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billyO

PID controlled forge build

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Well, it sure looks good! B)

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Thanks Alan, but how it works is what's important, because looks always fade.... (thus your B) emoji, I'm sure)

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That's the "cool" emoji, a sly smile in shades.  No slight intended.

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Don't worry, Alan.  No slight was taken.  I was agreeing with how I interpreted what you were saying...and I'm still agreeing.

Thanks for the compliment, though. Perhaps I should open it up to show the bird's nest of wires inside.....

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Looking good! B)

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Hello all.  I finally got to fire up the forge today for a little bit in an attempt to dry things out after almost a year of inactivity.  I ran it for an hour with steam exiting the entire time before shutting it down to try to minimize cracking of the refractory.  The thermocouple got to  1500 degrees for about 20 min.   One thing that has me puzzled is that when I had the tank regulator at ~4lbs, it ran fine, but when I tried to bump it up to 8lbs, the burner seemed to sputter (see pics).  

4lbs

1.jpg2.jpg

8lbs

3.jpg4.jpg

 

I don't remember ever having this happen before, but I am getting older.  Is it that I just need to let the interior get hotter before increasing the propane?

Thanks

Edited by billyO

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This is a blown burner, right?  The way I was taught to adjust those is with an air gate on the blower and a needle valve on the propane.  Tank pressure never even registered on the gauge, since the fuel line was 1/4" copper dumping straight into the air line.  

Or am I missing something?  

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Hi Alan.  I'm not sure you're missing anything.  Yes, it's a blown burner (I think, I always called them ribbon burners).  I have needle valves on the lines and there is a baffle on the blower that I've always used to control the air flow.   In the past I found that for general forging, I would have the tank manifold at about 2-3# pressure, and to create a reducing atmosphere for welding I'd bump up the tank valve to 6-8# and close the blower baffle a little.  For some reason I got in this habit as opposed to fussing with the needle valve.

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You are getting more flow than the ribbon burner outlets can tolerate and the velocity is so high at the outlet the air/gas mixture is moving faster than the flame front can burn back to the face of the burner.  This liftoff is a common phenomena.  You are correct that as the forge interior heats up the flame front will apparently accelerate and move back towards the burner outlets.  After the candling is complete, and all water vapor boiled off, I would run it at a low, stable flame until the forge interior heats then turn up the air/gas mixture.  As I've previously stated, your PID control only varies the gas, which can be a problem for overall flame control.  When I built a similar system I used a zero pressure regulator, which varied the gas in a fixed proportion to the airflow.  If you use a temperature controller to modulate the air it automatically modulates the gas as well.

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26 minutes ago, billyO said:

For some reason I got in this habit as opposed to fussing with the needle valve.

Fair enough, the regulator is easier to get repeatable settings with.

 

23 minutes ago, Dan Hertzson said:

If you use a temperature controller to modulate the air it automatically modulates the gas as well.

Good to know, thanks!  I'm getting more into using gas now that coal is so hard to find, and every bit helps.

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1 hour ago, Dan Hertzson said:

After the candling is complete, and all water vapor boiled off, I would run it at a low, stable flame until the forge interior heats then turn up the air/gas mixture.

Thanks for the info, Dan.  

I ran it today for about 1 1/2 hours and I noticed it acting more like what I was used to.  There are 2 reasons for this, that I can think of, first was what you mentioned, there was no (or only minimal during the first 5 minutes) water vapor boiling off today and the interior got to heat much quicker.  The second thing was that last night I re-read the operating instructions from the manufacturer and they say to run a 3/16" rod in all the orifices every 2000 hrs of use, so I did that too.   

I also tried the controller once it got up to 1750F for about 30 minutes and took video.  I plan on posting  it once it uploads to Youtube (it's taking a long time to upload....) 

 

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Here's a link to the video.  (the first one is 4x normal speed to save time)

 

 

Edited by billyO
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