New burner question

[valupak]

Hello all.

 

New to the forum and blacksmithing, but have been working with metal for years.  I built a propane forge/burner.  It is a forced air burner.  It is 2 inches in diameter with a 1.5 inch reducer for a cone at the business end.  I fired it up today.  It was working great in my forge (softbrick) for about 5 minutes...nice blue flame, nice sound, great flame shape before placing it into the forge, etc.  Then suddenly, it sounded like a jet engine.  The sound was much louder.  I think the flame moved to inside the burner tube instead of outside as the tube started to get hotter.  My question is, is this a bad thing?  If so, how can I avoid something like this from happening?

[swedefiddle]

Good Morning,

 

Burners act completely different with the back-pressure of being inside a fire-box. The burner nozzle you should be able to touch a few inches away from the forge. If it is hot, the fire is burning back inside the burner instead of at the tip. I don't know where you are introducing the fuel into the burner, the further away from the tip of the nozzle, the better (it allows more time for mixing fuel/air). If the flame is going back inside the burner, you don't have enough air pressure for the fuel. Adjust the fan speed (I have my fan running full all the time, I adjust the air flow volume with a gate valve) and try different gas pressures (you may have to change the gas jet).

 

There is a reason why forges are available, ready to go. :) :) :)

 

Fill out your information properly, no name valu-pak. Might be someone close to you that may help you.

 

Neil

[valupak]

It was burning/working great for about 5 minutes, then got really loud and hot.  Figured it wasn't a good thing.

 

To describe the burner...  It is a 2" blower, some 2" PVC with a ball valve, 2" steel pipe 4" long, a 2" T fitting.  On top of the T fitting is my gas orifice which is .0625.  There is a 6" long piece of 2" steel pipe followed by a 2" to 1.5" reducer.  I can attach a picture tomorrow.

[Dodge]

Welcome to the forum, valupak. We're nearly neighbors :)

 

I had the same thing happen on my forced air forge. I am running a 1.25" pipe with a graduated ring flame holder ( Two smaller pieces of pipe inside each other with 1/8 " gap between outside pipe and each inside piece. Think spiral only closed rings) IIRC, the issue in my case was too little air for the gas volume. (Learning curve) No its probably not a good thing and I think I simply opened the choke more next time I lit it. With the reducer on yours I'm guessing its a back pressure issue but cure may be the same. Some one with clearer knowledge will be along shortly to confirm or deny this ;)

Scott

[Frosty]

Welcome aboard Valupack, glad to have you.

 

Lose the reducer on the end of the burner tube, it's most probably your problem. 2" is a mighty big burner but you can turn it down. When you reduce the diameter of the tube the fuel air mix accelerates but back pressure increases in the cube. Neither are helpful. Instead either try it with a straight pipe OR add a thread protector to the business end. the thread protector will increase the diameter slightly which will slow the mix and help keep the flame in place.

 

Frosty The Lucky.

[ThomasPowers]

I teach my students about tuning a blown burner by eye and ear when it's first lit up in the forge and then to check it as you go along and tweaking it as necessary.  I'd never assume that I'd just stick it in the forge and not need adjustment!  (and I never talk gas pressures on a regulator as those gauges tend to be off sometimes by as much as 50%!)