Don't store Oxygen and Acetylene together in an LPG bottle and attempt to weld

[vk6zgo]

Not a mining town. A friend’s father was into collecting mining lamps and we nicked his carbide stash. Also found the local outdoors store (army and navy surplus) at the time stocked it for cavers. Could buy a cool Kg of it for £2.

I would have probably hung out with your dad

Only if you are a centenarian!
I was telling that story to a young EE who was originally from Vietnam, & he topped it with the way him & his mates used to find unused munitions from the Vietnam War (usually rifle & machine gun cartridges), get them open, & use the guts to make very potent fireworks.

Amazingly, none of the silly buggers managed to kill themselves!

Back to topic.
Thousands of home handy persons owned oxy-acetylene equipment over decades, with a vanishingly small percentage coming to grief.

When I first got an "oxy set", I was a complete "oxy moron" for about a year, finding hundreds of jobs for it, then my use of the gear diminished, till I found I was paying a not inconsiderable rental fee for bottles which I wasn't using, so I sent them back, & packed up the gauges torches & hoses.

They are still there,in good condition, & I've been tempted to get some "non-rental" bottles & do some jobs around the house.

As with most such things, I go & have a "lie down" till the feeling goes away!

[Psi]

I use to play with carbide crystals when I was a kid.

Same, growing up we had a welding plant that used carbide and water instead of a acetylene gas tank.
To keep it feed we had a large plastic drum of carbide in the garage for over 20 years. And this was in a residential city neighborhood 
I think we only ever used 1/2 the drum in the 20+years before we sold the whole thing.

I once detonated a few granules of carbide in a 2L coke bottle with some water and spark igniter.  It made a dry ice bomb look like a Christmas cracker/bon bon

I shudder to think what size explosion could have been achieved had the entire drum been converted and detonated at once.

[TerraHertz]

Yes, but that is about flow velocity and not pressure. Also, when you have a fuel/oxygen mixture the speed of a moving flame front can be much faster than the flow velocity in a tube. That's why a normal gas torch mixes fuel and oxygen right at the tip.

Uh, no. A normal oxy welding torch mixes the gasses right after the valves in the handle. Yes, the mix present in the channel from there to the tip IS explosive. If you sequence the lighting right the flame does not burn back into the torch because the velocity of flame propagation is slower than the gas velocity in the fine hole at the tip. Only as the gas expands and slows down on emerging can the flame front keep up with the flow. If you turn the gas flow up too high, you can blow the flame away from the tip.

Of course if you turn the valves down too far, you get a nice POP as the gas mix in the torch detonates. And if you reeeely fuck up, you can blow up the hoses. (Never done that myself.) I don't even want to think about what it would take to get a mixed gas back into either of the cylinders.

Part of the art of oxy welding is adjusting the gas rate and proportion to achieve the desired state of oxidizing or reducing chemistry at the flame tip. Recognizable from the visual characteristics of the flame.

The oxy cutting tip has a ring of fine jets carrying oxy-acet mix gas. These small flames are used to heat the target steel to red heat. Then the central pure oxygen jet is turned on. The hot steel catches fire in the oxygen, and that is a VERY exothermic reaction. It's the burning steel that melts itself. The oxygen jet is forceful enough to blow the resulting iron oxide slag out of the way.

Heh. Someday I'd like to try using a thermal lance. Those things rock.

There is also the situation that the flow is controlled by some kind of lever at the torch end to control the flame size. For a given flame size the flow velocity in the tube is slower when the pressure is higher because for a given mass flow the product of velocity and density is constant.

True that when the velocity slows close to zero the possibility of flash back is much higher, but I predict the explosion would happen long before then.

It seems you've never used an oxy torch.  If you're in Sydney some time, drop me a line and you can have a go.

The really crucial thing is that you never, ever mix oxygen and a flammable material in a confined space. Ever.

Except:
1. When you want to blow something up. Like unwanted ants nests. Woohoo!
2. In the end of an ordinary oxy torch. It's a small space and the metal is thick enough to take the bang if you mess up.

[SparkyFX]

if the man did this and is a welder I am convinced he was extremely intoxicated

Not only that... it might also be worth noting that burn gases and inert gases use different threads on the fittings, so you can not accidentially connect them the wrong way or at all.

Acetylene bottles/pressure regulators and maybe the torches have a left hand thread (the nut is marked with indents), oxygen or argon/co2 have right hand threads.

That almost requires intentional wrongdoing, either while connecting all components, during filling or during use.

An oxy acetylene rig always requires flashback arrestors, just because at some point the bottles will be empty and pressure and flow rates will not be stable in the system.

[Stray Electron]

It's lucky that Swaziland changed its name this year then...   "Mom, I went to get the money out of the Swiss bank and it's really hot here, there's this weird black and white striped horse wandering down the street, there's a heck of a lot of black folks here, even more than in Baltimore, and that Swedish language course I took is useless, nobody understands a word I say!"

   Funniest post of the day! 

[vk6zgo]

if the man did this and is a welder I am convinced he was extremely intoxicated

Not only that... it might also be worth noting that burn gases and inert gases use different threads on the fittings, so you can not accidentially connect them the wrong way or at all.

Acetylene bottles/pressure regulators and maybe the torches have a left hand thread (the nut is marked with indents), oxygen or argon/co2 have right hand threads.

That almost requires intentional wrongdoing, either while connecting all components, during filling or during use.

An oxy acetylene rig always requires flashback arrestors, just because at some point the bottles will be empty and pressure and flow rates will not be stable in the system.

It is only in relatively recent years that flashback arresters have been available.
In the previous eighty to ninety or so years, people got along without them, with the accident rate still being miniscule.
I'm not deriding them, we should have them, but it isn't quite as black & white as "always".
When the bottles become almost empty, it is evident, because it is not possible to maintain a stable flame.

[SparkyFX]

It is only in relatively recent years that flashback arresters have been available.

It was teached some 22 years ago in welding classes i attended to have them in place - because they are a good idea for protection. Maybe we aren´t talking about the same thing. The devices i talk about pose an increase in cross sectional area, held separate by two paper-like diaphragms. Should back-pressure or a flame come backwards, this will make the diaphragm close the supply. They are ridiculously cheap, i even got some in my kid-size oxy torch "rig".

The other remarkable protection was to not lower the temperature required for an ignition by improperly lubricating oxygen supply fittings (oils and grease and such).

[Cerebus]

It is only in relatively recent years that flashback arresters have been available.

I knew you were old mate, but I didn't realise that you were so old that the nineteenth century was "relatively recent years" from your perspective.

Nineteenth century examples of dry and wet types of flashback arrestors, for use with oxy-hydrogen.:

[HighVoltage]

In our town in my childhood, a "smart" plumber wanted to show his coworkers, how oxygen and acetylene can make a nice little explosion.
He filled an air balloon with a perfect mixture until it almost popped.
Then he ignited the balloon with a cigarette lighter.

He went to the hospital with bad burns in his face and him and all his co workers had popped eardrums.
Because of his stupidity, the German government closed his business.

Some people are just plain stupid!

[mzzj]

Uh, no. A normal oxy welding torch mixes the gasses right after the valves in the handle. Yes, the mix present in the channel from there to the tip IS explosive. If you sequence the lighting right the flame does not burn back into the torch because the velocity of flame propagation is slower than the gas velocity in the fine hole at the tip. Only as the gas expands and slows down on emerging can the flame front keep up with the flow. If you turn the gas flow up too high, you can blow the flame away from the tip.

And oxy-hydrogen torches use pre-mix even in the hose (and some smallish volume inside the electrolysis chambers and scrubbers)
Low volume, low pressure and "explosion" safe design being the key points there..

(btw: oxy-acetylene mix has about 4 times higher energy density than oxy-hydrogen)

[vk6zgo]

It is only in relatively recent years that flashback arresters have been available.

It was teached some 22 years ago in welding classes i attended to have them in place - because they are a good idea for protection. Maybe we aren´t talking about the same thing. The devices i talk about pose an increase in cross sectional area, held separate by two paper-like diaphragms. Should back-pressure or a flame come backwards, this will make the diaphragm close the supply. They are ridiculously cheap, i even got some in my kid-size oxy torch "rig".

The other remarkable protection was to not lower the temperature required for an ignition by improperly lubricating oxygen supply fittings (oils and grease and such).

The things I am referring to screw onto the gauge or handset instead of the hose, then the hose screws on to that, rather like an inline attenuator with "N" connectors.
Normally they use them at both ends of each hose.

[taydin]

I like the turn of the century design where the gases go through a water tank That seems like an ultra reliable way of stopping a flame going back to the cylinder.

The design that I'm using at the moment has steel wool inside of it and a drop of solder. A flame supposedly causes the solder to melt and set a spring free, which then goes and closes the end.



Comparing these two designs, I find the water method to be much more reliable.

[vk6zgo]

It is only in relatively recent years that flashback arresters have been available.

I knew you were old mate, but I didn't realise that you were so old that the nineteenth century was "relatively recent years" from your perspective.

Nineteenth century examples of dry and wet types of flashback arrestors, for use with oxy-hydrogen.:

Note that the examples you show are for oxy/hydrogen not oxy/acetylene.

This is what modern ones look like:-
https://www.weldclass.com.au/blog/16-flashback-arrestors-your-questions-answered

The Australian Standard referred to in the linked article only dates from around 1984, so I was correct in saying "relatively recent years"
They were certainly not supplied with the oxy set I bought in the late 1980s to replace an earlier one that was stolen, so were not mandatory then.

[Cerebus]

It is only in relatively recent years that flashback arresters have been available.

I knew you were old mate, but I didn't realise that you were so old that the nineteenth century was "relatively recent years" from your perspective.

Nineteenth century examples of dry and wet types of flashback arrestors, for use with oxy-hydrogen.:

Note that the examples you show are for oxy/hydrogen not oxy/acetylene.

This is what modern ones look like:-
https://www.weldclass.com.au/blog/16-flashback-arrestors-your-questions-answered

The Australian Standard referred to in the linked article only dates from around 1984, so I was correct in saying "relatively recent years"
They were certainly not supplied with the oxy set I bought in the late 1980s to replace an earlier one that was stolen, so were not mandatory then.

Yeah but you said "relatively recent years ... available", not "mandatory". More than a century, given the Industrial Revolution's around 200 odd years old, is only going to be "relatively recent" to someone with a very long lifetime. Admit it, you're the Count de Saint Germain and slipped up, thereby outing yourself.

[jmelson]

Nobody stores acetylene in liquid/or gaseus form in pressurized cylinders.

Do you have a typo, there?
Commercial acetylene tanks hold acetylene dissolved in acetone, and that is stored in fuller's earth.  The pressure in the bottles is relatively low.


Jon

[m3vuv]

years ago i was messing about with oxy accetalyne,i lit the welding torch adjusted it for a neutral flame then stubbed the torch out leaving the gas comming out of the nozzle,i got a bin bag and held it over the nozzle untill it was inflated,i used masking tape to seal it and took it to the bottom of the garden,luckily i lived out in the sticks at the time and didnt have neibours,i put the bag at the bottom of the garden about 50yds from the house and workshop,i used a piece of masking tape for a fuze lit it and stood just in front of the workshop,after about 5 seconds there was what i can only describe as an explosion,i felt the shockwave (nearly knocked me over),i heard a noise from the workshop,went in and found a load of tins of paint etc had came off a shelf on the gable end,the shock must of rattled the garage wall,it was block built as well,the bin liner wasnt either fully inflated,if he had a proper ratio mix under pressure,im supprised there was anything left of him!!,i think if i remember as an explosive its not far behind c4 scarey stuff!!!.

[amyk]

It is only in relatively recent years that flashback arresters have been available.

I knew you were old mate, but I didn't realise that you were so old that the nineteenth century was "relatively recent years" from your perspective.

Nineteenth century examples of dry and wet types of flashback arrestors, for use with oxy-hydrogen.:

Note that the examples you show are for oxy/hydrogen not oxy/acetylene.

Page 20 of  this century old book shows the same water-chamber type for acetylene.

[duak]

I was, I think fourteen years old when I got a lead-acid motorcycle battery.  It had a nifty 6 mm diameter plastic tube to vent hydrogen released during charging.  I cranked up the charger from 6 V to 12 V to get some real electrolysis happening.  I figured I'd get a nice little flame when I lit the hydrogen coming out of the tube.

Guess what happened next?

There was a good POP, part of the side of the battery was shot across the room and the battery moved the other way about 20 cm or so.  Acid was sprayed across the counter fortunately away from me.

My sister has alway said that if we didn't have bad luck we'd have no luck at all.  I'd disagree in this case, it was bad news for the battery but I could have got acid or debris in my eyes.  I'll take that as good luck.

Cheers,

[alpher]

Nobody stores acetylene in liquid/or gaseus form in pressurized cylinders.

Do you have a typo, there?
Commercial acetylene tanks hold acetylene dissolved in acetone, and that is stored in fuller's earth.  The pressure in the bottles is relatively low.


Jon

I don't see any typos there, do you?

[amyk]

I was, I think fourteen years old when I got a lead-acid motorcycle battery.  It had a nifty 6 mm diameter plastic tube to vent hydrogen released during charging.  I cranked up the charger from 6 V to 12 V to get some real electrolysis happening.  I figured I'd get a nice little flame when I lit the hydrogen coming out of the tube.

Guess what happened next?

There was a good POP, part of the side of the battery was shot across the room and the battery moved the other way about 20 cm or so.  Acid was sprayed across the counter fortunately away from me.

My sister has alway said that if we didn't have bad luck we'd have no luck at all.  I'd disagree in this case, it was bad news for the battery but I could have got acid or debris in my eyes.  I'll take that as good luck.

Cheers,

Now consider that hydrogen is actually rather mild in terms of explosive force, compared to acetylene or even propane...

Hydrogen:


Propane:


Acetylene:

[Mr. Scram]

Wasn't that last one the only one premixed with pure oxygen?

[duak]

I took my sons out to a day at the chem lab at one of the local universities where they did the balloon demos.  Hydrogen and hydrogen with air were pretty good - you didn't need hearing protection but it was a good idea.  Hydrogen and oxygen definitely needed hearing protection - it was a good thump in the chest.

Has anyone been to Top Fuel drag races where they use nitromethane as fuel for the cars?  Although I knew they would be LOUD, the first time I saw them I was surprised by the visceral thumping.  Rock concerts could very well be louder, but the impact is indescribable.  It almost seemed like the air became much more dense; like a liquid.

Gummi Bears in liquid oxygen burn almost as brightly as thermite.  I remember seeing a video by (I think) George Goble who got a charcoal brazier (Hibachi) ready in about two seconds flat by pouring a cup of liquid oxygen on the briquets.  Actually, almost all of the cast iron Hibachi burned leaving just the feet.

[drussell]

It is only in relatively recent years that flashback arresters have been available.
In the previous eighty to ninety or so years, people got along without them, with the accident rate still being miniscule.

I don't think that is quite true.  I remember seeing ones on the hoses of some very old rigs when I was a kid.  Plus, that 1916 book linked to earlier talks about early styles of torches that needed flame arresters, how they were constructed chambers with asbestos cloth layers interleaved with wire mesh, etc.

[tautech]

years ago i was messing about with oxy accetalyne,i lit the welding torch adjusted it for a neutral flame then stubbed the torch out leaving the gas comming out of the nozzle,i got a bin bag and held it over the nozzle untill it was inflated,i used masking tape to seal it and took it to the bottom of the garden,luckily i lived out in the sticks at the time and didnt have neibours,i put the bag at the bottom of the garden about 50yds from the house and workshop,i used a piece of masking tape for a fuze lit it and stood just in front of the workshop,after about 5 seconds there was what i can only describe as an explosion,i felt the shockwave (nearly knocked me over),i heard a noise from the workshop,went in and found a load of tins of paint etc had came off a shelf on the gable end,the shock must of rattled the garage wall,it was block built as well,the bin liner wasnt either fully inflated,if he had a proper ratio mix under pressure,im supprised there was anything left of him!!,i think if i remember as an explosive its not far behind c4 scarey stuff!!!.

The muggins that blew himself up lived ~15 mins drive away.
Yeah oxy sets are great tools and fun.....if you're bloody careful.
I got my first at 13 going 1/2 share with pop and had it for 40+ years before losing the lot in a shed fire. 
None of the bottles exploded but melted the fusible plugs on the taps and vented safely as their supposed to do.

Unlike some bigger bottles in a local workshop fire when I was a kid that popped and took a leg from each of two fireman fighting the blaze. The remains of those jagged exploded bottles are set as a monument to their efforts outside the Kumeu/Huapai volunteer fire station to this day.

Any compressed gas need be treated with respect !

Copied from a post I did a few years ago when not wanting to offer too much info in case some twit blows themselves up:

A neighbour every year at guy fawkes used to fill a bag with a oxy plant mix with a short length of fuse wire and a LONG lead to a car battery.

BOOM

Last one they did, I was driving ~2 Kms away and nearly shit my pants. 
Their 70 Yr old mum always watched, but that was the last one they did as it upset a few neighbours even though we live in a rural area. 
Good rural fun. 

Sadly their mum and one of the sons are no longer with us and both gone from natural causes. 

[tautech]

About things that go boom, couple of interesting vids in this thread:
https://www.eevblog.com/forum/beginners/will-this-work-fireworks-detonator/