My IFB/fibre-blanket furnace build.

Thanks Pat.

I pushed through In my mini burner (during my test over using a 3/16 ID hose) on syphon almost 5 gallons per hour with maybe 3” gravitational head pressure. When I switched to WVO (in the same situation) I dropped to 1/2 gallon per hour.

(I am just going to use pneumatic food grade hose for the diesel, vegetable oil, and air delivery for my initial testing melt.)

This is where I came to the conclusion of slightly pressurizing the tanks, (especially the WVO tanks) from the turbine air blower.

I did find some ball three-way ball valves to make switching seamless.

Once I wrap the furnace with the stainless steel, I will be working on pneumatic/fluid switchgear. All ball valves and two needle valves.

I have not even considered ordering the crucible’s yet. I want furnace first, maximum crucible second.

I will probably weld up a stainless steel crucible and melt pop cans for my first burn. Maybe I'll do the 1000 can challenge. And maybe Jason will make fun of me for it and I'll end up on his shame list.

 

Today I got the couplings welded together with standoffs. Hopefully tomorrow I get the clamps so I’ll be able to remove the red ratchet straps and laser protective coating.

 

If you are going for iron temperatures, you may consider letting the IFB's protrude down between 1/4" and 1/2" below the sheet metal surface, since you will generally get some blowby at the lid/furnace joint.

For aluminum work, not a problem with the flush arrangement.

That is a pretty slick approach to encasing the ceramic blanket.

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Hey Pat, I’m definitely going for iron melting temperatures.

The heads of the screws should drop down in the V groove’s of the sidewalls of the furnace. I’m sort of hoping they are out of harms way. The 0.031 stainless steel on the bottom of the lid should take the brunt of the hit. If I find it leaks too much, and too much heat damage to the stainless steel, (I am going to use it) to clamp a cheap woodstove gasket or I might just glue it to the top wall of the furnace. I believe they are made of ceramic, somewhat a ceramic rope. If I recall correctly, they’re only rated for 1000°F. But, I think they’re only $10.

The marker X’ed out Area on the top of the furnace is roughly where the stainless steel will lay. The heads of the screws should fall between the V’s.

 

Here’s a question I have. What should I expect will happen to the ceramic wool in the exhaust??? I don’t mind if it melts a little bit and recedes. I didn’t really want to cote it with any refractory either. I figure, the stainless steal at the top of exhaust is going to take a shit kicking. The ID of the brick is 3 7/8” and the stainless steel ID opening is 4 1/2“.

Edit; the ceramic wool has a 2300°F rating.

 

You will be ejecting fibers into the airstream if you don't either coat the ceramic blanket in the lid, or perhaps put some IFB parts in there.

The stainless on top may or may not overheat.
The hot gases tend to go straight up, so maybe you will be ok.

I tried one of those low temp gaskets, and it turned molten in about 5 minutes, and will adhere your lid to your furnace if you are not careful.

Here is Version #1 of my furnace, where the lid overlapped the hot face shell by two inches, and the IFB's came up next to the top of the hot face top edge.
The result was to trap the leaking hot gasses and direct them onto the stainless.
The stainless gets very soft when it is red, and in extreme cases can even melt.

I had to redesign the entire top of my furnace as far as the IFB's, and rework my lid too.
Luckily I did not have to change the hot face.

 

Here is the redesign with IFB's flush with the top of the hot face, but I still had issues with the stainless shell on the lid overheating (see second photo).

 

And the final fix was to fill in the 2" lid recess with high temperature (3,800 F) filler, and bring the filler out over the stainless shell lip.
I put a thick layer of graphite on the top of the furnace, and then closed the lid while the filler was still soft, to get a somewhat exact fit.
This worked well, and any lid leakage just exits horizontally without really affecting anything.

If the lower stainless shell overheats, that is no problem since its only function is to cover the ceramic blanket.
If the stainless shell on the lid overheats, the refractory in the lid falls out into the furnace.
I should have keyed the refractory to the lid shell in about 4 places with short bolts welded to the inside of the stainless lid shell.

So had I known then what I know now.........
Hindsight is 20/20, and now I know exactly how to do it.
Iron temps are most unforgiving as far as overheating things that get in the way.

 

Thanks Pat. That was a little bit of a kick in the nuts!, but I’m OK with that. I’d rather fix by learning from your mistakes than mine.

In the picture below, how are you getting leaks through the fibre blanket in “A”?

In “B” I can see where a good seal could affect any furnace...., now you have me worried.

 

The overheating at A was just a result of the hot gasses being directed upwards, and that part of the shell was protruding out into the hot stream of gas.

If you look at the myford and other designs, they don't try and use a lid with a lip that protrudes down, and for good reason, because with the positive pressure inside the furnace due to the leaf blower providing combustion air, even with a 4" hole in the lid, there is still a significant pressure inside the furnace, and so the lid will generally leak at the lid/furnace joint.

If there was such a thing as a 4,000 F gasket, then my overlaping lid design would be a good one.

I figured I best mention these problems to perhaps save you a bit of grief when you fire things up, or at least know what to watch out for.
With aluminum melts, you can get away with almost anything.
With iron melts, the slightest problems tend to become big problems.

The seal I am getting right now is pretty good, and that is a result of closing the lid with the high temperature filler still soft, and letting it settle onto the uneven surface of the IFB's and hot face, and then set.
Even without a perfect seal though, I now have a direct horizontal path for any escaping hot gases to exit without impinging on anything.

I almost never follow along with what everyone else is doing with furnace design, and so I can tell you a lot about what does and does not work when you deviate from the design that most folks use.

The intent of my design was to eliminate as much dense refractory as possible, and minimize iron melting times, and so that meant eliminating the upper and lower flanges that you see on the myford design. Probably having at least a 2" wide upper flange is a good idea.
A lower flange of dense refractory serves no purpose other than to give a surface for the sheet metal to pull up to, but my sheet metal works fine without the lower flange. The more dense refractory you use the slower your iron melt will be.

My hot face weighs 70 lbs, which I consider on the lighter side for cast refractory furnaces.
My design heats quickly and uses less refractory than a full flanged design, but I have an excellent high temperature patching compound from a local supplier too, so I can quickly fix any refractory problems that may arise (and did arise) with the lid/furnace joint.

I was looking for the durability of a 1" Mizzou hot face, but wanted to keep the hot face as minimal as possible, and use either IFB or ceramic blanket for everything else.
My lid is a 1" thick cast domed Mizzou piece with 1" of ceramic blanket on top, and then a layer of IFB's on top of the ceramic blanket to protect the ceramic blanket.

Edit:
And another goal of eliminating the upper and lower dense refractory flanges was to eliminate what will act as large heat sinks, which draw heat out of the furnace and deliver it into the outside sheet metal. I tried to eliminate any heat-sink paths and minimize heat getting away from the 1" hot face, and my furnace does a good job with that.

I am very please with the melt speed/durability balance that my furnace has.
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Another day pushing forward. Got the sidewalls on. I will cut the rest of the red handles off the strap clamps.

 

Fancy.... Now let see some fancy castings!

 

That's it, you just want to see the fancy castings? You don't want to see how I get there(pattern-making or mold), or the machining and fitting afterwards?

 

LOL, Jason is well known to be one of those types who eat all their popcorn before the show even starts.

Edit:
The furnace is looking good.
I like those clamps a lot.

You really have to operate a furnace to get a feel for it.
You can read about furnaces, but there is nothing quite like running one and shaking out the bugs that tend to crop up from time to time.
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That's me! munch munch. I can't wait to see if this thing works. It sure looks strange without a big tuyere and blower.

Matt, you don't need a hinge, light that sucker now.

 

Maybe don't get too attached to the way the furnace looks if you are going to use it for iron work.
This is scavenger's furnace after maybe 200 iron melts?
Still functional, but not really what you would call pretty.

 

LMAO, that thing is EPIC.

 

LOL at the picture Pat, 'go hot or go home....'

 

Thanks! ... those little clamps weren’t purchased that way. They were a couple hours of work 3 feet of 10-32 all thread, 3/8 SS diameter rod turned into a little steps, then SS TIG welded.

Before and after;


I figured it would be completely boring discussing the clamp, the outer banding, shim punching, and how it latch together.

I definitely suspect there will be learning pains on its maiden voyage...(And I think some others here do too, with the mini torch design and the segmented decagon corners).

As I am moving forward....I’m trying to keep everything that may be a consumable, easily replaced. I’m trying to keep weight down to a minimal, so I can easily relocate it. And I’m trying to keep power requirements under 15 A.

Tomorrow, hopefully I will be flipping the flanges on the lid and finishing the design, on the lid flipping support.

Then the control board... I want most of the controls for fuel, air and pneumatics about 8 feet away from the furnace.

I can totally skip to the light her up and tweak video, maybe this weekend.