Flow rate issues for 55 gallon mash tun

Bullka · 12-28-2009, 03:11 PM

I built a 55-gallon stainless steel brewing tree last month and successfully brewed my first half batch at the end of November. We are brewing a full 40-gallon batch this Sunday and would like some advice on our mash tun. Last time we brewed just a 20-gallon batch and it took 3 to 4 hours to collect the wort from the mash tun. I am worried about 3 main things with this and I am not sure if any of them are bad or not; is the grain going to soak for too long? Will the temperature loss over 4 hours cause problems? And we are just impatient and want to know if we can speed up the process.

Our setup is (2) 12” bazooka screens with SS pipe to a ball valve at the bottom of the barrel. When we first started to drain the wort after an hour soak we opened the 3/4" valve all the way and just let it flow as fast as possible, around the rate of 2 gallons per minute. After about the first 4 or 5 gallons the rate decreased quickly to a trickle. The rest of the time it flowed at a gallon every 15 minutes. I have read now that our flow rate was too high and we may have compacted the grain. This is an easy fix to reduce the rate to 1 gallon in 4 minutes with the ball valve, but the issue we have with that is it will take us over 3 hours to collect the wort on a 40 to 50 gallon batch if we can even get a proper flow rate of 1 gallon in 4 minutes. What are your thoughts?

We also placed the grain in the mash tun first then poured the hot water on top, this time I will reverse that to help prevent clogging and get a better grain bed. Let me know if you have any suggestions to prevent our system from clogging besides reducing the flow rate and adding the grains to the hot water. I appreciate your help!

*added note: we will be batch sparging for this brew day, but next time I might try fly sparging. I have not done a batch this large so we will see how it works.
I was told by another home brewer not to disturb the grain bed when adding the second addition of hot water after draining off the first running, on my previous batch I just added the second addition through a sparge arm. But everything I just read online recommends stirring in the second addition of hot water for a batch sparge. As noted below, that will be a little difficult with 100 lbs of grain, what do you recommend?

chefmike · 12-28-2009, 04:45 PM

I would first try the two changes you have cited. I would think both will improve your lauter.

I would also think that you may be able to increase the flow over the first half hour while maintaining the stability of your grain bed. Batch sparge or no sparge, I am assuming?

As to temperature loss... my reading leads me to believe that the impact of that should not be significant, though I am not versed in batches of this scale. Alot of this thought was taken from discussions of overnight mashing.

I bet your lauter speed improves.

Luckily others far more experienced than I should be along soon. I am just avoiding some chainsaw work outside!

**FSR402** · 12-28-2009, 05:37 PM

For me it takes about 2 hours to sparge (fly sparge) I can do it faster but I have no need to.

Are you batch sparging? I do fly on the big batches just because once you have a 150 pounds of grain settled in the bottom of the tun the last thing I want to do is try and mash paddle that thing. I also pump thru my flash boiler for about an hour to mashout and stop the conversion. So with that it's a 3 hour job after mash is done.

brewpal · 12-28-2009, 06:59 PM

You may want to consider using a ss screen over a larger area. Our 55 gal drum for mashing used a screen originally made to fit the bottom of a sanke kettle. We got it to seat firmly against the bottom of the drum by using the copper pipe to apply some pressure down.

We could comfortably mash 100 lbs and fly sparge in 45-60 min.

You might also consider trying to condition your grain for better flow.

Pumping strike water into MLT
False bottom screen
100 lbs mashing

Bullka · 12-28-2009, 07:07 PM

If the process does not become more efficient this time, I will definitely move towards a mash screen. I have only been brewing for a year and am still pretty new to all of this, how would I condition my grain for better flow?

Gregredic · 12-28-2009, 07:38 PM

Another possible fix....

Try using rice hulls. That's what we had to do in order to fix our stuck sparge problem's....should help yours out too.

chefmike · 12-28-2009, 11:13 PM

malt conditioning

it leaves hulls more intact... rice hulls would be similiar, but conditioning is cheap!

brewpal · 12-28-2009, 11:14 PM

Malt Conditioning:

http://www.homebrewtalk.com/wiki/index.php/Malt_Conditioning

Did this recently on a 50% 2-row/50% wheat mash and it worked great. No run-off issues at all. Cheaper than buying rice hulls.

Combine that with a mash screen and you should see improvement.

MikeRLynch · 12-29-2009, 01:12 PM

Did you say that this is a 55 gal brewing tree? I'd like to see some pics of that!

**Cape Brewing** · 12-29-2009, 02:21 PM

Holy SNIT!! "hours" to sparge???

Wow, I'm doing something really wrong then. I have a 30 gallon SS pot as a MT with a full sized false bottom and then under the false bottom is a good-sized copper manifold (just 'cause I had it).

I sparge in about seven minutes with a March pump. I cut back the flow rate a little bit with a ball valve, open the bottom of the MT and pump it out. Ten minutes tops and I'm done.

I would be really nervous about having grains sit that long. Wouldn't you start pulling a ton of tannins out of the grains with the wort sitting in the mash that long?