Author Topic: Resurrection of a CFEI 100 KVA Induction Furnace  (Read 83267 times)

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #725 on: February 10, 2021, 01:29:53 PM »
22kw equates to 1.65 kg/H iirc so it depends on the heat rating of your torch
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #726 on: February 11, 2021, 05:33:13 AM »
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 !
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #727 on: February 12, 2021, 07:22:42 AM »
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 !
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #728 on: February 12, 2021, 09:20:27 AM »
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 !
« Last Edit: February 12, 2021, 01:36:25 PM by awemawson »
Andrew Mawson
East Sussex

Offline tom osselton

  • Hero Member
  • *****
  • Posts: 1255
  • Country: ca
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #729 on: February 12, 2021, 07:55:57 PM »
Looks good!

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #730 on: February 13, 2021, 05:31:24 AM »
Thanks Tom  :thumbup:

The 'High Flow' propane regulator arrived this morning. Output supposedly 3/8" BSP and is printed on the outside of the box but when I looked at it and tried a 3/8" BSP fitting it wasn't ! Delving into the box the instructions say 3/8" NPT

Now 3/8 BSP is 19 TPI and 3/8" NPT is 18 TPI - they are NOT compatible when hoping for a gas tight seal  :bugeye:

A pain as I've had to order up an NPT hose tail, and NOT the sellers fault as Silverline had marked the box BSP - some one has screwed up !
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #731 on: February 14, 2021, 10:53:42 AM »
Time to replace the hoses on the Torch associated with the Ceramic Chip Forge. It occurred to me that I hadn't taken a picture of it burning previously then I realised that it was that the old hoses were SO stiff and inflexible I couldn't hang it on it's allotted hook for the picture. Not so now - I'm using 8 mm i/d propane hose for the gas and 10 mm for the forced air. These are close but not identical to the originals which are undoubtedly Imperial sizes.

It was such a struggle to get the fittings onto the hoses that I had to resort to unusual means. I'd tried loads of lube and boiling water to no avail, what I wanted was something hot and slippery - a cup of very hot oil to dip the hose in. Searching about for a suitable flameproof metal container I settled on a 'turn over handle' that I'd made to set the timing on the Thwaites dumper truck. Set in the vice. 3/4 filled with oil and heated to 125 C with a blowlamp it worked quite well. Hold the hose end in the 'cup' let the rubber heat up, push it on. Still quite a struggle but far easier than using hot water !

I'm still waiting for the proper double ear 'O Clips' for the 10 mm hose so that has temporary ones on at present. Torch now easy to manoeuvre with no more fighting the hose to get it where I want it.

There is one 'strangeness' that I want to get to the bottom of. If the hearth is burning there is no gas going to the torch, despite the fact that there is a direct connection from the gas supply to it (via a ball lever valve)   I have a feeling that maybe it is because the gas to the hearth is drawn into its burner by air flow through the venturi and perhaps the gas pressure in the internal plumbing is pulled down sufficiently that air is drawn in via the torch gas jet. This effect is also exhibited by the 'Bunsen' pilot jet.

When my 'High Flow' regulator is plumbed in (awaiting an 8 mm 3/8" NPT hose barb) maybe this symptom will be eliminated.

Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #732 on: February 14, 2021, 12:29:13 PM »
Very interesting Andrew, that torch looks a lot like mine, and yet the flame sems to be reversed, you have a flamein the centre, whereas I have a flame round the outside? I wonder if some idiot at this and has the hoses reversed?
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #733 on: February 14, 2021, 01:20:26 PM »
Phil the air hose is fatter than the gas hose so hard to get them wrong :scratch:
« Last Edit: February 14, 2021, 01:52:30 PM by awemawson »
Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #734 on: February 15, 2021, 06:51:20 AM »
I am going in this morning so I will check, but I think mine are the same diameter, and both RH thread on the torch end. My torch seems to be blasting air out of the centre hole, producing a cold core to the flame. Any road up, summats not Jannock, as my old boss used to say, i will check it out and let you know!
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #735 on: February 15, 2021, 07:06:03 AM »
Interesting - the metal tube bits of my torch have the hose barb grooves directly into them so no screwed fitting as such - just push on and crimp. Out of the DS130 the gas is 1/2" BSP male cone and the air is 5/8" BSP male cone. (Don't often see 5/8" BSP and this one is an adaptor down from a 3/4" lever ball valve)

There doesn't seem to be a jet as such on my torch - the burner end is a wiggly steel shape that unscrews and apart from the inbuilt taper control knob that does air and gas in separate sections there seems to be no restriction other than the size of the tubes that the torch is made from.
Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #736 on: February 15, 2021, 02:49:33 PM »
NAH MATE! my imagination, you can't get the gas and air pipes swapped over, they  would fit, but then there would be no gas at the pilot! obvious if you have half a brain! My hoses are the same size, and have threaded couplings onto the torch, and it has also just been rebuilt by Flamefast, who recomended the 37mbar reg, but made no mention of throughput of gas as I can remember, I will check tomorrow and take pics if I get chance, but tomorrow is Holbrook bed collection day, so it will be fraught! Wish me luck!
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #737 on: February 18, 2021, 05:39:07 AM »
At last I've heard back from Flamefast - apparently 3 mm is the jet size for propane - the one currently fitted is the one I made at 3.5 mm so I'll make another in due course.

(Note: The torch is rated at much the same output as the forge so I used it for the following tests)

I've managed to get my hands on a suitable manometer to cover the propane (37 mBar)  pressure range so can do some proper diagnosis on the issues. Setting my (probably low flow rate but adjustable) regulator to 37 mBar  with no gas flow and then setting the torch burning rapidly demonstrated the problem. The gas pressure dropped dramatically to barely 1 mBar (though the torch burnt well!)

Re-adjusting the regulator so that the pressure returned to 37 mBar gave a huge flame and insufficient air for the amount of gas, so luminous, however throttling the gas down with the lever ball valve on the manifold I could restore the flame to a very acceptable shape and colour.

Of course turning off the torch increased the gas pressure well above 37 mBar (blowing my red - dyed water out of the manometer !)

So I definitely need to increase the feed pipe bore and get the high flow regulator fitted. The feed from regulator to the  forge is currently 8 mm and I have 13 mm on order with associated fittings to allow the high flow rate regulator to be used.

« Last Edit: February 18, 2021, 06:27:21 AM by awemawson »
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #738 on: February 19, 2021, 06:53:15 AM »
The hose and fittings have arrived to fit the new 'High Flow' regulator and a fatter feed pipe from the regulator to the forge -13 mm as opposed to 8 mm -
This represents a large increase in delivery area - 50 mm increased to 133 mm

As expected the propane pressure now stands up better to the flow of the torch and the forge, but still dropping to about 30 mBar.

However I notice that there is obviously a leak between the perforated ceramic tile that is the actual burner and the pan or plenum chamber below it as gas / air mix is leaking out below and igniting at the side of the quadrant tiles - this is bad news as it means digging the pre-formed tiles out of their bedding cement to see what is going on.

This ceramic chip forge is being a bit of a pain (to say the least) taking far too long as it is really a diversion off the 'main event' which is the Induction Furnace, however I don't feel that I can leave it as it is and must bite the bullet and fix it.

Andrew Mawson
East Sussex

Offline Muzzerboy

  • Full Member
  • ***
  • Posts: 124
  • Country: gb
    • The Mighty Shiz
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #739 on: February 19, 2021, 10:30:54 AM »
FWIW, there's "25KG 1400DC Dense Castable Refractory Furnace Kiln Forge Lining" on homeworkshop.org.uk at the moment. No idea if that's even remotely applicable, or pricing or anything but thought I'd mention if you haven't seen it.

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #740 on: February 19, 2021, 11:16:29 AM »
Thanks Murray - as you will see from the pictures below I've managed to remove the perforated tile without breaking it, although I've yet to clear about 20 holes that are refusing to be poked free. Perhaps a carbide drill will work if I can find any long enough and thin enough (1/8" x 2")

The fire cement / grout or whatever it should be called that surrounds the tile and seals it to the 'quadrant tiles' and the plenum chamber is very friable and crumbly - probably intentionally to allow for expansion and contraction. Whatever it is it's the correct stuff that I bought from Flamefast years back. The tile sits on a fibrous substance that sits on the steel of the plenum chamber. Now I (perhaps foolishly) didn't replace this all those years ago and it has totally fragmented. Whether it is intended as a gas seal or just as a thermal cushion between the steel and ceramic I'm not sure. I have a call in to Flamefast but they've not come back to me yet.

It is possible the 'gasket' is just Kaowool  or similar.
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #741 on: February 19, 2021, 12:14:02 PM »
Blowing through the 'perhaps Kaowool' tells me it's far too permeable to be a seal so I think that it is just a thermal barrier and perhaps also an 'expansion cushion'  between the steel and ceramic bits.

The good news is that I have managed to clear ALL the perforations in the tile by extremely gentle and slow application of an 1/8" HSS jobber drill. Much to my surprise it slowly dislodged material that was too stuck for an 1/8" punch and hammer to move.

(anyone want a grossly maltreated 1/8" drill bit  :clap: )

Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #742 on: February 19, 2021, 02:27:10 PM »
Well Done Andrew! not an easy task without a breakage! I have today dug out the paperwork which came with my torch when it was rejigged for propane/butane, and the torch demand is 1.66 Kg/hr and output 23.5kW for the T4 torch.

Phil
Edit, this effectively puts me in the same boat, except that the T4 operating pressure is 35mbar, not 37 will that regulator be ok or not? For what they cost, I will buy a higher throughput 35mbar one!!
« Last Edit: February 19, 2021, 02:57:02 PM by hermetic »
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #743 on: February 19, 2021, 02:51:18 PM »
Thanks Phil,

Those figures tie in pretty well exactly with what I was given by Flamefast but means that your regulator is marginal at 1.5 kg/H
Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #744 on: February 19, 2021, 04:16:22 PM »
I now find that nearly everyone sells 37mbar, but not 35mbar! Will look again tomorrow, Time for T and bed!!
Phil
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #745 on: February 19, 2021, 04:21:04 PM »
Phil, they probably say 35 mBar to allow for a bit of loss in the pipe due to the flow - 2 mBar is peanuts.

But do you have any way of measuring the actual pressure when in use. I expect that it'll be lower than you expect !
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #746 on: February 20, 2021, 06:58:03 AM »
Being a Saturday no more progress in sourcing the correct bedding compound for the tile - it's a very light, crumbly white material rather like Plaster of Paris but softer. I'm fairly sure that the gasket / cushion under the tile is a KAOwool type and that can be sourced easily in suitable sheets.

As for the bedding compound whatever I use needs obviously to stand up to the heat, give a good seal to the gas / air mixture between the plenum chamber and the perforated tile and yet be able to be dug out in the future to replace the tile (which really is a consumable). There are various high temperature silicone seals that look good on paper but I've never used them. However all the ones I've found say (oddly) not to be used as a gas seal despite being intended for flues  :scratch:

I thought I'd try and 'size the problem' by laying the tile back in unsealed and ungrouted and see how much was actually escaping. In the picture you will see a blue fringe where the escaping gas / air mix has ignited, though interestingly now the flames no longer lift off the tile seat - this is probably due to the new regulator.
Andrew Mawson
East Sussex

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #747 on: February 20, 2021, 07:06:23 AM »
Andrew Mawson
East Sussex

Offline hermetic

  • Hero Member
  • *****
  • Posts: 765
  • Country: england
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #748 on: February 20, 2021, 12:53:19 PM »
Andrew, could that bedding material be there to dissipate the gas so that you get a flame out of every hole? difficult to photograph I know but it doesnt appear that the outer holes are burning? I have seen this dissipation layer in an ornamental gas fire we had which was supposed to look like a log fire. Also seen somwhere, gas burning on the surface of a bowl of sand which acted as a dissipation layer, but can't remember where. If so, would a layer of fiberglass or rockwool work?
Phil
Edit, where did you get your 4kgh regulator from?
Man who says it cannot be done should not disturb man doing it! https://www.youtube.com/user/philhermetic/videos?

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: Resurrection of a CFEI 100 KVA Induction Furnace
« Reply #749 on: February 20, 2021, 02:03:08 PM »
Phil, as far as I can recall from about 20 years ago the layer under the tile was washer shaped with a 6" hole in the middle leaving all the holes exposed, and a 12" outer diameter matching the tile. But it had totally fallen apart as I didn't renew it all those years ago. I'll try to get an original one on Monday.

The regulator was from eBay - It's a Silverline 997865. I got it from a seller that just had the one, and it does seem that there is more than one version as some say 3/8 BSP and  some 3/8 NPT and are undescisive as to whether it's LH or RH. Mine was NPT RH and cost me the princely sum of  £7.95 !

In normal use the ceramic chips defuse the gas / air mix of course and add a bit of back pressure hence the outer holes come into play. In the picture, the holes opposite the pipe leading the gas / air to the plenum chamber are taking most of the flammable stuff.
Andrew Mawson
East Sussex