Help with tuning blown forge

[ciladog]

Well it sure burns great, and appears to support what you say about "more" air and not "less"

Do you have any other images/details of the "side blast ceramic ribben burner"

I dont have a needle valve on my gas, which also makes it hard to tune.

Credit where credit is due. I just followed what these guys did with some of my own modifications.

link

link

I made mine by drilling a hard firebrick, not casting one. I cut a rabbit about 1/2 inch by 1/4 inch around the outside of the brick with a diamond blade on an angle grinder and cemented it into the mixing box.

You can adjust it down to a wisper or up to a blast furnace but if you don't blow in enough air for the amount of gas, the flame jumps into the mixing box. When that happens, I just shut the gass ball valve then open it again with a little more air and all is well.

[Dave Hammer]

Ciladog....

What did you use for cement?

[kcrucible]

You can adjust it down to a wisper or up to a blast furnace but if you don't blow in enough air for the amount of gas, the flame jumps into the mixing box. When that happens, I just shut the gass ball valve then open it again with a little more air and all is well.

Basically it's a multi-jet buner drilled out of fire brick. Given the lack of straight flow from the air/fuel input to the burner inlets, I can see why that design NEEDS a blower. Without signifigant pressure it just wouldn't work. Pretty cool though. This is basically what Grant was doing with his stainless steel rosebud bottom port.

Maybe I'll have to do something like this to create a blown glass glory hole. :)

[ciladog]

Ciladog....

What did you use for cement?

I removed a brick from the forge and took a picture so you could see how the burner is supported. The mixing box is welded to the lower frame of the forge and the burner is supported by and held in place by the top and bottom bricks. So the cement is only to seal off any gas leaking around the sides.

I just used Rutland fireplace patch that I bought at a local store. It’s good up to 2200F and then turns to glass. So what if it turns to glass it still works.

[Dave Hammer]

Celadog...

This is getting more interesting....

Burner holes: How many holes and what size drill bit did you use...

Thanks....

[ciladog]

Celadog...

This is getting more interesting....

Burner holes: How many holes and what size drill bit did you use...

Thanks....

I drilled 15 holes (3 rows of 5)in a 6 inch long brick. The holes are 5/16 inch.

[knots]

Well it sure burns great, and appears to support what you say about "more" air and not "less"

Do you have any other images/details of the "side blast ceramic ribben burner"

I dont have a needle valve on my gas, which also makes it hard to tune.

I have ball valves on my forge furnaces. They are either on or off. The way to control gas volume is with your regulator.

For a given orifice size increasing the pressure increases the flow, and decreasing the pressure reduces the flow. Using an adjustable regulator with a blown forge furnace and controlling the air volume you should be able to tune the burn to a fine degree.

Now with atmospheric burners I still use the regulator but the fuel gas orifice must be carefully sized to the forge furnace volume, and to induce air flow through the burner. I used a smaller orifice and higher pressures for my atmospheric burner to increase gas discharge velocity.

[Charl. Crossforge]

I might be a bit late here, but I have a 2 burner forced air forge done with verokast 1600. It works well. I used mig tips as jets but drilled them out to 3mm. If your jets are too small they act like regulators themselves and no matter how much you open up your regulator, you can only force so much gas through those small jets. If you go too big on the jets you pick up another problem in that you get no back pressure from them, causing your pressure gauges not to show any pressure, thus making adjustments in pressure difficult as you can not really judge the pressure from your gauge.

 

That said, I have found that most times, guys using forced air have too much air blowing into the forge. I use a blower from a car's aircon system which does not give a lot of pressure, and still I have my "gate valves" open only about a 5th of the way. (Flexible pool hose connected to the blower and the feeder pipe for the air with the gate valves is about the same size.) The more air you have, the deeper in the burners your gas will burn, but keep in mind that the air you blow into the forge also cools it down, thus, with too much air you will have roaring burners but in the process you are cooling the forge with too much air preventing it from reaching proper temp. You want most of your flame outside the front of the burner where you want the heat, with only a little flame exiting the mouth of the forge. From here, if you need more heat, increase gas pressure and then increase air flow slowly to reduce the ammount of flame at the mouth of the forge. Repeat till you get the right temp. Also keep in mind that verokast will initially have trapped water and also contains particles that need to burn off initially so you will need to run it a couple of hours to burn in properly. After that it will start to function a lot better.

 

You will also find that as the temperature in the forge starts to increase you will need to adjust gas and air settings. When mine gets up to operating temp I drop my gas pressure by about a third and reduce the airflow to get a little bit of flame at the mouth and that is enough to keep it at the right temp.

 

The trick is really to get the ratio between jet size, gas pressure and airsupply figured out and your forge should work like a charm.

 

Hope that helps.