SCUBA tank, on board air.

[Matt16]

I have a York compressor almost ready to go on my truck. It puts out 7cfm (the big ARB puts out 2 or something), so I dont even really feel I need a tank, but I'm worried that the pressure release (blow-off valve?) won't handle 7cfm and the pressure in the hose will increase past it's capacity before the compressor can turn off. Thus, I want some kind of cheap tank.

I found an old SCUBA tank (about 2' x 9") at a junk store with the original fittings. Are these NPT? Its steel I believe.

The other tank I found was an old aluminum pressurized kerosene tank for a kerosene stove. Again, not sure whether the fittings are NPT, but at least it has a shraeder valve.

There was also an old medical oxygen bottle, NPT?

[tc]

Not sure on the fittings. You certainly don't need a tank that big (and the space it takes up)

What pressure does the York run at? Could be too high for lockers, and another regulator on the output of the tank would be a good idea.

[Matt16]

Originally Posted by tc

Not sure on the fittings. You certainly don't need a tank that big (and the space it takes up)

What pressure does the York run at? Could be too high for lockers, and another regulator on the output of the tank would be a good idea.

Essentially I am looking for the cheapest safe tank that I can use that will fit above my rear axle. The York apparently puts out a massive 7cfm at idle at 90psi. That's what I've heard. The only reason I want a tank is because I don't think any blow off valve (?) can handle that much air and I don't want my lines instantly exploding the second I stop putting air into the tires, before the pressure switch cuts power to the electro-magnetic clutch on the York.

With a larger system volume, the pressure will increase slower and the pressure valve will have time to turn off the compressor without a huge spike in pressure.

[Matt16]

A semi wrecking yard is charging $40 for a 2 gal tank, which is a little much I think. This is a jury-rigged, budget project, cause all the NPT fittings are going to be the expensive part.

[premirrider]

Im thinking of using an old propane tank for my york compressor. Just my thoughts

[scuba]

Originally Posted by Matt16

I found an old SCUBA tank (about 2' x 9") at a junk store with the original fittings. Are these NPT? Its steel I believe.

So mine got stolen not too long ago, im guessing that stupid crack junkie took it to whatever junk store you got yours from...
Could i by it back...

[Matt16]

That s a bit of drive to go from San Diego to Vancouver, but those crack heads are pretty determined.

Do you know if scuba tanks are NPT, seeing as you have some experience with them.

[taikowaza]

I'm a scuba instructor and you've got to be careful with those old scuba tanks. There is a date stamped on the tank itself, that is a hydrostatic test date, if it's over 5 years it's not considered safe for a fill.
I heard a tank blow (luckily no one was in the compressor room when it happened)...
it left a very large chunk out of the wall heheheh
but all joking aside take that tank to a scuba shop and get it 'hydroed' and visually inspected, they'll stamp the steel with the new hydro date and put a fill sticker on there good for a year until your next visual inspection and you'll be good to go!

[crolison]

Originally Posted by taikowaza

I'm a scuba instructor and you've got to be careful with those old scuba tanks. There is a date stamped on the tank itself, that is a hydrostatic test date, if it's over 5 years it's not considered safe for a fill.
I heard a tank blow (luckily no one was in the compressor room when it happened)...
it left a very large chunk out of the wall heheheh
but all joking aside take that tank to a scuba shop and get it 'hydroed' and visually inspected, they'll stamp the steel with the new hydro date and put a fill sticker on there good for a year until your next visual inspection and you'll be good to go!

ditto, you don't wanna mess with a big flying hunk of metal in your truck.

[ETRNL]

kinda off topic but would a full Scuba (3000psi) be safe to drive from 4500ft to sea level mounted in a vehicle?
mine is for on board air as well but i use an adapter for a paintball tank to a 48ci (regulated to 800psi)tank to an external regulator set at 100 psi to standard yellow coil airhose to fill tires

[crolison]

Originally Posted by ETRNL

kinda off topic but would a full Scuba (3000psi) be safe to drive from 4500ft to sea level mounted in a vehicle?
mine is for on board air as well but i use an adapter for a paintball tank to a 48ci (regulated to 800psi)tank to an external regulator set at 100 psi to standard yellow coil airhose to fill tires

Yes, 3000psi in a tank is still 3000psi wherever you go, since it's its own atmosphere, and is not affected by the outside pressure (unless its a crap load of pressure or vacuum).

[taikowaza]

Originally Posted by crolison

Yes, 3000psi in a tank is still 3000psi wherever you go, since it's its own atmosphere, and is not affected by the outside pressure (unless its a crap load of pressure or vacuum).

yes this is correct, the pressure in the tank will be almost identical but the change comes in when ambient pressure kicks in, IE when you start breathing or using the air...for example if you are very deep underwater you will burn through your 3000psi much quicker because the air is denser (more molecules of oxygen/nitrogen in each breath)...so that's why you have to worry about oxygen toxicity and nitrogen narcosis the deeper you go.
so when you are high up in the mountains, there are other things to worry about with your tank and your body...for example, there will be a lot less oxygen in each breath as the molecules will be dispersed, so the higher you go, the less O2 is getting to your brain. That's why those Everest climbers need O2canisters to stay focused etc.
as far as wheeling at the ranges you're talking about this shouldn't be an issue at all, but if you ever plan on diving with that tank be careful not to drive up high into the mountains right after scubadiving, this is just like being in a plane and if you drive up too high soon after diving you will get bent

[4Crawler]

I think there may be some NPT fittings on a Scuba tank. I once did an air up system for a guy that works at a resort where they use those tanks and he wanted to be able to air up his tires from the high pressure tank. He sent me a 1/4" NPT fitting quick disconnect fitting that fit the Scuba regulator and I integrated that into the air hose:
- http://www.4crawler.com/4x4/ForSale/4air.shtml

Another option is a used pressurized water fire extinguisher. They are rated for 200 psi and made of stainless steel. They do have one 1/8" NPT fitting, but I drill and tap the head for 3/8" and 1/4" NPT fittings:
- http://www.4crawler.com/4x4/CheapTri....shtml#Storage

[Matt16]

I'm going my a semi wrecker to look at air brake tanks today.

Given my situation described above, do I even need a tank?

The way I see it, a scuba tank rated to 4000psi isn't even going to notice 120 psi, even if it expired. If you disagree, please explain.

[Matt16]

Bought an air brake tank. Has the pressure release valve, the mounting bracket etc, as well as 5 NPT tapped ports. I'm pretty happy with it.