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How Is False Bottom Constructed In Lauter Tun

How is the false bottom constructed?

The false bottom is installed in the Lauter pool to provide support to the grain bed during the saccharification process and to retain the spent grain after the fluidization is complete. However, most of the separation of wort from grain during flow occurs in the grain bed itself. Ideally, the grain bed floats a few inches (30-40 cm) above the false bottom. In larger containers, the false bottom is constructed as a series of interlocking plates that together cover the entire area of the bottom of the container. They must be narrow enough to prevent the passage of large particles, yet wide enough to avoid being clogged and blocking flow altogether. It is a good idea for the slots or holes to be wider on the lower side than the upper side to prevent particles passing through the sieve from clogging the gap. In general, the total open area of the false bottom is 11% or more. And the distance between the false bottom and the bottom of the tank is 15cm-16cm.

How Is False Bottom Constructed In Lauter Tun
How Is False Bottom Constructed In Lauter Tun

For the dry grinding method, the false bottom can hold 160-175 kg/m2.
For the wet milling method, the false bottom can hold 170-210 kg/m2.

We can calculate the diameter of the Lauter jar based on the volume of the malt.
Generally speaking, after the dry malt is milled and water is added, the volume of the spent grain expands to 1.65-1.8 times.
For example, for a 1000 L brewing system, the malt is 200 kg according to malt: water = 1:4.
For 200 kg of malt, the final waste grain would be 0.2×1.8 = 0.36 m³.
Ideally, the thickness of the spent grain bed is between 30cm-40cm to allow for filtration. We set it to 35cm.
The volume of waste grain is 0.36m³.
Πr² x 0.35m = 0.36m³.

With this formula, we get R=0.57m
Diameter 0.57×2 = 1.14m, outer diameter 1.14m + 0.16m = 1.3m
If the malt is larger than 1:4, for example 1:3, then the diameter of the grinder will be enlarged accordingly.

Kilns are available in different bottom types.


In terms of volume, fermenters up to 2000L have a conical bottom, while those above 2000L have a flat bottom. The reason for this is that in systems above 2000 L there is usually a separate chamber.
For fermenters with extended collection rings and back pressure flushing devices, flat bottom fermenters are used.

Therefore, the support under the false bottom is different in different bottoms. The first picture shows a support for a percolation tank with a conical bottom, and the second picture shows a false bottom support for a flat percolation tank.
In addition to the above-mentioned false bottom support, there is another way to fix the false bottom to the bottom of the tank with a nut, because there is a large density in the grain bed. How to take out the false bottom?
See the picture below, we can use a Phillips screwdriver to open the nut and take it out, screw on the small handle in the second picture, lift the false bottom plate and then we can take out the rest of the false bottom. The same method as the fan-shaped false bottom.