Forced air burner tuning?

N

Nylund knives

Well-Known Member
Hi again,

I have now made a forge to do my forge welding but I have som trouble with the fine tuning of my burners. I have made a lot of changes cutting and welding to my forge thats why it is so ugly.

This is my current setup:
8-2.jpg


The inside is about 17 inch long with 3 layers 1" wool, inside dia is 6" and I have two burners, the hole for the gas inlet is 1/16.

I've also tried a single burner and only 2 layers of wool.

What should the flame look like inside the forge?

What I'm trying to get is some blue at the burners, about 2inches long blue flames, and some yellow flames out of the burner opening, "dragon breath" like in the picture. Is this right?

My main problem is probably that my blower is to large.

When I'm running at 7 psi and the bladevalve for the blower is 95% closed then everything is looking good, and I get welding heat but my burners have backfired a few times and starts burning inside the pipe. The nozzle on the burners look like this:
flameholder.jpg


The bigger pipe is 1,5 inch dia. Can the door be to small?
If I open the gatevalve to about 80% I get long blue flames and no dragon breath. If I then turn up the gas to about 10 psi everything is looking good except that the wool starts melting inside my forge.

I run the forge for 20min today and in that time I hade melted away 1 inch of the 3 inches of wool.

Do you have any ideas?

Regards
Jakob
 
I see several things that are causing various problems you mentioned.

1. I suspect the blower is WAY too much CFM for that forge.

2. Part of the reason your getting back-burnering into the burner is their location and orientation. Heat is going to travel up, and with those burners mounted as they are, they will just keep getting hotter and hotter until the air/fuel mixture ignites inside the burner tubes.
Also, with the burners orientated that way, you're directing the flame right on your work piece/billets.....not good. The whole idea of use a circular forge design is to create a swirling flame pattern.
(the forge shown in these pics is 8" ID with 1" of kawool X 16" long, running a single venturi burner that is 1" diameter. At 10psi, it will run 2000F all day long. NOTE: this is my general purpose forge, and is not for welding....I have a separate vertical welding forge.
Flamepattern1.jpg

Flamepattern2.jpg

You do this by mounting the burners on a tangent to the radius of the forge's interior, This not only produces a more even heat, but if you mount the burners through one side or the other, they also heat up less, and your fuel line isn't hanging directly over the heat of the forge.
Here is a pic of my venturi forge to give you an idea of the burner orientation:
ForgeBurnerTangent.jpg



3. The way the angles are in the tubing/burner....those are basically square corners....really reduces the "smoothness" of the air/fuel flow, and causes major restriction.

4. Personally I think your "over burnered"...meaning that for the dimensions you indicated, you've got too much/many burners. A single 1 1/2" burner at 6-7psi with a 150 +/- cfm of air should run that forge easily at 2350F+

Overall, I think you have a few components that are not sized correctly for the size forge you indicated.... and those are what's causing many of the issues. Down size the blower to about 150-175 cfm, go to a single burner setup like in the photo above, and up size the burner to 1 1/2". I think those modifications will go a long ways towards solving your issues.
 
Question.. I know you asked a different question but im trying to understand and mybe help you and others......you say you used 3 layers of 1" kola wool...how did you secure it and did you cover it toataly with a refracatory cement of some kind? and if so what ?...theres a reason i ask this..

thank you
 
I have a heat treating/welding forge with about the same interior dimensions as your forge that is also lined with 3" of ceramic insulating matting, mainly to take up the space inside the large mailbox that I used as a shell for the forge. I have a single 1" burner tube powering it and I can max out the display on my pyrometer at 2000 degrees or cut the gas back and run it at about 1650 after a full warm up. The blower that I have feeds 60cfpm but that seems to be pretty minimal. If I replace the blower it will be more powerful, more like Ed mentioned.

You really should take Ed's suggestion and change the angle that the burners enter the forge. My burner enters the the fire chamber just below the top and is mounted horizontally to the body of the forge. It gives a fantastic swirle of burning gasses which is really evident if I have to cool an overheated part of the blade in oil then return it to the forge.

I would also like to make the suggestion that you find something else to rest the bar of steel on while heating it in the forge other than the anvil. If you get a little absent minded and walk around the anvil while forging a piece of steel you will be putting your back side right into the dragon's breath. Believe me, you notice real fast...but don't ask how I know. Also if I was working that close in front of the forge in some of the weather we've had here in Illinois the last I'd fall out from the heat.

Doug
 
Thanks once again for helping me Ed.

The reson I put the burners like this, this time was to protect the wool from melting. At first I had a single burner, only 2 layers of wool and the burner was at a tangent, the wool melted after about 10 minutes, it's 2300 fahrenheit wool.


I will try again with both the single burner and the two burners to see if I can get any better results. I will also be looking for a smaller blower.




Jakob
 
Black Dragon Forge said:
Question.. I know you asked a different question but im trying to understand and mybe help you and others......you say you used 3 layers of 1" kola wool...how did you secure it and did you cover it toataly with a refracatory cement of some kind? and if so what ?...theres a reason i ask this..

thank you
Click to expand...

Hi,

At first I covered the wool with a fireclay but it didin't work that good. It shrinked very much when drying so it cracked a lot, after a few coats it did look okay but almost everything fell off in the first heating of the forge. At the moment I have noting to cover the wool.

I will, as soon as I've found a scandinavian supplier, cast the interior of the forge with some kind of refractory. Shipping from the states was very pricey.


Regards
Jakob
 
Doug Lester said:
I have a heat treating/welding forge with about the same interior dimensions as your forge that is also lined with 3" of ceramic insulating matting, mainly to take up the space inside the large mailbox that I used as a shell for the forge. I have a single 1" burner tube powering it and I can max out the display on my pyrometer at 2000 degrees or cut the gas back and run it at about 1650 after a full warm up. The blower that I have feeds 60cfpm but that seems to be pretty minimal. If I replace the blower it will be more powerful, more like Ed mentioned.

You really should take Ed's suggestion and change the angle that the burners enter the forge. My burner enters the the fire chamber just below the top and is mounted horizontally to the body of the forge. It gives a fantastic swirle of burning gasses which is really evident if I have to cool an overheated part of the blade in oil then return it to the forge.

I would also like to make the suggestion that you find something else to rest the bar of steel on while heating it in the forge other than the anvil. If you get a little absent minded and walk around the anvil while forging a piece of steel you will be putting your back side right into the dragon's breath. Believe me, you notice real fast...but don't ask how I know. Also if I was working that close in front of the forge in some of the weather we've had here in Illinois the last I'd fall out from the heat.

Doug
Click to expand...

Yes, the forge and anvil setup is just temporary. I need to pour a new floor and a foundation for my hammer so in the mean while I'm trying to get my forge running as it should.

I think I really need to find a new blower, the blower I'm using now is almost as heavy as the anvil on the picture and is three phase...
 
What is the ceramic fiber matting rated at? It should be be 2400 degrees (1300 degrees C.), though you could get something like Inswool HTZ which is rated at 2700 degrees (1500 degrees C). You can find it at Hight Temperature Tools and Refractory Supply. Granted, the oversees shipping costs, if he ships overseas, will be a real hit in the pocket book. Of course, look locally first. Do not run a forge with a ceramic matting lining that is not covered with something, mine is coated with about 1/4-1/2" of a refractory cement. Once the matting has been heated to over 600 degrees (aprox. 300 degrees C.) it can form particles that will bury themselves in your lungs and not come out. That means that if you have to replace the lining you need to wear long sleaves and a respirator, not dust masks which only make you think that you're protected against particles.

Doug
 
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