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Brian Wong Shui 03-29-2011 11:22 PM

Quote:

Originally Posted by Lawrence Duckworth (Post 95572)
Brian, thanks so much for your help. I’ve been down there a couple times now and sure wish I would’ve bumped into you…

I’m getting close to tackling the door and s/s front. The expansion is something to ponder for sure…and the weight of the door too, maybe a counter weight on the backside of the bridge assembly.

The skin is 26 ga.coil stock from the local metal roofing supply house, probably should have gone with something heavier, (16ga.nmaybe??) anyway, fastened with a strap and 2- ¼-20x5/8” ea. I’m guessing the skin is in four sections for expansion, otherwise a sheet of stainless would have been a bunch quicker and less hassle…but then wrenching all the nuts down kept my middle granddaughter busy:).

Lawrence,

26GA is awfully thin. Our furnace skin is at least 11GA if not closer to .125" (I'm going off of memory here). Remember that the skin is holding the 3 castings on the inside together. You might think that they are heavy and won't move but they will.

Did you use the correct fiber against the castings? Inswool HP (or equivalent) won't cut it. The continuous operating temperature limit for HP is 2150F. Use something like a Inswool HTZ which has a continuous operation temperature limit of 2450F.

Pete VanderLaan 03-30-2011 04:38 AM

I agree with Brian. That metal needs some pushback capacity to it or the castings will go out of alignment. I haven't yet faced the door issue but I will soon. I have one spare but it is such a heavy thing that I want to lighten it up and go with a bunch more fiber and a ceramic shell on the hot face.

Brian, how long was that element in service? I occasionally hear about failure's like that. I've just never had one. I just usually melt the connectors.

Brian Wong Shui 03-30-2011 06:05 PM

Quote:

Originally Posted by Pete VanderLaan (Post 95577)
I agree with Brian. That metal needs some pushback capacity to it or the castings will go out of alignment. I haven't yet faced the door issue but I will soon. I have one spare but it is such a heavy thing that I want to lighten it up and go with a bunch more fiber and a ceramic shell on the hot face.

Brian, how long was that element in service? I occasionally hear about failure's like that. I've just never had one. I just usually melt the connectors.

The element was in service about 3.5 years.

Pete VanderLaan 03-30-2011 07:16 PM

That's not bad. I have heard it said that they have no known lifespan if run at 2400F but I don't believe it. I have broken most of mine through conventional raw stupidity well before they have gotten that old.

Lawrence Duckworth 03-30-2011 08:46 PM

Quote:

Originally Posted by Brian Wong Shui (Post 95576)

Did you use the correct fiber against the castings? Inswool HP (or equivalent) won't cut it. The continuous operating temperature limit for HP is 2150F.


Brian,

I used the Inswool HP.....

Brian Wong Shui 03-30-2011 10:34 PM

Quote:

Originally Posted by Lawrence Duckworth (Post 95592)
Brian,

I used the Inswool HP.....

Lawrence, I'm not quite sure if the castings are made with an insulating castable. (I suspect not). The worse case is that it isn't. So for a 4" thick casting with 8" of HP in a vertical cylinder you are looking at the following. (I ran the numbers through HWR HEATransfer 2003)

Batch Cook
Hot Face: 2350F
Casting/Frax Interface: 2113F (Wall), 2199F (Roof)
Shell Temperature: 220F (Wall), 245F (Roof)
Ambient: 78F

Operating
Hot Face: 2050F
Casting/Frax Interface: 1875F (Wall) 1940F (Roof)
Shell Temperature: 188F (Wall); 206F (Roof)
Ambient: 78F

The best case is that it is an insulating castable with similar thermal properties to Kastolite 30 where you would be looking at the following temperatures:

Batch Cook
Hot Face: 2350F
Casting/Frax Interface: 1909F (Wall), 2048 (Roof)
Shell Temperature: 193F (Wall), 222F (Roof)
Ambient: 78F

Operating
Hot Face: 2050
Casting/Frax Interface: 1702F (Wall), 1817 (Roof)
Shell Temperature: 168F (Wall), 189F (Roof)
Ambient: 78F

HP has a max service temp of 2300F and a continuous use limit of 2150F. So you'll be above the continuous use limit under certain conditions but below the max service temp for all conditions. If you haven't sealed up the top yet, I would replace 2" of HP for 2" of HTZ for the frax against the crown.

Lawrence Duckworth 03-31-2011 04:32 AM

Now that’s the kind of information I’m looking for!! the site required a registrationn though…maybe tonight.
I was looking at HP melt temperatures and Spruce Pine Cullet operating temps??.

Anyway I’ve had my breakfast and am off to the @#$%&* ART making process again.....

Pete VanderLaan 03-31-2011 05:30 AM

When Brian uses the figure of 2350 for a batch temp, it's not inaccurate but it is high for what you need. When I did the performance tests for SP Cullet, I really didn't need to melt above 2195F. If I was melting SP87 as a batch, I would want 2350F for about a five hour burst. So, you have to ask yourself if you really ever plan on getting away from the cullet. In a 300# furnace, you might push it to 2250 max. I do all of my batch melts now at aboput 2225F. I just take a bit longer. The glass is better for it.

The reality for me is that ALL fiber gets stressed after a few years and the insulating value begins to collapse. If you look at the elements and the passage brick, the element is operating at 2800F at the bottom of the brick so the casting is really being exposed to that temperature for a lot greater time than you might think. The result has been deformation at the holes in the crown and sometimes cracking. That is probably a cost of doing business.

So, if you want real flexibility in the furnace, switch to the higher temp fiber. It's simply more coin. If you really think you are going to run the cullet, which is great stuff, I think you will be fine. Your furnace and crucible will love you for it and so will your electric bill. And if you change procedures down the road, you will be taking the furnace apart again .

Mine has deteriorating performance from when it was new two years back. I will open it up in May and we will see where the problem is. I know I have 1.5 inches of glass on the floor but that shouldn't do it. I have to assume the passage brick is compromised. Charlie Correll and I will be making passage brick for sale as well.

And the castings are not insulating castings. It's a proprietary in house refractory mix.

Lawrence Duckworth 04-04-2011 07:55 PM

The door has 5 layers of superwool, and about 3 inches of castolite-30
The door assembly has an adjustable counter weight on the back side of the bridge allowing a very light touch and rolls ez on the two wheeled end truck.

.....that’s about it till the transformer and molly’s get here.

Anybody ever run across a complete electrical drawing for these molly furnaces?

Lawrence Duckworth 04-04-2011 08:40 PM

One bag poured the door with maybe a handful left over.

Pete VanderLaan 04-05-2011 05:59 AM

I will gt the elements shipped by the end of the week Lawrence. Steve says you should have more spare straps than I was going to send. I suggest 20 in that case. The schematic you are looking for is in the Ark of the Covenant. ( there really really really isn't one).

I also did have yet another bussblock issue with my furnace two days back , coming in to a bank of elements being down and had to replace one on a Sunday. Spares are good. It's the second time in two years doing the same one in the transformer. I had to cut the cables back about eight inches. Steve said I'm the only one to ever have transformer issues. My straps after two years look like they are brand new on the other hand.

You are doing a great job on that furnace.

Pete VanderLaan 04-05-2011 06:00 AM

I will get the elements shipped by the end of the week Lawrence. Steve says you should have more spare straps than I was going to send. I suggest 20 in that case. The schematic you are looking for is in the Ark of the Covenant. ( there really really really isn't one).

I also did have yet another bussblock issue with my furnace two days back , coming in to a bank of elements being down and had to replace one on a Sunday. Spares are good. It's the second time in two years doing the same one in the transformer. I had to cut the cables back about eight inches. Steve said I'm the only one to ever have transformer issues. My straps after two years look like they are brand new on the other hand.

You are doing a great job on that furnace.

Dave Hilty 04-05-2011 06:43 AM

[quote=Pete VanderLaan;95734] "Steve said I'm the only one to ever have transformer issues. My straps after two years look like they are brand new on the other hand."

Not. I had the very same issue last year and sourced the aluminum blocks from a local electrical supply house.

John Riepma 04-05-2011 07:29 AM

Lawrence I sent you a PM

Pete VanderLaan 04-05-2011 08:06 AM

[quote=Dave Hilty;95735]
Quote:

Originally Posted by Pete VanderLaan (Post 95734)
"Steve said I'm the only one to ever have transformer issues. My straps after two years look like they are brand new on the other hand."

Not. I had the very same issue last year and sourced the aluminum blocks from a local electrical supply house.

******************
Turns out they are made just down the road from me in Manchester. I don't know if I can buy them direct yet. My latest failure was with the fan always running. It was not nearly as severe. and I credit the fan.

Lawrence Duckworth 04-05-2011 07:09 PM

Quote:

Originally Posted by John Riepma (Post 95736)
Lawrence I sent you a PM

Please check your PM mail box again.
thanks

Charles Friedman 04-07-2011 12:07 PM

Quote:

Originally Posted by Lawrence Duckworth (Post 95727)
One bag poured the door with maybe a handful left over.


This is when a vent could have been cast in place. Threw the door and up, in a pipe attached to the door trolley, “Door /Vent”

Lawrence Duckworth 04-12-2011 03:47 PM

The mollys showed up today and I tested all the tubes for continuity before signing off on the UPS ticket….maybe they’re not really all that fragile after all :)

For what its worth, I hooked the furnace from the top to load and offload. I put the crown and the pot in after we got every thing over to the barn.

Pete VanderLaan 04-12-2011 05:43 PM

Quote:

Originally Posted by Lawrence Duckworth (Post 95896)
.maybe they’re not really all that fragile after all :)

.

**************
Hah! I had six broken elements in my last shipment. You're supposed to say that the crate was really intelligently designed and prevented these gossamer wing thingys from shattering. ( Just wait...). I bet your UPS driver was just thrilled.

That shop in the background by the way is beautiful.

Lawrence Ruskin 04-12-2011 06:48 PM

So what happens if one or more of those elements flunks a continuity test?

This is my first moly element shipment

Pete VanderLaan 04-12-2011 07:05 PM

The very last thing I did today before placing your elements in their crate was to test their continuity. You do it through the end of the box where the round larger ends protrude if you poke about gently in the foam rubber. DON'T TAKE THEM OUT OF THE PACKING you will just be tempting the fates. Just probe with a continuity tester on the ends. There are two in each box. If they have continuity, leave them alone until you need them.

The crate has two wooden bulkheads at each end. It has bracing struts 12 inches down the box on the top and bottom. In the middle of the crate is an inner wooden box built out of chipboard and 1x2's. Most of it is hotglued in place like the other bracing but the top 12x12 is screwed. Remove the screws and take the elements out in their cardboard inners.

When you do get at the elements to use them, they have two wooden braces in the elements themselves to prevent compression or tension. You will have to remove the wood on the cold zone. Do it very carefully. On the hot zone, let it burn out. If you try to pull it, you'll break it.

These things are well packed. Yours are better packed than the ones for the other Lawrence since his were more locally shipped. It's coming via an expensive fed ex air delivery. It's the only way I do international. UPS is just unreliable.

Jordan Kube 04-12-2011 11:16 PM

It's a good idea to keep them in the packaging but it's also a good idea to get a spare element packed into a brick to have on hand in case of inconvenient element failure. Put it in a padded box or something if you're worried about breaking it.

Lawrence Duckworth 04-13-2011 06:41 AM

When drilling the holes in 2800fb do you guys over size the first 6 inches or so and size the last 3 ?

John Riepma 04-13-2011 06:50 AM

Everyone will have a different opinion/method on this, but here's what I did. I drilled two holes the length of the brick on 2" centers with a 1/2" aircraft length drill on a boring mill. The bricks, while 2800's, are still punky enough to drill easily. The holes are slightly larger than the element shank (.040"-.060") and the element slips in easily. To prevent the chimney effect I cut pieces of high-temp fiber paper the size of the end of the brick and die-punches two holes in them slightly smaller than the element shank. I slipped these onto the top of the shanks above the brick and below the electrical connections where they would be cool enough to not degrade and tight enough to prevent the chimney draw from starting. We have not seen any problems at all after 3 years. Melting Spruce Pine batch, leaving the door cracked open slightly when charging to vent.

Pete VanderLaan 04-13-2011 08:10 AM

The on center for a 6/12 element is 50mm. The on center for a 9/18 element is 60mm. The diameter of a 6/12 is 12mm or a touch under 1/2 inch. The diameter of the 9/18 is more like 3/4 inch.

When making a passage brick for a 9/18, you need to use a 3" thick 2800 IFB

Charlie and I will be making and selling passage bricks.

I don't really see the need for having an element/brick unit made up. It only takes about fifteen minutes to have it ready and when you have lost an element, you have pretty much lost the blowing session anyway. While one person is dismantling the old unit, the other can be readying the element, unless there is only one of you of course, a rarity it seems in hot shops.


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