SpudFiles

Hey,

I'm just after a bit of advice about connecting setting up a regulated air feed.

I currently have my fridge compressor setup and it is working perfectly. What I would like to do is connect my fridgy to a propane tank and then regulate the air out of the tank.


My compressor


i.e this setup

Now, that you hopefully understand, I want to ask about thread differences. This regulator here has "5/8”-18 UNF RH Ext" threads, while the propane tank will likely have some weird thread type aswell.
How should i go with connecting this?

I don't think a propane tank is safe at those pressures. LPG doesn't get much above like, 120psi unless the tank gets hot, as far as I know. I don't think they're rated to more than a few hundred PSI, so using one with a fridge compressor could result in some bad juju (shrapnel, etc...).

Can't help you with the threads, sorry.

Peace,
Pete Zaria.

Pete Zaria wrote:I don't think a propane tank is safe at those pressures.

Sure man, I can understand that, although i don't know where you got the idea i was going to be using extremely high pressure from.
I will only be using about 250psi in the tank. Then I will probably regulate it to 50-100psi.

propane tanks usually have a pressure relief valve if pressure get too high, so you'll be relatively safe

Matt_NZ wrote:

Pete Zaria wrote:I don't think a propane tank is safe at those pressures.

i don't know where you got the idea i was going to be using extremely high pressure from.

In the pic you posted, the gauge is reading well north of 500psi, and I know fridge compressors are capable of more.

As long as reasonable caution is used, I think your idea will work fine. You might also look into a large fire extinguisher or similar; they can take higher pressures (being designed for CO2 use).

Peace,
Pete Zaria.

Pete Zaria wrote:I don't think a propane tank is safe at those pressures. LPG doesn't get much above like, 120psi unless the tank gets hot, as far as I know.

Thing is, there's this thing called "The Sun" and as a result of it, tanks DO get hot and must be built accordingly. Vapor pressure for propane at 130 F (very doable in the summer sun) is right around 250 psi.

Pete Zaria wrote:

Matt_NZ wrote:

Pete Zaria wrote:I don't think a propane tank is safe at those pressures.

i don't know where you got the idea i was going to be using extremely high pressure from.

well north of 500psi,

It is well north of 500kpa, it is a dual psi & kpa gauge.

Peace.

Pete Zaria wrote:In the pic you posted, the gauge is reading well north of 500psi, and I know fridge compressors are capable of more.

No, his gage is reading 200 psi.... Which is "well north" of 500 kPa. More like 1300ish, actually.

D_Hall wrote:

Pete Zaria wrote:In the pic you posted, the gauge is reading well north of 500psi, and I know fridge compressors are capable of more.

No, his gage is reading 200 psi.... Which is "well north" of 500 kPa. More like 1300ish, actually.

Whoops, you're absolutely right, I didn't notice the kPa marking. Good call.

Peace,
Pete Zaria.

In the USA, the DOT propane tanks are required for the relief valve to remain closed up to 300 PSI to prevent venting and fires in hot weather.

If you remove the valve from the tank (it unscrews) the tank will accept regular pipe thread fittings. Use a proper relief valve as the safety relief on the original tank is built into the valve.

The tank on the right shows a test fit for converting a tank from 3/4 inch to 1/2 inch to 1/4 inch for air fittings. This is not screwed in tight. The threads on the US tanks are 3/4 inch pipe thread.

Technician1002 wrote:the tank will accept regular pipe thread fittings.

Since it is in the usa would this be an NPT thread?

Also I still need to find out about to find out about this UNF thread (which I'm finding on gas regulators) if I can adapt it or I'm better off looking for a air regulator with bsp threads?

I used fittings straight from the plumbing depatment. They matched the thread pitch of the valve that came out. I'm assuming they are NPT.

C11 made this same mod and it looks like he used regular plumbing reducers like I did. See his mod and photos here;
http://www.spudfiles.com/forums/my-new- ... 21218.html

Matt_NZ wrote:

Technician1002 wrote:the tank will accept regular pipe thread fittings.

Since it is in the usa would this be an NPT thread?

Also I still need to find out about to find out about this UNF thread (which I'm finding on gas regulators) if I can adapt it or I'm better off looking for a air regulator with bsp threads?

There's nothing special about UNF.

That said, most regulators will have the screw fittings coming out of the body of the regulator, but the fittings themselves are simply screwed into the body of the regulator with NPT threads. There's a very real chance that all you have to do is remove the UNF fitting and plug in a piece o' pipe.

D_Hall wrote:most regulators will have the screw fittings coming out of the body of the regulator, but the fittings themselves are simply screwed into the body of the regulator with NPT threads.

You must be right. After looking for documentation for the regulator I linked to i found it has 5/8" BSP connections on the body, this is brilliant.

Btw, what do you think of the regulator. Would it be well suited?