Ribbon burner forge doesn't come up to temperature

[Lasse Ballweg]

Hey guys, 

I've finally built my new forge and had it drying for a couple weeks before I first tried it out and had it slowly coming up to temperature. But after 20 Minutes it still wasn't nearly hot enough and it didn't seem to go any higher  maybe the forge is just too big for the burner? 

The burner is made from 1 1/2" pipes, gas nozzle is 1mm and the burner block has 23 eight millimeter holes. The Forge is insulated with 3 layers of koa wool and 20mm castable refractory. The blower has 600m3/h and is speed controlled, when I turn it a bit higher than on the picture it blows itself out. 

Thanks in advance to anyone!

[D.Rotblatt]

First thing I see is no door.  Maybe just open for the picture?  If not, a couple of IFB (insulating fire bricks - the light soft kind, not the hard heavy ones).  Huge amount of heat loss with open doors and ribbon burners, I even find that closing off the top half of the opening is very helpful (heat rises).

What is the cubic inch (or metric) size of the interior of your forge?  I assume from what you wrote and past posts you are using a blown system, not NA.  If so you should be able to crank it up.  A gas jet of 1mm (.039") is very small for a blown system, try drilling it out to 2mm or more and use a needle valve - if you are using propane it should still work at that size, you'll just have to crank the pressure up higher.  Further, the 23 hole size is designed for a NA burner, and the original one by Wayne Coe is a 26 or 27 hole so it should work fine if you're forge isn't too big.  Should do a 350 cubic inch (around 6000 cubic cm?) forge easily - and more if you can crank it up.  The small jet might be limiting the amount you can turn up depending on your gas pressure.  But it doesn't look excessively rich in the pic.  If you're using propane, you should be able to crank that up to 20 lbs easy.  If you're running on a gas line, I don't know the pressures there in Germany.

20mm refractory is about 3/4" - which is fine but may take 30 minutes or so to get up to heat depending on the type of refractory. I am a believer of very thin layer of refractory or eggshell layer, but that is not so common and needs more upkeep or care.  First time may take a little longer as the last of that water is dried out.  As I say, I don't use thick refractory layers, but others may chime in.

You are going to get cold spots in your upper and lower left edges next to the burner.  Is there any way to tilt the burner up or down about 20 degrees? Up and the ceiling will heat up and reflect onto the floor, and the flame will form a bit of vortex around the forge.  Down and it will directly heat the floor and what you are forging.  All the combustion with a ribbon burner takes place in the first few inches - in your pic you can see it's fully combusted about 1/3 of the way across the forge.  One advantage of a ribbon burner.  The burner right now is blowing exactly at the opposite wall, which then reflects back - another thing which might be adding to it burning out.

Anyway, hope that helps.  Try one thing at a time, and see if it helps or hurts.  1st start with a door (blocking the opening 3/4 closed). 2nd if the interior size is too big put some IFB in the right side and make it smaller and see if that helps.  3rd try playing with the jet size and see if that helps.  

Good luck,

DanR

[Lasse Ballweg]

Thanks a lot for your tips! Today I tried blocking the openings and making the forge interior smaller by stacking fire bricks I already had (hard type of fire brick)on the side the burner is facing. I think the forge is just too big for the burner and I'll get myself some soft fire brick to reduce the forge size. After about 15 -20 Minutes the forge was quite warm and I was able to turn the gas pressure down. The flame turned to quite a stable state then. I think it will run fine with the soft fire bricks in place and some proper doors. Is it normal that the flames almost disappear at that temperature? The forge was always running on the picture and you can barely see the flames. Thanks for all your help