Oxygen fire. Please read

[Simon TW]

I posted this on the other place, about six weeks after I posted it I was told of another unit going up in flames.

Just a gentle reminder to al of you CCR divers out there.

One of my former students has had an O2 fire in her unit. Not that it matters but to save all of the questions it was an AP Evolution. She turned on the O2 nice and slow as normal and within seconds it was on fire.

The unit was very quickly put into the water, they reckon about 30 seconds. Within that time there wasn't much left of it. It was really burned, the heat must have been so intense, all of the unit is barely recognisable. There is nothing left to salvage.

The thing that sticks in my mind is that if she had been wearing it when she turned on the O2 then there would have been a very sad outcome indeed.

From now I no longer turn on the O2 whilst I'm wearing a rebreather. I would advise everyone else to do the same.

http://i5.photobucket.com/albums/y175/265stw/Oxygen%20fire%20on%20Evo/CCR9_zpsf47f35a1.jpg
http://i5.photobucket.com/albums/y175/265stw/Oxygen%20fire%20on%20Evo/CCR12_zps57fcc736.jpg
http://i5.photobucket.com/albums/y175/265stw/Oxygen%20fire%20on%20Evo/CCR16_zps1deb7d9e.jpg
http://i5.photobucket.com/albums/y175/265stw/Oxygen%20fire%20on%20Evo/CCR28_zps37e643d8.jpg

[Rob Dobson]

Damn... I'm nearly always wearing my unit when switch the gases on; not any more.

I guess the unit being tied to the boat when you switch the gases on could be worse still as the delay in getting it untied whilst on fire could take out the entire boat. Hhhhhmmmm...

[JPTaylor]

Damn... I'm nearly always wearing my unit when switch the gases on; not any more.


I have always turned unit on when not wearing it, do everything short of pre-breath. Find it much easier to open valves & generally set-up.

[Ruffy]

Shocking stuff!
I dont think that anyone in our group switches o2 on while wearing the unit, I will show the pics around just to be sure:sweat:

[thetrickster]

Do we have any indication what caused the fire?

First stages - What condition where they in? When were they last serviced?
O2 Source - how was the 2ltr filled? Is it a known source?
Cylinders - in test?

Do you know the source of the fire? HP Port? LP Port? OPV?

Man, that is shocking :(
I'm hoping we can learn from this.

Glad she was okay.

[Scuba steve]

Boom .

I'd say it was a terrifying moment for the poor girl when it happened . Glad no one was hurt

[dwhitlow]

Do we have any indication what caused the fire?

First stages - What condition where they in? When were they last serviced?
O2 Source - how was the 2ltr filled? Is it a known source?
Cylinders - in test?

Do you know the source of the fire? HP Port? LP Port? OPV?

Man, that is shocking :(
I'm hoping we can learn from this.

Glad she was okay.
Agreed, it would be useful if there were identified factors.

I'll not show the missus that picture....

If I didn't take the booster outside to pump O2 I certainly would now!
(it was rather chlly last night as well)

[Kermit]

Take a look here.

http://www.thediveforum.com/incidents-safety-information/2036-dangers-high-pressure-o2.html

Not for the feint hearted..

ps. I turn my O2 on when the unit is on my back (leaky valve and all that). I think I might change that habit.

[ray]

Hi.

It could be anything which caused it, particle impingement, O ring blowing allowing a rush of 02, not fitting the 1st stage properly on the 02 bottle allowing oxygen to escape at pressure through the threads, favourite wrong grease contamination.. Dangerous stuff pure 02.

Either way lucky to get away with it without injury to anyone.. This one didn't http://i50.tinypic.com/1aplk.jpg



ray.

[nickb]

Reckon the service bill might be a bit pricey. I wonder if the cells are still OK :P:

[Graham Smith]

Reckon the service bill might be a bit pricey. I wonder if the cells are still OK :P:

I reckon the cells have converted to fairly decent CO2 cells by now.....

G

[Scuba steve]

As most on here know fire takes 3 things ( heat , 02, fuel ) to exisist . In the presence of 02 combustion points and temps can be dramatically reduced . But where's the heat ??? I can only guess that some sort of cleaning solvent fumes or vapours give the initial flash and the rubber in the presence of the 02 burns at the lower combustion temp . And the high levels of 02 makes the fire burn more fircely

[Rob Dobson]

As most on here know fire takes 3 things ( heat , 02, fuel ) to exisist . In the presence of 02 combustion points and temps can be dramatically reduced . But where's the heat ??? I can only guess that some sort of cleaning solvent fumes or vapours give the initial flash and the rubber in the presence of the 02 burns at the lower combustion temp . And the high levels of 02 makes the fire burn more fircely

The ignition in these cases tend to be high pressure O2 hitting a hydrocarbon causing a flash. I.e switching your O2 on the oxygen hitting some oil at high pressure.

[notdeadyet]

High speed gas coming to a sudden halt makes for a hell of a lot heat. Something that used to happen a lot in fixed gas installations is shit breaking down in the reg, fragments getting blown along a straight pipe, hitting a bend, everything slows, a ton of heat and kaboom. It used to happen in hospitals and labs surprisingly regular.

Must admit, I wouldn't trade the stainless pipework and HP compression fittings on the O2 side of my unit for anything. Rubber hoses, orings, crappy scuba connections... I really don't like them. Also means I can do away with OPVs as everything is rated to 200bar.

Sent from my GT-I9100 using Tapatalk 2

[Scuba steve]

The sudden halting of the very small amount of gas and subsequent small increase in pressure in a CCR shouldn't amount to sufficient heat to cause the flash . Again you need sufficient heat , fuel and 02 . And it all has to be in the correct proportions .

[gobfish1]

whats the leaky valve dives going do , turn it on sat on the bench for 30mins and piss away the goods ,

[notdeadyet]

The sudden halting of the very small amount of gas and subsequent small increase in pressure in a CCR shouldn't amount to sufficient heat to cause the flash . Again you need sufficient heat , fuel and 02 . And it all has to be in the correct proportions .

Really? I visited a site a few years ago where it happened in 1/4" pipe. What bore is a scuba hose?

Anything may have caused the fire in the OP but don't underestimate how much heat is generated AND the drop in ignition temperature of most materials (at 200bar brass will ignite at not far off half of the temp it would take at 1bar, neoprene rubber only takes a shade over 200degC at high pressure).

Sent from my GT-I9100 using Tapatalk 2

[Simon TW]

The sudden halting of the very small amount of gas and subsequent small increase in pressure in a CCR shouldn't amount to sufficient heat to cause the flash . Again you need sufficient heat , fuel and 02 . And it all has to be in the correct proportions .

Steve you don't need heat. I remember my old lecturer explaining Oxygen combustion when I was a lad and it was better than a magic show. He took an oily rag and put it on the bench then he opened the O2 on the welding torch and put it under the rag. Within a minute there was spontaneous combustion.

It served as a reminder that whenever the O2 hose had a hole in it to wrap some insulation tape around it and never ever stand over the O2 hose in your oily boiler suit. When the O2 hoe was mostly insulation tape it was time to buy a new one.

Why you don't need an additional heat is that the hydrocarbon molecules get exited in the presence of O2 and rub together causing friction and the friction produces heat which then results in combustion.

Sits back and waits for a scientific explanation.

[Simon TW]

whats the leaky valve dives going do , turn it on sat on the bench for 30mins and piss away the goods ,

Steve the leaky valve divers will be fine. I've just some maths based on a rEvo CMF at .8 litre per minute means 24 litres.

3 litre cylinders results in 200 bar reducing to 192 Bar

2 litre cylinders results in 200 bar reducing to 188 Bar.

I'd be happy to jump in with 188 bar.

[gobfish1]

Steve the leaky valve divers will be fine. I've just some maths based on a rEvo CMF at .8 litre per minute means 24 litres.

3 litre cylinders results in 200 bar reducing to 192 Bar

2 litre cylinders results in 200 bar reducing to 188 Bar.



I'd be happy to jump in with 188 bar.

188 BAR , Yep me to , Iv read about some turning off the gas to save a bit , Then turning back on when ready to jump , even read a few divers not remembering to turn said o2 back on jumping in with o2 off ,

maybe now , after seeing your post and numbers , some will think twice ,,

must say that photo puts the wind up me , thanks for posting sir ,

[notdeadyet]

I had a shutoff valve on my KISS so that I could shut the oxygen off but everything stayed pressurised. Loads of people told me I was going to kill myself because I wouldn't remember to turn it on. Oh well :D

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[ARJAYM]

I have always turned unit on when not wearing it, do everything short of pre-breath. Find it much easier to open valves & generally set-up.

+1

saves taking it all off when you find a problem

[ARJAYM]

[QUOTE=Simon TW;45946]
One of my former students has had an O2 fire in her unit. Not that it matters but to save all of the questions it was an AP Evolution. She turned on the O2 nice and slow as normal and within seconds it was on fire.

Any chance of finding out from owner or others present what they saw to get an idea of general are on unit where fire started ?

May have all been a bit quick but could be of use.

[flyingfisheye]

Was the unit left in the Sun? was it in the Red sea and at high temperature before the O2 turned one as a factor?

[Soggy]

once you've pressurised the unit then theres no further risk of fire?

[Mister Mike]

You will usually find that the cylinder valve has got stiff to operate . So that when opened by operator it jerks open causes instant pressure rise that heats up the Hp hose as it goes through the restrictor and ignites .It then flames back through the first stage burning out the diaphragm and creating a torch. The sintered filter should stop the cylinder igniting but not for long. So the best way to prevent this is to keep your valves serviced ,keep them clear of contaminants and when opening your valves do it in a controlled way and keep your hand on the tap until full pressure is reached. This way if there is a pop you can close the valve immediately and just have to deal with a black Mark and not the boat catching fire.

[Soup Dragon]

Frightening stuff I always turn gasses on do tests pre-breath before kitting up I know why now!!
Cheers
Soup Dragon

[PeterL]

In the picture of the reg, what's the hose that goes into that busted up ferrule, is it the HP or LP as it looks like it went pop?
Cause or effect?

PL

[Mark Rowe]

Has a CCR O2 fire occurred under water ever?

As how many CCR divers have done or keep in their bag of skills the ability to drive the unit O2 manually through switching the O2 cylinder on and off under water - Eg for a stuck solenoid
Understand the need to do it by some to get home but that's what the bailout is meant for too, but to be skilled to do it at depth you must practice.

[JPTaylor]

As how many CCR divers have done or keep in their bag of skills the ability to drive the unit O2 manually through switching the O2 cylinder on and off under water - Eg for a stuck solenoid
Understand the need to do it by some to get home but that's what the bailout is meant for too, but to be skilled to do it at depth you must practice.

Easier to have a 1L of O2 on unit with a small 1st stage & APD hose & add via MAV with inboard O2 turned off. If you empty that (unlikely) you can open/close inboard O2 whilst on deco which is a lot easier!

[weazelz]

Steve you don't need heat. I remember my old lecturer explaining Oxygen combustion when I was a lad and it was better than a magic show. He took an oily rag and put it on the bench then he opened the O2 on the welding torch and put it under the rag. Within a minute there was spontaneous combustion

you do need heat. the source of the ignition was heat caused by adiabatic compression where the high-speed stream of o2 hits the rag. this is why o2 valves should be opened *slowly*, to minimize the speed of the gas flow. o2 doesn't cause things to spontaneously combust without an ignition source

[SilentDiver]

Easier to have a 1L of O2 on unit with a small 1st stage & APD hose & add via MAV with inboard O2 turned off. If you empty that (unlikely) you can open/close inboard O2 whilst on deco which is a lot easier!

That is the next thing on my list to add to my unit.

Going to have a 1Ltr steel on each side one for suit inflate and one for off-board O2.

[Mark Rowe]

Easier to have a 1L of O2 on unit with a small 1st stage & APD hose & add via MAV with inboard O2 turned off. If you empty that (unlikely) you can open/close inboard O2 whilst on deco which is a lot easier!

Agreed but that's not how the manufacture designed it - wonder how many dive their unit as built and have feathering the O2 valve in their bag of "I will fly the unit manually when it breaks" tricks.
I learnt the skill on my vision course but not sure how much I would use it after seen the pics and remembering to slowly open the valve when underwater.

[gobfish1]

Easier to have a 1L of O2 on unit with a small 1st stage & APD hose & add via MAV with inboard O2 turned off. If you empty that (unlikely) you can open/close inboard O2 whilst on deco which is a lot easier!

i went with a 2l for just that, (My old 1.5 ali for suit feed, is much the same as the 2l , so it seemed to even out ,)
was going to go with 1l size ,

my thinking was if im going to put a 2nd o2 on may as well go with the 2l, add it to my inboard 3l and iv got a usable amount of oc as well , maybe 800L plus at 6m / 3m , 40 mins no bother. sort of kill two birds with the one stone

id prob call the dive if i had to use the in board valve to keep SP , with 2nd cylinder and MAV, im happy to keep on going ,

[Paulo]

That is the next thing on my list to add to my unit.

Going to have a 1Ltr steel on each side one for suit inflate and one for off-board O2.

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway

[the diving tiler]

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway




The is a chap who done this on the Lusitania a couple years back, look it up on the irish tec site think there is a story on it. :x:

[SoggyBottoms]

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway

this isn't well thought out chap
have another think about your idea


Sent from my iPad using Tapatalk HD

[Paulo]

The is a chap who done this on the Lusitania a couple years back, look it up on the irish tec site think there is a story on it. :x:

thought that the reason behind that was to do with a chemical heating pack he as using to stay warm?

[the diving tiler]

thought that the reason behind that was to do with a chemical heating pack he as using to stay warm?


And I think 60% o2 plumbed into the suit :(

[DiverMike]

I'm thinking of having off board O2 like suggested. Is 1l enough? I'm thinking steel as my Ali suit 1.5l inflate bottle is huge.

[JPTaylor]

Most dives I use 50 bar from a 3L, so 150 bar of O2. Most is used during the ascent, to maintain SP. So a 1L @ 200 bar should to enough & you still have access to O2 left in in-board via feathering valve. Doing O2 RB this was isn't that bad, that's how basic military O2 sets work!

You can also use your deco bailout to drive unit at depth if suitable hose fitted, even 50%.

[gobfish1]

I'm thinking of having off board O2 like suggested. Is 1l enough? I'm thinking steel as my Ali suit 1.5l inflate bottle is huge.

to run your breather/ bail out , Yes , to run a 3hr dive i norm use 50 to 80 bar ,, but i do piss away a fair bit of o2 whan on deco and comming up from 21m

on a 1l id need to keep my eye on it, (IF id started to use it at the beginng of my dive ,)

[Major Clanger]

On my Mod 2 and a bit, we had a go at taking the MAV hose from one diver and connecting it to the MAV of their buddy to share O2. Do-able as a last ditch but tricky.

[gobfish1]

On my Mod 2 and a bit, we had a go at taking the MAV hose from one diver and connecting it to the MAV of their buddy to share O2. Do-able as a last ditch but tricky.

id rather not get in to faff mode on a dive , good stocking fillers for mod2, but not for me,

[Major Clanger]

id rather not get in to faff mode on a dive , good stocking fillers for mod2, but not for me,

Me neither gobbers but if it was my only option to get a squirt of the happy juice then what's yours becomes mine :)

[Garf]

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway

So you have a source of heat (you), fuel( your clothing) and pure Oxygen. You also have potential static electricity discharges. Precisely how O2 clean are you? One of those things you'd probably get away with for your entire diving career, but if you didn't it would be very nasty. Then then get out of your kit and walk around a bunch of smoking divers in flammable clothes still retaining higher than normal levels of O2.

Then you get into the whole IBCD / Skin bend debate.

You're right. What could possibly go wrong :)

[Major Clanger]

... if suitable hose fitted, even 50%.

Good for maintaining set point but could make a bastard of you and your computer's deco calculations if deep with a high helium mix in the dil unless you switch the computer and don't mind that giddy feeling for a bit. Think I'd rather bail.

[gobfish1]

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway

its just a arse about tit way of trying to solve a problem you May have , Giving your self a problem on all your dives ,

[jamesp]

I am sure there is a reason not to but .... could you use o2 in your suit inflate (1L, not going to break the bank) and in the event of an O2 issue you could run the unit off of your suit inflate bottle? You are going to ascent straight away anyway so you are only going to be dumping from the suit anyway

Dont fart.

[weazelz]

So you have a source of heat (you), fuel( your clothing) and pure Oxygen

I'm not a chemist/physicist, but honestly, do you think body temperature, even under a few bar of pressure gets anywhere near the ignition point for anything in your suit, even in an oxygen-rich environment?


You also have potential static electricity discharges. Precisely how O2 clean are you? One of those things you'd probably get away with for your entire diving career, but if you didn't it would be very nasty. Then then get out of your kit and walk around a bunch of smoking divers in flammable clothes still retaining higher than normal levels of O2

I'll go along with this, for the sake of argument. at best, you're going to get a bit of a "whoomf" which might inflate, or maybe burst your suit with the produced co2, using up the available o2, but unless you're blasting additional gas - ie some %age of o2 - into the suit, then that's the end of it. you'll be under water - what's the worst that could happen?

in every normal situation [1], you *cannot* make fire without fuel, o2 & heat. if you could guarantee a *really* slow fill, to eliminate adiabatic heating, then you could stick a litre of petrol in a tank & fill it with o2

oxygen fires are only oxygen fires when there's a sustained source of oxygen. if you've ever used oxy-acetylene, then you'll know that the steel-melting, ultra-hot blue flame (with the o2 on), turns into a smoky bunsen burner (with the air hole closed) flame with the o2 off

where's NigelH when you need him?

[1] interestingly, certain types of coal, under certain circumstances, *will* spontaneously combust when exposed to oxygen, although it would seem that 21% will do:

Spontaneous combustion - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Spontaneous_combustion#Affected_materials)

[Garf]

As I said it's all very unlikely tbh, if we agree that the risk of a fire in increasing using a high percentage O2, then why take the risk when the consequences could be unpleasant. you say "could burst your drysuit". That's could be a disaster and frankly I'd rather avoid it.

[weazelz]

As I said it's all very unlikely tbh, if we agree that the risk of a fire in increasing using a high percentage O2, then why take the risk when the consequences could be unpleasant. you say "could burst your drysuit". That's could be a disaster and frankly I'd rather avoid it.

in truth, a sudden over-pressure in a suit would likely be vented by the dump and/or neck/wrist seals well before the suit itself would burst. however, intuitively, high %-age o2 as a suit gas would seem undesirable

anyway, getting back OT, I am rather surprised that Mr TW, as an experienced CCR instructor, & hence 100% o2 handler, is apparently unaware of the causes of o2 fires - I'm sure I was taught this on my PADI Nitrox blending course, TDI Advanced Nitrox course (100%), BSAC Advanced Nitrox course (50%) & possibly even my PADI Nitrox course (40%)

[GLOC]

Andy, the last comment was a bit harsh re: knowing sources/components of fire. Most people think of heat as directly applied heat as opposed to kinetic energy from gas/particles slowing down from high speed.

Regards

[bottle maker]

Going a bit off topic and possibly worth a thread on its own.

I used 34% back gas as suit inflation after that days diving when I took my suit off all the seals had gone slimey. It was as if petrol had got on the rubber. I contacted the suit maker who said wash it with soapy water. after that the suit started leaking and was eventually changed FOC by the manufacturer. I wonder if this is a common cause of suit seam failures with the glue reacting to high PPO2's. Certainly the manufacturer did not disagree with me when I suggested this was a possible reason for my suit falling apart.

Graham.

[Ron MacRae]

Going a bit off topic and possibly worth a thread on its own.

I used 34% back gas as suit inflation after that days diving when I took my suit off all the seals had gone slimey. It was as if petrol had got on the rubber. I contacted the suit maker who said wash it with soapy water. after that the suit started leaking and was eventually changed FOC by the manufacturer. I wonder if this is a common cause of suit seam failures with the glue reacting to high PPO2's. Certainly the manufacturer did not disagree with me when I suggested this was a possible reason for my suit falling apart.

Graham.

No. We all do that. Last time out, due to the LDS being a bunch of muppets, I went diving with backgas at 40%. Suit was/is fine. Nitrox shouldn't be an issue. Also any other contamenant in the fill that would do that to your suit would do bad things to your lungs too.

Ron.

[Kermit]

if you've ever used oxy-acetylene, then you'll know that the steel-melting, ultra-hot blue flame (with the o2 on), turns into a smoky bunsen burner (with the air hole closed) flame with the o2 off

(pedant mode on) An oxy-acetelene torch BURNS the steel with a central jet of pure O2. It dosn't melt it. The outside flame is only there to heat the steel up a bit. (pedant mode off)

[gobfish1]

id use o2 to feed my suit if i needed to . and have used it , (When iv fooked up) All kitted up and ready to go, ie no whip on my 50% cylinder,
o2 or 18/45 i went with o2 , as iv already done the he in the suit .. lol not a good plan . on a long ish dive ,

think the piont was . why plan for a ccr problem that may never happed , by having o2 feed your suit for all your dives ,

if your going to solve a problem, solve the problem ,

should be no need at all to use o2 for your suit feed when diving ccr ,,

i can think of 3 other ways to solve the stuck solenoid problem .

out of the 3, only 1 gives me a problem free return , and even a bonus,

none of the above 3 have feek all to do with my suit feed , why would i want to piss about with something that work,s all ready , and have 4 ways to back that up ,

[ebt]

Jesus. Im in the old farts corner with gobby ;)

The gas I'd try to avoid squirting into a drysuit is helium, but only because I dont fancy getting chilly (I've done it before). I wouldnt put O2 in out of choice, but not from any great risk/concern other than the wallet impact and maybe thoughts of aging the glues used in the suit.

I certainly wouldnt worry about static electricity inside a 'dry' suit, its humid as hell in there.

[Mike_123]

How many carry their electronic car-key in their drysuit pocket ? I usually do - there's a potential heat source.

Several have posted about regularly taking their mobile phones with them - lots of potential there.

I chatted with a couple of guys at Eurotek that were talking about using O2 for drysuit inflation while wearing home-made heated vests. No thanks ! Same goes for the any electrically heated gear imo.


. . . . at best, you're going to get a bit of a "whoomf" . . . . you'll be under water - what's the worst that could happen?
I'm struggling to imagine how even the briefest of oxygen fires inside your drysuit could be a trivial problem.

Oxygen flash fire. - YouTube (http://youtu.be/2wMRL2bVKc4)

[Scuba steve]

When doing deep trimix i feed the suit off my 50% . But i have a spare whip on my 100% just incase

[weazelz]

Andy, the last comment was a bit harsh re: knowing sources/components of fire. Most people think of heat as directly applied heat as opposed to kinetic energy from gas/particles slowing down from high speed

Gareth, I thought I was being rather mild - a CCR Instructor should not be "most people" in terms of o2 handling

I know Simon is well-liked & well-respected - both generally & by some good friends of mine - but for him to perpetuate this misinformation/FUD from that position does no-one any favours

Simon - apologies for any offense

Hebails - buy the man a beer from me when you see him; I'll get you one back when I see you next

[weazelz]

(pedant mode on) An oxy-acetelene torch BURNS the steel with a central jet of pure O2. It dosn't melt it. The outside flame is only there to heat the steel up a bit. (pedant mode off)

<pedant>
I'm sure you're right for OA cutting. I was thinking of OA welding, which is melting
</pedant>

[SilentDiver]

I'm thinking of having off board O2 like suggested. Is 1l enough? I'm thinking steel as my Ali suit 1.5l inflate bottle is huge.

Judging by what I use from my Ali 1.5Ltr suit inflate on an average dive and for what I am going to be doing this year a 1Ltr each side will be plenty for suit inflate and off-board O2. I am not going to be doing anything deep, dark or scary until towards the end of the year as I need to get dived up again after my surgery enforced lay off but am thinking that this this may be the ideal time to play with different setups.

And I am going to be getting steel cylinders 1Ltr each side to keep trim/balance, (that and they can be over filled a little bit without too much worry).

The only spanner in the works I can see is my torch battery, (metalsub), upsetting the balance, which is why I am selling it and going back to my old Greenforce HID100 and F2 battery.

[Simon TW]

you do need heat. the source of the ignition was heat caused by adiabatic compression where the high-speed stream of o2 hits the rag. this is why o2 valves should be opened *slowly*, to minimize the speed of the gas flow. o2 doesn't cause things to spontaneously combust without an ignition source


Sorry Andy but I don't agree, I can see that you want a ruck. Sorry it's taken time to respond, I've been rather busy in the UK with shitty internet connection.

It couldn't have been adiabatic compression. The rag that he used was one that was used in all engineering companies in the 70s. They were even laundered. Heavy red cotton mesh.

Maybe have another read of what I've written then give the "scientific explanation" (as requested) as to where the heat is in the combustion of O2 where hydrocarbons are present.





Why you don't need an additional heat is that the hydrocarbon molecules get exited in the presence of O2 and rub together causing friction and the friction produces heat which then results in combustion.

Sits back and waits for a scientific explanation.

Again sits back and waits for scientific explanation (good starting point is exothermic reaction, not that easy to explain really).

[Simon TW]

anyway, getting back OT, I am rather surprised that Mr TW, as an experienced CCR instructor, & hence 100% o2 handler, is apparently unaware of the causes of o2 fires - I'm sure I was taught this on my PADI Nitrox blending course, TDI Advanced Nitrox course (100%), BSAC Advanced Nitrox course (50%) & possibly even my PADI Nitrox course (40%)

Wind your neck in, sober up and re read the thread. Then ask all of those instructors who taught you above why they didn't explain hydrocarbons.

[Kermit]

Let me try and put this in a way that even little furry things can understand.

Take a piece of clean steel, sit it on a bench in 1 atm of air and, slowly, it will rust. Rusting = oxydization. Oxydization = burning. The lump of steel is slowly burning and turning into rust.

Now take the same piece is steel, heat it to red hot and blow 100% O2 over it and it burns. It's EXACTLY the same chemical process, just a lot quicker.

Take a mound of coal. It is gradually oxidizing its carbon. Even at room temperature. However, this oxidization (rusting, burning whatever you want to call it) is happening very slowly and the small amount of heat it gives off dissipates into the rest of the coal and the air.

In certain circumstances the dissipation of this small amount of heat is slower than its production and the temperature of the coal rises slightly. This causes the coal to oxidize a little faster. A little more heat is produced and thus a chain reaction is created. Sometimes ending with flames etc..

Pure O2 is a better oxidizer than air. High pressure O2 even better. There are many circumstances where an ignition source or external source of heat is NOT required for combustion. A fuel is though. However, in the presence of pure O2 virtually any material becomes a fuel. Hydrocarbons especially.

HTH
Ian

[Simon TW]

Let me try and put this in a way that even little furry things can understand.

Take a piece of clean steel, sit it on a bench in 1 atm of air and, slowly, it will rust. Rusting = oxydization. Oxydization = burning. The lump of steel is slowly burning and turning into rust.

Now take the same piece is steel, heat it to red hot and blow 100% O2 over it and it burns. It's EXACTLY the same chemical process, just a lot quicker.

Take a mound of coal. It is gradually oxidizing its carbon. Even at room temperature. However, this oxidization (rusting, burning whatever you want to call it) is happening very slowly and the small amount of heat it gives off dissipates into the rest of the coal and the air.

In certain circumstances the dissipation of this small amount of heat is slower than its production and the temperature of the coal rises slightly. This causes the coal to oxidize a little faster. A little more heat is produced and thus a chain reaction is created. Sometimes ending with flames etc..

Pure O2 is a better oxidizer than air. High pressure O2 even better. There are many circumstances where an ignition source or external source of heat is NOT required for combustion. A fuel is though. However, in the presence of pure O2 virtually any material becomes a fuel. Hydrocarbons especially.

HTH
Ian


Thank you.

[weazelz]

However, in the presence of pure O2 virtually any material becomes a fuel. Hydrocarbons especially

indeed

if you add heat

NDY - I am disappointed in you

[MikeF]

a ittle sobering reading on whet happens when you add hydrocarbon contamination (oily hand) to pure O2 (leaky hose)

http://www.marinesafetyforum.org/upload-files/safetyalerts/msf-safety-flash-09.02.pdf

[Stan]

a ittle sobering reading on whet happens when you add hydrocarbon contamination (oily hand) to pure O2 (leaky hose)

http://www.marinesafetyforum.org/upload-files/safetyalerts/msf-safety-flash-09.02.pdf

That has really made me re-consider LP side O2. I would imagine the results if he were clad in rubber-based materials, all glued together (can't imagine that happening though eh??), could have been horrendous.

Out of interest, what provided the source of ignition? Apologies if I missed it while skim reading and mainly looking at the pictures!

Thanks for posting.

[GLOC]

Out of interest, what provided the source of ignition? Apologies if I missed it while skim reading and mainly looking at the pictures!

Thanks for posting.
The fire triangle is a simplistic representation of what is required to work at 1 atm.

Fire is a chemical reaction which requires a certain amount of energy to start/continue. That energy may be present from 20C air temperatures.

As I just read somewhere, you can explosively combined F2 and H2 without O2 being present at -180C. Thermite doesn't require O2 to be present.

By having pure O2 present (an oxidising agent), you can reduce the ignition temperatures significantly.

There is a substance called BOL IR which is a metallic compound which reacts with air to burn (pyrophoric). Think magnesium on steroids. There is no ignition source present, it just burns in the air using the 21% O2 present. http://www.fas.org/man/dod-101/sys/ac/equip/mju-52.htm

Regards



Sent from my iPad using Tapatalk HD

[weazelz]

[QUOTE=GLOC;69665]The fire triangle is a simplistic representation of what is required to work at 1 atm.

Fire is a chemical reaction which requires a certain amount of energy to start/continue. That energy may be present from 20C air temperatures.

As I just read somewhere, you can explosively combined F2 and H2 without O2 being present at -180C. Thermite doesn't require O2 to be present.

By having pure O2 present (an oxidising agent), you can reduce the ignition temperatures significantly.

There is a substance called BOL IR which is a metallic compound which reacts with air to burn (pyrophoric). Think magnesium on steroids. There is no ignition source present, it just burns in the air using the 21% O2 present. MJU-52/B BOL-IR decoy (http://www.fas.org/man/dod-101/sys/ac/equip/mju-52.htm)

well wiki'd

Thermite: Thermite - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Thermite)

thermite doesn't require O2 - BECAUSE IT'S IN THE OTHER COMPOUND

didn't you do this shit in chemistry age 13?

[GLOC]

Thanks Andy. And pyrophoric materials? How do they work without ignition?

Regards

[weazelz]

Thanks Andy. And pyrophoric materials? How do they work without ignition?


you have white phosphorus regs?

[GLOC]

No, the assumption that is being made is that an ignition source is required to start a fire. It is not.

Regards

[GLOC]

More here on the subject of spontaneous combustion

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120003032_2012002559.pdf

Regards

[weazelz]

I give up

I will maintain that for materials used in mainstream diving equipment - ie brass & stainless steel - they do not spontaneously combust - as indeed do not vaselin'd BASC 'tashes at 3ATA of O2 (I blame Chasey for that one)

honestly - regulate yourselves before someone else does [Janos bait 101]

[Major Clanger]

Iain has an interesting take on this and why black soot like particles are found in cylinders during cleaning but he's not migrated and it's over the other place. Reckons that it happens more often than we know on a micro level within our gear. Trouble is, he then goes on to sweat the detail and annoy everyone.

[GLOC]

I know brass and steel don't spontaneously combust!

If oil and grease aren't an issue with high pressure O2, then why is there all the advice about not mixing the 2? I'm not talking about just inside the diving industry.

Genuinely interested.

Regards

[GLOC]

Andy,

This is what I think happens. As you seem so knowledgeable in this area, please correct me I am wrong.

Certain base assumptions/comments:

When a substance oxidises (rust is oxidisation, but a slow pace) a chemical reaction takes place which generates heat.
For combustion to occur there needs to be heat, fuel and oxygen
For sustained combustion there needs to be significant fuel, continued O2 and sufficient heat to support the combustion

Using a pure O2 scuba diving environment, there is O2, should be no fuel (hydrocarbons) and no heat. The regulator is opened and O2 flows through the system. The gas is restricted as it moves and causes friction. In the case of a presence of an oxidising fuel (oil/grease), this oxidises and will raise the local temperature. If that temperature rises enough to allow spontaneous combustion of ANY fuels present, an ignition will occur. If there is enough fuel to continue the combustion and raise the temperature higher, other items may become fuel because their ignition temperatures have been reached.

In the case of the report above, the O2 escaping produced a situation where enough fuel (grease/oil) was being oxidised to raise the local temperature to ignite the fuel, once that happens, you have a sustainable fire.

No ignition source has been introduced and yet you have a sustainable fire because you have fuel, heat and oxygen.

Regards

[Fernando. Rueda]

Hi Guys,

Just read this and though I would let you know that my two year old inspiration Rebreather caught a light exactly the same way last 28th June 2019 whilst running the start up procedure, on opening the O2 ads I have done 100's of times, within a second it caught on fire I wasn't so lucky and sustained some burns to my left hand and face which are busy being treated specialist burn doctors.

The cause is still completely unknown we suspect maybe a ~HP hose ruptured but nothing conclusive as yet the back of the first stage blew off as well, I can categorically say that if it had been strapped toy back when opening the O2 the outcome would have been horrific

I can categorically advice NEVER to open your O2 whilst the machine is strapped to one's back

i am not very affair with these posts but would like to share some photographs and really hope we can learn something from this

[Darren A]

Hi Guys,

Just read this and though I would let you know that my two year old inspiration Rebreather caught a light exactly the same way last 28th June 2019 whilst running the start up procedure, on opening the O2 ads I have done 100's of times, within a second it caught on fire I wasn't so lucky and sustained some burns to my left hand and face which are busy being treated specialist burn doctors.

The cause is still completely unknown we suspect maybe a ~HP hose ruptured but nothing conclusive as yet the back of the first stage blew off as well, I can categorically say that if it had been strapped toy back when opening the O2 the outcome would have been horrific

I can categorically advice NEVER to open your O2 whilst the machine is strapped to one's back

i am not very affair with these posts but would like to share some photographs and really hope we can learn something from this

Blimey, I know these things try and kill you every dive, I didn’t realise they try and cremate you as well. Glad you were not hurt more badly.

No doubt AP will charge you to repair the unit.