Switching from steam pans to divided - help with evap modifications

[Openwater]

Good morning. I'm switching from steam pans on my homemade evaporator to a divided pan. The steam pans were 6" deep and sat down in the evaporator (scorched pan sides). Now, I've got a 14" x 48" pan with float box being made to put on my evaporator with a 12" x 48" opening. My stove pipe is 6" dia.

My questions are:
1. How much higher do I need to raise the fire grate?
2. I will also need to get more heat/flames/hot gas against the bottom of pan, so could I just put a couple baffles on ramp of arch to force up against bottom of pan, or should I just raise the entire bottom of ramp/arch closer to pan bottom?
3. If stove pipe is 6" diameter (28.25 square inches), how much space/area should there optimally be between bottom of arch and bottom of pan? More or less than exhaust pipe area?

Thanks for any advice/suggestions.
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[berkshires]

My questions are:
1. How much higher do I need to raise the fire grate?
If it was working well before I would just raise the grate 6 inches so the fire is the same distance from your pan.



2. I will also need to get more heat/flames/hot gas against the bottom of pan, so could I just put a couple baffles on ramp of arch to force up against bottom of pan, or should I just raise the entire bottom of ramp/arch closer to pan bottom?

Again, I would raise the whole thing 6 inches. You could just fill with vermiculite or something and then put firebrick on top of that.



3. If stove pipe is 6" diameter (28.25 square inches), how much space/area should there optimally be between bottom of arch and bottom of pan? More or less than exhaust pipe area?


I guess you would want to ramp up to the same area as your stovepipe, so about 2 1/2 inches.

GO

[Openwater]

"Again, I would raise the whole thing 6 inches. You could just fill with vermiculite or something and then put firebrick on top of that."

I'm trying to keep the arch as light as possible. Would the vermiculite be the lightest filler to use? Could I also just lay a piece of cement board on top of the filler instead of firebrick?

[SeanD]

Vermiculite is feather light. If you don't want to lay brick on top of it, it's okay to lay cement board on top. The up-side to either of those routes is you can adjust your distance to the bottom of the pan very easily and quickly.

Even lighter still would be a thin layer of refractory cement misted with water so that it hardens in place. It will eventually crack, but you are just looking for something to hold the vermiculite in place. The down-side to that route is adjusting the distance to the bottom of the pan is uneven and messy.

[Openwater]

Thanks. I'll try the vermiculite and cement board to raise up the arch bottom. Probably will line sides with ceramic blanket or mineral wool - any practical significant difference between these for just putting in sides of arch?

[Pdiamond]

MY suggestion is to raise it up to within an inch of the bottom of the pan then about 4 inches in front of your chimney vent drop it back down. That may help create turbulence and keep some of the escaping gasses under the pan longer before going out the flue and up the chimney.

[Openwater]

Thanks Pdiamond. That's kinda what I was getting at when I asked about setting baffles (bricks, etc) in the arch vs. raising the whole arch floor. I assumed adding just the baffles would create more turbulent airflow vs straight laminar air flow; wasn't sure which is best when trying to keep heat against the pans.
Stove pipe cross-sectional area is 28 sq inches; if I raise the arch floor up to within 1" of pan, it would only give me about 14 sq inches of space for airflow. Any problems with having an airflow area under the pans smaller than the arch outlet/stovepipe? I don't have a damper in my stove pipe to restrict exhaust/smoke.

[Swingpure]

MY suggestion is to raise it up to within an inch of the bottom of the pan then about 4 inches in front of your chimney vent drop it back down. That may help create turbulence and keep some of the escaping gasses under the pan longer before going out the flue and up the chimney.

Sorry to jump into this thread, but your comment and Openwater’s above yours, made me think about my evaporator. The first four pans were boiling fine, but the fifth pan, (the preheat pan) only got hot. I had raised it so it would not block the stove pipe exit, but in doing so I also raised it higher above the gasses.

My fire box is about 19” wide, if I added a brick that was 17” wide, 2 “ high, and 2” deep, at the door side of the start of the fifth pan, would that raise the gases up and create turbulence to add more heat to the fifth pan, but still allow the gasses to escape through the stovepipe, without dramatically affecting the draft?

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[Pdiamond]

An evaporator is not like a wood burning stove. you do not want to put in a damper in your stove pipe. Yes you lose some heat, but you want that fire ripping to boil off the sap as quickly as possible. Consequently that is why it takes more wood to make syrup than to just heat up a space.

[Pdiamond]

Gary, that would do the same thing.

[Openwater]

Got it. Finally starting to understand the thermodynamics. I've used wood in a wood furnace to heat the house before where I wanted long-lasting hot coals. With the evaporator, however, it sounds like we don't want just hot coals, but flames stretching as far thru the arch as possible, correct?
Last night, I welded-up some steel braces/brackets(old bedframes) to set in the arch to hold up the cementboard. Will fill the space underneath with mineral wool/insulation or vermiculite.
Any advantage to putting a skim coat of refractory cement on the cementboard? I've got a small bucket of the premixed stuff.

[Pdiamond]

won't hurt a thing.

[Openwater]

Did a test boil on my new/first divided pan yesterday (14" x 48") which is 18g stainless. Didn't get the hard boil I was hoping for. Here's my questions after test boil:
1. Is it normal to have little to no boiling in 1st channel coming from float box? I did get some boiling in 1st channel, but mainly in front of pan right over firebox.
2. Front of pan definitely boiled better/harder than back of pan, so I need more heat in back of pan. Planning on laying a piece of 2" angle iron or something about 2/3 of the way up the ramp to try to force more heat up under back part of pan.
3. Could I use a stronger/better blower for my AUF? Right now I just have a bathroom exhaust fan (100cfm) blowing thru a 4" duct into ash space under grate hooked up to a dimmer switch used for ceiling fans to control fan with 3 different speeds; I assume I get the 100cfm at the 3rd/highest speed.

Last year I boiled in restaurant steam pans that I think were only 22 gauge and the whole pan sat down in the arch so sides of pan got scorched; those pans produced a HARD rolling boil. The new divided pan did produce ALOT of steam when boiling so I couldn't even see the water surface or bottom of pan, so I'm not sure if my expectations are too high. I would really just like to make sure I get enough heat/boil to create the sap/syrup gradient and I don't know if that may be impossible if the back of the 3 channels isn't boiling as hard as the front of the channels.
Thanks for any advice or suggestions.

[Cjadamec]

I would try more air first. I did the exact same thing as you going from 6" steam pans to a proper syrup pan.

I ended up raising the floor of the evaporator with brick and ceramic blanket. It was just what I had around at the time.

You don't need the whole floor raised that high. I went with a "wedge" floor where the floor just slopes up to it's highest point for the last 6" of pan length. That last 6" has about 2 inches of clearance. I run an 8" stack. Just after the pan the flue spaces opens right back up and out the stack it goes.

If you have any inflatable lawn ornaments those can be a good source of fans in a pinch. They generally have good cfm and are positive pressure blowers.

[Pdiamond]

Openwater, what kind of space do you have under your pan from where the ramp begins? You only need about 1/2 to 3/4 of an inch under the pan in this location, then just before it exits the arch have a drop.

[Openwater]

Openwater, what kind of space do you have under your pan from where the ramp begins? You only need about 1/2 to 3/4 of an inch under the pan in this location, then just before it exits the arch have a drop.
Maybe that's my problem. Front of ramp right after firebox is about 7-8" under the pan and then ramps up to about 2.5" under back of pan before opening up into the bigger space in stack before hitting 6" pipe.
I thought I always had to keep at the least the same space/area under the pan as the cross-sectional area of the 6" stove pipe. I didn't know if it was ok to "choke" the opening under the pan to an area smaller than the flue pipe.

[Pdiamond]

I believe if you narrow that space you will achieve the boil you want. Ceramic blanket works well for this.

[Openwater]

I measured it. front of ramp right after firebox is 4.5" from pan and ramps up to 3" from pan before entering stack.
If I put in a firewall right after firebox that goes up to 2" from pan, would I still need to fill in the space after the "wall", or will the flames stay up against the pan bottom for the length of the pan?
I don't have much time for fabrication at this time since I plan on boiling sap this coming Sunday.

[Cjadamec]

I measured it. front of ramp right after firebox is 4.5" from pan and ramps up to 3" from pan before entering stack.
If I put in a firewall right after firebox that goes up to 2" from pan, would I still need to fill in the space after the "wall", or will the flames stay up against the pan bottom for the length of the pan?
I don't have much time for fabrication at this time since I plan on boiling sap this coming Sunday.

I would simply lay 1 course of brick under the back edge of the pan. That will bring the gap down to 2 inches or so right at the back of the pan and give you more heat there.

That's a quick and easy way to do it and should get you results right away. There is no need to alter the rest of the ramp.

[red/one]

I used vermiculite and ceramic blanket last year and it worked very well. If you build a wall to 2" or so below the pan you can fill behind it to the stack.

[Openwater]

I would try more air first.
Any opinions regarding this blower on Amazon for getting more air:
VIVOSUN 6 Inch 390 CFM Inline Duct Fan with Variable Speed Controller HVAC Blower for Ventilation

I'd have to neck down the 6" outlet to the 4" opening that goes into my AUF inlet

[Cjadamec]

That fan will work, probably a bit over sized for your size arch but axial blowers don't develop as much pressure as a squirrel cage blowers.

[Swingpure]

Good morning. I'm switching from steam pans on my homemade evaporator to a divided pan. The steam pans were 6" deep and sat down in the evaporator (scorched pan sides). Now, I've got a 14" x 48" pan with float box being made to put on my evaporator with a 12" x 48" opening. My stove pipe is 6" dia.

My questions are:
1. How much higher do I need to raise the fire grate?
2. I will also need to get more heat/flames/hot gas against the bottom of pan, so could I just put a couple baffles on ramp of arch to force up against bottom of pan, or should I just raise the entire bottom of ramp/arch closer to pan bottom?
3. If stove pipe is 6" diameter (28.25 square inches), how much space/area should there optimally be between bottom of arch and bottom of pan? More or less than exhaust pipe area?

Thanks for any advice/suggestions.
22560225612256222563

Hmmm, I am also switching from steam pans to a divided pan. I am rebuilding my cinder block evaporator so that it fits the new pan better.

I was not thinking about raising my grate, I just thought it was an opportunity to add more wood in the fire box. Instead of two rows of wood under the pan, there might three.

Also I know everything I have read on this forum says that you want 2” or less distance between the ramp and the pans, but I know of at least two professional evaporators that have 6 or 7” of space between the ramp and the bottom of pans and the head stack and pipe get literally red hot. A little befuddling.

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