Fermentation Tank

Overview

A fermentation tank, often called a unitank or cylindro-conical vessel, is where brewers convert sugary wort into beer. Yeast pitched into cooled wort consumes fermentable sugars and produces ethanol, carbon dioxide, and a range of flavor compounds. The tank holds this process under controlled temperature and pressure for one to four weeks, then serves as the vessel for cold conditioning, yeast harvesting, carbonation, and racking the finished beer to a brite tank or packaging line. The defining feature is the conical bottom, which lets settled yeast and trub collect at the lowest point where they can be drawn off through a single valve.

The vessel is built from 304 stainless steel with 316L used at wetted welds for corrosion resistance against acidic wort and aggressive cleaning chemicals. Interior surfaces are polished to a 320 grit or 2B finish so that no crevices harbor bacteria. Glycol jackets bonded to the exterior remove the heat that active fermentation generates, which for a vigorous ale can reach several degrees per hour if left unchecked. The whole assembly sits on a Support Stand tall enough to clear racking lines and a yeast collection bucket under the cone.

Vessel construction

The Tank Vessel is the pressure-bearing core. A rolled Cylinder Shell forms the straight body, capped by a Dished Top Head and closed below by a Cone Bottom set at 60 to 72 degrees. A steeper cone sheds yeast faster but raises the overall tank height, so cellar ceiling clearance usually decides the angle. A Manway gives access for inspection and manual cleaning of stubborn deposits, and two Thermowell pockets let probes read wort temperature without piercing the sanitary boundary. The Racking Port sits above the yeast bed so clear beer can be drawn while sediment stays in the cone.

Cooling and temperature control

Fermentation is exothermic, so every tank carries a Cooling Jacket Assembly made of dimple plate welded to the shell. Glycol chilled to roughly 26 °F circulates through a Cone Jacket and one or more Cylinder Jacket sections. Splitting the jacket into zones lets the brewer crash the cone to drop yeast while holding the upper beer at a different temperature, or vice versa. The Temperature Control Assembly assembly closes the loop: a RTD Probe feeds a Temperature Controller that opens a Glycol Solenoid Valve whenever the beer drifts above setpoint. A typical ale ferments at 64 to 68 °F, a lager nearer 50 °F, and cold crashing pulls the whole tank to 32 to 34 °F to settle yeast and haze before packaging.

Pressure and carbonation

Closed fermentation lets the brewer capture carbon dioxide rather than vent it. The Pressure Control Assembly assembly centers on a Spunding Valve, an adjustable back-pressure regulator that holds the headspace at a chosen pressure so the beer carbonates naturally during the final days of fermentation. A Pressure Relief Valve protects against both overpressure and the vacuum that forms when a warm full tank is suddenly chilled. For tanks that finish carbonation under gas, a Carbonation Stone diffuses fine CO2 bubbles into the beer, and a Pressure Sensor with a Pressure Gauge tracks headspace pressure. Design pressures of 15 to 45 psi cover both gentle spunding and force carbonation.

Cleaning and sanitation

Because the vessel never comes apart between batches, cleaning happens in place. The CIP System pumps caustic, then acid, then a final rinse through a CIP Spray Ball mounted at the top head. The fluid sheets down every interior surface and drains through the cone to the CIP Return Line. A static spray ball relies on flow rate and pattern coverage, while a rotary head gives mechanical impact for heavier soils. Sanitary Butterfly Valve units and an O-Ring Set of food-grade gaskets close off the process lines during cleaning so chemicals do not reach the wrong circuit.

Valves and beer handling

The Valve Set handles every liquid transfer. A Bottom Dump Valve at the cone tip dumps settled yeast, which many breweries harvest and repitch into the next batch. The Racking Arm swivels up out of the sediment during fermentation and down to draw clear beer when transferring out. A Sample Valve lets the brewer pull gravity and taste samples through a flamed port without introducing wild yeast or bacteria. All connections use tri-clamp fittings so they can be broken, gasketed, and reassembled quickly.

Materials, variants, and use

Most craft fermenters are jacketed unitanks in the 10 to 60 hL range, but the same architecture scales from a 5 hL pilot tank to a 600 hL production vessel where the cone alone is taller than a person. Single-zone glycol jackets suit small tanks, while large vessels need separate cone and body zones to crash uniformly. Insulation, a Polyurethane Insulation layer under stainless Cladding Panel cladding, keeps glycol consumption down in warm cellars. Horizontal maturation tanks exist for lagering, but the vertical cylindro-conical design dominates because it ferments, conditions, harvests yeast, and carbonates in one vessel, cutting the number of transfers and the contamination risk that comes with each one.