Farming Magazine - December, 2011


Making a Maple Vacuum System More Efficient

By Tim Wilmot

There are never too many useful tips for a maple producer who wants to make his or her operation more efficient and trouble-free. This past September I learned some new ones at a vacuum workshop held by the Vermont Maple Sugar Makers' Association in Shaftsbury, Vt. The instructors were Nick Atherton, service manager at CDL in St Albans, Vt., and J.R. Sloan of Green Mountain Mainlines in Fairfield, Vt. While these workshops were primarily aimed at sugar makers with systems of less than 1,000 taps, much of the information that was shared could apply to systems of all sizes.

J.R. Sloan installs tubing all over the Northeast and has seen operations of all sizes. He claims that the number one reason for a failed system in any woods is grade - not laying out the system to keep some grade on all the lines. Lack of grade at any point in the line causes sap to pool in a sag, diminishing the vacuum beyond this point. Additionally, because the sap will freeze in these sags on a cold night, ice and slush will come down the lines in the morning and may interfere with the sap extractor ("releaser"). A mistake that many producers make is running mainlines from a nice slope into an area with a shallow slope, or even no slope, just to pick up some taps in a flat area. In many woods those taps can be picked up by a separate mainline to avoid flattening out the whole system. In the case of trees that are clearly below any logical path for a mainline, Sloan recommends not using sap ladders; instead he uses the vacuum in the mainline to pull the sap from the trees to the mainline by running individual lateral lines with five taps per line.

Sloan had many other tips relating to tubing. When he estimates materials for a job, he uses the formula 6 feet of mainline and 20 feet of lateral line per tap, which works in most woods. He uses only three sizes of mainline: 1, 1.5 and 2-inch, to avoid having too many kinds of fittings, and he likes 1-inch minimum for better vacuum transfer, especially on flatter slopes. To gauge the slope, use a sight level, which Sloan recommends testing prior to use by sighting along horizontal siding on a building and making sure that the bubble is really on the center line when the instrument is held at level. Whenever possible, he recommends keeping 5/16-inch lateral lines short and relatively straight - when in doubt always add another line and mainline saddle rather than lengthening a lateral line to pick up one or two more trees. Saddles add cost, but the shorter lines reduce the money spent on tubing. For saddles, Sloan uses only models that have a rubber gasket that can be separated and placed on the mainline after the hole is drilled; this ensures that the gasket will be flat and provide a tight seal. He uses only single-port saddles; saddles with two ports might seem like a money saver, but a leak on one of the attached lines will partly block the vacuum and sap flow from the opposite line. He likes to run mainlines on either side of a woods road rather than across the road, so that he can drive up in his four-wheeler and check each line for leaks by looking at the movement of sap where the tubing enters the saddle. Finally, for the benefit of the workshop attendees Sloan added: "You don't necessarily need a wet/dry system for less than 1,000 taps, and don't go home and redo everything, instead strive for steady improvements where possible."

Nick Atherton talked about pumps and sap extractors, and pointed out that many of the vacuum issues that his customers encounter are related to the extractor. While many producers with smaller vacuum systems prefer mechanical extractors over electric extractors due to their relative simplicity, Atherton feels that the pumps used in smaller systems often do not supply enough vacuum to keep a mechanical extractor running trouble-free; at a minimum, 2 hp or 20 CFM is recommended for a mechanical extractor. To provide as much vacuum as possible, the dry pipe from the vacuum pump to this extractor should be oversized - 1.5-inch diameter at a minimum - and problems often occur when trying to put the extractor too far from the pump. With smaller vacuum pumps, Atherton feels that an electric extractor will be much more satisfactory. Although it requires a separate water pump to move the sap to the tank, and it must be kept from freezing, the electric extractor does not pull vacuum from the tubing system when it dumps sap. With this type of extractor, steps must be taken to ensure that the vacuum present in the extractor will not de-prime the water pump and keep it from evacuating the sap. The line from releaser outlet to the water pump inlet must be leak-free and have no unnecessary connections. Use a swing check valve on the outlet side of the water pump to maintain vacuum in the pump, and use small-diameter hose from the extractor belly to the outlet side of the pump impeller to balance the vacuum in both units.

Finally, Atherton explained that although the liquid ring pumps used in many maple operations are more "bulletproof" and less likely to cause maintenance issues, the type of pump that often fits into the budget of small producers is the rotary vane pump, which can be straight from a dairy system, in which case vacuum will usually be limited to around 18-inch Hg, or a vane pump adapted for maple with an oil flood system that permits higher vacuum. One of the most common maintenance issues with a vane pump occurs when sap gets into the pump due to a malfunction of the extractor and/or moisture trap. The pump does not need to be taken apart, but needs to be flushed using flushing oil, which is available through many pump suppliers. Kerosene mistakenly used instead for this purpose will cause the vanes to dry out and stick, leading to difficulty starting the pump.

The lessons described here are just a few of the many that can make a sap collection system more economical and efficient. Experts don't necessarily agree on which method which piece of equipment offers superior performance. The best choice for people with maple operations large and small is to listen to a variety of successful producers, installers and technicians, and a great way to do this is to spend time at the annual maple schools, such as those held every winter in many northeastern states.

The author is maple specialist with University of Vermont Extension and Proctor Maple Research Center in Underhill Center, Vt.