Propane Tanks as Air Reserve Tanks or Make another Compressor

[Fortunateson]

I picked up a 42 and 80 gallon used propane tanks off a couple of trucks today. THe smaller looked brand new. I thought I would use them as extra air tanks for my air compressor or attach spare compressors and motors to run them. My question is how would I purge any vapours before welding on them? Soap and water, pump CO into them, or what?

 

[flyingblind]

http://www.garagejournal.com/forum/showthread.php?t=56583&highlight=propane+tank
search is your friend.
Apply water and weld after dry. or apply fire and then weld after fire goes out

 

[Farmall 1066]

Water and weld worked for me. Built a portable one years ago using 100# tank.
Smell never did go away completely. 25 years ago, and cousin has it now.
Still stinks!

 

[Kaizen]

I put a bottle of dish detergent and water in mine before cutting. no issues

 

[slip knot]

I've made a lot of barbeque pits from old propane/butane tanks. I'll fill them with water to the cut line prior to cutting. So far I haven't had any issues, but a bud of mine banged on the side of one just as I cut into it. bout crapped myself there.

 

[KRB52]

Keep in mind that there may still be propane in the metal pores that will come out and mix with the air in the tank. Said propane may get into tires you inflate with the spare tank or be exhausted from an air tool you run with it. I wouldn't use it for any sort of breathing air source. Biggest question is: is the grief that they may cause offset by the price you paid for the two tanks?

 

[RWorth]

If anyone wants it I have a 100 lb propane tank you can have if you come and get it. I changed over to 40's, easier to handle.

 

[LS6 Tommy]

Propane tank compressed air conversions are a pretty good way to build a potential bomb in your shop...

Tommy

 

[m91196]

Propane tank compressed air conversions are a pretty good way to build a potential bomb in your shop...



Tommy

Exactly, especially for the minimal benefit.

If you need a portable reservoir they are cheap, otherwise what are you really accomplishing.

 

[like2wheel]

Keep in mind that there may still be propane in the metal pores that will come out and mix with the air in the tank.

Any facts to back this up?

My BS meter goes off every time I hear people talking about metal "pores"..

 

[doorfx]

I don't think the smell from the ethyl mercaptan will ever go away.

 

[PugetDude]

Any facts to back this up?

My BS meter goes off every time I hear people talking about metal "pores"..

...+1

 

[Fortunateson]

Propane tank compressed air conversions are a pretty good way to build a potential bomb in your shop...

Tommy

Can you explain why? If propane is heavier than air and I invert the tank shouldn't any traces eventually bottom out the existing open holes? It is propably just the warning additive I would like to get rid of.

 

[flyingblind]

Crystal Defects:



Metallic crystals are not perfect. Sometimes there are empty spaces called vacancies, where an atom is missing. Another common defect in metals are dislocations, which are lines of defective bonding. Figure 6 shows one type of dislocation.

http://depts.washington.edu/matseed/mse_resources/Webpage/Metals/metalstructure.htm

 

[blazemaster83]

Years ago I had an old 25 gallon propane tank that I got for free. I wanted to cut it in half so I looked up what to do. Everyone said to fill it with water and you'll be fine....


So I fill it up, wait a few hours then pour it out. I had the tank up on some saw horses with the spout towards the ground so It would empty out. After it was empty I decided to pass a torch in front of the hole in the tank to see if there was any residual propane. The thing lit up like a rocket, and shot a 2 foot blue flame like a jet out of the hole. It also made a hell of a noise, like a giant bottle rocket. Scared the hell out of me.

So obviously it wasn't empty, I filled it up with water again. Wait a few hours like before, empty it. Same damn thing again, pass a torch in front of it and the thing lit up. Blue jet blast, and bottle rocket noise. This time I was sort of expecting it, but still shook me up.

The third time, no jet blast. But I learned I will never cut/weld/burn/etc. any propane tank ever again.

 

[Fortunateson]

http://www.garagejournal.com/forum/showthread.php?t=56583&highlight=propane+tank
search is your friend.
Apply water and weld after dry. or apply fire and then weld after fire goes out

So you say "flare" off any remaining gas? By the way all, I have to check if these were propane or LNG tanks. Only paid $20 for the pair.

 

[flyingblind]

So you say "flare" off any remaining gas? By the way all, I have to check if these were propane or LNG tanks. Only paid $20 for the pair.

A little research will show that people have just pulled all the valves and plugs then allowed the tank to breathe for a while and apply flame. Any remaining gas will just ignite like a candle.. I personally just purged them with water and go. I think there are a few videos that show the process. I use one for a sand pot pressure pot that attaches to a pressure washer.

 

[CNGsaves]

So you say "flare" off any remaining gas? By the way all, I have to check if these were propane or LNG tanks. Only paid $20 for the pair.

I can guarantee you those were NOT . . . . LNG . . . (liquid natural gas) tanks as the MWP (max working pressure) of those are in 5,000 psi to 10,000 psi range or MORE.

+1 that you need LOTS, and LOTS more research if you even hope to convert these likely propane tanks for use as pressure vessel for compressed air.

Many people have been killed by NOT knowing what the hell they've been doing. Say for instance, the tank instead was CNG (max pressures in 5,000 psi range) and you blindly starting taking out valve or plug, it could launch the plug right through your body and side of pickup bed like it was slicing through butter.

Be super careful is what I'm saying.

Finally, if you have no experience or certification welding pressure vessels (ANY thing including low pressure propane or compressed air), then step away from the plasma or oxy torch or welder . . . .OR . . . you might be in the news tomorrow.

POST Up PICTURES of these tanks and their labels:

 

[Firebrick43]

Keep in mind that there may still be propane in the metal pores that will come out and mix with the air in the tank. Said propane may get into tires you inflate with the spare tank or be exhausted from an air tool you run with it. I wouldn't use it for any sort of breathing air source. Biggest question is: is the grief that they may cause offset by the price you paid for the two tanks?

And yet you probably have gasoline cars, mowers, and cans in your shop/garage?

Gasoline has lower flash points than propane and vapors are more volatile.

Yes you need to wash a tank out properly, remove valves and vent for a day or two before cutting it but after its back in service, as long as the tank is sound, there is no problem running the very few molecules into tires or air tools?

Also propane is odorless. Therefore to help people identify a leak they add mercaptan oil. The oil itself is persistent not the propane.

 

[Milton Shaw]

Why not just get some old R22 tanks and use them. Same size as a 20 lb tank and never has explosives in it.

 

[Fortunateson]

Looking at them this morning I think I only have to weld on some legs/feet. Perhaps one bung for a drain on the larger tank. Fittings, line, valves have been remove quite some time ago. I plan on using plugs for the holes that I won't be using. Yeah, that mercaptan oil, I had forgotten the name, is lingering. Maybe I will try the tomato juice idea. I also have some tank sealer sitting on a shelf that I could through in as well so no rust forms. Basically got them at a reasonable cost and want to use one for sure as an extra reservoir for the air supply on a sandblasting cabinet. These are not 20lb tanks, see original post.

 

[pcmeiners]

"Propane Limits of Flammability - The lower and upper limits of flammability are the percentages of propane that must be present in an propane/air mixture. This means that between 2.15 and 9.6% of the total propane/air mixture must be propane in order for it to be combustible. If the mixture is 2% propane and 98% air, there will not be combustion. If the mixture 10% propane and 90% air, combustion will not occur."

In any propane tank, if the air is replaced a couple times before using it as a receiver, there is no way it could have 2.15% or more propane in it, mercaptan smell or not.

 

[OccupantRJ]

I don't think the smell from the ethyl mercaptan will ever go away.

Tomato juice helps. If you think diluted form stinks, wait until you get a whiff of the undiluted.
It makes most people gag and or puke. I won't even buy it until a couple days before I receive a load of gas. That's right, a butane tanker going down the highway can have 8,500 gallons of unscented fuel in it. if it crashes, how will the average person know it is gas? UN1075.