Moly Furnace

A couple questions from an amateur. What's the thing dangling down inside the furnace that appears dark? Is it an element? Why "moly?" What purpose does the restrictor serve? Keep the door from slamming open?

Nice to see a post that's about glass....

Mike Beede

Hey Mike yeah that's an element. There are four in a semicircle. Molybdenum disilicide furnaces are state of the art glass melters. A real revolution in glass furnaces. Because, they are virtually impervious to glass attack from most soda lime batches, can easily handle temps in excess of anything we'd need, and can cycle indefinately--they have an undetermined (read long) lifespan.

But there are some caveats. Electrically they are not plug&play. The operating voltage varies with the size of both the hot&cold zones, and element resistance changes dramatically with temperature. Generally they run on high amperages at low voltages. To make this power you need to use a large heavy transformer. To compensate for the extremely low cold resistance, you need a current limiting scr.

Also, they are extremely fragile when cold.

Right the exhaust restrictor adjusts the speed and power of the cylinder. Its an elegant solution; they sell lots of speed/airflow restrictors for the incoming side, but they really don't work that well. Plus, the restrictor is just a few bucks.

I can look it up later today when I have time. If you want, go to ec21.com and search "Songshan". Also, These guys were not the least expensive bidder. I contacted another Chinese company that was actually

1/3 cheaper. But they didn't have the track record, so I went with Songshan.

Okay I had to go through my inbox--

snipped-for-privacy@songshangroup.com Contact is Mr.Yang Xuehao

Chida

snipped-for-privacy@chida.info Contact is Andy

Chinese suppliers ROCK.

Great thanks for the info. I found them yesterday with your previous info. Shame they don't have the tech info in a PDF format that I can find. The tech info on their site doesn't display properly in my browser, the images are squashed vertically. I shall go and have a look at the Kanthal site.

I am currently build>Okay I had to go through my inbox--

Okay you need to get the Kanthal Super Handbook. Its put out by kanthal and they'll send it to you for free. In fact, they sent me two for some reason. It is an incredible resource. It shows you how to install the elements, pitfalls, and a whole table of voltages/corresponding to cold and hot zone dimensions. Basically all these elements have the same specs regardless of manufacturer. So you can use this info for I2R elements, Kanthal, or the Chinese ones. By that I mean, dimension for dimension the voltages will be the same or very similar. Good luck and let me know if I can help.

Lots of info,

Jack Imo the Sinotte article and Henry's article really aren't useful from a technical standpoint. For one thing, both these guys sell furnaces, so you get into the issue of polluted information. But in Henry's case its just an introduction, an overview of Moly. In Sinotte's case its just not accurate information. For example, there is no way he could have any idea wether the Chinese elements are inferior. He's just playing on that same old racist stereotype that pervades the glass community and for that matter, America right now.

I read that Sinotte article a few months ago. I actually was going to get some electroglass pellets to try out, but after I read that I felt like he wasn't an honest guy and I never got the pellets. Electroglass furnaces use Sic elements, and apparently he'd rather try and stick it out with sic than change. But if you ask ANY objective expert--for example, the folks at I2R who sell both--they'll tell you moly is the way to go. And since sic burns out and Moly doesn't and since when sic goes you have to replace the whole bundle and not just one element (sic element resistance changes over time and moly doesn't) it is certainly NOT in their financial interest to recomend moly.

Personally, I've been using wire elements for years on the theory that moly was too complicated. Sinotte certainly has his finger on the pulse of the glass community in that sense. People are freaked out by the electrical requirements. But I'm here to tell you that it is actually LESS complicated than wire--by a great deal. The only thing that is more complicated is the transformer but once that light goes on in your head, you'll wonder what the big deal was. That's the way it was for me. Also, its less complicated than sic, though I've never run a sic furnace. But you have all kinds of issues of glass attack, changing resistance, and element placement and longevity with sic to deal with that you don't have with moly. And really, the only part you need in a moly system that you don't have with sic is the transformer. Some guys run them with ssr's instead of scr's but basically the difference is minimal. So, in short I really think Sinotte is full of crap.

Notice I supplied a link to Moly furnaces. I have no ax to grind either way. You OTOH, you have a Moly furnace and can do us all a service by keeping us informed of the performance. I'm only interested in power consumption, life of elements, and original cost. What *did* that one cost to build anyway? I have a friend who is trying to decide between SiC and Moly. He called me this morning to troubleshoot his wire furnace. We lost the top of three banks so he spent the day blowing 150 pounds of glass so we can install new elements. I think we can both agree, the only thing worse than a wire furnace is no furnace at all.

Claiming the Chinese element is inferior is a matter of opinion, and a sales tactic. But racist? Give your head a shake, David.

We have no qualms about using Chinese rods. If they prove to be inferior, we'll move on.

I think he's tired of changing elements so any info you can give on the design would be appreciated. I speak math and electrical pretty well.

The Kanthal website is a nightmare. Can you give more details on getting this book?

You can order it from the Kanthal site, I do remember having to slog through alot of density on their site, but its there. I also got an introductory letter with the handbook which I may not have thrown away, I'll try and dig around for it.

I guess the basic point I was trying to stress in the last post was--I've been following the discussions of moly furnaces very keenly for several years, and reading all I could on the subject including all that stuff you posted. In fact I have had the parts from Stadelman for nearly three years, so I've had a real incentive. But nothing really de-mystrified the situation for me until I read the handbook. I mean, I understood the principles mostly, but not well enough to build the thing myself. That handbook is just, like I said an incredible boon to anyone wanting to do this. Its a gift.

Looks like i'll have to get the Kanthal Super manual on order, I downloaded a brochure which gives an overview but one link to a manual was dead.

From my point of view wire elements are the cheapest to make and control, low aging at about 6% increase is easily worked with, they can be designed to work directly off 230V supply, and the calculations relating to the design are quite simple although I say that as a mechanical engineer. As an occasional glassblower I may not want to go to the expense of the moly but I may now look further into it though and at least get a quote on elements.

The main issue I see with moly is the requirement for a low voltage high current power supply which while not necessarilly complicated may be expensive, at the moment my oil cooled welder springs to mind with 3 or

4 elements >Jack Imo the Sinotte article and Henry's article really aren't useful

The way I see these threads on google is really confusing. It seems like everything is mixed up chronologically. Anyway...

Jack about the Chinese, I do believe the situation today, where American manufacturers claim Chinese products (a country of over 1 billion and a huge diverse economy) are universally inferior, is racist. Saying all products made by one race or nation are inferior, is racist. And, its moronic. Think about how huge China is. How many companies there are, in all the cities and provinces. All the different employees, supply situations, expertise, markets, etc. Then realize how stupid it is to make such a blanket statement. As for Sinotte, he is playing on this. He says Chinese elements are inferior, and we all nod knowingly. But there is no POSSIBLE way he could make that statement with the benefit of evidence without expensive testing. In some cases, like moly elements, the matertials and workmanship fabrication costs just don't lend themselves to cost cutting.

So, enough on that.

Basically with the power, you work with what is conveniant. That turns out to be 30 or 60 volts. Its conveniant because they make 4 to 1 stepdown transformers for industrial office buildings to take 480v down to 120v. These are really not that expensive. for a 25kva I think its like 500 bucks new. So. If you put 240 in the primary, you get out two

30v legs. Okay, so you've got 60v. Now you need to decide how much oomph you need for your furnace. In my case, I put together four 15v elements in series, for 60v and a total draw in the primary of 42a @240. For a larger furnace, you'd want to go bigger. Por ejemple 3 20v elements in series. Or, start putting bundles in paralell. The Kanthal handbook has all those tables.

Once you have that figured out, just make sure you have a current limit on your scr, so you can hold the whole thing back while it gets up to temp.

Ps. what is your friend running as far as configuration with the wire? Maybe I can help. Also, its not all that hard to convert wire over.

When you lose a bank with wire you have some choices to make. You need to determine which elements in that bank are stil good. If its the first bank you've lost, you can hold those elements out and use them as spares when you lose the next bank. One thing you obviously don't wan't to do is run uneven banks.

Use of google may explain why your reply is off my post rather than Jacks. Maybe the view as tree option at the top of the page would help.

For me in the UK that type of transformer is not commonly available to my knowledge as we use 230V for domestic electric with 13A being a standard socket, 30A is common supply for cookers, and 45A and 60A for electric showers. I will ask an electrician I know though and see what he says about that sort of transformer.

Are you us>Ps. what is your friend running as far as configuration with the wire?

Right, plus the book has pictures, which are helpful to a guy like me.

You want to use the scr on the line side of the transformer, i.e. the primary side. I guess that's upstream. The reason is, on the load side you'll be dealing with that high amperage which will require heavier more expensive switching. Also you want to have your safety relay (I use an mdr) on the line side, which circuit will be run through your door kill and second overtemp/safety controller.

Really, I put the panel meter on the primary side and can easily forget that I am dealing with esoteric voltages. The panel meter reads from

0-50 amps, and so I can see what I am really drawing in house current.

But when you get to the UK, all bets are off. There was a guy recently on the warmglass board who actually gave some very dangerous electrical advice. Normal for the US, but dangerous for the U.K. As I understand it, your high voltage 230 is not two hot legs as it is in the US, but one hot leg and a neutral, as is our 120v. I once had a neighbor who would always say you are taking your life in your hands to change a lightbulb in europe.

What is "moronic" is using a inflamatory word to describe an unsubstantiated business practice by (how many, exactly?) American manufacturers.

The word RACISM means:

a.. noun: the prejudice that members of one race are intrinsically superior to another.

By definition, then, selection of one product over another cannot be "racist", because inaniminate products are not members of a "race".

I absolutely DEFY you to cite one instance anywhere when ANY "American manufacturer(s) claim Chinese products (a country of over 1 billion and a huge diverse economy) are universally inferior". This is a broad, sweeping, totally unsupportable claim. Making you, in all probability, nothing more than a liar.

Find me just ONE such verbatim claim...by any one American manufacturer (in any industry) that makes a claim that "all" Chinese products are inferior.

Your claim that some obscure author in some obscure book about some obscure technology dismisses products from the Pacific Rim as inferior does not locically extend to ALL of American industry. You cannot take one author's opinion (probably misquoted by yourself) about the suitability of a product for an application and transform that intrepretation into some geo-political conspiracy. Well, I guess YOU can.

Normal people would just go on about their business.

Please go take your meds now. And try to refrain from displaying your ignorance of the English language.

I was thinking some more about this David. You can use any smallish voltage that is easily available to you. You just need to pick and configure your elements appropriately. For example if you have a single pole 230v, you could still probably use this step down transformer to get to 57.5v, single pole. I'm just speculating; ask your uk guy. The thing is though, these elements need to run on 170 amps. So if you don't use a stepdown transformer, you may have to use a high amperage primary circuit, which is a drag, and lots more expensive. And you'll use a big chunk of your service. That's because the 4-1 stepdown transformer bumps up the amperage in proportion to taking down the voltage. So when I put in 50a @ 240 in the primary, I get 200a @ 60v out in the secondary. So I only have to use a 50a breaker, small scr, small safety relay, etc.