Cleaning bottom of sap pan, it is necessary?

[randomseeker]

I am still cleaning up, I am embarrassed. However, it has occured to me perhaps I could get away with just cleaning the sap side of my raised flue pan and not blast off the soot on the bottom. Is there any data out there regarding how much insulation is provided by the baked on soot? When I do wash it off it is only a millimeter thick. Would this inhibit heat transfer significantly?

[tcross]

i brush the bottom/fire side of my flue pan whenever i drain the flue plan, to clean it during the season... basically only a hand full of times a year . after the season it gets another good brushing but i don't dwell on it being shiny new looking. the first time you fire it up it's going to collect soot. i think the soot may slow your boil down a tad, but i assume its marginal due to the fact that it collects soot as you boil on it. if you never cleaned it, you may notice a bigger difference, but i find that brushing it a hand full of times during the season, it'll preform real close to as new. I'd say clean it, but don't get to overly concerned with it looking shiny new!

[ennismaple]

We clean the underside of the flue pan with the flue brush every day before we fire up. It doesn't take long and even if it improves your boil by 5%, over the course of the season that's a lot of time and fuel saved.

[randomseeker]

You clean every day underside? My evaporator holds the sap/syrup between days so I cannot move the pans. Do you empty your pans daily? I'm missing something. Your machine is obviously larger than mine and I cannot imagine pulling my pans off daily - the evaporator design prohibits it. And I cannot get underneath it.

[MISugarDaddy]

I believe he is referring to using a flue brush attached to a pipe or similar device to brush between each flue before firing. This can be done from the firing door if you don't have an access door at the opposite end of your arch. Our current arch has an access door under the chimney that allows direct access to the flue pan for brushing the flues. I also brush the flues each morning before firing up the evaporator. It is amazing how much soot drops off from the flues with this process. When the season is over I do as you are doing and power wash the bottom of the flue pan to remove as much soot as possible, but all of it never comes off.
Gary

[therealtreehugger]

If I remembered, I would brush off the bottom of the flue pan before I light it each time. I have been using just a metal rake. Under the firebox area, it gets pretty sooty, and taking the layers of soot off I am sure increases the boiling rate. I get as far as I can, but can’t get all the way, because the back part only sits a few inches above the firebrick, and it’s too tight to get the rake in there. I could probably fashion something to fit.
At the end of the season, when the pan is emptied, it comes off the evaporator, and the entire thing gets a really good washing and scrubbing.

[buckeye gold]

I use one of these on a long hancle everyday before I build a fire. It get's most of the soot and some of the creosote. Makes a difference. No need to drain anythiing. At the end of season the final cleanup includes completely cleaning the bottom

https://www.amazon.com/Weber-18-Three-Sided-Grill-Brush/dp/B08M455M22/ref=sr_1_21?crid=2AK3KKNZQOF3S&keywords=grill+brush&qid=1665315974&qu=eyJxc2MiOiI1LjI3IiwicXNhIjoiNC45NiIsInFzcCI6IjQ uODcifQ%3D%3D&sprefix=grill%2Caps%2C391&sr=8-21

[maple flats]

When I was still collecting and boiling sap, I used a flue brush to clean the bottom every day. A few times over the years i missed it and i could notice a difference.
For those who ask how when the pan is full, to clean the underside you only use a brush on a long (pipe) handle to get rid of the soot and fly ash that is stuck on the bottom. On my last evaporator I had to use a 2 piece handle, because the evaporator was only 4.5' from the back wall, so I couldn't get a 7' handle in thru the rear cleanout door, I had a handle made up of 2 lengths of 3/4" black pipe, one 4' and one 3' with a coupling to join them. I never found I could get a good cleaning working thru the front door.
I never found it necessary to clean under the syrup pan. Anything on there seemed to burn off with a proper fire under it.

[ennismaple]

Our syrup pan comes off every day to be cleaned and remove nitre. While it's off and after we take the ash out of the fire box, we climb into the fire box and push a flue brush attached to a 10 foot pole (1/2" EMT) through every channel on the underside of the flue pan. The few extra minutes of prep work saves a lot more boiling time (and fuel).

[randomseeker]

Really great feedback everyone, and thank you!

I have a Smoky Lake Silverplate with a 24” x 60” sap pan. There is no access to the raised flues from either end of the sap pan proper, but if I remove the syrup pan there is about 10” of overhanging sap pan into the arch. I could therefore get a brush, angle it up and into the raised flues to brush down some of the soot. It would be very difficult to direct exactly where inside each raised flue the brush was contacting though.

When, at the end of the season, I remove the sap pan for cleaning the soot build up is 1mm or 2mm at most. Would I be losing much heat transfer through that little soot? My stack temperature is around 1000 degrees F so it is burning pretty hot under the flues.

Does anyone have a calculation to determine the heat loss through 1mm of soot?

[ennismaple]

When, at the end of the season, I remove the sap pan for cleaning the soot build up is 1mm or 2mm at most. Would I be losing much heat transfer through that little soot? My stack temperature is around 1000 degrees F so it is burning pretty hot under the flues.


If your stack temp is 1000F you're losing a LOT of BTU's up the stack. I've never done the math but a couple mm of soot will significantly inhibit heat transfer into the pan. We've been working to optimize our primary and secondary air flow rates and how much wood we use in each fire to keep our stack temps to 600F. We've found that the difference in boil rate is nominal with significant reductions in wood burned, plus we're less likely to get scorched nitre in a long boil.

[Swingpure]

We've been working to optimize our primary and secondary air flow rates and how much wood we use in each fire to keep our stack temps to 600F.

What do you use to measure your stack temperature and how high up from the evaporator do you measure it?

Thanks

[randomseeker]

I use a SmokyLake digital control unit that has a probe for the stack, which I measure about 4 feet off the bottom of the stack.

[randomseeker]

That's interesting. At 900 to 1000 degrees I get the highest boil off rate. 600 is the bottom of the range at which any boil off happens. It doesn't take any more wood per stoke to go from 600 to 1000, it depends upon the bed beneath the feed. If I can get the coals really hot I get the higher temperature. I don't have good data to show much much boil off I get comparing temperatures. This is very interesting. I will have to do some reading on this.