Cross Flow Pans vs. Reverse flow Pans

[Thompson's Tree Farm]

OK, everybody chime in here. What are the advantages and disadvantages of cross flow pans. I have a 4x12 wood fired lightning evaporator with regular reverse flow pans. I am considering a second pan so I can switch during the season to facilitate cleaning. Would it be smarter to go to cross flow pans and buy a 3rd pan?
Thanks,
Doug

[Fred Henderson]

Well with a cross flow you will definately have to shut down to change them. Reverse flow you can change direction while boiling and change it now before boiling the next time. If you have another pan. A reverse pan will cost you more because it will be the whole pan not just half of it as would be the case with a cross flow. I am hearing that cross flow is soon going to fall by the wayside.

[hard maple]

has anyone switched from reverse flow to cross flow
and wish they hadn't??
or vice versa??

[802maple]

I personally would never own another reverse flow pan, I have owned 3 different ones and thought I liked them until I used a cross flow. I then bought a cross flow and have never looked back. It is a old wives tale that you have to shut down your fire to change them. I change them at about the time that I have to refire if I need to during the boil. Just don't open your door and the draft will suck the heat right away from where the pan used to be until you get the new one on.

[Fred Henderson]

How true 802 but a wood fire may present more of a challenge.

[802maple]

That is what I was doing it with on my intens-o-fire wood fired.

[Jim Schumacher]

Jerry, can we have a little more detail on how you change the pans out without scorching them? Also, do you still prefer cross flow pans?

What does everyone else think of cross flows? I never used them but it seems like a hassle to have to change the pan out versus switching sides...but again, I never used an evaporator set up with them.

Sorry for reviving such an old thread. I am starting to design my new evaporator and am trying to decide what pan system I am going to use.

[Mark]

I have used a cross flow for the last 11 years and decided to try reversing the pans. I added plumbing to do it on the reverse flow pans. I could go almost twice as long between pan changes. I tried to do a hundred gallons of syrup and then reverse for the next hundred. I would normally shut down after a hundred gallons so this would cut the shutdowns in half.

The problem was when doing a hundred one way I would end up warping the pans on the second hundred. I could not do it with one reverse. I had to reverse every hour to get 200 gallons of syrup through. There is always the problem with the chance of burning after the reversing and getting big draws. Drawing off thin syrup because you know thick is behind it. You just get stabilized and it is time to reverse again. I quit doing the reversing by the end of the season.

I have had the most luck with my oil fired finisher. I could let the big rig slow down a bit and change the finisher pan in ten minutes.

That is boiling 16 brix sap. Before the RO I would just change the pans at the start of the day.

[Thompson's Tree Farm]

After starting this thread, I took Jerry's advice and got cross flow pans. Would not want to go back (but the old reverse flow pan is stored for emergency use). I have not yet changed pans mid boil and am usually boiling alone so that would be difficult. I change the pan every day before I start up. I am sure that I should be doing it mid boil or more often as I make up to 200 gallons/day on a 4x12 wood fired. A change out mid boil or sooner would mean less buildup. Pans clean easily, usually with just a soak in permeate. If niter is not coming off easily, adding some vinegar for about an hour solves the problem.

[802maple]

I still prefer crossflow, I will never go back to a reverseflow.

I will go over this again, when I am ready to change pans I plug off the front pan from the back pan, disconnect connections draw off half the syrup in the pan I am going to change and put it in the the new pan. Then I quickly take the dirty pan off the arch, put the clean pan on the arch, make my connections. I put the remaining syrup from the dirty pan into the new pan pull the plugs and start boiling at full force again. It takes about 3 to 5 minutes max to do this not the 2 hours that Leader and others say that it takes. I turn off the blower and make sure i don't open the doors on the front so that the draft is pulling the heat down while I am making the change. I have done this alone on up to five foot evaporators, on a six footer I usually ask for help.

[Brian Ryther]

Has any one ever had a problem with cross flow and cold spot at the draw off? The front corners of my syrup pan are the coldest part of the pan.

[802maple]

Do you have reverse flow pans Brian? If so that is what makes a crossflow so much smoother. The reverse flows don't like going from the hotter part of the pan to the cooler part and back to the hotter part, that is why you end up with syrup toward the middle of the evaporator first with a reverse flow.

[Thad Blaisdell]

Has any one ever had a problem with cross flow and cold spot at the draw off? The front corners of my syrup pan are the coldest part of the pan.

Do you burn oil....? If so what are you using for nozzles?

[Amber Gold]

Jerry, when swapping pans on a wood fired, how does the new pan not burn when there's no liquid in it? There's going to be some time involved w/ setting the new pan, making the connections, and then filling it. Is there a window when you can put the liquid in the pan w/out burning it?

[Brian Ryther]

I burn wood.

I have a reverse flow pan. I do agree with Jerry that it can be hard to get the syrup past the cold corner at the front of the last partition. I do often end up with large slug batches of syrup when no matter what I do I am unable to even the draw off to a constant flow. In a cross flow pan doesent the syrup want to go towards the hottest part of the pan, so isn't it hard to get the syrup into the draw off box?

[Randy Brutkoski]

I am not able to get a somewhat constant pour off either. I pour off big batches every 20 to 25 min. Roughly I get 10 to 13 gallons for every pour off. And quite often i have to open the pour off valve almost all of the way because the temp spikes so fast, sometimes even with the blowers off. I have also tried running my front pans not as deep. I had to flood the pans quite a bit just to be safe. This was my first year boiling so i imagine i will know more what to expect next year.

[802maple]

Jerry, when swapping pans on a wood fired, how does the new pan not burn when there's no liquid in it? There's going to be some time involved w/ setting the new pan, making the connections, and then filling it. Is there a window when you can put the liquid in the pan w/out burning it?

I am going to pick on you here Josh, read it again. I believe I said I put half the syrup in the new pan.

[802maple]

I am not able to get a somewhat constant pour off either. I pour off big batches every 20 to 25 min. Roughly I get 10 to 13 gallons for every pour off. And quite often i have to open the pour off valve almost all of the way because the temp spikes so fast, sometimes even with the blowers off. I have also tried running my front pans not as deep. I had to flood the pans quite a bit just to be safe. This was my first year boiling so i imagine i will know more what to expect next year.

Randy most likely you are waiting to long before you start to drawoff, I always start alittle early.

Brian, I don't have the problem you stated, because it is going toward a constant heat source with consistant heat at each partition instead of the constant changes in a reverse flow.

[Brent]

From what I've heard from local dealers in Ontario ... a reverse flow rig is a hard sell in Quebec. They want cross flow almost exclusively.

I got a new to me reverse flow rig last summer with two syrup pans. I thought I was going to be in heaven. Reverse once or twice then swap the pans like 802 suggests.

When I got the rig together I stood and stared at it with my mouth open catching flies. Bloody Leader drop flue has no way to close off the flow between the flue and syrup pans. *&^%$ ! I looked everywhere for a really narrow profile valve, even a slide valve but I could not find one that I could weld in.

So I've been learning how to reverse flows. It's not easy and frequently tests your pucker point. You've got to have a 5 gallon pail of sap standing by. Next year I'm planning to make a paddle that fits the syrup pan divisions very tight. When I want to reverse I'll plug / unplug the flue pan ports, then put the paddle in the channel I was drawing from, open the opposite side to drain into a pail and slowly chase the thickest sap with the paddle until I get it into the last channel. I might even try to catch the thinner stuff and pump it directly to the old draw off side. That should get me pretty close to the correct gradient in the channels and avoild the near melt down in the middle. It wouldn't be the first time I needed a plan B or C or D but I sounds good in the middle of the off season.

[Brian Ryther]

Jerry, I can see what you are saying with a constant heat across each partition, but you are going from the back of the pan, the hottest, to the front of the pan, the coldest. I can see how it is better, but wouldn't it be even better to plumb the flue pan to the front of the crossflow syrup pans and draw off at the back, hottest, pan.. ?

[vtmaplemaker]

but wouldn't it be even better to plumb the flue pan to the front of the crossflow syrup pans and draw off at the back, hottest, pan.. ?

I have seen this done, the problem they had, was with syrup coming off the hottest part of the pan, it was very easy and very quick to burn especially later season sap.... Its kind of along the same lines of why don't we use a all flue to syrup?? As you get closer to syrup, the density rises faster, and its harder to keep in the pans...

[802maple]

I have seen this done, the problem they had, was with syrup coming off the hottest part of the pan, it was very easy and very quick to burn especially later season sap.... Its kind of along the same lines of why don't we use a all flue to syrup?? As you get closer to syrup, the density rises faster, and its harder to keep in the pans...

You have it exactly right vtmaplemaker, believe me Brian this system works well and as pointed out it doesn't burn as easily. Bryanex is right, you couldn't pay a Quebec sugarmaker or atleast a majority to use a reverse flow and now me either.

[Jim Schumacher]

Alright guys. You pretty much have me talked into cross flows.

Now tell me if you see any potential flaws in my pan configuration, as it is a bit untypical. My plan is to build a 3'x10' raised flue pan and team it with two 2'x3' cross flow pans and put them on a 3'x14' high efficiencty woodfired arch. Would the 1' wide channels in the cross flow pans be too big for their 3' length?

Thanks for all the great input!!!!

Jim

[Amber Gold]

sorry jerry, I saw where you said take half out but somehow missed where you said put half of it in the new pan.

[chrislanfear]

i would agree with 802 that you need to start your draw earlier. i have a 5x16 Tornado with cross flows and we draw off about 130 gallons an hour. i have a modulating draw-off and it is constant.

[802maple]

No problem Josh

As far as the pan configuration goes, my first Intens-O-fire that I built for myself was a 3x13, with a 10 foot raised flue. I was told that 18 inch pans were better for that size evaporator with 9 inch sections. I know I loved that rig and it was my first crossflow.