Just a question

[georgelineman]

So I have 4 runs of 3/16 tubing with good elevation drop. On a average day the reading on my gauges are high with the normal flow of gas bubble sap gas bubble. But Monday when we had a gushing run of sap and the tubing was completely full of sap the readings were not as high. The average dope like me would think the more flow the more vacuum pull ???? It's not a problem just axe n. The problem is when I was in school and the teacher said you have to learn pie are square and I raised my hand and told her no ma'am pie is round cornbread are square. Well anyway what the answer is ? maybe Dr. Tim ???
Cornfuzzzzedd in Cornwall NY

George

[wmick]

Its about volume....
Your 3/16 lines full of falling gravity sap remove the atmospheric pressure from the tubing (vacuum) Perfect vacuum = 14.7 psi... but a 3/16" line under 14.7 psi is only capable of flowing a specific gpm of flow...
Once your trees produce enough sap to approach or equal this flow capacity limit of your lines...., head pressure from the trees will overcome and equalize the pressure in your lines... (Lowering the vacuum gauge)
Probably not happening all the time... But if you want to really optimize things, just add an additional gravity line, to move some more volume.
(Theoretically you could actually get to the point of having a positive gauge pressure (+psi) if trees were pushing more sap than the lines can handle. 100ft tree could create +40 psi)


Same would apply if you had a small vacuum pump... If the trees produce more sap than the pump is capable of moving, the vacuum disappears.

[georgelineman]

Thank You !
george

[DrTimPerkins]

How many taps on each line? How steep is the line (and is that for the whole distance, or do you cover a flat area at the end)?

[georgelineman]

All lines are down hill all the way except line 1. line #1 first 5 taps have a 1' drop (from end of the line to where it goes up hill is 20') then uphill 5' then down hill all the way to tank. Total run of 250' 24 taps 20' drop highest vac reading on gauge I have seen 15. Line#2 200' 15 taps 20' drop. 23 highest reading. Line #3 100' 12 taps 6' drop highest reading 8. Line 4 100' 13 taps 6ft drop highest reading 10. The highest readings all came a on an average flow day. But readings dropped on the one day the sap was gushing out and lines were completely full of sap. I do not have access to a transit so elevation is a guess. Someday after the season I will rig up a red neck transit and have a better idea of elevation. Like I said in a previous post its not a "problem" just wondering about the science of it. Its really cool to see sap going up hill! Thanks Dr. Perkins for all you do for the industry and even the little hobby guy like me.

George .

[DrTimPerkins]

How long has this tubing been installed and how are you cleaning (or replacing tees/unions)?

[georgelineman]

the 250' run is new this year. the others are all new spiels this year but tubing is 3 seasons old this year. Cleaning is well water and vinegar flushed 50/50 for at least 5 min. then 15 min. of just well water then left up till dry then put away in dry place till next season