Oil burning furnace build thread

So I'm gonna document my build here, I have bought most of the materials but I'm still open to suggestions as I go. Starting point is a 55gallon drum form, I used hefty Harriet as a reference for the dimensions and scale of the thing. Originally the interiors height was going to be 13.5" y'all, a 9" brick with a half brick on top, but at the last minute I got a better deal on 12x12 3200f bricks so I'm still adjusting the dimensions based on that. More details later when I'm at a PC but here's a sketch

 

what size crucible are you using ??? some of your measurements seem ... "odd" is it really a 9,5 inch ID? that will force you to use a pretty small crucible in an oil furnace oil furnaces need some room for combustion


V/r HT1

 

Following with interest...
What are you using for starting barrel dimensions?

 

The design started out based around what I have lying around for scrap, and I was going to use an old expansion tank as an inner form to pour the refractory against, before I decided to go with fire brick lining, but that set my expectations for dimensions. Then I thought I might use the expansion tank as a crucible for large awkward aluminum melts, but I've slowly abandoned that plan as well, a large crucible just isn't all that expensive. The height is again based around convenient use of bricks, but since 12" feels too short I'm stacking a second row of brick cut into 4, so hopeful 14.75 inside.
The barrel is about 22" diameter, then I want 3 or 4 inches of ceramic wool insulation, lines with the 12 bricks cut in half and arranged as shown. The plan is 7 full width and a single oddball one, but the actual dimensions is still in flux. 8 half width bricks sounds nice but it means I'll have less insulation and it will be an absurdly large furnace for smaller melts, but I don't know if I care about that. 9.5 does feel like a typo, that may be an older version of the dwg, I'll go check latest and greatest

 

Oh after going all over the place on size, my thoughts are to make sure the furnace can handle a #55 crucible, which o see listed as 9.5x12.25, which is much larger than any casting project i can currently imagine, but since a #30 is still 9.25 OD, why not build in the room to grow, rather than try to build a bigger furnace later.
That said I'm thinking I'll make it as tight as practical on a theoretical #55 to maximize insulation since I still think a #20 is a very reasonable crucible.

 

Ok my image ghost is all locked up so here's a .... Screen shot
basically the dimensions end out making the bricks be about 11" diam at the tightest points, which is what you see in cross sectiond there.
The pink is the insulation so you see the the bricks will compress it a bit in the corners.
I'm still tempted though to make the 8th tile smaller and make it tighter still to help keep that insulation alive. I figure a nice big thick insulation wall will make it easier to let the melt come down to the perfect pour temperature in a slow controlled way and maybe even help with fuel consumption, but since the final goal is a waste oil burner, I'm not very worried about fuel consumption rates. The first few burns will likely be done with diesel or heating oil, but ultimately I'll be cleaning and running motor oil thru it.

 

Luckygen has some dimensions of his oil fired iron melting furnace which is what I'll be using next time round. Oil is much slower to burn compared to gas as it has to vaporize and go from liquid to gas first so having a large air gap between the crucible and the furnace wall will ensure the burning oil spends more time beside the crucible. I have a one inch air gap between the AX25 crucible and the furnace wall so Luckygen's furnace has over twice the air gap surface area around the crucible lip and he melts iron easily where I can barely reach 1350 degrees C with my furnace.

 

Castaway, Mark's suggestion above is a good one.

You might save yourself much wasted effort and grief by spending some time going through the"Furnaces and Their Construction" subforum. Much has been written there on the subject of iron-melting oil furnaces. And the larger section on Foundry Construction contains a lot of hard-won information on all aspects of making an effective and durable melting setup.

In short, 3200 deg brick might or might not last through a few iron melts depending on their quality. Your furnace interior is way too small for good performance. You need to figure out dimensions of the furnace, insulation, plinth materials and design, lid design, lifting and pouring equipmant, and burner design as an integrated whole. One aspect affects the other. I'd suggest copying a good design and later improving it based on your experience in using it.

Denis

 

I watched the video a couple times. His outer metal shell (in the comments as from a water heater) seems to be about 540mm/21+1/4" diameter (350+95+95mm) which would be just a little smaller than a 55 gallon barrel. Here is what I got, if it is incorrect I can fix it. I suppose if I worked the math a bit more I'd come up with the height on the collars underneath the crucible. Does it appear that his tuyere is just above the floor?

 

Start here with my most recent build, it will get you pretty good measurements for what you are trying,
and alot of build hints and warnings

http://forums.thehomefoundry.org/index.php?threads/ht1s-insane-overpowered-new-furnace-build.1938/

V/r HT1

P.S. my furnace would definitely melt cast Fe in an A20 with no issues

 

oh i didn't realize you just threw that sheet togeher right now, thanks thats a useful ref. I'm not sure I understand the comment about my furnace being too small melterskelter. are you saying there is not enough clearance to the sidewall with a #55 crucible in there? like i said I want it to be possible to use a 55, but I'm designing more with the 20 in mind, which has 2.75" total clearance, or 1.35" clearance per side. with the 55 that tightens up to only 1.5" clearance, or .75" per side, which it sounds like might be too tight for good performance with oil, but would work with propane. that is fine by me, assuming it works WELL with a #20. unfortunately some sources will say that "1" clearance is ideal" but never specify if that means a 10" crucible in a 11" bore, or a 12" bore. other sources clearly vary opinions on the topic, so i try to take everything with a grain of salt. one nice thing about teh tall burner design is that i can have a tall plinth to keep the "smaller" crucibles in the hottest part of the furnace, with complete combustion around and slightly under them, and then run a more typical sized plinth when i go up to larger size crucibles, possibly with a penalty but time will tell.
these sources are great and will definitly save me headache in the future, absorbing as much as I can and moving forwards.

also the 3200 is not hot enough? i thought that was the highest generally available grade of most refractory. will i need to skim coat it later with something beefier?

 

No wukkas. I wrote them down on a piece of scratch paper once and probably used it as a coaster for cup of coffee and now it's in the bin somewhere. Now that it is on the computer I'll have it for a couple years and it's here too. Found out that a person who recycles 55 gallon drums is a couple miles up the road from me so let the scheming begin...

 

Maybe read through some of the furnace build threads as all of this has been previously discussed.

Here is a thread that contains my thoughts on the "ideal" iron furnace. I have 21 melts on my recent build and it is holding up very well needing only tiny tweaks.
http://forums.thehomefoundry.org/in...ry-wool-furnace-build-14-dia-bore.1122/page-3

Refractory temperature ratings must be done in simple air environments like those found in resistive furnaces or kilns. But, the interior of an oil-burning furnace tuned to maximum temperature must be a wild place chemically as there is a complex soup of hot fuel combining with hot oxygen making who knows what ions and radicals etc swirling around at a fairly high velocity scraping at the surface of the hot face.

I think it was Kelly who pointed out that refractory durability is inversely related to density. I have found that to be true. If you look in the old threads you will see that I once made a lid with refractory brick. Lids take much less beating than the side walls being directly impinged by flame. My lid took constant maintenance and I was always worried it might burn completely through mid melt. On the other hand, my Blu Ram lid and side walls have been very durable.

And refractory bricks that I have bought have varied widely in their density and in their durability. But none of them have been as good as Kast-o-lite which has not been as durable as denser refractories which have not been as good as phos-bonded Blu Ram refractory.

Melting iron with oil is very demanding for furnaces. There is no comparison to the wear induced in aluminum melts in a resistive furnace to iron melts burning fuel. And getting a fuel furnace tuned to burn hot enough to melt iron efficiently is not trivial.

Denis

 

Fantastic information there, thank you very much. I wish I knew better what exactly I wanted to use the furnace for, but I really don't. That would make design easier. That said aluminum and copper casting is most likely going to be there big use for this due to materials I have on hand, but I must have the option of iron from time to time. Looking at your build I'm almost definitely going to cut down to 3 inches of insulation since it seems 2 was almost enough and 3 works well. This will open up a bit more space inside to improve clearances.
That's a good point about temp ratings, and I saw at least one mfr say that the temp is not the operating temp but rather the temp at which damage starts, so that clarifies a bit. Kinda like working with tantalum capacitors!

 

Oh and a search didn't turn up anything, but does anyone here have any experience with versaflo 70 plus? It's what the local shop I found is suggesting for castable to make the floor and lid to seal up the fibers

 

You may need to contact Harbison-Walker and see if they will help you out. 70% alumina is very refractive, but I don't know how much abuse it will take.
VERSAFLOW® 70 QS PLUS - HarbisonWalker International (thinkhwi.com)

 

Here is what my supplier recommended (KS-4) for the hot faces and some of their other choices, also aligns for temp range and $ to $$$. We did not specifically discuss 'ferrous' so they may assumed I am doing bronze or aluminum and wanted the lowest cost option. We did talk about a chopped 55 gallon barrel unit size and ceramic fiber blanket. They also were leaning towards firebricks as the base.

KS-4® Plus – 2500°F Max (dense)
SUPER HYBOND® PLUS 2800F Max (plastic)
Mizzou® Castable Plus – 3000°F Max (dense)
KAST-O-LITE® 30 LI Plus (insulating 3000°F)<-would I need a wash coating?
PLASTECH® 70P (plastic, 3100°F, phosphate)

Castaway, are you getting excited about putting your furnace together?

Still scheming on my end...should a person stop the 'floor' hot face short of the barrel so the Kaowool can insulate that portion? Seems like the 'ceiling' would need to go to the barrel and rest on something. Also considering the hemisphere interior option for the lid.

 

Oh shoot I'm dumb and forgot to account for lining the bore in the lid, thanks for that image to remind me! Was going to use a metal form to hold the space while working, but didn't actually have a plan for after! Doh!

I cut the drum to height partially to make it easier to move around inside (soon we'll get snow and I'll need to do most of the build in the basement) and to see how well my little jig worked and gotta say I was impressed. Cut it tall so I can cut it down if I want, but I don't think I will end out doing that.

 

Looking at the MSDS for those USA available refractories show a lot of them are mullite clay and alumina mixes whereas the the 1650 degree C products available in Australia (and probably the UK) are similar to Portland cement although about three times the strength of normal cement. https://cementplantsupplier.com/cement-manufacturing/what-is-refractory-cement/

Maxicast 16LCCF is what I've been using up to date.


I'll also re-post the brochure for the Morgan (UK) furnaces with their dimensions and fuel consumption which are alumina firebrick construction: https://www.moltenmetalproducts.com/our-products/furnace/MMP-Lift-Out-Furnace-Gas-Oil.pdf