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Old 04-21-2020, 08:50 AM
Eli Zilke Eli Zilke is offline
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Moly furnace conversion to natural gas?

Hello all, hope everyone is staying safe and healthy. I work for Water Street Glassworks a nonprofit school in Michigan where we teach classes, have renters, and do make it take it. Last year we converted from a homemade invested crucible furnace with a Gibberson burner to an older Stadelman 300 pound furnace to ease the mind of the building owner of our beautiful historic building (There are three condos above the studio). I love the new furnace but we have found that electric in our area is cost prohibitive. We went from an $1000 gas bill to a $2500 electric bill. Has anyone made a hybrid furnace that uses the electric to maintain set point but assist by a natural gas burner running at a contact pressure? Or total conversation of a Stadelman to gas? Thanks in advance Iíve learned so much from this board over the years.
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Old 04-21-2020, 10:28 AM
Eben Horton Eben Horton is online now
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Pratt fine arts in Seattle had one a few years ago when I was there. They ran it just as you described.
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Old 04-21-2020, 11:23 AM
Josh Bernbaum Josh Bernbaum is offline
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I have a moly furnace and have long thought about finding a way to have it be a hybrid instead. I'd love to have the ability to do melts with the speed of a gas burner with decent BTUs, but be able to idle/maintain working temp using electricity to the elements. Also would be nice to turn on the burner during power outages. I've briefly picked Cheyenne's brain about this in the past, but we didn't get too far yet.
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Old 04-21-2020, 11:41 AM
Eli Zilke Eli Zilke is offline
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Do you think the added air movement/ vibration would be an issue for the elements? Would you put a burner below the pot add an angle to achieve a swirling motion? Also unsure what to do about a flu For exaust? I imagine if I put it on top of the furnace it would drastically add heat and I can see having issues with element connectors. Maybe a exaust stack out the side? Thanks for brainstorming with me.
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Old 04-21-2020, 01:09 PM
Josh Bernbaum Josh Bernbaum is offline
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Yeah the flue is tricky. It would need to be able to be easily plugged when just using the elements. And would whatever burner get overheated when it's off and not having forced air going thru it? I don't know.. My 'crash cart' I built for power outages, with a venturi burner mounted to a temporary door, just has another hole for exhaust gasses in the same door. But I suspect that flue placement wouldn't be ideal if you're actually charging at high fire.

I don't know about the elements and how they'd be affected by the heat and turbulence of a flame at high fire. I'd like to know if it's possible, without compromising the elements. I don't think I'd want to try it with my dinky 6/12 elements, but maybe with the 9/18's..
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Old 04-21-2020, 01:22 PM
Shawn Everette Shawn Everette is offline
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As some one that has seen the devastating design failure of below pot burner, I'm not recommending it. If you're pot fails you're talking about major reconstruction, rather than scooping out what you can and chipping the pot out. In concept it's a good idea of optimal heat distribution, but when they fail they fail hard.

You're going to want to keep the connections at the top as cool as possible to prevent resistance at the fittings. If you've got any aluminum bus connections, toss them and get copper, it's well worth the upgrade. Consider making it a habit to check the connections monthly, it's fairly quick and can prevent catastrophic failure. Also, be careful of the cooling hoses as they can go up in flames, I ended up just putting a box fan on safety cage after that happened.

Wet dog's side exhaust work just fine, and you can route that kind of design where ever you want. Depending on what you're melting an exhaust is also a good idea in general, as I've had glasses straight up burrow their own exhaust from off gassing. High boric glasses are not friendly to the refractory in a Stadelman.

The main flaw in that furnaces design is not being able to pull a pot from the front, so if you're planning a major overhaul consider trying to redesign that in. That is unless you've got a crane, but even that's only so helpful.
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Old 04-21-2020, 01:27 PM
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Steve always told me that the elements don't do well in reducing atmospheres and degrade badly around 800F.

I still have the rectangular furnace he built me years back which takes the pot out the front. I too had the experience of seeing electric rates become untenable in NH so I sold the control panel and all elements a number of years back. I have a brand new, uninstalled crown for the furnace as well as a brand new uninstalled front plate.
Charlie Correll built me a recuperator for that furnace which sits here, never used that would fit into the left hand wall which would have to be re-engineered to accommodate the recuperator. It has no other burner systems but the blower is indeed here, brand new. No other controls.

I would love to see this furnace go into service. At my age, I have no plans to resurrect it myself. I would sell it in its entirety quite reasonably if there's interest. It would have to be shipped and involves crating and a lull to get it into a truck. It will accommodate a 400 lb pot although I ran 3 80 lb pots in it for color. It's a nice piece of work.
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Old 04-21-2020, 03:10 PM
David Hopman David Hopman is offline
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How many KWH are you using per month? I'll be dumbfounded if the rates there are higher than here in PG&E N. CA country but my bill isn't even close to that and i also have an electric glory hole.


Quote:
Originally Posted by Eli Zilke View Post
Hello all, hope everyone is staying safe and healthy. I work for Water Street Glassworks a nonprofit school in Michigan where we teach classes, have renters, and do make it take it. Last year we converted from a homemade invested crucible furnace with a Gibberson burner to an older Stadelman 300 pound furnace to ease the mind of the building owner of our beautiful historic building (There are three condos above the studio). I love the new furnace but we have found that electric in our area is cost prohibitive. We went from an $1000 gas bill to a $2500 electric bill. Has anyone made a hybrid furnace that uses the electric to maintain set point but assist by a natural gas burner running at a contact pressure? Or total conversation of a Stadelman to gas? Thanks in advance Iíve learned so much from this board over the years.
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Old 04-21-2020, 03:18 PM
Hugh Jenkins Hugh Jenkins is offline
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Wink

If the furnace is made of wall panels, You should be able to reconstruct one wall for a recuperated burner. I don't know what Charlies exit temperature is but mine is between 300 and 350 at the top of the stack. That is easily ducted out. I think charlie still uses a blower and that won't help in an electric shut down. I use compressed air and can run at 5psi from a 3 amp Thomas compressor repurposed from an oxygen concentrator. My furnace is freestanding 100#. I too have seen the failures of a burner below the crucible, which makes the pot wall hotter than the glass. I now have the burner and exhaust above the pot, with the exhaust port next to the burner. I do not know what it would do in tandem with electric, but the burner is easy to remove and the stack has a complete damper to prevent draft heat loss.
I have run my unit on a reasonable size UPS for a few hours. Its a 2 minute switch to put in a venturi-Gib head combo in a pinch.

All that said, I now run 90% of the time on veg oil. That is currently in very short supply since restaurants are shut down or limited to out the door delivery. We will see how long it takes for there to be a surplus available again. Our propane has not dropped at all yet and still is at $4.50 plus tax per gallon. Not a viable way to run for me, so we are off and pruning trees, watching the garden grow.
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Old 04-22-2020, 08:21 AM
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Pete VanderLaan Pete VanderLaan is offline
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NH approved a demand structure on ratess for commercial services. It charges $9.49 every time you use 5000 watts in a 30 minute period. That's really easy to do, particularly if you have electric equipment.

It's compounded. If you did that for another 30 minutes, it's another $9.49.

Then, you still get charged for the actual rate which varies. It's low from 8PM to 5AM at.02 kwh but you still get the penalty. Other times? It's around .12 KWH.

When I first installed my moly, the bill was about $700.00 per month. I sold the tool when it hit $2200 per month melting once a week. It has gotten far worse since I sold the tool. Now, my shop has been virtually shut off for several months using a heater to keep the chickens water from freezing at night. It still runs over $350 dollars a month, $650 if I dare turn on the annealer.

I run propane now.

Eversource is no longer in the electricity business. What they charge for is delivery and that part of the bill is infinitely more expensive than the actual power used.
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Old 04-22-2020, 08:27 AM
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Quote:
Originally Posted by Hugh Jenkins View Post
If the furnace is made of wall panels, You should be able to reconstruct one wall for a recuperated burner. I don't know what Charlies exit temperature is but mine is between 300 and 350 at the top of the stack. That is easily ducted out. I think charlie still uses a blower and that won't help in an electric shut down. I use compressed air and can run at 5psi from a 3 amp Thomas compressor repurposed from an oxygen concentrator. My furnace is freestanding 100#. I too have seen the failures of a burner below the crucible, which makes the pot wall hotter than the glass. I now have the burner and exhaust above the pot, with the exhaust port next to the burner. I do not know what it would do in tandem with electric, but the burner is easy to remove and the stack has a complete damper to prevent draft heat loss.
I have run my unit on a reasonable size UPS for a few hours. Its a 2 minute switch to put in a venturi-Gib head combo in a pinch.

All that said, I now run 90% of the time on veg oil. That is currently in very short supply since restaurants are shut down or limited to out the door delivery. We will see how long it takes for there to be a surplus available again. Our propane has not dropped at all yet and still is at $4.50 plus tax per gallon. Not a viable way to run for me, so we are off and pruning trees, watching the garden grow.
*********
One of the persisting troubles with moly's was the lack of convection in the furnace. I ran an optical pyrometer on some of them and I could measure 1100F above glass line and at the same time read about 275F at the foot of the pot. That wasn't even considering what the temp would be at the center of the pot on the outside. I'd imagine you could have touched it.

So, for a long time, we've recommended putting your exact torch in the clean out at the lowest possible setting to get some air flowing. That seemed to stop the problems people were having with thermal shock on the 24 inch and larger crucibles.
I hate burners at the base of the pot. Hugh has that temperature extreme right on the money. Firing above glass line from the side with a downdraft flue seems right.
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Old 04-22-2020, 08:39 AM
Josh Bernbaum Josh Bernbaum is offline
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Quote:
Originally Posted by Shawn Everette View Post
As some one that has seen the devastating design failure of below pot burner, I'm not recommending it. If you're pot fails you're talking about major reconstruction, rather than scooping out what you can and chipping the pot out. In concept it's a good idea of optimal heat distribution, but when they fail they fail hard.
I built my gas furnace, which is a slightly modified design of the ones I built at Charlie's years ago, with a burner below the top of the pot level and scooched back some so flame doesn't shoot at the pot so much (a long oval front to back). But I calculated the volume of a full pot spill and that's at least how high my hard-brick 'pedestal' that the pot sits on is. I haven't had the pleasure of a pot breaking (knocking on wood here right now), but in theory I don't think it would reach the level of the bottom of my burner block, or the level of the top of that pedestal. I get that a burner being higher makes sense to keep it more out of harm's way, but I have a hunch that the flame being lower is a bit more comfortable to gather out of. It makes for a higher sill height though.
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Old 04-22-2020, 09:24 AM
Shawn Everette Shawn Everette is offline
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This one was an old Wet Dog with the burner at the front that ported to the rear base of the pot for convection. If the pot broke the glass would just flow through the burner port making for a hell of a clean out. On the last pot change I noticed that the port was starting to collapse because of all the weight, abuse, and heat; and that it's time was sooner than later. Sold it to a couple guys that ended up filling in the burner hole and porting a new one in at the lip of the crucible. Still in service as far as I know.

I can't say that I've noticed a difference in gathering from one to another. Both were well insulated, so unless you're gathering for 30 seconds the burner didn't change much. On a full electric stadelman you'll definitely notice because of the loss of power from the safety shut off, make sure to keep a spare on hand. Honestly the only furnaces I've found uncomfortable were tuned too rich and gave some nice dragons breath every time you opened the door.
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Old 04-22-2020, 10:13 AM
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The other aspect of bottom fired I neglected to mention involved the very same optical pyrometer.

If I shot into the upper chamber of any gas furnace that utilized bottom firing, I could take measurements of 2300F in that upper spot. However, when I went and shot into the clean out immediately after doing that, I consistently got readouts about 450-500F hotter at the floor. 2750-2800? No crucible can withstand that for long.

Charlie and I discussed this a number of years ago and he changed his designs based on the observations that I was seeing a lot of pot losses in his older furnaces. That was back when I was still representing EC. It always looks the same. Crows foot on the opposite side of the burner. Sometimes slightly pinked.
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Old 04-22-2020, 11:50 PM
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The life of my crucibles changed considerably when I went to upper chamber burner arrangement. There is still a hot side of the pot across from the burner. I think one pot suffered from not being filled completely and having a hot edge, but that is conjecture on my part. I think charging and heating schedules are a big variable from shop to shop, but bottom heating on a fast melt schedule has to be stressful.
Early on, 2006 or so, I had the burner in front of the exhaust port. That meant gathering somewhat in the flame path. I have changed that and have the burner to the back and flame going across the rear of the chamber. I have kept the burner and exhaust at the same level which keeps the exhaust from coming out in your face as it did with the exhaust in the lower chamber. I did a few experiments with the exhaust into the recuperator through the crown of the furnace. They were easy to build and worked but acted too much like a chimney with the door open. It also seemed harder to realign everything after a pot change, which I do by taking the crown off.
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Old Yesterday, 04:44 PM
Gary Grebus Gary Grebus is offline
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Pete ... what rate schedule is Eversource charging you under? I pay peak demand charges on my bill, but not that extreme.
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Old Today, 07:28 AM
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It's (G) and it's brutal. Eversource is on a tear trying to convert any residential structures to the G status. They don't care if they sell electricity anymore. They charge for delivering it. Nathan here had not really looked at his bill until I started railing about it. Now, he sees it.

I have a 400 AMP Service and they will make the argument that they have to have the capacity to meet my needs at any time.
They also charge for electricity that you fail to use a called "Stranded electricity" Last month the tooling was entirely shut down with only the hot water heater running and it wasn't used for more than a gallon a day. The bill for electricity in that instance was about $50 bucks. Delivering it? $180.00. If I ran a medium size annealer for five days a week, it will go to $600.00
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Old Today, 01:04 PM
John Riepma John Riepma is online now
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If they're not in the insulin or epinephrine sales business they're missing a hell of an opportunity. They already have the business ethics in place.
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