FLENDER Gear Units for Aerators


An aerator is an impeller in the biological part of a sewage treatment plant. It swirls the surface of the water so that it is enriched with oxygen. This activates the bacteria, so that the biodegradable constituents are removed from the sludge.

The impeller is fixed to the gear unit output shaft, which is extended vertically downward, a certain distance from the gear unit. To prevent the clarified water from becoming contaminated with gear oil, FLENDER gear units are designed with an output shaft featuring an oil retaining tube and a non-contacting, non-wearing shaft seal.

The axial and lateral loads resulting from the process are absorbed by extra-heavy-duty output shafts and output bearings.

Technical data


Helical and bevel helical gear units



Gear stages

2- and 3-stage

Power ratings

up to 3,600 kW

Transmission ratios

i = 6.3 to 112

Nominal torques

10.5 to 173 kNm

Mounting positions



  • Oil pressure lubrication with flanged-on pump

  • Reinforced bearings

  • Dry well design (shaft seal is absolutely oil-tight)

  • Coupling flange for mounting the aerator

  • High operational reliability

  • Low noise level

  • High efficiencies


  • Wastewater treatment