One man's insanity---the story of an induction furnace

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Harold_V
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One man's insanity---the story of an induction furnace

Post by Harold_V » Tue Jun 20, 2017 1:47 am

I have long desired to be able to cast iron, with ductile iron being a priority. To that end, I kept my eyes open for an induction furnace, which is the simplest way to melt such an alloy. A cupola can be used, but sulfur content of the iron must be quite low, otherwise the inoculation process that makes ductile iron isn't successful. You end up with gray iron instead. Acquiring coke of any description has become difficult, with the low sulfur requirement making it all the more difficult. Sulfur can be removed from molten iron by dribbling calcium carbide to the molten mass. It combines with sulfur and can be skimmed, but obtaining carbide, these days, is not an easy task, nor is it financially viable.

While living in Utah, I kept tabs on Utah State Surplus. In exploring their yard, I discovered an induction furnace, legs missing, and no power supply. The story is long, but in time it became mine. Now all I needed was a power supply. There's more to the story about the furnace and legs, which I'll add at a later date.

There was a surplus electrical supply house in town, one which I had frequented when building various projects, including the 30 amp rectifier I used to use in refining silver. I happened by one day and was talking with Norm, the owner. I asked him if he ever encountered induction furnaces. He replied that he indeed had, and, in fact, had one in his yard as we spoke. Imagine my surprise to discover the power supply was the one that went missing for the furnace I had procured. It was an Ajax Magnethermic 50 kW motor generator supply, three phase 208 volt input, single phase 3,000 Hz 400 volt output. The power supply and furnace were each marked with the same auction numbers and were listed as items 1 of 2 and 2 of 2. The power supply was marked with a large red cross, which I didn't understand at the time.

I was keenly aware that these old power supplies were equipped with capacitors that were PCB filled, and that if they were leaking, it was required that they be scrapped through legal channels. Before striking a deal with Norm, I inquired of Ajax Magnethermic to determine the original owners of the furnace, and they were most helpful. Turns out it was purchased and used by the Bureau of Mines, in Salt Lake City.

Armed with the knowledge that the BOM once owned the machine, I inquired of them if they could help me in disposal of the caps. They disclosed that it should not have been sold (which explained the large red X), and been intended to be scrapped due to the PCB's enclosed. The state said a mix-up had occurred and it was auctioned, with Norm being the successful bidder.

The BOM considered my request, and after a three week wait I was informed that they would pay for disposal of the caps. I was to procure a proper container, in which the caps would be placed and shipped to a PCB disposal facility. That sealed the deal, and Norm and I confirmed the purchase.

Because the power supply had been stored outside for at least two years, the meters were trashed, so they were removed for rebuild. I also discussed them with Ajax, who provided me with meters that could be rebuilt, shipped to me at no charge. Long story short, I have four meters waiting to be installed, and I found a firm in the south that would build new capacitors, PCB free. They, too, are awaiting assembly.

That brings me to today, about 22 years after I acquired the power supply. I had intended to just get it running, but the prolonged sitting out of doors in Utah winters had created considerable rusting, with which I have great difficulty dealing. I hate rust and don't tolerate it well. I have begun the process of scraping the exterior, which will be followed by treatment with phosphoric acid, then a decent spray paint job. Once done, the power supply will be assembled and wired, then the fun of testing will begin. I am honored to have the assistance of Patio, who is a licensed electrician with an administrator's certificate. Between us, I expect that we should be able to solve a huge number of issues that are sure to rise to the top.
Here's a picture of the power supply as it sat Sunday evening, June 18, 2017.
Ajax power supply.jpg
I still have to remove several switches and indicator lights, as well as some door hardware. I will leave the interior intact, as much as possible. It's not very pretty inside, but one doesn't have to look there in order to operate the machine. I'm simply going to try to live with a good cleanup, as removing the contents would be an insurmountable chore for me, especially considering the unit weighs right at three tons, with the motor/generator comprising the vast majority of the weight.

Of interest, the motor/generator mounts vertically, sharing a common shaft. Here's a picture.
Motor generator.jpg
For those who don't know, units such as this are all water cooled, including the caps and buss bars, as well as the furnace proper. A water cooled shroud surrounds the motor/generator, with water circulating through the caps to keep them cool. I'm amazed at the engineering that was involved in building such a simple, yet complex, device.

If anyone cares to see how it looked when it was discovered, I have an old photo, but I am unable to use my scanner, thanks to no driver being available. Patio has offered to scan a few pics for me, which I will have him do in the near future.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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Atkinson_Railroad
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Re: One man's insanity---the story of an induction furnace

Post by Atkinson_Railroad » Tue Jun 20, 2017 4:50 am

Harold;

Where there’s a will, there’s a way. You’re not insane. Maybe an “Industrious Passionate”?

The motor generator being the heart of the power supply should be inspected and considered for recondition.
Because it’s of vertical design, the bearing fits are likely still in good condition, “but” the bearings should be
replaced noting that the unit has sat dormant and outside for the length of time you’ve reported.
A competent electrical apparatus repair shop could perform the work best because they would also be able
to confirm the integrity of the winding(s) insulation. From your photo, one of two lifting eyes can be seen
indicating the unit is possibly removed through the top of the cabinet.

Definitely a fun looking project. Do you have access to an operator’s manual for the power supply?

John

tornitore45
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Re: One man's insanity---the story of an induction furnace

Post by tornitore45 » Tue Jun 20, 2017 7:06 am

What a story of passion and determination. My question: what you plan to do with ingots of malleable iron?
Mauro Gaetano
in Austin TX

John Hasler
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Re: One man's insanity---the story of an induction furnace

Post by John Hasler » Tue Jun 20, 2017 7:49 am

So the capacitors were leaking?

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NP317
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Re: One man's insanity---the story of an induction furnace

Post by NP317 » Tue Jun 20, 2017 9:15 am

Wow! Quite a project. I hope to read of your success very soon.

While in charge of the Student Teaching Shops at the University of Washington Mechanical Engineering College (Seattle), I inherited an excellent working induction furnace in the small foundry. The power supply (refrigerator-sized) was a water-cooled solid-state rectified 440V 3-phase unit. I had to replace the large water-cooled diodes once (expensive!), but it served us well for 12 years.

When I visited the Shop last year, the foundry was gone. I learned that the furnace power supply had quit working, so the entire system was sent to the UW surplus. My replacement Manager did not have the capabilities to trouble-shoot and repair the power supply. It has all been replaced with more CNC machining centers, and a large heat treatment oven.
Anyway, I wonder where that furnace and power supply ended up???
~RN

John Hasler
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Re: One man's insanity---the story of an induction furnace

Post by John Hasler » Tue Jun 20, 2017 9:25 am

Do you have schematics? I'd be interested seeing the design.

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SteveHGraham
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Re: One man's insanity---the story of an induction furnace

Post by SteveHGraham » Tue Jun 20, 2017 9:56 am

That's really neat. Not ready to quibble about the "insane" part, however.
Every hard-fried egg began life sunny-side up.

rrnut-2
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Re: One man's insanity---the story of an induction furnace

Post by rrnut-2 » Tue Jun 20, 2017 10:33 am

Harold, It's looking good! Does the unit have a closed water cooling system internally? If it does, make sure that you use only distilled water in it.
Also, it will have a deionized water filter which will need to be changed before you put the distilled water in. Normally, we would check the conductivity with a micromoh meter.

Motor bearings I wouldn't get to worried about unless they saw water. Once you bump the motor to check direction, you will be able to tell their condition.

Make sure the capacitor contactor contacts are clean and free. If they are not, they tend to burn up quickly. Make sure all connections to the furnace are tight. Again, if they are not, they will burn quickly. It's amazing what can happen around an induction furnace!

Jim B

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ctwo
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Re: One man's insanity---the story of an induction furnace

Post by ctwo » Tue Jun 20, 2017 10:55 am

If you have a cell phone, you can usually get a decent "scan" by taking a photo, of a photo. Sounds crazy?
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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SteveM
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Re: One man's insanity---the story of an induction furnace

Post by SteveM » Tue Jun 20, 2017 11:05 am

ctwo wrote:If you have a cell phone, you can usually get a decent "scan" by taking a photo, of a photo. Sounds crazy?
I do that all the time.

I guess the fact that I'm crazy helps.

Steve

tornitore45
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Re: One man's insanity---the story of an induction furnace

Post by tornitore45 » Tue Jun 20, 2017 12:55 pm

My replacement Manager did not have the capabilities to trouble-shoot and repair the power supply.
Is not difficult to find highly technical help at an engineering university.
Mauro Gaetano
in Austin TX

Patio
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Re: One man's insanity---the story of an induction furnace

Post by Patio » Tue Jun 20, 2017 11:13 pm

Harold, I am glad you have decided to post pictures this adventure. :)
Live for the moment!
Prepare for tomorrow!
Forgive the past!

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