Tapping and Tubing

Vacuum: an Explanation

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The concept of vacuum is the exact opposite of what most people think of when they see a pump and some lines. Most people think of air being pushed though a line, similar to a compressor with an air line. Air can be compressed to an infinite level as long as what is holding that air does not explode. With vacuum it is the exact opposite. Vacuum is pressure based on the force that the earth’s atmosphere exerts on all of us. This amounts to about 15 pounds per square inch of surface or 29 inches of mercury. This pressure is also referred to as barometric pressure. As the atmosphere fluctuates, we might know by watching the weather that barometric pressure goes up and down with changes in atmospheric air movement. If you remove air from a container, you will produce a vacuum inside that container. That lack of air creates a negative pressure that is measured in inches of mercury (element abbreviation Hg) and will never exceed the outside barometric pressure.  As molecules of air are moving toward the pump and that air is ejected at a volume over a period of time, in this case Cubic Feet of air per Minute (CFM), the capacity of the pump will determine how fast this will happens.

What we are trying to create inside our sap lines is the absence of air or a perfect vacuum. Most producers grasp these basic concepts they also realize that there is no way to maintain a perfect vacuum inside their sap lines. Damage from wildlife and aging equipment introduces air into the system. Even the tree allows air to be introduced. For this reason we always allow for 1 CFM of air movement for every 100 taps. The problem with most systems is that we are getting way more air into the system than we want. This puts a greater burden on the pump to remove the air. The speed at which this is accomplished is largely determined not only by pump capacity, but how the tubing system is constructed. Line length and diameter in relation to the pump and the amount of liquid in the lines has as much to do with it as pump size. Couple this with the fact that most producers are attempting to run at high vacuum (as close to the daily barometric pressure as possible). The problem with this is that it is counterproductive to pump efficiency. To go from 12 to 15” (Hg) vacuum requires 20% more system capacity, 12 to 18” requires 50% more system capacity and from 12 to 20” requires 80% more capacity. Placing your woods on vacuum can yield more sap per tap, up to a 50% increase; however, this greatly increases the demand on your pump and everything behind the pump – from the shed to the tree – has to be in optimum condition. You can see in one short paragraph there is more to running a vacuum system than simply hooking a line to a vacuum pump.

The simplest way to design a vacuum system is to start with a tubing system and then install a pump that will effectively handle the tubing system. First, you need to determine how many taps will be on each mainline. You need to know the slope of those mainlines. Sap flowing in a relatively flat woods will move more slowly than sap moving down a mountain side. Each line has a volume capacity for the liquid it is conducting. For example, a 1 inch line on gravity will conduct 50 gallons per hour on a 2% slope and 75 gallons per hour on 6% slope. A good rule of thumb is that you want no more than 40% of the space inside the tubing holding liquid. The rest is needed to move air. The vacuum line is dual purpose, but its main function is air movement which facilitates the actual vacuum effect. If the sap level rises to the point that it blocks that air movement then the vacuum level quickly drops off. This along with excessive leakage are the main reasons for vacuum level drop from the pump out into the woods. In other words, using too small a diameter line will result in lines running full of liquid and dropping your optimal vacuum levels. One of the best ways to overcome this problem is to use dual-line conductors, using the top line for air movement and the bottom line for liquid. The use of this type of system is vital in flat woods with very little slope. Getting your lines sized correctly is the first step in creating an efficient vacuum system. In the next post we will discuss the importance of vacuum line sizing and distribution.

Author: Les Ober, Geauga County OSU Extension

Tips on Using Vacuum and Maintaining Tap Hole Sanitation

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Looks like Ohio Maple Producers may be headed into another sugaring season with unusual weather patterns. As of February 5th, 2013, there has already been a significant amount of new syrup made in NE Ohio. The real challenge is setting up your production system so that it can deal with the changes in the weather. You may say that there is nothing we can do about the weather; we have to accept what comes. That is right, however, you can change the way you produce syrup to take advantage of every opportunity that comes our way.  If you take a look at what happened in Ohio over the past several seasons you will notice some definite trends. Yield per tap dropped from .286 gallons of syrup per tap in 2008 to .169 in 2010. Last year, we once again lead the nation in Yield per tap (.244).  One of the main reasons for this was that favorable weather patterns enabled producers on vacuum tubing systems to collect a greater volume of sap on more days over the course of the entire season.  The end result was a huge average yield per tap. How you manage your system during the season is key.

Taphole sanitation has become the buzz word of the industry. Taphole sanitation is all about keeping your drop lines and spouts free of bacterial contamination. The piece of technological equipment that may have started it all is the Check Valve Adapter Spout. The warm weather in Ohio over the last several years has proven to be a good test for the new spout that is designed to prevent a back flow of bacterial-laden sap back into the tree. It works well in warmer climates like Ohio.

Solutions for taphole sanitation are based on research done at Proctor Lab in Vermont and the work done at Cornell University. What it comes down to is that you need to be replacing your spouts every year. Plain and simple. You should be replacing your drops every other year. And if you shut off your vacuum for extended periods of time during the season when it is not frozen, then you should consider using the Check Valve. The newest model goes directly on the line without the stubby adapter and looks very promising. If you run your vacuum continuously then one of the new polycarbonate spouts may be the answer. Check your drops frequently looking for bacterial buildup. Also this is a prime area where squirrel damage occurs so watch for leaks.  At the end of the season, make sure you get all of the sap out of the drops. The best way to do this is to clean under vacuum if you can. This removes the maximum amount of liquid out of the lines.

One question that comes up a lot is whether you should shut down your vacuum pump during extended periods of warm weather or let it run? Many producers are finding out that when you run the vacuum pump continuously, you will continue to collect sap even when the temperatures remain above freezing for several days. In most cases, the sap you collect will produce enough syrup to offset the cost of running the pump. In fact it is better to keep the pumps on and keep something moving through the lines. This cuts down on bacterial growth in the lines and the moving sap will keep the lines cooler. But it takes a good vacuum pump to run under warm conditions. The average vane pump (dairy pump) struggles in this environment. They are not designed to produce high vacuum over long periods of time. They are designed to work comfortably at 16 inches of vacuum. This is the vacuum that you use to milk cows. The best pump choice for extended high vacuum use is a liquid ring pump. They are cooled by water or oil and they hold up well under long periods of continuous use.

The last several years should have convinced everyone that tubing on vacuum pays. The Financial Analysis Guide released in Winter 2012 by The Ohio State University shows that the cost of production can be improved by installing and running a vacuum tubing system. It is clear that technology is and will continue to drive profitably and production in the maple industry regardless of what Mother Nature throws our way.

Author: Les Ober, Geauga County OSU Extension

Tapping Basics

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The recent warm spell had many maple producers fired up and ready to tap. If you frequent a maple chat forum such as Maple Trader you hear a lot of speculation on when, where, and how to tap. There appears to be as many theories on tapping as there are tap holes. Let’s look at the tapping process.

The first thing to remember about tapping trees, whether you tap early or late, is that you only have one chance to get it right. Making a mistake the first attempt can screw up the whole season. It is more important how you tap than when you tap. First, we need to take a look at the trees and determine which ones to tap. To do this, we follow a set of tapping guidelines that are published in the North American Maple Syrup Manual. Depending on whether you follow the traditional or the conservative guidelines you will be tapping a tree no smaller in diameter than 10 to 12 inches.  This is where a recent study done by the University of VT Proctor Lab adds clarity to the ongoing debate. The research work was done by Dr. Abby van den Berg at Proctor at high yield sugar bushes throughout Vermont. High yield was operations with vacuum systems using 20 plus inches of vacuum to collect sap. What Dr. van den Berg found out was that the current conservative tapping guidelines of 12 inches in diameter minimum size was appropriate for tubing systems using modern high vacuum collection systems.

The study compared the percentage of functional and non-functional wood in the trees of different diameter and applications. Functional wood is new growth wood, the kind you can tap and get peak production. Non-functional is the dead wood that is left behind as a result of tapping. This wood is the stained non-productive wood that you see in cross sections of maples that have been tapped.  At 12 inches diameter a healthy tree will regenerate enough new growth (90% or greater functional wood) to maintain tree growth and adequate sugar production to maintain tree health. Trees under 12 inches saw a steady decrease in the percentage functional wood at an earlier age. This is important because you want to consistently be tapping into new wood year after. If the percentage of functional wood is on the decline this makes it harder year after year to find new wood to tap. It could lead to a decline in overall tree health and productivity. A quick way to determine tree size is to use a rope 38 inches inches long. If you get to a tree and you can place the rope around the girth of the tree without the two ends of the rope touching then you have a tree at least 12 inches in diameter. There were other factors in the van der Berg study that could also influence the reduction of functional wood.

The standard drop line length recommended and used in the study is 30 inches. It was found that if the drop length was reduced, it in turn reduced the tapping zone of the tree. The result was a decline in the functional wood area at an earlier age. This is very important.  As we work, innocently enough, our drop lines get shorter and shorter as repairs are made and old spouts are cut off and new spouts are replaced.  Slowly but surely, this greatly reduces the tapping area on that tree. If you are following the new tap sanitation recommendation of replacing drop lines every other year you can overcome this problem of short drop lines by replacing them with new 30 inch drops. Also consider on trees with very large diameters that you may need an even longer drop line. Another factor is using the old style large spout. This will increase the size of the non-functional wood for each tap. It is always wise to use the new 5/16″ tap if you want to promote tree health.

The study at Proctor used a one and a half inch tapping depth with the 5/16″ spout throughout the study. One and a half inches is the correct tapping depth for today’s maple operations and maintaining that depth can be difficult. One way is to put a piece of tubing over the bit exposing 1 ½ inches of bit allowing you to reproduce that depth each time you drill. Also consider how you drill. Make sure you hold the drill straight drilling a round hole, angled slightly downward. If you wiggle the drill, you will have an oval shape hole that will leak sap and lose vacuum. Do this enough times and you will be losing vacuum all over the place. Use a sharp bit that cleans the shavings out of the hole. Shavings left in the hole will attract and promote bacterial growth.  The spout must be seated properly but do not over drive the tap causing it to split on top and on the bottom. Use a light tapping hammer and leave the sledge hammer at home. Today most producers use cordless drills to tap. It is important to use a drill you are comfortable with – the new drills with Lithium batteries are light and are a good investment both in battery longevity and ease of handling.

Establish a tapping pattern that you use every year, such as 6 inches over and 6 inches up or moving to the opposite side of the tree.  Do not try to tap a tree year after year on the south side because someone told you it would run early. With buckets expand your dumping zone to include high and low buckets.  What is important is getting the job done right the first time. Remember there is no pride in bragging you tapped 1000 trees today if half of them are screwed up. Slow down and make your work count. Here is the website for the University of VT Fact Sheet on Tapping.

Author: Les Ober, Geauga County OSU Extension