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Forge burners getting hot to touch?


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So I finished my forge today lit it up and after it being on for a while the entire burners got hot to the touch. And not only both ends of the burners but also some of the pipe for gas. I know this is a safety concern so I want to fix this pronto. My theory is that the heat is creeping up the burners through the holes drilled through the soft fire brick for my burners to go through. They weren’t the best holes and left some gaps.

 

I thought making the burners longer might help but I don’t know if that would effect the burners operating correctly?
 

I also thought maybe putting some refractory around where the burners go into the fire brick to maybe better insulate it and seal any gaps?

 

Does anyone have advice on how to make these burners not heat up and be  safe to use?

 

picture below 

A7BA1208-50B7-4956-B869-543F9964FAE0.png

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1. Always plug around the burner entry with some kind of refractory. A bit of kaowool topped by clay is great.

2. While you see it a lot, top-entry burners are not a good design for this among other reasons.  

3. That forge only needs one burner judging by the size, that may account for some extra heat as well.  

 

I bet if you plug the gaps most of the issue will be solved.  Until you shut down, when the burner tubes will act like chimneys and heat it all up again.  But the gas will be off, and if you have a quick disconnect fitting at the valve you have nothing to worry about.

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27 minutes ago, Alan Longmire said:

1. Always plug around the burner entry with some kind of refractory. A bit of kaowool topped by clay is great.

2. While you see it a lot, top-entry burners are not a good design for this among other reasons.  

3. That forge only needs one burner judging by the size, that may account for some extra heat as well.  

 

I bet if you plug the gaps most of the issue will be solved.  Until you shut down, when the burner tubes will act like chimneys and heat it all up again.  But the gas will be off, and if you have a quick disconnect fitting at the valve you have nothing to worry about.

What about making the burners longer? right now they are 3/4” x 6” black pipe nipples I was thinking of replacing them to 3/4” x 12” black pipe nipples. Would this affect how the burners perform though? And do you think this would help even more with heat?

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Longer burner mixing tubes will affect how much air is induced by the high speed gas flowing into the mixing tube entry.  What size orifice did you drill and what pressure are you running at?  Can you open the shutter you are using for the air more while it is running?

 

Also, try opening the door a bit more.  NA forges are picky about backpressure in the chamber.

 

Most important: how far into the forge shell do the burners project?  The end of the flare should be no more than 1/2" past the outer skin of the forge.  Ideally there should be a thin "shelf" of forge insulation (or even better a cast refractory) that protects the end of your burner flare (those are stainless steel right, not galvanized?  If the latter junk them immediately).

 

As Alan noted, top mounted burners often have this problem.  Weirdly it is usually worse when you turn your forge down from a higher heat to a lower by turning down the gas.  This makes less gas air mixture flow through the burner, which acts to cool the burner.  As long as you are not getting preignition inside your burner (popping sounds) or the burner tube actually starts glowing you should be fine.

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16 minutes ago, Dan Hertzson said:

Longer burner mixing tubes will affect how much air is induced by the high speed gas flowing into the mixing tube entry.  What size orifice did you drill and what pressure are you running at?  Can you open the shutter you are using for the air more while it is running?

 

Also, try opening the door a bit more.  NA forges are picky about backpressure in the chamber.

 

Most important: how far into the forge shell do the burners project?  The end of the flare should be no more than 1/2" past the outer skin of the forge.  Ideally there should be a thin "shelf" of forge insulation (or even better a cast refractory) that protects the end of your burner flare (those are stainless steel right, not galvanized?  If the latter junk them immediately).

 

As Alan noted, top mounted burners often have this problem.  Weirdly it is usually worse when you turn your forge down from a higher heat to a lower by turning down the gas.  This makes less gas air mixture flow through the burner, which acts to cool the burner.  As long as you are not getting preignition inside your burner (popping sounds) or the burner tube actually starts glowing you should be fine.

I put the end of the burner about half way through the 2.5” thick soft brick so it’s about 1.25” depth into soft brick. 
 

I will move it up 

 

I also noticed it has about a 1/8th gap around the end of the burner while sitting in the hole. I plan on closing it up with refractory to where there’s no gap. I hope this will keep it from heating up.

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From what I remember- the recommended mixture tube ratio should be 1 to 8... 1x the diameter of the pipe= 8 x the length for optimal mixture.

 

This was the advice from the burner gurus on IFI... when I was building mine.

 

And my burner entrance as a sealing example.?

To the right of the blade.

 

20210303_185041.jpg

Edited by Welsh joel
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