Stuck mash, Biab bags and recirculating

[Tytonegro]

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 filterbag. 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 included a few pics to clarify

 

[Hpal]

I have built a recirculating biab rig as well (pics in my gallery), had the same problem with the fine mesh bag filling up and pumping dry. Got a mesh bag from country brewer which is coarser and works well. I'd try to recirc a little slower to give the liquid time to drain through.

 

[Tytonegro]

I have built a recirculating biab rig as well (pics in my gallery), had the same problem with the fine mesh bag filling up and pumping dry. Got a mesh bag from country brewer which is coarser and works well. I'd try to recirc a little slower to give the liquid time to drain through.

I saw on some photo's that some Biab bags are considerably coarser than mine. So that might be a pointer to a solution.

Do you have any idea about the flow of your pump (throttled or not)?

 

[Hpal]

with the coarser bag I can have it on full flow, I use the little brown pump as well. With my original fine bag I would throttle it back with a ball valve on the outlet to 1/3 or 1/2 open. You just have to match the pump flow to the bag flow, if in doubt don't let the element come on at the same time as the pump's recirculating so you're guaranteed there'll be wort around the element.

 

[Hpal]

Update. I accidentally snapped the fitting off my little brown pump, so I bought one of the keg king 240v ones at 19L/min. Ill try to recirc a bit faster with that and hopefully the bag is coarse enough. This means I may also be able to finally tune the pid with the temp probe in the pump inlet because the little brown pump was not flowing fast enough and gave me too much overshoot.

 

[motman]

Maybe try a t on the outflow of the pump, with one line back into the base of the kettle or back into the in pipeline with a tap to restrict the flow just enough so you get the desired flow back up to the top?

 

[Fat Bastard]

I think you'll have trouble with it. Initially in my brewing career I did a sort of 1.5 v recirculating BIAB thing with a bag in an urn (basically) resting on a false bottom thing to keep it off the element and it would easily suck the element/deadspace dry even with a 12v Little Brown Pump. You could fit a return line to the base of the kettle to cure it as suggested, but bear in mind that if the flow into the base exceeds the flow back to the top of the grain bed it'll muck the grain bed up and defeat the purpose. Slow and steady definately wins the race with a recirculating BIAB system!

 

[mattlea266]

I run a 19 litre per minute pump (Kaixon) and found the bag was the biggest problem in early testing. Ended up getting a bag from craftbrewer and have not had a problem since. Another thing is your crush, are you grinding in a coffee maker still or using a mill. The finer the crush the more likely you will get blockage with this type of system. Also, some types of grains can have an effect such as rye. (worst brew day ever).