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Old 11-29-2018, 08:36 PM
Josh Bernbaum Josh Bernbaum is offline
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Nursing moly through power outage

Just had the privilege of my first over-8-hour power outage here since I've had a moly furnace here for 8+ years. It was 27 hours total, big ass tree took out some lines on my road on Tuesday morning. Power came back on yesterday, but there are still some folks without power here in VT after that last storm of heavy, wet snow and wind. Got a chance to use the "crash cart" I built for the first time. I wheeled it up to the furnace with temp at 1600F, and the venturi and gas flow on a low-ish setting got the temp up to 1900 over 20 hours or so. I have no experience with venturis on furnaces, and after I thought it was working properly for a half hour or so, I went next door to later discover it started backfiring and it smelled really bad when I got back over there. (was the paint on the venturi heating up too much) So after increasing gas and air intake a bit it seemed to run fine into the next day. Only went through about 1.5 20# propane tanks in the 20hrs, thought it'd be more for some reason. Glad I happened to have two full tanks at the time. Still slept over there in the shop Tues. night just in case, because I'm a nervous nelly with no safety on a gas burner. It'd still be great to find a way for a moly system to not eat generator motors though, but at least this seemed to do okay with using the cart. Trying to attach a photo of it here.
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Old 11-29-2018, 11:33 PM
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Scott Dunahee Scott Dunahee is offline
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I think it is awesome you built a crash cart before you needed it. Awesome.

Cheers.

I made it through some ugly equipment malfunctions with a trusty venturi burner.

BSD
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Old 11-30-2018, 07:58 AM
John Riepma John Riepma is online now
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That looks like a terrific solution Scott! Much better and quicker to implement than what I had planned for my next outage. In order for me to plagiarize it properly could you provide the part numbers for your venturi and burner? And just curious, but with a power outage how were you able to tell the temperature?

For anyone else like me that does not have telephone service to their studio or whose phone service fails in power outages, this is a device that I got to tell me when the power is out at my studio 25 miles from my home:
https://store.pumpalarm.com/alarm-device-p/s-pb-std.htm
The unit initially cost about $200 but was much cheaper than having cable cellular service pulled in and paying monthly bills. It has a prepaid cell phone or something like that inside it that will send a text to up to 3 numbers when the power goes out and also when it's restored. The restoration text prevents me from overreacting to minor outages that only last a couple of hours.
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Old 11-30-2018, 08:22 AM
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Pete VanderLaan Pete VanderLaan is offline
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The trouble with the moly and the crash cart is that there is no flue. I don't think what you show in the photo is sufficient. FDurther Gibberson heads on venturis do slow flow down. If I was doing what you are doing ( and I have), I'd bring the venturi in thru the clean out, crack the door and plug most of that with fiber but leave space for exhaust. '

The thing about gas is that it expands on combustion and where the venturi may seem settled initially, the internal pressure of the furnace continues to change as it regains stasis. Burn back in tubes on gas equipment is inevitably a velocity issue. The combustion gas needs to go somewhere.
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Old 11-30-2018, 09:36 AM
Josh Bernbaum Josh Bernbaum is offline
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I do have an exhaust hole in that crash cart's door Pete. I plugged it about half way with frax, but it could be opened even further. Exhaust gasses were exiting there, I could feel it with my hand, and see it until I adjusted the air up till the lick of flame coming out went away. Perhaps it's not an ideal spot, but I do think the gasses are finding that for their escape. I did remove a bit of the frax after that backfire issue, perhaps that helped free up the flow a bit.

John, that Venturi system I bought from Dudley Gibberson in NH. I think I saw after I got mine that he was selling an even smaller one which would have been nice. And I can see the temp readout on my controller during outages because I did spend the cash a few years ago to put in a propane generator with an auto transfer switch. Which has been awesome, except it can't run my electric furnace. Runs just about everything else in the shop tho.
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Last edited by Josh Bernbaum; 11-30-2018 at 09:37 AM. Reason: Got a name wrong
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Old 11-30-2018, 10:01 AM
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Pete VanderLaan Pete VanderLaan is offline
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I saw the hole, I just don't think it's adequate. expanding gasses make for increasing pressure as the burner is turned up. Venturis don't do well in that kind of environment. I hate sleeping in the shop. Too many mice.

Mark Peiser fires his entire furnace on a venturi and never goes beyond 2280F.
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Old 12-01-2018, 10:02 AM
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Franklin Sankar Franklin Sankar is offline
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Will the gas interact with the elements?
I canít remember but if you do this for wire elements and go up to 2280 will it melt the wires?
Franklin
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Old 12-01-2018, 12:19 PM
Josh Bernbaum Josh Bernbaum is offline
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I'd like to know more about how elements do in a flame environment also. Specifically moly in my case. I've begun a conversation with Cheyenne Malcolm about designing a hybrid furnace, one which would run on moly elements for idle/working out of, and have a gas/forced air burner for melting and power outages. And some sort of flue that could be plugged or maybe the door just gets cracked open during gas operation. Maybe the burner would have to be easily removable too, not sure if it would overheat not having forced air going thru it when not in use. I don't know if this is possible, and neither does Cheyenne, but we are starting to think about it anyway. I'd love to be able to do melts with gas and then switch back to electric. Rate-wise, for me in the northeast it's a wash, it's all expensive, propane or electric. Cheyenne thinks that testing will need to be done to answer some questions about the durability of the elements in that environment, and sounds like testing, in itself, would be expensive before building the final furnace. I'm sure this idea will be quickly dismissed by some, but I've been intrigued for some time if it might be a possibility.
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Old 12-01-2018, 03:01 PM
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Pete VanderLaan Pete VanderLaan is offline
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Steve did/does have information on that and hopefully he will chime in. I recall his greatest concern was having the elements parked anywhere around 700F but that could be wrong.

The conflict I see is needing the flue and burner porting. Moly really needs to be buttoned up tight or it performs poorly. Way back, Steve tried putting a small flue on Mongrain's furnace and it would not make temperature at all.
All of this cullet coming our way via Europe is using the same methodology for melt performance and that's barium/boron. GLASMA 704 doesn't even have Alumina in it if the specs are to be believed. After Spectrum, one would think that it was to be avoided but the Europeans use different refractories than we do here. I don't see the refractories changing since greenware clay is a bridge too far for American studios. It changes the superstructure as well.
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Old 12-02-2018, 12:21 AM
Max Epstein Max Epstein is offline
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Quote:
Originally Posted by Pete VanderLaan View Post
Steve did/does have information on that and hopefully he will chime in. I recall his greatest concern was having the elements parked anywhere around 700F but that could be wrong.

The conflict I see is needing the flue and burner porting. Moly really needs to be buttoned up tight or it performs poorly. Way back, Steve tried putting a small flue on Mongrain's furnace and it would not make temperature at all.
All of this cullet coming our way via Europe is using the same methodology for melt performance and that's barium/boron. GLASMA 704 doesn't even have Alumina in it if the specs are to be believed. After Spectrum, one would think that it was to be avoided but the Europeans use different refractories than we do here. I don't see the refractories changing since greenware clay is a bridge too far for American studios. It changes the superstructure as well.
So... how do you build a "european" furnace? To resist the boron content?
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Old 12-02-2018, 08:34 AM
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The refractories are different materials. They utilize AZS and the use of pure silica brick is common for superstructure. The crucibles are different compositions utilizing clays instead of coarse grained alumina. They accommodate junky low melt glasses somewhat better. It isn't necessarily better, it's just different. Spruce Pine accommodates alumina refractories really well. Spectrum didn't . One takes higher melt temps. People seem to want good melts from a crock pot.
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Old 12-02-2018, 10:24 AM
Kenny Pieper Kenny Pieper is offline
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Quote:
Originally Posted by Josh Bernbaum View Post
I'd like to know more about how elements do in a flame environment also. Specifically moly in my case. I've begun a conversation with Cheyenne Malcolm about designing a hybrid furnace, one which would run on moly elements for idle/working out of, and have a gas/forced air burner for melting and power outages. And some sort of flue that could be plugged or maybe the door just gets cracked open during gas operation. Maybe the burner would have to be easily removable too, not sure if it would overheat not having forced air going thru it when not in use. I don't know if this is possible, and neither does Cheyenne, but we are starting to think about it anyway. I'd love to be able to do melts with gas and then switch back to electric. Rate-wise, for me in the northeast it's a wash, it's all expensive, propane or electric. Cheyenne thinks that testing will need to be done to answer some questions about the durability of the elements in that environment, and sounds like testing, in itself, would be expensive before building the final furnace. I'm sure this idea will be quickly dismissed by some, but I've been intrigued for some time if it might be a possibility.

I would get in touch with Dirk Valkema. A decade ago he was doing some hybrid furnaces. I don't know if he is still making them but Im sure he would have some info for you.
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