Peppie

Peppie's Propane Puffer

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Once your forge is up to temperature it probably will make very little difference.  The fuel/air mix will tend to ignite immediately upon exiting the nozzles, so even if you start out with the flames lifted from the surface of the burner block they will usually settle down onto the face of the burner block after a few minutes.  At least that's been my experience.  However, to your point, the more cool fuel/air moving through the plenum and burner block the cooler it will stay and that means a lower chance of the flame igniting inside the plenum (backfiring).

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I did notice yesterday after about an hour of it running, the flame had settled down lower to the burner.

TY for the input. This is my first RB. The more ya know the better.

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Mine had lifted flames at first testing but after working through the fuel and air, it now stays at the face from start to finish.  Flames at the holes will be more stable.  You can see your flames fluttering about in the video..  It could be too much air velocity or not enough mixing before it gets to the plenum.  I don't recall off hand what the main issue of mine was that fixed it.  I tweaked a few things at the same time and ended up with a stable flame.

The face of the block is going to get far more heat from the radiation of the rest of the forge than it will from the flame base touching it.  The backside of my burner is only warm to the touch after an hour at an orange heat.  The air mo ving through it will help cool it.  I leave the blower one for a while after shutdown so the heat doesn't work into the plenum.. just trying to get longevity out of the burner.

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Paragon

I am in the habit of leaving on the blower after I have shut down the gas. (Previous forge was forced air)

The air gas mix enters the system about 4" prior to a 90 degree bend. Then it is a straight 16" to the entrance of the plenum. Do you think that 16" and the 90 degree elbow is enough to get a sufficient air gas mix? Or should I fashion some type of mixing spiral and insert it into a section of the 16" straight run?

20190524_184916.jpg

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I don't know for sure.  Far from an expert as I am still tweaking my first.  I have read that propane does not mix with air as readily or something of that sort so I went overboard with stuff I had on hand.  I would think it would work OK as I'm sure many have similar setup to what you have but I do know some have put a regular solid spiral inside and it has helped mixing.  I used perf sheet to help induce turbulence to mix it

The spiral is per sheet metal.  I heated it with an OA torch to get it to twist easily (otherwise it just wants to fold on the diagonals with the holes)  The yellow baffle is still just a test to help divert the air to all holes evenly.  I have added more holes than what is in the photo to even it out.  Eventually the plan was to use a can with holes as an insert.. eventually (the simple yellow sheet is working very well.

You may just have too much air velocity or not enough gas (basically need to find that balance - Previous post from above link is when I figured it out and previous to that was the lifted flame).. I don't remember what the key thing was to get mine to settle on the burner face but I think it was a combination of the air and gas tweaking.

 

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TY Paragon,

Where did you come across the perforated sheet metal? 

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In my garage.  Came with the house.  You can typically find it at your local hardware or builder center in the metal stock area.  Can get it online from McMaster-Carr and metal supply places as well.

Regarding the detached flame, I can get mine to detach and seems to be too little gas or too much air.

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Paragon, thanks again.

I will get some perforated metal and do a bit of tweaking once it arrives 

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