Steam Stack Height

[danno]

I've read the prior threads and don't see a concensus. Some like them high to improve draft/draw - with the idea that "water under vacuum boils at as lower temp". While others like them short to reduce the condensate build up in the stack and with less draw, keeping higher heat in the hood to increase pre heater temps.

What do you'all think?

Do you have your preheater pan under your steam stack to catch the condensate running down the inside of the stack?

While my smoke stack is over 20', my steam stack is probably closer to 5', but easy enough to raise.

[OGDENS SUGAR BUSH]

my steam stack is center of my pre heater condensate pan. stack is 8 ft high and dumps out at the cupalo

RICH

[Brent]

This is going to be interesting, Next week I cut the roof for 1 smoke and two steams.

I'm also interested to know if you think a damper is needed on the steam to regulate the flow. I'm going to have a preheater set over the flue pan.

[OGDENS SUGAR BUSH]

No Damper And I Dont Think It Is Needed? Interesting To Here About This

Rich

[brookledge]

My steam stack is just 6 feet high and dumps up in my cupalo. I don't have a hood over my syrup pan. I like it that way because it is simple to lift the hood off for cleaning and I don't have to touch the stack. Whereas if it went up through the roof it would be more difficult to take the pipe down to raise the hood.
I also have a damper. The first year I didn't have a damper and the temp coming into the evaporator was in the high 100s then with the damper I keep itt at about 200-205. If I close the damper too much the whole hood rattles and sounds like it's going to explode.
I think the issue of higher hood pressure to heat the sap more vs. lower pressure to boil at a lower temp is a good subject for one of the research centers to look at or better yet a good physics experiment.
Keith

[sapman]

I,too, wonder if higher temps are really more beneficial. While closing the damper gives you higher temps, if the steam isn't escaping are you getting the evaporation?

I know with my Steamaway (which may be a different principle), running the sap deeper gives me higher temps, but it isn't bubbling as much, hence very little actual evaporation. But the bubbling is obviously artificial from the air injection, so perhaps my reasoning is off base for your situation.

Tim

[tapper]

My steam stack is 6' high empties into the cupola and is centered over the condensate pan. It has a damper. Closing it just slightly makes 200 degree sap at the preheater and makes the hood leak. Completley open and sap at the preheater averages 160 degrees with no hood leakage. Makes me think there is a trade off there. Hotter sap entering the fluepan versus more evaporation by leaving the damper completley open.

[Dave Y]

I don't think steam stack heigth means a thing aslong as you are getting you steam off you pans. Mine is 5' high and I have a damper on my back pan and I can get the sap to boil in the preheater. I personally dont think there is any trade off to using a damper as you should see the prehater pan pissing out condesate when the temps are that high. yes you are making more condesation at those temps. But, you are also discharging it.

[tapper]

Yes for the tiny amount of trade offs there are betewwn damper open or damper closed or the height of the stack the long and short of it all boils down to simply getting the steam up and outta my face.

[maple flats]

I have 2 steam stacks and they dump in the cupola. I designed mine to be able to raise the hood with the stacks going up too. I have enough clearance to raise the hood about 2 ft. The stack are a 10" on top suspended from the cupola and a 12" at the hood, the upper just rides inside the lower. It worked ok but I might try to go 2 @ 10" all of the way and just have it 2' shorter, to see if I like that better, it would still be up to the bottom of the cupola and I would have a loose guide to stabilize it. My current steam stacks are 10' high

[WESTVIRGINIAMAPLER]

Anyone got any expert opinion, maybe Jerry(802maple) can chip in on this one. I would be curious to know which was is the fastest evap rate, I usually run my stack damper 1/2 closed.

[danno]

I've got the hood raising issue figured out nicely. My 10" steam stack goes through the roof through a 12" roof flashing, so there is just a little bit of play. I've got 4 eye bolts, one in each corner of the hood. Hood is cabled through pulleys that lead to a winch. If I want to raise the hood, just winch it up and the steam stack slides right up through the roof.

Still deciding whether to increase height of steam stack. I don't think my preheater leads are long enough to move the condensate pan under the stack without connecting the the preheater to incoming sap line under the hood. I much prefer to make this connection outside the hood.

[Brent]

When my evap gets here I'm going to see how well it draws. One thing I am considering is to wrap the stainless with the mylar-silvered bubble wrap. If the pipe temp stays high it will draw better and have less condensation.

This however may necessitate a damper because if the stack is insulated it may draw too fast for the preheater.

[Brent]

going back to your first post you mention "water under vacuum" and boiling temp.

I you would be hard pressed to measure an air pressure difference in the hood with a short stack, tall stack, damper open or damper closed.
I think you can forget that consideration.

[Russell Lampron]

Brent when your hood fits tight on your pan it is sealed off good enough so that the draft from the steam stack will create a slight vacuum which will in turn lower the temp that sap will boil at. By adding a damper to the stack and closing it it will build a slight pressure inside of the hood that will make it take a little more heat to maintain a boil.

If you don't have a preheater you don't need a damper. If you do have a preheater you can get hotter sap by closing the damper some. It only makes about a 5 degree difference in mine. I usually leave the damper open so that I don't get a face full of steam when I open the door to check the boil in the flue pan and add defoamer.

Russ

[Brent]

I hear what you're saying about raising or lowering the pressure and it's real physics. I just don't think that with an open stack and the velocity that air and air pressure equalize that you would ever measure a difference in the boil rate.

By co-incidence I was talking with Patrick Phaneuf about dampers in my steam stack and he said he has a design the puts out 190 - 200 degree sap without needing a damper. And then adds that we can add one later if we think we need it.