Stuck mash, Biab bags and recirculating

Hi,

I'm designing an electric one-pot RIMS system where I use a BiaB bag to hold the grain during the mash. You could say: another Braumeister clone...

I'm not a real metal worker and my wife is handy with the sewing machine ;-) Therefore I opted for this bag solution instead of some metal false bottom with slits/holes that act as a sieve. I see quite a few people making 'Braumeister' clones, using malt pipes and the like. In my first attempts, I used a false bottom (with big holes) and had the bag sitting on top of that, just to prevent it from touching the bottom/heater.
I use a small 12 Volt pump (the brown Chinese one ;-) that is rated 109 G/hr (6.9 L/min) and I found that it runs dry because the wort doesn't flow quickly enough through the grain bed and filter bag. In my first version, the bag was sitting against the wall of the brew kettle so that in the end only the bottom was 'available' as active filter area. The version I tried today is shaped like a bucket, so it tapers to the bottom, and hangs free in the kettle, so that the total submerged area is available for passing the liquid. But alas, still not good enough. Within 30 sec. you see the level of the wort rising inside the bag with 2 or 3 cm (1 inch) and it doesn't take much longer or the pump runs dry.

Especially when the system is heating up in a multi-step mash, I would like the pump to run continuously to avoid overshoots in temperature.

I read that even the Braumeister suffers from this type of blocking with higher gravity beers. Therefore I was wondering what solutions people have come up with that work.
Just pumping slowly?
How much is slow or too fast?
What volume rate per area is more likely to work? (of course it also depends on the height of the grain bed.)
Any other solutions or ideas?

Thanks a million,

I've attached some pics to clarify my setup

You may also need a false bottom. Are you leaving the mash to settle 10 mins before trying to run the pump. When you mash leave for 10 mins then open tap pour into a jug and gently pour back on top of the grain. Repeat this 5 or 6 times draining a litre at a time. Leave again to settle then try the pump. If that fails you may also need a false bottom too

Mark1964 said:

You may also need a false bottom. Are you leaving the mash to settle 10 mins before trying to run the pump. When you mash leave for 10 mins then open tap pour into a jug and gently pour back on top of the grain. Repeat this 5 or 6 times draining a litre at a time. Leave again to settle then try the pump. If that fails you may also need a false bottom too

Click to expand...

Thanks for the tip.
The settle time is for the grain to absorb moisture, I suppose? Does that prevent the grain from clogging/sticking?

I haven't tried that, but will do the next time.

Why would I need an(extra) false bottom?

rather than pump from the drain, as the pump can try and suck pulling the grain down from suspension and restrict further flow.
Perhaps drain into a small insulated reservoir fittied with a float switch inline with your pumps drive current, and to avoid cavitation under the FB adjust the flow from the tap to a minimal one, Pre heating the vessel used for the float switch would probably be needed, kinda spoils the simplicity of a one pot system, but with a moderate pump flow <1l per min a 2-3l capacity pot should work..

perhaps save a bag of spent grain for some optimum flow tests, bung the spent bag in the pot and flood with cold water and monitor how fast it drains naturally through the grain, that should provide a rough metric for the max flow you can expect with hot liquor during a brew.

Or fit a central tube into the bag of something like 22mm copper tube keeping its centre grain free somehow?, determin its length/height to sit just below the full level pre pumping, then if you overpump the extra liquor will flow down the tube to the bag bottom and straight back to the pump source.. check out the grainfarther a nz brewmeister type option, it employs this idea.. doughing in might be a bit harder this way.

Fil said:

rather than pump from the drain, as the pump can try and suck pulling the grain down from suspension and restrict further flow.
Perhaps drain into a small insulated reservoir fittied with a float switch inline with your pumps drive current, and to avoid cavitation under the FB adjust the flow from the tap to a minimal one, Pre heating the vessel used for the float switch would probably be needed, kinda spoils the simplicity of a one pot system, but with a moderate pump flow <1l per min a 2-3l capacity pot should work..

perhaps save a bag of spent grain for some optimum flow tests, bung the spent bag in the pot and flood with cold water and monitor how fast it drains naturally through the grain, that should provide a rough metric for the max flow you can expect with hot liquor during a brew.

Or fit a central tube into the bag of something like 22mm copper tube keeping its centre grain free somehow?, determin its length/height to sit just below the full level pre pumping, then if you overpump the extra liquor will flow down the tube to the bag bottom and straight back to the pump source.. check out the grainfarther a nz brewmeister type option, it employs this idea.. doughing in might be a bit harder this way.

Click to expand...

Thanks for your thoughts.

Yes, we have been thinking about this external small reservoir and all that comes with it, that, as you mentioned, complicates matters. ;-( So for now I skip this one.

It might be a good idea just to measure how quick the liquid drains with some spent grain. I'll definitely try and do that. The flow you mentioned ( < 1 ltr/min.) is much lower than I probably have now. It makes me wonder if that would give enough flow over the bottom/along the heating elements to give proper temperature distribution.
Another thing that came up was using the full capacity of the pump, but split the output partly through the grain and partly beside it. This way you could still have a good flow over the heating element.

The idea with the overflow tube might also be complicating matters. The length should be adjustable and how to keep the grain out?

Anyway, enough food for thought.

btw I saw on some picture that some people use voile bags that have a much coarser fabric than I'm using. Maybe that's a pointer to a solution.

Is the metal (mesh pizza tray?) sitting flush with the bottom of the boiler, or do you suspend it to keep a reservoir of wort underneath? I can't quite tell from your pics, but if it's just sitting on the bottom of the boiler, a few SS bolts could make some legs for it, which would raise it from the bottom which would leave the wort draining from there instead of pulling it through the grain, compacting it around the tap.

If not, i've no idea, but if you resolve the problem, please let me know. I have a similar set up in a 50L pot. My element is a kettle element so I've had to create legs for my fb. I want to step mash easily so I have a mag pump but am yet to use it.

markm1878 said:

Is the metal (mesh pizza tray?) sitting flush with the bottom of the boiler, or do you suspend it to keep a reservoir of wort underneath? I can't quite tell from your pics, but if it's just sitting on the bottom of the boiler, a few SS bolts could make some legs for it, which would raise it from the bottom which would leave the wort draining from there instead of pulling it through the grain, compacting it around the tap.

If not, i've no idea, but if you resolve the problem, please let me know. I have a similar set up in a 50L pot. My element is a kettle element so I've had to create legs for my fb. I want to step mash easily so I have a mag pump but am yet to use it.

Click to expand...

In the setup as shown in the pictures, the pizza bottom is tied to the bag and hangs about 4 cm above the bottom of the kettle. I also used a separate bottom as you described, that was indeed supported on 4 screws as legs.

In the meantime we have made a new bag of much coarser fabric. This seems to solve the problem.
The original bag was said to be 130mil, now its about 0.5 mm (500mil) openings.
Together with a coarser grind and waiting 10 minutes after filling the grain everything went very smooth even without cloudiness of the wort.
I will post pictures of the two types of fabric later.

Added photo: On the right the new coarser bag, on the left the old bag that was too fine.