nate_e

Recipes 

At this point I've completed about 6 AG batches using fly-sparging with out too much drama. At this point my most memorable "learning experiences" have been about the effects of flow rate and stirring thicker mashes on efficiency. But as always I'm trying to improve my process and this part has me stumped.
In batch #6 and #4 I've had what I'd call a semi-stuck sparge. I'm using a 10gal. round rubbermaid cooler and a 12" SS false bottom (Northern Brewer's design) attached to the bulk head by 3/8" high-temp silicone tubing. I vorlauf about 5-6 quarts to clear things up and dial in a flow rate of ~1qt/min. The two times I've gotten this stuck sparge, the flow rate stays that way until I reach about ~2 gal of wort in the BK. At that point the flow rate begins to slow and I've noticed small bubbles climbing their way up the tubing from the BK to the ball valve on the MLT. Eventually the flow slows to a trickle. I opened up the valve to ~1/2, and flow started up again, but with a lot of grain material in suspension and at a higher rate than I wanted to sparge at. So both times I closed the valve, stirred the mash, let it settle and started to sparge again at ~1qt/min with no subsequent problems.
Has anyone experienced something similar?
A couple of things I've noticed is that in order to get flow going from the MLT in the first place, I have to open the valve pretty far in order to get the air out of the line. Once that happens I scale it back immediately to get my desired flow rate. Could this initial "burst" be contributing to a stuck grain bed later on?
I don't think it's a vacuum lock forming because stirring the mash has fixed the problem, but I can't be sure.
As I said, this has only happened twice but it seems to be a recurring problem. Any advice is welcome!

Misplaced_Canuck

Recipes 

Quite possibly. If you're only trying to get the air out of the line, pinch the line a few times and try to get rid of it that way. You can also use a small up-rise lower in the line to allow the wort to pool before it exits the line.

1qt/min = 1gal/4min = 15-gal/hour. That's a pretty quick pace to me, as I do 10-gal/hour sparge for a 10.5-gal batch.

Also, if you're doing a 5-gal batch, try using a 3/8" line, and not any bigger. This prevents getting too much air in the line.

MC

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nate_e

Recipes 

Thanks, I'll try a slower rate.
As for the air, I'm not too concerned about it other than that it seems to be a symptom of the gradual decrease in flow I'm seeing. I'm wondering if draining a bit of water from the MLT before adding the grain at mash-in would flush out air in advance and prevent the initial vacuum "lock". Does anyone do this as standard procedure?
Also I should add that I usually throw in a few handfuls of rice hulls with every batch.

acidrain

Recipes 

Are you draining into a BK that is below the MLT? I'm not understanding why the flow slows once the wort starts to fill the BK.

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Keg #1: Monster Mash Pumpkin Ale
Keg #2: Cascadian Stout
Keg #3: Brandon O Graff

Fermenter #1 RHESB 6.1
Fermenter #2 Citra Pale Ale

Misplaced_Canuck

Recipes 

Grain bed compaction over time. I've had that happen before, especially when using adjuncts.

MC

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nate_e

Recipes 

The bottom of the BK is at least 1ft below the MLT, but not much more than than that. I thought that maybe flow was impeded as the BK filled, but the fact that stirring the mash and starting the sparge again reestablishes flow argues otherwise.

acidrain

Recipes 

He's fly-sparging. I could see that if it was a batch sparge.

It's still impeding it though, and I suspect that is your problem. Try draining into a lower vessel.

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Keg #1: Monster Mash Pumpkin Ale
Keg #2: Cascadian Stout
Keg #3: Brandon O Graff

Fermenter #1 RHESB 6.1
Fermenter #2 Citra Pale Ale

Misplaced_Canuck

Recipes 

I fly sparge. Still happens occasionally, over a time period.

MC

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