By Les Ober, Geauga County OSU Extension
You have just bought a new vacuum pump and you have spent some time making sure that your vacuum lines are sized properly but for some reason one or two lines are just not preforming the way you want. Is there a solution to this problem? Yes there is! It is all about distributing the vacuum to where you want it.
If all of the vacuum lines are the same size and all of them run directly to the releaser all of the CFM’s for each line will be distributed equally across the system. If you have 4 1 inch lines coming to the releaser that is powered by a 60 CFM pump each line would receive 25% of the vacuum or 15 CFM. According to theory that would be enough vacuum to run 1500 taps on each line. However, based on previous articles in this blog you realize that due to line loss this is not entirely true but each line would receive 25 % of what is available. What happens when you have 1 1 ¼ line used in a wet dry system hooked to the releaser along with 3 1 inch single lines. This is where vacuum distribution comes in and the math starts.
Each pipe diameter has a cross section area
Knowing this will give you the cubic feet capacity per minute for the pipe.
It will also allow you to assign a percentage of a vacuum pipes capacity to each pipe.
Area of the Pipe
¾” .44 sq. inches 1 ½” 1.77 sq. inches
1.0” .78 sq. inches 2.0” 3.14 sq. inches
1 1/4 .1.23 sq. inches 3.0” 7.07 sq. inches
How do I determined what percentage of my vacuum is going to each line?
Let’s say in your woods you have 4 line, three 1 inch lines with 1/3 of my taps on them and one 11/4 over 1 inch Wet / Dry with 2/3 of the taps. Here is a simple formula determine vacuum
: For the 1 inch lines .78 + .78 + .78 = 2.34
For the 1 ¼ line = 1.23
.78 ÷ 3.57 = .22 or each 1 inch line receives 21 % of the CFMS
All together the 1 inch lines in this system are receiving 63% CFMS
That leaves the remaining 37 % (32CFM) capacity for the 1 1/4 line.
Now you have 2/3 of the taps on the 1 ¼ wet /dry line only receiving 1/3 of the CFM”s. You need to redistribute the CFM’s to the largest number of taps. To correct the problem you need to reduce the number of CFM’s going to the 3, 1 inch lines or you need to increase the size of the dry line on the wet dry system. If you apply the math using the above information you can obtain the most economical solution;
You could install a 2 inch line in place of the 1 ¼ this would apply 60% of the CFM’s to that line and 40 % to 3, 1 inch lines. You could also bring all three 1 inch lines together into a vacuum booster with a 1 ¼ outlet going to the releaser. What you end up with is two lines coming into the releaser of the same size, each with 50 % of the CFM’s. Remember the wet line does not count as a vacuum line; its only function is to transfer liquid. The only other considerations are to avoid line loss from the vacuum pump to the releaser by using a 2 or three inch line and to account for all the CFM’s used by releasers and other equipment on the system.
All of this information is available in more detail in the New York State Maple Tubing and Vacuum System Notebook from Cornell University, written by Stphen Childs, New York State Maple Specialist. To obtain a copy contact Cornell University, College of Agriculture and Life Sciences, Department of Natural Resources.