic realms of engineering. Presumably to make the concept a little easier to grasp. You’ll forgive me if my terms of reference differ a little from yours. You are of course quite correct though, it seems that having done the calculations my original guess of “a couple of atmospheres” was far too conservative.
You need not worry about the possibility of diving on one of my dodgy blends. I reserve these purely for personal consumption. On the other hand you may be more concerned to hear that my former students could well be designing the cars that you drive, the bridges that you drive over, possibly the aircraft in which you fly and maybe even the chambers that you frequent. I wouldn’t let this play on your mind though, it will no doubt just worry you.

Roving Shark
“The same muck that was in there in the first place or the stuff that’s magically appeared”
Now this really isn’t my area of expertise. I’ll simply have to take your word for the fact that the air on commercial aircraft is so wonderfully pure. Is the food delicious too?
“Agency bashing” Excuse me? I believe I was supporting the stance that I hear is taken by that particular agency. How would that be bashing? And “Facts”, please.

It has been a blast but I think, on reflection, I’ll leave the Yorkshire Divers Community with its own peculiar take on the physical world. It really has been an education. Happy diving.

[MarkP]

I assume you’d leave the valve open while it’s in the plane hold, I’m also assuming that the hold of a plane isn’t pressurised. So I’m not sure that your tape would still be in place when the plane has ascended to 30 whatever thousand feet and the ambient pressure has dropped a few atmospheres.

Calll me Dr Dumb, but in the very unlikely event that the hold weren't pressurised I'm struggling to work out just how the pressure would drop by any more than one atmosphere, even if said aircraft flew to the moon and beyond.

Besides, as any fule kno, to maintain O2 clean status you need to put green tape over the open valve.

[nigelH]

When you put your bit of sticky tape on the tank valve at sea level you would be doing so at a pressure of roughly 29.92 in/Hg (say 14.69 psi). As you ascend to 35,000 feet the ambient pressure drops to around 7.04 in/Hg (say 3.46 psi). Therefore, (14.69 psi/3.46psi) – 1 ata = 3.246 ata

It has been a blast but I think, on reflection, I’ll leave the Yorkshire Divers Community with its own peculiar take on the physical world. It really has been an education.

Can I cut this out and keep it?
I haven't laughed so much in years

[Frankie Price]

JamesP “How many atmospheres do you reckon the pressure will drop by?”
3.246 – roughly.
As I said, assuming the hold isn’t pressurised. Also assuming you ascend to around 35,000 feet and with a standardised sea level temperature of 59F. When you put your bit of sticky tape on the tank valve at sea level you would be doing so at a pressure of roughly 29.92 in/Hg (say 14.69 psi). As you ascend to 35,000 feet the ambient pressure drops to around 7.04 in/Hg (say 3.46 psi). Therefore, (14.69 psi/3.46psi) – 1 ata = 3.246 ata
Even with a pressurised hold it could drop around 1.39 ata. In this case assuming you are flying at around the same height and using the standardised minimum recommended cabin pressure of 10.9 psi . Dropping now only 3.79 psi. In either case I still would not rate your sticky tape’s chances of providing a seal.
Normalising all references to atmosphere at an assumed sea level is, in my experience, a convention that is common only in diving and some of the more basic realms of engineering. Presumably to make the concept a little easier to grasp. You’ll forgive me if my terms of reference differ a little from yours. You are of course quite correct though, it seems that having done the calculations my original guess of “a couple of atmospheres” was far too conservative.
You need not worry about the possibility of diving on one of my dodgy blends. I reserve these purely for personal consumption. On the other hand you may be more concerned to hear that my former students could well be designing the cars that you drive, the bridges that you drive over, possibly the aircraft in which you fly and maybe even the chambers that you frequent. I wouldn’t let this play on your mind though, it will no doubt just worry you.

Roving Shark
“The same muck that was in there in the first place or the stuff that’s magically appeared”
Now this really isn’t my area of expertise. I’ll simply have to take your word for the fact that the air on commercial aircraft is so wonderfully pure. Is the food delicious too?
“Agency bashing” Excuse me? I believe I was supporting the stance that I hear is taken by that particular agency. How would that be bashing? And “Facts”, please.

It has been a blast but I think, on reflection, I’ll leave the Yorkshire Divers Community with its own peculiar take on the physical world. It really has been an education. Happy diving.

I think you are taking the psi.