Hello everyone, Im making my first propane torch foundry and I'm stuck on one part. The whole that the torch goes in, I've read the whole needs to be 3 times the size of the torch, I've also read that it should be double the size. So if I have an inch in diameter, from what I understand that would be a 3 inch hole? Any help would be appreciated
what type of burner are you making??? cant answer without knowing that A venturi I assume which most people use a .035 Inch V/r HT1
That hole is called the tuyere and for propane furnaces it is usually a minimum of 3 inches in diameter. You can make it as large as 4 but I wouldn't go over that or you're going to have a large hole in the side of your furnace that may cool it too much or overheat due to the relative lack of insulation.
Thank you very much. I was thinking 2.5 inch hole. Like you said im just affaid to make too big of a hole
That just doesn't sound right ??? Mine on a 3/4" inch burner is only about 1.25" sort of like having a flare right before it enters the furnace. I guess it does act as one...
Having the Tuyere 3x the burner tube is nonsense. Answers will vary on that but can also depend on furnace size and burner style. For most furnaces with a propane burner 2.5" is plenty because you'd never have burner that needs a larger Tuyere for that combo. If you get the Tuyere too large, you get flame leakage which can be remedied by stuffing the gap with ceramic wool but when you get the center of the burner and flame path farther inward and crowds the plinth or impinges on your crucible (unless you mount the burner off center)......like the example of a 4" Tuyere in a 10" bore furnace, where the Tuyere is nearly half the furnace bore.. A 2" ID burner tube can support a high energy propane burner, but some styles oil burners can have a lot of hardware inside the burner tube and utilize the space. What are the internal dimensions of your furnace? Best, Kelly
My Tuyere is literally the exact size of my burner, I cast the burner wrapped a couple of times with paper directly in to the wall of the furnace
? 3 inch works fine. Let's you shove more air in to burn more gas and let's you swap out the burner for an oil burner down the line. If you angle the inside of the furnace wall so the flames spiral around and the wall shields the burner tube then you get no flame leakage. Like this (obviously with the burner tube pulled back into the wall).
My tuyere is 2" and works well. If I do this again it will be 3". Easier to neck it down than make it bigger. You only chip out refractory once to realize it's a miserable job. Some tough stuff!
I'd did it similarly except I used a slightly undersized roller I had laying around and wrapped a few turns of aluminum flashing around it. After finishing the refractory installation I simply slid the roller out and collapsed the flashing to remove it. I welded a split piece of the actual burner tube pipe material, 2-1/4" exhaust pipe I believe, to the outer shell for burner support. I only welded it from 12 o'clock to 6 o'clock and left the left side sprung open. I use a quick release hose clamp to cinch it up when I install the burner. That keeps the weight and abrasion from the burner tube off of the refractory.