Ribbon Burner Build

[kraythe]

Author's Note: This thread details a large project as it develops. If you wish to do the same project, I would highly encourage you to read the entire thread first. If you don't, you might find yourself missing lessons learned.


So it is time for me to go from pipe oriented blown burners to ribbon burners. I have heard so many good things about their efficiency and heat output that I thought it was time to make the new leap since I am building a new forge anyway (the old one has been too badly damaged by borax).

So I will post the build in this thread. I will continue to edit the first post if possible to add more information and then reply to the thread to let people know there is new stuff. If that isn't possible the replays will contain the new content.

The burner is based on a bunch of research into the ribbon burners topic. It will be a 4"x5" burner made from mild steel tubing and Kastolye 30 refractory with stainless steel reinforcing needles at a 5% weight ratio. The burner will be coated on the hot face with ITC-100 to reduce heat absorption and hopefully prolong the life. The burner will power a forge that is roughly 9" x 7" x 10" in volume at current plan. The burner will be installed in a hole in the Katolte 30 hot face of the new forge and slipped through the Superwool insulating layers and mounted on the metal shell.

To to start, I take 10" of mild steel, 1/8" wall tubing and mark it up for cutting in half. I also mark out the square i will remove for the burner hot face. This steel tube will form the plenum which will be pressurized by the gas/air mix.


After cutting the tube in half, I put it in a vice to start cutting out the center. I want to leave an L edge inside the tube so that the seal with the castable refractory will be better. I will eventually add insurance with a bead of high temperature furnace sealant just for good measure.


A 4" grinder with a cutting wheel makes short work of the center.


Notice that i overshot a bit with the cutting wheel. I will weld this gas tight later.


You can see the inside shape of the tube here. Note the landing L shaped area.


Now its time to cut the remaining 5" of tube along the corners so I get 4 walls. On two of these walls I will reduce the tube to 4" in length to make the caps for the ends. I will grind these flat so they cap fairly well. It need not be perfect as the weld can fill in a bit but you don't want it too far off or you will have some creative welding to do.


Now I put the whole thing on the drill press and center punch the exact center. Then I set up a bimetal hole cutter and clamp it down. Clamp it really tight as the vibration is fierce. Use cutting oil and remember if something goes flying don't try to catch it, just get the heck out of the way and cut the power to the press. A drill press has way too much torque to stop something by hand.


Now I take the remaining two separated walls and grind them so they will fit in the tube. These will form baffles that will cause turbulence in the gas/air mix and help it completely mix throughly. These baffles don't need to fit perfectly as they are not needed to be air tight when welded. So don't spend a lot of time cleaning them up with a grinder.


Now that the baffles fit I have drilled out the baffles to make a large number of holes. The gas air feed tube will be a 2" diameter pipe nipple and the holes drilled in the plates should have as many holes as possible to prevent constricting airflow. I might actually drill some more holes before I weld them in. The holes should not be aligned with each other as you want things to swirl around turbulently. The plate with the holes on the side will be closest to the feed pipe and the plate with the holes in the middle will be furthest away.


The only other piece for the plenum, which is not shown, are some angle brackets for mounting to the shell and the 2" black iron nipple that will be the feed pipe. Next time we will weld this together and check it carefully for gas tight welds.

All comments are welcome.

[SoCal Dave]

More pictures. Keep it coming

[kraythe]

OK, time for the second phase of the build. I decided that there were not really enough holes in the baffle plates so I set about drilling a bunch more, still trying to keep the holes from lining up. As you can see, I drilled a "hole" bunch more. They don't have to be all lined up and everything, no one will see it when the ribbon burner is done without taking the thing apart (and that will require a hammer and some force). So here is the setup in the drill press and the result.


Once I had the baffle plates it was time to install them in the plenum. I used 3/4" OD square tubing scraps to space the first baffle plate away from the feed hole. Then I laid the plate on the tubing and centered it in the plenum. Use the plate with the side holes closest to the feed pipe so the air must make a 90 degree turn.


Next I gently tack welded the plate in position then scrubbed the tacks with a wire brush and then pulled the alignment tubes. I just barely tacked them to hold them in place so I don't accidentally weld the tube in the plenum. I went over the tack welds again making them stronger. This is all the welding you really need to do as these won't be under stress really. I probably even overdid it but better to be safe than sorry. You can also see the penetration on the sides to show we have a good tack.


For welding I used a Lincoln 180HD welder set up for flux core. I used flux core because I don't have to meticulously grind everything which is often necessary with MIG.

After tacking , I took it back to the vise and used the grinder to make sure that the plate is shorter than the two sides. If there is extra space on the end, that is no big deal for the air flow but if it is too long then you will have a problem putting on the end caps.


After I had the first one in, I repeat the same process for the second one, first spacers, then lay in, then tack then grind. Now both baffles are installed.


More in the next post.

[kraythe]

Ok, on with the show!

I thought I might take a moment to mention safety gear. I almost always wear gloves in the shop. I only don't wear them when working around rotary machinery like a drill press. I use cheap Black Stallion TIG gloves for normal work. The fit is good and they are only about 10 bucks at my welding supply. For grinding, do yourself a favor and get a respirator like the one shown below. They are cheap from home depot. Without them you will be sneezing out black snot and coughing up black metal. That can't possibly be good for you so wear a respirator when grinding. I also wear eye protection at all times in the shop.


Now it is time to put on the end caps. I lay one of the caps on the top and tack weld it in place.


Now that it is tacked, I go over the edges with the flux core. In retrospect I wouldn't have used the walls from the extra tubing for the end caps. On the edges where the metal is thin, it is really easy to blow through the metal and spend an hour or three filling holes. Major pain in the posterior. However, although it looked like a dog's dinner for a bit, I got the holes filled and welded.


After I ground off the welds a bit, I went over them with the OA torch in my shop. I have a Victor Journeyman High flow torch that could cut through a battleship deck if I had the right tip. In this case I used a number three welding tip. I took a pass over all the welds with the torch to see if there were any voids or pinholes. I had a rod in my hand to add extra weld material as needed. The result is a nice air tight weld. The result of both end caps being welded on is shown below.


Its worth noting that the OA torch is probably the most dangerous thing in my shop. Please, if you don't know what you are doing with them, get a class in them. They can explode without even a spark if you do things wrong. They are supremely dangerous. If you have a TIG gun then 1, I am jealous and 2, you can do this with the TIG setup.

Ok now here is my son testing the baffles and plenum. He put a shop vac in blower mode and clamped the plenum to the table. The air pressure should feel pretty even across the whole face of the plenum.


Now that we have the main plenum sealed we will tack on some mounting metal. This metal will also be used to set the depth for pushing the plenum in the castable mold later so we measure to make sure there is 3/4" of clearance between the metal supports and there bottom baffle. Calipers do the job nicely and we can transfer that to the outside.


For the metal supports, we drill some holes then clamp one of the supports to some tubing to make it perfectly 90 degrees to the plenum and tack it in place.


The plenum just happened to fit perfectly in the slots in my welding table (its strong enough to hold a car if you could get it up there) This made it easy to make sure the other side would form a flat and level bond later to the outer shell of the forge. So we tack welded on the other side. If you don't have a car capable welding table with slots, any two pieces of good solid metal or tubing that is straight will work.


Now we are almost done with the plenum and it is really starting to look like a great ribbon burner. Next time we will be welding on the feed pipe and then preparing the mold for the castable refractory.

Stay tuned.

As usual, all comments are welcome.

[SoCal Dave]

Thanks, like the progression of the pictures. Looking forward to more of the assembling.

[kraythe]

I am on day three on the build of the ribbon burner.Now that the plenum is taking shape I am debating about some things that perhaps could have been designed better. I am a bit concerned about the adhesion of the Kastolyte to the burner but we will go with it and see how it comes out. If the cast doesn't come out the way I want, we can still adjust the burner and try again.

What I need to do now is connect a feed pipe to the plenum. I have researched this and have seen other builders use a black steel pipe nipple as the feed pipe. Although this works, the metal to weld against is very thin so I opted to go with a 2" black steel straight coupler instead. This will give me much thicker metal to weld to. I just happened to have one lying around in my scrap bin.


I would like to pass on a word of caution here. Make sure you test the threads in the pipe before welding it in place. You will feel exceedingly silly if you weld it and it won't thread later. I checked with a spare pipe nipple I had lying about.


You might have noticed the coupler had some holes in the side. I used these before as they were tapped for set screws in an old burner. So the first task here is to fill the holes gas tight. My welder makes short work of that and then I put the coupler in place over the feed hole. Now it is time to weld it in place. But first, on the advice of a friend who is a pro welder, I preheated the pipe. He suggested at least 200 degrees and I am sure I exceeded that. Then I tacked the pipe in place.


Next I welded all around the pipe and then made sure the threads still worked with the scrap black steel pipe. The flux core did a good job but slightly undercut the pipe's steel. After welding, I power brushed it off (wire wheel chucked in a drill is LOADS safer than one chucked in an angle grinder) and then I welded a fill pass over the fillet weld to make sure it is gas tight.


Now it is time for some wood work. And a bit of humor I might add. First task is to transfer the outer dimensions of the plenum to some scrap 3/4" plywood with a pencil, then I measured the thickness of the remaining edge with some calipers and transferred that to the drawing and finally I split the empty space in the plenum with a 1/2" grid. I decided to put burner tubes every other intersection in a checkerboard pattern. This left me with 14 tubes. Note that i didn't put them more densely because you could run into a problem where there isn't enough castable refractory between tubes to hold adequately and the result would be a cracked burner.


Next i drilled out some 5/6" holes in the intersections where the burner tubes are to go. Then I cut some 5/16" dowels so that they penetrate all the way to the bottom baffle plate in the plenum and then slotted them in. I now cut the walls to serve as the dam for the castable. Here is where the humor comes in. My shop is set up to do precise cuts on metal but my wood tools are laughable. I just have one little jig saw and a hand saw. So my dams didn't fit perfectly but that might actually be a benefit in the long run.


Now its time to mix the castable. I used a drywall mud pan to mix small amounts and some scrap steel to stir. It should be quite thick, almost like peanut butter. For maximum strength I put in a couple of handfuls of these tiny stainless steel reinforcing needles you can get at the Hi Temp refractory store on eBay. Meanwhile my son brushed all the flat surfaces with vegetable oil and dipped the rods in the oil as well. This should help with separating them from the refractory later. Its worth noting that we didn't use crayons as some others have done because of three reasons. 1) We didn't want the mess of the crayons. 2) The wood dowels worked well and will burn out cleanly if need be. 3) My 6 year old daughter would kill me for wasting crayons like that.


Finally we were ready to pour. We put the refractory right on top of the dowels and picked up the whole apparatus and smacked it down several times to get the refractory to fill the spaces and settle. Second we inserted the plenum and we quickly found out we had forgotten Archimedes in his bathtub. The metal of the plenum displaces some of the refractory and we ended up having to quickly scoop some out and resettle the concrete then try again with the plenum. We shoved it down and tapped it down with a hammer. Then we clamped the whole thing to the table and began tapping the forms lightly with hammers. The idea is to get the refractory to settle around the plenum via vibration; to go over the lip of the plenum and then settle on top of it to a depth of 3/4" and thus form a strong block.


Now all we can do is wait. It should be 3 or four days before we can take the molds off. In the meantime I have some ideas for refinement in the plenum that I am debating exploring Stay tuned for that story and a potential second ribbon burner cast soon.

[kraythe]

While we wait on the castable to dry I thought I would address a couple of questions that might come up and do some fun math. Everyone loves math right?

First of all, finding 2" diameter black steel pipe fittings isn't so easy at least where I live so some might wonder why i didn't use galvanized instead. The reality is that galvanized can be bad new in a high heat environment. Although its easy to find, if you try to weld it without a lot of protection you are in for some nasty heavy metal poisoning. The galvanized coating burns off at a much lower temp than welding temp and then if you breathe that stuff in, its bad news. You can use galvanized to feed fuel/air mix to the burner but don't weld it. If your feed tubes get hot enough to off gas the galvanization then you will have other, more serious, problems than galvanized fumes. Weld to black iron and then couple to galvanized if need be. The black iron fittings of that size can usually be found at plumbing supply stores.

Another thing you might consider in this build is a Normally off solenoid rated for propane. The plenum of the burner is pressurized gas/air mix and if you suddenly lose power you can have a back flash on your hands. As the pressure drops in the plenum, the flame front backs up into the plenum and burns back towards the propane source. A solenoid will cut the gas if power is lost. However these suckers are a bit expensive so you might opt to go without. If you do, then make sure that you have a ball valve to turn off the gas. The chance of a massive explosion is pretty small though. (legal disclaimer, I am not an engineer and you use this information at your own risk). Propane has to have a specific stoichiometric mix to burn and when the flame front hits the propane supply tube and has exhausted the air, the flame will simply go out. This is NOT like acetylene in an OA torch (remember me telling you its the most dangerous thing in my shop?) An OA torch can flash back right into the bottle so if you don't have flash back suppressors you are asking for a Darwin award. It doesn't hurt, however, to use flashback suppressors in a propane line but it probably isn't necessary. If you want to use them, make sure they are rated for propane.

Finally lets do some math. The Plenum of this burner is pressurized by the flow of fuel and air into the plenum through the feed pipe. The baffles foes things to get turbulent and encourage complete mixing. However we can think of the whole system as a big pressure feed pipe. The area for the circle is described by the mathematical equation π r². So the area of the feed pipe is π square inches. Each 5/16" diameter burner tube has an area of 0.07669 square inches. This means that it would take π / 0.07669 tubules to equal the area of the feed pipe or just a bout 41. Given that, the pressure must increase in the plenum since it can't push out as much air as being pushed in. At the same time you have to be sure that your blower can handle the back pressure on the burner or the fuel/air mixture will try to back flow into the feed pipe and then potentially into the blower and then ... well you get the idea. So although the plenum must be pressurized, you want enough holes to make sure the pressure doesn't back build. In my case I have 14, so it should be ok but we will see when we fire it up. Id actually like to have a few more but we learn by doing and I am constricted by that inside edge of the tube.

When it comes to the baffles we do the same calculation and since we are using half inch baffle holes, we find that we need at least 17 holes in our baffle plates to avoid restricting flow (π / (.25 * .25 ) * π) = 16.02 . Fortunately I have more than that in both baffle plates.

[DClaville]

Thanks for posting this i have for some time been thinking about trying a ribbon burner at some point and now i have had some answers to my thoughts
keep up the good work

[kraythe]

OK we now have a semi-cured castable block. The other day I took off the side forms (after about 36 hours curing) to allow the side to cure better. Now its time to take off the bottom form.


After trying to carefully tap a chisel in the seam between the castable and the burner, we realized that the dowel rods were holding the form on it. So we thought to drill out the base to get the dowels off. It somewhat worked but the bits didn't track down the center of the dowels and so it left two problems, off center drill marks and partial dowels. It appears even the wood drill bit cuts through the refractory well, which is bad. So drilling is not a good idea.


Here you can see that not all of the refractory has cured, The chisel is pointing to the darker castable that hasn't cured. You could put it in your wife's oven to finish it for a couple hours but that could lead to bodily injury so I can't recommend it.


We still had dowel remnants so we thought to burn them out with an OA torch. We got a nice birthday cake effect but the results weren't satisfying.


The tops of the dowels burned off but I couldn't burn lower. You have to remember that the OA torch produces a 5k degree flame which exceeds the castable's rating. So we piled up some insulating bricks, shoved an old venturi burner into the pile and baked it until it stopped smoking.


Prior to putting it in the brick pile forge, I had begun to think I had made a mistake with the dowels. Now Im not so sure. Baking it cured it fully for sure. I could have possibly wrapped the dowels in wax paper to allow us to pull them out the center and burn only the paper. However, since i didn't i have some damaged jets so we will see how it works out later.

The next step was to use a shop vac in blower mode to facilitate removing the remaining smoldering wood and ashes. Make sure you keep track of flying embers and put them out to avoid starting a fire. Then we used a dowel and gently tap it into the jets to make sure they are cleaned out.


Now that we had the burner cleaned out, we needed somewhere to attach our blower to. So we used a hole saw and cut out a 2" hole from a piece of 1/8" metal. Placing the wood underneath allows you to drill through without hitting the press table and also clamp it down tightly. We welded this plate to a 2" pipe nipple and now we have a modular blower plate. For temporary testing we won't drill it and bolt it but just use clamps.


Now its time to fire it up and test it. We put together a set of 2" galvanized pipe to attach to the burner and blower. Galvanized is fine here because if this gets hot enough to strip off the galvanized coating you will have MUCH bigger problems (such as personal safety). We set up the burner on the floor pointed in a safe direction. Then we used a simple propane jet to inject the propane and then started up the blower on low. Using a sparker we lighted it up and ... it lit! Oh boy did it light.



The burner puts out a huge amount of heat. Heating a 1/4" square rod in open area to orange in less than 30 seconds. It is a serious appliance that puts out serious BTUs. If I put this in a forge now, it would definitely make my old blown burner and definitely the venturi burner look like little candles.

We had to close the blower almost all the way to get the flame front to stick to the nozzle. That tells me the pressure inside the burner is way to high. That tells me the holes are too small or to few. Also the damaged jets were merging flame and creating a big yellow plume. This means that they aren't working perfectly. In retrospect, we wouldn't have used the drill but simply burned it completely. Doing the nozzles with crayons or candles is just too messy and would require us baking it in the forge anyway. Furthermore, since the burner is square, that makes putting it in a forge or furnace tricky. A slight misalignment of the form will make a nightmare fitting situation. However, if the burner was round, any potential problem with fitting could be solved with a drill and a large hole saw.

We have definitely learned a lot on this first ribbon burner project. I plan to put that knowledge to use and do another burner with some modifications. Please stay tuned for that thread.

[SoCal Dave]

Thanks for the update. Very informative.

[mudbugone]

Very interesting burner.... You mentioned a round burner instead of a square ...any more thoughts on that ?

Since you seemed to have such an issue with the wooden dowels... How about SS tubes and leave them embedded in the casting ? Is there excessive heat where the flames exit the cast burner tip ?

Would skewing the tubes into a spiral direction create a swirling flame (if using a round tube) or is it preferable to have the flame feed straight into the forge chamber ?

I'm only asking questions that popped into my mind as I read the buildup on this burner. I'm assuming this type burner would be more suitable for a larger size forge.

Please continue to update this thread... I've not seen this type burner discussed before and it appears the conversation on it has stopped.

EDIT--- I found the thread on the round burner and will read thru it too...

[HWooldridge]

Deleted.

[eric sprado]

We Call them crayon burners in the Northwest because most guys use CRAYONS for the mold. They melt right out!! There are some pretty complete tutorials on NWBA site for the burners.

[kraythe]

Very interesting burner.... You mentioned a round burner instead of a square ...any more thoughts on that ? Since you seemed to have such an issue with the wooden dowels... How about SS tubes and leave them embedded in the casting ? Is there excessive heat where the flames exit the cast burner tip ? Would skewing the tubes into a spiral direction create a swirling flame (if using a round tube) or is it preferable to have the flame feed straight into the forge chamber ? I'm only asking questions that popped into my mind as I read the buildup on this burner. I'm assuming this type burner would be more suitable for a larger size forge. Please continue to update this thread... I've not seen this type burner discussed before and it appears the conversation on it has stopped. EDIT--- I found the thread on the round burner and will read thru it too...

If you angled the jets the effect would depend upon the shape of your forge. I honestly don't think it would do much. Ribbon burners don't leave a lot of extra gas to get burned in the forge like some other designs. They are efficient. Running a ribbon burner at 2 psi will give you the heat of 10 psi of a normal blown or venturi burner.