Expand an Evaporator, or build a second one? (Also design consid. for huge pans, etc)

[wisnoskij]

Hello all,

First I want to lead off with a big thank you to everyone on this forum, it has been an unequaled resource for me.

Where I am now.
I have a 6 steam pan evaporator. I still have to work on extending the exhaust system, adding a preheating system, attaching the insulation better, and siphons would save me a lot of work. But it works amazing, the hardest part in using it is to trying to keep the pans from boiling over.
The sides angle in somewhat to protect the sides of the pans, between the pans is covered with T posts. And the Exhaust box is a 8"-20" 3 foot pyramid.
Evaporator.png

The one issue I had with it is it takes longer to get to full bore than I would of expected. I think it had to be like 3-4 hours before it was at peak performance, for example, I think it was about 3 hours before the back pan was the hottest pan. An extended exhaust should help somewhat, but I had it facing into the wind on both boiling days to help with any exhaust pull weakness.


But my biggest question right now is expanding it. I have the opportunity to get a old milking tank cheap. This would quite naturally become a 3'-6' pan, with at least a few dividers to make one of those Z flow pans (the ones where the sap flows to the front on the right, back to the back down the middle, then up to the front again on the left).

This brings up two main design questions.
1. I have never seen a setup with a pan that was not really movable. You take the pan off the fire to finish of the batch, but this pan might be a little big for that. At the very least I would need to do quite a bit of welding and design work to make a place to pull it off to. Do the real professionals have systems setup to cool pans where they lay? or are they always designed to be taken off the fire part of the evaporator?


2. How far apart to put support walls? I really want the underside of the pan to be flat to encourage a good flow of exhaust, but I can do support/compartment walls on the inside. But the question is, is 2 walls longways plenty of support? Do I want to add some short ways walls, or just even more longways walls? Just common sense I am thinking it might make sense to do something like (diagram below).
Pan.jpg

Or are thinner pans just way better? Will the firebox and exhaust be just so wide as to be unwieldy and hard to build?
When Leader says 3x8 or 3x10 arch, do they mean 3' by 8 or 10' arch? I just watched one video of one of their arches and it looked like the pan stayed on the arch, and I am pretty sure I saw wood ash, but no word on how they cooled off the pan.

The compartment walls should only need to be like 3-4 inches tall, so I should have enough extra SS.
But maybe that will lead to a bunch of areas where the sap does not flow forwards and just stays still? So maybe I would actually want thinner compartments, like four 9" ones, or five 7.xx" ones?

I have seen very long evaporators. But, my experience with this 6' one is that I think they must take a LONG time to come fully up to temp. What is your experience with this? I am just trying to think of what would be the most efficient and easy to use setup. Running two evaporators is probably not ideal, but how best to combine them?

1. Again, is such a big setup only good if you are evaporating 24/7 and don't have to worry so much about warm-up time?
2. Can I change widths so dramatically in a single evaporator?

OK, I had the craziest design idea. Since I not only need to expand the draw area, but also am worried about it being slow to heat up; What about a double firebox evaporator? Where I basically just stick this finished evaporator on the front of a second evaporator. The 8" draw of the first one feeds into the second firebox, which adds in additional air, heat, and fire, to become a 12" draw, exiting out a 12" stack*?

* If I am reading this Leader manual right, then a 12" stack should be just about right for about the equivalent of 3'x9.x' of pan space.

Misc question. This should probably be its own post, but should I be doing anything fancy with air intake(s). I just assumed I wanted an intake about equal to my exhaust under my fire at the front??? But maybe I want a little intake half way down my evaporator to induce some reburn, but I imagine it does not get hot enough with all the boiling water?

[Sugarmaker]

Well,
You have been thinking about this milk tank evaporator a lot. I will not try to discourage you from trying it. I have told folks for years that if you can put sap in it and fire under it you can make syrup. It is about as simple as that. Remember that syrup was made in antique cast steel kettles in the woods!
Before you get too far I would suggest that you visit several sugarhouses making syrup on small to medium evaporators. This will help you determine some of the design basics.
Yes large evaporators are listed as 3 x 10 that's 3 feet wide x 10 foot long pans. (mine is a old 3 x 10 King)



So on your partitions in the bottom of a milk tank, it will be a challenge unless your a real good welder. I would recommend that they be continuous welded along all seams to avoid leak from one channel to the next. On that size area you might need three partitions. And they would need to be at least 8 inches high to avoid boil over into the adjoining partitions. The tanks are thicker than normal pans but with enough fire it would eventually make syrup. My guess is you might have a lot of time into that tank pan and might be happier with a custom built syrup pan?

Commercial pans set on a arch and are not removed to take off syrup. The syrup is drawn off at one corner of the pan set up.

Not sure I have helped you here?
I had a neighbor that had a fire under a milk tank and sap in the tank. Not sure if he made any syrup? But he was doing it!
Regards.
Chris

[wisnoskij]

Thanks a lot Sugarmaker. That info really helps
So do you just remove the coals and leave enough sap in the pans to avoid them turning into sugar over night? Or turn the entire thing into syrup/close enough and let it cool off and it all off?
And why would the sides need to be at least 8 inches, A lot of pan sides are 6" high, that is all I am working with now. And the internal walls are of course less important. Excessive boiling was solved by the addition of a tiny amount of oil in my case, are you saying you can allow the pans to go and stay in super boil mode if you have +8" walls?

Does that 3x10 have a 10' long pan? Not exactly sure why all the professional setups have the giant thing on the back half?
And great suggestion for checking out how others are doing it. I know someone I was planning to ask about a tour after sap season is over.

[Sugarmaker]

Thanks a lot Sugarmaker. That info really helps
So do you just remove the coals and leave enough sap in the pans to avoid them turning into sugar over night? Or turn the entire thing into syrup/close enough and let it cool off and it all off?
And why would the sides need to be at least 8 inches, A lot of pan sides are 6" high, that is all I am working with now. And the internal walls are of course less important. Excessive boiling was solved by the addition of a tiny amount of oil in my case, are you saying you can allow the pans to go and stay in super boil mode if you have +8" walls?

Does that 3x10 have a 10' long pan? Not exactly sure why all the professional setups have the giant thing on the back half?
And great suggestion for checking out how others are doing it. I know someone I was planning to ask about a tour after sap season is over.

I dont "pull the fire" But I do know some folks that do. I just time it so that there is enough sap to allow the fire to go out and still have 2 inches in the pan the next morning. I my case that may mean having 25-30 gallons of sap remaining and I stop firing. ( I am still firing with wood).
If you get a really good boil going it can easily boil over 6 inch sides or partitions. I assume for oil you mean defoamer? And no the internal walls are just as important in height, to keep from boiling over at any area of the pan. This keeps the gradiant going as your sap pushes the syrup towards the draw off port. Any boil over or leaks between partitions will basically keep the gradiant from forming and you will have a mixed batch of syrup through out a major portion of your pan. Making it much harder to have syrup at just the draw off.

Pans should boil as hard as you can unless you really just want to simmer sap. Most of us try to boil as hard, as hot, and as fast as we can. As a friend says "your only 15 seconds for disaster" when running one of these oid rigs!

My antique arch and pans have two pans each 5 foot long. Most rigs today have a longer flue pan and a shorter front syrup pan.

The giant 22 inch high stainless unit is a steam away that I built. It takes 2% sap and removes enough water to make it into 3% sap when it enters the back pan, Also heats the sap to near 200 deg F. The rest of the stainless are hoods to remove the steam.

All kinds of variations and sizes of evaporators!
Regards,
Chris