On building a Satanite/Wool furnace lid

I have put on hold my plan to build a lid of perlite and Satanite in view of the comments made by various members concerning the negative experiences they have had with perlite. I do intend to test some Satanite/Perlite bricks at some point once I get my new lid on my old furnace.

For this lid I decided to use satanite on wool. I made a wool/Satanite lid a while back that worked fairly well but eventually failed partly due to failure of the vent liner and partly due to the Satanite/Wool bond failing. I think some of that was due to my less than optimal technique in applying the Satanite and also due to the fact that the wool was simply laid in flat in two 1" layers. On my book-stacked wool there will be support for the wool provided by the lower steel rim of the lid shell and by a stainless wire that skewers the pieces of wool and that wire will be suspended from the lid shell.

This lid will have book-stacked wool and hopefully better technique in applying the Satanite. In addition I will use a wool/Satanite liner. If it appears the W/S liner is not holding up, I will make a bubble alumina castable liner with expansion joints as any fully cylindrical element in a furnace cracks.

Complicating my build is the need to set the muffler on top of the lid. I am still mulling exactly how that interface will be handled for this build.

I am including a few pics and a brief video of a couple of the more interesting aspects of this build just in case that may be of interest.


Here is the partially packed lid with the skewering wire visible entering the stack on the right.


A detail of the skewering wire and its vertically-oriented suspension wire that penetrates the lid and will be tigged to the lid top surface after the lid is packed.


Some 2600 degrees wool wedges


Tigged ends of the suspension wire on the outside surface of the lid. I found that just striking an arc on the wire a cm from where it exits the lid forms a ball of SS on the wire as it melts and that ball can be followed right to the lid and then melted into the lid surface by just holding the torch on it for a few seconds.



Here is a short video of making pie-shaped wool pieces for the lid.


I should be putting up some more of the build/completion of the lid tomorrow. I am anxious to fire up my furnace and make some more levels.

I have made 5 epoxy splash patterns of the original wood pattern so that I can pour multiples and not have to pound on the relatively delicate vinyl and wood original. The vinyl lettering is especially vulnerable on the original. I will probably post some on the splash pattern making as well as I found that to be a somewhat interesting process too.


Denis

 

You might want to taper the inner edge.

 

Thank you. I agree. That is in the plan. I intend to trim the vent to make a smooth hole, taper the edge, and trim the wide surface of the lid to reduce bumps before applying the Satanite.

Here is the hot side of the lid with two heated thin coats of Satanite. Note that the vent hole is broadly chamfered as recommended by fishbonz.


Denis

 

Dennis, what is the final thickness of the wool to metal lid? I do like your threading design! I would have took a side tack approach.

 

Side tack?

The lid is 4 inches at the rim tapers to and 3 at the vent.

Then I cut the chamfer and applied the Satanite.

I WILL like the lid if it is reasonably durable. Time will tell. It seems like the wire should help support the wool. The wool was tightly packed and is very self-supporting at this time. But many heating cycles will cause it to lose resiliency and it may shrink some. Will it continue to maintain self-support?

Denis

 

Yes something like this. Or maybe with 10-32 threaded rod and a couple nuts on the outside. Knowing me I’d probably even add thin stainless steel hangers with expansion joint that T into the Satanite.

 

I see what you are thinking, Matt. My comments would be
1) I wonder how one would drive the rods through the wool and hit holes in the lid sides
2) Given how relatively weak wool is the amount of steel in this plan seems more indicated for dense castable.
3) In reality I don't think my wire will do very much, but it just might help keep the "books" of wool aligned with each other and might reduce sag to some small extent. I am actually relying on the added stiffness of the Satanite and the tight packing of the wool to provide most of the support for the lid insulation.

Denis

 

So your wool is also “book-stacked” on edge in place I think based on the photo. In my case a steel “shelf” around the outer under surface of the lid supports the strip. Nicely done. I hope I can fire mine this weekend. ( My foundry time has taken a big hit as my grandkids are out of school by my daughters choice as a precaution related to the Corona virus. My wife and I are caring for them much of the day. ).

How many melts has it withstood and what metal?

Denis

 

Yeah, right click on the desired image, click on "Copy Image Location" then paste that between img tags, like this.

Code:

[img]http://forums.thehomefoundry.org/index.php?attachments/20190504_135619-1040x780-jpg.7144/[/img]
[img]http://forums.thehomefoundry.org/index.php?attachments/20190504_135555-1040x780-jpg.7145/[/img]

 

I strongly agree that the dome shape is beneficial. I took second best as I did not have an easy way to make a doem and did not have and appropriately sized one for use. BUT, I definitely intend to learn how to hammer form a dome. Not that hard from the vids I have watched and I think beneficial enough to warrant the "trouble." Next time...

Denis

 

The top does not need to be domed, just the bottom of the load bearing structure. Think of a stone arch bridge.

 

Aren't these one in the same? The candy shell built into an arch creates its own support.

If I were to cast a complex shape that has expansion and contraction characteristics in a furnace, I would hang the hot face from expansion rebar wire. Somewhat like a suspension bridge.

 

The reason I like the dome is that the book-stacked wool is pressed into the dome just like stones are formed into a dome. (In real life stone domes are often stacked on wood domes while under construction with wood removed upon completion) Domes are self-supporting as discovered thousands of years ago. Also allows for some movement due to heating and cooling. I believe the nature of wool is such that it will remain stacked pressed together far better than it will hang from wires or rods in the long run.

Exactly how wool would be arranged as an arched bridge with presumably horizontal courses on top of an arch escapes me. I’d like to see this idea expanded upon or sketched out.

Denis

 

If you've got a China Town nearby look up a cookware shop. Commercial woks come in many different sizes and are relatively cheap, that's what I used to make my domed lid years ago.

 

It's easy to make a domed lid with wool, you have to start with a 4" deep shell. Cut the wool 4" thick on the outside and taper to 2" at the vent.

 

I can see I did not articulate this well. The bottom of the lid castable refractory/Wool needs to be domed. That way it stays in compression and does not fall off/away from the meatal use for the casing. The metal casing does not need to be domed. Fishbone's explanation is spot on. You do not need a doomed metal casing, just the lower edge of the ceramic need have a dommed shape.

A picture is worth 1000 words. See attached cross-section.

 

I think there is a structural difference between stacking the wool into a domed lid(configuration) vs simple radial stacking of the books (bricks) of wool. The pie shaped stacking which is done in a flat stack in a flat lid is equivalent to stacking a full circle pie of stone and then cutting the under-surface into a dome shape. Those stones are keyed only in one plane. On the other hand, initially stacking the the stones using a dome form, keys them both in the horizontal and vertical planes and is intrinsically much stronger and allows the stack to open up a bit with heating and close down a bit with cooling. The heat/cool movement is probably more important when using IFB than with wool. However wool does lose some of its resilience with with heat exposure.

I can see the value of using thicker wool. I used what I had bought six month ago when going in a different direction.

The wok idea is great. I wonder how many years it would have taken me to think of that one. Not only is the metal preformed saving a day of hammering and not quite getting it right, but woks are thicker in the center area than the 16 ga steel I would likely have beaten into submission.

Denis