dhughes Posted October 7, 2019 Share Posted October 7, 2019 Hello forgers, I built a forge this summer according to a large amalgam of advice of this forum. And following that, I was able to get a pretty good forge out of it, so to that extent, I am deeply appreciative for all who extended this advice. However despite best efforts, I can't get a forge temperature that heats my steel above orange heat. Here are some of the variables that seem to affect heat: elevation is about 175 meters mig tips are 0.025" insulation is 2x 1" ceramic wool lining is ~3/8" Mizzou to protect wool Mizzou has 3 coats of ITC 100 internal volume is approximately 176 in³ entrances covered or partially covered with brick when heating pressure is typically 2psi for normal work, tried up to 20psi but still don't get yellow heat Thanks in advance for any help or suggestions. Daven Quote Link to comment Share on other sites More sharing options...
pnut Posted October 7, 2019 Share Posted October 7, 2019 (edited) Outside it's hard to judge color. Orange in the sun is probably closer to yellow. Have you looked at the stock at orange heat in a dark spot like inside a pipe? I thought I was having the same problem until I noticed I burned some mild steel that didn't look hot enough. With that being said, what color does the inside of the forge reach? Pnut Edited October 7, 2019 by pnut Quote Link to comment Share on other sites More sharing options...
dhughes Posted October 7, 2019 Author Share Posted October 7, 2019 10 minutes ago, pnut said: Outside it's hard to judge color. Orange in the sun is probably closer to yellow. Have you looked at the stock at orange heat in a dark spot like inside a pipe? I thought I was having the same problem until I noticed I burned some mild steel that didn't look hot enough. Pnut Ah yes, this is true, I can hardly see any colour when it's direct sun. But I've seen the colour at night, it's certainly orange. The metal is nothing like the colour or malleability I see in forging videos. And seems to lose all colour in 5-10 seconds, where in videos I see orange colour fade out in more like 40, starting from a bright yellow. This makes even normal forge work a bit frustrating, to say nothing of welding! I shall take pics in dim light when conditions allow. 10 minutes ago, pnut said: With that being said, what color does the inside of the forge reach? It gets glowing orange after a while, perhaps 20 minutes. Quote Link to comment Share on other sites More sharing options...
slanwar Posted October 7, 2019 Share Posted October 7, 2019 That was the reason I built a coal forge because even if I use charcoal I'm able to get the metal yellow. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 7, 2019 Share Posted October 7, 2019 What size is the diameter of your burner tube? A .025 mig tip is usually a bit small for a 3/4" burner and I noticed you have some kind of choke system on your intake. A properly built and tuned T burner shouldn't need a choke system. It also looks like the burner tube may be a bit long. For that volume of forge you should be able to get to forge welding heat with a single well tuned 1/2 inch Frosty T burner with the forge openings mostly closed off. Based on the information you've given the burner is almost certainly at the heart of the issue. Quote Link to comment Share on other sites More sharing options...
dhughes Posted October 7, 2019 Author Share Posted October 7, 2019 1 minute ago, Buzzkill said: What size is the diameter of your burner tube? A .025 mig tip is usually a bit small for a 3/4" burner and I noticed you have some kind of choke system on your intake. A properly built and tuned T burner shouldn't need a choke system. It also looks like the burner tube may be a bit long. For that volume of forge you should be able to get to forge welding heat with a single well tuned 1/2 Frosty T burner with the forge openings mostly closed off. Based on the information you've given the burner is almost certainly at the heart of the issue. It's 3/4", and thanks, I'll experiment with larger tips. The tube is 8" long. I did start with a 6" tube, but invariably the heat from the forge would conduct up to the burner nozzle and it would ignite in the Tee chamber, sputtering unless the regulator was turned way up. The longer tube I have found solves this unless the forge has been running for a long time (hours) and then I can wet the burner intermittently to cool it off. The air regulator mechanism is something I wanted just in case it fixed the problem. Typically I keep it all the way open now, as fiddling with it doesn't improve much. I could stick a 1/2" tube on there give it a shot too, if you think that's more appropriate. Thankfully that hardware is just a few dollars! 2 minutes ago, slanwar said: That was the reason I built a coal forge because even if I use charcoal I'm able to get the metal yellow. Heh, I'm beginning to appreciate the thought of a coal forge more and more. But I feel there's hope for this gas forge, since lots of folks seem to have more success. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 7, 2019 Share Posted October 7, 2019 The rule of thumb for tube length is 8 to 9 times the tube diameter. Even though we can construct functioning burners using mostly plumbing parts, the dimensions are still critical in getting the results we want. Optimum burner tube length is a balance point between being long enough for good mixing of the fuel and air and loss of velocity due to friction of the fuel/air mixture on the tube's inner walls. The orifice of the jet has to be about the right size to induce the correct amount of air as the pressure increases for the diameter of the mixing tube. The distance between the end of the jet and the opening of the mixing tube affects the fuel/air ratio in a significant manner as well. Is the end of your burner tube sticking into the forge chamber at all? It should be up inside the insulating layers of the forge chamber to keep it out of the hottest portion. Generally speaking the mixing tube outside the forge should be a little cool to the touch when it's in operation. If you need to cool it down then it's either mounted poorly or it's not functioning correctly. All naturally aspirated burners will have a minimum pressure required to function at all, and it's not uncommon for a little more pressure to be needed to keep them from backfiring/burning in the mixing tube when the forge is glowing. In my experience with that type of burner, the minimum functional pressure tends to be around 2 to 3 psi, but each burner/forge setup produces some variation in the threshold. Quote Link to comment Share on other sites More sharing options...
dhughes Posted October 7, 2019 Author Share Posted October 7, 2019 17 minutes ago, Buzzkill said: The rule of thumb for tube length is 8 to 9 times the tube diameter. Even though we can construct functioning burners using mostly plumbing parts, the dimensions are still critical in getting the results we want. Optimum burner tube length is a balance point between being long enough for good mixing of the fuel and air and loss of velocity due to friction of the fuel/air mixture on the tube's inner walls. The orifice of the jet has to be about the right size to induce the correct amount of air as the pressure increases for the diameter of the mixing tube. The distance between the end of the jet and the opening of the mixing tube affects the fuel/air ratio in a significant manner as well. So do you not get that heat conduction problem with a shorter tube too? I followed Frosty's rules to the tee (he he) until just recently when I replaced with a longer tube; it should be noted that before with the 6" tube, the temperatures were no different but there was more backfiring behavior. As the forge got hotter it would need more like 8-10psi to stop backfiring. The nozzle of the burner is indeed recessed quite far back, perhaps 1/4 inch into the shell, while the insulation + mizzou extends about 2.75" past the shell. I guess it could go further back; I'll experiment. That's interesting about the temperature of the mixing tube being cool to the touch... there's definitely something different happening there then. Mine gets hot enough to vapourize water instantly. It sounds like I need to try a few different burner designs with variations on the jet intrusion distance / air opening position. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 7, 2019 Share Posted October 7, 2019 There are a few possibilities. If the burner port in your forge is significantly oversized compared to the mixing tube and you are running full out with the exhaust openings mostly closed off, that can force heat and/or flames to exit the forge around your burner tube. Normally if the port diameter is just a little bigger than the mixing tube diameter it will result in secondary air being drawn in around the mixing tube. You can stuff some excess fiber blanket in the opening if you think that's happening to see if there is any change. If the end of your mixing tube is only about a quarter inch past the shell that should be fine unless the burner is aimed in such a way that the main portion of the flame is impinging on the insulating layers before it gets to the forge chamber. That could result in both poor overall burner performance and and heating the end of the mixing tube. I used a 1/2" T burner with a 4.5 inch long mixing tube in a forge where the shell was a disposable helium tank. I could get to nearly white heat with it. Startup was a little touchy as I had to run low pressure for a while to keep from blowing the flame off the end of the burner until the forge interior began to glow. After that I could run wide open (for me that's slightly over 20 psi) without issues. I've since moved to a naturally aspirated ribbon burner which also uses the T burner design to provide the fuel and air mix, but I had to modify some of the dimensions to get the results I wanted. When troubleshooting try to get in the habit of changing only one thing and then testing so you know when you find the root cause of your issue. Quote Link to comment Share on other sites More sharing options...
dhughes Posted October 7, 2019 Author Share Posted October 7, 2019 In my first round of troubleshooting I did try stuffing up the cavities around the burner as it fits in the port, preventing cold unmixed air from getting sucked in. It's possible that the Mizzou lining around the insulation at the port opening is causing turbulence or reflection of air; it's kind of cracking away because it's so thin anyway... I'll remove it and coat with ITC. That's inspirational to hear regarding your helium tank forge. After all this work, I want a white hot forge too! Yes, when I try these different suggestions I'll keep to a scientific schedule of one thing at a time. When the weather clears up I'll take some pictures of the results of different changes. Thanks for all the help so far! Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted October 7, 2019 Share Posted October 7, 2019 If the flame is impinging on the the insulation layers before it gets to the chamber this may be a case where at least temporarily you want to insert the burner further into the forge (still not beyond the insulating layers though) to see if it improves your situation. Quote Link to comment Share on other sites More sharing options...
JHCC Posted October 7, 2019 Share Posted October 7, 2019 1 hour ago, dhughes said: The metal is nothing like the colour or malleability I see in forging videos. Videos aren’t a reliable guide, as the sensors usually can’t handle the incandescence and extra infrared light. I’ve videoed my own forging and noticed that the metal in the video usually looks a lot hotter than it did in real life. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted October 7, 2019 Share Posted October 7, 2019 Don't be at all discouraged. If there was anything really serious about burner of forge, you would never have gotten up to orange. A little more work will get you to yellow. Quote Link to comment Share on other sites More sharing options...
dhughes Posted October 7, 2019 Author Share Posted October 7, 2019 3 hours ago, JHCC said: Videos aren’t a reliable guide, as the sensors usually can’t handle the incandescence and extra infrared light. I’ve videoed my own forging and noticed that the metal in the video usually looks a lot hotter than it did in real life. I'll keep that in mind, thanks. 1 hour ago, Mikey98118 said: Don't be at all discouraged. If there was anything really serious about burner of forge, you would never have gotten up to orange. A little more work will get you to yellow. Thank you sir, I'll keep at it. Quote Link to comment Share on other sites More sharing options...
slanwar Posted October 8, 2019 Share Posted October 8, 2019 20 hours ago, dhughes said: It's 3/4", and thanks, I'll experiment with larger tips. The tube is 8" long. I did start with a 6" tube, but invariably the heat from the forge would conduct up to the burner nozzle and it would ignite in the Tee chamber, sputtering unless the regulator was turned way up. The longer tube I have found solves this unless the forge has been running for a long time (hours) and then I can wet the burner intermittently to cool it off. The air regulator mechanism is something I wanted just in case it fixed the problem. Typically I keep it all the way open now, as fiddling with it doesn't improve much. I could stick a 1/2" tube on there give it a shot too, if you think that's more appropriate. Thankfully that hardware is just a few dollars! Heh, I'm beginning to appreciate the thought of a coal forge more and more. But I feel there's hope for this gas forge, since lots of folks seem to have more success. I have a propane forge I built with 2 burners and will take a lot of time to get some metals yellow but others - rebar for example only orange, so I built a coal forge and I learned to not take phone calls when heating metal.... Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted October 8, 2019 Share Posted October 8, 2019 I once bought a big (sometimes called a railroad) forge once with a damaged firepot. The fellow had been heating a piece of RR rail in it to work on and got a call. He rant in and said "Can't talk I have steel in the fire" and ran back out to see a piece of rail on front side and a piece of rail on the back side and a tower of sparks in the middle. I keep hoping to find a replacement firepot cheap; but most I've seen are priced at 3 times what I bought the forge for or greater! Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted October 10, 2019 Share Posted October 10, 2019 Another way to handle an overheating burner is to change it out for a smaller burner that can be turned up higher... Quote Link to comment Share on other sites More sharing options...
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