What is your RIMS recirculation rate? Is it important?

[vash68]

I was wondering (and searching a lot) what flow rate do people run their RIMS at, esp. with Blichmann mash tuns?

From my experience, Blichmann's published RIMS recirculation rates are not attainable, at least on my system (2 vessels both 15 gal Blichmann Boilermakers G1).


I know that for 15 gal G1 mash tun max RIMS recirculation rate is 1.3 gpm.

According to this (click Data tab!) data for G2 kettles,
http://www.blichmannengineering.com/products/boilermaker
the 15 gal G2 mash tun max RIMS recirc rate was lowered to 1 gpm.


I have never been able to attain anything close to 1.3 gpm on my RIMS without causing stuck mash within 15-20 minutes after recirc starts. Where does Blichmann draw their specification from? Wishful thinking?


I have brewed about 20 batches with my 15 gal Blichmann Boilermaker G1 mash tun using RIMS, March pump with ball valve on output and 1/2" ID silicone tubing all around my system.

I control my recirculation flow with 1/2" ball valve on pump output and, based on my experience, the safe flow rate for my MLT is only about 0.4-0.5 gpm at best. This seems to be the case regardless of amount of grain in MLT - I use between 12 and 19 pounds depending on batch size.
My normal mash is thin, 2qt of water per 1 lb of grain.

My mash efficiency however is around 80-84% with 2 vessel system, I can't complain there.


There are mostly 2 questions in my head:

1) What RIMS flow rates do you guys use, is there optimal rate for mash or the higher the better?

2) Does it matter that I can only achieve 50% of advertised recirculation rate for my mash tun if I already I get 80% mash efficiency? Another words, can I improve my mash efficiency if I increase my RIMS recircuration rate?

 

[doug293cz]

The standard answer is: "as high a flow rate as you can get without sticking your mash." It is highly system dependent, and what works for one brewer may not work for another. The model of kettle used is probably one of the least important variables in the mix. One of the most important variables is going to be the particle size distribution of your crush. The higher the proportion of fines, the more likely the bed is to stick. Stickier grains like wheat and oats can also drive lower flow rates. You can reduce the proportion of fines in the crush by conditioning (adding about 2% moisture) prior to milling. You can also improve the flow properties thru the grain bed by adding rice hulls to the mash.

As for mash efficiency, you have to break it into it's components of conversion efficiency and lauter efficiency (mash eff = conv eff * lauter eff.) You should target a conversion efficiency of 95% or better. Measure your conversion efficiency using the method described here. Maximum possible lauter efficiency depends on your sparging method, and is highly variable. For no-sparge and batch sparge it is possible to calculate maximum possible lauter efficency, but not for fly sparge (but fly sparge should do better than batch sparge, or you're wasting your time.) You calculate your actual lauter efficiency by dividing your mash efficiency by your conversion efficiency.

Brew on

 

[mabrungard]

As Doug said, recirculate at the rate that your mash allows. A high recirculation rate is not required, but it does improve the ability to control mash temperature. I have a manometer plumbed into the bottom of my mash tun and I adjust the pumping flow to draw the head at the bottom of the mash to about the bottom of mash elevation.

PS: The permeability of a mash varies during the mashing period. It's low initially and it increases. Having a manometer in your system allows you to properly adjust your flow rate to match the mash's permeability.

 

[dyqik]

I have a manometer plumbed into the bottom of my mash tun and I adjust the pumping flow to draw the head at the bottom of the mash to about the bottom of mash elevation.

PS: The permeability of a mash varies during the mashing period. It's low initially and it increases. Having a manometer in your system allows you to properly adjust your flow rate to match the mash's permeability.

An open topped sightglass plumbed in near the base of the mash tun is a very effective manometer, by the way, for anyone wondering how to install one. And is also helpful when transferring strike water and fly-sparging.

 

[vash68]

An open topped sightglass plumbed in near the base of the mash tun is a very effective manometer, by the way, for anyone wondering how to install one. And is also helpful when transferring strike water and fly-sparging.

Dyqik,

my Boilermaker does have open topped sightglass with bottom opening at 1" above false bottom. How exactly can I use it to monitor the flow/pressure?

Measure your conversion efficiency using the method described here. Maximum possible lauter efficiency depends on your sparging method, and is highly variable. For no-sparge and batch sparge it is possible to calculate maximum possible lauter efficency, but not for fly sparge (but fly sparge should do better than batch sparge, or you're wasting your time.) You calculate your actual lauter efficiency by dividing your mash efficiency by your conversion efficiency.

Doug,

thanks for breaking it down for me. I will want to calc my sparging efficiency since I know it is a weakest link in my 2 vessel systems.
My sparging method is a single batch sparge water added to the top of already thin mash (2qt/1 lb), then draining entire first runnings amount, then recirculating sparge water for another 15 min or so at 0.5 gpm.

In my system sparge water is added to the top of grain bed via a length of 1/2" ID silicone hose. Do you mean adding any fancier sparge arm to my MLT may increase loitering efficiency?



Martin,

if grain bed permeability increases during mash, does it mean I can start recirculating at lower rate (say 0.5 gpm for my system) then gradually increase it (to say 1 gpm) ?

Thank you all!

 

[doug293cz]

...

Doug,

thanks for breaking it down for me. I will want to calc my sparging efficiency since I know it is a weakest link in my 2 vessel systems.
My sparging method is a single batch sparge water added to the top of already thin mash (2qt/1 lb), then draining entire first runnings amount, then recirculating sparge water for another 15 min or so at 0.5 gpm.

In my system sparge water is added to the top of grain bed via a length of 1/2" ID silicone hose. Do you mean adding any fancier sparge arm to my MLT may increase loitering efficiency?

...

Your sparge method isn't a traditional batch sparge, and will likely have a slightly lower lauter efficiency than a normal batch sparge. This is because any mixing of the wort and the sparge water above the grain bed will put extra sugar in the sparge water, and that will decrease efficiency. I can't say how much efficiency you will lose a priori, but the delta can be calculated by comparing your actual lauter efficiency to the theoretical lauter efficiency for your grain bill, pre-boil volume, grain absorption ratio, and MLT dead space. You might also lose efficiency because the amount of recirculation you specifiy will only pump 7.5 gal, or about two turnovers of the sparge wort in the MLT. This might not be enough to homogenize the sparge wort, which is what you want to do in order to maximize lauter efficiency.

A fancier sparge arm is not likely to provide any benefit for your sparging method.

Brew on

 

[dyqik]

Dyqik,

my Boilermaker does have open topped sightglass with bottom opening at 1" above false bottom. How exactly can I use it to monitor the flow/pressure?

When you are pumping from the mash tun, you should see the liquid level in the sight glass drop - the weight of the liquid in the tube is supported by the pressure at the inlet, so when the pressure at the inlet drops due to suction from the pump and the resistance to flow from the mash bed, the liquid level drops.

I adjust my pump's outlet valve to keep the liquid level around the 2 gallon mark in the sight glass. At the start, I might be at a bit below half of the maximum opening, but by 30 minutes in I can usually open the valve all the way. This is for 5.5 gal batches with a 10 gallon Home Depot cooler and a 24V "little tan" pump.