Yet another keg furnace

In the construction industry, I have noticed the use of portable vibrators which were cylindrical shaped, mounted on the end of a wire/cord, used to settle concrete into the forms.
The contractors in their typical off-color vernacular called these things "big dick" and "little dick". Lets assume they were referring to someone named "Dick", perhaps the owner of this equipment (sarcasm intended, but lets keep it clean).

I will have to give that a try on my next lid.
I want to make a domed lid for my new furnace, since I don't think my flat lid is going to survive long.

Its like Mark says, if you make things into a wedge or arched shape, then theoretically even if it cracks, you can contain the material.
I have noticed this effect on my large (first) furnace where there are a number of cracks in the refractory, but when I made a second tuyere in the furnace to test a dual-burner design, it was like chiseling through granite, and was difficult even with an air chisel.
As long as the refractory does not crumble, then you can pretty much patch it indefinitely, and a good 3,000 F (+ -) refractory that is not over-watered will not crumble for a very long time.
Patching any defects as they occur slows down the degradation process greatly.

I generally patch/close all cracks as they open with a little ITC100 or 200, since it only takes a tiny amount when the cracks first appear, and it seems prevents the cracks from propagating into much larger openings.
I had to add a metal band around the top of my first furnace to prevent it from cracking at the top.
Furnaces heat up at the top first, since the hottest part of the flame and a much more complete combustion is located, and then the heat radiates downwards.
The bottom of the furnace never seems to be as hot as the top, I think due to the cooling effect of the ambient temperature combustion air introduced, and also the cooling effect of the fuel spraying (for those of use who use spray nozzle burners).
So the top of my furnace was expanding much faster than the bottom, and the refractory was just splitting open at the top.
The steel band at the top stopped all of that.

The Stanley Steamer boilers were wrapped in piano wire, and they could withstand thousands of pounds of pressure, with no Stanley boiler ever failing other than perhaps a tube failure, which is not a major safety thing.
I may wrap the exterior of my new furnace with a layer of wire, maybe at the top only, or maybe a steel band.

I have heard the argument that steel expands differently than refractory, but that does not seem to be a problem with the steel band I added to my old furnace, and indeed the old furnace would not have survived without it (it is still functional to this day, but is a very high-mass furnace). Without the steel band, the cracks at the top of the furnace were opening up to perhaps 1/4" wide.

Edit:
In the past, I have sprayed a couple of layers of ITC-1oo on the interior of the furnace and lid, and that really seems to help reflect heat from the furnace wall back into the crucible.
Lately, the price of ITC-100 has skyrocketed (like many things these days), and so it is not so economical to coat the interior with it, since the entire refractory lining can be replaced for perhaps less than the cost of a couple of quarts of ITC-100.

 

A lot of years ago I built a pump filter combination that resembles what is described in post 14. I have plans to use it in the near future but it will require some minor repairs. I plan on building my used oil storage in much the same way as is described in post 14.
I originally built this pump filter for on sight oil recovery. At that time I was using 2, 55 gallon drum plumed together. The first was the sump and gravity filter, the second was built the same way but was insulated with fiberglass. It was vented and had an electric water heater element in it that could be turned on to bring the oil to around 250 F to ensure any remaining water was boiled out.
I originally used the oil to heat a house and barn with a home made boiler set up. The burner used a 100 P.S.I. spray nozzle with an electric heater on the nozzle. It would start easily with the electric spark igniter. The preheater of the oil was probably to large for the heat surface and it would cause scorching of the oi,l that led to frequent clogging.

Joe

 

I think the small effort to recycle used oil is worth it....messy, but worth it and the cost of filters etc is small compared to the purchase of the fuel. I'm more interested in used cooking oil than sump oil, it seems to be much cleaner oil to handle and I understand it's considered much less toxic from an EPA standpoint, nosy neighbours notwithstanding. Modern engine oils seem to have a lot of synthetic components and I hear they are harder to burn and can cause problems for burners.

 

I have not used any waste motor oil.
Instead I have always used diesel since it is clean, consistent, water-free, readily available at most gas stations, and until recent years relatively inexpensive. Farm-diesel is supposedly cheaper than automotive-grade diesel, and some use farm diesel, but I don't have a source for that.

One of the problem with waste oil seems to be the heavy metals in it, but all combustion engines burn some level of oil from their crankcases, and the fumes are what you breath when you drive down the highway/road.
Then again, cancer rates are pretty high in this country (got my dad and several relatives), but I am not sure that could be attributed entirely to engine fumes, and indeed it could be genetics only.

Not wanting to find out the hard way, I have avoided using waste oil, but I have accumulated some waste oil, and would like to get rid of it.
The waste oil I have is all used synthetic motor oil, and a test of pouring it on a campfire shows that it seems to burn very well.

I know some who use diesel only, and others use either 100% waste oil, or a mixture of 10-20% diesel to waste oil.
I would guess that waste oil would light pretty easily with 20% diesel added.
I have heard it both ways, that waste oil burners much hotter than diesel, and from others diesel burns hotter than waste oil. I would guess that they both have roughly the same heat content, and both probably burn at similar temperatures.

As far as fumes, I would avoid standing downwind of a furnace running on waste oil.
I have a powered respirator that pulls air from indoors, so I will be using that if I decide to burn waste oil.
I also wear a respirator when burning diesel most of the time, since I prefer to err on the side of caution. It can be difficult to cure cancer, and even trickier to figure out what causes it; but why take chances?

I have run across several people who burn waste oil to heat buildings, using specifically designed waste-oil heaters, and they heat large warehouses and such for very little cost other than the purchase, installation and maintenance costs (assuming they have a source of free waste oil).

I have also known some who burn used vegetable oil, and from an environmental standpoint, that seems to be quite safe (even then I would not stand around and breath a lot of combustion products from it). Commercial-grade vegetable oil is what I specify in large electrical transformers since there does not need to be any containment due to spills from a hazardous materials standpoint (it won't hurt the environment, and technically you could consume it and fry food in it). The problem with vegetable oil around here is that it is closely controlled, and all the storage containers behind restaurants are locked. I think the recycle folks have a lock on the vegetable oil recycling in the area.

Vegetable oil would have to be strained to get the solids out, but the solids would not be hazardous unless they were allowed to rot and become a bio-hazard.
I am not sure if vegetable oil would have some amount of water in it, say from cooking frozen food, but I would assume not since the oil would be hot enough to boil off water.

 

Hi Pat, I would hope that if the oil air mix is burning right, the flame temperatures will decompose anything seriously nasty in the oil (aren't toxic organic chemicals burnt to dispose of safely?). That said I do get an orange-brown ash around the furnace lining and this would be expected and must contain residual contaminants. The anecdotal talk about burning synthetic oils being hard to do comes from the waste oil heating guys, maybe in a furnace it's easier to do, I haven't tried it yet.

Anyway the lining is in: It's sold by an Australian company: Refractech and the price was good, the country of origin is Malaysia. 16LCCF has a maximum service temp of 1600 deg C. I suspect it's a calcium aluminate based refractory which is made by melting lime and bauxite in a furnace and crushing the result. A big thanks to Kelly, the use of a vibrator really saved the day and made the cement flow well enough that I didn't have to ram it in: it just liquified and flowed. I was able to stir it with steel rods to ensure a uniform consistency as it flowed about like normal runny wet cement. There was a small gap in the tuyere formwork that allowed the tuyere tube to completely fill behind my foam rubber plug and I didn't spot it until at the end of the job. It didn't want to dig out until the vibrator was used and then came out easily. I used a DC motor with an out of balance steel weight and powered it with a rectified filtered variac power supply that let me tune it for best performance....beautiful!!!. The whole thing sat on a doubled up foam yoga mat which allowed it all to move around with the vibration.

 

I'll remember the paddle for next time, I have a large drill that would be ideal. It's a dense castable 41% silica and 55% alumina, although that bit is misleading as some alumina would be chemically reacted with the lime to make the cement. There's a lot of pink/pale brown 8mm aggregate which I speculate is crushed bauxite. Silica has pretty low thermal conductivity and the alumina conductivity is a fair bit higher. Mechanically it's an 80 MPa concrete which is about four times stronger than portland cement based concrete and after firing it drops to 60 MegaPascals compressive strength.

 

Mark-

It looks like the furnace refractory turned out well.
I am going to have to try the vibratory thing next time I cast refractory.

 

There's no doubt it will be inefficient in terms of heat loss, I hope to compensate with faster melts in line with the original unit. I learned on Sunday that furnace was made in 1958 so it's having it's 60th birthday this year. The reasoning behind the design was that it was cheaper to burn extra fuel than it was to pay the operator's wages.

Kelly's advice was spot on, the vibration was key to getting a decent result. The only uncertainty is how well I blended the concrete mix before installation, I did use a 1/2" steel rod to stir it around in situ which was only possible with vibration.

 

Here's some pics of the interior of the furnace concrete after the PVC form work was removed. It looks pretty uniform and tightly packed, in one of the photos you can see how deep I was plunging the steel rod to try and mix up the concrete during the vibration phase. It's quite strong: I used a silicon carbide brick intended for rubbing down concrete bumps and this stuff was rounding off the corners of the carbide brick fairly quickly. All of the form work was stuck fast as the concrete got into every tiny gap as a glue: nothing came out willingly and some hammering was necessary which the refractory withstood easily, it's tough stuff.

 

It looks good.
Time to melt some metal.

 

I'll have to make a plinth/base mould in styrofoam and some sort of partial lid to cover the bore when casting the lid in situ to get a good seal in use.

 

Looks great! Air cure as long as you can and heat as slowly as you can bear.

 

Following the manufacturer's guidelines.

 

Thanks OIF (Old Iron Farmer), I'll have to hassle the manufacturer some more about curing. Their website is lacking a bit of data so I have to email and ask: hopefully it won't be like the last furnace which was curing for about 15 years before I had a chance to use it.

Hi Kelly, I can report a few minor issues now: the cement was packed very tight so the rigid PVC had to be cut out to remove. In future, I'll make form work out of easily removable stuff like waxed cardboard and styrofoam. I did a crucible lifter test with my existing equipment and it's close but it fits past the crucible and grips fine.

 

Very nice work Mark. It looks like your efforts have paid off. I'm glad that pulling the form out didn't do any damage even if it was tough to remove. Trying to muscle something with your arms down in a hole is pretty awkward. Imagine trying to drill through that stuff! I had to re-form the tuyere in one of my furnaces once. It seemed a wood rasp would do the trick. After a bunch of strokes it appeared to be plugged up but in fact the teeth were gone! I ended up using a hammer and chisel. I got it where it needed to be but it was difficult and not pretty.

Pete

 

It was a bit scary: I ripped a hole in the middle of the chipboard disc at the bottom trying to extract it and fortunately the curved keg base let me smash part of it and extract it all. I had a short stainless 4" pipe up the tuyere with some 4" bore PVC over it to contour to the bore curve: the cement got in past the tape seal and glued the whole mass together. I tried grinding with a 1" wheel but it was tough, then I used a long file by hand to groove the stainless tube and then split with a prybar and 4 kilo hammer (wearing safety gear for any steel splinters). It took hours and finished with using the prybar like a cold chisel to knock off the tuyere dags before smoothing with the carbide brick. The hard part's done and the concrete seems to be full strength if my efforts are anything to go by.