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Old November 25th, 2011, 05:06 PM   #1
Kodiak450r
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Default converting a propane tank into an air tank

i'd like to know if anyone has converted a large propane tank into an air holding tank before, and if there is a way to figure out it's capacity. my plan is to buy a air compressor head which i have found i can get pretty cheap, and hook it to a large propane tank. i know propane tanks are measured in weight capacity i.e 20, 40, 60 lbs etc. but how do you figure out the gallon size of the tank? i have found 60lb and 100lb tanks on craigslist for pretty cheap as well. i have figured out that basically i can build my own large capacity air compressor for approximately 1/2 what it would cost to buy one new.
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Old November 26th, 2011, 02:10 PM   #2
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no ideas huh? my main question is how do i convert tank size into gallons of air capacity?
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Old November 26th, 2011, 02:29 PM   #3
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4.24 pounds per gallon.

Worthington forklift tanks are 10 gallons.

Large bulk tanks are typically in gallons.
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Old November 26th, 2011, 02:30 PM   #4
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A 20-pound tank holds about 4.1 gallons of liquid propane.
4.2 lb per US gallon
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Old November 26th, 2011, 06:19 PM   #5
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ok so when you buy an air compressor and it says 60 gallon, it does refer to how much liquid it could hold. that helps my understanding a bit.
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Old November 26th, 2011, 07:58 PM   #6
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you do know the burst rating for an air tank and a propane tank are different
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Old November 27th, 2011, 07:56 AM   #7
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What are you using this for?

Read this consider all the cost/time. Then reconsider building one.
http://www.cadvision.com/blanchas/54...reservoir.html

If you have the stuff already laying around or are getting for free go nuts. If not go out and buy something that is already built. In many cases you can not reduplicate the same product for less.
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Old November 27th, 2011, 08:22 AM   #8
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Quote:
Originally Posted by cerial View Post
What are you using this for?

Read this consider all the cost/time. Then reconsider building one.
http://www.cadvision.com/blanchas/54...reservoir.html

If you have the stuff already laying around or are getting for free go nuts. If not go out and buy something that is already built. In many cases you can not reduplicate the same product for less.
thats pretty much what i want to do is build a home air compressor. my problem with just buying one is this. even the cheapest 60 gallon compressor on the market from harbor freight is 800 bucks. i have not found one cheaper that is worth my time. so i can build my own for at least half that. i can buy a twin cylinder compressor head that puts out 145 psi max pressure, and can deliver 15.2 scfm at 90psi. cost is only 169.99. i have found 100 gallon or bigger propane tanks used all the time for pretty cheap prices.

hancho mentioned burst rating for the tank so i will have to research that see if it will work.
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Old November 27th, 2011, 12:35 PM   #9
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You will never get the rotten smell out a propane tank.
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Old November 27th, 2011, 01:16 PM   #10
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Quote:
Originally Posted by High Center Hancho View Post
you do know the burst rating for an air tank and a propane tank are different
X2, and do you realize what a propane tank that is pumped up to 145# could do if it were to burst? there is a reason that pressure vessels are all certified. Are you going to be welding more ports in it or are you just going to use the one that is there?
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Old November 27th, 2011, 01:55 PM   #11
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X2, and do you realize what a propane tank that is pumped up to 145# could do if it were to burst? there is a reason that pressure vessels are all certified. Are you going to be welding more ports in it or are you just going to use the one that is there?
from my recent research a propane tank can withstand up to 200psi without a worry. i would also be installing a pressure relief valve just like all air compressors have anyways. i would only have 3 holes in the tank. inlet, outlet, and tank drain. as for the smell i have read from other places if you flush the tank out with soapy water it gets rid of the smell.
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Old December 6th, 2011, 04:43 PM   #12
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Ive read horror stories from people trying to turn LP tanks into smokers. When they cut, weld, tap anything like that into a tank, even drained, they turn into a frag grenade....Just sayin...
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Old December 6th, 2011, 04:55 PM   #13
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Originally Posted by BigBlkYJ 355 View Post
Ive read horror stories from people trying to turn LP tanks into smokers. When they cut, weld, tap anything like that into a tank, even drained, they turn into a frag grenade....Just sayin...
So you're requesting a live webcast while welding is being done? Purge it with any inert gas while welding and it won't blow up. I'm guessing you suck ass at welding and you are going to fukc something and it is going to blow up.
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Old December 6th, 2011, 05:15 PM   #14
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To figure out the capacity you could measure it and used this little trick I learned in school called "math" to find the volume.
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Old December 6th, 2011, 07:40 PM   #15
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To figure out the capacity you could measure it and used this little trick I learned in school called "math" to find the volume.
that would be great if i had one in front of me to measure. but since so many people suck at posting shit for sale it's hard to get anything useful from an ad on craigslist or anywhere else. the whole reasoning behind me asking this question is so i know what size tanks to look for when shopping for one.
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Old December 6th, 2011, 09:14 PM   #16
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Quote:
Originally Posted by BigBlkYJ 355 View Post
Ive read horror stories from people trying to turn LP tanks into smokers. When they cut, weld, tap anything like that into a tank, even drained, they turn into a frag grenade....Just sayin...
This is stupid. We cut them all the time.

As it sits propane boils at -44 degrees F so my educated guess is that a standard 330 gallon propane tank would be your best bet to use. They are well over a 1/4pm thick and plenty strong for a air compressor. In Michigan propane is almost always boiling inside it's tanks, creating lots of pressure, that is what you draw off when you burn propane. Along as your not a retard (so far the OP is not out of the water on this) you should be fine. Having worked in the propane industry for a while I feel comfortable saying the tanks are fairly durable, way more durable than any air compressor tank I've ever seen.
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Old December 6th, 2011, 10:25 PM   #17
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Originally Posted by Fullsize4life View Post
This is stupid. We cut them all the time.

As it sits propane boils at -44 degrees F so my educated guess is that a standard 330 gallon propane tank would be your best bet to use. They are well over a 1/4pm thick and plenty strong for a air compressor. In Michigan propane is almost always boiling inside it's tanks, creating lots of pressure, that is what you draw off when you burn propane. Along as your not a retard (so far the OP is not out of the water on this) you should be fine. Having worked in the propane industry for a while I feel comfortable saying the tanks are fairly durable, way more durable than any air compressor tank I've ever seen.
I wouldn't have any problems with the propane tank itself, just the modifications made to it. I am a pipe welder in the industrial refrigeration field so I am very aware of the pressure fluctuations of propane with different temperatures. (propane shows very similar characteristics with ammonia except different temp ranges) modifications made to a pressure vessel aren't very smart to do by an unqualified person. If he had a certified pipe welder do it I would say it is fine and dandy.
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Old December 6th, 2011, 10:35 PM   #18
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reading http://www.propanecarbs.com/propane.html

looks safe to me??

on a summer day seeing 100-120 F outside is possible - that would place your tank pressure well above 150psi. Not my first choice for an air tank, but it is thinking outside of the box.
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Old December 6th, 2011, 10:41 PM   #19
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Are propane tanks heat treated after they are welded? If so are you planning on having the tank re treated after you weld to it?
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Old December 7th, 2011, 08:36 PM   #20
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Quote:
Originally Posted by chadcooper55 View Post
Are propane tanks heat treated after they are welded? If so are you planning on having the tank re treated after you weld to it?
i don't think tanks are heat treated but i could be wrong. that wouldn't be a problem if it needed to be done as one of my customers is Heat Treating Services of michigan. i could very easily have any one of their 3 plants heat treat the tank for me. as far as welding fittings into the tank i would have it done by one of the guys i know at Clawson Tank that lives down the street from me. he is a certified pipe fitter/welder, and he has a really good welder to do it.
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