I have a CO2 fire extinguisher which i bought at a garage sale a few years ago very cheaply. It is out of testing dates and will need to be retested, I have just had it sitting in my shed and i am about to take it in to get it re-tested so i can use it for MIG welding.
Is there likely to be any legal issues with it, could it be an ex- rental or something? If so what markings do i need to look for to be able to tell this as i don't know any of its history?
Any help or information would be much appreciated, Joseph
Over a few years, I've acquired 3 or 4 the same way you did, and none of them had any signs or markings or stamped message to make me believe there would be any problem of ownership. I've had each tested and recharged at a reputable dealer here. Cost of doing that is well below the cost of a new extinguisher.
Brian Laws>I have a CO2 fire extinguisher which i bought at a garage sale a few
Not a good idea as fire bottles are not all rated for the same pressure levels as are welding bottles. Working pressure for CO2 extinguishers are 2/3's or lower than those normally used for bulk CO2. The highest rated portable fire bottle that I could find was only rated for 2000psi working pressure.
The problem Wes, is how are you going to flag the cylinder to the gas monkeys that charge the bottle that it won't take the normal fill pressure? All they look at is the color and the valve before charging it. Do you really want to put a bottle that is only capable of 2000psi onto a charging line that fills bottles to
3000 or 3500 psi? I don't know about you, but I darned sure don't want to be within a mile of that place when it happens. I've been around a bottle facility that went up in flames before. The fire department found O2 and CO2 bottles as far as 7 miles down range. We just had a small facility go up in flames here in the DFW area just a couple of weeks ago. DFD found ruptured bottles as far as a mile away from that one and it was tiny compared to the one that I saw as a kid in Houston. I work around high pressure gas systems every day and minor mistakes can kill you and anyone around you in an instant. We had someone put down the incorrect test pressure when an accumulator was changed out. The resulting explosion didn't hurt anyone because it was contained, but it did cost well into 6 figures to repair the damage done. This is one place where shortcuts and trying to cheap- charley it, will bit you.
Umm. Why would you fill any CO2 bottle to that pressure? it won't get any more gas in and you'd have to partially empty it to make it safe for storage after filling.
I don't think you understand the physics of CO2. It turns to a liquid at moderate pressures (i.e. well under 1000 PSI, depending on the temperature). You can try to push as much C02 into the bottle as you want, but you can't get the pressure higher than that without getting it really hot. It just turns to liquid and fills the tank up. It's not like nitrogen and a lot of other gasses that don't liquify until you get to really high pressures. You can fill a cylinder completely with liquid, and it STILL won't be at a dangerous pressure. The only risk would be if someone filled it completely with liquid and then sealed it, because then it's imcompressible and a temperature rise could cause a problem.
Anyone who is filling a CO2 cyclinder commercially will understand this, and there shouldn't be an issue. The downside of using a fire extinguisher tank is that it isn't designed to be banged around like a commercial gas cylinder. They are supposed to hang on the wall & be used in emergencies. As long as you treat them carefully, there shouldn't be a problem if it's been hydrotested in recent memory.
Never heard of anyone having "owned" issues with fire extinguisher bottles.
AFAIK, the whole "owned" tank thing with the gas bottles is all just part of their racket to tie you, the cutomer, to them, the supplier. Works good, too!
You will want a hydro, and a new valve. The times I was looking at this, they referred to the valve as a "commercial" vale. It is that same valve used on the soda fountain bottles, with screw threads and a shutoff valve, similar to a welding gas bottle (there's a surprise!).
If it is full, hack together some fittings to adapt it to use the gas in it. If the outfit that is doing the hydro and refills will credit you the CO2 that they remove, so much the better. Not a huge loss if they don't, just goes against my cheap nature to waste the stuff.
CO2 pressures are low, on the order of 800 psi, without overheating the tank or overfilling it, and your biggest risk is that the seals are shot to heck on the valve itself, and it leaks once opened and under pressure, in which case, you are no further behind. Fire valves may not be pressure tight, downstream of the poppet valve, or around it's stem (the part of the valve pushed in by the handle on the extinguisher), as their intended use is to dump the product on demand, if that makes sense to you.
CO2 fire extinguishers (FE) are not normally rented, they are sold. If you don't see "PROPERTY OF FOOTROT FLATS SCHOOL DISTRICT" stamped on the neck you are probably clear. The service people aren't going to run the serial number with the police unless you give them cause to be suspicious, they just fill them.
To get the best price and turnaround time, make sure you find the FE service company in your area that actually has the hydrotest cell and the filling gear on site - otherwise they send the work out to the people who do, and mark up the price to make some money on it.
There has to be an identification and instructions band, and it has to be readable. There has to be a readable serial number on the band, so they can log the recert.
The cylinder can't be all dented up or rusty - if the paint isn't perfect sand it down and give it a fresh coat BEFORE it gets bad. You will have to touch it up where they stamp the new hydrotest date.
And it has to be made by an FE company that is still in business or where they can get 'certified repair parts' from a successor company - it's silly, but for liability reasons they can't buy and use 5c bulk O-rings from McMaster, they have to buy the part through the FE maker for a buck each for the liability insurance.
(YOU can find and install an exact equivalent replacement part, as long as you don't tell the FE service guys you did it... But you have to be certain you have the exact size and materials, or it can fail in use. And the whole thing about a FE is that it can sit for years but has to work when you need it to, so don't take any shortcuts.)
If the manufacturer is long gone and the FE parts are no longer serviceable, you can get a new CGA valve and have them hydrotest and convert the bottle for welding or beverage CO2 use.
But if it's still usable as an FE it's more valuable as one - get yours filled as a FE and ask the service shop for a welding gas cylinder. People throw the whole FE in the trash if the valve or horn is bad, or the label/band is unreadable and they can't be used as a FE anymore. All you pay for is the valve, hydrotest and fill.
Doug: I do remember most of the physics of pure CO2, but in this case I'll plead brain fart partially due to way too many days with nearly no sleep over the last couple of weeks. It's also been nearly 15 years since I worked with CO2 by itself. Normally I deal with N2 and O2 and mixtures of various gases at pressures well above 2000 psi as well as LN2 and LOX. What I remembered, and missed was the absolute pressures on the vapor pressure curve given the bottle fill percentage vs. ambient temp. What I was remembering correctly is that the bottle pressure will rise approximately 500 psi for a jump in bottle temp between
80F and 90F, when the bottle is over 60% full and less than about 90% full. I simply displaced the curve about 50% upward.
BTW: There are now some commercial processes that are using CO2 in liquid form at pressures in the 1500-2000psi range.
I think the intension - I hope - is to use it as fire prevention. Normally they are to small for MIG except for tiny pony and portables.
The largest I have seen was mounted on two 4' tall metal wheels. But the largest tank CARDOX was outside a paint house at a GM plant. Fire suppress the entire building in seconds.
Martin
Mart> I have a CO2 fire extinguisher which i bought at a garage sale a few
Lots of good advice from others but I did not notice anyone letting you know that fire extinguisher bottles have a dip tube to draw liquid from the bottom of the bottle when being discharged. For welding you will want to draw gas from the top. This should not be a problem if the valve is replaced, as the dip tube is connected to the valve. Just for your information.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.