BG-14 burner issue

[Ironedge]

I have a single tier brewstand with 2 BG-14 burners. When lit, if I turn the gas up too high, the propane ignites by the back air holes at the connection. Has anyone seen this issue before and have a solution? I thought a heat shield would stop the problem, but that didn't work. The first picture is before the heat shield on the boil side, the second is with the heat shield. Not a very good picture, but I can provide a better picture later.

 

[day_trippr]

I've been running a pair of BG14s for many years so am fairly familiar with them, but could use a bit more information.
In one of those pictures there appear to be windscreens, but I can't tell how close the top edges are to the kettles. Better pictures of the screen-equipped version would be helpful.

Charles's Law wants there to be lots of open space above the burner element - the windscreens around my burners are more than a inch below the kettle bottoms, and there's lots of open space around the kettles for exhaust to "spill up" around them. So my suspicion is there isn't enough open space for the heat to flow upwards and it's literally putting up so much resistance the burner is back-firing at the venturi bell.

So the solution could be as simple as carving out some of that diamond plate decking...

Cheers!

[edit] Does the burner flame go predominately yellow just before the back-fire happens? That would be a sure indicator that the burner can't breath...

 

[Ironedge]

Makes sense. I guess the way I build the stand doesn't allow a whole lot of room for the burner to breathe. I guess I need to add some 1/2-1 inch spacers under the kettles to allow for the heat to escape up the sides. A couple of better photos are attached.

Cheers

 

[day_trippr]

Yup, that first pic is very telling. The top of the windscreen ends up very close to the kettle bottom so there isn't enough room for the hot exhaust to escape. If you could lower the screens without changing the burner height you could be home free.

fwiw, this shot shows my burner screens versus kettle bottoms, and there's just over an inch of gap between them. That puts the kettle bottoms ~3-1/2" above the burner tips. I can run this full blast without no issues...

Cheers!