What's The Safe Way to Cut Bottoms off Acetylene Tanks?

The best answer by jack of all trade

DANGER ! It is my understanding that a fully depressurized acetylene tank contains acetic acid or dimethyformadehyde. I am not a chemist and am unsure of the reaction, however I would never cut into an acetylene bottle, be it empty or full.

As I understand it (in my country), one does not actually buy acetylene bottles, but merely rents them and purchases the contents. This ensures maximum safety for all given the chemical energy in a bottle of acetylene.

That's news here. Acetone and kapok will certainly be present, both being flammable.

And those wind chime sticks of TNT next to the bug zapper would really set the room off.

Actually I had suggested the steel cut blades, but he did point out heat would still be generated.

The tanks are stuff he has around to mess with.

Overall I like the water fill or purge, then the cutting.

I really appreciate the suggestions. Whatever I will highly suggest water fill and then cut, and all such safety gear as glasses and not doing such stuff naked wearing flip flops.

Bobc, as ever a good sensible post.

Filling with water is always a good idea for any tank that once held any sort of fuel or gas........it purges and cools in one easy operation!!

Yeah, and that 14 foot blade would keep you away from the bottle a little bit <VBG>.

As they said in the sixty's RIGHT ON! But the acetylene tank may give that 1812 Overture affect. -- JHF

"Apparently Acetylene tanks are not just straight gas tanks but also contain a filler and possibly even Asbestos."

If this comes as a surprise to anyone, I'm surprised.

I hope you read Jack of all Trades link to Airgas. I have always heard that acetylene tanks have an absorbent line and a filler to absorb the acetylene. -- JHF

The safest way to cut the bottom off an acetylene tank would be to send it to a shop in another county or country and ask them to do it for you...

That is somewhat true cwarner7_11 for I did do work cutting up a couple of ships in Wilmington NC. I was in between film jobs. Pier over two guys died at similar work.[p[] One got a pipe thru his forehead and out the back of his brain on a kick back, and the other was split in half by a falling sheet of steel from a fraywire steel rope crane mishap.

Been down in the bottom of a ship where there is no, no, not any light at all sponging up kerosene and fuel oil.

The work went to India, where life was cheaper, after some of these events.

What class am I really?

P.S. I love you as I do others of the wise class.

Am from India. About 25 years backthere was a proposal to ship municipal garbage from the Big Apple to an unspoilt islnad in India, where a waste burning power plant would generate power. The unit was also to be paid USD4/ton for the job. I served on a committee to which this was referred for clearance. Rejected . Thankfully other states of India also rejected and we were spared becoming a garbage dump.

If the tank is full of water at the time of cutting and the top valve removed, there will be no explosion. Quantity of acetylene infiltrated into metal will be negligible, but a lot in the filler.

I was going to suggest that same thing, but felt my words might be offensive to some of our members. Out sourcing does have some merit at times. Nice reply.

there is moral revulsion to exploiting weaker economies (such as the workers in India) by passing a disproportionate burden of the world's hazardous waste (read for making chimes of all the things!) to a country and community simply because of its weaker economic stature. Americans and their idea of Basel! :)

Advise the friend not to do it, on grounds of safety to him/herself and anyone else in the neighbourhood. (S)He risks not being popular with life insurance companies.

Couldn't he alternatively go to someplace like the Huertgen Forest and dig up old, unexploded 88mm shells and cut them open with a torch? It would have to be safer.

Well Guys, I ended up advising my friend to get that Acetylene Tank back to whomever originally owned it. He ends up with all sorts of stuff in the course of his business selling Surplus.

It is funny that in fact actually more of my art, photographs primarily, have sold out of his place than the two or three galleries I've had stuff in.

What kills you sometimes as an artist is that if you can sell the work once, you know if it is reproduced, more would sell.

But back to the issue at hand. -It would appear that messing around with these tanks is fraught with many dangers. I was particularly swayed towards advising my friend to forget cutting the acetylene tank by the Air Products info, and the other link info.

As far as the Outsourcing of Scrapping Ships to India, well that is just a true thing.

Last I checked about 4 or 5 years ago, in the US it is about impossible to make any money scrapping a ship for the steel and what not due to the regulations. I have to admit it was one of the most dangerous jobs I ever had, and I feel as though I have some Street Cred with any worker anywhere in the world from having done it.

I'll tell you one rule to not ever violate should you ever find yourself on a dead ship.

Do not ever ever go below decks without a flashlight. Hell I'd about say never ever be below decks on any ship, live or dead without a flashlight after my experiences scrapping a ship.

I won't advise you about cutting so-called "empty tanks" but I will tell you that my neighbor was almost killed while welding an "empty tank." It exploded on him, crippling him for life. And while I cite this example let me add one more. Two men died when they were employed by a large defense company to clean out "empty" storage tanks. Dangerous stuff those empty tanks. I wouldn't do it.

I'll bet OSHA busted their company for a hefty fine. Confined space permits and clearing of tanks is common knowledge to everyone who does that stuff; except I guess the dead guys.

More cautionary tales from the US chemical safety Board this week

http://www.cape-coral-daily-breeze.com/page/content.detail/id/510725.html?nav=5037

Yes very dangerous

I would stay away from the acetylene tanks as they contain things other than just a pick up tube! They are also thinner and won't make a very good ringing sound. Then go to any welding supply store and try to get them to turn you on to the tanks that no longer past certification and are going to be destroyed anyway. There are several other gases that come in tanks that would be suitable like CO2, N2, etc.....

If I really had to do this there are only two viable opitions.

1. Purge the tank as suggested then pull a vacuum, take it to a company that does water jetting. They will cut it quickly and safely.

2. The other way is probably the way I would do it here in the US west. First the same process as 1. then I would pile up about three wooden pallets, start them on fire with a couple of chunks of old VW engine block. The magnesium is a great fire starter. I would have already laid the tank across the pallets. Next you run like hell out to 100 yards or 75 plus meters. Position yourself below ground level if possible. Looking through my huge long range scope I would wait until the until the paint was gone and the metal was just starting to flex and walk around then I would then shoot the tank just below the valve at the top. Any future concern of fire or unexpected rapid expansion of gas from cutting devices will be gone in a fem-to second.

I have lived through #2. however I did not use the tank for art but it is a great Idea.

miketheboilerguy@aol.com

Oh yes ! I saw the video. I can't believe the stupidity of the people that gathered to watch, is only surpassed by the criminal ignorance and lack common sense of the "expert" that set the explosives, just imagine 140 Lb. chunks of rotten meat flying and falling around you.

He shouldn't have said on TV he was an engineer, that gives a bad name to all.

THE ONLY WAY TO CUT OFF THE BOTTOM IS TO COLD CUT THE TANK WITH A COLD CUTTER, TREAT THE TANK THE SAME AS A LIVE PIPELINE THAT HAS BEEN BLOWN DOWN.

One summer many years ago I worked at a helium extraction plant. Occasionally we had to check tanks that had expired test dates, We did this by removing the valve and filling the tank with water. The valve was then replaced with a pipe that went through a hole in a round plate. The plate was then fastened to the top of a larger cylinder containing water, and the cylinder under test would be suspended in the water.

Water would be pumped under high pressure into the cylinder and the amount of water displaced in the large temperature by the expansion of cylinder under test was measured. When the pressure was released if the tank under test did not contract adequately as indicated by the water that returned to the outer cylinder, the tank failed. It would be removed, the special disk removed, the water drained, and hole would be cut in the cylinder with an oxy-acetylene torch.

Good tanks were inverted, drained, and air dried by inserting a hose in the hole where the valve went. The valve would be replaced, then a small amount of helium would be put in the tank to flush any air and a vacuum would be drawn on the tank before it would be returned to service.

As for acetylene tanks. It is my understanding that acetylene becomes unstable under pressure so the acetylene tanks would be filled with some kind of fibre and a fluid like acetone added. The acetylene would dissolve in the acetone. It is also my understanding that the pressure sensitivity of acetylene is the reason that underwater divers used a mixture of oxygen and hydrogen when welding or cutting under water,

Fill with water and cut bottom off with pipe cutter, the cold kind.

Remove the valve, stand the tank up in about 1" of liquid nitrogen. Tap the frozen bottom with a hammer. The frozen part will shatter.

viola! One ugly bell!

I'm just curious, because this isn't my field of expertise...would it be safe to anchor the tank underwater, say in a swimming pool, and cut the bottom off with a hacksaw? If the whole contraption is underwater, not only would heat be quickly dissipated but there would be no free oxygen to permit combustion.

Of course, it would be awkward, but would it be safe?

Why make life difficult just fill the tank with water?? then cut the bottom off with an industrial band saw,

If the oxy tank were filled with water and drained there would only be air inside, but still cutting with oxy can be dangerous in a semi sealed cylinder due to build up of gasses which can explode if the right mix should occur before a reasonably sized hole is made to vent it. Underwater this problem arises when gasses collect in a pocket above the cutting area changing to hydrogen will not relieve this problem.

The best suggestion is leave well enough if you are not familiar with the possible dangers. Of all methods abrasive water cutting would be the best and safest method.

Have read all posts, thus far... and, lest there be any uncertainties generated in anyone's mind regarding submerged cutting: "heat (would) be quickly dissipated"...

[ granted, a hacksaw generates much less, but... read-on...]

Divers have perished while performing underwater cutting operations, when pipelines (which had supposedly been purged by pigging with water), and even toppled platforms proved to hold trapped air and combustibles.

In 2008 we performed an investigation (real-world conditions) to see whether underwater drilling or underwater grinding would be the best means to help verify the presence of, or to help eliminate, such trapped gasses.

The report (https://www.adc-int.org/documents/TemperatureRise_GrindingvsDrilling__UW__.pdf - sorry, link no longer available) is rather large (pdf), but, if you can get to the video screen-capture image on page 7, you'll see that even with surrounding water (30 foot column overhead) MUCH heat is still generated (underneath, anyway)...(downloading requires patience).

Also... in response to acetylene cutting (underwater), this is only performed by outfits that cannot afford to bring themselves out of early 20th century...

Systems such as http://www.akbartraders.com/broco-underwater.html have been the name-of-the-game for decades, now.

That is, when all other safety issues have been properly addressed.

Best to all ~

Most people think that gas cylinders are a bit like a Thermos flask inasmuch as the internal volume is nearly as large as the external volume. When I was dealing with Argon cylinders we calculated the internal volume of the gas storage and found that in a 5' cylinder the size of the "hole" was about 12" to 18" deep by about 4" in diameter. Try working out the internal dimensions before doing any cutting to see if the cylinder will even make a decent bell.

Tony

Rent or borrow a large pipe cutter.It produces no heat when cutting.Fill the tank with water with the end fittings removed.This is the safest way I know of, but still do not recommend doing it.

GA MasterBlaster, you clearly know whereof you speak!

My suggestion would be to fill the acetylene bottle with water and cut it with a band saw, any acetylene left in the bottle or cast steel will be blanketed by H20

Back in my early welding days I had a small repair shop in south Alabama that I tried to make a living with. I did ok but never really made more than living expenses and was always having work like hell to make that. I had a deal where I would fix any tractor gas tank for 35.00 The old Ford 8N and 9N tanks had spot welds on the mounting brackets to the tank that would nearly always leak from constant vibration. Fixing one of these tanks was no easy chore all of the spot welds would have to be drilled out and re-weld or brazed up and it could take a few hours to do. I was hungry so what the hell besides, 35 bucks is better than 0 bucks. My system was to purge the tanks with an inert gas and then weld them up. I many times had no argon or Co2 and in this case I would use exhaust from my old fork lift to purge the tanks. One time time in a hurry I decided to just fill one with water and weld it up. BIG MISTAKE! I managed to turn the tank so I sealed a small pocket of air under where I was welding and BAM blew the tank to smithereens and drenched me and the shop with the nasty water. The bad thing was that the old farmer made me buy him a new tank for blowing up his and back then they were over 5 times the amount I charged for a repair. lesson learned is that although I had gotten away with doing this a few times it was still an accident waiting to happen and I would not recommend cutting on anything like this with water in it only. If you just won't have it any other way and got to try it for gods sake watch how you turn it so you don't trap a small pocket of air. If I had been a few inches over a piece of the tank would have hit upside my head and may have even killed me that day.

Cutting with a torch is a very very bad idea. When you go to blow the molten steel out, you introduce pure oxygen into the cylinder. This mixed with the smallest amount of fuel, whatever it be, will ignite and you have just created a very large pipe bomb.

Instead, fill the bottle with water, and attach a hose for continuous flow. Use a metal cutting band saw to remove the bottom. After the saw penetrates the interior of the tank, flow water continuous into the tank and out the saw cut. This will ensure that temperatures will remain below ignition point.

Why mess around with these bottles . . . yes they are free . . . but free any thing can turn out to be very expensive.

Take them to the junk yard . . . get the money from scrapping them!

Buy scrap pipe and build your bells from open ended things you can look through!!

Probably get the scrap pipe at the same yard.

Acetylene tanks are about 1/3 full of acetone in which large volumes of acetylene will dissolve, requiring lower pressure to store the gas. Here is one safe way to purge the tank before cutting it: 1. Depressurize the tank and remove the valve. 2. Dispose of the acetone as required by local ordinances. 3. Add 1 Liter of water and heat just to boiling for about 5 minutes. (Watch the wisp of steam that comes out.) DO NOT BOIL TO DRYNESS. 4. Dump the water and repeat. Steam in the tank during the boiling replaces the air that could cause ignition. Take the second boil off to dryness, and let the tank cool. I have used this to make BBQ pits from used acetylene welding tanks with no unpleasant surprises.

the only sensible answer so far has been from nuke sub with the suggestion to use high pressure pipe instead of screwing around with an inherently dangerous operation. anyone who has ever messed around with tubular chimes knows the right clean tone requires some careful cutting to length for best effect. But this is typical of engineers. They tend to get fixated on the process instead of the end result.

I found myself doing the same until I began visualizing the actual processes involved to stay safe. Being a lazy guy I began thinking there must be an easier way. who cuts round stuff with thick metal walls -pipe guys! right. and around here we see several example of pipe line welders doing stuff at home using off-cuts. Hmmm? surplus off-cuts and calculate the resonant length beforehand so you know approximately where to cut in the first place. Just go to any store selling chimes and analyze the products being offered the reverse engineer the product to see how its done.

http://www.cylinderrecyclers.com/brochure/Acetylene%20Recycling%20WP%201.pdf

Some info on recycling of tanks and problems.

By far the absolute best answer yet!!!

As said earlier, after reading what you guys have posted I told my friend to call a number in the posted links to find out how to safely get rid of the acetylene tanks.

As far as nitrogen, or oxygen the recommendations are to purge with water.

My friend has not cut these tanks in the past, and was at least wise enough to ask around before doing so.

I myself do not know everything, and when I do, I'll likely not be breathing, and that is suspect too.

I do really appreciate friends that are not bullheaded. It was very nice, extremely nice that I could even ask here on this Forum, "Is this safe?"

The answer is really a resounding "No."

If there is any reward here and now I can give to you on this forum for contributing other than a GA number for coup, it is for you to know that information such as given may well have prevented deadly experiments.

Thanks from the bottom of my heart.

P.S. I'm big into cliches` lately.

I remember reading in an old British book on sheet metal working something related to acetylene. The sheet metal mechanic had fabricated some "gas generators" out of copper. These were for a restoration job on an auto that had gas lamps. The devices produced gas, which I seem to remember was acetylene, by reacting carbide with water. When the generators were brought back for refurbishing, he reported that whenever he struck the copper with a hammer there was a small explosion. His conclusion was that the gas had entered into the metal and that you can't work on used copper generators. I wondering if the actual reason was some kind of carbide/cu/ oxide ? deposit or residue. Obviously I'm not knowledgeable about chemistry, but does anyone have any thoughts on this?

That is interesting information. I have never heard of something like that but this means nothing for there are many things I never heard of. I have used silver solder and an oxy acetylene torch to install and repair copper air conditioning pipe and other copper items many times and never had this kind of problem. I would also like to know if copper can absorb acetylene gas as well as how/why it can do this. Copper is pretty soft in the annealed state but not sure if this would be a factor.I bet there is a chemical/metallurgist type person here that knows this and could teach us something. If anybody knows please share the information.

I seriously doubt that modern wrought copper can absorb either carbide or acetylene. My suspicion is that either the surface was contaminated with carbide, or the old copper was either a porous casting or had been exposed to sulfur or an acid that had metallurgically damaged the copper making it porous. I suspect a good washing in soapy water would have gone a long way towards solving that problem. Copper is no longer used for natural gas fittings because the mercaptan will attack the copper over time. Is it possible that this copper tubing was used for natural gas at some point and got reused?

Hmm, didn't know that. learn something new every day...

Good job on finding the appropriate wiki entry nukesub, i'm putting you in for promotion to COB.

For some reason this post reminds me of another potential deadly action that I have seen done more than once. Although this has nothing to do with this post it is as dangerous if not more dangerous than cutting on flammable gas tanks IMO. I am talking about people inflating tires with oxygen instead of air. Every time I saw or heard of someone doing this the story was close to the same. They had a flat and didn't have a source of compressed air but had an oxygen bottle and thought that it would be ok to air up the tire just long to get to a station. I think one reminds me of the other because both of these actions are both very unsafe and should just not be fooled with in any circumstance IMO.

I had a friend in Texas that used to keep an adapter on his welding truck just in case he had a flat while welding on a pipeline or some other place way out from town. My friend was doing this one day when the tire exploded violently. Six weeks later he woke up in the hospital and discovered that he no longer could hear and also had badly damaged his eyes, lungs and other internal organs as well as broke one arm in two places. A piece of his truck had also flew over 100 feet and nearly cut his father in law's leg off when it tore through it. The welding truck looked like it had been totaled in a bad wreck and the bed and welding machine was completely blown off of truck frame. . My friend told me that he had done this many times in the past with no problems

I guess most people that fool with welding and cutting has seen the "use no oil" warning on all oxygen gages and I have always heard that it was very dangerous to mix oil and oxygen. I wonder if this is why the tire blew up being the tires are made from petroleum and/or many times people will use a small amount of oil around a tubeless tire bead to help it seal initially The thing that is surprising is that I find that many people do not know this and said if they had a flat and this was the only way to get the tire inflated they probably would have tried it too. I know that oil is a source of fuel for combustion and oxygen accelerates combustion and this is a good enough of a reason why not to mix the two. It is not uncommon to mix oxygen with other flammable materials such as acetylene. Although these mixed gases can be dangerous when fooled with improperly I have never heard of these mixtures just exploding without a source of heat or a spark to start things off. Can anyone explain why tires can blow up when inflated with oxygen when there is no source of heat or a spark to start the explosion?

I should guess from my experiences that as one suggested in the thread, that a spark was involved in the explosions of tires. I would also suspect that this explosion did come about due to other factors beside just the tire, and inflation.

When filling oxygen tanks for pressurized aircraft one is never to allow oil onto any of the fittings. I believe it generates Carbon Monoxide, and there have been cases when all on the plane died, and the aircraft on autopilot flew around till it ran out of fuel.

This was not a violent explosion event, and after 20 or so years, I have to admit I am a bit fuzzy about things I did, and seem to think it has something to do with Learjets.

Never got so far as to work on Jet Airliners, but the rules are likely important for the Emergency Oxygen Masks System, since I thought for cabin pressure and a breathable atmosphere, compressors were the main system.

I think that the main difference is that Oxygen is a Reactive Gas, whereas Nitrogen is an Inert Gas.

Factors of Dust, Oil, Friction, Temperature in the presence of a spark are deadly even in standard atmospheric environments as many Electricians know.

A little oxygen can go a long way, aye.

P.S. I'm pretty settled that messing around on your own with acetylene tanks is not recommended at all. Cutting them in half with a bandsaw isn't worth the time. Wonder if for Air Products some sort of guillotine rig could be created to make the job more efficient, or maybe lasers. What about a double pinch press thing? Maybe I'll call Reid and ask him who he sold the company too and see if there is a job making a better system? Now I want to start a new thread so I get to refresh myself on Aircraft Pressurization Systems.

Good answer, I knew that I had heard the reason this could happen before but I had forgotten why, thanks for clearing that up. I guess my buddy had static electricity make the spark that day. He would probably rather blame it some sort of bad voodoo or one in a million chance thing and not his stupidity that caused him to get hurt so bad.

You should also never use oxygen to blow dirt off your clothes and then go and light up a cigarette or go back to welding. The oxygen will permeate your clothes and turn you into a human bonfire. A lot of people on medical oxygen have incinerated themselves because they just couldn't quit smoking and lit up while either still breathing the oxygen, or had just turned it off.

Andy Germany is right. Oxygen is one of the most dangerous materials known to man.

I know of a few people who have been killed or burned from smoking a cigarette while on or right after being on oxygen. What is bad is that most had to be put on oxygen because of damage done to their lungs from smoking.

There was no spark at all the tire was still sealed at the bead and partially inflated and my buddy was just airing the tire up normally except he was using oxygen. I was thinking that there is a legitimate chemical reaction that can cause oil and oxygen to explode and was wondering if there is does anyone knew what is it called.

All safety issues aside I do think the tank can be cut without killing yourself. or someone else in the process. If had to cut one I would use argon or another inert gas and purge the tank first. If you correctly purge with an inert gas any tank of any flammable gas and oxygen and fill it with an inert gas it will not explode from a spark or open flame because:

1) the acetylene gas would be displaced by the heavier argon eliminating the source of fuel for a fire.

2) The argon would also displace any air/oxygen in the tank eliminating the accelerator for the explosion and fire will not even burn without oxygen being present.

The way I would do this is to screw a nipple and a tee into the valve threads and then attach a couple of small ball valves and rig the tee so I could put a flow meter and argon on one branch of the tee and use the other branch to vent the gas out. After I was satisfied the argon had displaced the flammable gas ( IMO I would purge for at least 10 minutes before testing the atmosphere in the tank ) then I would close the vent valve down to just a crack, set the flow meter to about 10-15 CFM and then using I would test to make sure it was not going to explode before starting to cu. I won't tell you how I would test the tank because it is very easy to do wrong and then regret it. My test method is based on argon not being able to sustain a fire and the fact that I had continuous pressure on the tank. We weld on potential explosive tanks routinely in the paper mill but only after cleaning, getting a good atmospheric test and purging with an inert gas such as nitrogen or argon(nitrogen is allot cheaper to use for a purge) I didn't want you to think that this cannot be safely done but rather that the risk of getting something wrong in the set up is not worth the bell you'd get from it IMO. If you notice acetylene tanks have a smaller radius on the top of the tank and the transition from the side of the tank to the top is nearly square where other tanks are rounded out more like a bell. What you would have is a very ugly bell for your trouble.

In my younger days it was a little exciting to do some things and even though it was sometimes very stupid to take the chance. I think I took chances back then because I didn't have the sense to understand the dangers. As I got older more and more I realized that the outcome of doing some things is not worth the chance taken and I am afraid that cutting on acetylene tanks is one of these.

How about taking them to a place that does water jet cutting. We've had more than 12" of nickel alloy cut this way and it produces a nice clean cut.

That is a very good idea, I think you could do it safely with a water jet but I don't think an ugly bell would be worth it unless you or a friend already owned the water jet. The only water jets for hire I know about are getting $100.00 an hour with a one hour min charge to cut for the general public. I have not seen a water jet that could cut on a three dimensional object like cutting the tank would require but I am sure they probably exist. The water jets I have seen would only cut on flat plates. A buddy of mine had the sweetest little water jet setup he used to cut out parts with. He recently sold it and spent near a million dollars for an even sweeter IMO laser and a super nice material handling system to feed this metal eating beast with plate. Although the water jet made a very nice cut he said the dampness created from running the water jet caused other equipment in his shop to rust.I do not know if this is right and the water jet did cause this rusting problem but he believed it did enough to spend big bucks for the laser.

you can use a radial gearmotor frame like those used for pipeline orbital welds to hold the waterjet head. Back when I worked for a oil well fire control company we had designed a dual head waterjet cutter for the wellheads that Saddam had blown up in Kuwait.

The problem with acetylene tanks is not the acetylene, but with the acetone that is is dissolved in and the friable matrix that is soaked with the acetone. that is why you should not lay your acetylene bottle on it's side when you are using it. You'll be getting liquid acetone instead of acetylene at your torch head if you do.

Oxygen + Oil = Bad Explosion.

Tires are made from oil!

Need any further details?

PS Oxygen is probably the single most dangerous gas to "play" with.......after cyanide gas etc....

If you look into O2 safety, you will see a lot of rules listed. The first one is that, as the above poster stated, O2 is a reactive gas. This gets even worse when it is under pressure. In fact, it gets sensitive to sudden changes in flow because the pressure wave has enough energy change to initiate combustion. The reason that high pressure O2 lines have to be absolutely clean, is that oxidation generates heat, and even the smallest hot spot will cause a chain reaction.

My best guess is that one of two things happened with the tire. One is that the metal fitting that he used made a spark on the threads of the valve stem as it rubbed across them. The other is that the tank was brand new and used unregulated, and after the tire was full the fitting was pulled off quickly, resulting in a compression wave when the valve stem closed.

I quickly glanced through all the lengthy comments above and did not see an answer from anyone who had actually done what you are trying to do. I actually did this back in College. I worked at Air Products and Chemicals while going to college back in the 1980s. I was asked to cut hundreds of old decommissioned gas tanks in half, acetylene , propane, oxygen, etc.. We cut the tanks in half due to liability. They did not want someone cleaning the old tanks up repainting them and trying to reuse them. As someone mentioned earlier the Acetylene tanks are filled with an asbestos like material and when cutting into them you NEED to wear a safety mask. Over the period of 6-8 months I literally cut hundreds of these bottles in half using a horizontal band saw with a very tough carbide steel blade. The band saw was motorized and you could adjust the rate of cut. The faster the rate of cut the more heat is built up and the quicker your blades get worn out. The saw had a reservoir where we put a liquid solution to cool the blade down (don't remember what the solution was called or what it contained). Be aware that this is a REALLY SLOOOOOW cutting process. The steel is thick and you can't rush the blade. The good news is the cut is nearly perfect with only minor needs to dress up the edge. I gave some of the old tubes to my father who made some BELLS out of them. I suggest that you contact Air Products & Chemicals or any similar gas supply company and ask to speak with someone who is in charge of decommissioning gas tanks. You could also go to most any metal fabrication shop and they will most likely have one of these band saws and you can pay someone by the tank. There is a company called Detroit Nipple, based in Detroit, they specialize in supplying metal pipes and said they could cut each tank in half for $25 per tank. Here is the link to their site http://www.detroitnippleworks.com/.

A very important item to keep in mind is that you will take on the liability of the material inside the tank if you ask someone to cut into the tank. As soon as someone cuts into the tank and sees white fluffy stuff floating around the room you are going to get a call from either the union or a lawyer. If you are going to have someone else cut the tank for you, then you will need to know what the material is inside the tank. Is it asbestos or something harmless? You will need to have it tested and a licensed professional certify that it is harmless. Or you can go out and rent the saw on your own buy a good face mask and take on the inhalation risk yourself. The latter is a much cheaper and swifter way to proceed. If you take precautions it can't be that bad. I'm 26 years older than when I cut those tanks I am healthy and a competitive swimmer. Good luck!!

Static electricity is perhaps the greatest fire hazard known to man. More fires are caused in industrial environments by static discharge than perhaps any other source. Our clothing, even our hair on our head, with a slight breeze, especially when working in low humidity areas, generate static charge of many thousands of volts. Everyone of us have scooted across the car seat, touch the door handle or other metal and bingo . . . the spark. Mix high concentrations of oxygen with dust in the air and make the spark for ignition. This is the reason the tools for tightening/loosening the gauges are made from "non-sparking" materials. If your friend was had been grinding, using an aluminum based grinding wheel . . . dust on his clothing could be responsible for the ignition and now where the chain reaction stops is limited only by the quantity of oxygen and proximity of the combustible materials.

almost anything will burn in a pure oxygen environment . . . NASA found this out during the workup to the Apollo Space program . . . when the space capsule was filled with 100% oxygen.

http://en.wikipedia.org/wiki/Apollo_1

Why not use a section of steel pipe around the same diameter as the bottle and weld a plate to one end.

Normal steel pipe does not make a decent ring when clanged.

After 68 posts the message should be, don't do it, don't consider it. Take an expired or no longer needed acetylene tank to a welding gas supplier for disposal even if it costs a buck or two. That will be the safest and cheapest option.

John 11:35.

Job 38:11.

The gas doesn't infuse to the metal, but the tank is filled with gypsum to stabilize the gas. I have safely cut the tanks open by first removing the valve and then flushing with water and refilling with water before cutting with a diamond blade reciprocating saw.