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I've got another question, and advice depending on the answer.


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 Why is there an iron reducer on every foundry burner I see?  As far as I can tell, all you have to do is aim the burner away from the crucible if possible, and unignited propane cools only the wall down.  As far as I see, I'd rather opt out for a smaller hole and therefore smaller leak for radiation and use a tipless burner.  But if there is a reason an iron reducer is added to the end of a propane burner, then, why not instead use a ceramic fiber cover that would usually protect said iron reducer as the iron reducer?  On top of that, you don't even need to take it out of the foundry, and you could probably cement it in to place as a permanent part of the foundry, and thus avoid the need of a giant leaking hole.  Whatever an iron reducer adds to a foundry's ability to heat up is found in the method involving a ceramic fiber burner tip protector as a permanent part of a foundry. 

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  • 4 weeks later...

If you are referring to a mild steel pipe reducer, not some esoteric foundry only piece of equipment, they are certainly not required for burner operation serving chambers like forges, foundries,  glass furnaces...  However, I believe that the rapid change in diameter makes a distinct transition point between the fuel air velocity  in the mixing tube and the burner outlet. This makes it easier to tune the burner to operate with the flame front in the right location, particularly outside a chamber in free air.  High temperature castable burner outlets have been around for a long time as well.  I used them on glass furnaces back in the 80s, and I'm sure they predate that.  If you really want to blow your mind look into multi outlet burners...

 

Note, some burners require secondary air induction for proper operation as well.  That gaping hole you mentioned. Might be best to get a little experience designing, building and operating burners before you try design changes. I'm all for experimentation, but it helps to start from a proven design so you know what is an improvement and what is not.

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If you're talking about those cast iron bell reducers, those are the result of ignorance.  Like Dan said, a flare can be useful, but those bell reducers don't do anything.  Apparently one person did it on YouTube years ago and now it's gospel.   With a true flare the angle is 12 degrees.  It's easier and better to just mold that into the refractory.  

The 12 degree flare is good for venturi burners in forges.  Blown burners for all applications work better without them.

If you feel you need a flame retainer, a simple 1/4" step at the end of the burner is all it takes.

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