Air in recirc lines during mash cycle (HERMS)

[The Judge]

To start, I've had a look here and not found an answer (though it was hard trawling through 63 pages).

I've had a problem a couple of times during my mash cycle of getting air into my recirc lines - particularly between the MLT and the pump suction. I prime my pump and the cycle starts no worries. But after a short while, the grain bed starts to get a little bit foamy and I suspect the wort is draining to the pump suction with some gas bubbles carried through. I've checked my fittings on the suction side and there are no leaks to let air in, so I'm almost certain it's from the mild foaming of the mash.

Has anyone else experienced a similar issue on a mash cycle? Any solutions or suggestions would be useful, cheers.

 

[mofox1]

I've had that scenario when cleaning out the kettle or mash tun and had the return hose pointed at/near the the out port. It was basically bubbling near the port and the bubbles were being sucked in.

If it's happening during the mash, then that would indicate some helluva lot of channeling. Have you tried keeping a higher level of water above the grain bed, or returning onto some alfoil or equiv?

Which pump(s) are you using? I'm using the cheapish mag drive ones from keg king (~$70) and they draw in from the centre, and flows out at the top. I've found that if I tilt them with the "nose" down a little bit (ie - raise the back by a cm or two) it copes with a little bit of air being sucked in.

 

[Adr_0]

Pics? Drawing?

 

[The Judge]

I have this pump, which sounds similar to your Mofox.

Not sure how to keep a higher waterlevel in the MLT as I'd have to go above my 3L/kg that I like for my mash. Perhaps the answer lies in evenly distributing the returning wort across the grain bed, and not stirring as often as I do. I usually stir every 10 minutes in a 60 minute mash.

Perhaps the stirring is also forcing the tiny bubbles into the mash, and then they are sucked down.


Mofox, what's your return line into the MLT look like?

 

[Adr_0]

No, I would say that your answer lies in how your hoses are laid out around the pump. Any pics?

 

[Yob]

Don't stir.. It's likely causing the finer particulate to settle near/on the manifold, I use a sheet in my mt and I got this reaction if I stirred, it was clogging the sheet and causing it to pull air.

 

[mofox1]

I have this pump, which sounds similar to your Mofox.

Not sure how to keep a higher waterlevel in the MLT as I'd have to go above my 3L/kg that I like for my mash. Perhaps the answer lies in evenly distributing the returning wort across the grain bed, and not stirring as often as I do. I usually stir every 10 minutes in a 60 minute mash.

Perhaps the stirring is also forcing the tiny bubbles into the mash, and then they are sucked down.


Mofox, what's your return line into the MLT look like?

It doesn't, not set up for recirc at the moment. I only do it during fly sparging, and then it's just the end of the hose sitting on top some afoil.

Tiny bubbles shouldn't be a problem, they should be able to be pushed through. Are you trying to pump too hard (phrasing!) or are there loops or bits in the hose that would allow a larger bubble to collect before being pushed into the pump, causing it to lose suction?

 

[The Judge]

No pics which show the pump and piping set-up. I can take some next brewday and post them in this thread.

 

[The Judge]

My suction pipe is all negative gradient, but it's not close to vertical at all, as the elevation difference of my MLT outlet to the pump suction is only about 30cm. As said above, will post some pics after next brewday, and also will try (a) not stirring and (b) evenly distributing returning wort.

side note: Mofox I love all your Archer references

 

[mofox1]

Some people called me mildly obsessed... they're the ones being nice.

 

[TheWiggman]

I get this problem. Because of the suction of the pump, when my hose gets warm it forms a less-than-ideal seal at the outlet of the MT. Slight bit of flexibility in the silicone results in a veeeeeery minor ingress of air through this line. Gets worse at mash out. I have no idea of your setup but check the barb fitting there. If you have a screw clamp, it might not be applying equal pressure around the hose. If you don't have one (like me), this could be fixed with a clamp.

 

[Adr_0]

My suction pipe is all negative gradient, but it's not close to vertical at all, as the elevation difference of my MLT outlet to the pump suction is only about 30cm. As said above, will post some pics after next brewday, and also will try (a) not stirring and ( B) evenly distributing returning wort.

side note: Mofox I love all your Archer references

You should be able to stir your mash without introducing air pockets into your suction line. Or, your suction line should be plumbed such that any air can remove itself via the inlet rather than through the pump...

Long downhill runs are bad, unless they end in an open bucket. If they loop up again, it will seal off an air pocket; if it goes into the pump it will either go through the pump (bad) or if it is building up rapidly, it will sit along the entire length with the bottom of the air pocket at the pump (very bad).

Try to get a vertical drop from the MLT, and ideally a bit of a slope in your valve/weldless fitting back up into the MLT. It only has to be very slight, so you can do this by putting something under the opposite side of the MLT to put it on a very slight angle. On your MLT outlet valve, maybe put an elbow pointing right down and then put your hose onto this so that it comes off vertically.

A vertical drop from the MLT and then a long horizontal section (very very slight drop) is better than an even, say 30° drop.

Air bubbles can be dragged in or can be dissolved and come out of solution along the hose. This is particularly the case if you have a long length of hose (pressure drop) where the wort can no longer hold as much air in solution. So you need to be able to let the air "go back to where it came from", much like the evil boat people*

*the complete opposite of what I actually think

 

[The Judge]

If you have a screw clamp, it might not be applying equal pressure around the hose.

I do have a screw clamp there, but you're right, maybe it's not applying equal pressure around the silicon tube to seal it. It's a possibility, and I'll investigate it.

Try to get a vertical drop from the MLT, and ideally a bit of a slope in your valve/weldless fitting back up into the MLT. It only has to be very slight, so you can do this by putting something under the opposite side of the MLT to put it on a very slight angle. On your MLT outlet valve, maybe put an elbow pointing right down and then put your hose onto this so that it comes off vertically.

Cheers Adr, this is all good advice. I think I will mess with the plumbing on the suction side, as I've always suspected it's not ideal. A bit more head on the suction side would help anyway, and your advice on the gradient (trying to get a vertical section in there) seems logical. Basically I'll have to raise my MLT a teeny bit more and get a vertical drop from the outlet to the pump suction. Will report back any successes.

Cheers