Prevalence, causes, and prevention of oxygen fires

[rhwestfall]

i have no idea what a Blender course is, care to share please?

Proper training for the mixing of gasses (mix your own Nitrox & Tri-Mix - depending on course)

 

[JackOfDiamonds]

Proper training for the mixing of gasses (mix your own Nitrox & Tri-Mix - depending on course)

I don't think the casual diver takes a blender course, there isn't much of a necessity to know how to mix your own gasses considering most dive clubs (around here at least) will not let you use their compressor, they will do it for you.

Safety more comes into mind, even if you are not diving with a rich mix of Nitrox / Tri- Mix or what ever you should know the proper safety measurements to be taken around them as you are in an environment that consists of many fire / other hazards.

 

[Bob DBF]

The one 'big deal' is to ALWAYS crack the valve open slowly.

This goes for air as well, the same mechanism can cause an explosion and damage only of a lower order. In addition, a leak or loose connection can cause damage to people, the higher the pressure more damage can be caused before it is shut down.

#7 is interesting. Medical O2 uses BUNA-N O-rings according to The OxyHacker book. We use Viton

The med O2 tanks I was familiar with were 2215# and operational flow rates were low. This may have an effect on the the continued use of the O-rings.

The vast majority of medical O2 problems are due to poor practices in an O2 rich environment, after the O2 is clear of the tank and reg.


Bob

 

[Scubagaskets]

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[lowviz]

there isn't much of a necessity to know how to mix your own gasses considering most dive clubs (around here at least) will not let you use their compressor, they will do it for you.

There is an active netherworld of divers who own several tanks and a transfer whip.

There is an art to the order. Usually pure O2 first and then your leftover EAN-whatever. You top it off with your HP130 air that never hits the water but is kept full at all times.

I had a LabView program that allowed you to turn dials for pressure drop additions and swap tank orders to find the optimum scenario for the EAN mix you wanted. Being retired, I no longer have access to the platform that allowed me to make executable programs.

Hack blending is an art.

 

[boulderjohn]

• Contamination of valves and cylinders from contaminated fill equipment or a contaminated source of gas.

• Ineffective attempts at cleaning equipment for oxygen service.

Here are two anecdotes for thsoe two bullets.
We were filling trimix tanks via partial pressure blending. When we needed to go to the next helium bottle (Ultra High Purity helium), we inserted the connector and filled the tanks. When we were done, I pulled the connector and saw that the threads were covered with some kind of grease. I looked in the He tank valve and saw that someone had gooped it up with what looked like axle grease, which we had not noticed when we inserted the connection. That valve is supposed to be perfectly clean, especially if you are buying a product labeled "Ultra High Purity." We did not use the tanks we had filled, and we did a major cleaning on everything we had used.

In possibly the most famous of the Florida explosions, the dive shop employee who had been assigned the task of visually inspecting, oxygen cleaning, and filling the O2 bottle had never had any training in either visual inspection or oxygen cleaning. He used silicone lubricant on the tank threads.

Sorry for my ignorance but i have no idea what a Blender course is, care to share please?

A blender class teaches you to mix gases for nitrox and trimix. (Some classes do nitrox only.) The class he took focuses heavily on oxygen cleaning of equipment in the process. Not all of them do.

 

[Diving Dubai]

A picture is worth a thousand words

The 1st (passed to me) an O2 first stage that had had a flash fire whilst attached to the cylinder (I don't know the precise details and can only surmise)

The Second, I do know about. A dive boat in 2006 off the coast of Dubai

The cause was a Rebreather O2 fire. Nothing survived above the water line.

The replacement for this boat was named "Burn"

 

[2airishuman]

@2airishuman : Why is it that a unibody valve regulator might be better (safer) in itself if not also slow opening, non tortuous path, etc.?

Very interestin thread topic BTW.

1) It removes the risk of contamination of both ends of the DIN fitting. Instead, there's a schrader valve that is capped except at the fill station.

2) No risk of rapid loss of oxygen if the valve is opened with no reg attached

3) No risk of inadvertent cross contamination by using an oxygen reg on an air cylinder, or an air whip on an oxygen cylinder, or an air "tank checker" on an oxygen cylinder, because the reg and valve are integrated and the fill fittings are not compatible.

4) Allows the possibility of setting up the O2 fill station so that there is no DIN connector, so that it is not possible to inadvertently decant O2 into an air cylinder

Doesn't fix the tortuous path problem by itself but opens the door to someone doing it. Fewer design constraints and a much relaxed maximum flow rate requirement since only one 2nd stage is served and assembly does not have to support the very high mass flow rates that can be required with back gas cylinders at depth.

 

[2airishuman]

If you have an IP creep or something happen to the 1st, your whole deco bottle is gone until it can be serviced. This will probably cancel your dive day depending on logistics available. A quick 1st stage swap with a spare from your bag is a lot easier.

I love the idea of those integrated valve/regs especially for bailout but its just not practical for me.

Uh, bring a spare bottle?

 

[2airishuman]

In possibly the most famous of the Florida explosions, the dive shop employee who had been assigned the task of visually inspecting, oxygen cleaning, and filling the O2 bottle had never had any training in either visual inspection or oxygen cleaning. He used silicone lubricant on the tank threads.

This is the sort of thing that really frightens me off of tech. I have trouble extending blind trust to a shop regarding an O2 bottle. There are individual people who I would trust but dive shops are organizations, and it is hard for me to know beyond a shadow of a doubt that my cylinder/reg work was done by someone competent and was not then later screwed up by someone else.

The alternative is that I can do everything myself, but that's a large skill set and equipment/supplies investment to saw off.