Lauter tun calculator for false bottom sizing

How the lauter tun calculator works

The false bottom area of a lauter tun follows from the grist mashed in each brew and the specific loading of the grain bed. The calculator works out the area, the tun diameter, the open area of the false bottom and the number of segments needed to pass through the manway.

1. False bottom area = grist per brew / specific grain bed loading. Loadings of 150 to 220 kg per square metre are typical, and 175 is the default.
2. Tun inside diameter = square root of (4 x area / pi).
3. Open area: OA = S / (S + W), from the slot and the profile wire width, so the open area in square metres is the false bottom area x OA.
4. Segments: the false bottom is made in segments small enough to pass the manway, estimated as the larger of 2 and pi x D / (2 x manway diameter), rounded up.

Worked example

A brewhouse mashing 1,000 kg of grist at 175 kg per square metre needs about 5.71 square metres of false bottom, which corresponds to a tun about 2.70 m across. A 0.7 mm slot on 18SB wire (1.8 mm) gives 28 percent open area, or 1.6 square metres of opening, and a 500 mm manway gives an estimate of 9 segments.

Reading the result

The figures are a starting point for engineering. The slot is confirmed for the mill and the grist, and the support structure is designed so that each segment stays flat to within 1 to 2 mm under the wet grain bed.

The lauter tun false bottom guide covers slot choice and support, and lauter tun false bottoms describes how SIMO Screens builds them.