Had another idea...

Mark42

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Re: Had another idea...

When I was a kid I worked for a guy who had a lawnmower repair shop in his garage. He had a compressor hooked up to a propane tank like the ones used on gas grills. Never gave it much thought, but I wonder if the old (5 gallon? ) propane tank would hold 100psi? At least its designed to contain internal pressure of some magnatude. How many psi does it take to liquify propane?
 

angus63

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Re: Had another idea...

Liquifying propane is done by cooling the gas to appx -40 F. You can then maintain it as a liquid by raising the pressure which raises the boiling point. Propane's boiling point at 200 psi is about 100 F. At room temp, std 20# propane tank is at appx 90-110 psi.
 

Limited-Time

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Re: Had another idea...

BTW, SgtMaj the numbers in my second post are more than a guess.;);)
 

angus63

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Re: Had another idea...

BTW, SgtMaj the numbers in my second post are more than a guess.;);)
Capt L-T----They are accurate calculations of the area and the resultant system loads, but do not address whether or not the stresses imposed on the tank exceed the materials yield point, which is the critical design point in vessel design. If you used the same approach on a scuba tank, nobody would ever strap one to their back because the system loads seem astronomical. Use your same calcs on an 8" dia x 30" long scuba tank at 1500psi and ask yourself would you wear something with that much resultant system load on your back?
 

Limited-Time

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Re: Had another idea...

Capt L-T----They are accurate calculations of the area and the resultant system loads, but do not address whether or not the stresses imposed on the tank exceed the materials yield point, which is the critical design point in vessel design. If you used the same approach on a scuba tank, nobody would ever strap one to their back because the system loads seem astronomical. Use your same calcs on an 8" dia x 30" long scuba tank at 1500psi and ask yourself would you wear something with that much resultant system load on your back?

angus63, you are correct about the material properties. I just figured when SgtMaj saw the load numbers he would realize there is no way a 55 gal drum could be expected to hold them.
 

Tail_Gunner

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Re: Had another idea...

Ayuh,.... That Does Work,... I've done it Many times,+ still use a 100lb.er for added reserve Now....



Ayuh,.... You Really Don't understand Anything about Pressurized Air,... Do You.?...?.

10psi is Not very much,.....

100psi is More than enough to Kill you.......

Pressure vessels have Rounded ends,+ No Corners such as at the top,+ bottom of a 55gal. Drum.....

It's at the corners where it'll Explode from....


:D Pay very close attenion here.....God a 55 gallon drum was not made to contain A PRESSURIZED LIQUID OR GAS... but then again everyone is entitled to drink his or her's own cup of dumb A@@.... Damm im a polictical monster am i not..:D
 

Nandy

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Apr 10, 2004
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2,145
Re: Had another idea...

Even if the barrel was to hold I cant imagine the motor of the compresor will last too long having to work in a load 100 times larger than the original.[/quote



Nandy, that same compressor could fill the Hindenberg to 100psi and not experience any more "load" than the one gallon tank it is filling now. The only difference would be the length of time the compressor would operate at the same load until the volumetric difference was made up. Fluid power is very deceptive. Ten psi is dangerous. Ten psi in a six inch cylinder will lift your 275lb mother-in-law easily. Pressure vessels are seamless and rated at appx 75% of their calculated allowable stress. "Hoop stress" in a pressure vessel is (press x rad / thick). If a vessel was seamless and had full spherical ends, a 30" dia barrel that was .06 thk made of steel with a tensile yield strength of 30,000 psi would be rated as follows:

Rated psi = thk x (allow. stress) / largest radius
PSI= .06 x (75% of 30ksi) / 15
Rated PSI = 90​

a 55 gallon barrel that is flat ended, sealed by coining and not welded, and chock full of discontinuities would not be rated, but as stated many times, fun to watch go boom from a safe distance!​

Spent many years designing pressurized aerospace heat exchangers and the engineer nerd in me is overpowering and escapes often.​

The engineer in you should remember that when a company makes a product their parts are "generally" strong enough to do their job. Specially the low end quality ones. That that motor will take way longer to get that tank filled with the pressurized air, I see an early failure of the motor due to overheating or just plain ***** out of the parts earlier than design.

OH, btw, if we are pulling ranks, I spent many, many, maaaaany days in the Holiday Inn... ;)
 

angus63

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May 20, 2002
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Re: Had another idea...

No rank pulling, just the facts. Actually, a larger accumulator tank will result in the compressor having longer cycle periods after the initial fill up because it will require using much more CF in order to produce a differential pressure. If your window airconditioner continually short cycled instead of running and resting, it would have a much shorter life cause start up is the hardest duty a compressor sees, especially without an unloader. Getting into the nitty gritty so I'll stop now
 

SgtMaj

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Nov 19, 2007
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Re: Had another idea...

Just thought I'd throw an update out there for ya'll... bought a single fitting to fill it with... (didn't get the second fitting and hose to use it with because I just wanted to test it and see if the barel would hold up. Installed the fitting easily enough, tried to fill it... had VERY predictable results... Didn't explode though.

Turns out, it's pretty hard to pressurize a drum with a hole in it. :D It had a tiny hole near the top that I didn't even see the first time around... about the size of a nail. Turned it into a rain barel instead. Works great as a rain barel. :)

Oh, by the way dimock44, try getting them from a car wash. I'm getting mine from simoniz car wash. If no one get's them, they just have to cut them up and throw them out, so it's better for the environment, and better for simoniz, and better for me, for them to give them away. It's a win-win-win. :)
 

dimock44

Petty Officer 1st Class
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Sep 7, 2007
Messages
275
Re: Had another idea...

Just thought I'd throw an update out there for ya'll... bought a single fitting to fill it with... (didn't get the second fitting and hose to use it with because I just wanted to test it and see if the barel would hold up. Installed the fitting easily enough, tried to fill it... had VERY predictable results... Didn't explode though.

Turns out, it's pretty hard to pressurize a drum with a hole in it. :D It had a tiny hole near the top that I didn't even see the first time around... about the size of a nail. Turned it into a rain barel instead. Works great as a rain barel. :)

Oh, by the way dimock44, try getting them from a car wash. I'm getting mine from simoniz car wash. If no one get's them, they just have to cut them up and throw them out, so it's better for the environment, and better for simoniz, and better for me, for them to give them away. It's a win-win-win. :)

Thanks for the tip Sarge, but don't tell anybody else or I'll have to get on a waiting list to get mine.:D
 
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