Sap ladder using star fittings

[mountain man maple]

Have a question on star sap ladders. Going to install a few hundred tap system this year and 100 taps will need lifted about 15-20' total. I have been told by some local producers that drops on mains that run through a ladder are more likely to pop out of tree due to backpressure until ladders thaw out. Has anyone else experienced this? My thoughts are if this is a common problem could turning the last star on the lower mainline horinzontal rather than upside down? I thought maybe only half of star would freeze this way and at least 2 5/16" risers would always be thawed and transfer air. Will this work or does it totally go against how sap ladders are able to work.

[BreezyHill]

We have never had a spout pop out in the 35+ years we have been running sap ladders.

The spinning of the star would not change the freeze factor of the line unless you had next to now sap in the system at time of freeze. Mine usually freeze with atleast a few feet in the risers.

[Maplewalnut]

I have never seen this either. Ladder freezes same as a lateral line, and then it thaws and then it freezes and then....

[BreezyHill]

I was thinking about this today while driving truck and had to reread your question.

For there to be back pressure your vacuum pump would not be able to pull anything thru the frozen riser...since risers will start to thaw before sap will run from the trees there is really no way for this to possibly happen.

Last season I spent several mornings watching the temp and the risers that were frozen to see at what temp they start to thaw. It was very surprising to see at 29 degrees the risers were starting to have tiny movement. This was in blue lines with full or nearly full sun and on the south side of the support tree. I was looking to see what temp the pumps should come on at...depends on the day...sunny 29 is good to get things moving, cloudy days, 31 was good to get things moving.

Not sure why your neighbors were having pop out issues???

Turning the riser would actually be bad for the function of the ladder. If the risers don't get equal flow then all the gases can go up one while the others are full of sap and flowing slower. Balancing the star by turning it to equalize the flow is important part of setting up the ladder.

[mountain man maple]

The ladders I will install will all get morning sun and will have sun on them most of the day. So I'm hoping I will have no issues. My system will run into a electric releaser. With 100 taps going through the ladder is a star ladder going to function better than a two pipe or single pipe ladder? Is my thinking right that a electric releaser also will help ladder work smoothly since I should have no backflow in lines.

[BreezyHill]

Is my thinking right that a electric releaser also will help ladder work smoothly since I should have no backflow in lines.

Yes. No back flow and an electric releaser adds to the CFM count of a vacuum system not reducing it, as does a mechanical releaser.

As for straight Pipe vs stars...I use both on several ladders. The stars are for the wet line that conducts the sap primarily and the dry line that primarily conducts vacuum are straight pipes.

I have used 1" and 3/4" straights and am very disappointed in their efficiency. The sap will flow around the air bubbles and back to the bottom with ease. I installed check vlaves to limit back flow and that helped but reduced my vacuum transferal rate. So I will be doing experiments on 1/2" risers.

I have also designed a PVC manifold system that has tested well and will try this on one of my ladders that gives me the most hair loss.

Most people forget about gravity when they are looking at a vacuum system. Gravity is the driving force of a ladder to fail. Gravity acts on the sap but not on the air. Vacuum works gest on the air and fairly well on the sap. The trick is to inject micro bubbles of air into the sap stream in the main so that these bubbles will be pulled rapidly up the riser. The bubble is lifting the sap up the riser. During the lift gravity is trying to pull the sap down. So as the sap rubs along the pipe some drops down the pipe wall creating a thin layer that is traveling backwards. This downward flow increases until the flow changes from a steady uniform flow to a surging or chugging flow that is very inefficient. The surges or waves of sap that go up the ladder makes the problem at the next ladder in a series even worse as you will have rapidly moving pools of sap hitting the ladder. This is where the manifold comes in. The objective is to allow the surges to equalize or even back to a steady flow thru the mainline to the next ladder or to the releaser. 996899699970

I attached pics of my releaser, one ladder with a single dryline riser, and a pic of my son working on our tallest ladder...18'. This is #3 in the 7 ladder series.

This is where the first manifold will be installed and I will have a lateral line attaching to bring in another 100 taps directly to the manifold. It would be easier to do it at the ground but I cant block the trail off and no need to put another 100 taps thru the ladder for no reason.

Back flow would be a deal breaker for a ladder. If you see this then you need to install a swing check valve in the mains. For best vacuum transfer they are advised for all connections of mains to a mechanical releaser. The pooling that is caused reduces vac transfer considerably. It would be less beneficial in a wet dry system but still will pay over time.