Home Foundry

[GreenTwin]

I have used several methods for the cap on the back of the burner tube, where the air and oil lines enter.
The latest method I used was to weld up a cap, and use a piece of thin plumbing joint stainless steel wrapped around the joint to secure it.

This was actually a drip-burner test, not a siphon nozzle, but the burner tube and cap construction are the same/similar as I would use on a siphon nozzle or pressure nozzle.

 

[GreenTwin]

Here is an earlier siphon-nozzle design that I tried, with spin vanes cut into the end of the burner tube.
The spin vanes did not have any effect on the melt, and I ended up cutting them off.

One think I liked about this burner tube was the three nuts that I welded at 120 degrees from each other, after drilling holes through the burner tube under each nut. I added a screw in each nut, and do a fine adjustment to center the nozzle in the burner tube.
I like this method of supporting the nozzle in the tube best of the several methods I have tried.

Be sure the nuts you use are well outside the tuyere, else the nuts and screws will not allow the burner to be inserted into the tuyere.

The nozzle tip is always about 1/2" inwards from the end of the burner tube.

 

[GreenTwin]

Here is an early version of a siphon nozzle burner.
You can see I added a section onto the burner tube to make it longer.
I think now days I generally make the burner tube 18" long, but I will have to check that.

And I used a rubber plumbing coupling to seat the cap to the end of the burner tube, which can melt due to the heat, so now I use a sheet of stainless wrapped around the tube and clamped twice to secure the end cap to the burner tube.

For my latest burner, I moved the PVC air valve to a remote location, again to prevent heat damage.

For the top photo, diesel enters the clear line, goes through quick disconnect, a ball valve, transitions to a black rubber fuel line, goes through an inline automotive fuel filter, goes into a needle valve, transitions to a piece of 1/4" copper tubing which goes through a hole in the end cap and runs down the burner tube to the elbow on the side of the nozzle adapter.
The copper tube is not fit airtight in the hole in the cap, since the combustion air pressure in the burner tube is low, and the small leakage at this joint does not affect the burner operation.
Some use steel brake lines, but I have more fittings that I can use with copper tube, so I use it.

The compressed air enters via the red hose, and is feed from the pressure regulator set at 30 psi.
The compressed air hose has a quick release, then a ball valve, then it goes into a piece of steel pipe that threads into the end of the siphon nozzle adapter.
The steel compressed air pipe is welded to the end cap. This pipe according to Delavan is a 1/4 NPTF, and its outside diameter is about 0.54".

The second pressure regulator feeds 10 psi air pressure to the fuel tank, and the fuel tank has a 30 psi safety valve, in case the pressure regulator fails.
One guy had his pressure regulator fail, and did not have a safety valve, so he blew open a fuel line fitting, spewed fuel everywhere, and started an inferno. This is why you don't use oil burners near houses, cars, or anything else valuable, and this is why you need a safety valve if you pressurize your fuel tank.

Other features of this burner which I like are the quick-adjust height support, which has a short hand lever which can screw or unscrew the burner from the vertical support, to adjust the burner height.

Another feature on this burner is a quick release to separate the burner internals from the burner tube, by unclamping the rather crude clamp.
This allows the burner nozzle to be withdrawn from the furnace at the end of a melt to prevent o-ring damage.
The rubber seal at the end of the burner tube is a slip fit, and there is no appreciable pressure on this joint, so it does not have to be very tight at all.

A better way to prevent overheating a siphon nozzle tip when the burner is turned off at the end of a melt is to leave the combustion air blower operating after you turn off the fuel ball valve.

Pressure nozzle burners do not have an o-ring, but I will still leave my blower on at the end of the melt with my pressure nozzle burner, to prevent cooking diesel onto the burner tip, which makes a varnish-like buildup.

Comments I have seen regarding a siphon nozzle burner are generally "Boy, that sure is complicated compared to a drip-style burner".
Yes, I agree, but if you have ever used a drip-style burner, and compared its operation to a siphon-nozzle burner, you would see why I go to the trouble of making a siphon nozzle burner.
The siphon nozzle burner is instantly controllable, with rock solid consistent operation.
Building a siphon nozzel burner requires a certain amount of technical expertise, and I have seen some who build them, but can't quite master it.
For those who are use to working on machinery, engines, and such, a siphon nozzle burner is not complicated.

 

[GreenTwin]

I have also used a gland arrangement to seal the compressed air pipe to the end cap, but generally I just weld the compressed air pipe to the end cap.

A gland arrangement allows complete disassembly of the various burner parts, and also gives you adjustment of the position of the burner tip relative to the end of the burner tube.

The fuel line needs a ball valve and a needle valve, so if you have a flame-out, you can immediately turn off the fuel using the ball valve.
You don't want to try and quickly shut off the fuel using a needle valve, and if you get the needle valve set correctly, you want to leave it in the same place, and use the ball valve for fuel on-off.

Edit:
Some things I learned about oil burners, after much experimentation.

1. Bigger is not better.
An oversized burner and combustion air blower actually run much cooler than a smaller properly sized burner and blower.

2. A higher fuel flow will operate cooler than a lower fuel flow.
For my furnace, fuel flows above or below 2.6 gal/hr run cooler than 2.6 gal/hr.

The idea is to introduce the maximum amount of fuel and combustion air into the furnace that the interior surface area can completely combust inside the furnace. There is a scientific term for this fuel/air ratio which I forget, but this ratio is critical if you are trying to achieve iron temperatures, minimum melt times, and the correct pour temperature for iron.
.

 

[GreenTwin]

As far as foundry suppliers, they don't take small orders generally, and they often sell in bulk.
So foundry suppliers generally will not talk to hobby folks (on rare occasions sometimes they will if they are having a good day).

I buy foundry materials in bulk, with "bulk" being defined as an order large enough so that the supplier does not hang up the phone in my face.

I have purchased from some foundry suppliers, and the second time I try to place an order, they don't respond because they don't want to waste their time on little orders when they could be making a large profit on a large order.
I can't blame them for what they do (ignore the hobby folks).

I normally don't reveal the regional suppliers that I use because I have to beg them to sell me materials, and if they were flooded with calls for small orders, they would probably stop talking to me.

The way I found suppliers is to do a web search for "Foundry Suppliers"; found some that were in the US, and started calling them.
I basically said "I am a hobby guy who needs a small quantity of (fill in the blank, ie: refractory, etc); do you have time to talk to me?".
The would either say "sure" or hang up the phone.
I purchased some things from the ones who wanted to sell small quantities, with small quantities perhaps being 75 lbs of ferrosilicate, 200 lbs of castable refractory, or 100 lbs of plastic refractory.

As I mentioned, I use Morgan Salamander-Super crucibles exclusively, and there are a number of sellers of these on ebay, which is where I purchase mine.

I fabricate my own pouring shank, lifting tongs, furnace, burner, and pretty much anything else I need for the foundry.
I make my own wood patterns, or 3D print patterns.
Sometimes I make patterns out of steel.
.

 

[GreenTwin]

This is the castable refractory that I use, which is called Mizzou.

I think the MSDS sheet goes with the Mizzou pdf file, but I am not certain.

It should be noted that the amount of water that you mix with castable refractory is tiny, which makes hand-mixing difficult but not impossible.
If you decide to add more water, you can easily ruin the refractory.
And as with all foundry material handling, one should wear a good respirator/industrial dust mask, to prevent inhalation of refractory dust, ceramic blanket fibers, sand particles, fumes, etc.

.

 

[GreenTwin]

An internet search for Mizzou turned up the following:

https://refwest.com/mizzouplus55bags.aspx
http://hightemptools.com/castablerefractory.html
I have no idea if either of these companies are reputable, so use at your own risk.
They are both in the US.
Shipping can be pretty extreme for refractory, so be sure to check on that before you purchase.

If the bag(s) get wet during shipping, or if you store them in a damp spot, then the refractory will set and will not be usable.
If you breath refractory dust, you will not be usable.

Don't purchase the refractory until you are ready to use it.
If you don't waterproof your cardboard forms, then the water in the refractory will cause the form to collapse, and you will have lost everything (I saw someone lose several hundred dollars of refractory this way on ytube a few years ago).

This is a very dense refractory, but it stands up to iron slag well.
Since it is very dense, it should probably only be used in thin hot face applications, such as a 1" thick hot face.
If you cast Mizzou 3" thick, your furnace will heat very slowly.
.

 

[GreenTwin]

When I make sodium silicate molds or cores (normally I use resin-bound sand for everything, but I have used sodium silicate bound sand for both molds and cores), I use 3%.
The secret to making strong sodium silicate cores is to not over-gas them.

Like many foundry things, I originally thought that more is better.
When making sodium silicate cores, using more than 3% makes the core very difficult to remove after casting, and they do not permeate the CO2 very well.

When gassing sodium silicate cores, gas for 5 seconds with CO2, and then immediately stop.
Any gassing over 5 seconds will ruin the core, and it will crumble within hours.

A 3% sodium silicate core gassed for 5 seconds works perfectly, and I have left unsealed on the shelf in the unconditioned shop for a year, and they were still usable.

Never put a sodium silicate core in a plastic bag filled with CO2.
The is the fastest way to ruin I core that I am aware of.

.

 

[GreenTwin]

I am following your foundry work with a lot of interest and great appreciation. I started casting aluminum a couple of years ago for my engine models which you can see here. Porsche 917 flat 12 engine
I would like to cast iron but my gas furnace does not reach the required temperature. I kindly take advantage of your experience to ask you for some advice : how did you make the Diesel burner, nozzle size, pressure, air blowing, etc?
What coating did you use in your furnace to withstand the temperatures needed to melt cast iron? . For my furnace I used ceramic fiber, but over 900/1000 degrees centigrade it starts burn.
Last 3 question, what% of sodium silicate do you use in the sand ?
I have a sticking and breaking problems to the molds, is there a release agent to avoid this?
Ceramic mold coating, can you tell me some brand of this product?
thank you very much

1. See info above for how I make diesel burners using Delavan siphon nozzles.
2. I use a 1" thick refractory called Mizzou, and it easily withstands iron temperatures, and is highly slag resistant too (see info above).
3. For sodium silicate, I use 3%, see my post on sodium silicate.
4. Sodium silicate is very sticky material, and it sticks to patterns worse than resin-bound sand.
I wax my molds to prevent most sticking.
Some use various pattern coatings that are silver in color, and I have tried this once, but don't know enough about it to say if it works well.
5. The ceramic mold coat that I use is called Velacoat (manufacturer info was posted by someone above, see ASK Chemical).
Sodium silicate begins to break down in water, especially at 3%, and so alchohol-based ceramic mold coat may also break down a sodium silicate mold or core.
I have never used a mold coat with sodium silicate, and am not sure if it would work.
If I had a bit of time, I would try it, but I am too busy with work for now.

.

 

[dazz]

2. Some use spin vanes near the end of their burner tube, and some do not.
I have tried both, and can't tell any difference, so generally I do not use spin vanes in the burner tube.
A commercial heating unit burner is discharging into a large combustion chamber, but for a foundry furnace, you are discharging into a space that immediately swirls around a round chamber, and so probably the reason a spin vane may not have an effect when used with a furnace.

I will try using spin vanes only because it is the easiest way to hold the burner nozzle.

3. It is easy to use a constant speed blower, and your idea sounds like it would work.

I have no idea how big the blower motor/fan should be. Trial and error required.

The fuel/air setting that produced the brightest luminance inside the furnace was about 2.6 gal/hr., and after I discovered that flow level, I compared notes with others doing iron work, and found that for the same size furnace, they were using an almost identical fuel flow level.

There seems to be an upper limit on the fuel combustion rate for a given size (volume) of furnace.

Cracks that are not filled will let a high temperature stream of hot gas get behind the hot face, and that can cause a lot of damage to the ceramic blanket.

I have thought about slightly pressurizing the space where the fibre insulation is to ensure there is air flow through any cracks into the furnace. Rather than cool the furnace hot face, the added oxygen may increase combustion.

I have seen one furnace build from lego-style individually cast refractory curved blocks, but they made the blocks about 4" thick, which is way too much mass for a furnace.

A concept drawing is attached. The actual bricks would be shaped to fit the allocated position. With CAD and a 3D printer, it will be easy to made bricks with complex shapes.

7. The aluminum foil is not a bad idea, but be aware, the back of my hot face is probably not much cooler than the face of my hotface, and so the foil would have to be behind enough layers of ceramic blanket to prevent melting the foil.
Iron furnaces run extremely hot.

Aluminium insulation is only good to about 200 deg C, so it would only survive if separated from the hot face with ceramic blanket.
Really thin stainless steel would work OK until the surface oxide changed colour and it stopped being such a good mirror.
I plan to use stainless steel for the furnace outer casing.


Dazz

 

[TSutrina]

I am just someone that view this site so I am only suggesting something. Lots of hobby people exist and they do need material. They could form a co-op to purchase material. The group could purchase in bulk and repackage it a local warehouse. Ideally be a corner of a small business builing with multiple small businesses so that they could rent/borrow fork lift truck owned by other tenant and maybe have use of their dock. The building is more likely to have the proper environment to keep the product dry. I visited a semiconductor manufacture in England that had space in a very old building that didn't have the environment needed. They built a plastic sheet enclosure within the building with the proper environment. So example humidity can be reduced within such an enclosure. Some equipment will be needed to do the repackaging and maybe sufficient co-op members live close enough to get together one or two Saturdays a month to do the repackaging. And need a person that does the receiving and shipping. This could be done by the small business that has the fork lift truck for a fee per order and a monthly retainer.

 

[GreenTwin]

I am just someone that view this site so I am only suggesting something. Lots of hobby people exist and they do need material. They could form a co-op to purchase material.

The problem is that some of the materials used in a foundry can be hazardous if the proper precautions are not used, such as commercial respirators, etc.
Every foundry product should come with a MSDS sheet (material safety data sheet), and the product should not be used without reading that sheet and adhering to its recommendations.
I think the safety aspects are what prevent many/most from creating a coop-type arrangement.

Some backyard casting folks take a casual approach to safety and material data sheets when casting things, but safety is priority #1.
If you are not doing things safely, you should not be doing them; that is the bottom line.

I like the idea of a coop, but not sure if the logistics of that could be worked out.
.

 

[GreenTwin]

There seems to be an upper limit on the fuel combustion rate for a given size (volume) of furnace.

I was told by someone who worked on commercial oil heaters for many years that the method of determining the maximum fuel rate for any give furnace is to begin with some low nominal fuel flow value, and adjust the oil and air to give about 4" of flame out the lid opening.
The combustion air flow is then increased until the flame is drawn back into the furnace.

The fuel is then increased again to give 4" of flame out the lid opening, and then more combustion air to draw the flame back into the furnace.

At some point, when the combustion air is increased, instead of drawing the flame back into the furnace, it will increase the flame size coming out the lid opening. This is the maximum fuel flow rate for the furnace.
I have not tried this method, and only learned it not too long ago, but next time I run my furnace, I am going to try it.
.

 

[GreenTwin]

A concept drawing is attached. The actual bricks would be shaped to fit the allocated position. With CAD and a 3D printer, it will be easy to made bricks with complex shapes.

One thing I have learned from my own furnace, and observing other's iron furnaces, is that melting iron is a brutal business, as far as the heat generated, the effect that iron-level temperatures have on the furnace hot face and crucible, the splattering slag, the very extreme expansion/contraction that all the components are exposed to, etc.
I have seen some folks transition from doing brass/bronze work into doing iron work, and the temperature difference between brass/bronze and iron is not that great (in my opinion), but the infrared energy coming out of a furnace at iron temperature, and the infrared coming off of the crucible required that shaded welding goggles, or some sort of shaded lens be used, else you will get sunburn in the eyes.
And with that much IR coming out of the furnace, you need full leathers, leather boots, heavy leather gloves, head cover, full face shield, etc.

And another common mistake I see when people try to pour iron is they do not use heat shields on their skimmer handles, pouring shank, etc.
Without a heat shield to protect the gloved hand, you will overheat the glove and burn your hand within perhaps 15 seconds, if your gloved hand is within 30" of a hot furnace or crucible.

As I mentioned, don't underestimate the IR coming out of an iron furnace.
I have had the black body of cameras 10 feet away start to get hot and smell when the furnace is opened.

And avoiding any moisture anywhere, such as in the scrap metal, the ingot molds, or anywhere else is essential.
The slightest microscopic amount of moisture on any surface, such as the dry surface of an ingot mold, can eject the molten iron right into your face/facemask.
I have 3rd had degree burns on my hands that prove this point.
I will link a video one person posted to highlight the moisture thing around iron pours.

But the point I was trying to make (I drifted off-topic a bit) was that spending a lot of time making custom fire bricks may or may not be productive.
If all the fire bricks crack after the second iron pour, then you are right back to patching with plastic refractory, and the question becomes why not just make the hot face from plastic or cast refractory in a thin sheet, or a thin cast refractory hotface?

.

 

[GreenTwin]

Here is an extreme case of a backyard guy I watched before I built my furnace, and he poured a lot of iron in his furnace.
He re-built his furnace perhaps three times, during the time I was following him, and learned a lot about what to do and not do with furnaces by watching his builds.
I will post a photo of the interior of my newest furnace, and you can see it is not nearly as bad as this one, but I don't have the large number of iron melts on my furnace either.

The material on the sides of the furnace is slag that has been splattered out of the crucible during the melt.
The crucible in the photo below is rather thin at the top, and that is ok as long as it is only thin at the top but otherwise still thick and solid elsewhere.

 

[GreenTwin]

This is my badly cracked hot face after about four iron pours.
This may look like a total disaster, but it is actually completely repairable/serviceable, since the Mizzou is still very solid, but just cracked.

I still use this hot face, and just patch any slight cracks with 3,800 F plastic refractory.

 

[GreenTwin]

Here is the rebuild I did on the hot face above, and it only took about 30 minutes to rebuild/patch.
With plastic refractory, I don't have long dry-out times, but rather just fire the burner on low for about 15 minutes, then 1/2 power for about 5 minutes, and then full power.

I have seen more than a few backyard folks go to great lengths to build a pristine furnace/hot face, and baby it, and obsess about a tiny spot of slag that shows up on the hot face. These folks generally never do iron work.
As long as the refractory has a high temperature rating and does not begin to crumble, then you can just patch it.

 

[GreenTwin]

Here are the insulating fire bricks installed around the hot face, after the rebuild.
I used a grinder (with a very good dust mask) to cut a convex surface on the bricks where they meet the hot face.
Insulating fire bricks are very soft, and easy to cut by hand if necessary, but they won't stand up to iron temperatures unless they are 3,000 F rated.

These are about 2,500 F rated. The price of insulating fire bricks goes up exponentially with temperature rating.
If you have to ask how much a 3,000 F insulating fire brick costs, you can't afford them, and I certainly can't (perhaps $10 per brick for the 3,000F was one quote I got).

The insulating fire bricks are lightly banded (not tight, since everything will expand when heated) using stainless bands.

I use a cast refractory extended tuyere, and am not entirely happy with it, but it does work.
I think an extended tuyere made from insulating fire bricks would be better, and let the bricks sit on the furnace steel base.

Two layers of ceramic fire brick are wrapped over this, and then a stainless steel shell.
The stainless shell ended up being the diameter of a 55 gallon drum, and if I had to do over, I would have just bought a stainless steel drum, instead of piecing together the sheet metal as I did.

The insulating fire bricks are not adhered to the hot face, to allow for rebuilds.

 

[GreenTwin]

This is what the interior of my rebuilt furnace looks like after seven iron pours, and I consider this to be a pristine and clean look, with no visible cracks.
I fill any cracks with plastic refractory prior to using the furnace each time, and if you do this, then you generally only have to fill a few very small cracks, and this seems to minimize crack propagation.

Even after the rebuild, I consider this hot face to be repairable and serviceable for many years.

I discovered that the art-iron foks use plastic refractory to patch their cupolas, and they generally never rebuild a cupola, but rather just pack new plastic refractory into the low spots before every use.
If I ever get to the point where I have to replace this hot face, I will add a layer of tap to the inside of the insulating fire bricks, and just pack on 1" of 3,800 F plastic refractory, so that I don't have to build forms, mix refractory with water, cast it, etc.

Plastic refractory is like very thick putty, and you don't add water, but rather just hand-pack it into place.
You could probably roll out a 1" thick sheet of plastic refractory (like cookie dough), and then put wrap it around the furnace interior sides and floor.
That would give a more consistent thickness to the hot face.

I used the same plastic refractory to fill out the L-shape that I used in my lid, and cover the stainless metal, and that is the only modification I have had to do to the lid shown below.

The plinth below the crucible is cast from Mizzou, and I have several of these, at different heights, depending on which crucible size I am using.

When I have finished pouring the iron, I empty any remaining iron into a preheated (to perhaps 500 F) ingot mold, but I don't try and clean out what remains in the crucible. Crucibles are somewhat delicate, and they should not be stacked, dropped, or roughly handled in any way.
The slightest crack in a crucible will cause it to fail during a melt.

If you tap lightly on a crucible, it should have a ring to it if it is not damaged.
If the tapping caused a dull thud sound, the crucible should probably not be reused.
A crucible should be retired when it begins to get too thin.

 

[GreenTwin]

One thing to note is that when I first built this 2nd furnace, I installed a 4" wide stainless steel band around the hot face, near the top.
I think this was a mistake, and I think the steel band exacerbated the cracking of this hot face.

One thing that using a hot face made of sections would to is give controlled cracking joints.
If you have access to a good plastic refractory, cracking is a non-issue regardless of how you build the hot face, as long as you use a good refractory that does not crumble at iron temperatures.

.