Propane tank PSI

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When re-filling a propane tank...what is the PSI? Anybody know?

[memtb]

naturist wrote:
Back in the day we used to use old propane tanks for compressed air at 100-125 psi for tire reinflation after being on the beach or for extra air when running the sports car in autocrosses and hillclimbs. Did it for years. If you put a water separator on the compressor, shouldn't be a problem with internal rust for many years.

Also, used them at tracks when racing motorcycles. Still have and occasionally use the same bottle I used when racing 40 years ago!

[nineoaks2004]

To save all the trouble and cost of making one, you can buy a 5 gal air tank with hose, fittings etc. at HF for $29.95 and 20% less if you have the coupon, they have larger tanks too. I have used one for years.

[Jetstreamer]

You can figure propane pressure at roughly twice the ambient air temp.

[myredracer]

People do it all the time. Propane tanks have a higher psi rating than air tanks and you'd probably never be anywhere near the max rating anyway. What size of tanks and what use?

If for a compressor setup, you need to provide a means of draining water out at the low point, either with a manual valve or auto-drain valve. I have a 60 gallon upright compressor with an auto-drain and it blows a puff of air and water out every time it pumps up and shuts off. There's a crazy amount of water that comes out of the tank when it gets regular use. For a portable tank (no compressor) you'll be fine without a drain. The odor they put into propane is apparently hard to remove.

Do not weld on the tanks (if needed). They are pressure vessels and you'd need a welder certified to work on them to do that. A good place to ask this sort of question is on the garagejournal.com forum like these couple of examples here and here.

It could be that at the end of the day it'd be cheaper and easier to just by an air compressor tank. Then you could repurpose the tanks into a fire pit, artwork or BBQ.

[Allworth]

My store ALWAYS has the flashlights (and the great tin-foil bladed screwdrivers).

[wa8yxm]

I followed hte Google knows link someone posted (Thanks) because. Well I wondered about that as well

The article I got to showed pressures at two common tempertures and 100 PSI plus or minus about 30 was the range they had. Of course the hotter it gots the more pLUS (128 at 80 degrees F) and tegh coldwer the less (Zero at -40)

[JaxDad]

Johno02 wrote:
It is not recommended to use ropane tanks for air. According to what I have heard, compressed air usually has a good amount of water in it, and propane tanks are not sealed inside. Again, according to what I have been tolde, continued use of air will cause moisture inside and rust, leading to failure, which could be very bad, depending on the instance. So not my opinion, just what I have been told, but I wouldn't do it.

The simple solution for that is to invert the tank and drain it after use, the water settles into the opening and is the first thing out with a head of air behind it.

[Ralph_Cramden]

Johno02 wrote:
From the web:

More on propane tank conversion...
by: Anonymous

A propane tank has to be made to withstand over 140 psi as propane becomes a liquid at 140 psi (at room temperature), any container with a mix of liquid and gaseous propane will be pressurized to 140 psi, regardless of the ratio of liquid to gas. The major problem associated with using a propane tank as an air tank is that the tanks is just welded steel so one should coat the inside of the tank with a rust preventative paint and the tank new plumbing should allow for the draining of water from the tank. ie the tank should be upside down with a drain valve at the lowest level. Removing the old propane valve is the most difficult part of the conversion. After removing the valve por in the rust preventative paint put the valve back on temporarily and roll the tank and turn it end over end several times so the whole insides of the tank gets coated with paint. Remove valve, drain out excess paint and let the tank dry for several days before adding new pipes and valves. Include a pressure relief valve.

___________________
The writer, who chooses to remain anonymous, but did actually sign in as DUH (unfortunate name that) makes some valid points.

Good that a propane tank is built to withstand 140 PSI. But... what is it rated for in terms of higher pressure. That you need to find out as your typical DIY type air compressor will discharge 150 PSI, and some of the more industrial types will send 200+ PSI into the tank.

If the propane tank is rated with a burst pressure exceeding twice the maximum pressure the compressor would put into it, then sure, use it, along with the PRV set to blow off way below the burst pressure of the tank, as the writer suggests. The thing is, if you don't know the burst pressure of the tank, don't use it! At least as far as I'm concerned.

Holy cow, before I went through all that I think I would drop by Junk Harbor and drop $40 for one of their excellently crafted by Sum Ting Wong 11 gallon tote tanks. It even comes with a sort of accurate gauge and if you get the flyer you'll also get a free nevr N stock led flashlight.

[Old-Biscuit]

naturist wrote:
Back in the day we used to use old propane tanks for compressed air at 100-125 psi for tire reinflation after being on the beach or for extra air when running the sports car in autocrosses and hillclimbs. Did it for years. If you put a water separator on the compressor, shouldn't be a problem with internal rust for many years.

Carried a couple propane cylinders as compressed air cylinders for tire reinflation/repairs when off roading/rocking

Also carried a small propane bottle to use for 'bead setting'
Spray some propane around rim.....throw a match at it and 'whomp' ---
tire ready for inflation/bead set

[Ava]

At minus 40 degrees, F or C degrees, propane is like water, every degree higher in a sealed container it will boil until there is enough pressure to stay as a liquid. The hotter the temperature, the pressure it needs is whatever it takes to return to liquid state.

[naturist]

Back in the day we used to use old propane tanks for compressed air at 100-125 psi for tire reinflation after being on the beach or for extra air when running the sports car in autocrosses and hillclimbs. Did it for years. If you put a water separator on the compressor, shouldn't be a problem with internal rust for many years.

[Johno02]

From the web:

More on propane tank conversion...
by: Anonymous

A propane tank has to be made to withstand over 140 psi as propane becomes a liquid at 140 psi (at room temperature), any container with a mix of liquid and gaseous propane will be pressurized to 140 psi, regardless of the ratio of liquid to gas. The major problem associated with using a propane tank as an air tank is that the tanks is just welded steel so one should coat the inside of the tank with a rust preventative paint and the tank new plumbing should allow for the draining of water from the tank. ie the tank should be upside down with a drain valve at the lowest level. Removing the old propane valve is the most difficult part of the conversion. After removing the valve por in the rust preventative paint put the valve back on temporarily and roll the tank and turn it end over end several times so the whole insides of the tank gets coated with paint. Remove valve, drain out excess paint and let the tank dry for several days before adding new pipes and valves. Include a pressure relief valve.

___________________
The writer, who chooses to remain anonymous, but did actually sign in as DUH (unfortunate name that) makes some valid points.

Good that a propane tank is built to withstand 140 PSI. But... what is it rated for in terms of higher pressure. That you need to find out as your typical DIY type air compressor will discharge 150 PSI, and some of the more industrial types will send 200+ PSI into the tank.

If the propane tank is rated with a burst pressure exceeding twice the maximum pressure the compressor would put into it, then sure, use it, along with the PRV set to blow off way below the burst pressure of the tank, as the writer suggests. The thing is, if you don't know the burst pressure of the tank, don't use it! At least as far as I'm concerned.

[Johno02]

It is not recommended to use ropane tanks for air. According to what I have heard, compressed air usually has a good amount of water in it, and propane tanks are not sealed inside. Again, according to what I have been tolde, continued use of air will cause moisture inside and rust, leading to failure, which could be very bad, depending on the instance. So not my opinion, just what I have been told, but I wouldn't do it.

[BB_TX]

100 psi should be no problem. Propane in a tank can go well over 200 psi when hot. Good chart below. Plus lots of other good info.

Propane pressure