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Good pipe sealant for forge burners


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If you use any at all, use a paste rated for gas. The tape kind tends to get in the lines and block the jets.

 

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4 hours ago, Alan Longmire said:

If you use any at all, use a paste rated for gas. The tape kind tends to get in the lines and block the jets.

 

I know it will hold up to the pressure (I used the stuff on my hot water tank install) but how well does it hold up to the heat? I'm going to be building a new forge next week and need all of the tips haha

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Fine, thus the rating for gas.  Actually, most people don't use a sealant on the parts that get hot.  You don't need it for the gas jet, especially if you're using a MIG tip. If your burners and lines are getting hot enough to burn you on the end away from the forge, you have a bad forge or burner design.

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That won't make a bit of difference.  Any leakage will just get sucked into the burner tube via venturi effect.  

 

Do yourself and your forge a favor, though, and lose those bell reducers on the ends. They do not help anything, and if you use them with the galvanizing on them they may well kill you.  If you feel you need a flare, form it in the forge lining.  A proper burner flare is a 12-degree cone.  

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7 hours ago, Alan Longmire said:

That won't make a bit of difference.  Any leakage will just get sucked into the burner tube via venturi effect.  

 

Do yourself and your forge a favor, though, and lose those bell reducers on the ends. They do not help anything, and if you use them with the galvanizing on them they may well kill you.  If you feel you need a flare, form it in the forge lining.  A proper burner flare is a 12-degree cone.  

Is it 12 degrees or 12 to 1 ratio?

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The old school paper dixie cups (the small ones) are about a 12 degree flare.

Just as a side note, if your forge is fire brick, soft or hard, you may have trouble getting a welding heat.  Hard surface materials, like brick, are not insulators, they are just a fire retardant.  Some of the heat from your burners will get used to heat the brick to working temps and keeping it there.  A layer of wool over the brick ( and some sort of surface treatment like mizzou) will improve the efficiency of your forge by several hundred degrees at the top end.

 

Geoff 

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On a single burner forge, a small leak is not usually a significant problem. 

 

On a double-burner, it may be.

 

The gas leaving the jet at high speed is what causes the air to be entrained. Gas from the leak is relatively slow and effectively non-directional, so doesn't help to induce air itself and just mixes with the air going past. This means that the "air", induced by the gas leaving the jet as intended, is actually a (lean) gas/air mixture and the overall mixture will be richer than that from an otherwise identical, but leak-free, burner.

 

Flame temperature varies as the air:fuel ratio of the mixture changes: it peaks around the stoichiometric ratio and reduces as the ratio moves away from stoichiometric. We usually run fuel-rich to limit scaling. A leaky burner will therefore move the mixture further from stoichiometric and run cooler than a non-leaky one. 

 

There are many other things that affect the mixture ratio and a small leak might well cause a negligible effect if other things are different (jet alignment, smoothness of the transition from reducer to pipe, etc, etc), but it's usually better to aim for zero leakage.

 

I like anaerobic pipe seal myself: it sets in the joint, but the excess will wipe off. I use Loctite 567 when I have it to hand through work, but use the cheap stuff from the local plumbing/DIY supplier when I need to buy it myself. I'm in the UK, so can't offer experience-based advice on which cheap one to use in the USA. Read the spec and check it's rated for your fuel gas (Propane or LPG) when you buy.

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13 hours ago, Matt Walker said:

Is it 12 degrees or 12 to 1 ratio?

 

I think it's degrees. The point being, a very slight taper, not a big bell reducer.

 

Always listen to Tim!  

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i may be wrong but was under the impression that it was a 12:1 ratio

Taking the tangent of this angle 1/12 equates to 4.763 degrees

I have always turned my burner nozzles with a 4  3/4 degree taper and they work fine.

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I’m gonna rebuild part of the burners using schedule 80 and use sealant. I have another question on placing the burners in the forge. I used 2.5” thick soft fire brick and I was wondering do I put the end of the burners half way through the fire brick?

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Halfway, part of the way, just enough... whatever works. 

 

But not all the way, so the burner is inside, all the way through your lining in the heat.

 

Mine runs about 3/4"-1" in past the shell. I have 2" of ceramic wool, and 1/4"-1/2" of hellcote refractory lining.

Edited by Welsh joel
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In my little two-brick forge the end of the burner is halfway through, and that works fine.  Why are you rebuilding?  The tubes shouldn't get hot enough to hurt them.

 

If you do rebuild, how big it the forge? A single burner is usually enough.

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