Several malfunctions

[kiegscustoms]

First year with used 2X6 raised flue Small Brothers Lightning Forced Draft, Auto Draw Off, Steam Hood, Parallel Flow Preheater.




We are having a problem with the fluid boiling in the center two partitions of our front pan before the syrup side. Two days ago the hot float stuck and scorched the second partition from the syrup side and blew the solder out of the back of the center two. Got that fixed but still boils wildly in the center two. The pan is level also.

Our next problem is our automatic draw off has taken on a mind of it's own. I purchased it used this year. It is an older style draw off with the bucket of water calibrater. By the time it reads the correct density on the syrup side and decides to draw off the syrup in the center of the pan causes it to spike and will finish it's cycle, and then immediately recycle pouring out mostly unfinished syrup.

Our third problem is we had 3 chimney fires last night. I live in the village so I have to have a cap and spark arrestor in my stack. I think it is restricting the flow of smoke too much.

My last concern is we are running a forced draft unit. The stack temp will run at about 850 to 900 with that running good and the back pan boils like crazy, but it blows all the heat away from the front pan. We have been running it with the blower almost off and both pans boil ok, but the stack temp stays at about 750. From past experience a rig this size should boil about a gallon of syrup per hour, but we are no where near that.


Any input would be very helpful.

[Brent]

Wow that's a handful of *&^.

The auto draw off likely has a stainless tube with a wire going down into it that has the temperature sensor at the end of the wire. On mine, it started reading funny and I found that through handlint I had managed to pull the wire and sensor up the tube about 2". To get it back down I had to very carefully cut the crimp at the top of the tube and open. Then I wrapped it with tape, push it back down and crimped it again. Fine now.

The stack fires and blower issue are tough. How tall is the stack ? How much is indoors ( if any ) You should only get stack fires if the stack is cold and the creosote condenses and builds up and then gets heated enough to burn. Sort of contradictory but if you cycle a cool smouldering smokey fire then a real hot one you could trigger fires. Is your thermometer in the stack or magnetic on the outside ... it makes a difference of 200 - 300 degrees.

Just guessing but I'd try backing off on the forced air somehow. If its directly connected to the arch, maybe try disonnecting it and just have it aiming at the openning. That will moderate the flow a bit.

[oneoldsap]

That is how lightening evaporators boil , use your scoop and move that syrup towards the drawoff . They are the easiest rig there is to burn , and the hardest to control ! Boiling concentrate on one is a real thrill !

[kiegscustoms]

The stack is about 8 feet inside the building and 5 feet outside. The cap clears the peak of the cupola so it should not be a draft issue. The stack thermometer is inside the stack. There is a small gap between the back side of the flue pan and the base stack that is open. Last night we found that if we close that up it immediately puts the chimney fire out. Keeping this gap closed raises the stack temp to 950 to 1000 but doesn't boil the front pan as well. I tried running it without the blower at all and using the stock draft door but that dropped the stack down to 500 and didn't boil at all...?

[Brent]

I think, from what you've explained about the back gap, is that you are not really getting a chimney fire, in the sense that you're burning creosote off the walls of the stack. I think, what you may be seeing, is the finishing of burning of wood gasses in the stack.

There is a good thread going here
http://mapletrader.com/community/showthread.php?t=7884

The University of Vermont Maple Research Extension had an in depth article about combustion efficiency in evaporators the in simplified terms says we need to vent our evaporators much like modern high efficiency wood stoves. That is with little or no air under the grate and inject air above the fire, down into it, to burn much closer to 100% of the wood gasses instead of blowing them up the stack and wasting them. You are injecting air at the bottom of your stack so the remaining wood gasses are burning in your stack.

There's four pages on that thread but near the end you'll see the results he is getting. Maybe a summer project for you.

[Hop Kiln Road]

My first question, are you using dry and uniform wood? I tend to use smaller pieces under the draw off side and throttle back the blower except for a minute or two right after I fire. Try firing just on your draw side until you establish the gradient. Leader says an internal stack temp of more than 830 is over-firing. I wouldn't dare to use an auto draw on a 2X6, or a hood without a sight gauge.

[kinalfarm]

do your bricks cover the edge of your pan? if so that my have something to do with the sides of your syrup pan not boiling or if you have a log touching the side of the arch it creates a dead spot under the pan. if you leave an air space that blower will push the hot flue gasses up the edge of the arch and boil more even

[kiegscustoms]

I am using dry slab wood from the mill, all split down to about the same size. I used half bricks on the top under the rail so there is nothing under the side of the pan. I agree with the thought that it is just the unburned gasses reburning in the stack. I checked the inside today and there is no creosote in the stack. The auto draw however is still confusing me. It worked perfect on the right side of the pan, but when we reversed the flow it began to take on a mind of it's own. Going to try reversing again and see what that does.

[maple flats]

You will never get creosote in the stack of an evaporator if run hot like you should. The flame you see out the top is wasted wood gas. The fire uses all of the oxygen and it re ignites when it gets air. I used to have that most of the time. I now never have it. I added high pressure air under AND OVER the fire. This burns everything before it goes up the stack. Mine is high pressure but even a squirrel cage blower pumping combustion air in will help a lot. With the high pressure it boils way faster than it ever did with no blower even though I thought it was real good before. Now it is impressive. And no flame nor sparks out the top. Not sure about a screen on top but if you must I would think you'd want to increase the size to keep from reducing the draft any.

[maple flats]

Another thing, for combustion air add much more over the fire than under it once a good fire is established I forgot, as for the boil in the center do you have fire brick blocking part of the outer sections. You want to taper the brick out so it ends at the inner edge of the top rail on the arch. I cut mu bricks at about 45 degree slope for the top 2 inches to allow the heat to spread. Even then the centers boiled a little harder than the outer. With the top air I now have that has almost stopped. It does start in the 2 center sections to boil first but shortly after the boil get almost uniform across the whole syrup pan after the top air valve is opened farther. I have a 4" high pressure supply pipe, split to 2 3" pipes, one under and one feeding the top manifold. Each has it's own ball valve. To start when I first light the top is only open about 1/4 and the same on the bottom. As the fire gets going I open the bottom about half. When fully involved I open the top about 80% and close the bottom to about 1/4. It then stays there all the time until the end of that boiling session, I don't even need to adjust to re fuel (every 20 minutes opposed to 5 before this air injection) I just open the doors and fill, no smoke, sparks or anything else comes out the doors (except a lot of heat). Getting more air should help both your flame out the top and over fire air should help even out the boil in the pan. If doing over fire air it involves making a manifold and removing some fire brick to install it then brick again to protect it. Not a project for during the season. If you want to think about it read the report I used. I will add it to this post when I find the link. Here it is: http://www.uvm.edu/~pmrc/Combustion.pdf

[Brent]

Burning slab wood could be further adding to the wood gas and oxygen starvatoion. It tends to pancake up when you load it and cook, dumping out more wood gas that does not burn in the arch.

[kiegscustoms]

I guess due to my location I will have to switch to a gasifying arch. We reversed flow last night and the boil seemed to even out a little. The auto draw still freaks out. We ran out of sap though and there is none coming in right now so hopefully it will run again and we can do some more experimenting.