Resurrection of a CFEI 100 KVA Induction Furnace

[awemawson]

Continuing the theme of trying to enhance the safety in the foundry before I start using it in earnest yesterday I admitted defeat with a small but persistent roof leak. Only happens when wind in a particular direction, but the drip was dripping directly onto (and through  ) a double 13 amp socket used for the roller shutter electrics. Amazingly it's never tripped the 30 mA RCD over the years. So if I can't cure the drip, live with it and move the socket 

. . so I did - actually I added a spur to the foundry ring main (in a sheltered position !) as previously it was fed from the shutter circuit for the main workshop roller shutter and now is off the local sub-main so more logical.

Towards the end of the day I ventured down the 'blind alley' that is between our boundary and the welding shop to try and find the safety cover that originally bolted onto the right hand side of the Furnace Driver and covered the exposed output connections. I found it hidden under an inverted plastic water tank that I'd used as air trunking on top of the old refrigerated water chiller that failed. Being of welded sheet aluminium construction it had survived the years pretty well but was absolutely FULL of wild life. Snails, slugs, spiders and goodness knows what! I roughly brushed it clean(ish) and left it in the foundry over night to dry off for inspection.

So this morning after further brushing and blowing out time for inspection. I decided to scrub it with a strong citric acid solution - I'd thought perhaps caustic soda that works well on aluminium, but the citric acid won as it's nicer stuff to work with.

Apart from some pitting corrosion where I had previously stuck a Danger sign it's actually scrubbed up pretty well. A good hosing to rinse the citric acid off, followed by an air blast and an hour in the morning sun and it was ready to bolt on . .

. . .so I did.

A new warning sign ordered, and when fitted will cover those corrosion pits nicely 

Meanwhile I've devised a way of plumbing in a means of measuring the coolant pressure when operating - bits on order - hopefully this will help to give an early warning of any more blockages 

Incidentally, up the 'Blind Alley' I came across a large Air Receiver that I used as a reservoir in the loft of my last workshop and is now redundant - If it is of any use to anyone it's 'free to collector' - you can just see it on the picture.

[AdeV]

One day, in the future, when a new civilisation rises from the ashes of this one, your place is going to prove absolutely fascinating to archeologists! 

[awemawson]

. . . and I'll still be here Ade plodding along through my list of jobs 


Today I installed the coolant system pressure gauge. This required a modest bit of engineering - turn a 28 mm slug of stainless steel, through drill it and bore and tap 1/4 BSP to accept the rear entry gauge fitting. Simple really and only cost me the tip of a centre drill - not too keen on stainless!

The bit I made sits in the branch of a 28 mm Tee compression fitting that I inserted in the vertical pipe run from the pump at a height that meant I could work without draining down the tank.

The book calls for a pressure between 3 and 5 bar. The pressure switch in the Furnace Driver Inlet Manifold clicks over at 2.8 bar, and the Grundfos pump can produce a maximum of 4 bar. So I set the pump bypass tap to give a system pressure of 3.5 bar - comfortably within the spec.

. . . no leaks so far 

(and yes, I now HAVE cut the 'glycerine pip' on the gauge to allow for expansion !)

[mattinker]

Looks like it's coming along nicely!

Cheers, Matthew

[awemawson]

Ready when you are Matthew 

I took delivery of the replacement fireproof cladding for the box on the inverting furnace body yesterday but haven't had a chance to experiment cutting it. The stuff I used before was 6 mm tile backing board and this is 'Aquapanel'  so similar stuff but 12.7 mm / 1/2" thick. When I've cut the panels to size I intend to slather them in sodium silicate solution to firm up the cut edges which tend to be rather powdery. They say that, like plasterboard, you can scribe one side and crack to size, but with the thinner stuff certainly you end up with one side rather 'undefined' - I think I'll experiment with an angle grinder.

This stuff contains a load of cement, so any saw won't be much good after a few cuts, but a diamond angle grinder blade might have better luck

[mattinker]

The way things are, I can't see crossing the Channel before Christmas! Looking forward to seeing this in the flesh!

Cheers, Matthew.

[modeng200023]

I was just thinking Andrew, with all the monitoring you have fitted to the project you won't have time to watch the crucible 

[awemawson]

Well it got used this afternoon - cottage guests had left and Penny was away so an opportunity to fire it up without any complaints of generator noise 

At first I had a bit of a panic. I'd been doing my testing on local mains when fitting the pressure gauge and all was fine. Swapped over to the heavy cable connection,  started the generator up (OK it IS a bit noisy, but a good sound!) but nothing was happening what so ever at the furnace driver - panic . . is wasn't until a few minutes of poking and prodding had elapsed that I realised that when I was fitting the earth bonding in the generator, I'd flipped off it's internal isolator.

A flick of it's lever and all was well with the world!

The very first unsuccessful melt of some copper pipe where the pipes ended up with slits in that I'd done when everything was put back together a few weeks back was tossed on top of a lump of brass as a 'starter pool' resulting in a lump of maybe 4 kgs of very coppery brass after not much more than 5 minutes heating.

It was just another trial dumped into an inverted spare crucible. In the picture the coppery one is the one I did today (brass plus copper scrap) and the brassy one is the other half of the same brass ingot but without added copper.

Now I need to start up the mould making side of things. I'm going to have a try at 'lost PLA' casting using forms 3D printed

I did manage to stick on the Danger notice on the safety guard, and order up some replacement  foundry boots from Zoro Tools. Proper ones with steel toe caps and insoles and heavy leather spats to keep molten splashes from spoiling my socks! What I thought was a modest price at £42 including postage - not many places stock boots that fit my size 13 hooves! The ones I used to use are long lost long ago !

[Pete W.]

Hi there, Andrew,

I quote: 'Proper ones with steel toe caps and insoles and heavy leather spats to keep molten splashes from spoiling my socks!'

I seem to remember reading somewhere that the spats are more to cover the lace-holes of your boots - they're more splash-retaining than your socks and the boots are slow to remove!  What material is used for the RN's flash-resistant clothing?  Is it cotton?  If so, maybe cotton socks should be the order of the day.

[awemawson]

Pete, they've not arrived yet but I think that these ones have quick release fixings for both the boot and it's spat.

As I'm sure you realise reference to my socks was tongue in cheek !

[awemawson]

OOPS - wrong picture - try again !

[awemawson]

I started drawing up a model in Fusion 360 of a label for our 'Bore Hole Taps' - it's 25 mm x 75 mm and needs refining as the detail is going to be too fine for the silver sand I am using with sodium silicate. The idea is to use 'lost PLA' - ie encase the model in silver sand with 4% sodium silicate mixed in, set it with Carbon Di-Oxide, then burn the PLA out in a pottery kiln set to 650 Centigrade. More work needed.

But as an adjunct to this I cut some slices off that big lump of coppery brass that I produced on Friday, and to my surprise found that it was hugely porous. Now I've had this with aluminium castings where hydrogen gets entrapped and forms bubbles but not with brass. I strongly suspect that the metal was far too hot, and the bubbles are zinc vapour. Hard to prove but I'll make a conscious effort next time to pour at a lower temperature.

It's all a (re) learning curve !

[tom osselton]

Interesting I wouldn’t have thought about the temperature vs zinc gas bubble formation.

[pycoed]

Look on the bright side, Andrew: you've just invented Oilite :

[mattinker]

ded.

But as an adjunct to this I cut some slices off that big lump of coppery brass that I produced on Friday, and to my surprise found that it was hugely porous. Now I've had this with aluminium castings where hydrogen gets entrapped and forms bubbles but not with brass. I strongly suspect that the metal was far too hot, and the bubbles are zinc vapour. Hard to prove but I'll make a conscious effort next time to pour at a lower temperature.

It's all a (re) learning curve !

Hi Andrew,

It may be just air bubbles due to your casting in an open crucible.

Have a look at Olfoundryman

&t=0s

He's casting in Al, but his sprue and risers are worth looking at!

Cheers, Matthew

[awemawson]

Very informative and certainly food for thought Matthew - thanks for the link.

[awemawson]

Time to tackle the 'Tilting' furnace body - if you remember I'd previously used domestic plumbing flexible hoses that had adversely reacted with the hydraulic oil in the 'air over oil' set up.

So first drain the remaining oil - most had already been squirted out when the hose fitting burst a month ago!

Then strip off the old fittings and pipes.

Then do a 'dry fit' of the stainless hydraulic fittings that I'd bought to check that I'd got the right quantities and genders.

. . . all a bit of a rush as I've got a chap due in 6 minutes to discuss (fencing of the agricultural type - not epees !)

Have a few pictures:
 

[awemawson]

So it was an afternoon of crimping:

First dig out the Parker crimping machine with it's hydraulic hand pump and a set of crimping dies for the 1/4" hose that I'm using. This size is a rather an arbitrary choice - I hope that I will get sufficient flow remembering that although it's using hydraulic oil, the pressure is only 'airline pressure' at about 100 psi. But I already had the hose and fittings and only had to buy the fixed adapters so that swayed me. Time only will tell . . .

Now the sequence is:

a/ Measure the application and cut a length of hydraulic hose to suit.

b/ Fit a ferrule over each end ensuring that it's fully home by tapping with a mallet.

c/ Insert the appropriate barbed fitting (straight or 90 degrees in my case).

d/ Crimp one end

e/ In the case of two 90 degree fittings adjust angular alignment 'on the job' and mark up the hose, ferrule and fitting.

f/ Crimp the other end

All quite easy, but short hoses with both ends a 90 degree fitting need careful alignment as this hose doesn't rotate to accommodate errors!

The crimper consists of a hydraulic cylinder that, using a 'gathering plate' forces a set of dies down a tapered hole over a set of 'teeth' to close down round the ferrule and squash it firmly, uniformly, and permanently round the hose and barbed fitting.

[awemawson]

Then it was a case of measuring up and assembling the various hoses on the machine, but in 'free space' as I've not yet decided how I'm going to clip them. I want to hold them as far from metal drips as possible, and maybe bend up 'drip shields' to go over them where possible.

However, until I can get it back into the 'able to tilt' state it's not easy to predict what will foul what as the crucible rises up - I may even have to adjust some hose lengths.

So now all the hoses are made and loose fitted and I'll wait until tomorrow to fill it up with oil as the adapter fittings have been 'Loctited'  and that needs to go off

[awemawson]

By this morning the Loctite pipe seal had had ages to 'go off' so I tightened all the cone seating pipe nuts and did a 'dry trial' ie no oil in the reservoir.

I'm pleased to be able to report that it worked splendidly - it sort of questions whether I need the 'air over oil' set up, but I expect with a full crucible I probably do - certainly that was my conclusion back in 2006 when I installed it.

So now I need to sort out pipe clips and some sort of sheet metal splash guards for the pipes. I'd rather assumed that the 'Munson Clips' that I'd previously used were a right off after bad handling in storage, but it turned out that only one 'foot' was broken, and amazingly I had one in my box of 'might be useful' bits (probably originating from the 2006 build!). I've temporarily put them back on, but they hold the pipes too far off the chassis and will be replaced, probably with rubber lined steel 'P clips'.

The arrangement of the Quick Disconnects is as a straight line of four QD's and foolishly I've never marked up what is what. However I dug out a photo of the inside when I commissioned it in 2006 which will let me work it out.

Among the pictures were a pair that reminded me of an issue that I'd had - the copper pipe was barely able to carry sufficient current even with water flowing though, and I'd had to parallel  up 70 mm CSA welding cable to give it a hand with all those pesky electrons! There was also a picture showing where I'd managed to fuse some of that cable - I hate to think what current that was carrying,but I can't remember the circumstances that caused it. (well it IS 14 years ago!)

So I'm now off to order up a few pipe clips !

Have a video of it working:

[awemawson]

Today's task: make up a set of copper commoning links for the Raydyne complete with flying leads of the 70 mm CSA welding cable so that  changing from one furnace body to the other is simplified, as the links on the Inverting Body are a bit of a pain to remove.

OK - need copper bar - no suitable copper bar in stock - squash some 28 mm copper pipe in the Epco 60 ton press and use that! So two six inch lengths were cut off, flattened, marked out, drilled, profiled, and cleaned up in phosphoric acid. I then prepared two short 'flying leads of the heavy welding cable with lugs on the end crimped so as to be at 90 degrees to each other to avoid a twist when in situ.

All then assembled and finished - well not quite as I'll replace the steel nuts and bolts with brass ones when they are to hand.

Meanwhile I dismantled the stainless plumbing arrangement that had previously been used and rescued most of the fittings for the 'may come in useful' box.

[awemawson]

I've just re-filled the reservoir with 32 weight hydraulic oil - no idea what I'd used before - unlikely to have been a hydraulic oil as I had no hydraulic powered machines then.

Using just compressed air, a full tilt was 6 seconds, which is too fast. Putting 3 litres of 32 weight hydraulic oil in the reservoir (cylinders total swept volume = 2.8 litres) it takes about 30 seconds which is too slow - I'd like 15 seconds for a smooth controlled pour. Perhaps I can cut the oil with something to reduce the viscosity?

A bit of 'googling' suggests that the oil in a J&S 540 head with the plain bearings is either ISO 10 weight or 32 weight cut 10% with paraffin.

So what can I use to 'cut' hydraulic oil? Paraffin perhaps - suggestions welcomed !

[awemawson]

As I don't have any paraffin oil, and getting it is a pain, I used Red Diesel. Google tells me that their viscosity is much the same. So I drew off 1 litre with a stomach feeding  syringe (sorry next years lambs!) and replaced it with 1 litre of Red Diesel.

The result: the 30 second rise time is now down to 22 seconds and the current mixture is 1/3 Red Diesel and 2/3 32 weight hydraulic oil - so that is definite progress.

Tomorrow I'll adjust the ratio again to maybe 50:50 - or even less, as if I go too far I do still have the flow rate valves to adjust - they are fully open at the moment. Need some hydraulic oil in there for cylinder lubrication, but it's not a high stress application really.

When the aerated hydraulic oil that I drew off has settled it can go in the dumper truck, as it leaks like a sieve!

[mattinker]

Hi Andrew,

If I remember correctly, your red diesel has a dissolved, wax ( it's the element that solidifies when diesel freezes) in it which is there to lubricate the injector pump when used as fuel in a diesel engine. So please, correct me if I'm wrong, in my opinion, lubrication is not  a problem!

Cheers, Matthew.

[PekkaNF]

I started thinking this Yesterday, but I have first hand experience on normal hydraulic olis of VG32 and VH46 viscosity. The company chooses Iso VG 32 over 95% of the thime, then VG 46 is used only when ambient temperature is significantly higher. On lower end of the ambient temperature tank heater kicks in and the hydraulic oil heats due to work it performs.

I wonder if the normal iso VG 32 oil would perform fine in the working temperature?

Most normal hydraulic oils are pretty much normal mineral oils that have some additives to prevent foaming, help filtering, disolve water (water is one of the biggest problem in modern hydraulics, you don't want it to steam on elevated temperature of cavitate at uner pressure, or rust) and usully a litte amount of EP additives to help lubrication.