h-m Posted September 25, 2015 Share Posted September 25, 2015 hello all, i am looking for some help on burners in my propane forge, i build a couple different styles of venturi burners and they worked fantastic on the cement block and then i closed the door to my very large forge and couldn't get any heat out of them, backpressure i am sure, so, i went to some blown burners and i have one in there, but i am concerned that it wont make enough heat. i used 1-1/4 x 9" black pipe, 1-1/4" TEE a gas jet with an .035 mig tip stuck in the side, an old blower from a powervent hot water heater hooked up to the run and i put concentric tubes in the middle of the burner for a flame holder, and i seem to struggle to get heat out of it. i hooked this blower up to one of the ventrui burners and i could get heat in minutes, but this one is struggling. do you guys think my blower is too small, my burner tube not the right size, maybe shouldn't have the flameholder tubes welded in the end? what do you guys think, should i go back to 1" for the burner tube, or go up to 1-1/2" or maybe my blower isn't putting enough air over there? i don't know right now, i am thinking of using my venturie burners hooked up to the blower, i suppose that might work too? let me know what you guys think? i will try and get some pics of stuff up here too.thanksmicheal Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 25, 2015 Share Posted September 25, 2015 Welcome aboard Michael, glad to have you. If you'll put your general location in the header you might be surprised how many IFI members live within visiting distance.My best suggestion for you is: Stop trying to figure out how to make burners work and follow one of the many sets of directions for making the things. Just by your description I have to say you don't know how either basic type works.Before any of us can be much help you need to at least post pics of your burners. Pics of your forge will help and once they get operating pics of them running so we can help you tune them.Just be careful NOT to pay a lot of attention to "help" from guys with not much more experience than you have.Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 25, 2015 Share Posted September 25, 2015 blown burners don't need much in the way of an orifice, many just dump the gas in an meter it with a needle valve.without seeing exactly how it's set up it's hard to do more than guess. Like how much of a blockage is that flame holder? Quote Link to comment Share on other sites More sharing options...
h-m Posted September 25, 2015 Author Share Posted September 25, 2015 thanks Thomas, yes i know that blown don't really need an orfice, i just had the hose hooked up to that supply so i used it, i will probably just pull the tip off and dump the fuel in. i am guessing that that flameholder is actually stiffling my air supply, i kinda thought that when i got done welding it, but thought i would see how it worked, i am going to stick a new piece of burner pipe on tonight and see if that works, sans flame holder, can't hurt right. how much air for a blown burner? i just canabalized this old water heater for its powervent fan, it might not really be many cfm, it is a small squirrel cage,i am going to get an old cloths dryer and cut the fan out of it, i am betting that should provide ample air, saw that on here or abana, can't remember which right now. just basically a work in progress.thanks all. Quote Link to comment Share on other sites More sharing options...
Latticino Posted September 25, 2015 Share Posted September 25, 2015 The concentric tubes should be at the very end of your burner assembly, just before entry into the forge, not in the middle of the burner. Typically this section is rather short, to give some backpressure creating the flame arrester without adding so much friction that less fuel/gas mixture gets out the business end. As usual, Frosty is right and photos will help with diagnosis.You were certainly correct that closing off the forge will choke off the ventauri burners, not allowing them to work properly. Why didn't you just adjust the forge door opening?Gas orifice size does make a difference in blown burner design as well, though not quite so critical as with naturally aspirated burners (ventauri). The orifice size, location of same, flow direction, mixing length and configuration of the mixing chamber all make a difference in how well your air/gas mixture is combined, which has an effect on the efficiency of the combustion. I have seen side entry work quite effectively. Is your burner running rich or lean? How far from the burner outlet is the flame showing? How long is your burner assembly, and how many elbows does it have? Does it burn well outside the forge? What was the rating on the burner you took the blower from (BTUH)? Lots of variables here, which is one of the reasons I used an industrial burner assembly on mine... Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 25, 2015 Share Posted September 25, 2015 (edited) For my blown system the blower was rated at 150 cfm and runs fairly choked down. As I recall the pipe used was more like 2" the gas inlet was a crimped piece of 1/4" copper tubing with a hole drilled diametrically to help mix the gas. (The pipe also made a right angle bend for mixing as well) This was built during a SOFA gas forge building workshop around 20 years ago...I've accidentally melted steel in it before. Shell was 10" diameter grain auger tubing. Edited September 25, 2015 by ThomasPowers Quote Link to comment Share on other sites More sharing options...
h-m Posted September 26, 2015 Author Share Posted September 26, 2015 I pulled the burner tube with the flame holder on end and put a 1" x 6" tube on for burner tonight it burned much better tonight. Still not as hot as I think it should be 1 burner in their and it took about 5 min to get a 1/2 round bar to red heat. It is a large forge though so maybe I am in ball park now Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 26, 2015 Share Posted September 26, 2015 Try a 1"x8" tube on the front burner. It appears to be a Reil style linear burner flame holders aren't going to work well on these.The floor of the forge is a V and the flame is aimed directly into the center. This will increase back pressure a little and retard heat circulating.The forge is large, how large work are you planning to doing? You mention heating 1/2" stock, this is not an appropriate size forge for working stock that small. The closer the forge walls to the work while maintaining room for flame circulation the more efficient it will be. The ends need to be closed up significantly, it's not an all or nothing thing. Start blocking the ends and when the burners stop operating efficiently open it back up a LITTLE till they're working properly.Adjust by stages, one thing at a time. If you change several things you'll never know what did what to the system.Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
h-m Posted September 27, 2015 Author Share Posted September 27, 2015 Alright I think I m getting my burners figured out! 1-1/4 tee 1-1/4 a 8" burner tube just straight piece of pipe no flair no bell. Propane coming in side of tee 1/8" schedule 80 pipe secured just at edge of run thru tee. Blower from the power vent water heater running wide open thru 1-1/2 pipe. Gauge says 9 psi lp pressure but I don't trust it. Think it is 1/2 that for real. 1/2" round bar took abt 3 min to get to cherry heat. Much better than I have been doing. Flame seems to burn stable. Think I m getting closer! Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 27, 2015 Share Posted September 27, 2015 That'll work. It's still an awfully large forge. What do you have in mind doing? A lot of us build BIG forges when we're starting out only to discover we only use a small volume, say 9"x9"x6" most of the time.Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
h-m Posted September 27, 2015 Author Share Posted September 27, 2015 Thank you Frosty. Beginners error. First forge. will be making sabers but i realize now most time will be using it for much smaller projects. And I happened to just use stuff I had laying around. It is an old 100 lb lp tank. Thanks all Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 27, 2015 Share Posted September 27, 2015 Common story for newcomers to a craft. We all imagine what we need before we know what that is. Done it many times.Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
h-m Posted September 29, 2015 Author Share Posted September 29, 2015 ok now i have finally found the sweet combination for this forge. i just put together a new burner again. this one is the cats meow now. 1-1/2" tee, 1-1/2" x 8 burner tube. propane coming in the tee side via a 1/8" sched 80 nipple, not quite 1/2 way across the tee run, hooked up to my wimpy blower, but i throttled it to almost off and cut the propane way down and she heated like a mad man! guage shows 9 psi adjusted way down with a needle valve at the burner. this burner was HOT! i throw 3 of them in there and i will melt the whole thing! now i can get to weld heat the whole chamber so i can weld. tomorrow i will give it a real run on first little project and see what happens. i will get some pics of it running hopefully tomorrow. i will rebuild my regulator so i know that it is working and i should be good to go!! thanks all.micheal Quote Link to comment Share on other sites More sharing options...
h-m Posted September 30, 2015 Author Share Posted September 30, 2015 Used this forge tonight for a little while. This burner is great for this combination. It runs good and I can throttle air and fuel down to control heat! Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 30, 2015 Share Posted September 30, 2015 Good! It's always good to see someone with good working gear.Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
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