View Full Version : Pot okay?

Lia Howe
02-15-2012, 12:40 AM
Did I get your attention, sorry to be misleading but I have a pot question.
I have a Stadleman, I started it up a couple of days ago. It got to temp and then I got sick. Hit by a truck sick. I didn't put glass in (thank God) I have turned it down to 1000. We use the furnace to keep our whole shop warm. Am I going to do any damage to the pot? I am just trying to save a little $$$$ ( did a year to year costs and our electric bill has doubled, yup doubled) Any advise about the furnace not the "I'm dying with some sort of a bug, a big ass bug.

Rollin Karg
02-15-2012, 05:16 AM
It's better to keep it around 1800, at 1000 you're in the danger zone with regards to Quartz Inversion. At idle the savings difference between 1000 and 1800 will be small.

The electric consumption over last year could be a different issue. Is it an older furnace and what size ?

Pete VanderLaan
02-15-2012, 06:49 AM
Lia has an older stadelman. It may have the dreaded doughnut ring of liberated glass. It also may be that the electric rates have gone way up and it's certainly worth looking at. Hanging around quartz inversion is just asking for trouble. Either shut it off or, as Rollin says, take it up to 1800F.

Peter Bowles
02-15-2012, 06:57 AM
You are at serious risk of dunting at 1000, assuming you mean fahrenheit. The temp gradient from top to bottom of the furnace - and through the pot will exacerbate the risk of cracking at this low temperature.

I'd be happy to hold a pot almost indefinitely at 1000C, without any risk to anything. The risk of damage to the pot also greatly depends on how much glass you have in there still and how old the pot is.

Tickle it back up to cherry red and don't be opening the door till you get there.

Lawrence Ruskin
02-15-2012, 07:36 AM
If you have that flu that's going around, I have some advice on how to regain your will to live...

David Russell
02-15-2012, 11:13 AM
In this thread, I have read the first reference to the notion that latter built stadelman's are designed to prevent the dreaded "jellyroll". Do I have this correct?

Pete VanderLaan
02-15-2012, 11:24 AM
The problem exists when the floor fills up with glass so much that the glass breeches the joint between the floor piece and the walls. My 28 inch unit could allow five inches of glass to build up before it was breeched. The floor doesn't automatically fill up. You either have to have had a leak or to be sloppy charging for a long time. I can't say how the earliest units were done. Checking the cleanout occasionally would certainly give you a heads up.

Rollin Karg
02-15-2012, 01:45 PM
Pete, how do you get the five inches before the Breech ?

Pete VanderLaan
02-15-2012, 03:05 PM
My floor is a monolithic casting that is like a big shallow pot, five inches deep. The walls sit on the lip of that pot. It's a wide lip. It has to totally fill the pot before it can flow through the joint. I came very close this last time, about 1/4 inch. The furnace was acting it too, very sluggish with that extra 300 lbs of glass down there. Air chisel...

Cecil McKenzie
02-15-2012, 08:00 PM
Many furnaces don't don't give the operator the luxury of knowing what is going on inside the furnace. I have talked to people who thought glass was leaking out a spot on the side of the crucible so they kept running but didn't fill above that level. After the crucible started to float in the furnace and they shut down they discovered the hole was in the very bottom of the pot.

I have thought that if there was a sump hole in the floor of the furnace where you were confident that glass would flow to in the event of a leaking crucible then the hole could be filled with frax and a thermocouple could be placed in this hole and monitored. While the frax was intact it would read much less than the interior temp. of the furnace but if it approached the running temp then you would know enough glass had been lost to fill the sump and that it might be prudent to shut down to avoid the jelly roll effect.Actually the opening to the sump hole could be say 1/2 inch above the floor so glass would not go in till a fair amount was lost.

The effectiveness of this would depend partially on continuous good housekeeping, like making sure batch or cullet goes in the crucible not on the furnace floor, cullet is small or heated so it doesn't pop all over , gathers are made carefully with dripping glass going in the crucible.

This method may not help much in a catastrophic loss but would work against slow insidious leaks that might go unnoticed for a long time.

Michael Ahlefeldt-Laurvig
02-16-2012, 10:06 AM
My floor is a monolithic casting that is like a big shallow pot, five inches deep. The walls sit on the lip of that pot. It's a wide lip. It has to totally fill the pot before it can flow through the joint. I came very close this last time, about 1/4 inch. The furnace was acting it too, very sluggish with that extra 300 lbs of glass down there. Air chisel...

I agree completely with this- I did the same on my pot furnace- the whole bottom surface also had a few degrees fall towards the cleaning port and it was a simple matter to clean out through the port once a month or so, Id do it in the morning after a melt before the furnace had cooled down to working temperature,- it would take 10 minutes or so. After 15 years when I retired the furnace and tore it down, there was no glass what so ever in the insulation. It was actually very difficult to get the bottom apart- that baby was baked. We used to melt at 1330 C in clay pots.

Tom Clifton
02-16-2012, 11:29 AM
Content moved to a separate thread " Glass Conductivity: Monitoring Catastrophic Pot Failure"

Rollin Karg
02-17-2012, 05:11 AM
Lia, I was thinking about this morning when I woke up. There are other things to consider here. How good is the fit on the door ? In addition to the Jellyroll you can actually have a cavity in that area. If you load batch in an unvented furnace there will be a certain amount of pressure from the moisture coming off the batch. My furnaces have a 400 pound pot and it takes 500 pounds of batch to fill them, that’s a lot of moisture that has to go somewhere. It will create pressure inside your furnace and take the path of least resistance trying to get out. If there are cracks in the bottom then the mixture of steam and batch can push through and attack your Frax. Pretty soon you have no insulation in that area and performance suffers. It also chews up doors and gathering ports on it’s way out.

The furnace we just built has a removal ring in that area, it’s there to make it easier to deal with this problem. I also have a furnace that is not performing well and it’s older and doesn’t have the removable ring. We’re going to try and add that ring at the next pot change and we want to do that without totally rebuilding the furnace. I’m busy filling orders right now, but as soon as we get caught up we’re going to get after it. Probably in a month or six weeks. I’ll post some photos then.

Electric bills can go up because the furnace is failing. They can also go up because you’re utility is just charging more and or changed the way they figure your bill.

Hopefully you’re getting some good help offline.

Pete VanderLaan
02-17-2012, 06:00 AM
If you get a point and shoot laser thermometer, it can tell you right away if the insulation has failed. If you use Spectrum nuggets, you can expect them to dissolve your furnace, the door in particular.

Rollin Karg
02-17-2012, 06:11 AM
If you get a point and shoot laser thermometer, it can tell you right away if the insulation has failed. If you use Spectrum nuggets, you can expect them to dissolve your furnace, the door in particular.

These are real handy and the prices have come way down. Under $100 makes them accessible to everyone.

Pete VanderLaan
02-17-2012, 07:49 AM
These are real handy and the prices have come way down. Under $100 makes them accessible to everyone.
Mine was a Ryobi for $40.00 at home depot. It only goes to 600F but I actually don't need more than that for this job. I have an optical pyrometer for the serious stuff. It costs more.

Lawrence Duckworth
02-17-2012, 10:51 AM
David Russell recommended that I map a 6 inch grid on the outside surface of the furnace and monitor those grid temperatures from time to time......

Tom Clifton
02-17-2012, 02:02 PM
Mine was a Ryobi for $40.00 at home depot.

Also check Harbor Freight (http://www.harborfreight.com/non-contact-laser-thermometer-96451.html) for this and other useful items.

David Russell
02-17-2012, 03:22 PM
That must have been some one else lawrence, but then again i have a 2 yr old boy so it might have been done in a state of exhaustion! I do love the knowledge that my temp gun provides.

Lia Howe
02-17-2012, 05:48 PM
Lots of info. I think that I may be losing heat through the top. Around the elements. I have melted hoses in the past. I re insulated and that problem stopped. I am using Spectrum nuggets and I have not noticed any really bad corrosion. I am probably not using my furnace as much as some of you. I am very careful when filling so that I don't spill or anything pops out of the pot. I am almost the only person that works out of my furnace, I will admit to gubbering a little when I am cleaning out the pot with the ladle. Belly fat gets really hot. I try to rush and spill a little. I hope to never change a pot to discover the mess I have made under it. I know Pete, it is only wishful thinking on my part. I will get the privilage someday.Lia

Pete VanderLaan
02-17-2012, 06:40 PM
I strongly suspect, based on what you just said, that you have developed chimneys around your passage bricks and that heat is escaping around those bricks in a major way. Is your furnace achieving temperature much more slowly now than when it was new?

Lia Howe
02-21-2012, 12:48 AM
I can't really say that I have noticed. Now that my furnace is up, can I work with that material Steve gave me an re cover the passage bricks while its hot? The material is meant to be wetted and then smoothed over the top the bricks to eliminate that loss of heat? Like a thermal blanket of sorts. I would of course turn the power off while doing this as I don't want to electricute (sp?) myself.Lia

Rollin Karg
02-21-2012, 02:52 AM
You can do this while it's hot. Make sure that the areas around the Passage Bricks is well stuffed with Frax then seal with the rewettable clothe. The idea is to prevent any air movement out of the furnace. Once you get a small leak it will quickly grow. There are some recent photos on here of some well done installations. I believe they might be in the furnace Build thread.

The suggestion about using the remote sensing Thermocouple is a good one and might help you make a quick accurate diagnosis of the problem.

It's good you're brave enough to ask questions on here, you're probably helping a lot of lurkers.

Pete VanderLaan
02-21-2012, 06:59 AM
Lia, the rewettable cloth ( dip lag) is not an insulator at all. It is a material designed to keep dusting down. The insulation issue I refer to is around the passage bricks as they approach your crown. That area needs thorough inspection.

With the Power off of course. Use the infrared laser thermometer. It saves lot of time.

Lia Howe
02-21-2012, 08:18 PM
I will probably attack this task next week. I can't say that I have had any real noticable problems. I just can see the red on top and that tells me heat is getting out.
Thanks Rollin, I am most times a lurker because I don't want to sound like an idiot. I live my life by a saying that my dad had, The only stupid questions are the ones you never ask.Lia

Steve Stadelman
02-21-2012, 08:42 PM
If you already see red you are late, late, late! Don't wait until next week!

Lia Howe
02-21-2012, 09:21 PM
I went out and looked closely at what needs doing and really there is only one real trouble spot. I haven't put glass in yet. Can I play around on top with glass on the pot? Nothing should land in the pot. Even empty if something landed in the pot what exactly could I do to get it out? It's not like I can stick my head in and take a look around. When it was cold once I put my camera in and took a picture of the bottom of the pot. Very exciting!

Pete VanderLaan
02-22-2012, 05:59 AM
Get some fresh fiber. Turn the furnace off. Get on a ladder and inspect every passage brick. You have chimneys if you can see red. Not only is it expensive as you know, it will fail if you don't repair it. You do not need to empty the pot but you do need to cut the power off.

Do it today, not next week.

Lia Howe
02-22-2012, 10:57 AM
I am finding this learn as I go kind of tough. Is there a Stadelman Furnace Maintenance Manual for Dummies (or even the Idiots Version) out there? I need something that tells me what to look for when I am inspecting everything before I start up each time. What to look for? What to check? Run screaming if you see?Lia

Pete VanderLaan
02-22-2012, 12:42 PM
Basic maintenance for the Stadelman furnace has been repeated in this forum time and again. Search the archives. You've had that furnace for years. What have you or have you not been doing all that time?

Lia Howe
02-22-2012, 09:22 PM
Hey, don't pick on me. My furnace has been running with NO problems. I have done basics. I was just curious if there was something written down.Lia

Lia Howe
02-26-2012, 09:05 PM
I did it. All my little red holes are now filled with frax. It looks like my elements are coughing up cotton balls. Furnace it working great. Just filled it with glass. Lia

Allan Gott
02-26-2012, 09:26 PM
You'll have to keep repacking the frax Lia. Without some rigid backing like the diplag that's been mentioned, the frax will still allow venting, venting will carry some flux, flux will eat frax, holes will reappear.

I don't think you're done with this issue. Passage bricks and their ports need close inspection/repair next time you shut down.

Lia Howe
02-26-2012, 11:22 PM
Thanks Allan, I was doing this as only a quick fix. Now that I am hot I didn't think that this was the best time to be playing with wet (or Moist ) Diplag near hot elements. My husband pointed out that hot steel doesn't like wet. I didn't want to risk stupid mistakes. When I shut down for the summer I will do better more thorough repairs that will include a layer of diplag, diplag ( just a fun word to say) I will take pictures to make sure even the smallest heat leak will be fixed.Lia

Pete VanderLaan
02-27-2012, 06:00 AM
I am guessing that you are using a commercial cullet . Is that right? Certain cullets creates the chimneys unless you vent the furnace, which we did not appreciate in the inception phases with electric furnaces. While some frax helps. it needs to be packed tightly or it will just dissolve again. It is likely that the frax still in there has turned to a melted fraxcrete and has little insulating value. You have found out why your electric bill is so high. Keep digging.

Lia Howe
02-27-2012, 02:01 PM
We found out 1 reason why our electricity was high. We have bedrooms upstairs that we never use, or almost never. Last spring we had someone stay in one of those rooms and they turned on the baseboards to 18 and never turned it down. We never checked because who needs heat in spring. Big mistake. We discovered it in Feb of this year. We run our house pretty cool in winter. SOOOOO it has probably been running non stop for about 10 months. Never trust your house guests to leave things as they found them.Lia

Michael Ahlefeldt-Laurvig
02-27-2012, 05:00 PM
There is ceramic fiber paste that comes wet in a bucket that is great for doing hot repairs and is much more durable and resistant to gases than fiber blanket. Its sort of expensive, but really good for around doors , chimney situations etc when you dont want to shut down.
I get it in 20 kg buckets but Ive also gotten it in caulking gun size tubes. It lasts forever if you keep a plastic film tight over the surface and seal the bucket well. It doesent like to get below freezing (in the bucket)

here is a couple of quotes from different companies
Marketed under our brands of Superwool® Fibre and Kaowool®, Morgan Thermal Ceramics’ versatile mouldable putties are excellent solutions for patching refractory cracks, penetration seals, and metal stud protection. Our mouldable products are ready-to-use for temperatures of 1100°C/2000°F to 1300°C/2400°F. They feature excellent strength and low fired shrinkage.

Fiberfrax Moldables and Pumpables
Fiberfrax LDS and LDS-AL moldables consist of Fiberfrax ceramic fibers dispersed in a sticky water-based refractory binder. These materials have a putty-like consistency which permits application by caulking, troweling, or hand forming.
Both products adhere well to most surfaces. Drying is accom- plished at a noncritical, elevated temperature, and the resulting dried material is strong, hard, and erosion resistant