mainline question

[philkasza]

O.K. this has probably been asked alot on here on how to size the mains. Is it true that if the mainline has a dip in it and gets full of sap then uphill from there will have way less vac? If thats the case, would it be good on basically flat ground to run the mains a little steeper and put a few sap ladders in?
Thanks Sam

[maple flats]

Do what you must but vac across a flat is very poor. Each choice uses vac. You must either get more elevation or run a sap ladder. A sap ladder requires more CFM than without one. Just make sure you have a big enough pump.

[Brent]

Another reason to keep it flat and descending wherever possible is a solid frozen line wont transfer anything. No sap. No vacuum. No nothing.

[PATheron]

Flat ground tapping is really hard. I struggle with it here and there too. Ive had some ladders and I think they work allright but another thing you can do is get pitch on the mainline even if you have to go way high at one end and just invert the laterals and let them run up hill. Its not optimum but itll work pretty good. The mainlines have to have pitch and thats just all there is to it. Itll be better to have the laterals run up hill by far than mainlines that slug. Once they start slugging your basically running a gravity system. Its an option anyway. Theron

[jim finen]

Running on a flat plane is not good no mater where you are. If the main fills up "in a dip" you will loose vac %. I feel the biggest bang for your buck in your case is sap ladders. You want that at least the 2% slope. If you put ladders in just make sure that you dont have them one after another on the same run of main line, each one will decrease the vac on that section after the the ladder.

[Brent]

Running on a flat plane is not good no mater where you are. If the main fills up "in a dip" you will loose vac %. I feel the biggest bang for your buck in your case is sap ladders. You want that at least the 2% slope. If you put ladders in just make sure that you dont have them one after another on the same run of main line, each one will decrease the vac on that section after the the ladder.

I've seen this comment many times and still have trouble with it. If a line fills with sap at a low point, sap will build up on both sides of the low point. The stuff up the line will build up and push the "pooled" stuff down a bit, until the point that it gets over the hump and flows towards the releaser. I'll bet if you left a low point intentionally, and put T's in with vac gauges above and below the low point, that the vacuum will be virtually the same. The vacuum isn't going anywhere or being used. It has to transfer to the other side of the low point ..... doesn't it ?

[danno]

Brent - I agree to a degree. We all strive for constant slope, but sometimes stuff happens. What I have noticed - sap through a flat mainline with a dip will still transfer pretty well on vac, not so much with no vac. I've also noticed my vac guages up in the push stay pretty constant, even as sap is surging through the lines - and I don't have a dry line. I have figured I am at the point of needing a dry line - when the sap is really flowing, I'm get 21"-22" of vac up in the bush, when it's not running that well, 25"-26" in the bush.

[Brent]

I have to say that I have not met anyone (not that I've met many other sugarmakers ) that has put in a dry line that did not a least "think"
they were getting better runs. I even hung some wire myself a couple weeks ago to do it too. I have not yet seen a Dr. Tim style serious study on wet / dry systems. If there's one out there I'd like to find it. I also have some suspicion that this was an empirical conclusion. This is what I think happened when the first evaporators were built with air over fire. A formula came out that 80% over and 20% under was the way to go, and that nozzles should be 1/4 to 3/8" diameter. No mention ever made about air pressure, having tested smaller or much larger nozzles. Anyway it seems perfectly logical to me at least, that when we get a big sap flow, the vac will go down. There is only so much energy being generated by your pump and if the system gets more sap out of the trees, more work is being done. You can do work or you can store it. By store it I mean create higher levels of vac that have the potential to do the work ... up to the max vac level that your pump will produce of course. Dragging sap along a level pipeline is doing work too, so a sloping pipeline will do a lot of work under gravity, that the pump will not have to do. So a long flat lateral line will "eat" up a lot of the pumps energy and reduce vac at the tap, but a dip in the mainline causing problems, I don't think so because the sap that keeps filling the 'up' side will push the sap in the dip further down the line.

Oh ... just while I was typing this I thought of a reason to punch a big hole in the idea ... we don't just suck sap. We've got air from leaks and wood gas from inside the tree. That will have to be sucked down the dip and lift / push the sap in the dip up the other side and then down the line. That means work ... or lost work from the vac pump ... or loss of vac. Hmmm. A wet / dry system would never have this problem would it ? More head scratching needed.

[maplwrks]

You guys keep talking like a dip, or low spot is exceptable.....You should never have a dip or low spot in a main line. Your vacuum will be greatly decreased if you have a dip. I know that when I get a real tight system going in the springm my ladders don't work all that well, I usually need to introduce some air to the line. When everything is tight and running down hill, the sap runs all the way to the releaser.