boiling on a drop flue

[Outdoorsman0490]

I was able to collect about 75 gallons of sap over the weekend and wanted to do a test boil with my new drop flue hybrid pan and block arch. When I had everything warmed up, there was a ton of steam coming off, when I turned the blower on, I couldn't believe how much steam was coming off the pan. I started the fire around 1:30, and had the 75 gal in the head tank empty by 5:30. One thing I did notice, was that the front of the pan, the syrup pans were roiling boil pretty good the whole time, as was the very front of the flue pan; I had thought that the entire flue pan would be roiling boil. I have attached a few images if the firebox and where the flues are in the arch, as well as the steam from inside and outside the sugar house.

From videos I have seen online, the entire flue pan should be rolling like crazy, which is why the pan sides are so high, right? In order to make mine do that, should I make the ramp more of a ramp and taper it closer to the flues; right now it is appox 1" below the flues the whole way back (fire box 22" long, rest of ramp is about 40"). Also, should there be almost no space between the top of the ramp and the bottom of the flues, 1 " is too much? Thanks86588659866086618662

Also, initially, I was getting used to the float box and the pan had somewhere between 1 1/2' and 2' of sap in it; is that just too much? would everything have been ok if there was just 1" in it. Would it make this much of a difference because I don't have a preheater as of yet, and was just running cold sap from the tank into the float box?

[lpakiz]

Outdoorsman,
Have you considered a stack temperature gauge? You can get into a digital one for $30 or so. I have one on the stack and one under the first 2 feet of the flue pan. The flue pan readout is roughly 1000 degrees hotter than the stack. So if the stack usually is at 800 degrees, the flue pan gauge is at 1800. Between the two, they'd will tell you how much heat you are generating, and how much is being absorbed by the flue pan, and how much is going out the stack. Also tells you exactly when to you are out of wood....

[Outdoorsman0490]

No, I never thought of that; will look into that.

Let's say my temp difference is like yours, then what would you think is going on.
Let's say the temps do not vary as much as yours, what would be recommendations to make it better

[BreezyHill]

This is not uncommon for a system without a preheater. Next time you have a pot of boiling water on the stove do a little playing.
Things to do: Place a cover on the pot...this is your hood. Now open the lid and see how the boil is. It should reduce as your are cooling the top of the water.

When the pot is boiling put in a small amount of cold tap water. The boil will at least reduce intensity if not stop. Remember that sap is usually 10-15 degrees colder than tap water.

Now try boiling the pot with only 3/4" of water. It will boil pretty quickly.

You must also remember that your pans are clean underneath. Make sure you brush your flues to keep them clean.

Remember that the more mass you have the more BTUs it takes to keep the boil going. I know people that run only 1/2" over the flues. I am not so bold and a 3/4" there are times when you can see the top of the flues nearly exposed. So I will stay with 3/4".

That is a respectable plum you have out of the sugar house! Great Job!!

Ben

[Mark-NH]

Sounds to me like your flames are rising up under your syrup pan and not traveling the entire distance under your flue pan

[Outdoorsman0490]

Thanks, maybe the pan was just too deep and I will have to try to keep it to an inch or slightly less.
I did make a small slit between a couple of my blocks about halfway down the flue pan, with the blower on, looking from the side, the flames were shooting past it.

[Flat Lander Sugaring]

your pretty deep for no preheater, steam hood, I ran my 2x6 for 11 years at 3/4" but had to watch carefully had little draws. Now with my Tsunami gasification arch I run at 1-1/2 to 1-3/4 deep and the whole thing is just a boiling monster. I had a stack therm once! I wrapped the needle all the way around and came back up to 200 hundred, they definitely help on loading times along with a timer set to 5 minutes before they are over heated.

[nymapleguy607]

How much stack are you using? It sounds like you might need another section of stack to help pull your heat toward the back of the arch.

[Outdoorsman0490]

Since the arch is 5' long, I have the stove pipe 10'

[nymapleguy607]

Are you using 6" or 8" ? I have a 2x6 with 8" stack, I have 20ft of stack on mine, most of the new arches used 10" stack and recomend 2x the length of the arch, if you calculate the volume of a 10" stack at 12 ft it is slightly larger than an 8" stack at 20ft. I only bring that up because sometimes we get too caught up on the 2x the length of the pan. If you have another piece of pipe throw it on and give it a try, I know it makes a difference if I run with a shoter pipe.

[BreezyHill]

Please do add the length of stack on. I really want to see if this has any affect at all. The reason I say this is the 2x was developed in the days of natural draft. Since you have a fan on the fire the natural draft is...well blown away. You now have forced draft fire; BUT I am still wondering if it will have a positive affect or if the added friction of the extra length of pipe will just increase the back pressure like in a trucks exhausted after a turbo charger is used. The longer the pipe the more back pressure.

Ben

[Outdoorsman0490]

It is 8" stack, I can put on another 2', should be able to pick some up in the next few days.

[Sugarmaker]

I was able to collect about 75 gallons of sap over the weekend and wanted to do a test boil with my new drop flue hybrid pan and block arch. When I had everything warmed up, there was a ton of steam coming off, when I turned the blower on, I couldn't believe how much steam was coming off the pan. I started the fire around 1:30, and had the 75 gal in the head tank empty by 5:30. One thing I did notice, was that the front of the pan, the syrup pans were roiling boil pretty good the whole time, as was the very front of the flue pan; I had thought that the entire flue pan would be roiling boil. I have attached a few images if the firebox and where the flues are in the arch, as well as the steam from inside and outside the sugar house.

From videos I have seen online, the entire flue pan should be rolling like crazy, which is why the pan sides are so high, right? In order to make mine do that, should I make the ramp more of a ramp and taper it closer to the flues; right now it is appox 1" below the flues the whole way back (fire box 22" long, rest of ramp is about 40"). Also, should there be almost no space between the top of the ramp and the bottom of the flues, 1 " is too much? Thanks86588659866086618662

Also, initially, I was getting used to the float box and the pan had somewhere between 1 1/2' and 2' of sap in it; is that just too much? would everything have been ok if there was just 1" in it. Would it make this much of a difference because I don't have a preheater as of yet, and was just running cold sap from the tank into the float box?


Hi,
After looking at your pictures and your description I believe your running about as fast as this will boil. Your doing a good job! Get some sap and make some great syrup. I think your level is Ok for now. Boiling shallow is always tricky leave that for another day in the future.
Regards,
Chris

[Outdoorsman0490]

I am pulling the pan off today. I have about 6 gal of sweet in the pan, so I figure I did somewhere between 65 to 70 gal in a little over 3 hrs once the pan was hot.

I am going to tweak the ramp design, put more insulation on the sides of the arch, probably try another 2' of stack, keep the pan level set at an inch tops with the float box, and keep more wood loaded in it all the time. And am going to make a copper manifold preheater with a home made hood over the week..

The amount of steam coming off the pan is crazy, but from watching videos on the comp,of other people boiling, I want my whole flue pan to be rolling, and would have to think the evap rate will increase once the boil is more vigorous in the back half of the flue pan.

[Outdoorsman0490]

So I reworked the fire box, which is the first 20" or so, then 20" of ramp up to the flues, then about 20" of flat tot he back of the pan. I also bumped up the stack height to 14' and put a piece of metal in the arch right in front of the exhaust to partially interrupt the flow going into the stack. Also, I made a copper preheater, parallel flow manifold style, 40' of 3/4 pipe, and a home made hood. I have the sap coming out way too hot to touch. All of this has not made the evaporation rate increase. I cleaned the pan and flues today before firing and from start up to finish it took about 8 hours to do 110 gal. I am kind of at a loss; I should be getting 25-30 gph from the pan, not 15 or so. I have 8" stack, is that too big for my set up, is 6" better?

[Outdoorsman0490]

O, and it boils pretty hard on the whole pan now; there is way too much steam to be able to really see in the pan, but it sounds like it is boiling pretty hard over they whole pan.

[lafite]

looks like you are doing the right things. adjusting your fire box and insulation will help. Any other Smokey Lake users have any input?

[Pibster]

Any chance your steam hood and preheater are leaking back into your pan? That happened to me so I had to make a new drip tray. Nothing worse than boiling sap twice.

[Outdoorsman0490]

No, everything drips out. The drip tray under the preheater is tilted towards the back into drip edge and goes into a bucket at a steady stream. The hood itself, all the condensate drips out as well, I am go into to collect that into a bucket next time to see how much water actually comes out.

[Pibster]

It's been a few years since I used a block arch. Maybe the estimated GPH is based on a regular steel arch.

[RiverSap]

Just an observation. I did not see a door at the bacfk of your block arch. I use a block arch with a divider pan and get pretty even boils. I have gaps in the lowest level of blocks for the air intake and have a steel door covering the back of the arch. My stack is six feet tall 8" pipe. Keep on boiling.