Shurflo Question, Air Lock ??

[TerryEspo]

Once again playing with my Shurflo, I still feel I am not getting best use out of my pump. Maybe its the sap not running, maybe its the pump getting an airlock.

Hopefully someone can explain what I am about to describe.

I have a manifold for my pump, one line goes directly into my pump and the other line is a gravity line for when the pump is off.
In the pics you will see a clear drain tube, that is my gravity drain line, the other line goes into my Shurflo.
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Now, when the pump is running for awhile, I see sap sitting around and the pump will not pull it. I can watch this go on for 5 minutes or more.
AIRLOCK ??
The is an air bubble right in front of the ice trap. If I shut pump off for a minute or two, then back on, pulls all sap in a lines, that I can see.

NOW,,,,The latest thing I tried while pump is running, is to open the clear tube gravity drain to let a TINY bit of air into front of system. I give a 1/4 turn (air-line), see the sap jump to life then close it gently to maybe 1/8 - 1/16 open. When I say airline open, I mean a very small tiny bit, just enough to see all sap start moving and pulsing along. When I do this, sap squirts out into collection barrel every 30 seconds or so, but never stops squirting. No more airlocks. It seems to never air-lock up when I let a tiny amount of air in from the clear tube gravity drain line.

This is not the same as venting is it ? With my "air-line" open sap never sits around, it is continually moving, all lines. I can pull a tap with my "air-line open" and I still have the sucking sound at the tap.

Can anyone explain what the heck is going on?

Please help.

Thanks.

Terry

[pennslytucky]

run a pickup tube from your gravity drain to the bottom of the tank so its sucking liquid instead of air. the pump pulls much harder on the tap line with a steady trickle of sap coming in regardless of where its coming from. if you put a gauge on the tap line you could run your bleed line like a throttle to get the max vac. all this extra pumping is making your pump work much harder tho. when the sap is running, i get more than enough from the trees to keep the pump busy so i took my return loop valve off and just leave it run on its own

[CampHamp]

Terry, I believe these pumps can generate about 25" when wet and 12" when dry (give or take). So when you are pulling a long stream of sap and the vacuum builds up to say 15" of vac and hits pure air... then it cannot pump further and stalls until your trees and leaks add sap and air to the tubing to get it back down to 12" where the pump can now pull air through.

By leaking air into the tubing, you are getting the vac down to 12" faster than the natural flow of sap would otherwise.

I found that I can maintain high vac at around 25" if I can setup my inlet so that sap trickles in at a constant rate. I can do that with about 5' of 1/2 mainline sloping gradually before the inlet and by having the pump angled up as well. The idea is you do not want sap to arrive in columns but rather have it flow in on the downhill.

[TerryEspo]

Thanks guys,

I will try both of what you said.
First I will raise my toolbox at the front to get some air and sap at the same time, I do have slope towards the intake right now. If that prevents what I call the AIRLOCK, then I will close off the airline completely.
If not, I will then suck a bit of sap instead of air from my "airline".

I can predict if sap is running good all this is not necessary, but good run days are rare for me this year, didn't have one yet.

Thanks for the advice guys.

Terry

[CampHamp]

Sounds good. Let us know how it goes...