Sap depth vs boil rate

[Diesel Pro]

I have good reliable help. Best of all free help. I manage the RO concentrate and water. My help runs the evaporator. I've said numerous times that shallow boils faster. Last season we typically ran at about 1" depth in my flat pan. This year he wants to run it deep stating: Why did they make the pan so deep if they didn't want you to use it?

So my question is, how much theoretical difference is there between 1" depth and 3"+ depth?

Free help is hard to come by and I don't want to start an argument, but I also want to get done in the minimal amount of time...

[NTBugtraq]

The water you are trying to get rid of has to reach the air in order to go away. The more it has to go through, whether that's sap or foam, the longer it will take to go away. Plus, the greater the depth, the larger the volume you are trying to keep boiling, that means more fuel and longer boil times to evaporate.

Tell your friend your pans are so deep in order to prevent foam ups from going over the edge of the pan.

Cheers,
Russ

[Diesel Pro]

What would you figure a good boil rate is for a 2x3 pan?

I'd probably be starting at 9.6% maybe 12+ if that matters.

I have a 2x4 evap with dual pans. We use the small pan at the rear for semi finished and the large pan for main boil. We draw off of main pan and add to rear pan periodically. The rear pan stays filled and just gets added to. I have plans to use a stainless stock pot to draw off from the rear pan periodically then move this into my PET Carboys when cooled rather than keep it on the boil all day.

[smokeyamber]

Boil rate rule of thumb is mult dimensions of the pan so a 2x4 is good for 8gph, Depth, wood and firing times all affect this, but it is a good starting point. I figure anything above the rule of thumb is all good. ;)

Enjoy your boiling :cool:and on the pan depth issue, if you are in a hurry, I would swap places to give your friend a break, run it low and then let him run it his depth. I used to run very deep pans ( 4-6 " ) and I could then load up the firebox, go inside and have a nice lunch, then come back to a 1-2" pan, that is a more relaxed pace than some would like, but batch boiliing lends itself to such things. I will be going to a continous flow setup next season so likely things will get more hectic... :lol: Key thing is to have fun and don't take it too seriously... leave that to the BIG guys !

[Cabin]

I have good reliable help. Best of all free help. I manage the RO concentrate and water. My help runs the evaporator. I've said numerous times that shallow boils faster. Last season we typically ran at about 1" depth in my flat pan. This year he wants to run it deep stating: Why did they make the pan so deep if they didn't want you to use it?

So my question is, how much theoretical difference is there between 1" depth and 3"+ depth?

Free help is hard to come by and I don't want to start an argument, but I also want to get done in the minimal amount of time...

The evaporation rate has to do with the surface area of the pan. So depth should not matter all things being equal. It will take longer for deap cold sap to boil vs shallow cold sap but once a boil has been reached it should not matter.

[Maplewalnut]

The depth of sap absolutely matters. Surface area is one factor but the amount of energy it takes to maintain boil is another. Startup will take longer with a deeper layer of sap but also the time it takes to return to 'boiling' after you fire (ia ssume you are wood fired) also contribute to evaporation rate. Boiling is a generic term I dont perculate my sap... I want a boil as high as I can get...which is the reason pan sides are higher than expected. Its not to fill the pans higher...its to keep the shallow layer of boiling sap in them as it tries to jump out!!!!

[Cabin]

The depth of sap absolutely matters. Surface area is one factor but the amount of energy it takes to maintain boil is another. Startup will take longer with a deeper layer of sap but also the time it takes to return to 'boiling' after you fire (ia ssume you are wood fired) also contribute to evaporation rate. Boiling is a generic term I dont perculate my sap... I want a boil as high as I can get...which is the reason pan sides are higher than expected. Its not to fill the pans higher...its to keep the shallow layer of boiling sap in them as it tries to jump out!!!!

But with a deaper level of sap the pan should not lose heat as fast so would the effect of firing the arch be a factor??

I always wondered why high stack temps are 'good'? If 1000 degrees of heat is going out the stack it is not being transfered to the sap. Other than keeping the flue clean what is the benifit of high stact temps?

[ennismaple]

Tell your help the deep sides are to keep the pan from boiling over. We run our syrup pan at 2". Since we can get big runoffs where half the front pan comes off at once we want the added depth to allow the float to allow sap in from the flue pan in to keep the pan from burning.

If the level is too deep the bubbles created by boiling can get re-absorbed into the liquid.

[Diesel Pro]

We add cold sap by buckets. I've been thinking of a preheat pan of sorts. What happens is with more volume it returns to boil quicker hence the notion that it's doing better.

I'll work on the pan sides thing and I think we'll start firing harder as well. We get a decent boil, but it's not jumping out of the pan kind of boil.

Next year I 'll split my wood like hockey stick handles to 2x4 size as well for the faster hotter burn.

[DaveB]

My experience is that I get a much higher evaporation rate the shallower the sap. I usually run about 1-1.5" and have generally not had a problem. My understanding is that the high sides are to prevent splashing and allow for flooding and other factors, not that you're supposed to run it at that level.

[acerrubrum]

I think the larger issue is that with a shallow pan it's easier to scorch the sap. If that happens, and you toss the whole pan full and have to clean the pans, you save nothing over having a deeper pan that requires more energy to boil.
Just last week I ran my pan lower (from the usual 1 1/2" to around 3/4") and increased my boil rate from 9-12gph. After walking away for 10 minutes I came back and realized I scorched the pan and had to toss the batch and clean up and start over. If I hover over the pan I'll run it lower, if I can't I run it higher. It's a lot more work, and heartache to toss a pan full and clean up.
Live and learn.

[slammer3364]

I have a small flat pan (18x48) I used to boil about 1 inch. This year I put up a stainless stack, a friend of mine made the base piece on the evaporator it is made of heavier stainless changed my blower somewhat and boiled at two inch depth ,that is the best boiling rate I have ever had.

[maple flats]

My fastest boil rate is when I keep the syrup pan at about 1", I don't dare shallower. On my flues pan I keep it at 1/2-3/4" over the flues. That is always the same, regardless of concentration, I've run from 2% straight sap up to 14-15% concentrate, all the same depth.
The tall sides are to contain the extremely hard boil, rather than to have it jump out.