Big problems...carbon deposits in the drop flues

[NTBugtraq]

Ok, so I drew my first syrup off my pan, ever, today. I took 5L and it turned out great. So I figured my gradient had been established and was looking forward to the next draw off. I was firing every 15 minutes. I was at +2F above boiling, and got interrupted so my next fire was going to be 20 minutes after my last...but low and behold, the entire pan area, drop flues, finishing pan, even the float box, was full of a dark brown foamy burnt smelling liquid. My level was still 1.5", I had defoamer in a ladle and foam wasn't that high in the pan, but it was all lost.

I immediately took what I could out of the arch fire box. I put the hose in the float box and started draining at the syrup outlet. After about 20 gals drawn off (of mostly black looking stuff) I disconnected the two pans and started draining all over...still running water into the float. While it drained I put some of the first stuff I drew off into my hydrotherm cup and dropped the hydrotherm in...it went below the surface and never re-appeared...iows, I was way below 65.8 brix (unless someone has another explanation). I didn't see the thermometer myself, but my helper said it was above +10F.

So, fire out, pans drained, I started the clean up. In the drop flues, from about 1/3rd from the back to the front of the flue pan, most of the flues were full of carbon material. I used a scraper to get some of it out, but I couldn't get it all, it was fried to the sides of the flues. I spent the next hour with a pressure washer trying to get the carbon out of the flues, not a whole lot of luck with that. Called the distributor I bought the pans from, he said to use oven cleaner. Bought that, put it on...lolz, he obviously never cleaned a drop flue pan with oven cleaner. The spray wants to spread out, but I want it to get to the bottom of the flue...yeah, like that's going to happen. Anyway, put an entire can of oven spray on the worst parts of the pan. Cleaner says leave it 2 hours...I'm leaving it there overnight.

Q1: How could this happen? 20 minutes and it goes from looking cool to total crap...I gotta believe that carbon was building up over time, but since I was establishing a gradient I wasn't about to go swishing around a chamber...how could I have known this was going on?

Q2: Float was working, level was what it was supposed to be (1.5"), so how could the entire surface of both pans get so outta whack? Black syrup was flowing back into the float pan for crying out loud...and I'd drawn off 5L 2.5hrs ealier...

I'm really unhappy right now because I can't figure out what went wrong. The last thing I want to do is fill em up and do it again, draw 5L, and then have 20+gals go to waste 2.5hrs later.

Any and all insights will be listened to. Today's draw-off was my first ever...and I did feel like it was kinda taking longer than it should, but it worked out fine...it wasn't till later. And should you wonder, the float did a great job keeping up with the draw-off.

Plan is tomorrow to put in lots of water and some calcium cleaner from the dealer and let that come to a boil, then drain, rinse, boil water again, drain, rinse, and then refill with sap to restart the gradient.

Cheers,
Russ

[CampHamp]

Sorry to hear your story. Frustrating stuff.

If you're pretty certain there was no boil over, then your intake must have stopped somehow and then started back up before you got back. A stuck float could do that or a block in your intake (ice in your head tank or frozen line).

I don't like the idea of using Easy-Off on the inside your pan. You definitely do not want any residue from that stuff in your syrup.

[Pibster]

Drawing off 5 litres at a time seems like a bit much but I can't see that causing the burnt flue pan. I usually draw a 1/2 litre at a time.

[NTBugtraq]

...then your intake must have stopped somehow and then started back up before you got back. A stuck float could do that or a block in your intake (ice in your head tank or frozen line).

There was no ice at the time, when it happened, I had already been boiling for 5 hours that morning. And, I was boiling at 1.5", so it couldn't have evaporated that much in 20 minutes.


I don't like the idea of using Easy-Off on the inside your pan. You definitely do not want any residue from that stuff in your syrup.

Me either, but its done now. I sprayed off as much as I could after letting it sit overnight. I then filled it with fresh water, brought it to a boil, added 4L of pan cleaner, and then stopped firing. I'm about to draw that off now, re-spray and see what that water tastes like.


Drawing off 5 litres at a time seems like a bit much but I can't see that causing the burnt flue pan. I usually draw a 1/2 litre at a time.

My pan + flues hold 40L. Drawing off 5L would drop the level in my pans by 1/4", leaving them at 1-1/4"...not enough to cause a problem.

Cheers,
Russ

[ihuntbear]

happened to me last year..was not happy...the dealer told me to soak it in vinegar and water over night.more vinegar then water.i think I used three gallon of vinegar to one gallon of water.it worked..just had to do a good clean up after

[PerryW]

as far as I know, there are only two ways for that to happen:

1) the level was too low

2) you went beyond syrup in the front pan.

the +10 deg f that your helper read in the dial would indicate that the front pan was beyond syrup, but hard to believe that would happnen if you just took off 5 liters.

[red maples]

5 L is still a big draw off of in a very short time. boiling hard combined with drawing off with even a little bit of foam could back up the floats. foam confuses floats and makes them think there is more in there than there really is. mean while the level is going down without new sap coming in. I would ditch the ladle or what ever your using and just add it by hand. just make sure you add enough defoamer on a regular basis. Make sure your line from the head tank is big enough and watch your back pan better. I don't know much about that evap. but I have run a little low in my back pan before and you need to lean on the float a little especially when the head tank gets low because there is a pressure difference between a full head tank and 1/2 full head tank.

[Spanielslovesappin]

did you take off 5 lt then boil another 2.5 hours before this happened? and what size is your evap?

[Big_Eddy]

If I read this correctly, you took your first draw of about 5 litres in the morning, then 2 1/2 hours later you had the problem.

I know that you were boiling a long time before that first draw as you sweetened the pans, but once that first syrup was take off, then you would be producing syrup at 2-3 litres per hour and I would have expected at one or two more draws in that time.

If it was 2.5 hours after the first draw and you had been running at a reasonably steady state all along, then your front syrup pans would have been getting very concentrated. Your helper saying the thermometer was showing +10F indicates the same thing. As the syrup gets more concentrated, it foams up, and will backflow into the flue pan raising the level there are well and telling the float "no thanks, we have plenty". Continue for another 20 minutes and the whole evaporator is getting so concentrated that there is no water left to boil off.

Hope you get it cleaned up as good as new. Be glad you caught it before the sugar caught fire!

My float box has a trickle noise that I am used to hearing. If that sound stops, I investigate. Could be ice in the lines, no sap in the tank, jammed float or anything. Regardless - no sap coming in requires IMMEDIATE attention.

[NTBugtraq]

So, to try and cover all the questions.

1. I drew 5L, and continued to boil for 2.5hrs before I had the problem. At every fire, I check the level in the pans and check for foaming. For that 2.5hrs, the levels maintained 1.5", and there was no significant foaming (until I met the destruction.)

2. I agree, the level must have been the issue. The thermo on the syrup pan was reading only +2F 20 minutes before the disaster. There was no significant foam anywhere at that time, so I believed that reading. Even when I met the disaster, the foaming wasn't deep, I could see sap in many places and foam around the edges appeared only to be maybe .5".

3. I discovered today that the float was not properly attached to the valve arm, that may very well be what caused the problem, I dunno, but I have put the float onto the arm correctly now.

4. The first thing I did upon seeing the disaster was draw-off into my finishing pan. I drew significantly more than 5L at that time, while taking as much of the logs as I could out of the firebox. After things were under control, I measured the brix of the stuff in the finishing pan, it was way below 65.8...so I didn't overcook as far as I can tell.

5. I have never seen foam to the level of the ladle yet, nor even remnants of foam on the side walls that high (I have seen evidence of sap maybe 3" above sap level, which I put down to the roiling boil). And I do keep an eye on the foam, every time I fire (every 15 mins)...

6. The boil is definitely most at where the float pan empties into the flue pan, and where the flue pan empties into the front pan...the dealer said this is expected and desired.

7. I drew 5L because that's how much came off the pan before the thermo in the front channel of the finishing pan changed from +7.5F to +7F...how else should I figure out how much to draw off?

8. Eddy, I too was expecting to see syrup long before that 2.5hr mark...but alas, the thermo didn't get back up to +7.5F??

9. If I can't rely on the thermo, and things can go from great to crap in 20 mins, does that mean the only way to evap is to live in the sugar shack? Not to put too fine a point on it, but I gotta split wood, check taps, check sumps, etc...

I left the Easy Off in the pan overnight. FWIW, its a stupid idea because you can't spray oven cleaner into the flues...the cleaner spray wants to go wide, and you want it to go deep into the flue...we just couldn't agree to do the same thing. Anyway, pressure-washed it off this morning...a lot of carbon came off but a lot still remained. Put the pan on the evap and filled it to 1.5" with water...got that to boiling (front and flue pans) and then added 4L of pan cleaner. Left that till it had cooled to 150F. Pressure washed again. Still a lot of carbon in the flues. Used a cedar shingle as a scrubbing tool and got a lot of carbon out...pressure washing all long. Put the pans back on the evap and filled to 1.5" with sap and started a new boil. Once it was boiling, have been playing whack-a-mole...paper thin strips of carbon pop up outta the flues and give me a chance to catch them with the screen...or...they fall back down into another flue...to arise a minute later...lolz.

Most important point is the sap tastes like water, not cleaner, and vapour has no smell, and the colour is clear (atm)...so I'm convinced I have not left residual cleaner, and the carbon is not going to affect my syrup flavor (since it will be caught in filters). It was a 24 hour ordeal, but we move on.

Unluckily/luckily...no sap flow yesterday...and so far none today...

Thanks all!

Cheers,
Russ

[Big_Eddy]

If there is fire in the arch then I'm in the sugar house. I step outside for a moment or two at the most. If I do have to walk away I only do it after a draw and I manually add 5 gals extra sap. I will let it tick over while I have lunch or dinner with one or two large pieces of wood but never a hot fire. I might be overly cautious but its worked so far.

[maple flats]

Still 5 LTR seems like a big draw. Is that pan a 2x6? At 130 taps that is my guess. Even on my 3x8 I rarely draw that much as a single draw. In fact maybe I do, far more. Since I was running a 2x6 I've tried to run slow continuous draws, and I tweak the valve open or closed a little as needed to hold at the correct temperature. I have at times been able to draw non stop almost an hour. This helps because when you do batch draws you get a degree of surging in the pans, which mixes the gradient.

[Spanielslovesappin]

More or less the whole of the evaporator was over syrup, it can happen quickly. It foamed up and tricked the float or the float hung up and it burned.

I do not leave the evaporator un-attended and helpers don't count. When i was a young helper i was involved in the total destruction of a set of pans.

Continuous flow or regular small batch flow on a 2 x 6 takes lots of attention, constant stoking and quite a bit of messing around. Just because the draw thermometer is at + 2 does not mean the the center of the syrup pan is not at +7, especially if it has been boiling with no movement for 2.5 hours. 5lt is a huge draw in such a small evaporator, it would likely destroy any gradient that had been established. frequently i would have to pull off some light and dump it back in on the other side of the syrup pan even after boiling for 6 hours and making lots of syrup just because i had taken to much out and then trapped syrup in the middle. There is no such thing as set it and forget it.

This whole situation sucks and i am glad your quick action saved your pans. I just want to convey the idea that gradient is not easy to maintain and sometimes the best you can do is take off small batches every 15-30 min say 1-4 hydrometer cups worth. i encourage you to stick with your evaporator like glue next time you boil and really get to know it, its kind of awesome when you finally get a unit dialed in.

[NW Ohio]

I am using a Smoky Lake 2x4 Hybrid, so I am not sure how different it would be from what you are using, but here are my thoughts. I would never leave the pan unattended (not even a minute... ...I know it may not be possible for everyone, but it could save you lots of work). I also understand the science behind the thermometer reading but I don't rely on it. I watch the syrup for the "right look", take the temp. reading into account, and as the final call on when to draw off I check it with the hydrometer, if it's light it can go back in the pan, no harm done. I would have been really nervous in that 2.5 hour timeframe with no draw and would likely have drawn a test cup multiple times for my piece of mind.
I wonder if you may have had a pan full of syrup that had no place to go so the sugar in it burned. New sap coming in washed past the burned stuff but did not pick up any sugar since it had turned to carbon and was stuck in your flues. This might explain the low brix reading that you got after things settled down.
Also, I would be sure to taste the syrup from the batch that followed. You might not taste any of the cleaner in the sap but it could be pretty dilute still. If you were still picking out carbon it could have still had cleaner in it (not sure how it works but I envision it penetrating into the burnt material and potentially being driven out as you started the boil). I don't know if you would drive those chemicals off by boiling or concentrate them along with the sugar. Just a thought.

[PerryW]

So, to try and cover all the questions.

4. The first thing I did upon seeing the disaster was draw-off into my finishing pan. I drew significantly more than 5L at that time, while taking as much of the logs as I could out of the firebox. After things were under control, I measured the brix of the stuff in the finishing pan, it was way below 65.8...so I didn't overcook as far as I can tell.



Trying to help, but didn't understand your comment above. Normally a "draw-off" refers to drawing syrup from the evaporator. It sounds like you are using the term draw-off differetly. Is your finishing pan a separate rig to do the final finishing?

Also, when you had the burned syrup, a lot of syrup was consumed in the burning process (turned to carbon), so I would expect your drawn off syrup to be less than 65.8 brix.

If it turned to syrup (and burned) in the flue pan, it would point to a problem where the cold sap was bypassing the flue pan and going straight into the syrup pan (flat pan) instead of travelling the longer route through the flue pan.

A couple other random comments:

An evaproator can be a strange beast, I have taken off a big draw and then looked at the it 5 minutes later and seen it back up over 7! SO you really have to expect anything. I do leave my rig boiling so I can run up to the house (for 5 minutes), but only after a big draw-off and after adding defoamer.

The part that mystifys me is that the problem happened in the back pan (flue pan right?) Usually over cooking syrup problems burn the front pan(syrup pan). But I'm not sure how your rig is set up. SOunds like the float issue may be the problem.

[NTBugtraq]

Still 5 LTR seems like a big draw. Is that pan a 2x6? At 130 taps that is my guess. Even on my 3x8 I rarely draw that much as a single draw. In fact maybe I do, far more. Since I was running a 2x6 I've tried to run slow continuous draws, and I tweak the valve open or closed a little as needed to hold at the correct temperature. I have at times been able to draw non stop almost an hour. This helps because when you do batch draws you get a degree of surging in the pans, which mixes the gradient.

My evap is 18" x 5', and 5L represents 1/4" height in the pans. I drew off slowly (save 1/2 valve opened), thinking the float kept up (I didn't measure after draw, my mistake, but I heard the new sap going into the pan). I asked about continuous draw and was told that wasn't really possible??


More or less the whole of the evaporator was over syrup, it can happen quickly. It foamed up and tricked the float or the float hung up and it burned.

I agree, this sounds like the most likely cause.


I just want to convey the idea that gradient is not easy to maintain and sometimes the best you can do is take off small batches every 15-30 min say 1-4 hydrometer cups worth.

If I take these small more frequent draws, what are you doing to keep it hot to bottle it?


I also understand the science behind the thermometer reading but I don't rely on it. I watch the syrup for the "right look", take the temp. reading into account, and as the final call on when to draw off I check it with the hydrometer, if it's light it can go back in the pan, no harm done. I would have been really nervous in that 2.5 hour timeframe with no draw and would likely have drawn a test cup multiple times for my piece of mind.
I wonder if you may have had a pan full of syrup that had no place to go so the sugar in it burned. New sap coming in washed past the burned stuff but did not pick up any sugar since it had turned to carbon and was stuck in your flues. This might explain the low brix reading that you got after things settled down.

Let's say I am taking samples from various places in the pans and discover there's no syrup at the draw-off point, but, there is syrup in the chamber before it, or in the flue pan, how do I get that out? And once its out, how do I deal with whatever the problem is causing that to happen?


Also, I would be sure to taste the syrup from the batch that followed. You might not taste any of the cleaner in the sap but it could be pretty dilute still. If you were still picking out carbon it could have still had cleaner in it (not sure how it works but I envision it penetrating into the burnt material and potentially being driven out as you started the boil). I don't know if you would drive those chemicals off by boiling or concentrate them along with the sugar. Just a thought.

Lolz, thanks for the re-assuring speculation...so you're basically saying it may happen at any time in the future and my product may have to be thrown away...nice. Carbon works as a filter, but I've never heard of it being used to absorb anything...its pretty hard and dense stuff.

Cheers,
Russ

[NTBugtraq]

Trying to help, but didn't understand your comment above. Normally a "draw-off" refers to drawing syrup from the evaporator. It sounds like you are using the term draw-off differetly. Is your finishing pan a separate rig to do the final finishing?

My evap has an 18" x 18" front 2 channel syrup pan with a draw-off tap, and a 18" x 42" back 2 channel 10 flue pan. I also have a 16" x 16" finishing pan that goes on a 60,000BTU propane burner. So what I meant was I used the draw-off tap on my front pan to take the burnt stuff out into my 16" x 16" finishing pan.


Also, when you had the burned syrup, a lot of syrup was consumed in the burning process (turned to carbon), so I would expect your drawn off syrup to be less than 65.8 brix.

That makes sense, hadn't considered that.


The part that mystifys me is that the problem happened in the back pan (flue pan right?) Usually over cooking syrup problems burn the front pan(syrup pan). But I'm not sure how your rig is set up. SOunds like the float issue may be the problem.

That's consistent with what others said, and given I discovered the float in the float box was connected incorrectly; I do believe it was the cause. Despite correcting that float issue, I plan on tending my arch a lot closer from now on.

Cheers,
Russ

[NTBugtraq]

Ok, just got off the phone with CDL, the manufacturer of my arch. They confirmed that the use of Easy Off was the right thing to do to get rid of the carbon, and that by using pan acid/cleaner after the Easy Off it will have gotten rid of any residual soap...phew. They agree that I should close the damper to try and get the fire going up to the syrup pan sooner, and that moving the C channel to the front should help also. They also told me how to deal with syrup being made in the flue pan...put some sap from my omg 5gal pail directly in where it appears the syrup is being made to dilute it. That's easy enough to do and makes sense. The trick will be to try and put that in slowly to avoid doing too much damage to the gradient.

Finally, I discovered that my flue pan bottom (i.e. the top of the flues) is actually .5" higher than the syrup pan. By running 1.5" in the flue pan, as I have been, I'm leaving 2" in the syrup pan. That, they say, is too much, so I will be aiming for 1" in the flue pan now. That will obviously require more attention to the whole setup.

I feel I have a better understanding of what happened and how to prevent it, here's hoping I can apply all I've learnt...;-] Expecting a great sap day today, so hopefully I will get an opportunity to put all this to good use.

Cheers,
Russ

[red maples]

well that explains a lot.

When boiling try to have zero foam in your flue pans. you have to keep up on it if you got 2 or 3 inches of foam your in not defoaming enough.

my front pan is never more than 1.5 inches I don't messure by the back just by the front pan other wise it takes too long for the front pan to catch up to the back pan and your back pan density will be too high and your syrup will be darker as well. you will also get big batch draws and its better to try to get slow long even draws rather than batch. Like some else said you will get more mixing that way and make darker syrup again getting a too dense gradient in your back pan.

make sure your wood is closer to the door. to keep your syrup pans boiling harder.

weather your on natural air flow or a blower if you run into trouble open the doors a cool draft will run under the pans cool things off quickly so you can catch up.

That being said Beware with a drop flue as there are no floats to the front pan so the level of your front is 100% dependent on the temperament of the boil of your flue pan it can be tricky. So everytime you open the doors make it quick. Your boil will slow and can suck the syrup out of your front pan while at the same time there should be more fresh sap coming into your float box. then once the level comes back up from boil in the back pan getting stronger then your front pan will be diluted. It takes practice to get things right. you'll get it sorry about the mishap... Good luck

[Hal]

Quoting from your earlier post . " If I can't rely on the thermo, and things can go from great to crap in 20 mins, does that mean the only way to evap is to live in the sugar shack? Not to put too fine a point on it, but I gotta split wood, check taps, check sumps, etc..."

YES!!! You never turn your back on the beast while it is operating. Quick trip outside to check vacuum or tank levels, water the trees, no more than half minute, and then only if you are sure things are stable.

No chairs or couches in the sugarhouse, no TV, computer, or reading material. Phone only as absolutely necessary, extra caution if you have visitors, back off on the fire while you eat lunch, get the picture?

It only takes a few seconds for everything to turn to crap, I have been boiling for over fifty years, and it can still take me by surprise.

[red maples]

Well said. but I do have a chair!!! but its set up right next to thermometer and it doesn't get used very often.

[mellondome]

Just a thought... is this a reversable flow flue pan? If so it sounds like you might not have been drawing from the flue to syrup pan on the proper side.

[NTBugtraq]

Just a thought... is this a reversable flow flue pan? If so it sounds like you might not have been drawing from the flue to syrup pan on the proper side.

No, the pan isn't reversible, at least I don't think it is. It has a float box welded to one side with an opening cut between it and the flue pan, and on the other side a clampable outlet pipe. I have wondered, out loud, as to whether it would make more sense to have the syrup pan at the stack rather than the front of the arch...???

Anyway, now that I have closed the damper (only open 1 notch now, instead of 5 notches), lowered the level of sap, and put slightly less wood in the firebox, I'm getting an even boil across both pans front to back. I stared at my sap boiling all day yesterday...I'm disappointed I have yet to; see the image of Jesus in the foam, find a map of Atlantis in the niter deposits, heard If you build it they will come in the hissing of the steam...;-]

Cheers,
Russ