In the process of building a keg furnace. Question I have is should I use kaowool with refractory cement on the inside? Or just use refractory? Any help is appreciated.
From personal experience the dense castable refractory needs to be 3" or thicker and will lose enough heat at that thickness to be 360C / 780F on the outside. The furnace will still run fine, it's just hot on the outside and you're losing heat faster. Dense castable is more durable for say oil fired iron melting as oil vapours can soak the kaowool.
Satanite coating kaowool works pretty well. Especially for aluminum and bronze furnaces. I think some members (Bonz?) had made it work well for iron too. In my case it broke down after 30 or so melts. But the satanite is effective at preventing oil getting into the wool. I like a thin BluRam segmented hot face with wool backing for my iron work. Reasonably durable and light weight that works well for my one-and-done style pours as opposed to repeated pours over several hours time. Denis
No experience with coated kaowool at all. There's some brochures for commercial furnaces with dense castable refractory that give a rough idea of shape and dimensions and you can see they start at half a metric tonne in weight or 1100lbs. I would imagine getting castable insulation to say 4" thick in a beer keg would limit crucible size to about an A16 at best while still having enough air gap for slower burning oil fuels to get hot enough. https://forums.thehomefoundry.org/i...cial-oil-gas-furnace-brochure.987/#post-23333
I would line the inside with 3 inches of kaowool and then an honest one inch of mizzou. This will help get the internal diameter of the keg down a bit in size. Unless you are planning on using a monster crucible, they really are a bit on the large size. Kaowool is cheap, use the entire box! I personally wouldn't coat a kegs worth of kaowool with satanite unless you need to really do this on the cheap and don't care about longevity.
It depends on fuel IMO. If you’re using propane I’d definitely recommend using koawool in the design in some fashion. Oil, especially the free variety, gives you more options particularly if you’re running multiple heats. My keg furnace does not have any insulation. I used a 10” HVAC duct for the inner form and a 12” duct for the outer form. First I rammed the floor level with mizzou. I set the 12” duct and rammed a wetted mix of sand and fire clay for the outer layer in contact with the interior of the keg wall. It’s 1.5” or so thick. I stopped about an inch from the top. I let that dry and then fired it. I then set the 10” form and rammed the mizzou hot face all the way up to the top covering the top of the exposed layer of sand/fire clay making a nice finished top surface. The furnace is quite heavy but I don’t move it so that doesn’t much matter, but it takes awhile to get that rock hot. But once it’s hot it’s hot. My first choice would have been to just use solid Castolite 30li because it’s an insulating castable but my supplier only had mizzou on hand and it was free so I went for the layered scheme with the goal of keeping the weight down. The furnace is pretty inefficient and indeed gets hot on the outside, but it melts aluminum pretty quickly on the first heat, and almost immediately on subsequent heats. I successfully melt bronze and cast iron and although first heats take awhile, second heats are very fast (comparatively). Free fuel and a well tuned burner are helpful. In hindsight if I were to build another furnace (I already have 3 so I doubt it), I would strongly consider using kaowool or at the very least be more adamant about the castolite. I kind of envy the speed and efficiency of the wool/satanite designs, but I’m gettin it done with what I have. Pete
I've only done gas fired aluminum in mine, Ironsides has a coated wool iron duty furnace though. I think the best setup would be having two furnaces. A coated wool for 'one and done' quick melts with gas. An iron duty furnace that can be abused.
I will use this furnace weekly and at times daily. Thanks for the input. Will melt silicon bronze mostly.
I will be using multiple fuels depending on availability. I just purchased some refractory. I drove and personally picked it up so it was cheaper. https://www.sheffield-pottery.com/LOUCAST-3000-CASTABLE-MORTAR-p/lvclcfs.htm
Yeah got it. I will need room for a A16 or A10. May be 2" kaowool and 2 1/2" refractory..... Decisions
These are the crucibles I use in my keg furnace linked below. 10” bore. I use the #18 for aluminum and the a10 salamanders for bronze and iron. I also have a couple of #7 budgets that I use for aluminum and bronze. The “budget” crucibles have a relatively short and sometimes catastrophic life in higher temp service and as mine get used up I’ll be going strictly to salamanders. The #18 is probably the largest I can fit in there and still get my tools in without scraping the sides. The conventional wisdom here has generally been to leave at least 2” between crucible and wall in an oil furnace for the sake of combustion (there’s still an active discussion going on here about it). But I set my crucible up within 2” of the lid to maximize the area down low in the furnace and it performs just fine melting aluminum. https://www.lmine.com/budget-graphi...2_374/18-budget-graphite-crucible-p-5735.html https://www.lmine.com/salamander-su...super-a-premium-graphite-crucible-p-4028.html This discussion brings up an interesting thought. One of the complications of a monolithic hotface wrapped with koawool begs the question: how do you set the refractory without damaging (compressing) the koawool? Myfordboy did a nice job of casting the refractory, wrapping with wool, and then fabricating the shell if my memory serves me correctly, and others have slid the assembly into a shell, but it seems like one could install the wool into the can or keg and coat with a heavy layer of satanite. Once dried or fired the satanite shell might very well hold up to the refractory being vibrated in thus protecting the wool. If moisture contacting the satanite was an issue, it could be simply lined with food wrap which would burn out during the firing process. Thoughts? Pete
Remember, when you add an insane amount of refractory, you will take longer to come up to temp. A solid inch or slightly more on the walls is PL E N T Y of mizzou. The stuff is tough as nails and really will take a beating from lifting tools, etc. Kaowool is much cheaper too, you find out real quick refractory cement never goes as far as you'd like.... Petee, I doubt it really matters that much if the kaowool gets a little beat up. A thin steel form would be helpful protecting the kaowool from the wet refractory. It could be left in there too. It won't burn up behind the hard face. Has anyone ever torn down a furnace to inspect the condition of the kaowool behind the face??? I have had the stuff catch on fire in my hand, but that's also out in the open and not in a closed off space. Wouldn't it be funny to find out after 10years on a build, the kaowool is nothing more than a pile of dust behind the face?
Mizzou is like concrete from the Gods! It is rated for 3000degrees and is hard as hell. It works best around 1 inch thickness. Back it up with Kaowool, sand/clay or cat poop. It comes in 55lb bags. You'll want to shop around as prices are stupid. I've seen unscrupulous sellers asking 14bucks for 5pounds to 170bucks a bag. Seems to me I paid around 70bucks a bag. You won't want to have it shipped in and you should be able to get it locally. Buy 2 bags. You will want to read up on using the stuff. Done right, you will not get any cracks. Just remember it is NOT CONCRETE as much as it will seem like it is to you. How you been? You turning professional youtuber on us? Remember everyone stands on the shoulders of the giants! So don't forget us big guy!
I was trying to get a YouTube video out every week but haven’t had as much time lately. But I mentioned you in my upcoming video. Remember when you told me to use 1/4” steel in my ingot mold? Yeah. The one I made already cracked so I made a better one out of 1/4”. And I found a group of duck mold makers that want me to make them aluminum duck molds. One guy wants me to make a goose body mold but that takes more aluminum than my propane tank furnace can handle. So I need to make a bigger one and I have a keg to do it. but I want this furnace to better than the last one so one trying to piece together a good plan.
Wait... there is a catch. Mizzou SUCKS heat (insulates badly), so you never get the interior as hot as when lined with Kaowool or other well-insulating linings. I have my not so good experience with it. In that sense it is concrete from the devils.
yeah, but that's why you use an inch. It may suck heat at first, but after I shut it down that sucker will heat my garage for the next 8hrs. Now if you cast 3inch thick walls, it will take 2days to come up to temp.
