Resurrection of a CFEI 100 KVA Induction Furnace

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russ57:
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Should have enlarged it... I didn't see the 'manifold' words - there is obviously flow between the in and out manifold not shown...

-russ

awemawson:
It is very confusing looking at the actual machine which is why I wanted to do the diagram to sort it out in my head.

The manifolds connect to flow and return on the Chiller, and as Graham says the pairs to / from the furnace body are A & B, and C & D

But then additionally there are the electrical connections. B & C are strapped together as are A & D and these two connections connect the coil of the Furnace Body, and the internal capacitor bank and form a tuned resonant 'tank' circuit

Once drawn out it’s actually pretty simple.

awemawson:
The new ball bearings arrived just before lunch, so I've just stripped and rebuilt all four quick disconnects.

I'd intended to clean up the inner brass-work with a bit of steel wool, but as I'm not changing the O ring seals decided against in case a strand of the steel got trapped under the rubber.

They came apart and went back together surprisingly easily - I used a tiny smear of Vaseline in each ball housing to hold the balls - I didn't want loads as although theoretically the coolant path should not come in contact I didn't want to risk Vaseline trace in the coolant.

Intriguingly the new balls measure 6.33 mm not 6.35 - just like the bag that I already had. Now my first thought was that the difference was due to using a digital vernier guessing stick rather than a proper micrometer, but as I happened to have my metric slip gauges handy I measured a 6 mm slip and it was dead nuts on. This digital vernier has always been surprisingly accurate and I had to apologise to it for doubting it's voracity :clap:

So is the 0.02 mm a looseness for normal bearing fits :scratch:

Sadly I can't do more this afternoon. Now lock down is lifted on holiday cottages our bookings are picking up and today is a 'double change over' with two sets of guests leaving, and two arriving, and the Covid-19 cleaning regime required is unbelievable and very time consuming.

Tomorrow should be better and I can then hopefully re-fit the Q/D's and hoses and resume testing :med:

awemawson:
A bright and early start to put it all back together for testing - and also a nice bight day to go with it :thumbup:

First I refitted the Flow and Return pipes for the Chiller completing the coolant circuit between it and the Furnace Driver.

Then on the Furnace Body I re-reinstalled the four Quick Connects and their associated linking straps that hopefully will preserve the newly installed stainless balls. Then the four new hose / cable assemblies from Furnace Body to Furnace Driver went back on, and that's about it . .

. . . time to turn on the coolant pump and see what happens. Two sharp 'click' sounds - I know what that is, it's the Flow Gauges - their magnetic torpedoes rise with flow knocking the top of the gauge, a good sign, actually a VERY good sign as previous symptoms were no flow in the left hand one.

Now previously the pump bypass tap had to be fairly closed, (ie higher pressure) for the flow gauges to rise, but now I can open the tap fully (ie lowest pressure) and they still work. I do remember that as the pressure was adjusted from low to high the right hand one lifted first, followed as the tap was closed further, by the left hand one. So there must have been a partial blockage for some time - symptoms were there but I hadn't recognised them.

So, in for a penny, in for a pound - put 'local power' onto the furnace driver and see if it goes PRET (ready) - oh yes. I then intended to 'ping' the Furnace Body to confirm resonance but inadvertently had the key switch in 'CHAUFFE' (heat), and I got the characteristic 2.4 khz humming and 15 kw indicated as power consumed. Quickly pressing stop, and feeling the 2.5 mm 5 core cable from local mains luckily no harm done, but I wouldn't normally try and actually HEAT something without having it powered by the big generator - phew got away with that one.

In conclusion, there must have been a partial blockage previously, and like a blood clot moving about the body, got to somewhere vital and killed things. My various activities over the last few days have cleared the blockage but I'm no closer to knowing where it was apart from that is was in the left hand Flow Gauge / 'C' Port / Inlet Manifold loop UNLESS that input mesh screen was the issue all along. (but if so why was the right hand flow gauge not affected as well?)

Now I've disturbed a large number of coolant connections in this investigation (17 at a quick count!) so I've left the coolant pump running while I write this and have a coffee, let's hope no leaks and no floods when I return.

russ57:

-russ

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