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Converting a Propane Tank to a Air Tank?
Irony - 26/8/10 at 08:02 AM

I need a portable air tank for my Electromagic Static Thingy and I thought a Propane tank from my works forklift may be the option.

We use the orange propane tanks with a screw fitting on the top. I would need to fill the tank up at work and then bring it home to use with the Electro Kit. It would regulator to bring the pressure right down.

Does anyone know what fittings I would need to achieve this?

wilkingj - 26/8/10 at 08:25 AM

More importantly than the fittings sizes... Is whats the safety pressure rating on the tank?

Namely what pressure are you going to use it at, and is it within the safety limits of the tank.
You dont want it to turn into a bomb and injure yourself or anyone else... let alone get killed!

Just be very careful and very sure of the technicalites of the pressures etc before you do this!
I am no expert at all, but urge you to be very cautious and do your homework before deciding to go ahead.

Ben_Copeland - 26/8/10 at 08:36 AM

http://wolfstone.halloweenhost.com/HalloweenTech/pnupro_PropaneAirTank.html

This website reckons propane tanks are rated to 250psi so 100psi should be fine.

Still worth investigating more tho

MK9R - 26/8/10 at 08:37 AM

i'm sure propane tanks are a lot lower pressure than compressed air tanks. How about a 2nd hand divers tank? i assume you have a compressor to fill it at work, so you dont even need to get one with a current test certificate

MK9R - 26/8/10 at 08:39 AM

http://cgi.ebay.co.uk/Faber-12-litre-scuba-air-cylinder-/220658444870?pt=UK_SportingGoods_Scuba_SnorkellingEquipment_SM

MK9R - 26/8/10 at 08:40 AM

quote:
Originally posted by Ben_Copeland
http://wolfstone.halloweenhost.com/HalloweenTech/pnupro_PropaneAirTank.html

This website reckons propane tanks are rated to 250psi so 100psi should be fine.

Still worth investigating more tho


i stand corrected

chrsgrain - 26/8/10 at 09:07 AM

quote:
you dont even need to get one with a current test certificate


The whole point of an inspection certificate is to make sure it isn't about to explode when you fill it!

Chris

liam.mccaffrey - 26/8/10 at 09:16 AM

when I was in the states. you used to be able to buy air reciever tanks from walmart. They were pretty large too and only $18 iirc, which I thought was a steal. They were rated to 110 PSI has a pressure gauge and cam with a bunch of fittings and a tyre filling hootus.

The idea was to fill them and keep in the car for tyre inflation.

I knew at the time they were a steal and I wish i had bought a few

Bluemoon - 26/8/10 at 09:17 AM

quote:
Originally posted by MK9R
quote:
Originally posted by Ben_Copeland
http://wolfstone.halloweenhost.com/HalloweenTech/pnupro_PropaneAirTank.html

This website reckons propane tanks are rated to 250psi so 100psi should be fine.

Still worth investigating more tho


i stand corrected


I would not do it, or at least I would think very carefully about it. Propane is "normally" at a lower pressure (I think) and that's a US site, you would need to find the colar gas bottle specs, or what ever you are going to choose.

You might find that you will be working in the "saftey" factor region all of the time for the bottle? Not sure of the vapor pressure over-liquid propane or how it changes with temperature...

Dan



[Edited on 26/8/10 by Bluemoon]

Irony - 26/8/10 at 10:06 AM

The tanks we have are STACKO by manufacture and their website says there design tested to 3000kPa. Which I have converted using a conversion website to 30 bar. So I think six or seven bar will be fine.

Does anyone no what sort a fitments I would need to make this work?

off-road-ham - 26/8/10 at 10:37 AM

Hi, I would advise looking for a faulty compressor, one where the motor or pump have failed.
If you do use a propain tank you will need to remove the valve assembly and "Clean" it out.
This is an involved process because there is a buildup of residue on the inside of the tank.
I belive the valves are a left-hand thred into the top and containe an inner valve to stop the pressure droping to 0 (although I could be wrong on this.)

I do have plans somewhere to do this from a build your own compressor article using a car aircon pump.

personaly I would find a faulty compressor for its tank.

Also you need to make sure the air coming out is clean if you are using it for powdercoating.

[Edited on 26/8/10 by off-road-ham]

paulf - 26/8/10 at 11:06 AM

Propane tanks are tested to at least 24 bar, i had one from a gas conversion removed from a transit van and used it as a receiver for my compressor for years at 120psi until one day i moved it and realized it was full of water and going rusty.
The main problem to overcome is that the valve has a left hand thread although it would be possible to dismantle a regulator to obtain the fitting then adapt this to a 1/2 inch ball valve with a tee piece and air regulator to fill it and connect up to spray guns etc.
I think I have seen receivers fitted with a ball valve for this purpose in the tool station catalog, although one of the cheap Aldi type compressors would be a better bet for about £60.
Paul

Irony - 26/8/10 at 11:39 AM

It looks like a cheap cheap compressor is going to be a better option then really. All the safety issues plus sorting the valves plus lugging it about to be refilled. £60 on a Aldi one then......

procomp - 26/8/10 at 11:48 AM

Hi

What size tank is required. Dive bottles any use. Used to use them as quick fill easily portable for tyres. If tested the local dive shop would fill them FOC.

Cheers Matt

londonsean69 - 26/8/10 at 12:01 PM

quote:
Originally posted by procomp
Hi

What size tank is required. Dive bottles any use. Used to use them as quick fill easily portable for tyres. If tested the local dive shop would fill them FOC.

Cheers Matt


You need to take a look at pressure and volume.

A standard (UK) dive bottle is 12l at 232 bar. Thats 2784 litres of gas.
You would then need a regulator to bring it down to somewhere between 7 and 10 bar. Most SCUBA first stages drop it to around 10-11 bar, so you could probably rig something using one of those (I have a tyre inflator that connects to a BCD hose).

By far and away the most common neck thread on a UK dive tank is M25, with a few old ones still kicking around (3/4" BSP). The valve will either be a yoke (clamp on reg) or a DIN (5/8ths), although some are rigged for airgun charging

The testing cycle on a dive cylinder is for a visual every 2.5 years, and a hydro every 5 years. The requirement for a visual is dropped for surface use only tanks (air guns etc.) as they probably won't have the chance to get a good gob of water in there.

As for free air - doubtful. Generally around £3-£5 for a fill near me, but I just happen to have a 300bar breathing air compressor.
A hydro test last time I had one (last week in fact) was £29.50 including valve service. The shop is use is excellent, and cheap. Some others charge £40.

Dive Compressors aren't cheap, so the shop will want to recoup the outlay. there are a couple of places that do free air, they are hoping you will spend some money in the shop whist waiting for your fill, but they are few and far between.
Part of the cost is down to the need to have the air tested for purity every few months, not a requirement for the typical (low pressure) garage compressor.

[Edited on 26/8/10 by londonsean69]

Theshed - 26/8/10 at 12:04 PM

I have a snap-on 150l air receiver that is free to a good home - collect from london

Dale - 26/8/10 at 05:15 PM

I have made a 30 lb propane tank into an air pig( portable tank) 8 years ago with no issues and have an automotive 40 lb tank on a complressor that has been in use for years.
was easy conversion The automotive ones are massivly over built and free to pick up sometimes--mine was.
Dale

dazzx10r - 26/8/10 at 06:14 PM

My compressor tank is an old 35kg propane tank, been using it for years and it's been fine. The compressor knocks off at 120psi, you could pick up a 7kg (smaller size to your fork lift truck one) either propane or butane, the local tip usually have a fair selection of them.

kenton - 26/8/10 at 08:25 PM

I have one that is used if one of the farm vehicles gets a puncture. Its an old forklift truck size, threads are 3/4"bsp.
I put a T in the top, one side has a valve and an airline fitting to connect to the workshop airline, the other side has a connector for tyre inflater.
I fill up the tank (120 psi) close valve, transport to vehicle with puncture and inflate. The tank contains enough air (usually) to return to farm.
Hope this makes sense.