Resurrection of a CFEI 100 KVA Induction Furnace

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awemawson:
Last night I mass produced modified butt splice crimps ready for an intensive day of cable / hose making.

First cable this morning went together really easily, the 3/4" copper end terminals slipping up the Brewers Hose very easily with a drop of Hellerman cable lube.

The next cable was an absolute nightmare. When I stripped the ends ready to pull the old cable out for re-use I was met by cable end in an appalling state - really badly frayed. And pulling the bulk of the cable from the hose it wasn't in the best condition. My first reaction was that this must have been one of the original cables that I re-used, but looking at the big reel of 70 mm welding cable that I still have from all those years ago they both have the same very fine wire format wheras the other two cables had somewhat thicker strands.

No choice though - this wire cannot be re-used so I set to and stripped the insulation from four meters of welding wire off the reel, and crimped a lug on the end to pull it through the hose with the lug hole Ty-Wrapped to the eye in the end of my 6 mm fibreglass pulling rod.

Now this was exactly how I'd pulled the other wires through, but this time it was an absolute pain and put up a huge fight - no real idea why. I got to within 21 inches of the end when the Ty-Wrap (a stout THICK Ty-Wrap) snapped :bang:

Shining a torch down the hose I could see the lug, but how to get at it? In the end I went fishing with a hook bent into the end of a 1.6 mm welding rod. First attempt got it half way before the hook straightened - second attempt was sucessful.

Next job, crimp the end fitting on and pull the cable back, pushing the fitting into the hose. First inch was fine but after that I paid dearly for every millimetre of progress despite loads of Hellerman lube on the fitting. But we got there in the end.

Then it was a case of compressing the hose back down the cable six inches, clamping with a Mole Grip, and crimping the other end on, followed by releasing the mole grip and pushing the fitting up the hose - this end wasn't too bad.

So (apart from Band-It clamping the ends and serving with heat shrink) that's three down and one to go. but I've called it a day - our first set of 'Cottage Guests' arrive shortly, we having been closed down by Covid-19 so I need to be able to meet and greet at short notice.

I did however remove the ends from the last cable, and sadly it also is the finer strands, so that's something to look forwards to tomorrow :bugeye:

awemawson:
Well I'm pleased to be able to report that the last cable wasn't as bad as it could have been. although the fine strands were a bit frayed at one end there was sufficient 'good' cable to make up the remaining assembly.

And even better - the lengths do seem to be better than previously and dress together nicely on a trial fit.

To complete the last hose, having had yesterdays major issue pulling the copper through the hose, this time I first pulled a length of 6 mm polypropylene rope through, then used that to pull the copper, rather than trying to pull directly on the rigid 6 mm fiberglass duct rod (which is hard to grip)

Having done a trial fit to check the lengths are now correct (they are!) I then flushed out each hose using mains pressure water to get rid of the last of the phosphoric acid and any debris that may have entered. The end fittings are 3/4 BSP Female with a cone internally, but using a stack of rubber tap washers formed a passable seal for this temporary exercise. Pleasingly they are all free flowing (as they should be) but when I dismantled the original hoses I found bits of hose lining jammed in the copper pipes that had been scalped out as they were pressed in. To try and avoid this I spent quite some time and trouble fairing the copper fittings, even buffing them on the wire wheel.

I'm now off to re-fresh my memory how to use the Band-It tool and do one or two test pieces !

awemawson:
Reading the very scruffy and out of focus instructions that I had secreted in the Band-It box I decided that there must be better copies 'on the web'. Well, downloading one from the makers web site it told me to cut the stainless band before wrapping and tightening resulting in a loss of about 6 inches of band for every clamp - blow that for a game of soldiers - I've 24 of these to do - that's a lot of wasted stainless band :bugeye:

So I 'winged it' and in practice it's not too bad to do - with the roll of banding uncut it gets in the way of cranking the tightening handle, but that's simply cured by deflecting it with your thumb as you crank. In relatively little time all twenty four Band-It clamps were applied, and I was just thinking 'time for tea' as I still hadn't received the delivery of large heatsink tube to dress the clamps to save cuts on the sharp bits when Adrian the ParcelForce man hove up delivering my order from RS.

Tea will have to wait - eight 100 mm long slices of heatshrink were cut and shrunk over the Band-It clamps so the hose assemblies are ready to re-fit.

I'll not refit them until I've replaced the Chiller flow and return hoses with the new ones that were delivered the other day - I'd thought that I could use the existing Jubilee hose clamps but of course the new hose is much thicker wall than what is on, so that doesn't work. I had considered using Band-It clamps, but they would be permanent so I ruled that out.

. . . so more Jubilee clips on order - as I said to Adrian - See you tomorrow !

awemawson:
The larger Jubilee Clips turned up just before lunch, so I've been able to replace the flow and return hoses for the Chiller with ones with a more substantial construction, with a far thicker wall.

All went well, not much coolant split, and I was able to install the newly re-made cable / hose assemblies. Again this went well with no leaks - well not entirely true, I'd left one coupler nut only hand tight so it weaped, but easily cured.

However the Furnace Driver will not go 'Ready' as coolant is not flowing in the left hand flow gauge so it's magnetic float is not lifting with flow. Now this is indicated as an 'Ext 1' fault on the control panel, which is what happened just before that hose burst.

I know that the new hose / cable assemblies all flow satisfactorily as I tested them, so there must be a blockage elsewhere. The documentation gives no indication of the plumbing so I'm going to have to 'knife and fork' it. It could be the furnace body or the furnace driver - time only will tell, but I'm now allocated to other things so that's a job for tomorrow.

awemawson:
Well I couldn't just leave it, I had to have another look to keep my sanity.

First thing to check - there is an input mesh / screen filter that I've never been able to get at properly due to the way the flow and return chiller pipe block access. So a bit of heavy dismantling involving my biggest Stilsons got the big connections undone so that I could remove the whole assembly, check it and put it back in a different orientation so that it was accessible in future. Now this screen is on the input, and coolant was flowing, so unlikely to be 'the' fault but it needed looking at. Sure enough there was a fair amount of debris that was easily washed away under the tap, but it wasn't totally blocked.

Then I removed the four recently re-made hose / cables and again proved that there was free flow down them - there was.

I then turned my attention to the 'furnace body'. There are two coolant paths, "A to B" and "C to D" - I believe that the continuous copper tube coil of the furnace has a deliberate block to coolant in it's centre, and coolant flows in at the top and bottom, (A&C) and out at the centre (B&D)

Blowing with an airline there is free passage from A to B, but C to D is blocked.

Why ? I have no idea. Perhaps a bit of debris stuck in there? Or perhaps one of the 'QD' connectors have failed? Either way it's going to have to come apart.

. . As you can imagine this is a bit of a set back to the project - let's see what tomorrow brings

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