Nanafalke Posted October 25, 2017 Share Posted October 25, 2017 Hey, I just finished building my forge burner, it is based of Will Matthews Design and uses a 1/8" pipe and a 0.6 mig nozzle with a couple other fittings. Here are some pictures: Sadly, at 0.2 bar (2,90075psi) it is not burning well, makes a weird sound too. If I increase the pressure, it starts burning correctly. Video of it burning, first at 0.2 bar, then I increase the pressure and decrease it in the end: My theory is that it may be drawing too much air, but even if I cover the back of the bell reducer, the flame doesn't get better. Thanks alot! Best wishes Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 25, 2017 Share Posted October 25, 2017 From what I saw the burner behavior is normal at low pressure. The flame was burning inside the tube and that creates the pulsing/chirping sound. Once you turned the pressure up the flame was burning at the end of the tube as it is supposed to do. At low gas pressure there isn't enough velocity to pull in the appropriate amount of air. The problem is not enough air, not too much. It's not really a problem though since (in my experience at least) you'll be running higher pressure than that when forging anyway - unless you have way too much burner for your forge. Also, keep in mind that the burner will behave a little differently inside the forge due to additional back pressure. Quote Link to comment Share on other sites More sharing options...
Binesman Posted October 25, 2017 Share Posted October 25, 2017 Im sure frosty and mike will be along soon to help and they have both forgotten multiples of what ive ever known about a burner. However air intake isnt your issue You are getting early combustion and the flame is firing inside your mixing tube. When you turn up the pressure you can see the flame jump to the tip of the reducer and it starts burning correctly. I believe a proper flare to create a better venturi should correct that however not 100% id wait for someone with more experience to verify that. In the meantime i might recomend grinding the threads off the business end of your coupler to try and reduce turbulance at lower pressure to get the flame to stay at the end Quote Link to comment Share on other sites More sharing options...
Nanafalke Posted October 25, 2017 Author Share Posted October 25, 2017 Thanks alot for your help. I actually ran this burner at 0.2 bars before and it worked just fine, sadly I had to replace the 1/8" pipe with a new one, because the thread I cut in the pipe was bad and it didn't properly seal after a while anymore, even with ptfe. That the same burner doesn't work at 0.2 bars anymore confuses me. Video of the "old" burner: Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 25, 2017 Share Posted October 25, 2017 It doesn't take much to change the behavior. If you are just a hair off in jet alignment it can have an impact. MIG tips can have minor differences in orifice diameter. The point is that very small changes can have a noticeable effect. The smaller the diameter of the burner the more minor changes can have a significant impact in performance. Quote Link to comment Share on other sites More sharing options...
Nanafalke Posted October 25, 2017 Author Share Posted October 25, 2017 Didn't know that just a little change could have an impact on the combustion. Thanks for the information. I have 9 more mig tips, will try them out tomorrow. If that doesn't help, I probably have to realign the pipe. Quote Link to comment Share on other sites More sharing options...
timgunn1962 Posted October 25, 2017 Share Posted October 25, 2017 Have you tried it in a forge yet? If it is going to work in open air, then trying to tune it in open air makes perfect sense. However, if it is going to be used in a forge, tuning it in a forge is the sensible course of action. The forge massively changes the conditions at the tip. With a forge full of flame, there is flame drawn to the edge of the burner nozzle and this keeps the main flame attached. Which thread was bad and leaking in the first one? If it was leaking gas that got drawn in to the burner, the extra (leaked) gas will have changed the mixture ratio. Might this explain why things were different once you stopped the leak? Quote Link to comment Share on other sites More sharing options...
Nanafalke Posted October 30, 2017 Author Share Posted October 30, 2017 Not yet, I still have to build it . The thread for the mig tip was leaking, that probably let more gas run into the pipe. So that probably lead to more gas in the combustion. Strangely, now I have to really crank the pressure up for a proper flame. Seems like something is jammed. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted October 30, 2017 Share Posted October 30, 2017 No; cranking up the gas pressure will never induce enough air to balance out an over rich flame, because air induction and incoming gas pressure are functions of each other. Yes, raising the gas pressure will improve the air induction, but never enough to overcome a gas jet that is simply too large for the burner it is in. Quote Link to comment Share on other sites More sharing options...
Jasent Posted October 31, 2017 Share Posted October 31, 2017 (edited) Every mig tip is going to be slightly different. I have 2 T burners that are identical in parts and build but both work very differently! Funny part is the one that's the most imperfect works the best in my forge. The other is as close to concentric as I can measure ( 0.0015") but dosent work as well as the crooked one. Changing tips in the crooked one made it burn very poorly. That same tip that messed up that one made the centered burner improve. All where the same size and from the same package. Remember these tips were made to feed wire to a welder. Not as gas nozzles. Just my experiences and thoughts the leak theory sounds plausible. Either run the higher preasure or try all the tips you have Edited October 31, 2017 by Jasent Quote Link to comment Share on other sites More sharing options...
JoeThePro Posted October 31, 2017 Share Posted October 31, 2017 23 hours ago, Nanafalke said: Seems like something is jammed I've had needle valves and regulators act like that before. Also be sure you aren't triggering the safety in the tank by cracking open the pressure too fast on start up. Quote Link to comment Share on other sites More sharing options...
Nanafalke Posted November 5, 2017 Author Share Posted November 5, 2017 I disassembled everything and cleaned up all pipes and holes. Now at 0.2 bars it works just fine. So there was something jamming. I also removed the valve because it broke while fastening the pipes. Interestingly, now it draws too much air, resulting in blowing the flame out. The airintake needs to be covered quite a lot for a stable burn. But calibrating the burner outside the forge would make no sense. Thanks for your help so far . Im going to build the forge out of a 11 kg (24lbs) propane tank with 2 layers 1" ceramic wool isolation and aprox 0.8" firecement. What do you guys use for regulating the pressure? At the moment, I have a pressure gauge from 0 to 1 bar (15 psi) installed at the burner and I regulate the pressure with a 2.5 bars (36 psi) pressure reducer simply by turning the valve of the tank. Are there better regulators where you don't have to mess with the valve of the propane tank and control it more easily? Best wishes Quote Link to comment Share on other sites More sharing options...
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