Patching Up a Furnace

Home enthusiasts discuss their Foundry & Casting work.

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Pipescs
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Patching Up a Furnace

Post by Pipescs » Thu Mar 31, 2016 8:07 pm

I figure I am about to be told I am wasting my time here.

This is an attempt to keep the shop furnace going for another year as I don't really have the time to reline it right now.

My furnace was built to the plans sold by Colin Peck. While I do like the oil burner he designed, I am not impressed with the life span of the furnace body itself. It is only 1.5 inches thick and has not held up well. Having said that, To be totally honest, I did not know what I was doing when I mixed up the refractory. Too much water led to early cracking.

After a couple of years hard work it is starting to fail at the top lip and a lot of the exhaust is blowing out of the lid area instead of the vent.

This is the worst of the damage.
IMG_0891.JPG


To try to extend its life I purchased two half gallon containers of Furnace Repair Cement. Total cost with shipping for the gallon was thirty six dollars. (If it does not work it will not be a great loss at least.
IMG_0889.JPG
The mixture is thick enough that it smeared on the sides with a two in brush. The directions say to clean and wet the surface, then spread on a thin coat. At this point it becomes about gluing bricks back in. In my case I wanted to build up the upper lip so I mixed the remainder of the first container with a couple of pounds of Fire Clay to turn it into a very stick thick putty. It became too thick to brush or trowel, so mostly it was installed by hand. (washes off with water and scrubbing)

I used the putty to fill the inside cracks and holes, then built up the top lip with the putty. I used a two inch brush to add a original thickness layer over the puttied up cracks. After this I covered it with plastic and then a heavy steel plate to make a smooth top lip.
IMG_0897.JPG
The plan is to now let it set for a week or two and do a couple of low heat burns to drive the moisture out of it slowly.
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

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steamin10
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Re: Patching Up a Furnace

Post by steamin10 » Fri Apr 01, 2016 8:29 am

IMHO anytime you make a move to help yourself, you are extending your learning curve. Pass or fail, you are going to learn something.

My home built furnace for rendering aluminum was built with large kiln brick stood on end, with fire clay and sand mortar. It is loaded with cracks but has never been relined, or fallen apart. It was not made with castable so it is a different animal than your creation. It is also fired with LP gas from a 100 lb bottle. It will not attain bronze temps like the other two furni, so it sees less destructive heat levels.

I do not expect your patch work to stay pristine. I think it will flake and crack, at the minimum, but that is the nature of these things anyway. You have taken steps to lengthen the useful life, and that is the goal. Good looks are not.

As for the drying cycle, it may be aided by an IR light hung over the bore, or a 100 watt bulb laid in the bottom. The relatively gentle heat will drive the moisture out without too much hassle. a day or two, and you are ready to temper the new coating with a pilot fire to a full burn.

If and when you come to a reline, consider using a wrap or two of chicken wire to loosely bond the castable together to prevent separation of the pieces that inevitably occur. It will help to prevent fall out of chunks as you experienced.

I have watched your posts with relish, and enjoy your progress, thanks for sharing.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Fri Apr 01, 2016 6:36 pm

Light Bulb inserted
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Sun Apr 03, 2016 8:58 am

Morning all,

Overall I am very happy with my patch job.

After a couple of days dry it out with a light bulb I did a small wooden fire, then a larger fire with a blower.

At this point I added a lot of wood and did a really hot fire.

This all with the lid in place. The last firing was producing a nice two foot plume.

The lip (which is my greatest problem) turned out great. it was patched with the cement/fire clay home mix. it came out hard and did a nice job of cutting off the fire out the lip problem.
2016-04-03 07.22.02.jpg
After it cooled off I found that the areas where I had painted on the cement without the fire clay had bubbled up into thin wall bubbles. They turned out to be surface only and the area under the bubble was in much better shape than original. Based on the amount of steam that came out of the walls when I fired it, I am sure this was moisture trapped in the cement. A lower heat on the initial firing would have prevented this I believe.
2016-04-03 07.21.52.jpg
So the next step is to do a batch of Aluminum for a couple of projects
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

Harold_V
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Re: Patching Up a Furnace

Post by Harold_V » Sun Apr 03, 2016 3:20 pm

Pipescs wrote: A lower heat on the initial firing would have prevented this I believe.
Allowing a greater period of time would have prevented that from happening, too. Because the surface forms what is a relatively impervious film, it takes considerable time for the free moisture to evaporate. What's important is that the material not be taken beyond the point of boiling until all the free water has been expelled. No steam, no bubbles.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Sun Apr 03, 2016 4:12 pm

I am thinking about breaking up the surface after the next firing to look it over. I have anther half gallon of the cement to use
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

Harold_V
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Re: Patching Up a Furnace

Post by Harold_V » Sun Apr 03, 2016 8:40 pm

Hmmm. From my vantage point, that may not be a great idea. The inside of a furnace rarely has a great appearance. So long as it is performing the required duty, might be a good idea to just use it as is, then use the balance of the patch material to restore it as required. So long as you don't have any major heat leaks, I expect there would be little benefit in doing it prematurely, although it does make a guy feel a lot better when it "looks good". The one exception might be if the material has a limited lifespan, which is often the case with refractories. If so, yeah, I'd do it soon.

I remember how proud I was of the tilting reverberatory furnace I built when it was finished. Really nice to look at, but quickly degraded due to the use of a serious amount of flux. I ended up patching, just as you did. Wasn't pretty when finished, but it restored the function, which was my objective.

In any case, I've followed your exploits with considerable interest, so please continue to share your experiences.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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steamin10
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Re: Patching Up a Furnace

Post by steamin10 » Mon Apr 04, 2016 3:04 pm

Generally what Harold said. A furnace is a working tool, and can be ugly as all , but serves a nasty function, and sacrifices itself with use. It is the service, and not the beauty we require, and that goes against typical attitudes of people who like paint and eyeshine over function. So rustic serves, and pristine is an ornament, useless.

Anything with sodium silicate will skin (paint additive) and unlike my homemade concoction, slow the drying. One incarnation of mixes I used included portland cement for a binder. It so happens heat works against this, the fireclays are a better choice.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Wed Apr 06, 2016 9:33 pm

Well it is staying ugly. We are going to do a couple of firings mid month to do an aluminum casting and a couple of bronze. We will know more then
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Sun Apr 17, 2016 9:18 am

Yesterday was the big test.

Two fellow modelers needed castings so they came over to help me cast them.

We did six castings with the furnace running flat out for over two hours. Burned about 10 gallons of oil (total cost still zero as I get it free from the high school concession stand). This is the hardest and longest I have ever run the beast.
DSC_4035.jpg
This is after it cooled over night
DSC_4037.jpg
the walls are rough with a different texture than before but the big cracks did not open back up. The top ring which is made up of the cement and the fireclay held up well.

Time will tell if the patch holds. If I can get another year out of a little labor and a 13.00 expenditure, it will be well spent.
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

Harold_V
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Re: Patching Up a Furnace

Post by Harold_V » Sun Apr 17, 2016 3:16 pm

Looks like the prolonged firing fully vitrified the patch. Reminds me of the outer surface of a well used crucible.

Looking good!

H
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Pipescs
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Re: Patching Up a Furnace

Post by Pipescs » Sun Apr 17, 2016 9:04 pm

Looks like the prolonged firing fully vitrified the patch
So, I take it I should leave it alone and not scrape it away?
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

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