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My new evaporator


After loosing most of my help and as I got older, I’ve cut down on maple production. At my largest I had 1320 taps plus I bought sap from others totaling about another 1000 taps. I’ll now have at least 200 taps and my maximum will be about 425 taps. I’ve now sold my wood fired 3×8 evaporator and I just picked up my new 2×6 evaporator. The new evaporator will be oil fired and it should evaporate faster than wood fired per square foot of surface area. The new evaporator has a 2×4 raised flue pan. Raised flues are each 8″ tall and are spaced 5/8″ apart. Raised flue pans are considerably higher efficiency than drop flue pans. Once the boiling concentrate flows from the flue pan it goes into the syrup pan. The flue pan has 2 major channels filled with several flues, as the concentrate flowes into the syrup pan there are 4 chanels. The flow is serpentine, it goes one way to the end of the channel, then crosses over to the next channel and so forth until it reaches the draw off box at the end of chanel 4. There it will be controlled by an auto draw off.

An auto draw runs by temperature, which is adjustable. I set it according to the boiling point of water, which changes as the air pressure goes up or down. I have a device that helps me set the draw temperature, then I use a Murphy Cup and a Hydrometer to verify, and I make minor adjustments to get the density of the syruo at very slightly over density. The Murphy Cup tells me what the hydrometer should read at the exact temperature the syrup in the test cup is at that moment. I then read the hydrometer to verify it reads what it should. It takes longer to explain that it takes to do it, but it’s a very importand step. Before the invention of the MUrphy Cup I used an Accu Cup, which told me the temperature of the test sample, then I had to look at a chart to determin what the hydrometer should read t that temperature. The issue there was that the chart was not degree by degree, but jumped in steps which meant I had to guesstimate what the reading should be if the temperature was somewhere in between two readings on the chart, that left room for error because the change in density readings was not even across the temperature range between any two temperatures on the chart. The Murphy Cup chnged all of that, the scale on it is actually a temperature but it reads in density rather than degrees, no more calculating density, fast and easy.

I go to slightly over density because as I’m bottling syrup it’s much faster to add a little distilled water to thin the syrup than it is to evaporate off more to thicken the syrup. In the end, I bottle syrup at 66.9% sugar, pure, all natural with nothing added (except a slight amount of pure distilled water in most cases)

Then the syrup is graded and put into jugs or bottles. Graded means the amount of light passing thru the specific test vial is measured and that % of light transmission is what determins what the grade is. 100%-75% is Golden, delicate taste, 74.9%-50% is Amber, rich taste, 49,9-25% is dark, bold taste and anything under 25% is very dark, strong taste. For syrup to be labeled any of these grades the syrup must also be tasted, it must have a taste in line with the grade and must have no after taste. If it fails any of those it instantly becomes commercial grade and can not be sold retail. Commercial buyers can work with it, maybe sell it for coating cereals, or nuts, maybe cook it to make sugar. Super heating to get sugar often gets rid of off after tastes. At any rate, If I ever get commercial grade syrup it will get sold bulk. Fortuantely I’ve never gotten commercial grade, but it’s possible I suppose.

I have now just set the new evaporator in the sugarhouse. Over the next few months it will be made ready to boil. I’ll need to final clean it, then place the gaskets on the rails to seal between the arch (where the fire is) and the SS pans. Also a gasket goes between the syrup pan and the flue pan. I also will need to connect the pipes and valves to bring concentrate (I run my sap thru an RO [reverse osmosis] to remove much of the excess water to make it “concentrate”. to the flue pan, then from the flue pan to the syrup pan and finally once it becomes syrup it flows to a draw off tank. From there it will be pumped thru high temperature silicone hose by an air powered diaphragm pump to my finishing pan. The finishing pan is also a 2×6 and it’s propane fired. Once I get enough to bottle or to fill a stainless barrel or 2 I heat the syrup to about 200-205F and pump it thru my filter press, from there it’s sent to a water jacketed bottler or to a barrel or 2.

Once I have a batch in the bottler it gets final density verified and graded. The grade and % of light transmission is recorded in my log book and bottling then proceeds The syrup also at this point gets a final taste test. Once in a retail container the grade is labeled and I also mark the lot number (actually each label has a serial number and that range in sequence is entered in the log book in case it’s ever needed. So far I’ve never needed to refer back but it’s always possible. I also save the test vial from every batch (the light transmission and grade) with a date code on it if needed.

My old evaporator had a trench under it the full length of the sugarhouse, I decided that was not needed, thus I’ve concreted it in about half way so far, the rest will be concreted in this summer. That trench just proved to be a tripping hazard. I’m now looking for an appropriat oil burner to use and once i start getting ready the fire bricks and blanket insulation will be put into the arch, the wood fired door will be removed and a steel plate will replace it, with a mounting hole to mount the oil burner. This burner will need to get a 3.5 GPH nozzle.

After a year I’ll decide if I used too much oil, if yes, I’ll look for an RO that can get the sap to a higher % of sugar and proceed if necessary. My currant one only gets to about 8% in one pass and about 12% in two, it will not get higher, the pump is not powerful enough. That will come next year about this time of year. I’m thinking it’s likely but not sure.

I’ve got a friend who converted a larger evaporator from wood to oil and he says he never wants to go back to wood, oil, while costing more boils far more steadily, faster and as you run out of concentrate you just flip a swithch and clean up and leave. He’s now on his second oil fired, he moved and has far fewer taps, thus a smaller evaporator. With wood fired you need to know when your concentrate level is at a specific level, stop adding wood and wait from 60-90 minutes depending on the wood you are burning, then you can clean up and leave. That 60-90 minutes oil doesn’t need, just flip the switch and the boil stops instantly. That’s an avg of 75 minutes earlier to go home, be with the family or get some sleep, all important things.

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