are they the heavy steel ones or the ones of the thinner metal disposable ones that you buy to fill balloons?

 

They are the heavy steel ones, about the same as the Oxygen bottles on a shop oxy/acetylene torch rig.

 

the only problem would be how do you drain the water out of them unless you mount them upside down, build a bracket on the wall and make a manifold out of black pipe to connect them with a drain on it..

 

Good point on the water, hadn't thought about that. What you suggest is very do-able and would solve the issue. Any idea if I would get enough volume out of them to make it worthwhile? My other thought was purchasing a 100 gallon propane pig for $90 and use that, but the helium bottles are free and unused.

 

the only problem with using tanks for compressors that werent made to be used is they can go BOOM and kill you.....old propane tanks make great bbqs, but unless you get it hydro tested I would stay away...what kind of compressor do you have?..the helium tanks wouldnt add that much volume for all the work...mabe just easier to buy a new compressor or buy a compressor with a blown motor or pump but the tank is still in good condition...

 

I wouldn't bother. Calculating based on a 6" I.D., those only give you about .2 (2 tenths) of a cubic foot of volume for every foot in height. Total volume increase would be negligible.

Radius = 3 so piR^2 = 28.27 square inches cross section. X 12 inches = 339 cubic inches per foot of length /1728 cubic inches per cubic foot = about .2 cubic feet.

Included the math because it surprised me...hope I got it wrong somewhere.

 

Math is basically fine, your conclusion needs a little adjustment.

There are 231 cubic inches per gallon.

So your math of 339 cu.in. is about 1.5 gallons per foot.

2 tanks at about 4.5 feet tall means 13.5 gallons of extra storage. Not terrible, but not a lot either.

 

By the description, they sound like 150' bottles.....Those things cost about 200 bucks each.......I'm not sure if they can be filled with argon or C-25 due to pressure ratings(stamped on bottle, check).

Like said above, pass on using them for extra air capacity, especially if you discover you can sell them...Yeah, I know about neck rings and all that, but it might be worth your time to investigate.

BTW, when we talk pressurized gas cylinder sizes/capacity, we state their cubic foot 'size' when filled with gas and compressed to bottle working pressure....So, ferinstance, a 1 cf bottle at atmosphere will only hold 1 CF, but same bottle will hold 150CF of same gas when compressed 150 times atmosphere pressure.

So calculate the inner volume of the cylinder, then factor in the working pressure to solve CF capacity....In your case, about 100-150psi.

But seeing how air compressor tanks are sold base on liquid gallon capacity, then those bottles of yours will give you about 4 extra gallons air storage capacity each.

 

I would sell them (get them tested first if they are out of date) and buy the compressor you have always wanted.
I would but a 580 valve on them for argon, C25, nitrogen, etc because they will sell easier than helium cylinders.
You can get a good 60 gallon air compressor for less than $500.http://www.tractorsupply.com/en/store/porter-cablereg%3B-stationary-belt-drive-air-compressor-60-gal

 

Damn, just buy a bigger compressor dude! Your small pump will burn up trying to fill all the extra tank capacity, you would lose all the $ your cylinders are currently worth, could be a dangerous project ( depending on your skill level), and you would waste hours building this contraption. A bigger air compressor is just such a better alternative to building one with multiple tanks.

 

Like wny said if you add more storage to a small compressor it will work longer on a cycle and might overheat. Yes, your air supply will last longer until the comp. kicks on, but it will work longer. You just need a comp. that puts out more CFM.
Mike

 

I'm not worried about these bottles or any of the plumbing exploding, they are solid, and I've worked with much higher pressure systems before. However, that said, it does make more sense to upgrade the compressor in the long run, I was just hoping not to get into the buy 1 tool and upgrade all the other tools, in this case at least it's only 1 tool. Thanks for the replies.

 

I found a used Speedaire 30 gallon standup 3 HP 220v with 11.4 CFM @40 PSI and 9.0 CFM @ 90 PSI for $330, more than enough CFM for the PM 45. So it looks like it's time to retire the old Juczzi Brothers v-Twin, nothing wrong with it except it doesn't have the CFM I need, man that was a sweet compressor, very quiet and trouble free for all the many years I had it. Probably best as they aren't around anymore for parts or service.

 

More capacity doesn't give you more CFM output. It will let you go slightly longer till you run out of air.

 

What ever you purchase. . . make sure you get a two stage compressor rated at 175psi.

 

Why? Many times a twin cylinder compressor will make more CFM than a 2 stage compressor will. 2 cylinders doesn't automatically mean 2 stage. A twin cylinder compressor has 2 LP cylinders, both taking air in from the atmosphere, and exhausting to the tank. A 2 stage has 1 LP cylinder that takes air in from the atmosphere and then that air goes to the 2nd stage HP cylinder where it's gets compressed again to a higher pressure.

If you don't need a lots of HP air, but need lots of volume, a twin cylinder may be a better choice. Depends. Some 2 stage compressors have larger LP cylinders to compensate for having only one intake cylinder and still will make CFM numbers comparable to some twin cylinder models. Other times the twin cylinder will win.

 

I was getting a propane bottle filled one time, and I asked the guy whether people ever bought old propane bottles from them to use as reservoirs for compressed air systems (I think I also asked him whether filling a propane bottle with water, then hooking it up to a pressure washer, was a safe way to hydrotest it at home and he said yes)...anyway, he ended up GIVING me a 100-gallon propane bottle for FREE. I haven't hooked it up yet, but I plan to, and it will increase my current pressurized-air holding capacity by 125%.

 

Where TF is he located so I can go get my free 100gallon tank?!?!? Lol

 

Here they are pretty hard to come by. I have a 100 gallon I got full when a neighbor's house changed hands. The new owners contacted the gas supplier a few times. They never came to get it. I took it a mile out in the national forest, opened the valve, and left it there a day. When I returned, the odor was overwhelming! I welded the base from a 25 gallon 3 HP Sanborn to the top of it. Used it for body work including paint, DA, and sandblasting for 30 years until the reed valves in the compressor got leaky. I never found new ones, so I replaced it. As an auxiliary tank, mount upside down, use a T with drain, a T at the compressor with even a small hose is fine.

At the same time I had a 1 HP Sanborn, The tank rusted out, I used a 100 LB propane tank, set it up horizontal with wheels, welded in a drain, and saddled the compressor on with threaded rods. I used to rent generator & compressor for house construction when a certain builder would jump the gun, and start construction before the power line. It'd run two nailers all day.

 

You don't have to retire your old compressor, connect two compressors together to get combined out put. ex 11cfm plus 4cfm will give 15cfm out put.
Last shop I worked at had 2 10 horsepower compressors paralleled. A couple tire shops around here run 2 cheap 5 horse compressors because its cheaper than 1 good 10 horse and if one fails they still have some air.
Peter

 

overall, totally not worth using helium tanks, or any other tanks that are rated to 2000psi, simply due to the weight and how little actual volume you will store @ less than 200psi. 2000psi tanks hold a lot of [any] gas because they are pressurized to exactly that: 2000psi.