tubing

Out of the Woods Seminar

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The Out of the Woods series from Future Generations University in West Virginia hit an important topic several weeks ago, and the recording of “Two Seasons – Sanitation & Tubing“ is now available as a Recording.

The Talk Title “Two Seasons” is a play on this quote from Garnet Whetzel.

“There are only two seasons in a year.  Maple season and getting ready for maple season.”

I am quite sure that every single maple producer exists in this shared reality – the list of things to do is almost certainly greater than the amount of time you have for working on your list.  But there a few things on your annual list that you just cannot afford to ignore!  Keep in mind that a good chunk of this presentation assumes a 3/16th tubing system, but there are lots of great lessons to be learned from the talk.  Chiefly this, compelling evidence is shared on the benefits of sanitation (using the Krueger method with calcium hypochlorite) from a nice experiment out of the Mountain State.  Results from this experiment are followed by a great discussion on the bacteria, yeast, and mold challenges that maple producers face in the woods and in the sugarhouse.

Lake Erie Maple Expo RECAP

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Guest post by Carri Jagger, a MUCH appreciated piece of the Ohio State Maple puzzle!

On November 10th and 11th the Pennsylvania Maple Producers Association and the Northwestern FFA hosted the 2023 Lake Erie Maple Expo in Albion PA.  The Expo kicked off on Friday morning with a variety of sessions from beginning maple production, confections, and value-added products to tubing installation and vacuum.

I had the opportunity to attend the Advanced Tubing and Installation workshop on Friday that was taught by Steve Childs, retired maple specialist from Cornell University.  Steve taught us how to use the basal area angle gauge to estimate the potential number of taps per acre.

Steve also taught about evaluating your current maple tubing system to make sure that it is operating as efficiently as possible.  He shared the Cornell Maple Tubing and Vacuum System Notebook with the class.  You can view and print the notebook from the Cornell Maple Program Notebook Series Website.

On Saturday the conference resumed at the Albion High School where there were 4 concurrent sessions that covered 30 different topics.  I took the opportunity to attend the maple value-added track where I learned about using a glucose meter to check the invert sugar levels in maple syrup.  Determining invert sugar levels are important if you are planning on using your maple syrup for maple candy, sugar, cream and other confections.  If you would like to learn more about making maple confections check out the Cornell Maple Confections Notebook offered at the website above.

I also attended sessions about the distillation of maple and making beverages with maple.  Michigan State and Cornell are both doing extensive research about using late season maple and off flavor maple to distill into a marketable product.  Cornell has created recipes for several maple beverages and those can be found at the Cornell new product development site.

In addition to the conference there was also a trade show to visit with vendors about new and existing maple syrup equipment.  The conference was a great learning opportunity for both new and seasoned maple syrup producers.  The Lake Erie Maple Expo is always the second weekend in November and I encourage you to attend.

 

U-Kentucky/Ohio State Partnership Event

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Mixing Big 10 and SEC schools generally results in a brouhaha – not this time.  The University of Kentucky and Ohio State’s Maple team partnered to host a well-attended workshop last Monday evening just across the Ohio River in Boone County, Kentucky.  Strategically located to attract new and existing producers from southern Ohio and across Kentucky, 70 folks showed out for the event.  Beginning outdoors at the Boone County Nature Center, speakers covered topics ranging from maple identification to sustainable tapping practices and showcased demonstrations of different sap collection methods (buckets, bags, tubing) and a steaming boil on the local evaporator.


(Image Courtesy of University of Kentucky)

Along the way, attendees participated in a discussion of different grades and tastes of maple syrup profiled by a couple taste tests.  With a side-by-side comparison, many people were surprised just how different the same basic product – pure maple syrup – can taste.  That taste bud tease led us back to the Boone County Extension Center for a catered City BBQ meal and more presentations on value-added products, a couple short videos on sugarhouse design, and an excellent round of Q&A and conversations that lingered well after the event officially ended at 7 PM.

Many thanks to all who attended, and we look forward to continuing this partnership to expand the good news of maple across the southern tier!  To join up with your local community of maple producers, everyone should strongly consider joining their state association.  The Ohio Maple Producers Association annual event is Friday and Saturday, November 3-4th with Detailed Agenda here and a link to Register here.  The Kentucky Maple Syrup Association is also hosting their Maple School on Saturday, November 4th at the Berea Forestry Outreach Center and there is a button to join their ranks at the bottom of their webpage.

WV Maple Event Opportunity

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Southern Ohioans have a great opportunity to slide across the Ohio River to join a wonderful maple event scheduled for October 14th in Wayne, West Virginia.  Just across the water from Lawrence County, OH, our partners at Future Generations University and West Virginia University are putting on a workshop titled “Forest Management for Sap Production: Why You Should ‘Think Maple’ .”

Lunch is provided and the workshop goes from 9:00 AM to 4:30 PM and features sugarhouse and sugarbush tours at Tom’s Creek Maple.

Specific talk sessions are as follows:

  • Managing for sap production / Managing for timber production / or both!!
  • Sap collection systems
  • Managing a woodlot for sap production (hands-on and forestry tech talk heavy)
  • Integrating other forest farming activities into your sugaring operation
  • Forest health threats to maple
  • Technical resources through the OH/WV Maple Toolbox

Slots can be reserved by emailing syrup@future.edu.  Don’t miss out on a great learning opportunity to learn from syrupmakers in the far southern tier of what Ohio producers can expect to encounter in maple sugaring.

Tips for Working Volunteers into Your Maple Woods

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Whether you have children eager to help or new volunteers wanting to participate in your woods, you are undoubtedly familiar with the tug-of-war.  On one side, you want to get new hands engaged and interested.  On the other hand, if you want something to be done right the first time, do it yourself!  At the Ohio State Mansfield sugarbush, I am constantly balancing the need to get volunteers into the woods while still maintaining standards of quality and efficiency.  Here are a few tips that we use to make sure our volunteers are a help and not a hinderance.  Hopefully you can use one or more of these ideas to streamline your own efforts to reach this delicate balance.

Precision tappers are expensive, but precision tappers are also efficient and effective at controlling the single most important activity in your woods – tapping!  Precision tappers allow you to set the exact tapping depth and reliably expect that the grip points on the end of the device will result in a steady straight taphole each and every time.  While they are costly, our taphole consistently went through the roof when we employed these this sap season for the first time ever.  Precision tappers are probably not for the average producer, but if education and outreach is a central part of your mission, they may well be worth the cost.

An extra step for ensuring excellent tapping is to clearly mark your tapholes at season’s end with a dot of forestry paint.  If you are employing geometric tapping (e.g, over 3 inches-up 6 inches, over 3 inches-down 6 inches, …), then next year’s instructions simply become “find the [insert color of your choice] dot, space over, and tap.”

While we are on the subject of tapping, choose a sacrificial tree to train your tapping crew.  This double-trunked specimen is below our sap shed, has half its crown busted out, and has been tapped no fewer than 100 times in the past 5 years.  Our sacrificial tree is a classic “take one for the team” scenario.  Drilling a good taphole is only part of proper tapping.  How to properly set the spout is just as important, and in my experience, more apt for abuse and mistakes.  Repetition with back-and-forth feedback are minutes worth their weight in gold if volunteers or new help tap a significant portion of your woods.  Make your mistakes here – not on your production trees.

Lead by example in the sanitation department.  If your sap tank is filthy and scummed over, it’s hard to expect your help to take you seriously about sanitation in the rest of the woods.  If your tapping gear is mud-caked and filthy, it’s probably a bit hypocritical to expect your volunteer crew to keep your gear spotless and spit-shined.  Be diligent about sanitation, speak often about sanitation, and your help will take sanitation seriously as well.

Keep a volunteer’s job simple but always give them a roll of flagging tape to pinpoint potential issues they may run across.  If they see something suspect, have them tie up some flagging tape so you can check it out later.  Better yet, and particularly useful for keeping track of progress and directions in the woods, if you incorporate some numbering system into your main lines and laterals.  Below you’ll see an aluminum write-on tag that we tie on each lateral loop starting with main line number and ending with lateral line number.  So in this case, you’re looking at the 3rd lateral line on main line #1.  Navigation and giving directions becomes exponentially easier with this numbering system in place.

While we are talking about lateral loops, show your volunteers the rapid visual checks a producer has to ensure their woods are working properly.  As volunteers walk the woods, it’s easy to visually confirm that sap is traveling around the loops signaling a functioning system.  The same goes for sap flow through the drops into the laterals.  If the loops or drops are empty but the rest of the woods is running good, a strip of flagging tape might be warranted.

And lastly, do not realistically expect perfection.  I found this double spout tree untapped just last week.  It’s too bad we didn’t get this one tapped earlier, but if 1 big tree’s production is the price I pay to get someone excited about maple – that’s a price I suppose I’m willing to pay.

Fall Maple Assessment – Get Ready for Next Season

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The leaves have changed and have mostly fallen from the trees.  In some corners of Ohio, the first snow has already fallen.  For maple syrup producers, that means the push to get ready for a new season is upon us.  This is the best time of year to walk through your entire operation and systematically appraise your operation.  Now is the time to walk your sugarbush with a notebook in hand.  This assessment process allows you to locate the little things that make a big difference when the sap starts flowing.

Begin by looking at the most logical place first – your trees!  What condition are the trees in?  Are they healthy?  Did the June storms cause wind damage to the crowns?  The health of the trees will determine the number of taps per tree, and to some extent, the depth of your taphole.  If trees appear stressed, consider tapping a bit shallower (1.5 inches) rather than the full 1.75” or 2” depth.  It is not unusual to rest a tree for a season, allowing it to overcome obvious stressors.

Now reflect on your tubing system’s performance the very first year it was installed.   Compare that year to the way your system performed last year.  Have you noticed a drop-off in performance? It is easy to blame a poor season on the weather; in reality, the cause could be the age of your system and some neglected repairs.  For many producers, the first inclination is run out into the woods looking for squirrel chews and start repairing lines.  Do not get me wrong, that is important, but it is just one stage of a more holistic leak detection process.  The first order of business should be to inspect the lines for more systemic degradation and disrepair.  I hope that everyone is starting every season with all new spouts?!  However, your assessment should look deeper still.

When was the last time you changed the drops?  How long are the drops?  Are they long enough to allow you to reach around the tree?  Thirty-two inches is a good starting point for drop length in established systems.  What condition are your tees in?  Bad tees lead to micro leaks that sometimes are worse than squirrel chews because they are harder to locate and might be ignored an entire season.  What condition are your laterals?  Do they need to be replaced?  Are you noticing a mold buildup in the lines?  Are your lines patched together because of multiple repairs and damage?  When you replace laterals, it is a good time to look at the overall layout of the lateral system?  Count your taps on each lateral to determine if one is overloaded.  Remember, any given lateral should only be carrying 5 to 7 taps.  Also look at the slope of each lateral.  Is it running straight and tight and downhill for best performance?  What about your saddles, are they leaking?  Old saddles, just like old tees, need to be replaced on a regular basis – at least every 5 years.  Old saddles are often one of the major causes of leakage in maple tubing systems.

The next area of concern is the mainlines.  Ultraviolet light and wind damage are major causes of stress on mainlines.  Mainlines are good for 10 to 15 years, but eventually they must be replaced.  Yes, that is an expensive project!  However, the benefits outweigh the cost.  Installing new lines also allows you to remove damaged and unwanted trees during the repair.  Sugarbush stand improvement is important as it will improve the overall health and productivity of your sugarbush in the long-term.  Hazard trees, such as standing dead ash, should also be dealt with during a mainline replacement project.

It is easy to see how performing a pre-season assessment of your tubing system can be beneficial.  And that is just the tubing system!  After you walk your sugarbush – clipboard in hand – go back to the sugarhouse and develop an improvement plan. What must you buy?  In what quantity?  When will it arrive?  Are their supply chain delays?  Rank everything you have found in order of importance and start chipping away at your list – sap season will be here before you know it!

Vacuum Tubing Systems, An Update

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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.

Author: Les Ober, Geauga County OSU Extension

When the Season Comes to an End

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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.

Author: Les Ober, Geauga County OSU Extension

The Quest for High Vacuum Part 2

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When you bring up the subject of vacuum, one of producers’ first questions are “What size vacuum pump will I need to run my system?” They might add “Is the old rotary vane pump my granddad left in the barn good enough?” The question I ask them in return is “What vacuum level do you want to run today and into the future?”

As I stated in Part I, there are two ways to measure vacuum pump performance, inches of mercury (Hg) and CFMs (cubic feet per minute). Inches of Mercury (Hg) measure 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 15 given the maximum pressure possible is between 29 and 30. At 25″ Hg, approximately 85% of the air has been removed from the lines. CFM measures the amount of air being evacuated from the lines measured in cubic feet per minute. Pump ratings for CFM are assigned based on their ability to remove air, and this is largely determined by the size of the pump.

Two other factors come into play when comparing vacuum pumps. One is the horsepower rating. As the air is removed from an enclosed area, the molecules of air in that air become very sparse. The pump has to work harder as the air becomes thinner. The pump also has to overcome the force of the negative pressure inside that area. This requires more horsepower. A larger CFM rating does this faster but requires more horsepower. The other factor is pump speed. If you turn a pump faster, you will move more air and will increase the capacity. However, over speeding a pump can cause excessive wear on the pump.

So to answer the second question first, Granddad’s pump is not designed to produce anything over 15 inches of vacuum and that is not high vacuum by today’s standards. Most of the liquid ring, flood vacuum rotary claw and new-era rotary vane pumps are designed to run at vacuum levels up to 29 inches. Remember all of the pump ratings and their ability to increase vacuum level are done at the factory removing air from a sealed vessel. Based on this information, a performance curve can be developed. What makes this whole process more confusing is that many maple equipment companies are now listing there pump sizes by motor horsepower instead of by CFM capacity. As pointed out earlier, motor horsepower is only one factor determining pump capacity. When questioned about CFM, one dealer told me his pump will develop 11 CFM at 29 inches of vacuum. This has to be a specification taken off of a performance curve taken at the factory. The more important question is how likely is that pump to ever reach 29″ of vacuum in a working maple system? The fairest comparison should be made when the CFM is measured on a pump being run at 15 inches of vacuum. Otherwise, without having the performance curve data in hand for every pump you are considering, how can a customer make a fair comparison – quite simply, he or she can not.

So are the dealers wrong when they tell you that your pump will produce 29 inches vacuum? The answer to that question is both yes and no. As stated, most pumps are capable and have been tested to deliver 29 inches of vacuum. This is clearly shown on the pump performance curves. However, because the performance curves are standardized to barometric pressure at sea level, an adjustment for elevation above sea level needs to be made. For every 1000 feet of elevation you lose 1 inch of vacuum, this means the highest vacuum level achievable at an altitude of 2000 feet is around 28 inches depending on the barometric reading on any given day.

So what is going on when a producer tells you that his pump gauge mounted somewhere near the inlet of his pump is reading 28 inch of vacuum but out in the woods it is 18 inches or less? Is he wrong? Is the gauge broken? The answer to this question is no. Because line diameter restricts flow (termed line loss), a vacuum pump has the ability remove all of the air from the system within a short distance of the pump inlet. This phenomenon occurs because the pump can pull air out faster than the line can deliver it, thus creating a small area of high vacuum close to the pump, and the gauge at the pump measures only the vacuum in that area. But further out in the woods, the same is not necessarily – and in fact is unlikely to be – true. This is graphically displayed in the line loss charts used in the Cornell New York State Tubing and Vacuum System Notebook. A 60 CFM pump set at 15 Hg hooked to a 3“ line can maintain over 40 CFM out to 5000 feet. That same pump hooked to ¾” line is incapable of delivering 15 inches of vacuum at 2500 feet. This information is covered in a previous post titled “How Can I Get More Vacuum Where I Need It?”  Bottom line is that if the line diameter is too small, the pump’s capacity to remove air will be compromised, and the only vacuum reading that counts is the reading that is taken out in the woods at the last tap.

How do you determine the CFM capacity of the pump that will best fit in your operation? The New York State Tubing and Vacuum System Notebook (NSTVN) written at Cornell University by State Maple Specialist Steve Childs states that to go from 15 inches to 18 inches of vacuum you need to increase the CFM capacity of your system by 50%. Let’s start with the number of taps you have on the system. Let’s say you have 3000 taps. You know that for every 100 taps you need 1 CFM to keep up with the air and gases coming into the system primarily from the trees. This means that it would take at least a 30 CFM pump to remove the air that is coming into the system from the outside. The vacuum level under these conditions would be somewhere around 12 Hg. The NSVTN states that for every 1″ of vacuum you will lose 10% of the capacity of the pump. In order to increase that vacuum level to 18 inches or beyond, you would need to increase the pump size by at least 50%. That would now mean that you need a 45 CFM pump. This is only 18 inches of vacuum and you want to produce a high vacuum rate of at least 25 inches to achieve near optimal sap production. To get to 25 inches of vacuum, you still need to add another 7 inches of vacuum. Starting with a 45 CFM pump running at 18 inches of vacuum, using the 10% loss for every 1 Hg gain, you would end up with only 13.5 CFM (4.5 X 7 = 31.5 – 45 = 13.5 CFM). If upgraded to a 75 CFM pump, you would still only achieve 22.5 CFM (7.5 X 7 = 52.5 – 75 = 22.5) which still falls short of your goal. Not until you install a 100 CFM pump (which translates to 30 CFM; 10 X 7 = 70 – 100= 30) are you able to run your 3000 tap sugarbush at 25 inches of vacuum.

Now let’s look at the yield side, this time based on research done at University of VT’s Proctor Research Center. Proctor researchers set out to calculate yield up to 25 inches of vacuum. The study shows that sap yield doubles when vacuum is taken from 0 to 15 inches. From 0 to 15 inches, there was a 8 gal per tap increase, from 15 to 20 inches a 3 gal increase, and from 20 to 25 inches a 2.5 gallon increase. At 25 inches of vacuum a producer can cumulatively add 14 gallons of sap per tap. And at 20 inches vacuum, you have still added 11 gallons of sap. So what would happen if you settled for working at a lower vacuum level? If you backed down to 22 inches of vacuum, a 45 CFM pump would deliver 27 CFM – just short of the amount needed. Going up to a 60 CFM pump would deliver 36 CFM, adequate to run the woods with some reserve. You would raise your production by 12 gallons per tap per season. That is over 85% of your original goal of 14 gallons per tap.

You have now made all of the calculations and are beginning to understand the logic and principles behind setting up a vacuum tubing system. The one thing we did not mention was the importance of reserve vacuum. You also need to factor in the vacuum that is needed to run a manual releaser (at least 5 CFM) and any other features such as lifts or vacuum piston pumps. All of these chew up CFM. You do not want to be maxed out on CFM capacity when Mr. Bushy Tail shows up. Factor in another 3 – 5 CFMs in reserve vacuum and hope he does not bring his relatives. Your system needs capacity to recover from leaks and other unforeseen problems and it needs to do so as quickly as possible.

In my small world of maple production I am not comfortable with anything under 35 CFM. Here’s why! Our home woods only have 400 taps and the requirement to run those taps is only 4 CFM, but I have maxed out a 35 CFM pump. Here is how we did it. First, we have long mainlines because the woods is spread out. Second, most lines drain to a low point that is totally inaccessible to sap pickup so we use a lift to bring the sap forward to the releaser. Third, we then move the sap from the releaser tank to road via vacuum-operated piston pump. No one in their right mind would have put tubing in these woods, but we did and it works! We maintain 25 inches at the releaser, 22 inches of vacuum at the lift and 18 to 20 inches at the end of the mainlines. I will replace that pump with a bigger one someday, but in the meantime we are constantly looking for new and innovative ways to conserve vacuum and utilize what we have in the best way possible. Just like everyone else, we are spending countless hours looking for what Mr. Bushy Tail and his friends have done to our tubing. I cannot over emphasize the importance maintaining your entire system. There is simply no substitute.

Footnote: Many producers are successfully running their vacuum systems over 25″ Hg. They are successful because their system is properly designed and maintained.

Author: Les Ober, Geauga County OSU Extension

The Quest for High Vacuum in a Maple Tubing System (Part 1)

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The variety of vacuum pumps on today’s market is extensive. Although vacuum has become a mainstay in maple production, our utilization of vacuum pumps and equipment is small compared to their use in the broader industrialized world. Maple production is just on the tip of the iceberg when it comes to vacuum utilization. For this reason there is a lot of misunderstanding about the laws of physics (Quantium Mechanics) that govern the science of vacuum. Wikipedia defines the word vacuum as “void of matte.” The English word vacuum stems from the Latin vacuus which means “vacant.” The study of vacuum goes back to the Greek Age and the time of Aristotle. Several basic scientific principles apply when it comes to vacuum. Due to pressure exerted by the earth’s atmosphere (15 lbs per square inch) you can only achieve a maximum vacuum level of 29.92 inches of mercury (Hg). You actually can only achieve a vacuum level equal to the barometric pressure on any given day at any given location. Barometric pressure changes with the elevation above sea level and with the prevailing weather pattern. Another principle is how we measure vacuum. The level of vacuum is a negative measure (because you are creating a negative pressure inside of a vessel) and is read in inches of mercury (Hg). The rate of air being removed from a vessel by a vacuum pump is measured in cubic feet per minute (CFM) on an English measurement scale.

Even though it has become the Holy Grail in the maple industry, the term “High Vacuum” is largely misunderstood. High Vacuum or perfect vacuum exists only at 29.92 inches Hg. This is the highest level of vacuum achievable in our atmosphere and occurs only when every molecule of matter is removed from a vessel. This is extremely hard to achieve because once all of the air is removed there are still other gases that qualify as matter and are very difficult to remove. In fact the closest thing to a perfect vacuum only exists in outer space and we are not producing syrup on the moon.

Wikipedia states:

There are three levels of vacuum achievable with modern vacuum pumps. Low Vacuum (vacuum cleaners), Medium Vacuum (achieved with a single pump) and High Vacuum (achieved with multi-staged pumps and measured with an ion- gauge).

As you can see the vacuum we use falls in a range of somewhere between Low and Medium. And thankfully, the average maple producer does not live in the scientific world of vacuum, nor does he need to. The reality is that we are not dealing with a closed vessel but rather miles of tubing where the introduction of air occurs at every tap, fitting, and squirrel chew. The range that most maple producers should be comfortable with is around 20 to 27 inches of vacuum depending on their system and the pump they are using.

This is where the discussion and the debate begin. As I have stated in an earlier post, the producer must consider the entire system before he decides on the type and size of vacuum pump to use. Even though we are increasing the volume of sap being produced by increasing the level vacuum closer to 29.92 inches of Hg, we need to be more concerned about the ability of the whole system to remove air from the system efficiently. Rather than concentrating on achieving the maximum level of vacuum, we should be paying closer attention to the system’s ability to overcome leakage and everyday wear and tear.

There is a wide variety of vacuum pumps that can be used to apply vacuum to a maple tubing system. In fact, with the use of 3/16″ tubing, you may not even need a vacuum pump to achieve your vacuum goal. Most of the pumps used in the maple industry are adapted from some other type of use. The first pumps came from the dairy industry and were originally used to milk cows. These were rotary vane pumps that were designed to produce around 16 inches of vacuum. The vacuum was produced as the air trapped between the vanes held in an offset rotor was expelled to the outside via the exhaust. As vacuum level increases, heat builds up, and as a result, the system needs some kind of lubrication to absorb the heat. The pump is lubricated with oil that was contained in an oil reservoir. Once you went above 16 inches vacuum, the strain on the pump produced more heat that it was designed for. For that reason, oil coolers and oil-reclaimers were used to make pumps more efficient. Bearings need to be lubricated with a precise amount of oil to maintain function. When running above 20 inches Hg, if any of the above are neglected, you are headed for a Chernobyl-type melt down. There are commercial rotary vane pumps (running a flood vacuum) on the market that are capable of achieving up to 27″ of vacuum. One of the most popular pumps being used is the liquid ring pump. The liquid ring pump uses an impeller running in a ring of liquid producing close to 29 inches of vacuum. As the air is drawn in, the air becomes trapped in a compression chamber that is formed between the impeller veins and the liquid. The air is expelled to the outside as the liquid (oil or water) is recycled. These pumps achieve as close to 29 inches of vacuum as any pump on the market. The downside of this type of pump is that a water source is needed and that source needs to be kept above freezing.

One of the most recent pumps to come on the maple scene is the rotary claw pump. The rotary claw will produce 27 inches of vacuum, just under the level of a liquid ring pump. Rotary claw pumps are designed for continuous duty and require minimal in-season maintenance. The claw runs at a very close tolerance to the chamber and traps air in-between the claws and the chamber expelling it to the outside. A small amount of oil is used for lubrication. The downside is that these pumps are very expensive. They are designed to be run year round. Long layover periods may allow the pump to develop a rust layer inside to the pump resulting in excessive air. Because they run at a very close tolerance this may lead to early breakdowns. If you buy a rotary claw you need to fog the pump with anti-oxidation oil in the off season to prevent premature wear.

The last pump is the new-era rotary vane pumps that are designed to run continuously and to produce a vacuum of 29 inches. These appear to be highly efficient pumps. These pumps are similar in design to the older rotary vane pumps but have very close tolerances. They lubricate with oil.

So let’s rate the pumps on their ability to produce high vacuum from top to bottom. At the top is the liquid ring and the new-era rotary vane with the edge going to the liquid ring – especially one of the two-stage models on the market. These pumps consistently reach 27 to 29 inches of vacuum. Not far behind is the rotary claw which will produce 27 to 28 inches of vacuum. Next is the improved rotary vane with a flood system at 27 inches. At the bottom is Bessy’s favorite – the old style rotary vain used in milking systems. She liked it because it produced no more than 16 inches of vacuum. Any more and Bessy would send it across the room with one swift kick. No matter what you use, you will get more sap from your trees. Collecting maple sap with a vacuum system not only saves time and labor, but the vacuum will increase your sap yield somewhere between 50% and 150%. In the next post, I will cover things you need to consider before you hook your pump into the system.

Author: Les Ober, Geauga County OSU Extension