? on natural vacum setup

[chanced21]

Does the collection tank also need to be sealed tite? thanks

[500592]

No it should not

[farmall h]

Absolutely not...do not submerge the tubing into the sap either.

[DrTimPerkins]

So with all the questions lately about "natural" vacuum, it is important for people to keep in mind that "natural" vacuum does not get you the same results as pumped vacuum. What you're doing in this case is attempting to max out the capacity of your 5/16" lines across a drop in elevation, thereby creating a partial vacuum caused by the weight of the sap running downhill WHEN THE SAP IS RUNNING. Natural vacuum is not a good substitute for pumped vacuum. Why?

1. When you have the best natural vacuum, the 5/16" lines are full all the time. This can impede the flow of sap to some degree -- the lines are full, so squeezing in more sap causes pressure, which offsets the vacuum to some degree. The number of taps you want on the lateral line depends upon a bunch of things, there are no hard and fast rules, and what works well for one person one day under certain flow conditions might not be the best for the next person on the next day.
2. If the sap doesn't start running, is barely running, or stops running, you don't have ANY natural vacuum at all. It's kind of like a ball on top of the hill. Unless you have something to get the ball rolling down the hill, it just sits there and does nothing (the result being you get no natural vacuum). It isn't until the sap starts to run and build up in the line to some degree that you may begin to build up some natural vacuum.

Natural vacuum, like pumped vacuum, requires a really tight system. No vents, no leaks, no squirrel chews here and there. TIGHT. Otherwise, it doesn't work.

In my mind, natural vacuum on a 5/16" line is similar to sap ladders. If you have to use it to solve some particular problem or because of your specific circumstances, then OK....but there may be other ways to do it that'll give better results, and you give up something when you do use them. Don't expect it to do miracles though.

[chanced21]

only have a small operation cant afford a vucum setup yet thats y I asked about nat vacum thanks.

[Beweller]

Natural vacuum requires a very tight system and small diameter tubing.

The small diameter tubing reduces the tendency of air bubbles to rise up in the tubing against the downward flow of sap ("slip". If the slip velocity exceeds the sap velocity, no vacuum will be produced.) The small diameter also reduces the tendency of the tubing to drain (empty from the bottom up) when sap flow stops or falls to a low value.

If there is no air leak and the tubing is too small to allow drainage, the maximum possible vacuum is limited by the fall and occurs at near zero sap flow. Increasing the sap velocity (small tubing, more taps) causes friction pressure loss which subtracts from the vacuum. However, increasing the sap velocity permits the pumping of air from the system and reduces the impact of leaks. The presence of air leakage reduces the vacuum obtainable from a given height drop. Leakage rates approximating the rule-of-thumb 1 cfm per 100 taps are not compatible with natural vacuum.

For the ideal case, with leakage but negligible friction loss and slip, the vacuum produced can be calculated. In the optimum system the tubing diameter is chosen to balance the friction loss against the gain from better pumping characteristics and lower slip. For cases where the sap flow is too large for the maximum tubing diameter compatible with friction, slip, and drainage, multiple small tubes can be used.

If all else is favorable except drainage, a slight vertical rise at the end of the tube or a diameter reduction for the last few inches will prevent drainage. If there is any air leakage, the tubing will eventually empty and all vacuum lost.

With no or very small leakage, vacuum may be retained for some period after sap flow stops. The loss occurs more rapidly for small diameter tubing. If leakage is reduced to very small values, "tree gas" will become a limiting factor. Published data seems to be absent.

Note that "natural vacuum" is a "sap ladder" with the flow reversed.