Forced draft steam hood stack

[bmbmkr]

I made a steam hood for my 2x6 two years ago. The hood sits on the flue pan and is raised up about a foot over the syrup pan. Boiling is so MUCH better with the hood, but I'd guess only 70% of the steam is being evacuated. I'm getting quite a bit of steam out from under the front part of the hood above the syrup pan. My stack is a little far back on the hood, 24" O.C. from the smoke stack. I had to choose which set of rafters to go through. I made the 10' long, 8 1/2 dia stack out of a sheet of 28 ga SS.

I saw a video of the CDL Venturi evaporator, which uses air input to the smoke stack to improve draft. Last week I was in the sugar camp, and I thought Hey what about adding an air input to the steam stack?

If I fabbed up an angled duct to attach to the steam stack just above the hood, use a small blower, or tee off of the AUF/AOF air input and blow air up the steam stack would it improve the steam draft? Before I go cuttin holes in the stack and reconfiguring the AOF/AUF plumbing, what are your thoughts? Should I use a blower the same size as the steam output, bigger, or smaller, or just put another ball valve in the air input I already have in place and adjust it from time to time on the fly. I'd really like to improve the draft of the hood without adding another stack, roof jack, etc... Any thoughts/inputs appreciated.

Walk

[bmbmkr]

I posted this a few months ago when there isn't much traffic on the trader. Now that it's gettin closer to season maybe I'll get some hits.

Showed my idea to my cousin last week who worked damage control in the Navy, he said it works that way with fluid, said they used the ship turbine exhaust to pump water in a similar fashion. He thought it would work with air and steam. The one other sugar maker I asked suggested adding another stack- he also sells stack. Anyways, I'm thinking of tee'ing off my AOF/AUF air (650 cfm) and blasting some steam out of the hood.

Anyone have any thoughts or suggestions?

Walk

[bill m]

I am trying to get a picture of your hood in my head. Is it open from the front pan to the back pan and only the back part sits down on the flue pan on 3 sides? If so then I think that is the problem. The front part of your hood over the syrup pan needs its own stack. I don't think adding forced draft will help much in this case.

[maple flats]

I agree with bill m. Either you can add a separate steam stack or join the 2 higher up. If you choose #2, make sure the stack is large enough to handle both. On my x8 I had 2 stacks each was 13" diameter, it worked well. My flue pan and hood was 3x5, while my syrup pan and elevated hood were 3x3. On the outside of the hood it was all one piece, but the steam from the syrup pan did not mix with the flue pan steam.

[bmbmkr]

22655

Bill, 4 gutters sit on the top of the flue pan, the front of the one piece hood hangs over the syrup pan. Not so much forcing a draft up as in Air under fire, but sucking the draft by forcing air up the stack, which should draw more air from the larger stack opening below it, which is exactly how CDL creates draft with their venturi evaporator, they are blowing outside air up the smoke stack.


22656

Again, just my theory for my steam problem. I've read where people used fans & insulated their steam stack to increase the draft. Kinda like wrapping the straight pipes on the old Harley shovel heads. Adding another stack is definitely the best option, I don't have enough sheet left to make another one, and don't have the budget to buy one this year. Honestly, I don't want to have to cut another hole in the old shed roof I'm boiling under. But I'd like it to work, as I plan on selling this rig in a year or two when I upgrade and double taps again. I do have enough sheet left to make a 2 1/2" venturi tube, to connect to my AUF/AOF plumbing which comes in behind the arch. I can take no for an answer, I appreciate your all's insights.

[bill m]

I think the problem is the design of your hood. There should not be an opening in the hood between the front pan and the back pan. The back pan creates so much more steam than the front pan that the pressure it creates keeps the steam in the front pan from being drawn out.

[bmbmkr]

Bill, you are right about the "pressure" or volume of steam over the flue pan. As far as the design over the syrup pan, there are many manufacturers building hoods this way for both small and large evaporators, of course, however, they are using larger diameter stacks, or more than one stack. I get that, I know my stack is too small, and I probably should have moved it closer to the front of the hood as well, but it's built, and I'm out of time and materials to build another one. I have $180- in this hood. I traded for the 26 ga SS sheet the hood is made of, the 22 ga the gutters are made of and the 28 ga the stack and inside drip pans are made of. My cousin let me use his 8' brake, and my wife is a millwright/certified welder...I couldn't ask for anything but a better blueprint to begin with.

My question is though, has anyone "induced steam draft with a venturi set up like CDL uses in their new evaporator? I'm goin to try it this coming week. I found a way to try it out without cutting anything yet. I appreciate your insight. I'll post my experiment when my permeate tanks thaw out & I can do a test boil.

[DMF]

Here's a crazy idea: Why not put a section of pipe in your current steam stack with a built-in duct fan?

Something like this: https://www.supplyhouse.com/DiversiTech-625-AF8-8-Dia-Duct-Fan-420-CFM-37W?gclid=CjwKCAiA8OmdBhAgEiwAShr407G3m0Az9Eb9wAiy V8leeaiOTNVnVfvSwYYaEFPjreuX4vx4RnvA8hoCyOwQAvD_Bw E

Maybe you could utilize some sort of dimmer switch to vary the speed of the fan if needed...? Seems way easier than trying to duct some of the air from your fire blower...

[bmbmkr]

Here's a crazy idea: Why not put a section of pipe in your current steam stack with a built-in duct fan?

Something like this: https://www.supplyhouse.com/DiversiTech-625-AF8-8-Dia-Duct-Fan-420-CFM-37W?gclid=CjwKCAiA8OmdBhAgEiwAShr407G3m0Az9Eb9wAiy V8leeaiOTNVnVfvSwYYaEFPjreuX4vx4RnvA8hoCyOwQAvD_Bw E

Maybe you could utilize some sort of dimmer switch to vary the speed of the fan if needed...? Seems way easier than trying to duct some of the air from your fire blower...

DMF, I'm not sure if the electric motor would stand up to the heat/moisture from evacuating steam. There were several threads on here years ago about folks using these in small sugar shacks with small evaporators to evacuate steam through the wall in the peak of the gable to get steam out and they had moxed results. Good idea though. I appreciate your input.

[DMF]

DMF, I'm not sure if the electric motor would stand up to the heat/moisture from evacuating steam. There were several threads on here years ago about folks using these in small sugar shacks with small evaporators to evacuate steam through the wall in the peak of the gable to get steam out and they had moxed results. Good idea though. I appreciate your input.

Well they make fans for your bathrooms for evacuating steam. Granted, a shower doesn't produce as mush steam as an evaporator (unless you have a daughter like mine) but my point is that there should be an option out there.

As this is in the homemade equipment forum, I would assume that you're handy with fabricating. Maybe move the motor outside of the duct, add pulleys to the fan and motor and drive it with a little timing belt. Similar to this:
https://www.amazon.com/Befenybay-Synchronous-Aluminum-Timing-20-60T-8B-6/dp/B07ZC2K9ZY/ref=asc_df_B07ZC2K9ZY/?tag=hyprod-20&linkCode=df0&hvadid=385577181574&hvpos=&hvnetw=g&hvrand=11781524308214842186&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001683&hvtargid=pla-1041868456472&psc=1&tag=&ref=&adgrpid=77367395023&hvpone=&hvptwo=&hvadid=385577181574&hvpos=&hvnetw=g&hvrand=11781524308214842186&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001683&hvtargid=pla-1041868456472 (https://www.amazon.com/Befenybay-Synchronous-Aluminum-Timing-20-60T-8B-6/dp/B07ZC2K9ZY/ref=asc_df_B07ZC2K9ZY/?tag=hyprod-
20&linkCode=df0&hvadid=385577181574&hvpos=&hvnetw=g&hvrand=11781524308214842186&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001683&hvtargid=pla-1041868456472&psc=1&tag=&ref=&adgrpid=77367395023&hvpone=&hvptwo=&hvadid=385577181574&hvpos=&hvnetw=g&hvrand=11781524308214842186&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001683&hvtargid=pla-1041868456472)
Of course, you'd need a slot to allow the belt to penetrate the duct which would create a small opening for steam to escape out the side, but I think if you were running the fan, very little would escape.

It's just my $0.02, but I personally wouldn't want to pull CFM away from my fire to evacuate steam; I'd rather have a separate means of doing that. Also, it just seams WAY easier to have two separate systems (O2 to fire and evacuation of steam) vs. doing all the plumbing to combine the two.

[craigwade2005]

I'm not an engineer by any means, but I think that your thought process has merit.

Lots of items use this theory to move water - gold dredges, fire strainers etc.

There are also a pile of air driven things used in machining that use pressure to convert to volume.

I say try it, experiment and if it does work weld a cover over the stack. I think a small jet of high pressure may work better than a large volume of low pressure.

[mainebackswoodssyrup]

We have a fan in our stack to help get rid of the steam. We took the motor off the side of the fan, spliced in 3' of wire and mounted it on the wall 3' away to get it out of the steam/heat. Has worked good for 4 seasons now. Our hood is not tight fitting and we were not generating the draft we needed to get rid of the steam so we tried the fan and it works well.

[evanbeelen]

To me, this seems like this idea should work. I am an engineer in an automotive manufacturing plant, and we use this exact same mechanism of air flow in several of our sand blasting applications. We blow compressed air at an angle past an inlet port that is connected to a blast media feeding tube to deliver the blasting media. Your proposed design is basically just replacing the blast media with the steam coming from your pans. The advantage you have is that the steam already wants to go up the stack, and all you are trying to do is help it along. As others have pointed out, it may be beneficial to use a designated blower for the stack rather than taking away air from the fire box (unless you are already metering down your airflow into your firebox).

I am curious to hear what your results are, as I am looking into building a shack this summer and am considering my options for steam evacuation.

[BAP]

It would be cheaper and better to modify the hood you have for a second steam pipe than to screw around with fans and pay for electricity over time. Fans are just a bandaid solution.

[snakes14009]

So currently I run a 2x4 in a 12x12 shed and my original idea was to exhaust my steam out the smoke stack to help lower my exhaust temps and cool embers. Plus it would only have one hole through the roof. Any way I didn't have the ceiling height to make it work so i was going to add a 45 connector in the steam stack to add a fan and create suction for the steam. Yes it will work but your fan CFM has to be high to create enough negative pressure to pull the steam up through. So i went with an inline fan from amazon for about 40 bucks and it helped and worked in the steam all season long till the last boil. I am going to try a different fan this year. So give it a try let us know how it turns out.