evaporator setup

[Beweller]

It seems that everyone feeds the sap to the evaporator at the flue end, finishing syrup at the burner end.

Why?

[SeanD]

The biggest reason is because of the differing boiling points of sap to syrup. Sap boils at around 212*F whereas syrup boils around 219*F. The hottest part of your arch is right above the fire box, so that's where you want the near-syrup which requires more heat energy in order to boil. The relatively cooler gases that travel toward the back of the evaporator still have enough heat to get the sap at the back boiling at 212*F.

That's the basic premiss behind so many people trying to improve the efficiency of their evaporators. They are trying to squeeze every possible bit of heat out of their fuel and put it into the sap before it goes up the pipe. This arrangement of the sap moving from the back to front goes a long way toward that.

Sean

[Haynes Forest Products]

Same reason you put gas in your GAS TANK and the exhaust comes out the tail pipe:rolleyes: OK Im sorry I asked this question last year. I called Maple Pro and asked Garth about this very set up and he said that they had tried the idea of shooting a oil gun up at the flues and let the rest of the heat travel past the finish pans. I think the conversation went like this......Yep yep Yut yut OK ok Yet Yet shur you bet UH HA UH HA yet yet yup you bet see ya ...............I WENT TO BED FEELING BETTER ABOUT MY SET UP

[3rdgen.maple]

Haynes you left me disapointed on that post. I was really expecting you to say, because a burnt up flue pan cost alot more money than a burnt up syrup pan. There was a youtube video of a guy bragging about his great operation a long time ago and when you watched the video he was indeed feeding sap into his syrup pan and drawing off at the stack. Might work okay as long as you are running flat pans but once you get into a flue pan things would go to crap in a hurry. I would think feeding raw sap into the hottest pan would kill the efficiency of an arch, as the cool sap would kill the boil.

[Beweller]

Obviously the pans should be reversed.

[3rdgen.maple]

I wouldnt switch the pans if its a drop flue rig. Raised flue would be okay maybe but I think you have to remember that the flames need to be suck through the flues and with the large gap under the pan that way it would leave alot of room for the heat to go under the pans and out the stack. Heck give it a shot and let us know.

[Beweller]

Evidently no one knows.

My guess is tradition from when wood was THE fuel. Think of firing at one end and drawing syrup at the other. With oil firing, less reason, but the stack might be a bit more awkward at the syrup end than is the burner.

I think there may be a slight process advantage to the reversed configuration, but after more thought, I doubt it would be sufficient to justify changing the designs.

[Ausable]

Hmmmmmm - Reading between the lines - Sounds like You are firing with oil and the hottest part of your combustion is taking place near the stack rather then up front where the firebox is normally located -- is that correct? Or do I misunderstand You. If that is what's going on - You might want to modify the oil torch - so combustion take place in the fire box area -- or - modify the arch so the superheated air makes another pass thru the arch - instead of going up the stack---- Naw---- that is getting a bit radical -- modify the torch if thats the problem-----

[3rdgen.maple]

Beweller all I can say is since all the big equipment manufacturers spend so much time and money testing and redsigning evaporators to make us the best and most efficient equipment I do believe somewhere during that process if reversing the setup was the answer it would have taken place alot of years ago. So since it didnt and nobody does it it cannot be worth while.

[Bucket Head]

I once saw an oil fired rig (in the off season) set up "backwards" like that. It was a big one. I asked about its advantages and/or drawbacks. The owner said they did it like that for years and it worked well. Thats all he said. Take that for what its worth. Apparently he was happy with it. I suppose a well insulated, forced drafted and consistantly fired arch with a high stack temp. (meaning theres enough heat to finish the syrup in the back) would work allright. However, 99% of the sugarmakers out there are content with their "fire in the front" models. I won't be turning mine around anytime soon.

Steve

[brookledge]

Back in the 70s before RO's a local producer had 2 6X18 evaporators and had one with just flue pans. That evaporator was higher in the air and fed the other 6X18.
Keith

[Sugarmaker]

Old flat pans on a Warren outfit. Sap came in the rear pan wich had warming cups, then traveled in a external pipe to the very front pan. the syrup then moved towards the back of the arch through two more pans and was finished right next to the warming pan. I made many batches of syrup on this old rig. It was a 3 x 10 with 5 2 foot wide pans that hinged up on the left side of the arch.
REMEMBER YOU CAN MAKE SYRUP ON JUST ABOUT ANYTHING YOU CAN HOLD SAP IN AND GET A FIRE UNDER:)
Regards,
Chris