How is false bottom constructed in lauter tun?

helen 2018-03-24

How is false bottom constructed?

The false bottom is installed in the Lauter tun to provide support for the grain bed during the mashing in process and to retain the spent grain after runoff is complete. During the runoff,however, most of the separation of wort from grains occurs in the grain bed itself. Ideally ,the grain bed floats several inches above the false bottom(30-40cm).in larger vessels,the false bottom is constructed as a series of interlocking plates that fit together to cover the entire area of vessel bottom.smaller vessels may have only two such plates.the design of the slots in the false bottom is important. They must be narrow enough to prevent large particles from passing through yet wide enough not to become blocked and prevent flow altogether.It is a good idea for the slots or holes to be wider on the under-side than on the top side to prevent particles that pass through the screen from plugging the gaps.some manufacturers mill slots into the screens and mill the underside wider .others choose to construct the screens with V-shaped or wedge,wire laid out in strips separated by an appropriate distance. In general the total open area of the false bottom is above 11%. And the distance between false bottom and tank bottom is 15cm-16cm.

Here is drawings of false bottom:

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

We can calculate the Lauter tun diameter according to malt capacity.
Generally, The dry malt after milled and add water, the spent grain volume will expand to 1.65~1.8times.
For example 1000L brewing system ,according to malt:water=1:4  ,and the malt is 200kg.
For 200kg malt, the final spent grain will be 0.2x1.8=0.36m³
Ideally, the spent grain bed thickness is between 30cm-40cm for easy filtering.Let set it 35cm.
The spent grain volume is 0.36m³
Πr² x 0.35m=0.36m³

By this formulas, we can get R=0.57m
The diameter 0.57x2=1.14m and the outer diameter 1.14m+0.16m=1.3m
If the malt is bigger than 1:4, for example 1:3, the lauter diameter will expand accordingly.

There are different bottom type for lauter tun.
From volume,for lauter tun under 2000L with cone bottom ,while above 2000L ,the lauter tun with flat bottom. The reason is that there usually independent lauter tun for system above 2000L.
For lauter tun with with extended collection rings and Back pressure flushing device , the lauter tun with flat bottom.

Accordingly, with different bottom, the support under false bottom is different. The first picture is the support for lauter tun with cone bottom, and the second is the support for false bottom in flat lauter tun.

Except the above support for false bottom, there is also nut fix the false bottom with tank bottom as there is large compact on grain bed . How to take out of false bottom?
See the below pictures, we can use cross screwdriver to open the nut and remove it , screw on the small handle as the second picture and lift the false bottom plate, and then we can take out the others. The same way like sector false bottom.

Thanks for your reading.
Edited by Helen
Sales manager

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