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Archie Zietman

Blown Burner Blowing Out, Unable to Start

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Hello Folks,

I'm sure that this question has been addressed before, but I couldn't find an appropriate thread with search. I have just build a very small blown gas forge, interior dimensions are 3 inches wide, 5 inches long, and 4 inches tall, lined with Kaowool and Satanite. My burner is blown, 3/4 inch black iron pipe with a 60cfm Fasco blower providing the air, and gas coming through a standard low pressure grey hose at 1psi, regulated by a needle valve, and comes out of a .035 welding tip. My problem is this: When I turn on only gas, it lights up with an appreciable flame, mostly in the forge chamber, so the flame holder seems to be working fine. But when I turn on the air, even so little air that it's hardly a whisper, the gas flame blows out, and starting air first and then gas isn't working. I can't even get it started. Any suggestions? I'm thinking that maybe the forge chamber is too small for the burner? I really have no idea. If you need pictures, I'll put some up.

 

 

Thanks in advance,

Best,

Archie

Edited by Archie Zietman

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Just a guess, can't see how you're set up, but a .035 tip in a 3/4" tube can be set up as a standard venturi burner, which can move all the air that it needs. I believe a blown forge can be run at low psi, but it needs to flow a good volume of gas. Maybe try it without the mig tip. Also, there're tons of pics around with examples of blown burners which have some form or another of expansion chamber as part of their design. Even a standard 3/4" venturi burner may be a lot of burner for the size forge chamber.

 

Good luck with the burner, Craig

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Personally I use high pressure hose because I switch back and forth between a blown forge and my atmo forge...when lighting my blown, I light the paper make sure its going put it in, go back to my tank and turn it up to 2-3 psi to get the initial light, lots of flame coming out of the openings at this point....( side note make sure the over is closed on the blower so the gas mostly goes up into the forge and is not spilling out onto the ground, when its on the floor makes for fun times when leftovers from the paper light hit the ground ) Ok so its lit lots of flamage, I run up hit the blower, run back to the tank ( mine is on the other side of the tent from the forge ) and when the blower gets going I dial the psi back down to manage the forge...

 

Maybe this will help maybe not...

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If it's a blown burner and you're controlling the gas with the needle valve, maybe the mig tip is causing the trouble?

 

Mine has no tip.

 

It's all pipe. It's the same burner from the Ellis's site.

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depending on the blower you may need to completely block it up to starve it of air . I have run burners with mig tips and more accurately holed gas tips with no problems whatsoever . having a mig tip or sharp restriction in the gas line increases the gas speed and makes flashback less likely (or so I am led to believe).

in the past I have taped the motor shut and run a burner on the air the motor was stealing through the housing at the bearing side.....

it is possable the forge chamber is just too small.

I get a jet flame of about a foot + from a similar setup.

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Being able to control the air flow as well as gas flow is quite important on a blown burner.

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standard low pressure grey hose at 1psi, regulated by a needle valve, and comes out of a .035 welding tip.

 

Your problem is the welding tip. You aren't getting enough gas at 1 psi through a 0.035 orifice. I suggest losing the tip and regulate with the just the needle valve.

 

In an atmospheric forge 1 psi though 0.035 probably wouldn't stay lit either. My atmospheric forge (0.035 orifice) needs about 2 psi to stay lit.

 

I run 5 psi through a needle valve into my blown forge burner.

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I spent the night thinking about that and how small that opening is...something larger is better in this case...

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Turns out I just had way too little gas going in, like y'all were saying. I drilled the mig tip out to 1/16th inch, and the forge lit right up. Haven't cranked it up to welding heat yet, but I've done some forging at yellow heats this morning, and annealed some copper. It'll get to welding no problem. I think I'm going to add a kaowool door to the front, just to bump up the efficiency, I was blocking it up with hard firebrick today which took a while to heat up.

 

Thanks for al your help!

Archie

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