Author Topic: RIMS and false bottom  (Read 2498 times)

Offline bluedog

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RIMS and false bottom
« on: September 20, 2010, 12:19:23 PM »
I am currently using a RIMS set up for mashing in a ten gallon pot on the stovetop. I like it because I can step mash and have been hitting 75% or better efficiency routinely. However, I have noticed as I start to increase my grain bill my flow rate becomes a trickle. I am using a perforated false bottom in my mashtun. I thought at first it was because of the flow rate being too fast. But now I think it's because of the added weight of the grain compressing the grist. My last brew was 15 1/2 lbs of grain - I could not get it to recirculate as it kept plugging the screen. Again this has not happened with smaller grain bills (10 - 12lbs) even with more than 50% wheat. I am thinking about getting a Blichmann false bottom. Does anyone out there use one with a RIMS and if so do you like it? 

Offline dak0415

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Re: RIMS and false bottom
« Reply #1 on: September 20, 2010, 12:36:55 PM »
How fast IS your flow rate? I have a rims setup using a 13.3 gallon keggle with a 12" domed perforated false bottom.  My typical grain bill is 22-25 lbs but my flow rate is 1 gallon/minute or less.  I have a very small mash pump.  Even then I start the pump at about 1/2 open for the first 10 minutes or so as the grain bed settles then open the valve up all the way.
Dave Koenig
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Offline bluedog

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Re: RIMS and false bottom
« Reply #2 on: September 20, 2010, 02:54:20 PM »
I have 2 valves - one on the pot and one on the outlet side of the pump. I usually start with the one one the pot wide open, I have a March pump and it's gravity fed. I usually have the outlet on the pump only a quarter open or less. I run for a while like this and can tell when ther grain bed is set. The flow slows down a bit but stays even. It seems that when I up the grain bill I get a "stuck" recirculation. I am thinking it has to do with the depth of the grain bed.

Offline hopfenundmalz

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Re: RIMS and false bottom
« Reply #3 on: September 20, 2010, 03:41:32 PM »
Jeff Rankert
Ann Arbor Brewers Guild, AHA Member, BJCP Certified
Home-brewing, not just a hobby, it is a lifestyle!

Offline bluedog

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Re: RIMS and false bottom
« Reply #4 on: September 20, 2010, 03:55:40 PM »
It's looks like this
http://www.northernbrewer.com/brewing/false-bottom-for-10-gal-megapot.html#

If it is because of the depth/weight of the grain bed, I'm thinking this will help
http://www.northernbrewer.com/brewing/false-bottom-for-10-gal-boilermaker.html#

The design is different

Offline dak0415

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Re: RIMS and false bottom
« Reply #5 on: September 20, 2010, 06:03:39 PM »
I have 2 valves - one on the pot and one on the outlet side of the pump. I usually start with the one one the pot wide open, I have a March pump and it's gravity fed. I usually have the outlet on the pump only a quarter open or less. I run for a while like this and can tell when ther grain bed is set. The flow slows down a bit but stays even. It seems that when I up the grain bill I get a "stuck" recirculation. I am thinking it has to do with the depth of the grain bed.
Are you sure you are not getting grain bits stuck in the valves 'cause they are not fully open?  Keep the valve on the inlet side full open.  March pumps only like their outlets restricted.  I get lots more bits when my grain bed gets thicker.  Open the valve on your outlet side occasionally especially during the first 5 minutes or so and let the splooge loose.  Also try opening the gap on your mill a little, that will make the bits bigger so they will stay on the mash side better.  Finally add some rice hulls to the mash.  That will also keep the bits on the right side.
Dave Koenig
Anything worth doing - is worth overdoing!

Offline augie023

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Re: RIMS and false bottom
« Reply #6 on: October 11, 2010, 08:11:11 AM »
Is it a perforated SS false bottom like this?
http://www.homebrewing.org/12quot-Stainless-Steel-Domed-False-Bottom_p_1058.html

Or is it like this?
http://www.homebrewing.org/Stainless-Steel-PICO-style-keg-kettle-false-bottom_p_1010.html

I might have an anwer for the first one.

What is your answer on the first one? I am planning on building my RIMS soon and have that false bottom but want to be prepared for any issues

Offline wingnut

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Re: RIMS and false bottom
« Reply #7 on: October 11, 2010, 08:33:09 AM »
I do not think the Blickman style false bottom will be any improvement compared to the screen you are presently using.  In fact, I think that it is a move in the wrong direction.  Using a screen, you essentially have the best ability to let wort flow evenly thorugh your grain bed.  The Blichman is pretty close to providing that, but the design is geared slightly more toward longevity and easier clean up.  It can support a larger grain bed, but as long as your screen is not warping, the more robust desing will not be a benefit.

Things that I have noticed that have reduced my mashes from sticking while sparging:

1.) Stir the Grist and get all the pieces in suspension before letting the grain bed settle.  The larger pieces will naturally fall faster than the small, reducing the small bits from clogging your screen.  To aid this I add the water FIRST, then add the grains.

2.) Open the valves 100% every once in a while.  I do not have a pump system, but I did notice that grains would sneak through and sometimes build up in front of my valve that is metering flow.  By opening 100% and then back down to the metering position, the grain bits get unstuck and normal flow continues.

3.) Grind the Grain a bit bigger/add rice hulls.  Depending on the mill, your husks may be getting chewed up a bit too much by your mill, and not providing the "large" filter pieces needed to prevent a stuck sparge.  If you love your mill setting and do not want to change it, add some rice hulls to your grist (.25 to 1lb of hulls depending on the amount of grist)  That will supply extra "large" pieces without forceing a change to the milling size.

4.) Cut cross channels in your grain bed during sparging... about 1/3 to 1/2 grain be depth.  I have noted that some malts are high in gummy proteins that really slow down sparging if not addressed.  One way to reduce the gummy proteins is to do a protein rest around 130F.   However, an easier way to address the issue is to cut cross hatches into the grain bed, about 1.5 in square into the grain bed to break up the protein gunk and allow flow.  One key identifier of the issue is a lot of grey sludge floating in the grain bed about 10 to 15 minutes after dumping in the grains.  NOTE: it is important to not cut the bed too deply as that will lead to channeling and reduce your efficiency.  It is also important to cut uniformly for the same reason.

Good luck!
-- Wingnut - Cheers!