Evaporator Pan Rattling

[schellmaple]

I'm boiling on a homemade 18" x 64" V bottom evaporator with a 6" stack. I have it pretty much air tight with forced draft in the door. I don't know what the CFM's are but it's real close to what I have on my outdoor stove. The problem I'm having is when I'm firing it, it rattles the pan real bad almost until the time when it's out of wood, shaking some of the sap clean out of the pan. I have reduced the blower input but you almost have to choke it off before it settles down. The only way to stop is to crack the door open. It burns like crazy then with no rattling. I put some ceramic blanket up in the ramp area and I was wondering if this might be choking it off to much. I ran this same blower with a less tight system last year full board and had no problems.

[schellmaple]

I did find the CFM's for my blower and it is 100 CFM. Does anybody think my 6" stack is to small for this blower or do you think I am chocking it off to much in the ramp?

[500592]

You should really try to put an 8 or 10 in stack

[bowtie]

my boiler will rattle the upper door when i start a fire and it gets hot quick, ie lots of cardboard, and i put a screw attached to the chain to open the door in the dooropening to let air in. you may need to rig a small door to let air in if you can not change to a bigger stack because you are creating a negative pressure imbalance. even a small opening will "fix" this problem and should not affect your boil, may even help by "reburning" the gases that are causing it. just a thought.

[schellmaple]

OK and thanks for the help. I could put in a different stack if that is what I need to do. I would just need to move the arch back over to the garage and weld a different stack size in. I now have a 6" cylindrical stack coming out of the arch. Should I go ahead and put a regular rectangle stack tapered into a 8" pipe?