View Full Version : Help! I'm Fighting the Evaporator
NE Cornfed
04-04-2011, 09:07 PM
Hi Everybody,
My name is Scott and I found this site while trying to do a little research on my recently finished season. I lurked around a couple of threads and was hoping someone, anyone, could help me out.
Here's my situation. I've recently taken over the operations in a new sugarhouse (the girlfriend's family) that has been shutdown for the last 2 or 3 seasons due to a lack of knowledge and more importantly, labor. I'm not new to sugaring, but I am new to having to run the whole show. When I was younger, sugaring was more about collecting sap, stoking the arch and keeping an eye on pan and tank levels, not really "running" the evaporator.
We've got a 10-12yr old, Leader 3x10 that we're firing with wood. Being new to this sugarhouse, evaporator, setup etc; it took me a couple boils to figure out some of the nuances of the equipment. There were several things I noticed that were affecting evaporator efficiency (dirty flues, some missing or misplaced fire bricks, gasket leaks, etc).
However, one thing I haven't figured out, is during long boiling sessions I seem to have to "fight" the evaporator to get and keep good temps in my syrup pan. This happens more after drawing off than any other time. It isn't uncommon to lose 3-5 degrees after a draw. I've tried opening the drawoff valve all the way and also just cracking it open to let little more than a trickle of syrup out during a draw. I keep the valve open until the digital thermometer drops a degree, then close it and test my last cup full to see if I still have syrup or not. This past Saturday, we boiled for about 16 hrs, only made about 19 gallons, and on 3 separate occasions the temp stuck at 212-214 for 30 mins plus (we were drawing off a little over 217). While at other times, we would lose a degree or 2 and be drawing of every 10 minutes or so. I can't come up with any good reason for this. I run anywhere from 1"-1 1/4" deep in the syrup pan and my level doesn't get below 3/4" at any time. It's almost as if I'm just not getting the "push" from the colder stuff that I need.
Sorry for the long winded post, but can anyone shed some light on this? It's probably something simple, perhaps even the operator, I'm just stumped. Any help anyone could offer would be much appreciated.
erhino10
04-04-2011, 09:18 PM
I think you are drawing off to much at one time and allowing a slug of sap into your syrup pans from the flue pan. I have a auto draw off ant it draws on the tenths of a degree and just 2 or 3 tenths makes a big difference in efficency i cant imaging going an entire degree. Sometimes with the auto draw just a squirt out of the valve will result in a 1/2 degree temp. drop.
bobbyjake
04-04-2011, 09:35 PM
Scott,
It sounds like you have a number of things going on. Can you answer some questions?
What are your pans, size and configuration? A 3x10 usually has a 7' or a 6' back pan.
Do you know what your evaporation rate was? It should have been around 80 gph for a bare evap, maybe 100 with a preheater...
Do you know what your stack temperature was when things were really rolling?
Were the doors cherry hot or always just cast iron black?
What did the smoke look like? Was there ever fire actually coming out of the stack?
Generally, the big draws versus little draws only amounts to a few percent in terms of overall efficiency and throughput. What makes me wonder is your comment about 16 hours making 19 gallons. Do you know what your sugar content was that day (assuming that wasn't the first boil of the season either!!) cause if you were doing 80 gph, then your sap was less than 1%, but if your sap was 2%, you were only getting about 51gph through the rig.
danno
04-04-2011, 09:37 PM
There are other threads on this topic that you can search as well. Once you have the big temp drop, I bet that next draw an hour later is little hairy, huh?
I have a 3x10 that I have fought with as well trying to get regular draws. Like the previous poster, my new auto drawoff has helped tremendously. My first draw or two are still sometimes tricky, but after that the syrup comes off sooo smoothly with the temp never going more than a degree higher or lower than syrup. It makes working the evaporator so much more enjoyable and less stressful. With the autodraw, you really see the little things that you do that cause drawoff issues. Firing, inconsistent draws, defoamer use, sap level, etc.
Is the evap level from front to back and from side to side? Just one thing that I notice that people post on this site.
Sugarmaker
04-04-2011, 09:47 PM
Scott,
We have had all these similar problems during production this year. And have seen similar things in previous years. Just seems to be the way our rig runs. We have two 5 foot pans on a 10 foot arch. One thing I did find after the season ended and I cleaned the front pan was that the partition between the center compartments was leaking underneath from one to the other. This is mixing the sap and slowing probably lengthening the time between draws.
Sounds like your early work in making syrup prepared you rather well to run this sugar house!
Regards,
Chris
NE Cornfed
04-04-2011, 10:45 PM
Scott,
It sounds like you have a number of things going on. Can you answer some questions?
What are your pans, size and configuration? A 3x10 usually has a 7' or a 6' back pan.
Do you know what your evaporation rate was? It should have been around 80 gph for a bare evap, maybe 100 with a preheater...
Do you know what your stack temperature was when things were really rolling?
Were the doors cherry hot or always just cast iron black?
What did the smoke look like? Was there ever fire actually coming out of the stack?
Generally, the big draws versus little draws only amounts to a few percent in terms of overall efficiency and throughput. What makes me wonder is your comment about 16 hours making 19 gallons. Do you know what your sugar content was that day (assuming that wasn't the first boil of the season either!!) cause if you were doing 80 gph, then your sap was less than 1%, but if your sap was 2%, you were only getting about 51gph through the rig.
1. Its a 6' drop flue pan.
2. The evaporation rate has been in the crapper all year. I havent calculated my gph though because there's been some discrepency on the size of the storage tanks. It is a bare evaporator. One thing that suprised me about the flue pan the first time I saw it, there is only one partition in it. Is that common?
3. Dont have a stack thermometer, need one in a bad way. A broad estimate would be 1000-1200 when things were really rolling.
4. The doors were glowing for 85-90% of the day.
5. When things were going well, the smoke had the slightest hint of gray/black to it. When things slowed down, it was puking black, like a diesel that needs an injector. No fire out the stack.
6. Our sugar content was around 1.6-1.7 that day.
I'm guessing this is more of an operational thing more than anything else. The auto draw-off is coming in the off season, I can't wait. The limited number of times I've done it, I never had to manually draw off syrup until now!
NE Cornfed
04-04-2011, 10:50 PM
Is the evap level from front to back and from side to side? Just one thing that I notice that people post on this site.
It may have been a hair unlevel from side to side, once the arch got really saturated with heat, it expanded because of a crack in the arch front above the doors, I didn't put a level to it but the thought that it may be out of level crossed my mind. At that point though, it was too little too late.
NE Cornfed
04-04-2011, 10:55 PM
Danno- The net draws usually aren't too hairy- just big, but I definitely keep a MUCH tighter eye on the thermometer.
PerryW
04-04-2011, 11:49 PM
Hi Everybody,
It isn't uncommon to lose 3-5 degrees after a draw. I've tried opening the drawoff valve all the way and also just cracking it open to let little more than a trickle of syrup out during a draw. I keep the valve open until the digital thermometer drops a degree, then close it and test my last cup full to see if I still have syrup or not. This past Saturday, we boiled for about 16 hrs, only made about 19 gallons, and on 3 separate occasions the temp stuck at 212-214 for 30 mins plus (we were drawing off a little over 217). While at other times, we would lose a degree or 2 and be drawing of every 10 minutes or so. I can't come up with any good reason for this. I run anywhere from 1"-1 1/4" deep in the syrup pan and my level doesn't get below 3/4" at any time. It's almost as if I'm just not getting the "push" from the colder stuff that I need.
I run a 3x10 raised flue and your situation sounds normal to me, except your syrup production seems a little low (only 19 gallons in 16 hours). My take-off vary widely, sometimes after take-off, it only drops to 6 and then I take off again five minutes later. Sometimes the temp drops to zero and I wait an hour for the next take off. Personally, I just concentrate on making steam and just let the evaporator do it's own thing.
It also sounds like you run your front pan shallower than I do. I generally run 1-1/2 to 2 inches deep. Deeper depths make for bigger take-off's spaced further apart.
NE Cornfed
04-05-2011, 07:34 AM
I really appreciate all the help/suggestions. My GPH and overall syrup production is just plain aggravating.
If any of you guys with a similar setup are still boiling, let me know. If possible, I would like to see how someone with a few more years under their belt is running their setup. I know we had about a week left in our season as of Saturday, but between work and that maddening boil on Saturday, we decided to call it a season. I don't mind traveling, if you dont mind me looking over your shoulder and firing some questions at you. Let me know!
Thanks again everybody!
PerryW
04-05-2011, 08:10 AM
Your firewood may also be contributing the the slow evaporation rate. My 3x10 will do 90-100 GPH, but only with very dry wood, split small. I split it about half the size that you would for a small-medium size woodstove.
gmcooper
04-05-2011, 08:14 AM
NE Cornfed,
I have a King 3x10 with 6' drop flue. I do not have an auto draw. Some days I do run blower but never used it all year. Most of the time I ave 70-75 gph. If I really work I can get about 80 gph out of it. My wood is not great mostly softwood slabs. If I can keep the fire very constant I get much more uniform draws. If I let fire drop too much(which doesn't take long) or if I keep arch door open too long I will get into long spans between big draws. I run usually 3/4" in the pans. Some days I will drop down to 1/2" if I know I'll be the only one there> I really like to boil alone, I can concentrate on what I'm doing and I know I do a better job that way. Also if the fire goes up and down it will cause the float to react and you will get surges of sap coming in followed by stretches where none enters till levels get back to normal. From my experiance sap with low sugar content seems to be more of a challenge to keep consistant draws with. I never use a thermometer to draw syrup off. I watch the pan and bubbles and check with my hydrometer.
Sounds like you doing ok for first year!
We should have more than a week left in our season if you want to travel north.
Mark
NE Cornfed
04-05-2011, 03:03 PM
I really appreciate it Mark. I'm actually going to be in Portland on the 16th, I know its late but, I'll send you a PM sometime next week and see if you're still boiling. That would probably be the only way I'll make it that far north in the next couple of weeks.
NE Cornfed
04-05-2011, 03:06 PM
Your firewood may also be contributing the the slow evaporation rate. My 3x10 will do 90-100 GPH, but only with very dry wood, split small. I split it about half the size that you would for a small-medium size woodstove.
I know for sure that the wood had a little something to do with it, we ended up putting some wood in the evaporator that was much damper than I like, but you have to burn what ya got.
Do you guys run your blower all the time or wait until you're burning lower quality wood to use run it?
michiganfarmer2
04-05-2011, 03:44 PM
I came home one day and dad was mad as hell. He had been boiling 8 hours and had only made 5 gallons of syrup. I got to looking. The bubbles in the center of the syrup pan were golden, and the bubbles in the outside channels were lighter color. I checked the plug from the flu pan into the syrup pan near the draw off. It was loose, and letting sap in.
Once we plugged it, and got the gradient straightened out we took 15 gallons of syrup off in a little over an hour,lol
I dont know how he diidnt burn the pan
Brent
04-05-2011, 04:50 PM
From what I see on our rig, and your lack of a stack thermometer, I think firing is your biggest issue.
I can boil for an eternity at 1000 degrees on the stack and then get a big draw, but if I get it to 1200 the draws come off smaller and more regular. I think at the lower temp there is a lot of mixing between the channels and it tends to make syrup in 2 channels instead of just the last.
Get the kind that have a probe that goes through a hole in the smokestack. Faster response and gives you the same reference most of the guys here will refer to.
so is it really important to know your stack temp? I have seen some that have them and some that dont
Brent
04-05-2011, 04:57 PM
The stack temp tool is great to help you get to know the rig. Now as soon as I see my temp drop to 1000, I re-fire it. I used to let the temp drop to near 800 before re-firing and the difference is like running two totally different rigs.
Once you see the way it runs, you can learn to read the bubbles and boil in the syrup pan. You can get there without it ... maybe by the end of next year.
It's one of the best $20 buys for the sugarhouse you can make.
gmcooper
04-05-2011, 05:44 PM
I've never used a stack temp probe and the few I have seen with them spent most of the time worring what the stack temp was and how much heat they were losing instead of making syrup. I would imagine ideal stack temps would vary from one unit to another?
NE Cornfed if your in the area stop in even if we're done for the season.
Mark
GramaCindy
04-05-2011, 06:12 PM
so is it really important to know your stack temp? I have seen some that have them and some that dont
I found my best boil came with a stack temp off of the back of the evaporator on the horizontal pipe at 600*, below that and I had to load it up and then the boil slowed down. Keeping it close to the 600* mark was best. I also have a damper that we were able to keep at a 45* angle when fired properly. Seemed to slightly slow down the burn.
danno
04-05-2011, 06:20 PM
I agree with Brent on the stack temp. I don't use it to see how hot I can get the stack, I use it to judge if it's time to re-fire. I have a magnetic thermo on the stack and I don't know if it's broken, but when the evap is screaming, the outside stack temp is only 450 degrees. Again, I'm not looking for hot temps back there, but I know if it drops below 400, I need to be firing.
Sometimes in a long, smooth draw I won't re-fire so as to keep the draw going. As soon as the draw ends or is winding down, even before I put the fresh drawn syrup through the filter, I re-fire. If the fire went too low, I won't load it all the way up -that will just cool you further. I just add a few pieces of wood, and then add a few more a couple of minutes later.
NE Cornfed
04-05-2011, 08:56 PM
I've never used a stack temp probe and the few I have seen with them spent most of the time worring what the stack temp was and how much heat they were losing instead of making syrup. I would imagine ideal stack temps would vary from one unit to another?
NE Cornfed if your in the area stop in even if we're done for the season.
Mark
Will do. I'll be in touch.
PerryW
04-06-2011, 12:07 AM
I know for sure that the wood had a little something to do with it, we ended up putting some wood in the evaporator that was much damper than I like, but you have to burn what ya got.
Do you guys run your blower all the time or wait until you're burning lower quality wood to use run it?
I'm betting the slow boil rate is wood related. As far as blowers go, I have the opposite problem. My pine slabs and edgings are so small and dry that I actually close up the damper almost completely or too much heat goes up the stack. I could probably get a better evaporation rate by opening it up a little, but I'm in wood conservation mode.
maple flats
04-06-2011, 05:56 AM
Your wood should be about wrist sized and add by the clock. In my 3x8 I have tried lots of different times. Before I added high pressure air over fire the time was 7 minutes. Now with it the time is 12 minutes. Add the wood as fast as you can and get the doors closed again.
I find trying a constant draw best for me. I have achieved draws as long as 2 hrs , but more common is up to an hour. I draw slightly thick and thin in the canner after filtering. I find it faster this way.
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