Deco Cylinder Mishap

[openmindOW]

It could be. If you aren't sure, take a cylinder handling class. To be sure, this was a real snake in the grass. No way to anticipate the results at all.

I'd like to recommend a separate Thread on the safe storage and transport of O2 bottles.

 

[DandyDon]

I'd like to recommend a separate Thread on the safe storage and transport of O2 bottles.

Good idea. Go for it. You might link it here.

 

[fdog]

About using the plugs on DIN valves: the XSScuba convertible valves have a small pressure relief hole in the side. With the plug tight and the valve open the gas escapes through this vent and you hear a loud hiss. It also limits the rate of loss of gas. So for this particular valve using the DIN plug would help to pick up a leak and to limit the rate of leak.

All three of my tanks have the valves with the side vent.

Adam, I presume you're speaking about this pressure relief hole in the valve. The behavior you describe is not normal.

The XS Scuba (aka Thermo) DIN/Yoke valve


If gas leaks from this hole with the DIN plug tight, you must have either an o-ring missing, or a displaced o-ring.

Leaking from this hole with a plug inserted is not by design: the DIN plug mimics the connection made by a DIN regulator, so if it leaks with a plug, it will also leak when using a regulator - hardly a good design goal.

It takes quite a bit of displacement to get to the point where this hole allows gas to escape. When I've pressurized a valve with a DIN plug inserted, it usually takes me ~3 turns of the wrench, backing the plug out, until the gas vents from the pressure relief.


I for one want a DIN plug to be solid. When it's in place, I know I won't loose $150 worth of fill just because someone stubbed a toe on the valve. The relative safety of putting such a DIN plug on a 100% O2 cylinder is being debated over on this thread.

In terms of prevention, one possibility that's being discussed for this accident is an oxygen-rich environment caused by a slow leak. Certainly an intentionally vented DIN plug wouldn't have prevented this. Even a solid DIN plug may not have; there are many other slow leak sources, such as a loose bonnet, that are yet to be eliminated.



All the best, James

 

[Hetland]

Yes!! Advanced Nitrox! That teaches you HOW to use it safely. But that's not saying that the average diver could not buy or use it if he felt so compelled. I personally don't know that it is very rigidly enforced.

Breathing the wrong mix at the wrong depth is a very fast way to kill yourself.

 

[bleeb]

This incident has got me thinking. I have 100% O2 bottles for SCUBA Rescue in my garage. Is this an unsafe practice?

Not sure if the question came across the way you intended, but as written, in my mind, storing O2 cylinders inside a garage (or truck cab) is not a yes/no safe/unsafe issue. It's a 'what are the chances of a problem, error or screw-up' in each situation, and which one is more or less safe and tolerant of problems. What are the chances of knocking over a tank, or dropping on during handling, and in the process accidentally rolling a knob even a tiny bit. Once you have that pure O2 floating around, there are almost always lots of mechanisms to ignite and fuel a fire, so which situation either minimizes the chances of accumulating high concentrations of O2 or limits the damage?

 

[herbdb]

I have been following this thread and do not understand how the O2 rich air in an auto interior caused an explosion. I can see a very hot, uncontrollable fire, but what would fuel a violent explosion?

Can someone enlighten me?

 

[Hatul]

Adam, I presume you're speaking about this pressure relief hole in the valve. The behavior you describe is not normal.

The XS Scuba (aka Thermo) DIN/Yoke valve


If gas leaks from this hole with the DIN plug tight, you must have either an o-ring missing, or a displaced o-ring.

Leaking from this hole with a plug inserted is not by design: the DIN plug mimics the connection made by a DIN regulator, so if it leaks with a plug, it will also leak when using a regulator - hardly a good design goal.

It takes quite a bit of displacement to get to the point where this hole allows gas to escape. When I've pressurized a valve with a DIN plug inserted, it usually takes me ~3 turns of the wrench, backing the plug out, until the gas vents from the pressure relief.


I for one want a DIN plug to be solid. When it's in place, I know I won't loose $150 worth of fill just because someone stubbed a toe on the valve. The relative safety of putting such a DIN plug on a 100% O2 cylinder is being debated over on this thread.

In terms of prevention, one possibility that's being discussed for this accident is an oxygen-rich environment caused by a slow leak. Certainly an intentionally vented DIN plug wouldn't have prevented this. Even a solid DIN plug may not have; there are many other slow leak sources, such as a loose bonnet, that are yet to be eliminated.



All the best, James

Hi James, I looked at my tanks again, and the key I think to the difference is the design of the plug. My plugs are plastic and have an O ring NOT in the same place as a DIN reg, rather just inside the knurled outside part. Later in the day I'll see if I can take a photo. The inside part of the plug allows the air to leak out through the vent even when the plastic plug is tight.

Your plug must be designed like the male part of the DIN reg and totally seals the tank like a reg.

Adam

 

[Wookie]

I have been following this thread and do not understand how the O2 rich air in an auto interior caused an explosion. I can see a very hot, uncontrollable fire, but what would fuel a violent explosion?

Can someone enlighten me?

When something burns in a Oxygen rich environment, it's hard to tell the difference between explosion and violent fire. Google "back draft" or "flash over".

 

[ianr33]

I have been following this thread and do not understand how the O2 rich air in an auto interior caused an explosion. I can see a very hot, uncontrollable fire, but what would fuel a violent explosion?

Can someone enlighten me?

You are correct,it would be a fierce fire rather than an explosion,although if you were up close and personal with it the difference would be pretty academic.

The original news report stated:
<<Investigators believe the fire involved a scuba tank in the vehicle, which burned the victim. Shortly after EMS moved the victim, the fire spread to another tank and caused it to explode.>>

So if that is accurate (always a big if!) the initial fire caused another tank to "explode"

 

[Hatul]

Hi James, I looked at my tanks again, and the key I think to the difference is the design of the plug. My plugs are plastic and have an O ring NOT in the same place as a DIN reg, rather just inside the knurled outside part. Later in the day I'll see if I can take a photo. The inside part of the plug allows the air to leak out through the vent even when the plastic plug is tight.

Your plug must be designed like the male part of the DIN reg and totally seals the tank like a reg.

Adam

Here are photos of the plastic DIN plugs and the vented XS Scuba valve:


I can't think of a disadvantage to the design of the metal plugs you're using, except when pressurized there's no way to relieve the pressure from the O ring except by unscrewing under pressure which could dislodge the O ring. The plastic plug has to be designed this way because the material is not strong enough to hold back the high pressure and could blow out otherwise.

Adam