Can a propane tank be repurposed?

[W8BYA]

I will admit to my total ignorance when it comes to pressurized storage containers and could use some help. I have had no luck trying to find answers to most of my questions on the net.

Here is an idea I have had for years and wondering if it can be safely pulled off. The goal would be to have a pressurized utility sprayer that I can carry around with me for spraying roundup etc. I am tired of pumping my 2-3 gallon sprayer every several minutes. I have a 5-gallon backpack model but once full I have a hard time getting it on/off by myself and it hurts my lower back as I walk around my 6 acres. I like the idea of a smaller, pressurized, hand held 2-3 gallon sprayer. I know they make battery powered units but I like to experiment & was wondering if an empty propane tank be repurposed (refilled with air) to provide the 10 PSI that I need? I do not think the high pressure paint-ball tanks is what I want as they are thousands of PSI and expensive.

I have long wanted to take an empty (small torch sized) 1-pound propane tank and refill it with air via my shop air compressor and try out my idea. I would attach a regulator to knock down the high pressure air down to ~10 PSI.

My 1st & most important question is what PSI can these small 1-pound propane tanks hold safely? The last thing I would want is to set my shop compressor too high & have a catastrophic failure due to too much pressure while refilling it. The next question would be where can I get a low-pressure regulator with a gauge so I can dial in the PSI into my 2-3 gallon sprayer.

 

[fishdrivel]

Not touching this with a 10 foot pole.
Compressed gas containers kill a lot of people!

 

[W8BYA]

Not touching this with a 10 foot pole.
Compressed gas containers kill a lot of people!

So everyone who refills their propane tanks with a larger propane tank is at a high risk of killing themselves?

 

[3gunr]

Buy a 15 or 25 gal spot sprayer, put it on your tractor in one of several places handy plug in to battery and spray all you want without the trouble you are looking at with your method.

 

[W8BYA]

Buy a 15 or 25 gal spot sprayer, put it on your tractor in one of several places handy plug in to battery and spray all you want without the trouble you are looking at with your method.

Appreciate the idea......would be fine but this is not for spraying hundreds of feet of fence lines or tree lines etc.....way too much close in spraying that must be done on foot.

 

[LouNY]

Hundreds of U-tube videos of converting propane tanks to air tanks.
If I was going to do one I would use an 80psi relief valve.

 

[LouNY]

According to the national standards publication NFPA58, a propane tank with 20 pounds (5 Gal) of gas at 70°F would have a pressure of 145 psi; at 90°F

 

[duffer]

There is a reason why propane tanks have an expiration date. Much of the reason is the stress that the tank gets during the 10 yr life cycle. Pressurized, depressurized, rinse & repeat for 10 yrs. Much like an airplane that needs to be re-fit on a regular basis. Add to that, the fact that the vast majority of propane tanks sit outside in the weather, and they're made of steel that rusts, adds to the instability of the tank over time.

Human nature is to take things to it's limits. If you pressurize the tank to 5-10 lbs you won't be able to spray your herbicide for very long without repressuring the tank. Tempation will kick in and you'll up the pressure to have a longer "charge". That's when you'll likely get into trouble.

Do what you want, but I'd heed the advice of most of the other posters to find a different solution than a propane tank, and stay out of the E.R.

 

[W8BYA]

Hundreds of U-tube videos of converting propane tanks to air tanks.
If I was going to do one I would use an 80psi relief valve.

Can you reference a couple of them where the person actually knew what they were doing and knew the safety limits of the tank etc? I do not mean for that to come out wrong or disrespectful because I appreciate your input but just because I see someone doing something on YT does not automatically mean it is safe to do.

 

[W8BYA]

According to the national standards publication NFPA58, a propane tank with 20 pounds (5 Gal) of gas at 70°F would have a pressure of 145 psi; at 90°F

Awesome that you referenced a standard. Thank you. Do you by chance know the PSI for a standard 1-pound tank?

 

[LouNY]

I would expect that it is very similar as they are both filled with liquid propane and then we draw the vapors off with the valve at the top.
A few years ago it was common to refill the small tanks from a 20#, you had to invert the 20# to get liquid to transfer to the little tank.
Otherwise it had very little volume.

 

[W8BYA]

There is a reason why propane tanks have an expiration date. Much of the reason is the stress that the tank gets during the 10 yr life cycle. Pressurized, depressurized, rinse & repeat for 10 yrs. Much like an airplane that needs to be re-fit on a regular basis. Add to that, the fact that the vast majority of propane tanks sit outside in the weather, and they're made of steel that rusts, adds to the instability of the tank over time.

Human nature is to take things to it's limits. If you pressurize the tank to 5-10 lbs you won't be able to spray your herbicide for very long without repressuring the tank. Tempation will kick in and you'll up the pressure to have a longer "charge". That's when you'll likely get into trouble.

Do what you want, but I'd heed the advice of most of the other posters to find a different solution than a propane tank, and stay out of the E.R.

Appreciate that guidance. But I think we are talking about two different propane tanks. I am wanting to learn more about the small 1-pound propane torch tanks.

Also, the 10-15 PSI is the intended pressure inside my sprayer bottle. I would imagine the air-filled propane tank would be filled to 40-80 PSI (not sure).

And you bring up a great point about a 10 year life cycle. Is that for the small 1-pound tanks as well? If so I have no problem buying a new tank, emptying it, filling it with air and using it for 5-6 years then replacing it.

Most importantly I am on a fact finding mission here. I am asking because I do not know and if it sounds like a gray area I will simply stay away from it and get a battery powered unit. It is just you see thousands of VERY high pressure paint-ball tanks filled every day....I just wonder if the 1-pound propane tank can be refilled just like them.

That also just made me wonder if I could use a paint-ball tank that is very high pressure and regulate it down to 10 PSI and then use it?

 

[W8BYA]

I would expect that it is very similar as they are both filled with liquid propane and then we draw the vapors off with the valve at the top.
A few years ago it was common to refill the small tanks from a 20#, you had to invert the 20# to get liquid to transfer to the little tank.
Otherwise it had very little volume.

Roger that ! I have filled several 1-pound tanks using a 20# tank several times......exactly as you say, just make sure it is inverted so you fill it with liquid. Never had any problems but since I do not have any gauges on the setup I was at a loss at what the internal PSI was. TU agn.

 

[Rustyiron]

1 gallon pump up sprayer is about 10 bucks at HD. Much lighter and takes very little pumping.
I've also added a valve stem to this type of tank before if you absolutely don't want to pump. Just be prepared to walk back to the shop to refill it.

 

[Doughknob]

So OP i think you’d find even if you did what you initially posted, that ‘volume’ in the torch tank WAAAAY to little for what you need in 2 gallon sprayer.

 

[Eagle1]

All this worry yet how many put 120 PSI in a 50 year old portable air tank? Who changes their air compressor tank every 10 years? The stresses are same, just air is not flammable.

 

[Smokeydog]

With so many kinds of readily available sprayers to purchase why shake hands with danger? Large or small propane cylinders are not coated inside to resist corrosion.

Paint ball and SCUBA tanks are only meant for dry air.

There are some quart to several gallons spray containers made to be pressurized using a air compressor and are vary expensive.

It’s good that you ask a question. Hopefully you can understand why it’s not a good idea.

 

[lpakiz]

To give you a simple answer to a simple question.....
Propane pressure is linear to its temperature. Doesn't matter if in a 1# camping bottle or in the tank of a 8,000 gallon railroad car, or any size in between, including the 20 pound tank on your grill outside.

It matters not if the bottle, tank or tanker has 1# , 3 gallons, or 1,000 pounds or 8000 gallons. Temperature decides pressure of the liquid (and gas) inside that container. I didn't Google it for exactness, but 250 PSI is easily possible in a grill tank, in the sun, on your deck.
That said, you better know what you are doing before you introduce regulated pressure into another vessel not designed (or SAFE) for the resultant pressure. There are safeguards built in to all propane vessels for a reason. 20# and larger tanks have a stamp on the side indicating max working pressure.
BTW, I use a 100# propane cylinder, hung upside down from my shop ceiling for my air compressor receiver. I've had it for 40 years or so. My compressor is set to shut off at 150 PSI. Actually, I think it's heavier metal than the tanks of commercially built air compressors. I also use 20 pounders for portable air tanks. One just needs to get the right plumbing to make this work.

 

[JJT]

I converted a 20 pound propane tank to an air tank, 20+ years later it still smells like propane. I don't think the mercaptan smell ever goes away.

 

[grsthegreat]

Think backpack sprayer. Nice easy to use handle to pump while its on your back. ive used them for years. Very easy to use and walk thru brush. All weight on back, not arms.


edit: sorrt..i reread your post, and see you tried backpack sprayer. Problem is even a pressurized unit will need to be carried around, and holding them in hand sucks.