Buying used oxygen/acetylene tanks

An old boss of mine was cleaning out his storage and has some oxygen and acetylene tanks. 
 

They all feel empty, i was thinking there was something to check out with buying these used? 
 

Also is there a going rate for the empty ones? 
 

here is a picture of the tanks in question 

No biggie, the worst is they need to be hydro tested before being refilled.   ~$20

Most small welding shops exchange bottles, and send the empties in to the home office to be filled.

Make sure whoever the tanks were originally bought from still exist and are convenient to exchange with.

The two primary players in my neck of the woods are AirGas and Welsco, they do not want to exchange each other's bottles.  Unless you know someone, or are willing to cause a scene I'd go as far as to say that will not exchange each other's bottles. 

I've got an uncle-in-law that got Welsco to take AirGas bottles, but only because he's been a customer of theirs for decades and has spent tons of money with them, they still protested.

I know Welsco covers certification on their bottles no extra charge, I assume most do.

If you don't have a truck or trailer to haul them in, most won't let you haul a bottle in enclosed spaces like the trunk of your car.  Used to be you could sign a waiver and toss a bottle in your trunk, but that hasn't been the case, at least locally, for several years now.

Even if you take a used bottle to its original supplier, and you're not already a customer, expect the 3rd degree on how the bottles came to be in your possession.  Bottle theft is so prevalent that a lot of places won't exchange without proof of purchase, so have the seller write up a bill of sale.

That ring around bottle just below the cap should tell you a supplier name.  Those are small enough to "own" but most places just swap out full tanks for whatever you bring in. They worry about certification updates. The larger tanks, I forget the size by letter designation, are all rented. They charge you a small rental fee each time you get it swapped out based on time not frequency of fills.

I have a couple of aluminum tanks that were used to store CO2 for a laser cutting cell.  I thought they make great compressed air tanks for mobile usage.  I think they're rated to 3000PSI.

As noted, there is a certification date.  If expired, they will likely need to be re-certified before anyone will fill them.  I was under the impression that it was more than $20 to re-certify.

In reply to 1988RedT2 :

Welsco is only in Arkansas and Oklahoma, so it probably doesn't apply to the rest of y'all but they don't charge to recertify bottles you buy from them.

In reply to bigdaddylee82 :

My bro worked at the big name place and when they have a customer want to leave them they do an inventory of the tanks and present a bill for missing tanks.  Then the customer re-signs rather than pay for a large amount of missing tanks.  

Kicking the can down the road. 

In reply to Datsun310Guy :

I could see that if they were leasing.  If you're going through a lot of gas, it can make more sense to lease and just have new bottles delivered and exchanged on-site.  I worked at a mid size boutique trailer manufacturer (bid on and made all kinds of stuff, but trailers were our focus).  I ran a CNC plasma table, that used a giant, early '90s Hypertherm machine torch, that used a bottle of Nitrogen and a bottle of Oxygen for "air."  That plasma table, 3 full time welders, and 3-6 part-time welders (piece work) we went through a lot of gas, and it made more sense to lease bottles.

I don't recall us ever losing track of bottles though.

Personally I own my bottles, I don't go through near enough gas to justify leasing.

Yeah, I bought my tank from the local gas guy, and he said just bring it back for exchange before the certification expires.  As it turns out, I use not a lot of gas, and sure enough, the date had come and gone.  When I took the tank back, they either never looked or didn't care.  

Thanks. I saw some air gas tags. Will have to look closer to see if there is an expiration date on them. Or a recertification date. 

Cut them up and fire up the welder and and make a really cool wood stove and / or a smoker?

In reply to dean1484 :

The acetylene tanks will require a little more work, they ain't hollow.

I was meaning to look at ours at work.  They stamp into the tank the test dates.  Sometimes they are really old but look decent.