evfreek Posted December 18, 2011 Share Posted December 18, 2011 Hi. Someone gave me a CO2 fire extinguisher. It is the small 5 pound one, with the valve handle on top and a plastic horn on a swivel hose. I want to convert this into a CO2 tank for my mig welder and for carbonating water. I have a spare regulator for CO2, with a CGA-320 fitting on it. The fitting on the fire extinguisher valve is an odd one. It has about a 1/2" opening and appears to be a 1/4" NPS thread, not the more common NPT thread that is tapered. What would be ideal is an adapter that has one male NPS end and one male CGA end. Unfortunately, these are almost impossible to find. I called a couple of fire extinguisher places, and most don't deal with CO2 extinguishers. Others just send them out to be refilled. Finally I received a referral to one who said they know what I am asking. Although they said that they have the adapter, they said that they it would be better to vent the cylinder to the atmosphere, refit it with a handwheel valve, and hydrotest it. In total, that would run about $90. Looking around Ebay, I noticed cheap new CO2 tanks about the same size selling for between $50 and 100. Some of them were substantially less, but would require high shipping charges. Locally, they are probably more, but there wouldn't be a shipping charge. It looks like it would cost less just to get the cheap made in China new tank than try to retrofit the old one. But, then I would waste the tank. A lot of people lament that we live in a throwaway society and that we depend too much on Chinese imports. But, it seems like, at least in the short run, it is much more convenient and less costly. The way the fire extinguisher shop was talking, it was unclear whether they really had the adapter. Now, I am beginning to doubt it, and since it is pretty far away, it will cause a lot more carbon dioxide impact to drive there than it will to vent the tank to the atmosphere. Searches on the internet do not show adapters of this type, although there are several hits for paintball tank adapters. One resource did say that it is safe to adapt an NPT thread to NPS if lots of sealant is used. 800 psi of CO2 is enough to cause a lot of damage if it comes loose, but a simple thread shear calculation tells that a silver soldered homemade adapter of this diameter would be safe at these pressures as long as it was made of brass and not cast iron. If it is desirable to minimize the waste stream, are there any other good ideas for salvaging this tank? Link to comment Share on other sites More sharing options...
Jacques Posted December 18, 2011 Share Posted December 18, 2011 If I were you I would not fiddle around with pressurised tanks. The last time our compressors were tested the technician told me all sort of horror stories about what he have seen when tanks burst. And I still haven't found the gauge I home fitted onto my CO2 tank. It was a scary day that. Link to comment Share on other sites More sharing options...
eric sprado Posted December 18, 2011 Share Posted December 18, 2011 Don't DO IT. Don't DO IT.!!!!!!!!!!! I've seen the blown up pickup trucks etc. from stupid handling of pressurized materials. DO NOT DO IT. Got it???? Use the tank as a Shell for a small KO Wool lined forge. Lots of plans for those on all the sites. Link to comment Share on other sites More sharing options...
Larry H Posted December 18, 2011 Share Posted December 18, 2011 If you change its configuration no one will fill it,...co 2 gives a crummy weld compared to 75/25.......and i think the stuff in drinks is more pure for ingesting.... make a bell or something Link to comment Share on other sites More sharing options...
ptree Posted December 18, 2011 Share Posted December 18, 2011 I say DON"T do the conversion. First, no one will fill it for you, period. Second, a CO2 tank in the soda fountain size is not expensive, can be filled/exchanged, and is designed and built for the service. I use a "soda Fountain" size bottle with my 110Volt mig and it lasts a long time, costs about $13 to have refilled here in S, Indiana. The CO2 extinguishers make nice bells. Link to comment Share on other sites More sharing options...
pkrankow Posted December 18, 2011 Share Posted December 18, 2011 CO2 fire extinguishers are rather nice because there is no mess to clean up after they are used. Dry ice evaporates and CO2 is a gas. I have cleaned up after BC and ABC dry chemicals. BC is a horrible gritty powder that gets into everything, and ABC fuses to everything hot it touches. Phil Link to comment Share on other sites More sharing options...
evfreek Posted December 18, 2011 Author Share Posted December 18, 2011 It looks like the consensus is "do not modify". As for the comment that "no one will fill it for you", at least one place will fill it for me. The shop that offered to do the conversion. Apparently, they are the only place around here that refills fire extinguishers. If they convert it, they certainly will service it. They get to do hydro's every 5 years, anyway. The CO2 tanks require more frequent testing due to corrosion possibility. As for bells, I have an OSHA buddy who de-certifies gas cylinders. There is an endless supply of these things, but they are miserable to work on. They are made of a tough steel, they are scary to cut with a torch, and they radiate a lot of heat when they are at forging temperature. It is a lot of work being asked to assist on forging a bust and hips on one of the 5 foot ones. This was really more of a complaint or rant on the throwaway society that hurts a traditional blacksmith's heart. Most of my buddies have the small grow or keg sized tanks that they picked up cheap from some Chinese importer. Probably safer too. Gotta get with the times :( Link to comment Share on other sites More sharing options...
clinton Posted December 18, 2011 Share Posted December 18, 2011 Find the right cylinder for the application. There are new 20 lb tanks available for $150 - $200 I would get the steel tank for 200, a damaged tank will not be refilled.http://www.ramweldingsupply.com/products-list.mcic?c=68 I was taught to NEVER mess with pressure tanks. There was a guy that blew himself up when I was in welding school. He went to the local supply house and asked for fittings so he could trans-fill an oxygen tank. They told him it was not safe to do so and would not sell him any fittings. He went out with a bang- nothing left. If you did manage to get a valve fit on that fire extinguisher no supply house would fill it. The tanks for welding are rated at 1800 psi Link to comment Share on other sites More sharing options...
Steve Sells Posted December 18, 2011 Share Posted December 18, 2011 in the construction trades, pressurized vessel work requires a special license for a good reason. Link to comment Share on other sites More sharing options...
peacock Posted December 18, 2011 Share Posted December 18, 2011 It won't be wasted use it for a fire extinguister. allways a good thing in a blacksmith shop Link to comment Share on other sites More sharing options...
SmoothBore Posted December 18, 2011 Share Posted December 18, 2011 I recently visited a Smith in Southern Pennsylvania, who had 4 Fire Extinguisher "bells" of various lengths, hanging by his door. they were hanging close enough together that you just brushed your fingers over them, and they "tinkled" against each other. It was a very nice example of creative recycling. . Link to comment Share on other sites More sharing options...
Glenn Posted December 18, 2011 Share Posted December 18, 2011 Use the fire extinguisher as a fire extinguisher. BUY or rent an Ar/CO2 cylinder for your mig. DO NOT attempt to mess with high pressure cylinders, and for good reasons. Got to where they are refilled and ask about the horror stories. Many times they begin with "Hey Y'all watch this" and end poorly. IForgeIron is all about safety. Personal safety is YOUR personal responsibility to keep YOU safe. Link to comment Share on other sites More sharing options...
clinton Posted December 18, 2011 Share Posted December 18, 2011 You can buy used tanks on craigslist all day long. 20 lb tanks selling for $20 - $200 right now. Also if you have another tank, oxygen, argon, helium you can trade it for another tank with the gas you need. I had an old oxygen tank and traded it for a co2 at my supplier Link to comment Share on other sites More sharing options...
evfreek Posted December 18, 2011 Author Share Posted December 18, 2011 Sounds like it is safer to leave it as a fire extinguisher. I'll try craigslist. I just had a fire extinguisher training party. Picked out all the fire extinguishers older than 10 years, set a bunch of gasoline fires, and let the boys have at 'em with the extinguishers. It was a great time to be had by all, with many of the classic mistakes including spraying the flames and not the base of the fire, and walking away before the fire was out. We just gave them a little shake and they all performed flawlessly. Some of the people were surprised how little of a fire you could put out with the small 1Abc ones. I pointed out that big fires should be left to the firefighters, and these little extinguishers are only good for trash cans, overheated frying pans, and smoldering electrical appliances. Next time the rotation goes around, we'll just add the CO2 extinguisher to the line-up. When I took them in to be recycled, I was shocked at the $5 recycling fee. These little ones are more expensive to refill than to let them "disappear" and replace with a made in China one. Seems that the local extinguisher place refills and sells them, and it would be a loss for them if it wasn't for the fee. The trash company won't take them, especially if there is a whole bin full of them. ;) Link to comment Share on other sites More sharing options...
clinton Posted December 19, 2011 Share Posted December 19, 2011 I am glad to see that you came to your senses on this. And the comment that you made in your first post about 800 psi not being too dangerous- (not your exact words) I can punch a hole in 1/2 inch plywood with a tennis ball @ 125 psi. I will gladly demonstrate it if you would like to see Link to comment Share on other sites More sharing options...
jimmy seale Posted December 19, 2011 Share Posted December 19, 2011 also boys, remember this. if you discharge one and don't use all of the dry chemical,it still needs to be recharged and tagged.as it may appear to be sealed and not leaking down the powder gets in the valve and will leak. this is so no one get surprised by a dead extinguisher in your time of need Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 19, 2011 Share Posted December 19, 2011 I picked up an air tank at the scrapyard Saturday, pulled the valve on it that afternoon. (The local small scrap yard sells me tanks *cheap* as they can't resell them as scrap without pulling the valve and that's too much work for them...) The top makes a bell. If the bottom is indented it makes a dishing form for SCA armour makers. If it's rounded it makes a ball stake for SCA armourers. If it's flat it makes a quench tank for knives or a bowl to hold stuff around the forge. The valves I sell back to the scrap yard. Only thing that goes to waste is the cutting swarf and the squeal! I avoid Acetylene tanks even as a gift! I avoid powder extinguishers too as they are much more a mess to deal with. Old CO2 ones can be discharged in the summer to cool off canned drinks and when empty treated as above. I sell a couple of bells a year from them and hang the rest around the outside of the shop for the wind to ring. Link to comment Share on other sites More sharing options...
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