The Home Machinist!

Ahah! Air boosted spray. Most oil burners are sensative to fuel pressure and have screens and fine nozzles, making them unsuitable for waste lube oils and such. Too much junk. Filtering a 1/2 barrel of lube oil cost me 5 50 microm filters in a hurry, so I abandoned the project just then. I had created an air blown nozzle, where an air oriface blew across a spoon, and sucked the fuel into a sheet and out the end in a course spray. But could not get a clear flame, and it popped and snorted with gouts of black sooty smoke. NEXT! The burner gun is under the snow for a coupla years now, I gotta go look. its outta a 100 K furnace I think, just the gun unit.

I made a filter head to take a regular ph8a car oil filter to put in the pressure line for the furnace. We change it every month and it seems to work good. The heater in the control block next to the burner heats to about 130. The oil is warm on your hand but not exceswsively hot. Vegetable oils need to be heated to at least 275 f, 300 is better. The biodiesel guys are buying that up so the price is prohibitive.
For our unit, the fan control slots are supposed to be open 1/2 inch. That is for a furnace flame, a bit yellow and 'brushy'
For a hotter longer flame, more oil pressure and more air pressure for the injector nozzel. I've played a bit with this one. 25 psi air and 10 psi oil is a big yellow-white flame. It would make the back deflector turn red in the bright light in about 2 minutes.

Hey, All, newbie here

I am in the process of building a furnace with the intent of casting lower temp metals (alum, brass, bronze, copper). the outer shell is a 30-ish gallon water system pressure tank. In the process of finding a 'mold' to use for the inner diameter, I stumbled on a 12-ish gallon pressure tank that, when centered in the larger tank, gave me a nice 2-1/2" thick space all around to fill with refractory mortar. Done.

Then, the light went off - I haven't seen a single steel-lined furnace in all my searches & youtube video watching. Have I caused myself a problem ?

This discussion is the closest I have found to discussing the topic, and while it doesn't seem to address it critically (other than cost), I would like to hear the opinion of more experienced smelters............... Will this likely cause me issues ?

I have some experience in smelting, with more in melting. My experience does not come from foundry work, although that makes no difference. What is important is for you to understand what the terms mean, and they are not one and the same, although similar in nature.

Smelting is the process of extracting elements from ores by melting and fluxing. Melting is the process of melting already extracted elements. I suspect that what you intend to do is melt, not smelt. It is uncommon for foundry folks to smelt.

That said, it is not a good idea to have a metal lining in the chamber. It isn't stable, and will oxidize in use. That has the potential to contaminate your heats, which is never a good idea. Beyond that, when you fire the furnace for the first time, the lining is likely to expand far greater than the refractory, which is generally reasonably stable. That will (or can) lead to fractures in the furnace.

All in all, you'd have been far better served to have used a form that could be removed after the lining was in place. That kind of form can be made from wood, where multiple pieces are glued up, then turned after the fact. Sealing the turned surfaces is a good idea, which you can accomplish with a spray can. Once painted and dried, it would then be coated with a very thin film of grease, which would act as a release, so it wouldn't stick to the refractory. To aid in removal, I've even resorted to installing a small hole in the bottom, so an air hose can be used to remove the form. That works quite nicely.

You likely understand that the form should be gently tapered, so the top is larger than the bottom. I usually do that by offsetting the compound on my lathe so it generates a modest taper. Without the taper, you may experience difficulty removing the form.

Do not attempt to pour without greasing the form. Depending on the paint used, it may bond to the refractory. That results in burning out the form. Don't ask how I know.

You may be able to bail out on this situation. The contraction of the lining can work in your favor, assuming you can get ahold of it by some means. Adding some dry ice to the chamber may shrink the existing form enough so it can be extracted. It the top is smaller than the bottom, though, I suspect that it won't work.

Hope some of this helps.

H

Edit:
Welcome to the board.

As I read it, you have poured the refractory, and you have the inner form in place, which is thin sheet steel, and you need to remove it.

Consider using an angle grinder with the thin metal cutting disks to make multiple slices in the steel liner. If you do slightly too deep and cut into the 2 1/2" of refractory, probably not a big deal. Once segmented, the steel strips should be relatively easy to remove.

I would assume a crucible, of approprate size, will be used hold the metal, then I would stay away from any other lining only a compacted high temperature refractory lining is needed.

I have McEngevan (https://mifco.com) Natural Gas B30 and B60 furnaces, I broke out the old cracked and worn linings, and recast a new lining in both.

For the inside form, I got hold of two cardboard tubes, used for cast concrete in a round form.

When the refractory had hardened, the cardboard was easily removed.

I also have an electric kiln that has commercial fire brick on the walls, never lit it off yet.

Also have a Kerr Electromelt furnace, that uses a carbon crucible to melt metal, the lining is some very light material, and so far after many melts still is in good condition.