Aluminium Casting Foundry

Making a foundry for melting aluminium (Aluminum for the US) out of a 13kg propane gas bottle

why am I making an instructable that many people have already done? well I thought it was an amazing Idea but I feel there was some room for better documentation, and a few little changes such as a lifting mechanism for the lid and no fire cement for the refractory.

Step 1: What you need

SAFETY NOTE: messing about with gas bottles or pressurized containers is very dangerous, do this at your own risk, but if you do decide to do it be safe, use your head, think about everything you do before you attempt to do anything. I have put in some tips as to what I have done in each step.


What you will need for this project

13kg gas bottle (UK), I got mine from freecycle.org from someone who didn't need it any more, in the US they are 12.4kg

Bag of sand

Fire clay

1.5 inch screws

a short length of steel pipe

nuts and bolts

a short length of hose

Charcoal

cotton wool


tools
----------

Angle Grinder with cutting discs and grinding discs

A file

Cordless drill and wire brush attachment

Arc Welder with 6013 rods (we find these rods easier to start and use with less sticking)

an outside tap

gas regulator if you're in the UK or you gas bottle doesn't have a tap

a steel rod if your gas bottle doesn't have a tap or you don't have a regulator

brush

rags for cleaning

marker pen

extension lead for working outside

hammer


------------------------

some extra info on the gas bottles in the UK can be found here including their dimensions.

http://www.calor.co.uk/customer-services/faqs/general-cylinder-queries/

the bottle I'm using has the following dimensions

Propane: 13kg Patio Gas 580mm 315mm

Comments

[blenz]

It is pretty funny reading all of the posts talking about how dangerous this all is. A couple of years ago the city had to change the supply tap from the main gas line to my house. Anything with these lines has to be welded, but they don't shut down the gas main. They drilled a hole into the main and lit it on fire until he was ready to weld in the new tap! For the old supply tap he did the same after he hammered in a steel plug! the entire time he was welding a 2 foot tall jet of flame was searing the cold February air. When it was all done he checked for leaks, you guessed it by playing his lit welding torch over all of the repair areas. So lets just all agree that "dangerous" is a relative term :)

[firesirt]

If you think about it, you need oxygen for propane to burn, so it really isn't dangerous until it is well mixed with air.

[AJMansfield]

The only real risk is that the additional heat from welding the tank could cause the tank to rupture (from increased pressure), and spill out gas fast enough for the flame jet to travel far enough from the container to damage stuff (like yourself). Generally, its really only dangerous if the burst of flame is unexpected.

[n1cod3mus]

that couldnt happen as I drilled 2 holes in the top and emptied the gas out of it, by the time I came to welding it the top had been cut off.

the only time it would be an issue if the gas bottle was still sealed and i then started to heat it, your then looking as a pressure vessel which is dangerous, it would basically be a time bomb.

[murban1]

Here in the USA if you go to your local propane suppler and ask for a bottle that is no longer certifiable and tell them it is for a special project often they will often give it to you for nothing. Saves them the cost of having to dispose it.

[Bald2]

In the past I have had to repair by brazing the odd car gas tank. I think this dangerous operation can be made a lot safer by dropping a few chucks of dry-ice in the tank and leave one vent hole opened and let the CO2 purge bit before you start. With that in place my hand doesn't shake nearly as bad with the torch.

[n1cod3mus]

dry Ice is harder to come by in the UK

[blenz]

Really!? Why have they made it hard to find? (No criticism just plain curiosity :)

[n1cod3mus]

its not avaliable in supermarkets here, it would take a while to source it

[blenz]

I'm sorry to hear that, If I could I would ship you a whole carton of the stuff! Thanks for the 'ible by the way I hope I get a chance to try it this winter.

[WareShoals]

Great instructable. For those of you looking for fire clay check out ebay: http://www.ebay.com/itm/Super-32-Refractory-Mortar-50-pound-container-/130470068688?pt=LH_DefaultDomain_0&hash=item1e609f41d0
I found some at the above address. WS

[Nirgal38]

Wonderfully detailed and well documented from beginning to end. That's the way all 'ibles should be.

Sadly, I lack the tools to build one myself but that doesn't mean I don't want one.

Incidentally, does anyone know where to easily find fire clay in the US? It doesn't seem to be an item carried by your average home improvement store (unless they have it listed under another name). I once built a forge from an old cast iron sink and have been interested in doing it again.

[botnot]

Hi,
Look in Ceramics Monthly old editions (college library) for recipes. It is easy to make. Also refractory suppliers and ceramics stores will have it in stock. Not the low fire or 'artsy' stores, but a store that supplies clays and raw materials in bulk. look online or in the Yellow pages where you live.
Good luck,
Botnot
ps
(at random)
http://www.backyardmetalcasting.com/refractories.html
http://en.wikipedia.org/wiki/Fire_clay
http://www.artistpotters.com/anagama/castable.htm
http://www.traditionaloven.com/wwwboard/messages/3189.html

[botnot]

If unable to find fireclay, you can use Aluminum Oxide, [alumina]. It’s works really well. Sand blasting companies use Alumina and sometimes throw it away.

By the way, fire slowly at first. We 'candle', (very soft and low flame, sometimes overnight), until all of the H2O has dried out. Raid conversion to steam can burst off sections of the refractory, cause cracks, etc!!. We always fire slowly and progressively at first. The denser the castable, the slower we fire it. Most castables have the instructions on the package. Google is your friend!
Forgot to post that,
Thanks,
Botnot

[n1cod3mus]

you could try pottery of ceramic suppliers, I got mine on ebay but im in the UK, if anyone else is in the UK clayman supplies do fireclay sometimes

[weldor]

Call a furnace or a boiler repair company. You may also find it at a local ceramics supply store.

[Kiwi 2]

Very well written and you have made a good job of the little furnace.

I was very concerned though to read the description of how you began the modification of the gas cylinder. I am a former welding instructor having trained many apprentices and tradesmen over a number of years in NZ. I want to advise all instructable readers never to attempt to follow the same process to cut into a gas cylinder. Any attempt to modify an old cylinder in any way runs the risk of serious injury or death. I cannot stress this enough. There have been several incidents world wide where cylinders have exploded.

There is a much safer alternative for furnace bodies. I have made a number of successful furnaces and forges using the internal casing of old water heaters. These are about the same diameter of gas cylinders and are made from 3mm thick steel which can be cut very easily and completely safely using a cutting disc in an angle grinder. I have attached some photos.

Once again, a great instructable Chris but my advice is to never use old gas cylinders. You were very lucky.

[botnot]

Nice work! I spent a long time building offhand glassblowing equipment. 'Sometimes' the layer of glass on the inside of water heater casings can vitrify at higher temps and begin to degrade the castable lining from the back. INot to say that it will cause cause problems, but it can.
Great project, and thanks for sharing to all,
Notbot

[n1cod3mus]

the gas bottle was empty, with no pressure, I drilled 2 holes using a battery operated drill, I would have used a manual hand drill if I had one, I did this slowly, then filled it with water to get rid of the gas which worked. no big bang.

I have to agree though if i could have got hold of an old boiler this would have been safer, but i was working with what I had.

[AJMansfield]

Which is almost EXACTLY the procedure used for industrial construction that is used before welding a tank like that. The only real difference is that they would leave the tank's walls intact, and use the tanks own valves instead.

[n1cod3mus]

the valves on the UK tanks are one way and you need a regulator to use them, unlike the US tanks which seem to come with a tap attached.

I have to admit I was crapping my self while i drilled it but I made sure the valve was depressed while i was drilling so i know there wasnt any pressure and i used the drill really really slowly to try and prevent sparks, i guess you could also run water over the area being drilled to prevent sparks.

[Thoth]

Couldn't you have used a wrench (spanner in the UK) just to remove the entire valve assembly, which would have made emptying out the gas much easier and safer?

Even running the drill slow there is a risk of explosion because the drill motor is constantly sparking.

[n1cod3mus]

I wanted to do this but on one side is a safty valve which got in the way, and the other side was a level gauge which was in the way. but to get it out you have to melt the liquid weld they use on the valves and this is best done with heat, not a good idea with a gas bottle

[weldor]

They are instaled with some sort of a locking sealer. I use my recipricating saw to cut off the valve. If you are concerned about the spark/gas thing turn a garden hose on the saw blade to basically seal the cut and you should be fine.

[loopingz]

I would be scared a this point, because on very low gas just some air inside would make some good explosion ratio...

[weldor]

for ignition of lpg or propane type fuels you need somewhere in the vicinity of a 14to1 air fuel ratio. That is where the water comes in. As I said before, it seals the air out and keeps what little trace gas is left in the bottle in the bottle. I ALWAYS bleed the bottle to zero psi and let it sit with the drain/bleed plug opend or removed over night before I ever start cutting.

If the afr is not correct there is little if any chance of an explosion.
If you had an air powered saw you could always cut it completely underwater.:)

[n1cod3mus]

the most likely out come would be a jet flame until the air got enough inside the bottle to ignite and then it would eat up the oxygen and just raw out of the holes like a jet engine. if anyone has seen those jam jar jet engines its the same just a lot scarier lol.

[bg_askins]

i take my empty tanks to the local propane company and have them purged with argon for $5

[n1cod3mus]

good advice

[radarguy]

This is SUPER SUPER DANGEROUS! Please recommend against this. Unless you can remove the valve and flush the remaining gas out before grinding you have a potential bomb!

[n1cod3mus]

which is what I did, flushed it out with water

[thisisradionick]

I have been working on a foundry with some people. http://www.hammerspacehobby.com/2012/05/flower-pot-foundry-test-run.html

We had a lot of problems with crucibles burning out the bottom. On the third try we used a small oxygen tank that we cut the top off of and it worked great.

[n1cod3mus]

i'm in the process of writing an instructable on making your own ceramic crucibles, sort of following Vince Gingerys method in his book, but my own way as i dont have a wood lathe yet.

[tatagatha]

I made a charcoal furnace last summer. I had a really hard time keeping the temperature consistent. Have you had issues with it swinging wildly? Maybe my refractory was poor. I've made an electric one this summer, but havent fired it up yet... yet! I'm hoping it will be more consistent and the electric radiant heat to be gentler on the crucible. Also, if you are first making ignots from known alloys, check out this little tip:

http://castboolits.gunloads.com/showthread.php?t=79594

[n1cod3mus]

havnt had an issue, but then I have no method of measuring the temp, but it melts the aluminium and keeps it molten

[loafers]

Bloody good job mate, brilliant instructible with with both a great outcome and documentation. You even used the better spelling of Aluminium haha, the word Aluminum urks me for some reason (not meaning to offend the American English speaking population, ours probably urks you guys). I reckon I should give that a go, a real ripper that is.
(p.s. I'm not British, I'm Australian)

[pedalmonkey]

Don't feel bad that you haven't gotten many hits yet. Give it some time. There have been a few other furnaces on here that were similar but this is probably the best I've yet seen . Good job on the ible!

[n1cod3mus]

thanks for the compliment

[heathbar64]

Nicely done! plenty of details as if you really expected us to build one from your ible. I've always meant to cast aluminum, and maybe this will motivate me to actually do it.
It seemed like in the test pour video, that the aluminum was kinda jello-ish. I always understood it to be watery when melted. what about that?

[n1cod3mus]

also you have to bear in mind that the surface tension would be different than water, hence why it sort of domed in the pan.