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jake cleland

propane forge issues

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I'm in the process of building a fogg style vertical forge, my first gasser. it's 17" tall with a 9" diameter, lined with 2" of ceramic wool, for a 5" i/d 13" high. it has a 3/4" T-Rex burner coming in at the bottom at a slight tangent.

 

i just fired it up for the first time, and even with the air inlet wide open and low pressure, i'm getting quite a bit of flame out of the doors, and the burner head, which i had just barely in the inlet for it (not through the steel body) got red hot very quickly - is this normal? do i need to shape the ceramic wool at the burner inlet into more of an inverted cone?

 

any help would be appreciated.

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Jake-

 

I'm no expert, as we've only built a couple forges so far, trying out different ideas, but it sounds to me like your burner needs to be into the body a bit more. Ours have been blown burners, but we attached the burner inlet securely to the forge body (a steel 3-gal. paint bucket), & then formed a cone-shaped opening thru the wool, running the refractory lining out to meet the burner inlet. We actually formed some spiral ridges in the refrac to try & get a better swirl on the last one. Don't know if it works, but I know it gets hot inside, & the burner tube itself stays [relatively] less hot.

 

We've tried to get pic's of what we did, but they didn't show much unless you knew what you were looking at. I can post some up if it would help.

 

randy

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As far as I know, having a slight inverted cone in the ceramic fiber will help. I had my t-rex burners sitting inside the ceramic fiber, and had the fiber continue the taper of the end piece until it got into the body of the forge. The tips will get red hot, they are made from Stainless (at least back when I got mine they were) and they hold up fairly well. I've been running them for about 3 years and they are still doing a great job.

 

With low pressure and the air vent wide open you might not be getting the right air mix, you can try adjusting where the gas tip sits inside of the mixing chamber. I have mine sitting almost flush with the bottom groove of the air slots.

 

I recently pulled my t-rex burners off the forge and swapped a forced air air burner since I can run less pressure and get good welding temperatures fairly easily. I dropped the t-rex burners in my salt pot furnace and they work perfect, and very efficiently verses the homemade burners I had.

 

Hope this helps...

 

Just curious, how many PSI are you running when you say low? I know there is a certain point at which there isn't enough pressure to properly mix the gas and air which I think is around 1psi give or take... Might try bumping up the pressure to see if you are still getting flaming out the door.

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You might need a smaller MIG welder tip at the orfice, Jake. I don't remember what was in it, and may have forgotten to look. I think the one I use has a 0.7mm tip in it. They shipped with 0.8mm installed ?

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thanks guys. i think i know what the problem/s is/are - my dad has played with it since i did the test burn, and the burner flare had been moved back. should've checked, but i was excited... i'll get it sorted once daylight rolls back around (same latitude as moscow here, so light is a bit of a commodity here)

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Not sure on your dimensions but the design is sound. What I find is Its better to micro manage the mix till I get up to heat. Then if you have fire coming out of the forge its often because its not getting enough oxygen to burn the gas off inside the forge. I know it sounds simple and it is but I solved all my problems by setting the gas, then forcing more air till I had the right mix.

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also remember that venturi rely on the propane to pull in air with it... if theres a bottleneck somewhere ..it could be difficult to draw the right amount of air... --- for example if your exhaust holes are too small, maybe make it difficult to draw air in...

- not so much a worry with forced air as you have a blower

 

also i cast the burner cone into the wool about an inch and line the wool with a 36 cement... this way the burner cone is actually made of refractory and it lasts a long time... even after 10 min of running it.. i can put my hand on the burner tube and its barely warm..

 

i find my T-rex does run abit rich.. but then it keeps the scale down aswell..

 

 

take care

Greg

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Jake,

I know you already have the venturi burner but for about 15 or 20 bucks in pipe and a cheap surplus fan you could build a blown burner and have infinite controll of your forging atmosphere. I built one of Don's little forges a few years back from 8 inch pipe and 1 inch of insulation and it works great for forging. I have a needle valve to regulate the amount of propane and a gate valve on the air, using these and the regualtor you can forge at less than two pounds of pressure. I get a lot longer use of my propane fills. Heat treating leaves a lot to be desired due to the small size but is managable. You could use the venturi burner for a larger volume heat treating forge. Just a thought.

 

Best wishes

Jerry Fisher

Edited by Jerry Fisher

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