The Craftmans Shop > New from Old
Resurrection of a CFEI 100 KVA Induction Furnace
awemawson:
22kw equates to 1.65 kg/H iirc so it depends on the heat rating of your torch
awemawson:
Still no word from Flamefast re jet sizes so it looks like I'm on my own there !
So I decided to get on with a bit of 'routine maintenance' on the hearth. The gas / air mixture enters a chamber below the hot bit, the top of which is a firebrick circular tile pierced with a humongous number of 1/8" holes for the mixed air / propane to pass through into the ceramic chips. I know from previous use that these holes get blocked up with debris from the forging and the ceramic chips themselves. Doing this exercise when I first got the forge I ended up buying a new pierced tile from Flamefast as there were so many that I couldn't unblock. This time I managed to clear the vast majority with a short length of 1/8" silver steel gently tapping with a light hammer. Some however where beyond clearing. I did this exercise with the air blower working to try and keep as much debris as possible out of the lower chamber.
The tile is set in fire cement, but I notice that although its periphery is well sealed, the four 'quadrant tiles' that form the actual bowl of the forge are not well sealed one to the other. I've placed an order for fire cement to resolve this - due Monday /Tuesday.
I'd hoped to be able to test the burning of the gas with no chips in place however it seems that the chips are needed to anchor the flame to the burner as the flame seat lifts off the holes in the tile.
Incidentally those chips are ridiculously expensive. About £90 plus VAT and carriage for enough for the forge. I can't believe that they are SO special. What you see in the bucket (picture below) are ones I bought new in 2004 so they last OK but there are always losses as they cling to items heated up, particularly if there is any flux present.
I do wonder if the ceramic pebbles sold for gas coal effect fires could be pressed into service. They are far too large but I've no doubt that my 60 ton press would be happy to help reduce them to chips !
awemawson:
The Fire Cement was delivered today - early so that's good. KOS brand - I can remember using this stuff to embed nichrome wire coils to make power resistors back in my youth !
So - blow out the dust from the joints between the quadrant fire bricks, dampen the brick with a wet brush, and force the fire clay as far as possible into the joints. Make tidy with a wet brush, and I also did the circular pierced tile to quadrant brick joints.
All this is to seal the plenum chamber beneath the pierced tile so that the propane / air mixture only comes up through the pierced holes and not the cracks.
Next job is to sieve the remaining ceramic chips to remove the dust particles before they go back in the hearth bowl.
I'll leave the fire clay a few hours to air dry before a gentle firing to set it. There will undoubtedly be cracks as it fires up but it will be better than it was !
awemawson:
Sieving the ceramic chips produced quite a bit of 'fines' and several coagulated lumps which I discarded and re-loaded the forge bowl with what remained.
When I lit up I was surprised how much steam it produced - 1/4 of a cup at the most was used in moistening and smoothing the fire clay, and I suppose that the fire clay itself contains water. At this stage the fire clay isn't being subjected to any great heat as where it was applied is several inches away from the hot chips. My idea being to heat the chips and let the warmth spread gradually to the fire clay.
Previously there had been evidence of combustion in the rear quadrant joint (see picture with burn mark on the paint) I'm glad to say that is no longer happening and the steel body stays cool as it should.
Having cleared the perforated tile holes there is a noticeable change in the shape of the hot area of ceramic chips - heat is over a much wider and more even area for a given gas pressure.
So was it worth all the hassle - yes I think that it was even though all I intend to use it for is pre-warming crucibles !
tom osselton:
Looks good!
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