Resurrection of a CFEI 100 KVA Induction Furnace

[modeng200023]

Andrew, I have not noticed you saying how much melt you can produce at a time.
I'm following your progress with much interest.

John

[awemawson]

John,

It's an odd thing but I was sure that I'd replaced crucibles in both furnace bodies with new ones both of the same size, however in trying to answer your question I see that in fact the tilting one has a much larger crucible than the inverting one. I have the original box on the shelf from 2006 in which they were delivered (to my place in Bromley) as I had to order several at the time. I will have to open it up and see if in fact I ordered two sizes, or if my memory is playing up and perhaps I only replaced one 


. . . . old age is a dreadful thing 

[awemawson]

Well I'm not cracking up after all, I DID replace both crucibles. I obviously bought four of each size and still have three of each size remaining.

See pictures for sizes

[awemawson]

Yesterday I managed to get the cast concrete slab onto the Pump House as a roof. This has been cast with a 1"  fall from front to rear to shed the rain. Sadly I managed to chip one corner but never mind, it's no great issue.

Having the lid on allowed me to fit the 80 watt tubular heater that on it's lowest thermostat setting is supposed to be proof against frost - handily this had just been delivered so could go straight in. I knew when I ordered it that is was going to be a tight fit - it's the same length as the inner rear wall to within a millimetre and JUST fits - phew !

[awemawson]

Today's task was to complete the ring main in the foundry. The roof leak is still present and will be until the weather improves and we can work on it, so I took the cowards way out and re-located the final double socket out of the drip zone  This involved threading cables and fitting girder cable clips in odd inaccessible places and took longer than it should have, but come lunch time it was finished and tested, allowing me to finally close up the sub-panel and label it's various ways.

Conveniently over lunch Hermes delivered a 125 amp three phase 'free socket' that I won on eBay. I wanted this so as to be able to power up the furnace driver (at low power) off local mains for testing rather than rolling out the long heavy cables and starting the generator. I had worked on the two issues I've had preventing it going 'Pret' (ready) and wanted to prove that I'd fixed them - I had 

So now is the time to pull everything apart for painting. The paint (hammer finish light blue) is the same paint that I sprayed the generator with, and also the electrical enclosure for the new chiller unit. Although obviously it's not an exact match for the original, it's actually not a million miles off. I will try to spray it in such a way as to form minimal hammer effect (high pressure, light coats, don't wet out surfaces fully). It's a pretty tough forgiving paint that covers many blemishes and oh boy will it have to ! (paint and thinners also arrived yesterday)

I now need to devise the easiest way to drain down and disconnect the four hose / cables to the furnace body and two hose to the chiller, and also the inner passageways of the Furnace Driver with minimum loss onto the floor and maximum retention of the expensive glycol solution. I have in mind to sacrifice my 'Clean' wet & dry vac to this purpose. It's supposed to be reserved for vacuum hold down fixtures on the CNC mill - I supopose if it suffers they are not THAT expensive. My (identical) workshop vac is disgustingly filthy and any liquid recovered using it wouldn't be worth saving !

Doing an inventory of the rusty bits just now and making a photographic record they are quite extensive  - all external surfaces need doing but amazingly the internal surfaces have faired far better - the door and panel seals must have done a good job of keeping the moisture out.

I must admit I'm not looking forward to this bit of the project. It wasn't worth doing before I'd proved that the unit worked, and now I know that it does I'm loath to take it apart, but if it's not done now it never will be, and those rust spots will become far more of a problem to deal with.

The plan is to remove the six castors from the base frame, sit it on it's adjustable feet and move it about with the pallet jack. (I fitted the six castors at my last place as there was no room to get the pallet jack at it, and four castor weren't rated for the weight !)

[awemawson]

In a flash of inspiration in the early hours of last night I remembered that I had a Numatic car valeting wet & dry vac tucked away on a shelf in my container that I had bought off eBay 'as it looked useful'. I think that it's only been used once by a friend who had had a smashed windscreen and cubes of safety glass everywhere.

Emptying the glass (!!) and washing out the innards and hose it was eminently suitable for sucking up the coolant as it escaped as I undid various plumbing fittings. In the end I managed to  're-cycle' three gallons of coolant, which I passed through a fine mesh filter. So not only is that three gallons of not inexpensive coolant saved, it's three gallons NOT on the floor to mop up 

Applying the vacuum hose to the two large flow and return ports on the furnace driver effectively sucked out not only the inner workings of the driver unit, but also the hose / cable assemblies leading to the furnace body. This made undoing them easy as coolant wasn't splashing everywhere (as it has in the past!)

So that's Phase One completed

Next - Phase Two, remove the castors . . .

[nrml]

It's a bit late to be of any use now, but wouldn't one of those air driven venturi vaccum coolant filling devices been ideal to just suck it all out from a low point in the circuit without any mess at all? With all the coolant and various other fluids you use across your workshop, you could do with one of those. They are pretty cheap these days.

[Pete.]

I have one of those Numatic vacs as a shop vac for swarf and general dirt. They are fantastic for both wet and dry. They do single and twin-motor variants.

[awemawson]

A good solution, thank you, but the Numatic actually worked quite well. I had one of those venturi coolant mixers but I sent it back and got my money refunded, as the mixing ratio quoted was miles off what I could measure with my Brix gauges

So Phase Two starts :-

Firstly the six castors. It seems that I'd drilled and tapped to fit them, so getting them off was easy with no struggling to reach nuts - probably why I did it that way!

Then I removed all external labels, door furniture, operating handles, locks, catches, captive bolts etc. Then for the operating panel. This is not an 'unplug' job - some is but most is hard wired. I worked out that there was just enough cable length to remove it from the front door, and fold it back into the cabinet. I wrapped it in bubble wrap, and as luck would have it the 3 phase sub-panel cardboard box was just the right size to secure it in, and tie it with the ubiquitous baler twine.

The main input 125 amp socket I knew was going to be an issue to remove. Held on by four M6 bolts into thread inserts, but one had cross threaded and pulled the insert out of the panel, and getting to he rear was pretty impossible being more than I could reach through the internal electronics from the other side. There was JUST room to grip it in a Mole Grip, closing it with the tips of my fingers. Mole grips tethered with another bit of baler twine, as when (if) the screw comes out the Mole Grips will plunge into more inaccessible space below. However a quick application of the rattle gun to the bolt head working against the inertia of the mole grips got it off, and as expected they went crashing into the depths but was able to be pulled out by string.

So I think that's Phase Two completed 

Major paint stripping and rubbing down next. I think that I will swathe the internals in dust sheets - do all the stripping and rubbing down, then remove the dust sheets and mask up properly before spraying.

I'm in two minds how to handle the doors. As they are at the moment they would just lift off their hinge pins, and that would make preparation of the frame somewhat easier, and preparation of the bottom edge of the doors would be a lot easier. I may lift them off, prepare them and the frame, spray the frame then re-hang the doors for spraying. Not decided . . 

[awemawson]

So - Phase Three: Prepare for Spraying.

This morning I went over all surfaces with a rotary wire brush removing loose paint and rust. This helps to reveal and take off bits of loose paint that superficially appear sound but actually are separated from the base metal. It also saves the stripping disk (which is the next process) - also rotary wire brushes last longer and are cheaper !

The wire brush leaves a harsh step between the remaining sound paintwork and the base metal, whereas the stripping disk (if used gently) allows you to blend the junction.

So four sides and the top took about an hour so I was finished by 9 am and came in for my fingers to stop tingling from the angle grinder and have a coffee. Hopefully using the stripping disk wont take much longer, though it does need gentler application.

[awemawson]

So to complete Phase Three took one and a half stripper disks and as expected took a bit over and hour for the stripping and about as long again to mask up for spraying.

I liken masking with paper to hanging the cheapest wall paper that you've soaked too long in paste - it tears at the first excuse!

Covering up the innards took a bit of taping ingenuity as of course you cannot get to where you need to put the masking tape - never mind I got there in the end - not the most robust, indeed I had to drop the roller shutter as the slight breeze threatened to blow it all off.

So Phase Three completed 

[awemawson]

Onwards with Phase Four then - spraying.

While the gun was very full and would still spray canted over, I sprayed the lower lips of the doors and panels. Then up the ladder to get a coat on the roof, followed by the exposed frame.

That gun full ALMOST did the right hand panel and surround, but needed a refill to do the remaining three doors - pretty much exactly two gun fulls to finish this coat.

Although it's dry now, I'll leave it over night before it gets the next coat. One or two places need rubbing down a bit - seems that I disturbed a spiders web over head with the air from the gun which got embedded in the paint.

Second coat definitely needed as it's not exactly uniform in density in places.

[hermetic]

No runs Andrew, thats the main thing, I am painting the welder tomorrow, same paint but in green!
Phil

[awemawson]

A quick light flash coat over the panel then come back and give it the proper coat usually prevents runs.

[JerryNotts]

Morning Andrew,

Nice to see some carefully done spraying.

You don't say what size your gun pot is but there are a lot of different capacities. You could go for a pressure pot, say 5 litres, olde non-metric gallon pots can be found. Use with sufficient pot pressure to push the paint to the gun inlet can work fine. I trust you set-up is a  decent make.

Jerry

[awemawson]

Hi Jerry, the gun is a Binks-Bullows 230 that I've had for Donkey's Years ! - must be getting on for 40 years old! Capacity - not sure but probably about one litre.

So having remembered to replace the Rivnut that had pulled out that holds the 125 amp input socket I got on with spraying the top coat. First I rubbed down with a green Scotchbrite pad to remove a few bits that had settled on the job yesterday, and then mixing a carefully measured 10% thinners as recommended had to it.

I must say that 10% with this paint and with my gun and nozzle is a bit of a struggle - I wanted to try and keep to the recommendations to get a decent dense coat, but in the end added a further splash of thinners - it may be that my nozzle is too fine, but it's the only one that I have !

It's an acceptable job, but I could criticise  it if I had to - it'll be far better when all the door hardware and labels go on to take the eye away 

So that's Phase Four completed.

Phase Five - put it all back together - starts tomorrow.

So . . . a paint drying day for the rest of today with a bit of  and later 

[Pete.]

Nice job Andrew 

Can't wait for the first melt!

[awemawson]

Thee and me mate 

I did rescue a rather tacky cast iron 'well hand pump' of the Chinese variety from a friends skip the other day thinking that it could be the first victim to melt 

[mattinker]

Thee and me mate 

I did rescue a rather tacky cast iron 'well hand pump' of the Chinese variety from a friends skip the other day thinking that it could be the first victim to melt 

That makes three!!

[tom osselton]

I’m looking forward to your first melt. Are you going to try greensand or mix a batch for cast?

[awemawson]

I will probably use sodium silicate and silver sand.

When I’m at that stage I’ll start a separate thread

[awemawson]

Yesterday afternoon I stripped off all the masking paper and had a nice anti-social bonfire of it in an oil drum brazier with all the paint rags creating a brief but impressive black plume. Lucky we have no near neighbours 

And this morning I started putting it all back together - bang on cue Parcelforce delivered the little 3 mm plastic rivets from RSComponents so I could re-attach all the various labels and warning signs.

Before I re-connected it to the furnace body I cut the Ty-Wraps holding the four Brewers Hose driver cables and re-arranged them to lie a bit more uniformly before binding them back together with more Ty-Wraps.

Then having attached to furnace body, and the flow and return hoses from the chiller I was able to test for leaks and start pumping water round the system - all sound thank goodness.

Using my 'test mains cable' I was then able to power it up off local three phase, check that it goes ready, and 'ping' the furnace body - it's still working amazingly.

So - next job it to sort out a way of having the high power cable from the generator permanently connected. Rolling it out each time is a major exercise and means that I can't fully lower my roller shutter so I can't leave it as is.

I need to work out whether to trench in the big 6" electrical ducting that I have, or whether either laying it on the surface  or fixing it to the rear wall of the barn is the best option. A bit of cogitation called for 

[Sea.dog]

It looks like new. Another Mawson success 

[awemawson]

Thanks Graham.

Do you remember that heart stopping day when we realised that it had a 15 year old back up battery and shot out to the workshop to investigate 

That was nearly curtains for the project!

[Sea.dog]

I certainly do, Andrew. I'll be sorry to miss the inaugural firing of the first load, unless things ease up, of course