Scorched Flues

[ecolbeck]

I had an incident the other day where I burned the drop flue pan. I believe it happened because the arch was slightly out of level (even though I had carefully set it up the day before) and the float valve was not keeping up with demand (I was running blower at full speed for the first time). There is char deep in the flues. Cleaning it out has not been fun.

My questions are:

1. Has this happened to anybody else or am I just special?
2. How is it possible to burn the deepest part of the flue? I understand burning the top of the flue or the syrup pan but not the part where there is at least a 5” column of water above it.

Thank you for your insights and for admitting me into the club of “Those who have burned things.” Will my plaque be coming in the mail?

[HillsideMaple]

Check how close your insulation or firebrick is to the bottom of the flues. That’s the only thing I can think of. If it’s too close it could be creating hot spots in the flue pan. Not sure about the plaque.

[ecolbeck]

Check how close your insulation or firebrick is to the bottom of the flues. That’s the only thing I can think of. If it’s too close it could be creating hot spots in the flue pan. Not sure about the plaque.

Thank you for this insight. How close would you say is too close?

[Sugarmaker]

Yes your special. Keep looking for the plaque!
I would say this is somewhat unusual to burn the lower parts of a flue pan. I really have never heard of it happening. The only way I can imagine is for the flue pan to be partially full of over cooked syrup which eventually catches fire and burns. I guess this could happen. but prior to that happening the front pan would have been on fire for maybe many minutes prior to that. Something is not right here.
There are some basic boiling principles that we can sometimes miss but are crucial to avoiding bad things happening.
1. Your only 10 seconds away from disaster at any one moment when running one of these. I dont care who you are or what rig you have.
2. If you have fire in the arch you must have a depth of liquid in the pans.
3. All valves/ systems must be able to provide adequate flow to keep the pans to the desired depths.
4. Have the OS buckets ready at all times.

Yes that would be the last place I would expect a fire to happen. Congrats!
Regards,
Chris

[HillsideMaple]

My pan has a 1” gap between the insulation and bottom of the flues. My set up is raised flue though, I’m not sure what the recommendation is for drop flue pans.

[Kbrooks80]

By any chance did you have a foaming issue when this happened? I just saw a pan that had a good 1+ inch of sap in the front (finish area) when it burned to the point it warped the bottom about 3/4 inch. We figured it was from the foam reaching the bottom.

[DrTimPerkins]

By any chance did you have a foaming issue when this happened? I just saw a pan that had a good 1+ inch of sap in the front (finish area) when it burned to the point it warped the bottom about 3/4 inch. We figured it was from the foam reaching the bottom.

I second that thought. Having a lot of niter in the flues when the liquid level dropped could also contribute to scorching.

[ecolbeck]

I was literally boiling the first 30 gallons of sap of the season so there was no syrup and no niter. I had sprinkled in some defoamer so that was under control. Thank you for helping to troubleshoot this. Glad to know I’m special!

[marlmucker]

Curious, how close is to close for insulation and firebrick? I just modified my setup to close off the ramp and force the fire under the flues more. I left approx. 1.5-2" gap.

[Brian]

I run a drop flue 4x12 and set the blanket against the flues and have done this for at least 15 to 18 years with no problems.