Problems priming a March pump

[mexican]

G'Day all,

I'm having a problem priming my march pump and dunno exactly how to get around it.

My setupis as follows. The pump is mounted so the inlet is below the outlet to ensure that the pump initilly fills from the bottom to stop air pockets. That part appears to be working well. The input of the pump is connected to the ball valve on my kettle which is fitted with a copper pickup tube bent down into the bottom of the concave base. The pickup hose is covered with a large screen I made up that looks a little like a hopstopper.

When I open the ball valve on the kettle wort starts entering the input of the pump effectively priming it. I can then see wort starting to slowly fill the hose between the pump and kettle. The problem appears to be that an air pocket forms once the level in the hose matches the level of the bottom of the pickup tube. I can squeeze the hose to force a little more air back out through the pickup tube but I cannot get rid of all of the air from the hose. When the pump turns on I get crappy flowrates bacause of the air bubble in the hose.

Does anyone have any idea's as to what I can do to get rid of the air bubble ? I don't want to fit a second valve just to use to bleed the air from the hose.

thanks,

mexican

[jamilz]

A couple of random ideas.

1) After it is full, raise the pump up and let the air bubble pass through the pump.

2) When filling the pump, remove any restriction from the outlet side of the pump so it fills faster. Perhaps lower the outlet line. You'll get a better rush of wort and it should push the air out.

[mexican]

A couple of random ideas.

1) After it is full, raise the pump up and let the air bubble pass through the pump.

I might use that in the interim though I eventually want the pump permanently mounted on my brewstand. Trying to tip the whole brewstand over to get rid of an air bubble would look, well, kinda weird.

2) When filling the pump, remove any restriction from the outlet side of the pump so it fills faster. Perhaps lower the outlet line. You'll get a better rush of wort and it should push the air out.

I'll give that a go as well. I think some experiments with a kettle full of cold water is whats required here so I can try out a range of things in relative safety.

Thanks for the hints 'oh great spiritual leader of the brewing masses' !

mexican

[TB]

Hi Mex.

I have a couple of ideas to help too.

As Jamil said in 2. make sure the outlet hose is not shut off (at either the pump or at the receiving vessel). ie. if you outlet hose connects to a ball valve at the vessel make sure it's open. Or if the hose outlet is sitting below the liquid level at the end raise it so that air can vent from the pump and properly fill.

Another idea is (it may or may not work depending on how you design and use your brewery) to fill the pump lines with water before hooking it up to the mash tun. I designed my system so that I can prime the pump at any time by just flowing a bit of water through from my HLT. It will fill the inlet and outlet hoses by gravity as long as the air can vent.

I'm not exactly sure how you use your pump and the procedures you use, but I usually fill my MT with strike water first, open the outlet and let it run full tilt into the pump and hoses to prime. I sometimes let the pump run for a period to fill all the lines but as long as the inlet and pump housing are full it shouldn't matter. Anyway, by doing that before the grain is added you can vent any air in the line without resistance by the grain at the input and without risk of sticking your mash. Then I just don't disconnect the pump for the entire mash or transfer. Whether you can do this or not is dependent on your system but that's how I do it.

Finally, what happens when you turn on the pump? Usually if you have liquid in you inlet hose, in the pump housing, and at least some in the outlet hose when you turn on the pump it will push this liquid through and draw any air in the lines through as well. Maybe there is a bit too much resistance from the grain bed and you're getting slow flow which gives the liquid a change to get around the bubble rather than pushing it out.

Once the bubble is gone though, do you get good flow?

Cheers. TB

[Tom-O]

I just lower the outlet hose as close to ground as possible. This flushes the air right out.


If not, that damn bubble will stay there forever unless you vent it somehow. I used to crack open the hose on the pump suction until I was shown the "lower the outlet hose when starting the pump" trick.

[mexican]

Hi Mex.

Finally, what happens when you turn on the pump? Usually if you have liquid in you inlet hose, in the pump housing, and at least some in the outlet hose when you turn on the pump it will push this liquid through and draw any air in the lines through as well. Maybe there is a bit too much resistance from the grain bed and you're getting slow flow which gives the liquid a change to get around the bubble rather than pushing it out.

Once the bubble is gone though, do you get good flow?

Cheers. TB

The few times I've managed to get hte bubble out of the input line everything works well and I get great flow.

The problem appears to be that because the pickup tube goes back DOWN below the highest point in the tube there is a small area where an air bubble can sit quite happily. If my pickup tube were horizontal then the air bubble would be able to escape.

I just lower the outlet hose as close to ground as possible. This flushes the air right out.

If not, that damn bubble will stay there forever unless you vent it somehow. I used to crack open the hose on the pump suction until I was shown the "lower the outlet hose when starting the pump" trick.

It sounds like you are using the force of the wort filling the input side of the pump to force the air out in one shot.

I'll be doing some experiments over the weekend and will try out all of the ideas everyone has posted to see what will work in my situation.

Thanks for the info.

mexican

[Tom-O]

yeah, the difference in the elevation between the level in the pot, and the end of the outlet gives you a certain flowrate. Then you turn the pump on, it gives you a higher flowrate.

the two together (elevation + pump pressure) move the wort fast enough to suck through air bubbles.


usually pumps do not "air bind" if the velocity if over 2 feet/second. But with these tiny tubing diameters it may take a little more than that. the plastic seems to hold it by static electricity, or surface tension, or something..