Fe-Wood Posted June 8, 2009 Share Posted June 8, 2009 Just thought I would share this- The other day I took the burner out of my gasser to use as a heat source to anneal a large piece of copper. The burner is a 3/4" Mike Porter design with a .035 orifice. Thinking the burner wasn't getting the copper evenly hot enough, I decided to increase the orifice size to .045. More BTU right? I was able to tune it to a nice neutral flame running at 6 PSI. Well, it worked just fine as a torch but not when I put the burner back in the forge with the larger jet. Then it started randomly spitting unmixed fuel (still vapor). There was also a considerable amount of "blue/green flame" coming out the forge opening. I suppose this was caused by the back pressure of the forge itself being a limited or confined space and the mixing tube not being big enough to effectively mix the added volume of fuel. I tried tuning the air intake to no avail. I have since replaced the .035 orifice and re-tuned the burner and it works fine again for the forge. Findings- I guess the rules for forge burners don't apply when using them as a hand held torch. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted June 8, 2009 Share Posted June 8, 2009 My experience is that, yes, the rules Mike Porter sets out are very well thought out and apply extremly well to the specific circumstances he designed for. Basically what works in a forge will work in open air. But the reverse is not true. What works in open air will often not work in a forge. The back pressure in a forge lowers the effectiveness of mixing. I use a somewhat different set up than Michael Porter but have not found any exception to his general statements about what it takes to mix gases or the effects of back pressure. Those are based on simple physics. Quote Link to comment Share on other sites More sharing options...
Frosty Posted June 9, 2009 Share Posted June 9, 2009 All these things work the same way, whether they're commercially, or home made. an induction device is an induction device, same principles, same rules. Mike did an excellent job of expressing the way these things work. There's one more factor to being able to use a much larger jet in a burner intended for open air use and that is secondary induction after the air fuel mix leaves the burner nozzle. It'll draw quite a bit more air right out of the nozzle which isn't available inside an enclosure. Frosty Quote Link to comment Share on other sites More sharing options...
Fe-Wood Posted June 12, 2009 Author Share Posted June 12, 2009 If I understand you correctly Frosty, is that just the ambient air around the flame or are you speeking of another air intake just before or within the flame holder? I just finished a 1" burner. Its hand held and I'm using to anneal large copper pieces. I patturned it after the "hybrid Burner" Not as clean as his but boy is it hot:D I've started 4 of the 1" and I'm thinking that 2 will be used for a small foundry furnace as I'm itching to cast some bronze:) I'm going to use a 40# propane bottle for the furnace body and hopefully a number 10 crucible if side clearance will allow. Quote Link to comment Share on other sites More sharing options...
Frosty Posted June 12, 2009 Share Posted June 12, 2009 Yes, secondary induction is of ambient air from around the burner nozzle. The resulting flame is the secondary combustion zone. (I think that's what it's called) Regardless it's not difficult to design and tune a burner to work efficiently outside an enclosure. As you've discovered. Frosty Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.