There is plenty to learn from this video focused on Proctor’s red maple research. How much sap is produced? How sweet is the sap? What sort of quality can be achieved with the syrup? This research has a similar set of questions to the USDA ACER grant we are working on here in Ohio comparing sugar maples to the red x silver hybrids on The Ohio State University-Mansfield campus.
CODIT stands for Compartmentalization of Decay in Trees, and sugar maples are darn good at CODIT! Mark Isselhardt, during the 2021 virtual Ohio Society of American Foresters spring meeting, gave an excellent microscopic and physiological explanation of how maple trees wall off and seal up old tapholes.
Why does understanding compartmentalization matter to a maple producer? Compartmentalization creates the all-important non-conductive wood that sugarmakers try to avoid with each year’s new taphole. And just in case you were wondering – how much does it matter? Through work conducted at University of Vermont’s Proctor Maple Research Center, Mark Isselhardt document sap yield declines of 70-75% when a taphole intersects non-conductive wood.
Despite being virtual due to COVID-19, 2021 Ohio Maple Days – or more accurately Ohio Maple Day sans the “s” – was a success. The audience, two hundred or so strong, heard presentations on tapping and updates from our ACER grants in addition to how production might be increased with red maple. A big thanks to this year’s speakers and an extra round of applause for the committee who worked hard on an event that looked quite a bit different than in years past. One silver lining to having a virtual event is that the sessions are easily recorded.
Visit the Ohio Woodland Stewards Maple page and scroll to the bottom of that webpage to access the different presentations. Let us know what you think and send us any questions, comments, concerns, or suggestions to talk topics for next year!
The goal of the previous two articles (Part I, Part II) and this final installment is for you to realize that there are many factors that go into installing and running a maple vacuum tubing system. All the factors are interrelated and each one needs to be careful considered on the part of the operator. The below information is contained in the Cornell New York State Tubing and Vacuum System Notebook (NSTVN) written by Cornell University’s Maple Specialist Steve Childs. Much of the information is these three posts is a synthesis of past content with some more recent best practice guidance.
Part I introduced basic concepts of vacuum in a tubing system, some different variants within vacuum systems, and the different factors (most well within the control of the producer!) that influence vacuum levels throughout a system. Part II walked you through how to calculate vacuum levels within your system and how to ensure your production needs are met by your system’s capacity. The final installment will help direct you towards a vacuum pump that will do the job you need it to do.
When someone brings up the subject of vacuum, one of the first questions producers ask is, “What size vacuum pump will I need to run my system?” They will also sometimes ask, “Will the old rotary vane pump my grandfather abandoned in the barn 10 years ago (or longer…) do the job?” The question I also ask back is this, “What vacuum level do you want to run at today and into the future?”
We should get the second question out of the way first. Grandpa’s pump was designed to milk cows, and Bessy would get a little fussy if the vacuum level were to jump above 15 Hg. So the simple answer is that Grandpa’s pump will work, but it is not designed for optimizing maple production. But if you are happy with a modest increase in production beyond simple gravity-fed lines, dust off the old rotary vane pump and run it at the recommended RPM. Moving on to where the maple industry has evolved.
To review, vacuum pumps are designed to remove air from the system, and we already know that vacuum pumps are rated in terms of their ability to remove cubic feet per minute (CFM) from the system. Two additional factors come into play when comparing vacuum pumps. One is the horsepower rating, or the power required to remove air at high levels of vacuum. As the air is removed from an enclosed area the molecules of air in that area become very sparse. A pump must work very hard to remove the remaining molecules of air in the system. The pump must also overcome the force of the negative pressure inside that enclosed area, and this challenge requires more horsepower. A larger pump with a higher CFM rating has a higher capacity to accomplish this task but bigger pumps also require higher horsepower motors. The final factor is pump speed. If you turn a pump faster your will move more air thereby increasing the pump’s capacity. However, over-speeding a pump can cause excessive wear on the pump. This becomes a critical factor when sizing a gasoline of diesel motor driven pump. Pullies need to be sized correctly or performance is sacrificed.
Caption: Vacuum gauge measuring 26+ inches of vacuum
Most of today’s liquid ring, flood vacuum, rotary claw and new age rotary vane pumps are designed to run at vacuum levels up to 29 inches. An important thing to remember is that all pump ratings and vacuum level capacities are preformed using a standard test at the factory removing air from a sealed vessel and a performance curve is developed. This is done in a controlled environment. Now the question becomes what happens when you lower the air temperature and increase or decrease the barometric pressure? The result is confusion. Today, many maple equipment companies are simply listing pump sizes by motor horsepower instead of by CFM capacity. I have personally never seen optimum conditions out in a sugarbush in February and March, and as pointed out above, motor horsepower is only one factor determining pump capacity.
Another question I have is this – “What is the likelihood of that pump reaching 29 inches of vacuum in your sugarbush?” How many times have you heard producers tell you that the pump gauge mounted somewhere near the inlet of the pump is reading 28 inches of vacuum and therefore he must be producing 28 inches of vacuum at every tap in his woods? The harsh reality is that out in the woods he might be struggling to produce 15-20 inches of vacuum. What has the producer not factored in? First, line loss because line diameter can be restricting flow and impairing the ability of the vacuum pump to remove all the air from the system. Second, the producer might have an abundance of leaks in his or her system. The reality is that the only vacuum reading that counts is the reading that is taken out in the woods at the last tap. Today in the age of maple tubing system monitors, producers can know exactly what level of vacuum they have at the end of each line. They can also monitor the level of vacuum at the releaser and make the comparison to the end of their lines and isolate and correct problems as they occur.
To determine what sized pump your operation requires, you should begin by constructing an evaluation like the one used in the NY State Maple Tubing and Vacuum System Notebook. Start by calculating the proper line size for the number of taps you have now and do not forget to think ahead regarding possible expansions you may make in the future. Factor in your equipment such as the releaser you want to run, whether you have lifts in your system and other CFM consuming features. Do not forget to build in some reserve performance to allow for possible leaks and for keeping up with your during peak runs. At this point, you should have a good idea of the right-sized pump for your operation. If you are right on the edge of meeting CFM demand, you should strongly consider buying a pump one size or even two sizes bigger than you planned especially if expansion is in your future. What’s the old adage? Buy once, cry once.
The Bottom Line
You have now made all the calculations and are beginning to understand the logic and principles behind setting up a vacuum tubing system. So what is the return on investment (ROI) for spending money on a bigger pump and increasing the size of your lines? For that answer, let’s look at yield research done at UVM Proctor Research Center. For the UVM study, the goal was to determine yields in systems up to 25 inches of vacuum. The results showed that sap yield doubles when vacuum is taken from 0 to 15 inches (8 gallons per tap). From 15 to 20 inches, the payoff was a 3 gallon increase, and pushing vacuum another 5 inches to 25 Hg resulted in an additional 2.5 gallons. At 25 inches vacuum, you have added nearly 14 gallons of sap per tap. Even at 20 inches of vacuum, the additional yield is still over 10 gallons. In today’s market you can add a modern vacuum pump, a releaser, and moisture trap for less that $10,000. If you increased your production by 75% on 1000 taps, you would go from 250 gallons a year to 400. If those 150 extra gallons sold on the retail market for $50.00, your return would be $7,500 dollars. At that rate, you have paid for your vacuum upgrade in two years. What are you waiting for?!
This is the final installment in the 3-part series dedicated to optimizing your vacuum tubing system. Be sure to leave questions or comment below.
The goal of the previous article (Part I), this article, and the next is for you to realize that there are many factors that go into installing and running a maple vacuum tubing system. All the factors are interrelated and each one needs to be careful considered on the part of the operator. The below information is contained in the Cornell New York State Tubing and Vacuum System Notebook (NSTVN) written by Cornell University’s Maple Specialist Steve Childs. Much of the information is these three posts is a synthesis of past content with some more recent best practice guidance.
Part I introduced basic concepts of vacuum in a tubing system, some different variants within vacuum systems, and the different factors (most well within the control of the producer!) that influence vacuum levels throughout a system. Part II will walk you through how to calculate vacuum levels within your system and how to ensure your production needs are met by your system’s capacity.
It is not uncommon during a peak or flood run for your vacuum to drop. If you maintain your lines and are running a tight, leak free system what is the possible explanation for this sudden drop in vacuum? One possible reason is CFM Allocation (air flow measured in Cubic Feet per Minute). In the most basic systems, all vacuum lines are properly and equally sized with the same number of taps per line and all running to a single collection point. The CFM requirements to maintain optimum vacuum will be equally distributed across the whole system. For example, if you have 4 lines of equal diameter connected to a 60 CFM vacuum pump each line would receive 25% of the vacuum CFM (15 CFM). According to theory that would be enough vacuum to run 1500 taps on each line. To use another example, if you are using a 20 CFM pump on a system with 4 equally sized lines and each line serviced 200 taps each for a total of 800, then you would be allocating slightly less than 5 CFM to each line – still more than enough to run each line. However, Total CFM utilization is not always dictated by the number of taps in the woods. One must account for the CFMs utilized by other components of the system, such as if you run a mechanical releaser and other add-on features like lifts or reverse-slope releasers. This reduces the number of available CFMs to accommodate tree loss and leak loss.
Caption: Vacuum Pump with Vacuum Gauge
Now let’s add some complexity to our scenario. Let’s say you expand your 800 tap operation by adding 600 taps to the backside of one of your 200 tap lines. What happens to your 20 available CFMs if you remove a 1” line and replace it with a 1 ¼” line to service the line that now has 800 taps. Now you have 3, 1” lines and the new 1 ¼” line servicing 1400 total taps. Now you must calculate your line allocation to determine proper CFM distribution.
The first step is to calculate the cross-sectional area of each pipe which is easily accomplished with basic geometry’s “area of a circle” equation.
|Cross-sectional Area of a Pipe|
|1 ¼”||1.23 in2|
|1 ½”||1.77 in2|
Second, you need to determine the percentage of your total vacuum going to each line. As a reminder, our example has 4 mainlines: 3, 1” lines and a single 1 ¼” line. Here is a simple way to determine vacuum distribution.
The cumulative cross-sectional area of our 3, 1” lines = 0.78 + 0.78 + 0.78 = 2.34 square inches. And for the single 1 ¼” line, 1.23 square inches. The grand total sums to 3.57 in2.
Now divide the cross-sectional area of each line by the total to see what proportion or percentage of vacuum is being applied to each line. You will find that each 1” line is pulling 22% of your overall CFMs which leaves 34% of the vacuum for the 1 ¼” line. By CFMs (remember you started with 20 CFMs), each 1” mainline is pulling a maximum of 4.4 CFM and the single larger line is hovering just under 7.
You can quickly see that you are sending way too many CFMs to each of the 1” lines and not enough to maintain good vacuum on the 1 ¼” line. A quick solution would be to combine the 3, 1” lines into a 1 ¼” manifold with the existing 1 ¼” line going directly into the releaser. That would result in the releaser with just two lines coming out each equally sized at 1 ¼”. This solution would re-allocate 50% of the CFMs to each line solving the problem of line allocation.
It is important to remember, you need to account for leaks that will introduce more air into lines. You might be able to maintain peak vacuum on most average days, but will your system keep up with sap flow when the big run hits and you need to move as much air as fast as possible to maintain vacuum levels. If you have your lines sized properly, you now need to take the next step to determine what size pump you should purchase.
Stay tuned for Part III (What Pump to Purchase?) on Thursday and be sure to leave questions or comments!
The goal of these next 3 articles is for you to realize that there are many factors that go into installing and running a maple vacuum tubing system. All the factors are interrelated and each one needs to be careful considered on the part of the operator. The below information is contained in the Cornell New York State Tubing and Vacuum System Notebook (NSTVN) written by Cornell University’s Maple Specialist Steve Childs. Much of the information is this and the next two posts is a synthesis of past content with some more recent best practice guidance.
When we talk about tubing systems, we have two roads to travel. One is a gravity system and the other is a vacuum system. A conventional 5/16” gravity system is not much different from running sap into a bucket. The yield is much the same as collecting sap in a bucket. When we add vacuum to a tubing system, we increase the sap yield 5% for every inch of vacuum we generate in our system. For example, if we produce 15 inches of vacuum in a line, we should be able to almost double our sap yield. The first year after installation is always the best. As time on a system accumulates, wear-and-tear hampers performance.
Caption: Year 1 Production with a Brand-New System Should Provide Your Best Vacuum Levels
The definition of vacuum is the absence of air. The maximum level of vacuum achievable on any given day is determined by the barometric pressure. This means that our vacuum level can never exceed the barometric pressure in the location of our sugar bush. There are two way to measure vacuum pump performance, Inches of Mercury (hg) and Cubic Feet per Minute (CFM). Inches of mercury measures the negative pressure produced when air leaves the line. For example, if 50% of the air is removed then the inches of mercury should be somewhere between 14 and 15. At 25 inches of mercury, approximately 85% of the air has been removed from the lines. CFM on the other hand measures the amount of air being evacuated from the lines in units of cubic feet per minute. This is the amount of air that a vacuum pump is pulling out of the system in one minute’s time. Where is the air coming from? The answer is gas that is forming inside the tree and being expelled through the tap hole. As a rule of thumb, there is a 1 CFM requirement for every 100 taps on the line. However, the biggest contributors are leaks allowing air to enter the system through damaged or aging tubing. This statement emphasizes the importance of managing leaks in a vacuum tubing system.
Caption: Vacuum Gauge Measuring Vacuum in Inches of Mercury (hg)
Speaking of leaks, the most important part of operating any maple syrup system is the time you spend in the woods making sure your vacuum tubing system is leak-free. Much of the rest of the article is spent discussing different technologies and equipment, but the simple fact of the matter is this – the best equipment with poor care in the woods won’t do you a lick of good when it comes to putting more maple syrup on tables of your customers. You must always account for leaks that introduce air into lines. You might be able to maintain peak vacuum on average days, but your system will show its weak points when sap flows are running fast and you need to move as much as air as fast as possible to maintain vacuum levels. Being able to spot and repair leaks quickly is essential. To accomplish this, you should design your system so you can isolate lines to pinpoint problems. This can be done by compartmentalizing your system with valves and vacuum gauges placed at the starting point of each line. The installation of a tubing monitoring system can be a wise investment as well, and the time saved and extra sap produced will pay for the cost of the upgrades in short order.
Back to our lesson on vacuum and barometric pressure. There are factors that have a direct effect on barometric pressure. One is altitude. As the altitude increases the maximum barometric pressure declines (rule of thumb: for every 1000 feet of elevation you lose 1 inch of vacuum). For example, at sea level, or 0 altitude, the average barometric press can be 29 inches; at 2000 feet, the average maximum barometric pressure obtainable is only around 28 inches. In addition, barometric pressure changes under different environmental conditions, and variations in barometric pressure caused by atmospheric changes can occur multiple times in a day. If we are running a vacuum pump under a low barometer at 2000 feet elevation, we might struggle to maintain 28 or even 27 inches of vacuum on a very tight well-maintained tubing system.
Sap moves down the line by gravity on a system of tubes suspended with wire. The basic components are spouts, tees, and drops moving sap from the tree into lateral lines. A lateral line should have no more than 5 to 10 taps per line and should be no longer than 100 feet in length. The lateral lines flow into main lines. In large systems, secondary mains flow into Wet-Dry lines and or trunk lines (large diameter lines) that move the sap to a central collection point. To properly function, sap lines should be straight, pulled tight, and sloped downhill. To this point gravity systems and vacuum systems are similar, with the gravity system relying on slope and Newton’s law of gravity to move the sap.
Caption: 65 CFM Bush R-5 Vacuum Pump
When vacuum is added to the system, sap flow is aided by the movement of air. The components of a vacuum tubing system are the vacuum pump, which is connected to lines via a sap releaser. Even though it is called a vacuum pump, it is not a pump in the conventional sense of the word and that is a bit confusing. A conventional pump moves liquid creating pressure ahead of the liquid and suction on the backside of the liquid. There are other types of pumps used in maple production. For example, a diaphragm pump is a conventional pump and that creates enough suction (secondary vacuum) to draw sap from a tree. However, if liquid is not present in the lines that suction can be lost. A true vacuum pump moves air, not liquid and it creates a higher level of vacuum (absence of air) as the air is removed from the lines. That level of vacuum can be maintained with or without sap in the lines and will only drop if a leak allows outside air to enter the line. Because the pump is designed to move only air, the liquid must be separated from the pump. This separation process is performed by a sap releaser. If sap enters the vacuum pump severe damage to the pump can occur! To prevent this from happening, a moisture trap is placed between the pump and the releaser.
Caption: Sap house releaser (right) with Vacuum Piston Pump (left)
A properly sized vacuum pump with a proper CFM rating will be capable of removing air faster than it is introduced. However, there is one factor that can interrupt and slow that process – line size. Vacuum lines are designed to conduct air to the pump. If your line diameter is too small, the air movement will be restricted requiring more time for the pump to clear air from the lines. This phenomenon is referred to as line loss. The smaller the line the more the air flow is restricted resulting in higher line loss. As an example, a 60 CFM pump set at 15 inches of vacuum hooked to a 3“ line can maintain over 40 CFM out to 5000 feet. However, that same pump hooked to a ¾” inch line is incapable of delivering 15 inches of vacuum at 2500 feet from the pump. Line loss increases the time (recovery time) needed to evacuate air from the line and restore peak vacuum level.
What is missing from this equation? The capacity of the line to conduct liquid. Every diameter of pipe has a maximum liquid capacity. The size of the pipe that is needed is determined by the number of taps flowing into the pipe. Each tap during a peak flow might contribute upwards of 0.2 gallons of sap per hour. Once you calculate the amount of sap flowing in you can determine the size of the pipe that is needed. There is however one caveat, the steeper the slope the faster the sap moves through the line thereby effectively increasing the capacity of a given-sized line on steeper slopes. Slope can also influence sap flow in other ways. The portion of the line, 50 feet or longer with the least amount of slope, will strongly influence sap flow. Examining this critical portion of your line might dictate a necessary increase in line diameter to allow for adequate air and liquid flow. Remember, you need to move air as well as liquid through a maple pipeline. To do this you must maintain the proper ratio of air to liquid inside the line so as not to inhibit sap movement. If you look at a working cross section of tubing it should contain 60% air and 40% liquid. This is a primary consideration when determining what size of line to use in your sugarbush. If the liquid level increases beyond that ratio or is uneven (wavy), the air movement will be restricted resulting in a drop in vacuum.
Caption: Whip Connection to a Wet-Dry Line.
There are two ways to solve this problem. The first would be to increase the size of your main lines but 1 ½” inch and 2” tubing is expensive, and it adds to the overall expense of the tubing system. Still, increasing tubing size may be justified if you have a large number of taps coming into a trunk line. The other alternative is to install a dual-line conductor commonly known as a Wet-Dry Line. Composed of two lines of equal size (or a dry line slightly larger than the wet line), a Wet-Dry system can excel at moving sap across flat areas or areas where multiple secondary mainlines merge. Secondary mains may enter the Wet-Dry line at a booster, or a line configuration called a whip. This allows sap to move down the wet line without impeding the airflow in the dry line. This set-up is particularly useful in flat areas where slope in minimal and sap flows slowly which may inhibit the necessary amount of air flow. Wet-Dry lines can be a cost-effective way to move sap through areas of minimal slope.
Stay tuned for Part II in a couple of days and be sure to leave questions or comments!
The maple season is now underway and this is a good time to talk about handling your sap during and after collection. How you handle your sap prior to boiling will strongly affect the quality of the syrup you make. When quality syrup is the goal, timing is everything, and the clock starts as soon as the sap leaves the tree and doesn’t stop until it hits the evaporator.
When sap comes from the tree, it is sterile. That all changes once the sap starts to drain from the taphole. The air and surfaces surrounding the tap contain an abundance of microbes. The sap supplies the food source and a media for the microbes to grow and multiply. Research at Center Acer in Quebec found 21 different strains of microbes present in sap. At first you would think that could be problematic, but the reality is, you need certain strains of bacteria to produce the color and flavor that is unique to maple syrup. For microbial growth you also need the right temperature. Once the environment warms the sap, microbes multiply rapidly. Producers can monitor the potential for microbial growth by checking the temperature of sap. If the temperature is close to freezing, growth is suppressed. Below 40 degrees Fahrenheit, the growth of bacteria is slow, but once the temperature rises above 50 Fahrenheit microbial growth is rapid. The chances for 50 degrees and above temperatures are greatest at the end of the season.
When sap leaves the tree, the sugar is 100% sucrose. Once the sap is exposed to bacterial action, a small fraction of the sucrose is converted into glucose and fructose, often referred to as “invert sugars.” When maple sap containing sucrose, glucose, and fructose is heated, you create an amber color and a unique maple flavor. The problem is when undesirable bacteria begins to outnumber the good bacteria. This changes the chemistry of the sap. As the invert sugar level increases, syrup begins to take on a darker color and a stronger maple flavor. This produces the different grades of syrup. Syrup early in the season has a light color and very mild flavor. The maple syrup produced at the end of the season is often darker and stronger flavor. Syrup containing higher levels of bacteria can develop a very strong almost bitter off-taste known as sour syrup. The syrup consistency takes on a thick almost rubber like appearance and is often referred to as ropey syrup. Sour sap is often confused with buddy syrup because it happens most often at the end of the season. Buddy syrup is caused by sap coming from trees where the buds are getting ready to bloom. The chemistry is completely different from sour sap. Sour sap can happen any time during the season when a warm spell causes extreme flushes of bacteria growth. Sour sap can be prevented with good sanitation practices. Buddy syrup is a natural occurrence every year at the end of the season.
The quality of syrup produced from buckets and bags is best early in the season. Once the hole is drilled and the spout is exposed to the air, microbial development and taphole healing begins. Your season has begun, and you are now on the clock. A normal season for a bucket, bag or gravity tubing producer is 4 to 6 weeks. During the cold periods early in the season, the sap stays fresh just like it would if you put it in your refrigerator. Keep your sap below 40 degrees Fahrenheit and you are fine, but let it heat up to over 50 degrees and you asking for trouble. That happens readily at the end of the season. What many producers forget is that the bucket is an incubator for bacteria if it is not cleaned out regularly throughout the season. Leaving sap sit in a dirty bucket for any length of time is a problem. Remember bacteria does not grow in a clean dry bucket. If you are in a warm spell wash out your buckets and place them upside down next to the tree. If you are in a extended cold period, you should collect your buckets and let them hang until the next run. And never let stale sap sit a bucket, hot or cold.
As for tubing, we have discussed tubing sanitation multiple times over the years and those articles are in the Ohio Maple Blog Archive. Keep your lines as clean as possible throughout the season. This is difficult unless you are on continuous high vacuum. I know it sounds expensive to run the pumps 24/7, but it works to your advantage by keeping the lines cool and dry when the sap is not running. Another essential is to follow the tubing sanitation guidelines, installing new spouts every year, and new tees and drops every three years. You will improve the quality of your syrup.
Once you get the sap to sugarhouse, there are additional things you can do to improve quality. Sap that is going to be stored for longer periods of time needs to be stored in a stainless steel tank. Avoid poly tanks for sap storage. Plastic tanks are incubators for bacteria. Older galvanized tanks, like galvanized buckets, need to be discarded because of the risk of lead contamination. For the backyard producer, make sure your tank is in the shade. Pack around it with snow if possible. You can even freeze some sap and put it in the tank during warm spells. What ever it takes to keep your sap cold, take those necessary precautions. Anytime your sap reaches 50 degrees Fahrenheit and you can’t immediately cool it back down, boil immediately.
What about the evaporator? Boil your sap as quickly as possible. If you are using a reverse osmosis machine, make sure you do not let your concentrate sit. Boil it as soon as it comes through the RO. You double, triple, and in some cases, quadruple the sugar concentration in your sap, and bacteria builds fast in concentrated sap. If you are using a small evaporator, it is a good idea to drain and flush your rig. Leaving partially boiled sap on an evaporator in a warm sugarhouse can result in ropey syrup. Once the syrup is filtered get it into a barrel or a container as fast you can. Do not let it sit around. Pack your drums hot and do not open them until you are ready to use them. Do not store syrup drums in a warm building. Move them into the basement where it is cool or package the syrup at 185 degrees Fahrenheit shortly after the season. From the tree to final container, paying attention to details pays big dividends.
This is an update for an article I wrote on the Ohio Maple Blog way back in 2013. It was entitled “Tubing or Pump: How to Optimize Your Tubing System’s Performance.” A lot of knowledge has been gained since that original article. In fact, a whole new type of gravity tubing system, 3/16″, has been introduced and has been overwhelmingly accepted by maple producers.
When we talk about tubing systems we have two roads to travel. One is a gravity system and the other is a vacuum system. A conventional 5/16″ gravity system is not much different from running sap into a bucket. It does save labor but the yield is much the same. But when we add vacuum to a tubing system, we can increase the sap yield 5 to 7% for every inch of vacuum we place on our system. For example, if we produce 15 inches of vacuum in our lines, we should be able to double our sap yield.
The definition of vacuum is the absence of air. The level of vacuum that is achievable is determined by the barometric pressure for any given day. This means that our vacuum level can never exceed the barometric pressure in the location of our sugar bush. There are factors that have a direct effect on barometric pressure. One is altitude. As the altitude increases the barometric pressure decreases. At sea level, 0 altitude, the average barometric press can be 29 inches and at 2000 feet the average barometric pressure is approximately 28 inches. In addition, barometric pressure changes under different environmental conditions. It can change multiple times during the course of a day. This is most important when we are boiling syrup because it changes the boiling point of water. But if we are running a vacuum pump under a low barometer at an altitude of 2000 feet, we might also struggle to maintain 27 to 28 inches of vacuum even on a very tight, well maintained tubing system. This statement also emphasizes the importance of managing leaks in a vacuum tubing system. Every leak adds additional air to the system making it harder for the vacuum pump to achieve and maintain high vacuum. The amount of air moved out of a system is measured in Cubic Feet per Minute (CFM). It is important to be able to differentiate between Inches of Vacuum and CFM. To successfully raise your vacuum level, you have to be able to remove the air from your tubing system. Once the air is removed, your vacuum level will increase unless you are letting air in through leaks.
Now let’s look at what happens inside a maple tubing line. A conventional vacuum pump is designed to move air not liquid. This means that a vacuum pump is pulling air out of the system while the trees and the leaks are adding air into the system. A properly sized vacuum pump with a proper CFM rating will be capable of removing air faster that it is introduced. The only thing that will slow that process is line size. If your line diameter is to small, the air movement will be restricted requiring more time for the pump to clear the air from the lines. This is commonly referred to as line loss. The smaller the line, the higher the line loss and the longer it will take to re-establish your peak vacuum level. That is why tubing design and pump size are so important in a conventional vacuum system. It is also very important to note that in a vacuum system, liquid does not need to be present to create a high vacuum. The movement of sap is secondary. As the vacuum level builds it creates a siphon that pulls the sap along with the air. In fact, when we look at the space inside a cross section of tubing we should strive to maintain a ratio of 60% air and 40% liquid. If the liquid level increases or is uneven (wavy), then the air movement will be restricted and the inches of vacuum will drop.
Let’s look at some other alternatives to move sap through a tubing system. One of the more popular alternatives to conventional vacuum is the diaphragm pump. Let’s look at what happens with a diaphragm pump. Diaphragm pumps are water pumps that unlike vacuum pumps are designed to move liquid – not air. Because they move water and not air, their capability of creating CFM is minimal at best. Manufacturers tell us that these pumps are capable of creating 20 plus inches of vacuum. How do you create a vacuum with these pumps when their ability to move air measured in cubic feet per minute is limited? In a sugar bush, your lines are hopefully sloped toward your tank and gravity allows sap to flow toward the pump. Once the pump picks up the sap on the intake side, it then accelerates the flow in the line. The pump simultaneously pushes the sap under pressure through the outlet. Because the pump is pulling hard on the sap and pushing it through the outlet, it creates a solid column of sap. As this column of sap moves down the line, the air and liquid combines thereby creating a negative pressure on the backside of the column. This negative pressure can be measures with a vacuum gauge. This continues until the sap flow slows down. As the sap flow slows the vacuum level begins to drop. Once the flow is terminated, the pump can no longer push sap through the outlet, and the negative pressure will ultimately disappear. If you run the pump without liquid, you risk damaging the pump. The biggest thing to remember is that a $200.00 diaphragm pump will not remove air from the system by itself. It has to move liquid to create a negative pressure on the backside of a column of sap. I know the above statements will create controversy from those that are using diaphragm pumps successfully. There are ways to tweak a system to create increased vacuum during low flows but the ultimate end is reduced or no vacuum. The other thing to keep in mind, if you want to be successful with a diaphragm pump, is to keep your tubing system free of leaks. Leaks will result in poor pump performance. Also protect you pump from freezing and ice in the lines. Ice can damage diaphragms. Diaphragm pumps are a good choice in small operations where an increased level of vacuum during a good run is better than no vacuum at all. But diaphragm pumps were never intended to a replace a conventional vacuum system and they never will.
I got up this morning (January 12, 2017) and it was 60 degrees! All I could think of was that a lot of my friends who make maple syrup saw the same thing I did and headed straight to the sugarhouse to find their drills. To say the least, 60 degrees in early January is unusually warm and the recent weather pattern has everyone scratching their heads. The decision of when to tap is one of the most important decisions you will make in any given year – hear are my thoughts on the subject.
First a little science! To quote New York Maple Specialist Steve Childs, we need to know “how does sap happen.” Sap flow is the result of sap rising and falling through the tree’s vascular system known as sapwood. Sap flows to provide nutrients to all of the vegetative growth above ground. Sap flows from the roots to the very tips of branches nourishing the buds that will develop into leaves. This process is on a phenological clock that limits the amount of time that we have to intercept a very small portion of that sap to convert into maple syrup. Once the buds emerge or “break”, sap is no longer usable for syrup production. Sap rises because of fluctuation in spring temperatures that we call the freeze-thaw cycle. As a tree freezes, a suction draws nutrients and water from the ground and through the roots. Once the temperature rises above 32 degrees Fahrenheit, gases begin to form inside the tree which then pushes the sap through the sapwood all the way into the very tops of the branches. Considerable pressure is produced in the process. In fact, pressures have been measured at 40 psi (pounds per square inch). When you drill a hole in the tree sap leaks out into a bucket and continues until the tree quits pushing sap or it freezes again. We can increase that flow by applying vacuum to the tap with a vacuum pump and tubing. If temperatures stay warm, sap flow will gradually decline; however, sap may flow up to 72 hours without the repeat of the freeze-thaw cycle. Without freezing, the sap level in the tree drops below the taphole and flow stops. Once the temperatures drop below freezing, the whole cycle starts again. This is a very simple explanation of a very complex process.
What else may stop sap from flowing? Once a taphole is drilled into a tree, the maple season clock starts to run. Using buckets and open tapholes, that window of opportunity is around 4 weeks before the taphole starts to heal up and sap flow diminishes. This healing is the result of the taphole being exposed to air and from the growth of bacteria in and around the hole. Air dries out the taphole and supplies oxygen to bacteria that coat the hole with slime eventually sealing off the exposed sap wood – similar to what happens when you get a cut. Blood flows for a while but eventually it coagulates and the bleeding stops. A vacuum tubing system is different in that the taphole is not exposed directly to the outside air and sap is kept flowing under vacuum for a longer period of time. If operated correctly, the taphole will be kept free of bacteria for most of the season. This can be accomplished two ways. First, you can keep the vacuum running continuously whenever the air temperature is above freezing. This keeps the sap moving, keeps the lines clear, and keeps the taphole cool. Producers have found that they can gather enough sap during extended warm periods to make enough syrup to pay for the cost of running the pumps during that period of time. The other method is to us a vacuum system with check valves to prevent bacteria-laden sap from the lines being pulled back in the tree. A tree will draw sap from the lines just like a hose will siphon water from a tank when you turn the tap off. The sap, because it has been exposed to the tubing, has some amount of bacterial contamination – however slight – and will speed healing of the taphole if drawn back to the tree. Check valves close when vacuum is released, and these simple devices seal off the tapholes from sap backflow.
Now to answer the question – “Should I tap during an early warm spell?” My suggestion is first to obtain all the information from a variety of sources that you can about upcoming weather patterns. Next, consider your system. If you are a small producer or a backyard producer looking for the ideal 30 day window, January is most likely too early to tap. Your taps may dry out and you may miss some of the really good runs in late February and March. You could re-tap but that is hard on the tree and is never recommended. The best approach is to watch the weather and be ready to get those good runs in February and March. For those of us who have vacuum tubing. We can stretch the season with taphole sanitation techniques. Watch the weather and tap when the opportunity arises. You may get some very good early runs. If you are going to tap now make sure you change out last year’s spouts and/or use check valves. You have to create a closed system at the tree to prevent taphole healing. If you have enough taps, consider tapping the side of the woods that runs early now and then tapping the later running sections a bit later on the calendar, effectively spreading your season. The best you can realistically hope for is two months before your taps start to shut down. I have personally kept my system flowing from the 10th of February to the 10th of April with the use of check valves and continuous vacuum operation. No matter what you decide to do, it is a gamble. Here is hoping your decision pays off!
The season has come to an end and now you are faced with the arduous task of cleaning up you maple operation. Where do you start and what do you use? For most equipment, the answer is simple – lots of hot water and elbow grease. A good place to start is with the tanks that hold both sap and syrup. Most are stainless steel and are easy to clean with a pressure washer. We found that a tank washing nozzle that fits your pressure washer is a valuable tool. The specially-designed nozzles enable you to spray to the side and reach areas that a standard spray tip cannot reach. There is no substitute for stainless steel equipment if you can afford it.
Plastic totes and poly tanks have become popular because they are relatively inexpensive but they are harder to clean. Plastic totes, while affordable, may only last about two or three seasons if you get off your cleaning schedule. It does not take long for the plastic to become so contaminated with bacterial spores that you have to discard and replace. However, if you keep poly tanks cleaned they will last for years. Another simple tip is to clean as soon after the season ends as possible. Allowing totes and tanks to sit dormant allows bacteria to build and grow making cleaning more difficult.
Your evaporator needs to be sugared off and flushed out as soon as possible. I often flush the pans with clean water and then refill them with permeate from the RO and let them soak. If permeate is not available, use water. I will drain and refill the pans with clean water and then add the proper amount of pan cleaner following label directions. Once the pan cleaner has done its job, I drain the pans and use a high pressure washer to finish the job. Do the process correctly and your pans will look brand new. Make sure all your float boxes are clean, replace gaskets if needed. Soak your auto draw off temperature probe and your hydrometer in a 5% vinegar solution to remove any residues or films. The thermocouple in the auto draw off probe works best when there is no niter on the probe. Clean your filter press thoroughly and lubricate parts with a food grade lubricant. It is good practice to remove all extra filters from your sugarhouse and store them in your house, somewhere dry and rodent-free. If you use a filter tank, you will need to clean filters and make sure they are completely dry before story to ensure no mold will develop over the off-season. Any filters with problems, even minor, should be discarded, and you should purchase new inventory for the next season.
Reverse osmosis units (RO) should be soap washed and thoroughly rinsed immediately after the last time you use them. Make sure all of the permeate is drained out. Once you break down the RO, return your membranes to the storage vessels with a cup of permeate in each one. Once everything is clean, you should send the membranes in to your dealer for cleaning and testing. There is nothing worse than starting a season with a bad membrane that is passing sugar. Make sure your high pressure pump and your feed pump are free and fully drained. Inspect the membrane housings and get them as dry as possible. Many times with the recirculating motors and pumps on the bottom of the membrane towers, dampness can cause the pump shafts to seize and seals to deteriorate. Because evaporators and ROs require the use of chemicals that are incompatible – phosphoric acid and basic soap – keep them separate and out of reach of children. Be careful when you mix pan cleaner and always follow the directions on the label.
The most controversial portion of a maple system to clean is most certainly the tubing. It seems everyone has his or her own way of dealing with the miles of tubing stretching through the woods. I have cleaned tubing just about every way possible over the years. We have sucked water, pumped water and air, water only, air and tubing cleaner, and just plain did not clean at all. In my experience, using water and air worked well until we tried to pump up too steep of slope and had a blowout that may have had enough force to launch a satellite. Sucking water through the lines left a lot of liquid in the lines that eventually turned to green snot. The method we now use seems to work. We pull taps with the vacuum, nip off each old spout, and immediately use a Stars Company (out of Quebec) line plug to seal the drop line and maintain vacuum on the system. Done properly, the sap in the lateral line will not suck back into the drop line. We then use a paint marker to mark the old tap hole which greatly speeds up next season’s tapping process. Once all of the taps are out, we back flush the mainlines with clean water. Next we close all of the main lines and open the end of each lateral opening long enough to pull air through the lines and keep vacuum on the system. Doing this should remove 80% of the liquid from the lateral and main lines. At this stage, we successively open the ends of each main line and let air in with the vacuum on. Once the vacuum on the entire system drops to zero shut off the pump. At some point before the next season, we then install new spouts on all the drops and let the lines air out completely. This method may seem excessive but it does work. We have a small amount of green sap at the start of the season, but nothing we could not easily filter and could possibly have been avoided by flushing the system again before the season.
A word of caution when it comes to using tubing cleaners. They have to be completely flushed from the lines before the next season. Never use Isopropyl alcohol – it is illegal in the United States. Also be aware that some cleaners attract Mr. Bushy Tail and his friends – never a good thing for tubing operators.
Once your system is cleaned, bring in all releasers and clean and sanitize them thoroughly. They are made of PVC which makes a good home for bacteria. Go over the mechanism and use lubricant provided by the manufacture to lubricate all of moving parts. The last task is to care for your vacuum and transfer pumps. Change the oil or drain out the water on liquid ring pumps. On the new rotary claw pumps change the oil and fog the pump with a pump oil. You need to make sure rust does not build up. The same is true for rotary vane pumps which are more maintenance-free but putting some oil on the vanes never hurts. All gasoline motors should be drained and the gasoline replaced with SeaFoam or a similar product. Never leave gas with ethanol in the tank. Drain the crank case oil and replace it with fresh motor oil and you will be ready to go for next season. Lastly, make sure you transfer pumps are drained and stored somewhere that will not fall below freezing.