Oil burning furnace build thread

Added 5 inched to the internal height, gets me more lined up with the numbers Denis mentioned above.

 

Since seeing your above (nicely done) drawing, I have been looking at my lid and after 26 melts can see that the stainless sheet metal rim has been worked some by the fire. It has long been a problem for me to seal my dome lids agains the furnace body/base and protect the metal that wraps around the edge of the lid hooking under the lid segments. After a few melts the wool gasket the lid rests on tends to shrink and loose some of its resilience. And, if I am busy managing the metal, fuel, and getting molds ready I do not always replace the gasket immediately. My bad. And that strongly contributes to erosion of the metal as jets of hot gasa escape and that spells trouble.

So, I sat down this afternoon to try to design a better lid retention ring. Here is a design for the lid segments that will allow for a rim that will not itself be "in the line of fire" so to speak.




I am NOT saying this is how you should build your lid. I am just pointing out an idea that relates and might be a good idea or not. As I envisdion the above the segments would be made of Blu-Ram and woudl be about 1" thick. The rim would accomodate a metal ring-like rim band that could encircle the outer rim. To the rim metal "fingers" that would wrap around the edge as far as the lower groove. Something like this:


BTW, that yellow rim piece would be a circular hoop---one piece not segmental. The red part could be continuous or, perhaps more practically, evenly spaced 1" segments welded to the hoop.

With this arrangement refractory would be sealing against wool rather than metal against wool. The tall yellow rim piece will also backstop wool laid on top of the refractory.

Sorry, this is all preliminary. But, I think is a promising idea for my furnace and might be useful for other folks as well. I'll continue to try to flesh this out.

FWIW

Denis

 

Thanks Denis. I have been thinking about something like that too, welding on bits of metal to catch the refractory on the lid. Would you still have a contact patch between the body and lid refractory around the bore of the furnace?

 

You could design in hard-refractory-to-hard-refractory contact around the edge of the lid. But I have found hard refractories to be only semi-stable over the long term and multiple firings in my hands. I think other folks have made tight hard-hard contact and I guess it has worked out. For my use, I like to use a layer of wool as a gasket since it conforms to any irregularity and is easily replaced as needed. (I just use some Satanite to glu it down) I had become a bit complacent in that last regard as I used SS for the lid hoop on my last build. I have since found that it is definitely much more resistant to fire than common low-carbon sheet steel. But, it still has its limitations. So, I think I am going to try something along the lines sketched above. I like the idea of taking the fire contact with steel out of the equation. I really think that will be a durable solution. Even so, Blu-Ram will not last forever. I am just trying to maximize intervals between relines of the furnace and the lid.

Denis

 

Perhaps an inner band of stainless with some tabs or rounds or? Could be attached to lid with sheet metal screws provided they don't poke the hard refractory.

 

I guess those tabs you drew could work. But make sure they stay out of the fire. Monolithic refractory seems to want to crack when I have used it. It will need all the support you can give it. So, you'll want plenty of tabs. I'd err on the thicker side as fire tends to eat them given a chance.

If I am totally honest, I'd suggest that rather than using tabs on your lid that you use a continuous donut of sheet metal welded to the hoop. The donut, shown in red below, provides considerable stiffness and uninterrupted support.
Not to scale exactly.



Denis

 

Sometimes I miss the days when I could CNC plasma cut parts for home projects...That ring would have taken about 1.5 mintes and could have been done right off the controller, no need for CAD or CAM...sigh...

 

On rings like that I have gone to making a masonite template for a fifth or fourth of the ring. Then I lay out segments on maybe 4 or 5 inch wide stock and cut it out on my band saw. I mig the pcs together and finish the OD on my belt grinder. So much slower than just laying it on a torch or plasma table---true. But quite conservative of material and, with the mig, pretty fast. The part does not look too pretty, I guess. But, since it is the underside of the lid, who really cares.

Denis

 

I've used tabs on two furnace lids now with no serious leakage problems with two caveats: make the lid thick enough that some wedging can occur if a crack does happen and secondly, cast the lid in situ on top of the liner so as to get a good mating surface. The tabs could also benefit from being welded halfway up the lid band so it would be hidden in the refractory and still key the refractory to the lid while keeping it hidden from any flame leakage.

 

This is the under side of my lid. It was cut from the top of the beer keg. I cut it just at the bottom of the depression that was originally rolled into the keg and poured it. It left the inward curve that supports the refractory. Other structure features of the lid like the handle holes help as well, I’m sure, but the primary support comes from the bottom rolled lip. It think the refractory in the lid is about 2.5” thick. If the bottom edge can’t be rolled then perhaps you could split some 1/2” conduit and weld it around inside the ring high enough that it’s encased in the refractory.
Since I made the lid first I used it to level the upper portion on the furnace refractory to give me a reasonable mating face. I get some leakage, but not bad.




Pete

 

Burying the lower rim/tabs part way up in the refractrory makes a lot of sense. My own take is that the inverted cone that Pete got from his selection of keg section is even better. The idea that settling of the refractory (which I think is bound to crack) casues compression of the fragments seems like a very favorable setup. In addition, heating of the band during firings will cause the band to expand more than the refractory. So, the refractory will tend to wedge itself even further into the band and then cooling of the band will cause yet more compression of the refractory. Both good thoughts I had not previously considered.

Denis

 

Hi all,
I am in the beginnings of building a diesel fired furnace and I see on the first pic of this page you have installed a riser/plinth for an A20 crucible and I wondered why? Are you looking for the swirl to hit the crucible at a higher stance?
Mark Presly is melting aluminum in less than 10 minutes with his and its not a huge set up.



Is it possible to build this to big and waist to much fuel? I want to size this for an A20 but will most likely not use one very often as the cost of material is so expensive.
Part of my thought was to build it oversized with 2nd stage wall that would slide into the furnace to reduce the size.

 

Hi Todd,

On a liquid fueled furnace, you need more height and more space between wall and crucible for fuel and air to mix and burn.

He did see quite an improvement over his old system approaching 3-4x faster melt with aluminum, it does seem like a nice system.

My small propane unit can do A6-ish in about 20 minutes. I have not taken a stopwatch to it yet but I do know not to try to multitask mid-melt (have molds ready to go and tools and PPE at the ready).

PS My pic above was an A20 concept. I am working to finish an A10 first. I would not use either plan as-is since they are unproven as of this writing (12-24-2023)

https://forums.thehomefoundry.org/index.php?threads/resizing-55-gallon-200l-drum.2490/

 

Welcome to the forum Todd,

The plinth is to keep the flame from hitting the crucible and shortening it's life.

I hate seeing people putting a time stamp on Aluminum melts. It sucks neebies into thinking they have to match that speed and is far from the truth.
The flame he used is for melting red metals and iron (very rich).
He should have dialed the flame back into the furnace and leaned it out as soon as the Al started to slump (hot short).
With that rich flame the Al will absorb the excess hydrogen and look like baby swiss cheese.
I would rather take 15-20 minutes to get a quality melt.

 

Hi Fishbonz I completely agree with you but I work for a diesel fired hydronic heater co and find this a little adventurous I am really excited to get this up and running. There is a ton of good information on this site and I think I can get it close although I cut my top flu hole 4" and I am second guessing this.

 

The nice thing about aluminum melting is that it is very easy to accomplish with a fuel fired furnace. It is not necessary to tune your flame to the very hottest possible degree and may not even be desirable for the reasons stated above so, I would suggest just making the furnace and not worrying too much about it having the ultimate high performance. Later, you can tune it to optimize performance for making castings, as opposed to making “muffins” as fast as possible. There will be enough challenges in learning how to cut gates, runners, and make risers. Hopefully, the melting part will be the easy part.

Denis