New Guy Looking for Evap Advice

[thebbqman]

Hey, everyone. I'm new to the forum and new-ish to this fine hobby. I bought a very-used oil tank evaporator that needs a little TLC and some parts. The seller didn't seem to know much about it. I'm hoping you can all steer me in the right direction. I'll try to attach some photos to this post. Here are my initial thoughts and questions:
1. General thoughts/ideas?
2. There is an opening from the upper pan frame to the lower pan frame and from the lower pan frame to.... something. I'm guessing this is for a gravity type feed between the pans. How do I use these openings and make these work?
3. There are what appear to be some racks inside the firebox. Any idea why they are there or what they are for?
4. There is a small divider/wall at the bottom of the tank about half way through - why?
5. For a pre-heater, I am thinking of inserting a copper coil (1/2" or so) into the flue stack (not around the outside) so the flue gases will heat the coil and incoming sap via hot gas convection.
6. Other than aesthetics, is there any reason to clean and paint this monster?
7. Should I look to fill the bottom of the firebox/lift the fire to get the heat closer to the pans?
8. I'm also thinking I need to fabricate a door and extend the flue pipe
9. What kind/type of wood do you use? Where should I get it? Next year I may cut down some of my oak trees that masquarede as maple trees when they don't have leaves.
10. Not sure if I should use two single open-flat pans or the fancier-looking pans that have the little dividers in them. If I use the dividers, should there be an angle to the pans, or should they be level?

Well that's probably 8 too many questions for my first post on here.... thanks in advance!
Jay

Brookline, NH


11904119051190611907

[maple flats]

Welcome bbq, this is a warning. Get out while you still have not caught this unquenchable, incurable disease. Once you get into it there is very little chance to ever get out. However, if you are not going to heed my warnings, I'll attempt to answer the questions. The answer to 1 is above.
2. It looks like you have the arch to a drop flue evaporator or maybe just 2 flat pans. The opening from the back pan will feed the lower one, either by use of a manual valve or possibly a float box on the inlet to the lower pan. My guess is it's just a manual valve. Once you get about 1.5-2" in each pan, with the manual valve between them closed, start the hottest fire you can. Your wood should be split wrist size and be about 3/4 the length of the firebox. When the syrup is ready to draw off, the valve will be at the opening in the lower section. You will want a thermometer to watch the temperature. When the boiling sap reaches just over 7 degrees above the temp of rapidly boiling water (at that barometer reading, it changes with the barometer), it will be time to draw off some syrup.
4. It looks like the back wall you ask about might be the rear support for the grates. I'm not sure about the front grate support, you may need to weld or bolt one just inside the door opening and down a few inches. One big question is the combustion air inlet, does the door have a BIG adjustable air inlet. Even if it does, you need to get air under the grates, and if you think you can run without grates, you will be hard pressed to get a hard boil in the pans. Personally, I would cut a large air inlet below the door. It should be a minimum of 70 sq. inches or more is better. Then in use, you will adjust the opening, but when I used my air inlet with no blower, my 6x14 opening was usually propped up (open) about half way (it had a door mounted at the top and a built in ratcheting adjustment bar held it up. From the back of the firebox, you should build a firebrick wall either straight up or maybe a slope up to within .5-1" of where the bottom of the flues or the bottom of the flat pan bottom will be. This forces the heat up to get better heat contact. Behind that wall, you can fill it with vermiculite (buy it from a commercial greenhouse supply, not a garden center for the best price by far. On top of the vermiculite, either lay a layer of half (thick) fire brick, or you can just put a layer of dry refractory cement, then mist it several times with water. It will set and cure to hold the vermiculite in place. You can also use dry mortor mix or even sand mix, but they are a second choice.
3. Those "racks" could be to support firebrick. If possible, the whole fire box area should be fire bricked to both protect the steel and to insulate so a higher % of the heat gets to the pans.
5. Bad idea, a coil inside the stack will boil the sap in the coil and burn some on the walls inside the pipe. For a good stack type preheater, search out one designed by Johnny Cuervo on this forum. He made one several years ago and has some pictures and a description of how he did it.
6. If you choose to paint it, use BBQ paint or it won't likely hold up to the heat well.
7. The grates I speak of will hold the fire up closer to the pans. You want between 16 and 18" from the pan down to the grates, then fill the firebox 2/3 full and refill every 7-8 minutes buy the clock (I ran every 7 before I added high pressure air over fire, now I do every 9) AOF is nice, but likely not in the cards for a starter rig.
8. Yes, you need a door, and depending on the height of the grates in relation to the bottom of the door opening, the draft could possibly be in the bottom of the door.
9. Use any dry wood you can get. A mix of hard and soft is real good. Old pallets cut up are great, just be sure the wood is dry. For starters, decide how many taps you will start with, then calculate the syrup, usually about 1 qt/tap is a safe figure. Convert that to gal. and for each gallon on such a starter rig figure you want 1 full cord for every 15 gal. When you get the efficiency up you might be able to get 20+ gal. / full cord, and a well tuned set of pans with a syrup pan and a flue pan can get up to 25 gal/cord. A full cord, is 4' x 4' x 8', split and well stacked, so if your wood is cut at 16", you will need 3 stacks 16" x 4' high x 8' long for every 15 gal of finished syrup.
10. The deviders will help you make syrup easier, but either will work. If you use dividers, the pattern is that there is an opening in one end (usually a cut out corner) and then in the opposite end of the next one, creating a serpentine flow pattern. If you don't go with dividers you will need to process in batch method, meaning, you keep adding sap while boiling to maintain the 1.5-2" depth (to become 1-1.25" depth when you get well acquainted with the process) until the bottom pan is all at the right temp. Then just maintain that depth while the fire dies and only draw off after the fire is out. The top pan will not get drawn, it will just be used to maintain the level of the lower pan, and as that evaporates and is also fed into the lower pan, you need to keep adding to the top pan.
Good luck! If you get all of this set up you will officially have the incurable maple disease, welcome aboard!!!

[RC Maple]

That is a great reply with a lot of good information. Part of you question 10 asked if you used a divided pan should it be at an angle or level. The pans should always be level whether flat or divided. I too say good luck with your project. The whole process of getting started where you are is a lot of fun and Flats is right, it is addicting.

[Sugarmaker]

Not a bad looking starter evaporator! I didnt see the pans? I would a least paint the outside with High temp black paint. You may want to get fire brick or arch board for the firebox. Fab a nice insulated door. Get the pans set on and shoot us some more pictures.
A good picture creates a thousand comments:)!
WELCOME TO THE FORUM!
Regards,
Chris