Author Topic: Mash tun Dead Space, recoverable dead space and grain absorption  (Read 1191 times)

Offline atlref

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I am trying to get a better understand of the proper way to go about my equipment and advance settings dialed in.
My setup -  3 vessel all grain Rims. Boil kettle 20 gallon Blichman G1 Mash tun 20 gallon Blichman G1 w/ Blichman false bottom, HLT 15 gallon Blichman G1. HLT and BK are gas fired.  2 chugger pumps and 5,500 ULWD heating element ( running on 120V so +/- 1,400 watts) for rims tube.
I have measured my true dead space ( unrecoverable water left under false bottom) = .1 gallon.  I have .5 gallons of recoverable mash dead space ( pump, lines, rims tube).
Process- Mash in recirculate for 60 min. and drain to BK. Add sparge water, stir, recirculate 10 -15 to clarify and ramp temp to 168 for mash out and drain to BK -   AT THIS POINT I would like to hit my pre-boil volume   -   I do not want to go and chase the last .5 gallon that will still be in my rims tube and lines leading into MT ( I know I could pump additional water from my HLT thru the lines to push the wort into the MT before draining but prefer not to.)

SO my question is -  Do I need to change my dead space to include this .5 gallons ( so it would now be .6 gallons) that is left in the system and at the same time decrease my recoverable dead space  to 0 ?  If I do this will it effect my water to grain ratio in the mash ( I believe the purpose of the recoverable mash dead space is to help keep your water/grain ratio in proportion).

Question 2 -
to compensate for the above scenario I have been increasing my grain absorption number . If I make the above changes should I go back to the standard .96 fl oz/oz and use an excel sheet to track and adjust absorption and adjust accordingly?

Thoughts comments will be appreciated.

Offline Oginme

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Re: Mash tun Dead Space, recoverable dead space and grain absorption
« Reply #1 on: January 31, 2020, 04:34:18 PM »
It sounds like you are pretty much on the right track in terms of defining your process.

If it were my system running it the way you are, I would add that additional amount in the mash tun dead space.  Since the water left behind will really be separate from the grain absorption and I really would not want to have this volume change due to differences in the grain bill, but more of a planned excess which is not drained out of the system. 

I would validate the grain absorption figure [mostly because I am a process geek and like to define these losses for my awareness] by monitoring total water into the mash tun (infusion + sparge) versus the volume collected in the boil kettle.  That figure less the wort volume planned on being left behind should be your grain absorption which can be tracked over a few brews to make sure that the setting is good enough to rely upon. 

Recycle your grains, feed them to a goat!