Vibrating pan while boiling

[snakes14009]

So i built a new 24"x52" pan and oil tank arch. It is boiling very well. But after an hour or so when everything is good and hot. The pan will setup a vibration resonance and literally start shaking. If i adjust the rheostat for the fan it will go away for a minute then start again. it is not coming from the fan or smoke stack, i believe it is coming from the fire rushing by the back section of the pan. the tops of my pan dividers do not have a hem. I can weld in some stiffeners if needed. but my cheap and lazy side says to disturb the fire flow in the back of the pan to see if it stops or decreases the vibration first. I have briefly watch the fire and it flows very smoothly from the firebox to the stack.

I was wondering if anyone has seen something similar before and what their solution was?



Just to answer some questions.

Pan is 24"x52"x8" the dividers are 8" the thickness is 20ga that is tig welded
The arch has standard stud insulation mineral wool so 2.5-3" thick and half brick firebricks on top of them
I do not know the CFM of the fan, i can tell you it is way more than the arch needs
the stack is 8"
1.5" gap between the bottom of the pan and the mineral wool insulation in the back of the arch.

Thanks to anyone that can offer advice with a similar problem.

[In da bush]

Maybe something is slightly warped? Also I would run pan gasket around the entire pan,looks like corners might be not covered in gasket.

[snakes14009]

the pan is sitting on gasket and is airtight in the area.

[DrTimPerkins]

Since it stops when you adjust the air, I suspect that it is either too much air OR the fan is off-balance from heating up. You said it stops when you turn down the far. After it starts vibrating, what happens if you crack open (carefully to avoid being showered with sparks) the fire door a tiny bit. If it stops...too much air. If it doesn't...far imbalance.

[snakes14009]

I like the door test I will have to try it. The fan imbalance was the first thing I checked. When the pan is shaking pretty violently the fan is smooth as a cucumber... thank you for the quick response.

[DrTimPerkins]

Open it VERY carefully and just a tiny crack so you don't get a face full of hot embers. :mad: