Total Grain Bed Depth

[brewfun]

82.83 gallons in 39" of height equates to .47" per gallon

.47" times 58.98g = 27.7"

82.23 gallon capacity / 39" height = 2.1 gallon per inch. That's at 0% expansion.

At 4% expansion, the volume drops to 78.9 gallons total capacity and BeerSmith accounts for that. This is useful when actually brewing, but when designing equipment a difference of even a few gallons can be problematic.

The issue wasn't what the mashtun would hold, it was what depth a heat coil should be installed for optimal use. In that case, converting volume to weight takes the heat and displacement out of the equation.

I'm all for making it simpler to calculate, but I'm not at his brewery, I can't see the equipment and I don't know his methods. Having worked with American, German and Chinese brewery manufacturers, I've found that knowing the root math helps avoid design mistakes from assumptions. It really sucks to find out after 4 months of waiting and hundreds of thousands of dollars that capacity is even 2% less because one piece was approved with the wrong dimensions. An 80 bbl brewhouse with a 2% error in capacity can add up to 4500 bbl/year of loss or $1.7 million in lost potential sales per year at capacity. Basically, the cost of the whole brewhouse, every year. On the scale of OP, it could mean $15K per year, which aint nuthin.

[dtapke]

it would be 2.1 gallons per inch, not 2.1" per gallon

2.1" per gallon would mean his 39" tall vessel would only hold 18.57 gallons

but i see what you're saying about losses due to mistakes in simple calculations, makes sense.

[jimgsp]

 - dtapke

Thanks for your input.

I will be brewing in January and putting this to the test. I will build a complete digital log which will include grain bed depth, and I will share that.

For my purposes, the calculated numbers we came up with are simply an approximation. I just needed a number within a few inches of actual. That said, I too am curious as to what we will end up with.

For me, the logic and the math that brewfun has shared with us substantiates a realistic number. I am condfident that number will be very close to actual.

Stay tuned......

[brewfun]

it would be 2.1 gallons per inch, not 2.1" per gallon

2.1" per gallon would mean his 39" tall vessel would only hold 18.57 gallons

but i see what you're saying about losses due to mistakes in simple calculations, makes sense.

Yup you're right. My bad, more coffee before posting needed. Now corrected.

[dtapke]

I'm intrigued to see your numbers, as I intend on moving from my 1bbl to a 3bbl system in a couple years. That said, it seems our numbers came incredibly close.

I imagine actual accurate grain bed depths to be difficult to measure with smaller systems like this. Once moving into larger 100bbl and up systems i think the calculations will be much more accurate as using rakes in the mash will help keep the grain bed at a more uniform height, whereas with smaller systems like this there's bound to be a greater percent variance due to uneven distribution of grain.

I'll be brewing this week and I'm curious to measure my grain bed depth throughout different points of the brew and see how much it changes and compacts during the course of the mash/sparge. I feel that with my system I'll be seeing 1-2" of variance from start to finish. I think I've been having some slight issues with compaction and need to figure out how to remedy this (slower sparge i'm sure!) as my mash efficiency on larger brews drops down to around 75-78 and on smaller brews i run closer to 85%