Grille size Propane tank conversion to air tank

moonlight machine · Jan 5, 2008

I see you can buy a kit to convert a propane tank to an air tank for filling tires or wharever

how much preasure will one of these tanks hold? how much preasure is the propane under?

I saw the remains of a garage that had all the doors closed when a 20 or 30 gal cheepo

compressor tank blew up. killed a couple guys and removed about 1/3 to 1/2 of the siding

makes you think about the propane tank to air tank conversion idea

aboard_epsilon · Jan 5, 2008

propane is at around 90 psi in the big bottles.

all the best.mark

Jim Shaper · Jan 5, 2008

LP tanks are rated to 240psi per DOT requirements.

loggerhogger · Jan 5, 2008

a few years ago, a prvious manager at the Mt Rainier Scenic Railroad tried to use old propane tanks for air tanks for the flush system on the passenger car toilets. Trouble was that we could never get rid of the smell that is put in propane. Every time the toilets flushed, the entire train reeked, and it scaired the passengers because they thought we had a gas leak on the train. You can buy portable air tanks fairley cheeply, and they will be a lot less trouble to work with.

kdc · Jan 5, 2008

All the information I've been able to find on the much larger yard tanks is 250psi. The B-B-Q tanks are sold at hardware stores and should have the PSI on the tanks.

They did make conversion kits intended for the tanks that held freon at one time--don't know if this is still true. I had one and belive me they are much lighter than any air tank I ever bought. I never put more than 100-120 psi in it to fill a tire.

I have a tank that I rarely use because I found the little 12V compressors ($12-$20) are easier to deal with " IF " you have access to a vehicle with a battery. I've even carried a battery out in the field and made clips for the compressor so it's portable.They have $60 ones now,but I've burnt up 8-10 $10 ones over the years--actually they got destroyed when I loaned it out(every time) I no longer have one (that's my story anyway & I'm sticking to it).

The conversion kit costs $8 or so (Auto-Zone) ,but for most stuff like bike & car tires(my El Camino air shocks) The little compressor works easily & weighs a pound or two.

You didn't say why you needed the tank,but thought this might help.

moonlight machine · Jan 5, 2008

kdc I don't need one, I just saw the conversion kits and was wondering what the max preasure was for a little propane tank. they seem a little light to me..........

matt_isserstedt · Jan 5, 2008

"I saw the remains of a garage that had all the doors closed when a 20 or 30 gal cheepo
compressor tank blew up."

A good reason to get an ASME tank. They are designed to the "leak before break" criteria for a pressure vessel. (IOW a crack that potentially forms in the material is "shunted" by the material's ductility before it can propagate around the perimeter at the speed of sound in that particular material :eek:

)

Jim Shaper · Jan 5, 2008

240psi is the working pressure. Burst pressure has to be over 960psi or there abouts. Even running 175psi wouldn't be taxing it.

I'm actually considering ditching my 80 gal compressor tank (ASME, but 25 years old and rusty in the bottom) in exchange for a bank of 6 100# lp tanks that I would then store outside along the back wall of the shop. 100#ers hold about 30gal each and only have a 16" girth. Plus, I can get them for $5 each.

The mercaptan stink does suck, and I've never found a good way to eliminate it other than with the plasma cutter to the tank for cutting. Freeing up 8sq feet of floor in my shop would be nice though. I can then stick the compressor head and motor on or under a shelf out of the way.

kdc · Jan 5, 2008

It might be a little trouble to coat the inside with Fiberglass Resin (or Epoxy) like a rusty gas tank,but it might seal the odor. Since you only have $5 ea. in them you won't get hurt $$$$ wise. Just line them up and pour it in the first one & roll them around til coated inside--then pour the mixture in the next one and repeat til you run out of coating or finish them all.

kendall · Jan 5, 2008

Most info I've found states that the relief valve opens in the 380psi range, so they should be able to handle usage as an air tank.

Like the idea of several tanks ganged together, I've got a narrow spot that's almost unuesable at present, would open up the space used by the AC right now.

With no drain valve, would likely want to mount them upside down so the accumulated moisture could be drained fairly easily.

Ken

Jim Shaper · Jan 5, 2008

That's exactly what I was planning. Make a cage, then invert them screwed right onto a manifold with a solenoid valve on the tail end and a line into the shop on the other. Presto - push button water purge.

I already have 3 tanks out back waiting. One has the valve off and is inverted to try to let the stink out over the winter. I was planning on selling the other two, but the more I think about the external storage, the more I like it.

Btw, these tanks use standard 3/4" NPT threads. Plumbing them couldn't be easier.

As for the polyester resin coating idea, I'm not sure how well that would work. Mercaptan might not mingle well with the resin. I'm sure there has to be a solvent out there that will cut the stuff. I'm betting the govt doesn't want to publish it because it would make blowing up the ex-wife too easy. LP is odorless.

440roadrunner · Jan 5, 2008

aboard_epsilon said:
propane is at around 90 psi in the big bottles.

all the best.mark

Propane pressure depends on temperature, and it can be a hell of a lot higher than that. Propane tanks should be perfectly safe..........

until they get rusted, just like any other tank

According to this chart:

http://www.glacierbay.com/ptchartpropane.asp

On a hot day you could easily see pressures in the 200psi range, especially if the tank is seeing prolonged sunlight, in a hot area of the country.

Troup · Jan 5, 2008

I've made an LPG tank into an air tank for my compressor. No problems whatsoever. I cut away the sheetmetal upstand / handle, drilled out and TIG welded plugs into the unsuitable threads, TIG welded a few black sockets in for various needs, did a leak test, all sweet.
In my case the tank is lying on its side, and I drain the water by means of a copper tube, brazed to protrude straight into the tank from a brass nipple in the lowest outlet on the end face of the tank. When I worked out where the nipple tightened to (after a few iterations) I but a 90 degree bend in the tube so it just kissed the bottom of the tank at the lowest point (the tank is mounted sloping slightly to the end with the outlets)
I haven't noticed any smell; the tank had been empty and open to atmosphere for a few months. I have a rather poor sense of smell, mind you...

Weirsdale George · Jan 5, 2008

I have heard, but don't know if it is true or not, is that rinsing the tank out with chlorine bleach will reduce or eliminate the odor.

clampman · Jan 5, 2008

I use them for quick burst air through 5/8" radiator hose for a turret lathe bar feed and an air operated hydraulic clamping system. Just put the latter together a couple months ago. I filled it with water and let it sit a couple days before plumbing it. I don't notice any smell from it anymore.

Regards,
Jimc

Frederick Harvie · Jan 5, 2008

Troup said:
I've made an LPG tank into an air tank for my compressor. No problems whatsoever. I cut away the sheetmetal upstand / handle, drilled out and TIG welded plugs into the unsuitable threads, TIG welded a few black sockets in for various needs, did a leak test, all sweet.

A strong word of caution here. I would not do any welding a air tank unless you have the certification to weld Pressure vessels. This is an area that in most jurisdictions is highly regulated

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Grille size Propane tank conversion to air tank

moonlight machine

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aboard_epsilon

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Jim Shaper

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loggerhogger

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kdc

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moonlight machine

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matt_isserstedt

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Jim Shaper

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kdc

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kendall

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Jim Shaper

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440roadrunner

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Troup

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Weirsdale George

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clampman

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Frederick Harvie

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