Agitator Motors for 500L Fermentation Tanks

An agitator motor on a 500L tank is not there to make the beer look busy. It serves specific process goals: keeping yeast in suspension during active fermentation, improving heat transfer across the cooling jacket, and blending additions without introducing oxygen. In carbonated beverage work, it also helps hold dissolved CO2 evenly and prevents solids from settling in the cone.

Most calls we get about this size come from brewpubs, small craft breweries, and beverage producers running pilot or mid-size batches. They have often already tried a gearmotor sized for water and found it either stalls on high-gravity wort or whips the product into foam. Matching the motor to the actual viscosity, batch size, and tank geometry matters more than picking the highest torque number on a spec sheet.

Material and Build Details

We machine the motor mounting flange, shaft, and impeller from 304 or 316L stainless depending on the customer\’s cleaning chemistry and chloride exposure. 316L is the usual choice where aggressive CIP with caustic and acid is routine, or where the tank sits in a humid coastal environment. 304 works fine for many inland breweries running standard CIP cycles.

Shaft seals are a wear item. We use a double mechanical seal with a sanitary flush port on most beer and beverage units, so product does not migrate into the gearbox. Welds on the shaft and impeller are ground flush and passivated. Surface finish inside the tank is typically 0.8µm or better for product contact. The motor frame is IP55 or IP65 depending on washdown practice, and the gearbox is sized with a service factor above 1.5 for the actual torque demand.

Matching Motor to Tank

A 500L tank with a 2:1 height-to-diameter ratio behaves differently from a squat 500L unit with a large cooling jacket area. For standard ales, a 0.37–0.75 kW gearmotor with output speed in the 20–60 rpm range is common. Lagers or high-gravity worts may need more torque at lower speed. Variable frequency drives are worth including from the start; they let operators slow the agitator during crash cooling and avoid shear damage to yeast.

Technical Specifications

FAQ

Will one motor design fit all 500L tanks? No. Tank diameter, liquid height, and whether you run ales or lagers change the torque and speed requirement. Send us the tank drawing.

Can I retrofit an agitator to an existing tank? Often yes, if the top manway or dedicated port has enough clearance and the tank wall can take a mounting flange. We need the port size and head thickness.

How do I clean around the shaft seal? The flush port on the mechanical seal lets you run CIP solution or sanitizer through the seal area without pulling the motor.

Do I need a VFD? For beer and carbonated beverages, yes in most cases. It prevents vortexing at high speed and lets you match agitation to the fermentation stage.

Tell us your batch size, beer type, number of fermentation tanks and available space. We can recommend the tank volume, cooling area and configuration for your brewery.