db New Reader
May 17, 2010 1:29 p.m.

I have a sand blast cabinet that I need a larger compressor to run, but don't have the cash for one the size I need.

I do have an old 100 water heater tank and was wondering about assembling one.

I found this compressor at HF http://www.harborfreight.com/air-tools/compressor-pumps/140-psi-twin-cylinder-air-compressor-pump-for-5-hp-motor-93786.html. The I would need a 5hp 220v motor. Anything else I would need, and ideas about how to put it all together?

Thanks.

4cylndrfury SuperDork
May 17, 2010 1:30 p.m.

make sure your welds are made of supermans hair - I dont trust mine at pressure

Woody SuperDork
May 17, 2010 1:59 p.m.

My grandfather built his own air compressor out of a refrigerator compressor and a steam tank, back when grandfathers made stuff because the needed to, and knew how.

Trans_Maro Dork
May 17, 2010 2:07 p.m.

Pressure switch, check valve, unloader (if it's not built into the pressure switch) drain valve and insurance that will cover what happens when the hot water tank lets go.

Shawn

Don49
Don49 New Reader
May 17, 2010 2:22 p.m.

If you have the electric available, just get another compressor the same as yours and run the air to a common line. You don't say what size you have now, but you can buy 5-7 hp compressors all day in the $5-600 range.

bravenrace Dork
May 17, 2010 2:31 p.m.
Don49 wrote: If you have the electric available, just get another compressor the same as yours and run the air to a common line. You don't say what size you have now, but you can buy 5-7 hp compressors all day in the $5-600 range.

Can I have a ride???

kb58
kb58 Reader
May 17, 2010 2:33 p.m.

Myth Busters showed that the tanks are good to about 340 psi or so... I still wouldn't do it. It's on YouTube.

stuart in mn SuperDork
May 17, 2010 3:09 p.m.

I doubt a water heater tank is rated for use for compressed air.

hamburglar New Reader
May 17, 2010 3:11 p.m.

Like said above, be aware of what compressed gases can do. Although compressed air isn't as hardcore as superheated steam, it can still get pretty hairy.

If you do decide to go this route, make sure you have some sort of bypass/safety valve to safely release pressure once you reach a set limit. Most compressors operate around 120 psi, which in THEORY your hot water take should be able to handle.

You will first have to remove and disable all the water related plumbing and plug those unnecessary holes...Stripping down the tank from its insulation is a good idea. I guess you would have to make some sort of frame to hold your tank and pump. For plumbing needs look to your smaller compressor for inspiration.

For the naysayers, the compressor I use weekly is cobbled together from bits and two bottom halves of 30lb propane tanks, made over 20 years ago.

njansenv Reader
May 17, 2010 3:57 p.m.

So, um.... what theory says that an old, possibly rusty hot water tank should be able to take 120psi?

120psi compressed air is way scarier than 120psi water....FWIW, I wouldn't do it.

Of course, I was taught thermo by a professor who lost the use of his legs when a air compressor let go....

RedS13Coupe Reader
May 17, 2010 4:10 p.m.
kb58 wrote: Myth Busters showed that the tanks are good to about 340 psi or so... I still wouldn't do it. It's on YouTube.

yes, but for how many cycles?

confuZion3 SuperDork
May 17, 2010 4:23 p.m.

Do I smell a new submission for Mythbusters?

Myth: A hot water tank can be transformed into an industrial air compressor without blowing up.

Result: They'll find a way to blow a few of these things up. Spectacularly.

SupraWes Dork
May 17, 2010 4:37 p.m.
confuZion3 wrote: Do I smell a new submission for Mythbusters? Myth: A hot water tank can be transformed into an industrial air compressor without blowing up. Result: They'll find a way to blow a few of these things up. Spectacularly.

Watch the episode, they did, it is very spectacular, I assume enough to make the OP give up this idea. At least I hope so.

Here's the short n dirty version

http://www.youtube.com/watch?v=Cv178a60Ypg

twolittlebroncos
twolittlebroncos New Reader
May 17, 2010 6:49 p.m.
Woody wrote: My grandfather built his own air compressor out of a refrigerator compressor and a steam tank, back when grandfathers made stuff because the needed to, and knew how.

Ditto - we filled up our bike tires with the refrigerator air compressor in Grandpa's garage.

44Dwarf HalfDork
May 17, 2010 7:36 p.m.

Yup I've still got a small compressor that uses a riveted tank. but we don't use it any longer.
Search Craig's list or other places find a real tank. I built my unit here at the house myself. Tank came from the local dentist office that upgraded compressors it was just a tank made in 65 but it is a certified tank unlike everything you'll find in the stores today. motor came out of a roof top a/c unit (customer replaced it do to age) the compressor Head came from a re builder place that had it on the shelf. motor frame is two guard rail I beams sitting on 6 old V8 engines valve springs. motors up stairs in the garage the tank is down stairs between the doors.

use a water tank = bad idea.

44

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