Air extractor for diaphragm vacuum system

[wmick]

So I got thinking about the common problem that people have with the little diaphragm pumps getting air and dropping their vacuum levels until it gets another good drink....

I was out at my setup last night watching this scenario.... As the temperatures got colder and trees were shutting down the problem got worse... with liquid the vacuum level would jump up to 20+... but then an airlock would drop it down to about 10 inhg... and the low times were longer than the high times.
I do have a bypass line that helps, but just not 100%... and to turn up the bypass to the point of keeping the pump flooded, would negate the pumps capacity for the trees......

After a little Day-Dreaming, about a way to "Catch" the air, prior to the pump (keeping the pump full of liquid)....
I came up with this idea, attached... Some pipe, fittings and check-valve and cycle timer required...

What do you think?? Will it work?? Sap Air Extractor.JPG

[maple flats]

I believe you are trying to over think it. How do you have your re-circulation line? Do you have a needle valve in the line and does the line always move some sap? If yes, it is not over powering the pump. A little diaphragm pump (in fact any diaphragm pump) moves far more when the diaphragm is kept wet. Which pump do you have?

[wmick]

Its a little Chinese pump... https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1 . I've had a couple of them running for a couple or three years... on thermostat controls... They seem to work good... but nothing to compare it to... I know they are easy on batteries... I typically change out the battery every 24 hours... but had one running for about 48 hours and still pumping at the end of the season last year... I think the pump is doing its job... Not unusual to hear guys battling with air in the pump problems...

My bypass is a 3/16" tubing from the tote back to the inlet of the pump, with a needle valve and it does work.... but still pulsates the vacuum level. If I open the needle valve right open it pulsates less. but it seems like I am wasting the pumps capacity on re-circulation. and might not have the capacity to keep up the vacuum, if the Trees really get pumping good....
If I back it off to to a trickle.... the vacuum level does pulsate back and forth from good to poor.
I should mention that my bypass is going into a manifold... (bunch of 3/4" pipe "T"s glued together with hosebarbs for sap.. and my needle valve is plumbed into a T and a strainer in another which feeds the pump by hose)... Just thinking now..... I wonder if I "T"d my bypass needle into the hose, immediately before the pump (rather than to the manifold), maybe the trickle would feed the pump more consistently and avoid the pulsating?... I will try this.

FYI - I did build and install my "air catcher" last night.... but no cycle timer yet... The trees were pretty much shut down for the day, so it wasn't filling very fast to exhaust the air... but it was filling. Not good sap running weather for the next couple days, but hopefully will be able to play with it more, soon.

[DrTimPerkins]

Almost all pumps will "pulse" to some degree, it is just a matter of the frequency (number of cycles per sec or minute). Larger pumps have many cycles (gulps of air) per second, so there is essentially little pulsing. Diaphragm pumps have very low frequency (fewer strokes or gulps of air) per minute, so the pulsing is far more obvious. Although the pulsing is probably not great in terms of sanitation effects at the taphole, there is relatively little you can do about it with this style of pump. Diaphragm pumps are made to move liquid, not air. The CFM capability of diaphragm pumps is very low, and they quite intolerant of leaks. Most pumps used to generate vacuum in maple operations are made to move air, and don't tolerate liquid well. The tradeoff for this effectiveness is pretty much cost.

As Dave said, they also need to have the diaphragms wetted for best operation. The issue there is "how much?" When there is little sap flow, you want a good amount of recirculation. When the sap is running hard, you probably don't need any. Unfortunately, this must be done manually.

So, with all that...perhaps your idea will work (not really sure I understand it), perhaps not. If you try it, let us know how it turns out.

[maple flats]

Those are most likely single diaphragm pumps, the pulsing is normal, a single will be more obvious than a double but both will pulse. I would not worry about the pulsing. I think I'd set the needle valve so you can see a lite to medium flow and that should be wet enough for wetting the diaphragm.
Unfortunately I am trying to reason this out while my only 2 diaphragm pumps are very different from what you have. One is hooked to my permeate tank to feed my tankless water heater and the other is my air powered syrup pump on my filter press. I have never tried those little pumps for sap vacuum.
Going to my small diaphragm pump on my permeate tank, it does pull air, but slowly until it gets some water to the pump, then it pumps very well. Mine is a 3.1 gpm pump. The same thing on my syrup pump, it pulls very slow until it gets a little syrup, then it quickly starts to pump lots of syrup on open discharge. The key on both is the diaphragm works at it's peak only when the diaphragm is wet.
That being said I can usually figure most mechanical devises out, being an old farmer, old being the key word.

[wmick]

Pulsating is maybe not the word I should have used... Whats happening is the pump will run like it's dry for 30 seconds (10 inhg)... and then (when it gets a good enough gulp of liquid.) The vacuum spikes up to over 20 and it moves a lot of liquid for 30 seconds... Then it seems to run dry again for a bit... repeat, repeat...

If the trees are really producing well, the vacuum stays high for much longer periods of time or constantly... If the trees are running slow, it will run dry more often... Im basically looking for a way to stop it from running dry as often or at all (keeping my vacuum level high) ... Air catcher was a thought to remove air and leave liquid.... Moving the bypass closer to the pump inlet, might just cure it, as well... give it a constant drink, instead of it taking periodic "gulps" from the manifold??

I think the biggest difference between using it for vacuum in the bush vs pumping from tank to tank, is the air bubbles vs no air bubbles... Constantly getting some gas from the trees or around spiles or tiny leaks here and there.. This decreases when the sap is running and increases when sap slows down... Basically if trees are running slow, the pump has no problem emptying the mainline leaving just air to pump... The big downfall is that this is the time I would really like to keep a decent vacuum level. If transferring from tank to tank....its just liquid, once things get moving.

PS - The other purpose that the air catcher provides, by chance, is an unrestricted path for sap to go directly to the tank, bypassing the pump, if the trees want to flow before or after the pump is running, or it quits for some reason.
...I know that sap should be able to run through the pump in that direction on its own, when not running... but I found that there is quite a restriction there for some reason? The little swing gate check valve on the top of my catcher is very easy to open.

[maple flats]

With a properly adjusted bypass from the destination tank back to just before the pump, like 3-4" should correct that. I think the term you were looking for is surging, it surges, then runs dry, poor vacuum then surges again.

[Ultimatetreehugger]

I have found that if sap is backing up like that than the sap is settling before the pump. So I set mine up to have a smooth run coming in. This is my setup and it works excellent. https://youtu.be/MFBYqZFnRYg

[Super Sapper]

Make sure that the line coming into the pump has a good pitch to it. If it is fairly level you can get the surging you are talking about.

[wmick]

I have found that if sap is backing up like that than the sap is settling before the pump. So I set mine up to have a smooth run coming in. This is my setup and it works excellent. https://youtu.be/MFBYqZFnRYg

Thanks - I think your video may have pointed out my problem... (or a contributor anyway)... My mainline is lower than my pump.... Mainline ends a couple feet off the ground, and my pump is sitting on top of a tote....
Previous years I had all 3/16" tubing coming straight from the bush to my little manifold... (in hindsight, the 3/16" tubing would not allow sap and air to pool up) Unlike the 3/4" mainline that I ran this year.... with a 3/8" tubing running up 3 or 4 ft to the manifold and pump.
Watching your video, makes me think I should try moving my pump to the ground, under the outlet of my mainline. so it gets the trickle of sap, at the rate it arrives...