The Craftmans Shop > New from Old
Resurrection of a CFEI 100 KVA Induction Furnace
Pete.:
"May cause cancer by inhalation" - that can only mean it's the GOOD stuff :D
awemawson:
So there was I melting the greenhouse . . . . . .
. . . . . OK let me explain, some years ago we had a greenhouse that was a bit of absolute imported rubbish - it didn't last the first winters storms - and for several years now there have been bits of green anodised aluminium channel section getting in the way and being tripped over in the horticultural area. Time to sort them out (I was told).
Now no point in chucking it out, turn it into ingots and save it for later use. Cut up with the band saw into convenient 'crucible lengths' today was it's appointment with doom. I even welded up an extra ingot mould as there was 3 kgs in the bundle.
All put in the pot, coolant water from the borehole circulating, 110 kva generator purring away . . throw the switch Igor :bugeye:
Wound it up to 50, then 60 then 75 kw - channel section sinking nicely into the melt - hang on - what's that burning rubber smell ?
Now there had been flames off the channel sections, not unexpected with the dross of years on the surface but this was distinctly burning rubber - what's going on and why are there flames down there among the various driver hoses ?
It turns out that one of the driver cables that is enclosed in 'Brewers Hose' for water to circulate to keep it cool, was resting against the 'air hose' (actually braided hydraulic hose that I'd used for robustness), and there must have been enough electromagnetic coupling from the driver hose to the metallic braiding to heat it up and set the rubber sheath on fire !
Turn off the furnace driver, give the hose a blast from the CO2 extinguisher and the flames subside - move the hoses apart - tentatively tilt / untilt the furnace (which uses this hose for the pneumatic cylinder) - OK still working - turn the furnace driver back on while the crucible is still hot, and pour the ingots (second one looks lousy quality)
. . . the good part of this is that it has only cosmetically marked the Brewers Hose (which is darn expense) - OK the air (hydraulic) hose is toast (literally!) but I have miles of that so it's not an issue.
OK Greenhouse melted, domestic demands satisfied, just need to swage up a new hose !
mattinker:
Andrew,
I know you are fortunate enough to be able to analyse your metal content! Extrusions are usually pretty pure Al. Did you add any Cu? I find 4to 5% Cu makes a harder more easily machinable alloy!
Cheers, Matthew
awemawson:
Matthew it's still in the ingot moulds. I made my judgement on how horribly it poured but as you say extrusions are usually LM2 or similar.
awemawson:
Added to today's tasks was of course making good yesterday's damage :bang:
Taking the hose off and duplicating it was easy, as I had the crimp ends and 1/4" hydraulic hose in stock, and I also have the proper 'Parker' crimper. It's a bit of a fiddle to manipulate but good solid kit that gives a nice reliable result.
The second air hose running along side this one had suffered a bit of collateral damage but I judged it safe to use - mainly cosmetic scarring.
Now having put it all back together the obvious question is how to avoid the problem in the future :scratch: I had left the four Brewers Hose power feed cables unstrapped to give more movement flexibility but it occurred to me that these are basically a transmission line (well a pair of transmission lines) and they avoid radiating by the fields of parallel conductors cancelling out (i'm assuming here that the damage WAS stray energy radiation from these leads inducing large currents in the braid of the air hose) so the first thing that I did was Ty-Wrap them into pairs.
However watching the action of the crucible assembly raising and lowering (it tilts) in the down position the power cables press firmly against the air hose which is less than desirable from many point of view. However stopping this is by no means simple. I need the hoses to emerge at a different angle from the base of the tilting assebly.
If I can source some brass 3/4" BSP cone connections that are at 45 degrees then that might be a possible solution but I reckon that they are probably as rare as hens teeth !
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