RIMS/HERMS Grain Compaction?

Yes, I'm aware I started two threads with RIMS/HERMS in the title. They're not the same topic.

Having had my direct fired RIMS tun running for a good 6 batches or so, I'm having some issues. During the warmer months, I didn't have to run the burner or pump during the sac rest at all. With two layers of reflectix, I'd lose maybe 2F over 60 minutes. That's comparable to a cooler and within my tolerances.

Now that it's cold in the garage, I've been applying heat at the 30 minute mark (and dabbling in step mashing". What I've found is, no matter how slow I attempt to run the recirculation, after about 15 minutes I start pulling air due to grain compaction similar to a stuck sparge. I have a 15" diameter full false bottom so I'm surprised I'm running into this problem. For now, my solution has been to stir the mash every 10 minutes or so when I'm running the pump, but I get the impression that most folks with semi-automated systems are more hands off. What gives?

This issue has been keeping me from considering the old heatstick on a controller type systems since I can't run the pump for 60 minutes and walk away.

Many people use grants. Gravity feed into a container and then connect the out of the container to your pump. Adjust the flow into the container and the speed of the pump so the level stays constant. I wish I had some links for you but in the past I've seen small SS containers (like the kind you store coffee in w/ the glass lid) modified w/ weldless fittings to achieve this. Maybe that will work?

By the way, I use a HERMS system but have the coil in a different container (1 gallon cooler). I use 3/8" copper tubing and the coil creates enough resistance that I can run the pump full open w/o compacting the grain. It was by accident as I was looking for 1/2" tubing but it was too expensive at the time so I went with 3/8". I now just open the required valves and turn the pump on. After it's recirculating for a few minutes I give the mash a stir and the bed seems to float back to normal and it's g2g for the entire time.

With my HERMS I run my recirculation for the full mash. I leave my 1/2" valves about half open and dont have any issues with grain compaction.

I have no clue.

Barring some massive, consistent, air filled dough balls.....

What bothers me is the "pulling air" bit. the screams of a leak that is temperature sensitive and only shows itself when there is a pressure change (or something like that).

I dunno exactly, it's too hard to say at this point as there are too many variables at play (Grain bed depth, recirc rate,etc.) but my best guess is that when the heat is on, something is opening up enough to allow the pump to pull in an air pocket, cavitate, and lose prime.

No air leaks in the system. Well, think of it like this, the grain sits on top of my false bottom. As more and more of the wort is pump up on top, less of it is available in the space under the bottom. The siphone tube picks up the last of it until it starts getting air. Of course, I could reduce the flow to a mere trickle to give the wort time to slip through the compacted grain bed, but I'm also concerned with overheating.

Here's something I just thought of. I run thick mashes somewhere in the range of 1-1.25qts/lb. My tun takes 7/8ths of a gallon before it hits the FB. I typically calculate to 1qt/lb and then add 1 gallon. So for example, on a 16lb grain bill, I'd use 5 gallons. Nearly one gallon of that is below the FB.

For those that run full time recirculation, what are your thicknesses?

There is about .5 quarts below my false bottom, I mash in at 1.25qt/lb. I use a constant recirc.

The odd thing is that the only difference you noted, was adding heat.

Another variable I'm thinking about is crush. I mean, I crush WAY fine.

If you have changed your crush since the warmer months, that would make more sense to me than the heat. May not want to crush so fine then.

I haven't changed the crush at all since I got the mill and first set it up. What's changed since summer is how often I recirculate. When it warm, the longest recirc time is for mash out ramp up.

Okay. I have to point the finger at your crush. I have been DF recirculatory with a Sabco FB for that last 8 or 10, 10 gallon batches and have never had this problem.

My typical mash ration is 1.25 to 1.5qt/lb and I would always open my pump valve slighly to set the bed for about 5 minutes and then wide open through the mash cycle.

I, however, use a fixed gap JSP mill.

.45mm,IIRC.

Maybe it's time to back off the flour or start adding rice hulls to loosen things up a bit.

edit: you beat me to the post. I still suggest adding a cup or two of rice hulls to see if that helps.

What about reversing the flow? Draw from the top and pump into the bottom. This way you can pump faster, will get some better mixing action in the mash, which helps with homogenizing the temp and mash conversion. But you’ll need some false bottom/mesh on top of the mash to keep the grain out of the wort that goes to the pump.

This is how I would operate a RMS/HERMS if I had one. Once the mash is complete, reverse the flow to clarify the wort.

Kai

Interesting idea but I would certainly have to thin the mash a bit more for that also. I suspect that if I were to give up some efficiency by thinning out to 1.75qt/lb I'd be ok in either direction. I'm just trying to keep my process as efficient as possible and still be able to control my temps more accurately.

Bobby_M said:

Interesting idea but I would certainly have to thin the mash a bit more for that also. I suspect that if I were to give up some efficiency by thinning out to 1.75qt/lb I'd be ok in either direction. I'm just trying to keep my process as efficient as possible and still be able to control my temps more accurately.

Click to expand...

I doubt that you will loose efficiency by going to a mash thickness of 1.75 qt/lb. I actually recommend a thin mash like this and based on my experince you may actually gain efficiency b/c tinner mashes tend to have a better conversion efficiency.

If you count on using more sparge water, which you do with thick mashes, you will get more wort from sparging than from the first wort. While I'm not saying that you are oversparging I'm inclined to say that less sparging will produce a higher quality wort.

Kai

I don't think I'm oversparging since my 3rd runnings are still in the 1.015-1.020 range and my mashes always test starch negative. I just know that my average mash/lauter efficiency dropped from 92% to 88% when I flat out added a gallon to my mash to make up for false bottom dead space. I'm just assuming thinning out even more would hit me for another 4-5%. I'd be willing to give it a shot tomorrow though.

I have very little experience of batch sparging, but from what I have read, when sparging with multiple batches, efficiency increases if the batches are all approximately the same size. If that is the case, wouldn't it make sense that the maximum efficiency would be achieved if the first running were equal in volume to each of the batch sparges?
As for mashing thinner, it has been my experience (brewing English style ales with English malts) that a thicker mash converts faster and produces a more dextrinous wort, but I did not notice any difference in efficiency. However, I was comparing 1 qt / # with 1.25 qt / #. As the thinner mash produced inferior results (by English standards), I saw no point in trying even thinner mashes.

-a.

The reason why thinner mashes produce lower efficiency would be the fact that there is less water left to sparge with given a fixed preboil volume requirement. In a moderate grain bill, a small shift from like 1qt/lb to 1.25 would be negligible but when the grain bill gets larger, you could be "stealing" 2 gallons from your sparge.

I'm brewing a 1.050 Lambic tomorrow and all three of my runnings actually do turn out to be around 4 gallons starting with a 1.45qt/lb mash ratio. We'll see how that goes.

There are two components to mash efficiency: conversion efficiency and lauter efficiency. So far the impact on the lauter efficiency has been mentioned for tinner mashes: less sparge water thus a less of the dissolved extract is transfered from the mash to the kettle.

While a tinner mash has a negative effect on the lauter efficiency, it can have a significant positive effect on the conversion efficiency. This means it may enable you to get more of the starches converted into extract. Full conversion of the mash, as tested with an iodine test, only tells you if the starches that were gelatinized and washed into the mash liquid were converted. But it doesn't tell you if you have unconverted starch left in the grits. The idea that a thin mash is better at getting more of the starches gelatinized and converted is supported by the fact that gelatinization requires free water, of which less is available in thick mashes, and that high sugar concentrations have been shown to increase the gelatinization temperature of starch.


Ajf, yes, English beers should be mashed thick as this is traditional for these beers and it might be necessary for their character. But along with a coarse crush that is used for these mashes, the mash efficiency is also lower than what you would get from a traditional German mash for example which is thinner (2/3 of the water for mashing and 1/3 for sparging is a rule of thumb) and more finely crushed.

Kai