Sap level fluctuation when flue pan starts boiling hard

[Biz]

When my flue pan starts boiling hard, the mound of sap bubbles in the flue pan blocks sap from flowing in since that is where the sap entry point is. Float turns sap off and the level in flue pans drops to like 1/4". The float box entry point to the flue pan is right where the sap boils the hardest. When fire dies down after 6-8 minutes, sap comes pouring in and level tries to return to the 1.5 - 1.75" that it is set to. However at this point I am ready to fire it again. Is this normal? I am worried about burning the syrup or pans. Perhaps there is a better way to fire it or set it up so that the flue pan boils strong in the middle of the flues instead of the very beginning of the flues near the sap entry point. Rig is Smokey Lake 2x5 Hybrid Pro but I assume this could be a problem with any rig set up this way. I use a mix of hard/soft wood, no blower.

Dave

[motowbrowne]

I've only seen a couple of jobs Jim's pans, but IIRC, they're a drop flue design right? I was thinking that 1.5" is pretty deep for a flue pan, but if that's also the level in the syrup pan, I suppose you can't go much less than that.

The first thing I'd try would be firing more often. You mention the fire dying down. When I was first running my 2x10 I did the same thing. Load the box full of wood, let it run for 10-12 minutes until it started slowing down, load the box full, repeat. I was getting about 30 GPH. After talking to another member here I used some tips I learned from him. Only open one door at a time and get it open, loaded, and shut in the minimum possible amount of time. Also, add only a few pieces at a time, but add wood every 3-4 minutes. The goal is to eliminate the fluctuations of heat from various stages of the fire. Instead you have a much more constant heat source. Typically I have to adjust my float as I get rolling. Once I'm up to temp and really cooking I have to increase the flow coming into the sap pan. Then when I start up again in the morning I'll reduce the flow because otherwise it'll want to run really deep and take forever to get going.

Beyond that, perhaps a baffle could be added to shield the float from the geysers. My 2x10 had something like that. Just a little cover that fit over the pipe that went into the float. Obviously not water tight.

[Woodsrover]

I run a 2x5 Smoky Lake / Badgerland arch and pan set and mine will do the same thing if I'm not paying attention. I check the flue pan quite often and add de-foamer as needed. When the bubbles calm down it starts feeding sap normally again.

[maple flats]

Add 1 drop of defoamer at each fueling and fuel using a timer. Maybe start at 7 minutes and experiment with 6 and 8 to see which performs best.
If you wait until the fire slows down you are causing this issue. The fire should never slow down until you are shutting down.

[Biz]

I can try that and see how it works. I am worried that if I do NOT wait for fire to die down, I will never get enough sap into the pan, since sap only seems to flow when it is not boiling hard. Just the opposite of what I want. It does not foam up very much, it is the fountain of bubbles that blocks sap flow. Consistently drops level down very low when boiling hard.

Dave

[TRAILGUY]

I have the same problem if I am not study with deformer.

[mellondome]

The boil will not block sap flow. Allowing the sap level to constantly rise and drop will cause issues with consistant draw offs. If you let the boil die on any evaporator it will draw in sap like mad. Bigger the pan the more it will flow in. Sap level in a flue pan only needs to keep the flues wet during a boil. It is the front pan level that you should adjust your float for (drop style flue). If you want 1" in your syrup pan, then adjust your float while in a normal boil to maintain that 1" in the front pan. ( not the sap pan)

[Biz]

Thanks mellondome, that is good to know. The level is just enough to keep the flues wet, it is just scary because it seems like I am very close to having no sap and burning the pan, since there is no sap flowing in. I am going to end up with a 1" or more difference in height between syrup pan and flue pan while it is boiling hard, does that sound reasonable? I may have to tweak the height to set the levels better during a boil.

Dave

[VTnewguy]

Dave, I would try consistent use of defoamer. Every time you fire the arch. Pump is working awesome-Josh

[Ghs57]

I run a Smokey Lake 2x6 hybrid, but can't say I have that problem. I don't use defamer in the flue pan only because I've not had to. After three seasons with this pan, I think I have the float level setting down.

As mentioned above, consistently firing makes a world of difference. I've got AUF/AOF/Preheater, and 6.5 minutes works for me. I can run an efficient level in the flue section that keeps the syrup section safe, even considering the pan evap rate. It may take some adjusting, but generally, when everything is up to temperature, I can dial it in and leave it alone.

Of course, there are so many variable from rig to rig, that your results may vary.