Buying oxyacetylene tanks -- advice needed

I'm a newcomer to gas welding, and am looking for some advice on buying oxyacetylene tanks.
I found a private party selling a used set of tanks. It sounds like a
reasonable deal. But, what should I look for? Should there be any papers that come with the tanks stating they've passed pressure testing? If I remember right, I recall hearing that tanks need to pass inspection periodically. If they don't come with proof of testing, is that a deal breaker?
Also, any visual signs I might want to check for, or any other advice would be greatly appreciated. Thanks!
Regards,
- Jamie
The Moon is Waxing Crescent (9% of Full)
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As far as I know, the last pressure testing date is stamped into the metal. Look around the top of the tank.
Jamie wrote:

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Take the tanks to the local gas supplier and get them to tell you what will happen the first time you bring them in for a refill.

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Please see my long long version of this amazingly accurate amazingly short answer. Which is spot on correct.
Steve
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I don't trust buying used tanks from individuals, I buy my tanks from one welding supplier. The cost for my tanks was around 475.00, when I need a refill I take them back and they exchange them for full tanks for around 65.00 for the oxy and 90 for the acetylene.
I've wondered if I pay too much myself, let us know how it goes. Sam
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Jamie wrote:

You can certainly save some money buying welding cylinders used, but it is also risky. Welding cylinders come in two flavors: owner and rental. Lots of cylinders out there on the used market are actually rental cylinders, owned by a welding gas company.
In fact, when you buy a tank, you buy rights to a tank. When it's empty, you take it to a welding supply and swap it for a full one and just pay for the gas. It isn't any fun at all to have the guy wheel your cylinders inside and then come walking back out to tell you "Those are rental cylinders - we can't swap them out for you. Thanks for bringing them back." You have no recourse and you feel like you were punched in the stomach. (Don't ask how I learned this!)
What I suggest is to talk to a guy at a welding supply, and have his store's phone number in your cellphone memory when you go look at the tanks. If there is any raised lettering around the neck ring, call the welding supply and ask if they're rental cylinders. Of course, if the seller has the paperwork that proves they're owner cylinders, that's another story.
When you do get your cylinders, however you get them, the first time you swap them out for full ones I strongly suggest you save the receipt as it ends all discussion about owner/rental issues.
Finally, around here, if you get a cash account at the welding supply store, you can often get a pretty significant discount and it becomes not that much cheaper to buy cylinders from the welding supply, especially now that prices on craigslist have shot up due to the zero cost of advertising.
GWE
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Tanks 101: 1. It depends upon the size: 60 cu ft or less are "owned" bottles. Greater than 80 are leased. 80 can be either. Rarely, large bottles are owned e.g., military surplus. Large bottles will have a collar with the owners name on it.
2. Gas suppliers usually just exchange bottles: you leave your empty and take a full one.
3. My supplier doesn't care about certification. YMMV.
4. Small bottles are just exchanged no questions asked (they are always owned). Large bottles are assumed to be leased and you take them back to the lessee. Anywhere else will refuse them and may confiscate them if you don't have the lease or bill of sale for those rare owned large ones.
HTH, Bob
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Greetings Jamie, Before I bought some used cylinders I wrote down the info stamped on the cylinders and called my gas supplier (Central Welding) for advice. They told me the following: Here in Washington State they basically use two types of cylinders. They are called "Owner cylinders" and "Leased cylinders". The cylinders are in different sizes so that there is no need to look at what is stamped on the cylinder. For example, an Owner cylinder may come in the 80 cubic foot size and the comparable Leased cylinder will come in the 100 cubic foot size. You want the Owner cylinders. When I get my cylinders filled I trade them in for full ones rather than wait for them to be filled. Not only is it faster, it is cheaper also. When you keep your cylinder always eventually it will need to be hydrotested. You will have to pay for this. When you trade in your empty cylinder for a full one the gas supplier takes care of the hydrotesting. So even when I buy a new cylinder, all pretty with new paint and all, when it is empty I trade it in for a full ugly cylinder. ERS
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And I have to ask. Is it OK to transport the Acetylene tank laying down ?
Bill K7NOM
Jamie wrote:

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Bill Janssen wrote:

Its not prewferable, but you can.\ You must let it sit upright for awhile (a day?) before using it, though.
Dave
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The other replies are all of the map because the trade practices in each regional area are all over the map and each dealer practice is all over the map. You will just have to call around to the various dealers and see what they have to say. Prepare to be completely confused. My take on what I've seen;
In general, the smaller tanks are owned, larger are leased/rental. Lots of gray are in the medium sized (122 cubic ft O2, 125 acetelyne)
Rental is a bad way to go, you pay a monthly charge of perhaps $1.50 to $2.00, full payout is set for 5 years.
Leasing can be good or bad. I have a lease where I pay a deposit, I swap the tanks when empty. If I want to get out of the lease, I bring the tank back and they give me my deposit back. I'm happy either way. One of the other dealers in town has a 5 year lease. Pay a deposit, you get the tanks for 5 years. At the end of the 5 years the dealer keeps the deposit. (!!!!)
Purchased tanks are problematic. My neighbor owned a pair of tanks. When he needed a fill he brought them in, they refilled the same tank, he picked it up a couple days later. Two trips and out of service for two days. Plus he had to pick up the recertification charge. (Bad deal.) Other dealers may just accept your tank and swap a refilled one. No recert charges. (Good deal) Then there is the tank that has been stolen or 'converted' from a rental. Bring it in and they say thank you for returning their property. If you purchase tanks from a private party, make sure your gas dealer is good to go with the deal.
Jamie wrote:

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Read through the rest of the responses, everyone's hitting little pieces of the full answer... ;-)
The "always customer owned" cylinders usually are under 3' tall - the B and MC size acetylene, and 50CF and smaller oxygen are safe to say "owned". If they own larger tanks, they'll have paperwork from the local welding supplier with them stating so. And the leased tanks are usually permanently marked on the neck ring as to the company that owns them, call them for more information.
The Hydrotest dates on the tanks are only important if they are way out of test, nowadays they figure that cost into the exchange and refill fees. But to check, around the neck they have the cylinder serial number, and the test dates. Good for 12 years.
Old markings are just month and year 8-93. New markings have the month and year stamped in 1/4" characters, and a custom square punch (2 characters top line, two bottom) with the 4-character code to identify the hydrotesting facility in 1/8" characters instead of the dash. Something like 8(B332)93 This way they can track the cylinders' test history easier - especially if it ruptures...
If the tanks have big dents, big rust, or show other evidence of being really banged around, you don't want them. You may not be able to exchange them, since the suppliers don't want to give you a good set of bottles and possibly have to scrap the ones you turned in.
If you take a questionable set of tanks and clean them up and paint them, they may offer to take yours and test them, and if they pass they'll fill them up and you get that set of bottles back. This will take a week or two.
Read and heed the warnings - The cylinders are safe WHEN HANDLED PROPERLY, and VERY DANGEROUS WHEN NOT. Always transport the bottles secured upright, and NEVER in a closed trunk or passenger compartment. They do blow up on occasion - Acetylene is flammable from (IIRC) 4% to 96% concentration in air, so leaks both big and small are dangerous...
The acetylene cylinders have fusible-plug thermal relief valves, and both have pressure relief valves or rupture discs, and a hot trunk will make them vent off. And acetylene occasionally becomes unstable and goes "Boom!" all by itself when mishandled - Google up the term "acetylene deflagration" for an eyeful.
Strap them in the back of a truck, or if you must use a car leave the trunklid wedged open with a big cardboard box for ventilation. Leave the supplier and go straight home and get the bottles into a shady storage spot.
No cylinders in the backseat of a sedan, windows rolled up, parked in the sun in your driveway or at the local Wally World... You'll come out and find your car opened up like a flower and turned into modern art. The pieces can go hundreds of feet and easily kill someone.
NEVER run the acetylene regulator output over 15 PSI - it is unstable as a gas over 15 PSI without the Acetone and the sponge matrix inside the cylinder as a moderator.
Never draw over 1/7 of the acetylene tank capacity per hour, or you start sucking out the acetone. Causes green spitting flames, not good. This means you are restricted to the smaller tips when using a B cylinder, and the tiny with an MC. If you want to use big cutting or welding tips to do big jobs, you need to buy or lease the big bottles or manifold several small bottles together - With a purpose-built manifold system, see below.
Oh, and no copper tubing for Acetylene piping systems - pure copper and brasses with too much copper in them can form unstable copper acetylide compounds inside, and they can start off the "Boom!". The brasses used in the welding regulators and piping adapters sold for the purpose are safe, but plumbing pieces picked up at the local home center may not be. No messing with unknown adapters.
Between this and everyone else who has already spoken up, That's the basics.
--<< Bruce >>--
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
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Hi Jamie
If *I* was buying a set of oxt/acet tanks I'd go with the seller, and the tanks, to a welding gas refilling shop convenient to your location and let them tell you about the "true ownership" of the tanks. I have bought so many used tanks that I have lost count. I have certainly bought more than 30 welding tanks in my lifetime.
By my standards, the cost to hydrostat the tanks and get them certified has to be ignored. The certification is for your safety. The cost of certification is normally fair.
Large capacity tanks are heavier and somewhat more inconvenient to haul around and to store than smaller tanks. The cost to refill the tanks is greater (per gas volume) for smaller tanks than for big ones.
Jerry
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Here's the straight skinny.
Yes.
No.
NO!
Maybe.
Bottles may be bought and sold unless they are the property of others. You can recognize this by the neck casting that will have the name of a company, such as AirGas, if they own it.
What happens is this:
You "buy" the bottles. You take them to a refiller. At that first "refilling", which will merely be an exchange, they will look at the bottles for about .37 seconds and either exchange them for you, or say that these belong to another company, and they can't exchange them, or that these belong to them, and confiscate them. If they belong to another company, you can take them there, and if they are legitimately bought "owner" bottles, they will merely exchange them.
The bottom line is .............. you won't know until you try to get them "filled" / exchanged.
If they do it the first time, you're home free, with an account, and now, bottles you got from that supplier. It is always advisable to stick with one supplier. Others may trade, but you run into less chances of hassles if the desk guy is having a bad hair day.
Nothing a seller says or does makes much difference unless it is giving you a bill of sale for bottles HE legitimately bought. He can say and do anything, but you will find out when you take them for refilling.
I would suggest that you invite him to take a ride to the refilling depot, and you BOTH have a talk with the guys there, so if there is anything awry, you will catch it BEFORE you give him the money.
Steve, who's had a lot of experience with owner/rental/lease bottles.
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