Gravity Releaser?

[Russ]

Hmmm... we have a few months to ponder that. We tested it under vacuum and it seemed to pump ok.

[tmccrumm]

I investigated this type of system 20 years ago, problem is, as the column of sap gets higher in the tube, all your vacuum energy is being used to hold up the column of sap, and very little vacuum gets to the trees, esp. if you have a pinhole ther to insert air.

[ryebrye]

... This is a very old thread, I know, but I'm curious if anything has been tried with this in the past 8 years or so.

(I also disagree with the last post - the vacuum pump doesn't expend energy to lift a column of sap, it removes air and atmospheric pressure is what lifts the sap.)

I have been toying around with the idea of trying out this kind of a releaser.

I have more than 30 feet of vertical drop from my last tap to my collection point, so I was thinking about setting up something with a big column of 3/4" mainline 30+ feet with a vacuum line at the top of it, and at the bottom of that column I'd have a flapper for a mechanical releaser. When the pump first turns on, atmospheric pressure would keep the flapper closed. When the force of the column of sap above it plus the sap coming down the line is greater than atmospheric pressure, it would open the flap a bit and let sap pour out until the atmospheric pressure overcame it again and shut it.

There may be a big fluctuation in vacuum level when this happens - especially if it opens enough to dump the whole sap column... But I won't know until I try it. (But if anyone else has tried it I'm all ears)

I don't really _need_ much vacuum in a mainline as I was pegging vacuum gauges with 28+" on 3/16 last year, so even if this is a total failure I wouldnt miss out on much by just bypassing it entirely and going with just gravity.

... Any thoughts?

[red maples]

this thread is from 2006. So looking at the past threads they do make Stainless sump pumps for the "electric" releasers.

But anyway I am trying to see why your having a problem. OK so trying to understand, basicially its laid out like this:

vac. pump......releaser collection tank..... 30 ft verticle rise.... first tap going out? is this correct? if so then are you getting sap stuck in the line as it comes down the line over the 30 ft drop? or do you need it to lift up 30 ft? I will read it again. See if I can understand!!??

[ryebrye]

this thread is from 2006. So looking at the past threads they do make Stainless sump pumps for the "electric" releasers.

But anyway I am trying to see why your having a problem. OK so trying to understand, basicially its laid out like this:

vac. pump......releaser collection tank..... 30 ft verticle rise.... first tap going out? is this correct? if so then are you getting sap stuck in the line as it comes down the line over the 30 ft drop? or do you need it to lift up 30 ft? I will read it again. See if I can understand!!??

The idea is that you*might be able to achieve high vacuum without having to have a normal vacuum releaser if you can leverage gravity to help you maintain vacuum in the system and still get sap out of it.

Here'a a really rough diagram of how it might look:

https://www.evernote.com/shard/s163/...a01b1a5c8cafc3

gravity_vacuum.jpg

I don't think you would need a submersible pump at all, gravity should cause sap to gather down the line and once there is enough there to overcome the force that atmospheric pressure is putting on it to cause it to rise up in the air you would have more force inside the tubing pushing against the flap then you had outside the tubing holding the flap closed, so the flap would open a small amount and sap would flow out but air shouldn't (or might not?) flow in.

[red maples]

I honestly don't see how thats possible. here is a perfect example fill a shop vac full of water just before the float shuts off the vacuum now loosen the cap wiht the vac running reguardless of the weight of the water on the cap it will still suck air and not allow the water to escape and if some does escape it will not be enough to clear out the lines while sap is still coming down the line backing up into you vacuum pump line.

the other problems you will have is when the line starts to freeze and backs up into the top line going into the vacuum pump, whenever you introduce any air leaks into the system it creates a cold air gap that will cause freeze points where the air coming in because its not really a closed system the vacuum goes into the releaser and that is the stopping point for the sap. there is no way for the sap to get to the releaser. In theory it will work under perfect conditions and under a constant run but sap is never constant and can run differently even hour to hour, day to day, morning to night. to many variables in sap flow to keep it constant. you can try it but I would say it will only work sometimes. You can try it and I would love to hear how it comes out. When a mechanical releaser dumps the vacuum to the large container is broken or removed allowing the sap to move out then when the vacuum is reintroduced it closes up and continues you really don;t have a consistent way of breaking the vacuum enough for it to work. it would also effect the vacuum in the upper lines as well.

but thats my opinion if you can find the right ratio of weight to vacuum it might and mean might work but I really think its a fine line.

[ryebrye]

I honestly don't see how thats possible. here is a perfect example fill a shop vac full of water just before the float shuts off the vacuum now loosen the cap wiht the vac running reguardless of the weight of the water on the cap it will still suck air and not allow the water to escape and if some does escape it will not be enough to clear out the lines while sap is still coming down the line backing up into you vacuum pump line.

the other problems you will have is when the line starts to freeze and backs up into the top line going into the vacuum pump, whenever you introduce any air leaks into the system it creates a cold air gap that will cause freeze points where the air coming in because its not really a closed system the vacuum goes into the releaser and that is the stopping point for the sap. there is no way for the sap to get to the releaser. In theory it will work under perfect conditions and under a constant run but sap is never constant and can run differently even hour to hour, day to day, morning to night. to many variables in sap flow to keep it constant. you can try it but I would say it will only work sometimes. You can try it and I would love to hear how it comes out. When a mechanical releaser dumps the vacuum to the large container is broken or removed allowing the sap to move out then when the vacuum is reintroduced it closes up and continues you really don;t have a consistent way of breaking the vacuum enough for it to work. it would also effect the vacuum in the upper lines as well.

but thats my opinion if you can find the right ratio of weight to vacuum it might and mean might work but I really think its a fine line.

Yeah, I probably will try it primarily because I don't have much to lose. 90% of my taps will be getting vacuum from 3/16 and gravity

(I'm only going to have around 100 taps on this system this year)

To avoid sucking air I might have it drain into a trap of liquid and then into the tank so that it will have a little more pressure to overcome but when it does overcome it, it will be opening into liquid and not air...

This specific setup might not be the right way to do it, but it sounds like from this ancient thread that some people have done it in the past.

It will be fun to play around with at least.

[Super Sapper]

Why not just replace the tubing after the last tap with one or two runs of 3/16" run down to your collection tank?

[ryebrye]

Why not just replace the tubing after the last tap with one or two runs of 3/16" run down to your collection tank?

The latest thought I have is even simpler than what I was proposing before - I'm thinking of having the mainline under vacuum and on the downward slope, and then connecting the vacuum to the mainline high up on it (so it's higher than a 33 foot vertical rise for the sap to get to where the vacuum is being applied) and the force of the atmospheric pressure would cause the sap to back up in the line until enough sap collected that it would naturally drain out the bottom of the tubing. I could use a flapper on the bottom to help it maintain vacuum until it gets primed, or I could leave it open and use liquid to prime it - but in either case I don't think I'll need the straight vertical tubing I was thinking of earlier - the column of sap in the 3/4" mainline will keep it from sucking air, and the weight of the sap will push sap out the bottom of it in a steady stream.

I could have the mainline step down to a couple of 3/16 lines and it would probably work too, but it will be easier I think to just keep the 3/4 mainline going down the hill. The advantage of going down to a smaller tubing size would be that I would require less sap to prime it, but the disadvantage is that it would take longer to drain when I want to drain it before a hard freeze etc - it can take a long time to drain a 3/16 line. I don't expect to have any vacuum leaks in the mainline part, so even after I turn off the pump it would not have an open flow of air to flush out the 3/16 drain lines.

I'll think about it more though.

[Super Sapper]

I'm new at the tubing and will be using teh 3/16" for the first time this spring, but why would you want to drain it during a freeze? When it warms up to thaw the trees for the sap to run the tubing will thaw out also and the lines will be primed and you will have the vacuum right away. Using the 3/16" would also eliminate using a vacuum pump and releaser.