Now that the syrup season is in full swing, here are a few tips to keep your evaporator running smoothly. When running your evaporator, the goal is keep a steady boil across the entire rig with the hardest boil occurring in the flue pan. It’s important to remember you remove 80% of the water is removed in the flue pan. This requires that you get the maximum amount of performance out of this section of the evaporator. When foam builds up in the back pan, the evaporation rate decreases and the liquid level drops. Once the foam level drops (using defoamer), the float registers that there is not enough sap in the rig and reacts by sending a large slug of raw sap into the flue pan. This immediately slows the boil. This reaction is eventually transmitted across the entire evaporator in the form of a large batch of syrup that comes off all at once, instead of small batches coming off at regular intervals. In most cases, large batches can be traced back to inconsistent foam management.
Let’s take a close look at defoaming an evaporator. First – the products used in this process. Today’s commercial defoamers are made of a natural food grade product. They come in liquid or powder form. Several methods are used to put defoamer in the evaporator. One is to simply put it in by hand. If this method is used, the defoamer should be put into the evaporator somewhere near the flue pan inlet. Other methods would be the use of a defoamer cup in the corners of the pan and injection devices that administer a precise number of drops over a set period of time. The cups work well on larger rigs where the boil in the flue pan is very aggressive. I have found on smaller rigs, especially if no pre-heater is used, the boil never gets close to the cups and the defoaming action is inconsistent. The most consistent results can be obtained with the by-hand method simply by placing a precise number of drops into the flue pan every 5 to 10 minutes or every time you fire the rig. A timer works well to remind you to keep this process going. For me personally, the biggest problem I have is remembering to place the defoamer in the flue pan because we are not using wood and not firing on regular intervals.
The number of drops used varies anywhere from 3 drops for small rigs up to 10 drops on larger rigs. The width of the evaporator determines the number of drops and this increases by 1 drop for every 6 inches of evaporator width, (3 drops in a 2 foot wide rig, 4-5 in 3 foot rig, up to 10 drops on a 6 ft rig). There are only two places to put defoamer, in the inlet corner of the flue pan and, only if needed, at the draw off point. One of the biggest mistakes is to put defoamer randomly across the middle of the pans, especially the syrup pan. Doing this kills the boil and promotes intermingling of syrup of different densities. The result will be the dreaded big batch. Incidentally if your syrup taste a little oily, and I sincerely hope not, you are probably using too much defoamer. If you are organic, use organic Canola Oil in place of commercial defoamer.
Managing foam looks simple (and it is!), but if you forget, the penalty is a bunch of chain reactions that can ultimately end up in inconsistent syrup draw-off and improper density of the syrup that you are processing. You end up constantly trying to compensate in the syrup pan for a problem that should have been handled in the flue pan. If it gets too far out of control and you end up taking too much syrup off your front pan at one time the result could be a scorched pan. When evaporators do not run smoothly bad things happen. Been there done that and believe me it is no fun.
One new item I tried during the 2015 season was Wendell Maple Foam Fighter. It is an electronic device that precisely places defoamer into the evaporator inlet over a precise number of minutes. On the first day of use, we were boiling fast and hard and the foam was starting to really build. I kicked on the new device and within 15 minutes the foam in the flue pan settled down. When it came time for the first draw-off of the day, we expected the usual bigger than normal batch. That did not happen. The first draw-off was average size and the rest were the same and evenly spaced over the time we were boiling. If this any indication what this device will do, it was money well spent.