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

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rrnut-2
Posts: 438
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Location: New Hampshire

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

Post by rrnut-2 » Mon Feb 05, 2018 12:21 pm

Heater hoses..nooooooo. That was what I did one night in an emergency on a 5000 lb furnace. We got the furnace cooled down without the power on,
but the next shift didn't listen to what I said. The power was started the next day and within 5 minutes they had a fire...guess where!

You may be okay with feeding the split coil from one end, but only if you increase the thickness of the refractory. The thicker refractory will slow down the heat transfer from the melt to the coil, but you will still have the heat generated by the power going through the coil. I can understand not wanting to buy more furnace leads, they are expensive. You could make your own.

Jim B

rrnut-2
Posts: 438
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Re: One man's insanity---the story of an induction furnace

Post by rrnut-2 » Mon Feb 05, 2018 12:32 pm

https://www.usplastic.com/catalog/item. ... CXEALw_wcB

That's a link to the Nylabrade hose.

Jim B

John Hasler
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Location: Elmwood, Wisconsin

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

Post by John Hasler » Mon Feb 05, 2018 1:20 pm

Is the temperature of the water exiting the coil guaranteed to stay under 175F? These people (among others, no doubt) make reinforced silicone that looks suitable provided that its conductivity is low enough (probably is, but I'd talk to their engineers before ordering). They also have silicone heater hose. If regular heater hose is ok except for the conductivity that might be a more economical choice.

https://www.siliconehose.com/4-ply-wove ... urbo-hose/

I'd feel a lot more comfortable running the hot water out of that coil into hose spec'd to handle boiling antifreeze.

rrnut-2
Posts: 438
Joined: Mon Jul 18, 2011 7:40 pm
Location: New Hampshire

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

Post by rrnut-2 » Mon Feb 05, 2018 2:38 pm

There should be thermostats in the furnace drain lines that are set for a maximum of 185 degs. Don't want to destroy things. The silicone would be more forgiving of small amounts of molten metal hitting them. We covered the hoses on the outside of the furnace shells with silicone covers. The nylabrade worked pretty good, with the next step being non-conductive hose from Inductotherm. The furnace leads used the Inductotherm hose.

Jim B

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

Post by Harold_V » Mon Feb 05, 2018 4:29 pm

John Hasler wrote:
Mon Feb 05, 2018 8:44 am
If I understand correctly the coil is designed to have water supplied at each end and exhausted at the center. You intend to plug off the center and run water in one end and out the other. If you do this you will need to increase the flow rate to match what would have been the flow rate out of that center drain. This will probably double the inlet pressure. It will also move the hot spot from the center, as designed, to the exhaust end.
Thanks for giving me something to ponder.
I suspect there's a good reason why they chose to discharge the water at the center of the coil, and why the smaller coil is double wound. My idea may not work as a result.

What I'd like to do is marry the one box to the legs/tilt mechanism of the other, but they are not physically the same size, although close. I'm going to have to explore the possibility.

It would really be helpful if I had some practical experience with induction furnaces. Jim has proven to be invaluable in that regard.

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

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

Post by Harold_V » Mon Feb 05, 2018 4:54 pm

rrnut-2 wrote:
Mon Feb 05, 2018 2:38 pm
There should be thermostats in the furnace drain lines that are set for a maximum of 185 degs. Don't want to destroy things. The silicone would be more forgiving of small amounts of molten metal hitting them. We covered the hoses on the outside of the furnace shells with silicone covers. The nylabrade worked pretty good, with the next step being non-conductive hose from Inductotherm. The furnace leads used the Inductotherm hose.

Jim B
Take note of the large array of lights/switches on the left hand side of the unit. A pressure switch (which I have shunted for testing) doesn't permit the unit to run if pressure is low, and there's temperature sensors for water and bearings that shut off power if there is overheating. Temperature is set for 190° by default (according to the manual).

Return temperature of cooling water can be determined for each section, as each discharges (individually) to atmosphere on the right hand side of the unit. I'd have to enclose that part if I end up with a closed system, which shouldn't be much of a chore.

I'd like to explore hose options. The Nylobrade appears to be the most economical, but I question the long term life expectancy. Do you have an idea of how long it might serve? It's not real convenient to replace, so it might be a false economy.

In regards to power leads, unfortunately, I have only one, so I will have to buy or make new ones in any case. I was fortunate to find one coiled up inside the power supply. What happened to the other three is anyone's guess, but they, like the legs for the furnace, got separated long before I got involved.

I may be able to make two leads from the one I have. It's much longer than I need, and must undergo repairs, as the connection has been crushed, as if run over by a lift truck. If so, that still leaves me with the need for two more. Fortunately, Ajax provided prints for the leads, so I have a sense of direction.

Your thoughts on the following, please.
A containment pit is suggested, one that could absorb a failed furnace. Volume, in my case, is small, so I have considered a rectangular platform built of concrete block, within which one could put sand. The furnace would mount on top of the platform, an 8" rise.

The shop floor is reinforced concrete, and is 6¼" thick. Rebar, to which my hydronic heating is attached, is on 18" centers, and is in the bottom 2" of the concrete. I suspect I'd want as much distance between the rebar and leads as I can get. I also suspect that so long as the leads run parallel to one another, there is an effective cancelation of induction.

I certainly don't want any molten metal to come in contact with the concrete floor (explosion due to steam), so I expect I'd have to work over a bed of sand where I'd cast.

Of interest, the original legs were made of Jessop steel (austenitic). The furnace Jim provided has legs that are magnetic. I now question how important it would be to use austenitic steel in case I have to end up using the original furnace?

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

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

Post by John Hasler » Mon Feb 05, 2018 7:02 pm

Harold writes:
> I certainly don't want any molten metal to come in contact with the concrete floor (explosion due to steam),
> so I expect I'd have to work over a bed of sand where I'd cast.

That's also an argument against a pit.

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

Post by Harold_V » Tue Feb 06, 2018 2:46 am

Don't know if anyone would be interested, but Patio made a short video of the power supply in operation. This was taken on the first spool-up, when it was operating single phase. Luckily, the set had spun up nearing top speed when the fuse let go.

https://www.youtube.com/watch?v=JIv0MR0vtxc

Today was my weekly trek to the "big city" for provisions. That gave me ample time to think about the differences in how the two furnaces connect to the power supply. It struck me that I can change the way the power supply is plumbed for cooling, so I can hook up both furnaces according to how they are made. It already is capable of connecting two, all I have to do is change how water is connected. A couple diverter valves is all it will take, and seeing as I have to replace all of the cooling hoses anyway, it's no big deal. I will pursue the rebuild of the second furnace with vigor. No reason not to.

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

rrnut-2
Posts: 438
Joined: Mon Jul 18, 2011 7:40 pm
Location: New Hampshire

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

Post by rrnut-2 » Tue Feb 06, 2018 9:43 am

Harold writes:
> I certainly don't want any molten metal to come in contact with the concrete floor (explosion due to steam),
> so I expect I'd have to work over a bed of sand where I'd cast.

I agree, you don't want to let the molten steel hit the floor. And it you have pipes in the floor even more so. Also, foundries usually have a mixture of concrete that is very high in rock content to help prevent floor pitting. So if you don't have that, your floor will pit even faster and more violently.

The steel legs won't be a problem. Just make sure to insulate the stantions from the floor just incase you hit rebar. Also, on the hydraulics, use insulated hoses on the last couple of feet between the steel lines and the cylinders. Remember, on the furnace, NO COMPLETE CIRCUITS anywhere.
The copper coil is the only exception.

On your water system, what you have is what we had for many years. The discharges drained into an open trough, and then into the water system.
This way you can monitor the flows and temps better. Make a tank. The ones that we had were 3ft x 3ft x 4ft. the water trough drains into this.
we had a pump that would pick up from the bottom of the tank and supply the furnace and power supply with cool water (room temp) at 50psi minimum. The pressure line had a mechanical temperatures switch to add cold water (well water) to the tank. The tank had a level switch to make sure the water level was maintained in the tank, excess water went to the brook.

Later on, the tanks converted with another section of tank which collected the "hot" water, and this was sent to a cooling tower, some had heat exchangers. The cooling tower would drain back to the main tank. Keep these tanks covered but the covers should be easy to remove in an emergency, like someone catching fire. Yes, I was there when that happened once.

Jim B

rrnut-2
Posts: 438
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Location: New Hampshire

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

Post by rrnut-2 » Tue Feb 06, 2018 9:46 am

One other note on the furnace, Glyptol is your friend. The oak supports on the coil is insulated with this. Just make sure the oak is dry first.

Jim B

rrnut-2
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Location: New Hampshire

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

Post by rrnut-2 » Tue Feb 06, 2018 12:02 pm

"Remember, on the furnace, NO COMPLETE CIRCUITS anywhere." This also includes jewelry, no rings, no necklaces, no bling! If you forget the wedding ring around the furnace, I will guarantee that you will not be able to find water fast enough!

Jim B

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

Post by Harold_V » Tue Feb 06, 2018 5:10 pm

rrnut-2 wrote:
Tue Feb 06, 2018 9:43 am
The steel legs won't be a problem. Just make sure to insulate the stantions from the floor just incase you hit rebar. Also, on the hydraulics, use insulated hoses on the last couple of feet between the steel lines and the cylinders. Remember, on the furnace, NO COMPLETE CIRCUITS anywhere.
The copper coil is the only exception.
I took note of the extensive isolation (via the use of mica) of the framework of the original furnace. I managed to save the majority of the mica pieces, and have an asbestos product with which I'll be able to make the few small bushings and/or spacers as required. I see this as much the same thing as avoiding what might be considered ground loops.
, some had heat exchangers.
Right now, that's the school of thought I'm entertaining.
Keep these tanks covered but the covers should be easy to remove in an emergency, like someone catching fire. Yes, I was there when that happened once.
A horrifying thought, but one must be prepared for the worst possible scenario.
One other note on the furnace, Glyptol is your friend. The oak supports on the coil is insulated with this. Just make sure the oak is dry first.
I was advised by Ajax "The coil should be insulated with a Class F insulating varnish." In this instance, the coil supports are made of maple, and they were so covered after being cleaned up.
"Remember, on the furnace, NO COMPLETE CIRCUITS anywhere." This also includes jewelry, no rings, no necklaces, no bling! If you forget the wedding ring around the furnace, I will guarantee that you will not be able to find water fast enough!
I can't tell you how much your guidance is appreciated. Dealing with this has been a real challenge, one I have thoroughly enjoyed, but you have made the task much easier, for which I will be eternally grateful.

Please give Liz a hug for us. She's a remarkable woman!

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

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