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Jlinner

Burner Placement

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I think I'm going to add a compressed air fitting to each burner to increase the air to fuel ratio. 

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Here is my canister after 45 minutes in the forge. The 1095 stuck together but didn't forge weld. I need more heat...

20181109_022521.jpg

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I'm assuming you've bricked up the openings as much as possible.  Maybe try a blanket of kaowool over top of the forge to try to hold the heat in better?  Not a long term solution, but it might help diagnose the problem.

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11 hours ago, Alex Middleton said:

I'm assuming you've bricked up the openings as much as possible.  Maybe try a blanket of kaowool over top of the forge to try to hold the heat in better?  Not a long term solution, but it might help diagnose the problem.

Yeah, I have all opening blocked for the most part. I think I might need another layer or 2 of refractory cement and the IR coating.

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Just the IR coating will help more than additional refractory.  And play with the size of the openings, if you have too much back pressure it'll cool off the forge a bit.

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I just re-read this entire thread to try and diagnose the issue.  I suspect it's that middle burner.  

That is to say, you need either fewer burners or bigger openings in the doors.  It looks like you're overloading the forge with gas and there's just not enough air in there to burn it all.

 

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8 hours ago, Alan Longmire said:

I just re-read this entire thread to try and diagnose the issue.  I suspect it's that middle burner.  

That is to say, you need either fewer burners or bigger openings in the doors.  It looks like you're overloading the forge with gas and there's just not enough air in there to burn it all.

 

Thank you for the reply, here are my openings. Rear opening is the first pic and front is the second. 

20181110_164926.jpg

20181110_164946.jpg

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Well, those look good...  try taking out the middle burner and plug the hole with a little wool.  I bet you'll get more heat and less dragon's breath.  Once you adjust the gas/air mix again, of course.  Start with the chokes full open and (assuming you have a pressure gauge) run 10 psi.  Once the forge comes up to heat, change only one variable (choke versus pressure) at a time.  Adjust the chokes until you get the blue flame at the burner flares Jerrod mentioned, then give it a few minutes for the heat to even out.  If you're not as hot as you want, turn up the gas pressure.  Wait a minute and check the temperature.  If there's too much dragon's breath, adjust the chokes.  Repeat each step individually until you get the desired effect, i.e. a bright light yellow interior at 2200 - 2300 degrees F.  You may be able to get hotter, but for high carbon steel that 2200 ought to do it for welding heat.  Wrought iron or mild needs up to 2400 degrees to weld to itself, which is also where high carbon turns into a sparkler and cast iron melts.

I strongly advise against running compressed air into a venturi burner.

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21 hours ago, Alan Longmire said:

Well, those look good...  try taking out the middle burner and plug the hole with a little wool.  I bet you'll get more heat and less dragon's breath.  Once you adjust the gas/air mix again, of course.  Start with the chokes full open and (assuming you have a pressure gauge) run 10 psi.  Once the forge comes up to heat, change only one variable (choke versus pressure) at a time.  Adjust the chokes until you get the blue flame at the burner flares Jerrod mentioned, then give it a few minutes for the heat to even out.  If you're not as hot as you want, turn up the gas pressure.  Wait a minute and check the temperature.  If there's too much dragon's breath, adjust the chokes.  Repeat each step individually until you get the desired effect, i.e. a bright light yellow interior at 2200 - 2300 degrees F.  You may be able to get hotter, but for high carbon steel that 2200 ought to do it for welding heat.  Wrought iron or mild needs up to 2400 degrees to weld to itself, which is also where high carbon turns into a sparkler and cast iron melts.

I strongly advise against running compressed air into a venturi burner.

Thank you Alan, I'm going to try your suggestions tonight. May I ask why no compressed air?

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I think it would totally disrupt the venturi effect.....but I've never tried either although it did cross my mind a time or two.

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They're not designed for it and compressed air is WAY too much air to be injecting anyway.  Blown burners are typically 50cfm or less, and get choked back at that.  Blown burners also don't use the small orifice MIG tips gas injectors, just 1/8" copper line and a needle valve.  

Edited to add: plus what Jeremy said.  Venturi burners have to be balanced. The gas jet pressure is used to entrain the air in the proper proportions.  If you added a steady blast of compressed air that would totally screw up that balance.  To compensate you'd need to pour insane pressures of gas into the burner, with the end result most likely being an oxidized steel still below welding heat and a huge ball of dragon breath outside the forge.

The idea is to get perfect combustion inside the forge, which is why I think you are over-burnered for the size.  The forge just can't hold it all, making it inefficient.  A single blown burner would work well with that size of chamber.  Or any size chamber, blown burners are pretty much infinitely adjustible.  Venturis are simple and extremely handy, though.  They work every bit as well as blown provided you have the right balance.

The general rule is one efficient venturi burner will heat 350 cubic inches of space.  Two will heat 700.  Putting two burners in a 350 cubic inch forge is just wasting gas and hurting the efficiency of the forge.  It just physically cannot handle the amount of gas/air mix coming in.  I have a little two-brick forge running a single venturi that I have to be careful with because the chamber is so small if I turn up the pressure too much all combustion happens outside the forge and the brick stays cool.  I'll show that one later elsewhere, it's new to me and not helpful in this thread.  Except for the efficiency thing.

Edited by Alan Longmire

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53 minutes ago, Alan Longmire said:

They're not designed for it and compressed air is WAY too much air to be injecting anyway.  Blown burners are typically 50cfm or less, and get choked back at that.  Blown burners also don't use the small orifice MIG tips gas injectors, just 1/8" copper line and a needle valve.  

Edited to add: plus what Jeremy said.  Venturi burners have to be balanced. The gas jet pressure is used to entrain the air in the proper proportions.  If you added a steady blast of compressed air that would totally screw up that balance.  To compensate you'd need to pour insane pressures of gas into the burner, with the end result most likely being an oxidized steel still below welding heat and a huge ball of dragon breath outside the forge.

The idea is to get perfect combustion inside the forge, which is why I think you are over-burnered for the size.  The forge just can't hold it all, making it inefficient.  A single blown burner would work well with that size of chamber.  Or any size chamber, blown burners are pretty much infinitely adjustible.  Venturis are simple and extremely handy, though.  They work every bit as well as blown provided you have the right balance.

The general rule is one efficient venturi burner will heat 350 cubic inches of space.  Two will heat 700.  Putting two burners in a 350 cubic inch forge is just wasting gas and hurting the efficiency of the forge.  It just physically cannot handle the amount of gas/air mix coming in.  I have a little two-brick forge running a single venturi that I have to be careful with because the chamber is so small if I turn up the pressure too much all combustion happens outside the forge and the brick stays cool.  I'll show that one later elsewhere, it's new to me and not helpful in this thread.  Except for the efficiency thing.

Just reading this wow.  Great info.  Gas is a bit much for me but if I ever decide to use a gas forge I’ll definately keep that in mind.  I may want to have a small one for heat treating.  I haven’t figured that out as of yet.

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