Almost-stuck mash/circulation in RIMS setup

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

PeatReek

Well-Known Member
Joined
Sep 19, 2005
Messages
48
Reaction score
0
Location
Bay Area
Hi all -

I'm getting very slow flow in my RIMS system and it's leading to some temperature fluctuations - since not much volume is flowing past the element, it heats up the tube too much, then shuts off for too long as the next volume is pushed in, etc.

I'm using one of the 18" stainless steel tubes from Brewhardware, 1500W 120V element, Auber PID, and silicone tubing. It connects to a 5-gallon round "gatorade cooler"-style mash tun, which has a full-diameter stainless false bottom that is suspended above the drain outlet (ball valve always fully open during RIMS circulation). Standard chugger pump, some back pressure applied.

When I am just heating water up to the strike temperature, everything is totally fine - there are no leaks, no kinks in the tubes or anything like that. After I add the grain, though, the volume circulating reduces noticeably - the tube out of the cooler and into the pump starts to flatten, and the volume out of the RIMS tube into the cooler visibly falls off.

If I shut down the whole system and stir the mash for a couple minutes, I can usually get it back running again at bit of a lower circulation speed. Sometimes I need to do this 2-3 times though.

What should I do? Has anyone else encountered this and if so, what helped?

Thanks for any suggestions...
 
I had the same problem. I couldn't get the consistent flow that's necessary to make RIMS work well. I bought a bag (Wilserbrewer is decent). For about 10 minutes, I pull the bag up by the string every couple of minutes, off of the false bottom. After that, it flows as it should. And the bag does make clean up easy. I mash in a keg, if that matters.
 
Are you just turning on the pump and going full throttle from the get go? In my recirculating BIAB set up I've found I need to ease into it. Otherwise I end up compacting the grain bed and choking off flow to the pump. Similar to a how someone might get a stuck sparge by flinging open the drain valve on a mash tun.
 
1. Use a crush that is more coarse - open the gap on your mill.
2. rice hulls as described by Bobby.
3. start with low flow and slowly ramp up after grain bed set as described by TexasWine.
 
Thanks all.

Should have clarified initially - I always use rice hulls in my RIMS system, and I'm pretty hesitant to use any non-hulled adjunct. The brews I'm talking about were all barley with ~4-8 oz of rice hulls depending on the grain bill.

For "easing into it," then, do you just throttle the output of the pump until it's a slow enough trickle that it isn't getting stuck anymore, and then increase as the grain bed gets properly set?

If so, how do you find this affects your temperature maintenance? With the Auber PID controllers you can "auto-tune" during heating to improve temp control and prevent overshoots, but my impression was that the tuning results were kind of dependent on a certain flow rate. I definitely notice the temp being more jumpy when my flow rate changes.
 
What type of FB is it? If you connect via silicone hose inside, the grain could be squeezing it off. If so consider a hard(er) pipe. Also, a mesh screen on top of your FB might help. I have a NorCal FB (~16" diameter) and it works like a champ - high flow even on wheat beers with no hulls. I crush to about .042".

Also, what is your grist ratio? Changing that slightly may help.

-BD
 
Thanks all.


For "easing into it," then, do you just throttle the output of the pump until it's a slow enough trickle that it isn't getting stuck anymore, and then increase as the grain bed gets properly set?

If so, how do you find this affects your temperature maintenance? With the Auber PID controllers you can "auto-tune" during heating to improve temp control and prevent overshoots, but my impression was that the tuning results were kind of dependent on a certain flow rate. I definitely notice the temp being more jumpy when my flow rate changes.

I start the pump with the throttle valve almost closed, then open it gradually until I get enough flow (i.e. an amount that I'm comfortable won't scorch). If you start the pump with the throttle open, it may compress the grain bed before you can throttle it back.

I don't think the tuning is that critical - there's enough wort and thermal mass in the tube that you can vary the flow rate quite a bit without seeing adverse effects.
 
I second the BIAB suggestion.


I had a number of brews slow / stick with seemingly no rhyme or reason - some had wheat, others none, etc, whereas other brews would be fine. Used copious amounts of rice hulls in all batches to try to be on the "safe side".


Since going with the BIAB bag, I haven't seen my flow drop off, and I've thrown some batches that should definitely stick: 50% wheat hefe, 3lb flaked oats + 2lb midnight wheat in an oatmeal milk stout, 24.50lb imperial stout with a lot of roasted grist and a couple lbs of wheat (making a pared-down version of this recipe for a 7% stout, we had it stick both times prior to the bag). Plus no rice hulls, so we can make bread again from the spent grains. Added benefit to me of easier cleanup, as in my system it's easier to pull the bag out, put it in a vessel, and dump that vs. lifting my keggle off the stand and having to pick out the false bottom and stand in the pile of grains, etc. Really like this addition.


I crush everything at 0.028" as well, and didn't want to change that to accommodate my equipment.
 
I don't think rice hulls do anything. That was my first attempt at a fix, and it didn't change anything. Could be me.

Lessening my crush and lowering my efficiency didn't feel right to me either.

I use a NorCal false bottom. I tried all degrees of slow and fast (some say you need to start full throttle to set the bottom) with no improvement. The bag works great. Just my experience.
 
I use a NorCal false bottom.


Same here (w/level 1 stand), and I don't have anything bad to say about it. I still use it, though now it's more to...kind of establish a grant than as a filtration device I suppose. I haven't had to lift my bag once yet though to clear any flow issues.
 
I'm with you, I have nothing but love for NorCal and Jay. His work is beautiful, and he is a super nice guy. I was a little bitchy about the bag at first, but I really dig clean up this way. I drain out the bottom of my keg, if that makes a difference. Anyway, the wort doesn't seem any worse for wear.

I got the idea of the bag from Yooper; it was a good one.
 
For "easing into it," then, do you just throttle the output of the pump until it's a slow enough trickle that it isn't getting stuck anymore, and then increase as the grain bed gets properly set?

If so, how do you find this affects your temperature maintenance? With the Auber PID controllers you can "auto-tune" during heating to improve temp control and prevent overshoots, but my impression was that the tuning results were kind of dependent on a certain flow rate. I definitely notice the temp being more jumpy when my flow rate changes.

That's what I do. Don't have a RIMs, but my PID does control an element in the kettle. I would tune your PID at the reduced flow rate and that should smooth out the jumpiness.
 
If you just use multiple levels of filtering like a stainless braided line under a false bottom it cuts down tremendously on the chance for a stuck sparge... its worked perfect for me for over 50 brews and not one stuck sparge with my rims...

its not rocket science, finer filter to catch any particles that get through the false bottom. I actually use three stages, False bottom with the stainless bazooka screen below and stainless braided line inside that...

Theres pics of it below in my build thread.
 
I had the same problem on almost the same setup with stuck mashes. Turns out the tubing i used to connect the domed false bottom became to soft causing collapse and no/very slow flow. Ended up switching it to some high temp pvc and never had that issue again.
 
Back
Top