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SOP — Lautering

FUERST WIACEK Version 1.0 | Brewhouse — mash transfer, lautering, deep cuts | Frequency: per brew

Purpose

This SOP covers the mash transfer and the lauter run: what the vessel can do, what a deep cut is, why cuts happen, and which numbers to read when a run goes wrong.

Setpoints live in the Botec recipes, not here. The values on this page are the current figures as of the version date, recorded for reference and reasoning. If a number here disagrees with the recipe, the recipe is right — and this page should be corrected.

Brew-day sequence and sampling are in the Brew Day Execution SOP. Vessel specification is in Brewhouse Reference.

The vessel and its design basis

The Läuterbottich (lauter tun) is a Krones CombiCube unit: Ø2.000 mm inner, 3,14 m² false-bottom area, 55 hl gross / 18 hl net, milled Senkboden with 14% free open area, six Läuterrohranstiche into six collecting pipes (Lieferumfang p. 17–21).

Krones designed it for 174 kg/m² at 12 °Plato with dry-milled grist — about 546 kg of grist per brew.

Warning

FUERST WIACEK brews above that design basis. Median original gravity is 15,3 °P against the specified 12, and the 575, 600 and 650 kg grists load the bed at 105–119% of 174 kg/m². That is a deliberate product decision, not drift — but it is why deep beds have little margin and thin beds have plenty.

Bed loading by grist

Grist kg/m² % of design Bed depth (derived)
750 kg 239 137% ~480 mm
650 kg 207 119% ~410 mm
600 kg 191 110% ~380 mm
575 kg 183 105% ~350 mm
500 kg 159 91% ~320 mm
450 kg 143 82% ~285 mm
375 kg 119 69% ~240 mm
350 kg 111 64% ~225 mm
250 kg 80 46% ~160 mm

Every deep-cut incident in August 2026 happened at 191 kg/m² or above. Every clean run in the same period was at 119–143 kg/m². The thin-bed programmes have never had a lautering problem.

Deep cuts

A deep cut is a corrective action, not a step. The rakes drive down into the bed to break it open when differential pressure has risen past what the runoff can sustain. It works — flow recovers immediately — but it is the machine reporting that the bed cannot deliver the flow being asked of it.

Cuts cascade. After a cut the bed re-settles denser than before, so the next cut arrives sooner and has to go deeper. That is how one cut becomes many, and it is why intervening early and gently beats intervening late and hard.

What a cut costs. It tears fines, husk particles and lipids into the wort, and on a 30-minute boil there is less opportunity for that material to coagulate and drop out. It does not measurably cost extract — 52 brews were checked in August 2026 and cut count explains none of the variation in extract per kilo of grist once programme is accounted for.

Note

Normal is ZERO deep cuts. One is already unusual. If a brew cuts more than once, something has changed — check the grist, the wort viscosity and the recent lauter parameters before accepting it.

Rake heights

Height is measured up from the false bottom. The knives should ride in the top quarter of the bed during normal running, descend through the upper half as differential pressure rises, and never enter the bottom third — that is the fine filter layer which does the actual filtration. Cutting into it gives turbid wort and a bed that re-settles tighter than before.

Grist Raking Height Minimum Height Maximum Height
750 kg 360 mm 160 mm 380 mm
650 kg 310 mm 140 mm 330 mm
600 kg 290 mm 130 mm 310 mm
500 kg 240 mm 105 mm 260 mm
450 kg 215 mm 95 mm 235 mm
375 kg 180 mm 80 mm 200 mm
350 kg 170 mm 75 mm 190 mm
250 kg 120 mm 55 mm 140 mm

Warning

These heights are DERIVED, not measured. Bed depths come from about 2 litres of settled bed per kg of grist over 3,14 m² — a standard design figure which reproduces the Krones 174 kg/m² basis at a 350 mm bed, but which has never been measured in this tun. To make them exact: at the end of a run, note the lauter tun level percentage at which the bed surface first appears. The level probe is a 1000 mm Stabsonde, so that reading gives bed depth directly. Correct this table once that measurement exists.

Do not set the nominal height above the bed surface. Knives floating clear of the bed do nothing, and re-entry disturbs more than continuous shallow work would have.

Raking speed

The Aufhackmaschine (rake machine) has 2 arms with fixed knives (feststehende Messer), driven at 2,6 kW. Specified raking speed runs from 0,104 rpm minimum up to 10,4 rpm for spent-grain discharge. The lift gear is 0,75 kW at 233 mm/min, with 4 range limit switches and 2 safety limit switches (Lieferumfang p. 20–21).

Normal raking is slow — a few minutes per revolution. Faster raking is more shear and more fines for no gain.

Flow and the control loop

The runoff is a ramp, not a single rate. Second wort starts around 7 hl/h, rises to roughly 8,5, then rises again toward the ceiling for the last and longest stretch.

The mash pump is rated 70 hl/h and the recipes cap flow at 16. Nothing about the flow ceiling is pumping — it is bed permeability.

The parameters that matter

Parameter What it does
Minimum Flow Rate The floor the controller fights to hold. When the bed cannot deliver it, the knives go down.
Maximum Flow Rate The ceiling the ramp climbs toward.
Delay Trending How long the controller waits before pushing flow up.
Valve Control Time Cycle How often the control valve is adjusted.
Deep Cut Lock Volume remaining below which cutting is forbidden.
Max. Opening Valve How far the valve had to open — the direct read on bed permeability.

Note

The August 2026 finding: softening the ramp stopped the cuts without slowing the lauter. Raising Delay Trending from 120 to 180 s and Valve Control Time Cycle from 120 to 200 s took a grist that had cut heavily on four consecutive batches down to zero cuts — while still reaching 15,9 hl/h against a 16,0 ceiling. The controller was not too fast; it was too abrupt.

Hunting versus saturation — they look similar and need opposite treatments. If flow swings above and below setpoint while the valve moves up and down, that is hunting, and the delay parameters help. If flow sits persistently under setpoint while the valve only ever climbs, the controller has run out of authority — delay changes nothing, and the answer is to lower Minimum Flow Rate, raising the step watchdog to match, or to reduce the demand.

The mash transfer

Transfer runs the agitator down from 80% to 30% as the vessel empties, with the mash pump ramping toward 95%. Two rinses follow the bulk transfer — one during it, triggered on level, and one after. Rinse volumes are set by time, not by volume.

Warning

Above roughly 50% the mash mixer creates a vortex that makes the level sensor read empty. That can end a step early and leave mash in the tun. Never raise agitator speed at low level to move a sticky mash — add water earlier instead. A false empty shows on the trend as an abrupt drop to the trigger level; a genuine one declines smoothly.

High-oat grists leave residue. Malted oats carry their own husk, which is long and fibrous and mats across restrictions — that is a transfer problem, not a bed-permeability problem. Rice hulls are unnecessary; the oats already supply the filter material.

Rinse water is not sparge water. Rinse water enters before lautering and dilutes the mash; sparge water percolates down through the bed and washes extract out of it. When rinse volume is increased, check whether the sparge self-compensates on its total-wort target before reducing it by hand — reducing both is how a rinse change becomes a yield loss.

What to record

  • First wort gravity and pH (VZ) — the most direct available read on bed condition. Clean runs sit noticeably higher than struggling ones on the same recipe.
  • Deep cut count — into the batch note. There is no automatic record of cuts anywhere in the estate.
  • Anything unusual in the mash tun — residue left behind, clumps, sticky material.

Note

The Botec BatchReport is the only source of sub-daily lauter data. It carries each phase with its start and duration and, for every parameter, three rows: RN = what the recipe holds, N = what was actually set, A = what was achieved. If RN and N disagree, someone typed an override on the day and it will not persist to the next brew.

Troubleshooting

Symptom Likely cause Action
Repeated deep cuts, flow below setpoint, valve climbing steadily Controller saturated — the bed cannot meet Minimum Flow Rate Lower the flow floor and raise the step watchdog to match. Delay changes will not help.
Cuts increasing brew over brew on the same recipe Wort viscosity has risen — check for a malt lot change, especially wheat Compare first wort gravity against the same recipe historically
Mash left in the mash tun after transfer Rinses too short, or a vortex-induced false empty Lengthen the rinses; check the level trace for an abrupt drop
Sticky clumps in the mash, unconverted starch Acid pocket at mash-in See Mash Additions — check when the acid dose fires relative to grist arrival
Turbid wort into the kettle Cutting into the bottom third of the bed Raise the minimum rake height