Thinking of going to blown burners.

[HWooldridge]

H. Is that the Sandia recuperative style forge. I keep mulling over experimenting with one (one day). The heat from my 3 burner gets unbearable in 400 sq ft. It should also cut down on fuel cost at run the forge hotter. A win win win ..... if I can find the time.

Got any pictures/ info?

Yes, many years ago when the plans came out, I built three Sandia style forges for myself and a couple of friends. They worked OK but always needed tuning so I built a manifold and added a blower. I'll have to take some pics and post since I don't already have one on the PC.

[roy_tate]

This is a picture of the forge that Rob Gunter and sons used at the 2009 SaltFork Conference last october. http://picasaweb.google.com/Roy.L.Tate/SaltforkConference2009#5395250849539729714

Check the Saltfork web site for our 2010 conference! http://www.saltforkcraftsmen.org/). Click next to see more photos of the forge, or "view all" to view more coverage of the conference.

Roy Tate

H. Is that the Sandia recuperative style forge. ...

Got any pictures/ info?

[pkrankow]

On the recuperative forge, how long does the metal last getting dragon breath on it all the time? What is the metal used?

Phil

[Nakedanvil - Grant Sarver]

Robert: Don't change anything until you get it cooked out really good. Seriously, I've had the devil of a time keeping a cast one going until 100% dried out.

[Jymm Hoffman]

Thanks Phil for adding the link about my burners. I have been using this style burner since 1993. I started using the blower Grant plugged since around 2000 or 2001. I still have the first one, even after it froze up. I took the covers off and found that there are no bearings, just bushings. I lubed it up and have been using it since, that was probably 4 years ago. I just sold one from my stock to a neighbor that is a fabricator. He is building one based on my system. I have over 6 ready to run in the shop right now.

I just modified my first vertical forge today. It only had one burner and did not get as hot as I like. I had since built a vertical 2 burner, based on my other system, just turning the entire manifold vertically. That left a cold spot on the burner/manifold side. Today I put another burner into the single vertical forge, opposite the first one, both angled to get a nice swirl. I had help from my fabricator friend that had a pipe bender.

I also agree with Grant, they don’t run well when they are wet, even the blown ones.

Here are a couple of photos. There is a 15” diameter disc in it; it is now a frying pan.

[Nakedanvil - Grant Sarver]

OMG! You cannibalized R2-D2! Great looking forge!

[Jymm Hoffman]

Wait till I do C3PO

If you are thinking of a blown system, I highly recommend the blower Grant mentioned at Blacksmiths Depot. I attach them to the forge cart and have a light switch with a plug. I prefer the light switch to turn them on and off, hopefully you can see in the photos. I can also simply lift the forge off the cart and swap with another. The earlier photo of the vertical is on the cart that usually has my first 2 burner. The larger 3 burner can also be lifted off the cart, but it is a handful. I also set up the gas valve so that down is off, thus the light switch and gas valve are up for on, down for off and a simple safety feature. Blower should get turned on first, so start there and go up, then reverse for off, start at the gas go down to the blower...

Those blowers are great and a great price. As I was preparing to build several forges of my "standard" size (12" X 12" round shells,) I was searching for a good source of blowers. One they had to work and two be reasonably priced. I had tried another blower from a furnace that a friend had loaned me. It was readily available through Grainger, but cost about $165.00 ten years ago. Nor did it perform the way I needed it to, in other words, it was not strong enough. As I was developing the manifold based on previous experience, I admit that I was reluctant to buy a blower that I had not used and was about to give up. So I went ahead and spent the money and bought one of these blowers from Kayne & Son (aka Blacksmiths Depot.) Much to my delight, not only did they work, but I found that I did not have to change any of my pipe sizes, the 1 1/2" black pipe slips into the blower. The only size change I have seen is initially I had to remove the coating from the black pipe for a slip fit. Now I don't have to do that. Not sure which changed, the pipe or the housing of the blowers? Does not matter, I normally don't even have to worry about taping around the pipe, the fit is good enough. I love it when a plan comes together and it is a simple as what I do. My "horizontal" forges are 2 and 3 burners that I can do lots of forge welding, the verticals I don't use for welding, so it is not as important to be as hot. But they still work very well.

Thank you Grant for the arrangements to get those blowers into our hands. As I occasionally sell my forges to students, I have probably gone through at least 2 dozen of these. As previously mentioned, you can normally find 6 in my shop, 4 permanently mounted, 3 getting serious use. I am still using the first one.

I receive no benefit from promoting these blowers, only hoping enough people continue to buy them so Kaynes keep stocking them for when I need to buy them.

[Robert Simmons]

I would love to get one of grant's blowers and will do so when I have the spare change to do so. As it is I have to improvise with a hair dryer. So I built a blown burner with a flame stabilizer rather than a flare and I have had some fascinating results from the experience. First the construction.

So I attached the hair dryer with a ton of tape to a 2" black iron pipe nipple and then attached that nipple to a bell reducer that reduces from 2" to 1". The bell reducer is attached via a close nipple to a gate valve and then that is attached via another close nipple to a T fitting. At this point I had goofed, I had the wrong size reducer for attaching the propane line but that was a happy accident really. I welded the 3/4 inch to 1/2 inch bell reducer to the top of the T junction and then attached a bushing to convert from 1/2 to 1/8 inch to the bell reducer. This allowed me to attach the 1/8th inch propane supply pipe. Next I attached the burner tube to the other end of the T and welded into that burner tube is the flame stabilizer. You can see the structure in the image below. I got the flame stabilizer design from another web site posted in this thread.

When I turned it on outside the forge, I used about 2 psi of propane and opened the gate valve for the air just a bit to start. The results were dramatic to say the least. The flame burned blue but detached from the burner by about 4 inches, however the whole flame itself was probably three to four feet long with only the first 4 inches or so blue and the rest a flaming, fuel rich yellow. Clearly this is not what I wanted. Adjusting the air from nearly closed to open didnt do a heck of a lot except if I put too much air in, the flame would detach and the torch would go out. I will give the flame one thing though, it put out a hell of a lot more heat than the same venturi burner at that pressure.

Putting it in the forge had similar dramatic results. I was pleased to see my forge design actually started a tornado of hot gas in the forge, however yellow flames leaping out 3 feet in front of the forge might cause a bit of a logistic problem (not to mention fire hazzard). Again, it produced a hell of a lot of heat. I had some problems keeping it on but that was probably only because I was messing around so much with the air volume.

So clearly the flame burned way too rich though my CO detectector registered a constant 0 with my 1000cfm fan overhead on so it wasn't producing so much CO that it overpowerd the fan as some of the venturi designs have done.

I am tring to figure out how to fix it and the only thing I can think is perhaps the fuel and air are not completely mixed when they hit the flame and that is causing the problem. I have thought I might put in a couple of elbows in the burner to increase the turbulence of the air flow and promote mixing. I dont know if that will work though.

Suggestions would be appreciated.

[Nakedanvil - Grant Sarver]

Did you try turning the gas way down?

[Robert Simmons]

Did you try turning the gas way down?

Yeah all the way down to flameout. I dont think the gas is mixing enough in the burner. The elbow idea is simply to try and make it mix more.

I am also wondering if I can use a single propane inlet for two burners in the forge though with the heat I was getting on the torch one might be enough.

[Robert Simmons]

in the continuing saga, the placement of elbows did not increase the mixing and still resulted in the flame detaching from the flame stabilizer. I went to a smaller flame stabilizer circle and welded the supports to the stabilizer on the bottom of the inner cylinder instead of the top of the cylinder and the flame shape looked much nicer. It might be a good idea to add the small solid rod in the middle of the two cylinders but I will play with that later. I also tried drilling a 1/2" hole in the pipe and inserting a 1/" pipe and welding it in. This caused the mixing to be better I think but didn't help at all with the detaching of the flame.

Right now I am thinking the position of the propane jet will be the answer to the question. Right now the jet comes in at right angles to the air flow and I think that might be the cause of many of the problems. I am going to flip the jet to one of the long sides of the T junction and slide it further into the intersection and see if the flow improves.

Man after all this I should make a blog or post or something with all I have learned through experimentation and research.

[kcrucible]

It occurs to me that your flame detachment problem is probably a function of air velocity. The stabilizer is intended to slow down the air/fuel mixture, but it's not doing enough.


Assuming that the air/fuel mix is right, then it's just a matter of slowing things down. You could try increasing from a 1" tube up to a 1.5" or 2" tube at the exit. That should (I think) make the same volume of air exit at a slower speed (basically the inverse of putting your thumb over a garden hose.)

Adding a rheostat to the hair dryer might do the trick too (like a dimmer switch), though that will change the air/fuel ratio, as would diverting a portion away from the air intake.

Just trying to be helpful, even though I'm more novice than anyone here. ;)

[Robert Simmons]

It occurs to me that your flame detachment problem is probably a function of air velocity. The stabilizer is intended to slow down the air/fuel mixture, but it's not doing enough.


Assuming that the air/fuel mix is right, then it's just a matter of slowing things down. You could try increasing from a 1" tube up to a 1.5" or 2" tube at the exit. That should (I think) make the same volume of air exit at a slower speed (basically the inverse of putting your thumb over a garden hose.)

Adding a rheostat to the hair dryer might do the trick too (like a dimmer switch), though that will change the air/fuel ratio, as would diverting a portion away from the air intake.

Just trying to be helpful, even though I'm more novice than anyone here.

Every suggestion helps.

The problem with sizing up is that the forge is cast already so that wont happen. Also empirically it should be possible to do a 1/2" blown burner as much as a 2" one if the fuel mixes properly with the air and the velocity is right. It is clear that the flame can burn, it just detaches. If it detached pure blue, I would say that the velocity is just too high but the mix is right. However, it is detaching when the flame is still yellow and I think that might mean that the mixing isnt working the way I want. That could be a function of the right angle entry of the propane rather than firing the propane right into the moving air stream as direct injection would do. So I will try the direct injection and get back to you.

[kcrucible]

Every suggestion helps.

The problem with sizing up is that the forge is cast already so that wont happen. Also empirically it should be possible to do a 1/2" blown burner as much as a 2" one if the fuel mixes properly with the air and the velocity is right. It is clear that the flame can burn, it just detaches. If it detached pure blue, I would say that the velocity is just too high but the mix is right. However, it is detaching when the flame is still yellow and I think that might mean that the mixing isnt working the way I want. That could be a function of the right angle entry of the propane rather than firing the propane right into the moving air stream as direct injection would do. So I will try the direct injection and get back to you.

Well, there are two issues... one is the richness, one is velocity. They're somewhat interrelated, and somewhat independant.

Your previous post where you said that you turned down the gas until flameout, it could be that the high velocity of air is what caused it to blow out, not neccessarily that it was down to no gas. A slower air velocity may allow the smaller quantity of gas to burn properly. If you did something like hold the hair dryer away from the input port so that different amounts of air escape instead of entering the pipe, you could try tuning that?


If I were trying to diagnose the problem I'd probably start with a very small amount of gas (the least you can manage) and almost no air, then start adding air a bit at a time till you got the ratio correct. Then you could scale up both gas and air at the same time until you had substantial heat and good flame, etc. (then you mark your dial, etc, so that you can just start there every time! )

[ThomasPowers]

I'd say that every blown burner needs controls for both gas and air which will allow it to be tuned for any particular point.

For me the gas control is the regulator on the propane tank and the air control is a sliding plate in the air pipe. To run I turn on the gas at a pressure close to what I've used before and light the burner and then turn on the air and adjust it till I get the burn I want.

If I want to go hotter I increase the gas pressure and then increase the air till I get a tuned burn again. To go lower I decrease the gas pressure and re-adjust the air flow again.

Adding a blower to a system designed to work as a venturi is probably not as effective as building a simple blown burner.

Did you talk with a local HVAC company about getting one of the blowers used for the hyper efficient gas furnaces---not the one to send air to the house but the one used to provide positive venting of the combustion. If you explain what you are doing and don't come across as crazy or abrasive you can often get a used one free or for a nominal price.

[Robert Simmons]

Adding a blower to a system designed to work as a venturi is probably not as effective as building a simple blown burner.

I am not converting a vneturi. Just using some of the same pipes. Not all the same, just some of them.

Did you talk with a local HVAC company about getting one of the blowers used for the hyper efficient gas furnaces---not the one to send air to the house but the one used to provide positive venting of the combustion. If you explain what you are doing and don't come across as crazy or abrasive you can often get a used one free or for a nominal price.

Interesting idea. When I have at least a little cash I might check. However, I think I will just end up buying a real blower sometime.

What i am thinkign aobut now is if one blower can power three burners. Hmm.

[ThomasPowers]

"A real burner" so a burner specially engineered to be used in a gas furnace isn't real? Perhaps this was worded wrong?

When SOFA had their first gas forge building workshop we just used a small 150 CFM squirrelcage from an industrial supply like Graingers. It's worked for over 10 years now. Was a lot more expensive than picking up one used from the HVAC folk; but we had to have a lot of identical ones for the workshop so all the forges would be the exact same. (we set up an assembly line and built forges all day and then numbered them all and pulled numbers from a can to see who got which one---keeps everyone on their toes as you don't know which one will end up yours!)

Sounds like you will be paying about the same or more for your blower than we paid for the entire forge---minus the hose, regulator and tank. Great if you can swing it; but a lot of us are not so well heeled.

[Dodge]

I would love to get one of grant's blowers and will do so when I have the spare change to do so. As it is I have to improvise with a hair dryer. So I built a blown burner with a flame stabilizer rather than a flare and I have had some fascinating results from the experience. First the construction.

So I attached the hair dryer with a ton of tape to a 2" black iron pipe nipple and then attached that nipple to a bell reducer that reduces from 2" to 1". The bell reducer is attached via a close nipple to a gate valve and then that is attached via another close nipple to a T fitting. At this point I had goofed, I had the wrong size reducer for attaching the propane line but that was a happy accident really. I welded the 3/4 inch to 1/2 inch bell reducer to the top of the T junction and then attached a bushing to convert from 1/2 to 1/8 inch to the bell reducer. This allowed me to attach the 1/8th inch propane supply pipe. Next I attached the burner tube to the other end of the T and welded into that burner tube is the flame stabilizer. You can see the structure in the image below. I got the flame stabilizer design from another web site posted in this thread.

When I turned it on outside the forge, I used about 2 psi of propane and opened the gate valve for the air just a bit to start. The results were dramatic to say the least. The flame burned blue but detached from the burner by about 4 inches, however the whole flame itself was probably three to four feet long with only the first 4 inches or so blue and the rest a flaming, fuel rich yellow. Clearly this is not what I wanted. Adjusting the air from nearly closed to open didnt do a heck of a lot except if I put too much air in, the flame would detach and the torch would go out. I will give the flame one thing though, it put out a hell of a lot more heat than the same venturi burner at that pressure.

Putting it in the forge had similar dramatic results. I was pleased to see my forge design actually started a tornado of hot gas in the forge, however yellow flames leaping out 3 feet in front of the forge might cause a bit of a logistic problem (not to mention fire hazzard). Again, it produced a hell of a lot of heat. I had some problems keeping it on but that was probably only because I was messing around so much with the air volume.

So clearly the flame burned way too rich though my CO detectector registered a constant 0 with my 1000cfm fan overhead on so it wasn't producing so much CO that it overpowerd the fan as some of the venturi designs have done.

I am tring to figure out how to fix it and the only thing I can think is perhaps the fuel and air are not completely mixed when they hit the flame and that is causing the problem. I have thought I might put in a couple of elbows in the burner to increase the turbulence of the air flow and promote mixing. I dont know if that will work though.

Suggestions would be appreciated.

I made my flame holder much like yours except there is a final solid slug in the center. I started with 1.25" straight black pipe(no elbows. Only a Tee to connect the blower) and used 1"(?) then a solid piece of 1/2" round in the middle. Maybe your open center isn't stable enough. It worked just as well outside the forge as in. I can run it as high as the regulator will allow as well as down to 2 or 3 pounds pressure. The only thing I have to do is adjust the air flow. Less gas; less air flow. Hope this helps :)

[SGensh]

Robert, I know it's easy to get frustratred with a project when it's not quite working out right but there will be a solution (or several) to your burner problems. I'd suggest that you may want to take a look at a very useful series of one or two page articles on burners which appeared in Process Heating and which you can view on the web. They will help you get a clear view of several types of burners as they have been used in industrial applications and perhaps that backround knowledge will help you to toubleshoot your own burners. There are simplified but clear diagrams and explanations of how and why certain types were developed. It's well worth the few minutes you'll spend running through them. You can find them by doing a Google search for "process heating buner history 101".

Thomas' suggestion of the free or almost free heater vent fan is a good one if you don't want to spend for one of Grant's. While they don't look impressive these units have high static pressure which is what you need in forge blower. I''ve passed along a few of these to other smiths and they have had good success with them. Jymm Hoffman's gas forges use more than one outlet with a single blower so you should be able to run your three tubes from a single one also. Take a look at Jymm's system which works very well, it's not a bad model to follow for a blown forge burner.

I've built both blown and atmospheric burners and each has it's place. There is no reason that you couldn't heat your funace with atmosperic's also but whichever type you've decided it's worth a quick look at the articles above.
(As an atmospheric application example a single PNB atmospheric burner in my freon can forges will burn from about 1 pound indicated on my Goss regulator guages up to over 40, average forging pressure is about 5 to 7 and it welds at 10 with no flare used in the forge. In the two burner it works similarly once up to temp but starts a little more tempermentally. It gets very hot- this is the forge Steve Parker and Phil Cox used at the Abana Conference)

[Robert Simmons]

Ok now I have experimented with injecting the gas directly into the stream and the flame still blows off the end of the burner. Clearly nothing I do is working here and it is frustrating me to no end. On top of that the hair dryer I was using as a blower died for unknown reasons and now I don't even have something to move air. This is so frustrating because I didn't join this board or hobby to design a perfect propane jet. My goal was to actually hit metal but I dont have anything that will heat my forge. The venturi designs stop due to back pressure in the forge (and any tiny modification of the forge doors cause problems, and the blown burners i have tried will, none of them, stay lit. And this is despite using almost an identical design to the one on knifehelp site. The only difference is my blown burner is only 1 inch in diameter whereas theirs is 2 inches. However there is no way I would be able to size up to 2 inches without pouring a whole new shell.

Right now I am putting propane in with a 1/8th tube. From the bottles, it goes through 1/4 inch hose then flashback arrestor (which is NOT going to come off) and then through a reducer to 1/8th and then injected into the air stream. The only remaining idea that I have is to use a 1/4 inch tube to inject the propane hoping that will slow down the gas enough so that it doesn't try to pop off the end of the torch. But I cant do that tonight as I am without an air source so another day without hitting metal. I don't know if that will work but its the only thing left that I can think of to try.

Going to propane seemed like such a good idea and now down a couple hundred bucks and 2 weeks I am regretting it.

[kcrucible]

The only difference is my blown burner is only 1 inch in diameter whereas theirs is 2 inches. However there is no way I would be able to size up to 2 inches without pouring a whole new shell.

That gets back to volume of air/fuel vs pipe diameter... ie velocity. Increasing the pipe diameter is one way to decrease velocity, but you could just put less air into the tube. You could use a Y (use the inline portion to inject) to split the air stream in half and only send half of the air into your burner, for example. If you add a valve to the output of the Y that feeds into your burner, then you can directly control how much air goes in. If you dial down the aperature then the rest of the air escapes through the other port. This gets around my earlier thinking that trying to reduce capacity would just increase velocity because there's a pressure release. It's easier for the excess to go out the other way than build to a higher pressure.

The only remaining idea that I have is to use a 1/4 inch tube to inject the propane hoping that will slow down the gas enough so that it doesn't try to pop off the end of the torch.

That sounds like a good idea to me. The longer the tube is the better I'd think... more time to slow down.

On top of that the hair dryer I was using as a blower died for unknown reasons and now I don't even have something to move air.

My guess is that the hair dryer couldn't handle the back-pressure being generated by putting that much air through that small a pipe. Putting in the pressure relief port I mentioned above should help keep the pressure nearish-atmospheric.

[Robert Simmons]

Well I swapped out for the 1/4 inch brass tube to put the propane in the burner and it still wont work in the forge without being very touchy and spiking the carbon monoxide. Out of the forge I cant get a stable flame if I have any air on at all. If I only turn on the propane, the torch produces a four foot long yellow flame that is obviously not good.

I have tried various flares and stabilizers, I have tried putting in elbows to encourage turbulent mixing, I have even tried a very long propane feed to have the two mix just at the end of the torch. Nothing is working for me. Every flame tries to detach if I use any air at all.

I am intensely frustrated and frankly ready to throw in the towel. If I didnt have a nice cast forge already and 300 into this project with all the tinkering, I would have scraped this idea already. Nothing I do accomplishes the task and the venturi burners work great out of the forge and not at all in the forge.

I am pretty close to saying "hell with it". I wanted to save money but I havent. And I cant justify spending hundreds now.

[Nakedanvil - Grant Sarver]

If you can run it at all, close it up as tight as you can and let it run for awhile and get hot and see how it works.

[Robert Simmons]

If you can run it at all, close it up as tight as you can and let it run for awhile and get hot and see how it works.

I can run it for a bit but very rich with lots of CO production.

I am beginning to wonder i the altitude at 5280 feet here in denver is an issue. I dont know at this point. Maybe the gas I am using is bad and I should try another bottle.

[pkrankow]

Altitude can affect it for sure. The thinner air and all.

Can you move the apparatus outside to fire, that way CO is a non-issue? Your forge won't settle down till it is running for 30+ minutes this first time, and it will take time to settle down every time it is lit.

Even my tiny kaowool lined forge takes about 5 minutes to start acting proper, but I work outside so never tried to measure CO. Yes, my burners despise wind, and my forge has been blown out by the wind too. There are days it huffs and puffs but stays happy enough for me to have some fun.

Phil