Method for monitoring and controlling the operation of a flow generator

A method for monitoring and controlling the operation of a liquid flow generator configured for operation in a tank housing in a liquid comprising solid matter, the flow generator comprising a propeller and a main body having a drive unit, wherein the drive unit comprises an electric motor located in said main body and a drive shaft connected to the electric motor and extending from the main body, wherein the propeller comprises a hub and a plurality of blades (14) connected to said hub, wherein the hub is connected to the drive shaft and driven in rotation by said electric motor during operation of the flow generator, a control unit being operatively connected to the flow generator in order to monitor and control the operation of the flow generator, the method comprises the steps of:

• a) driving the propeller in a normal direction of rotation in order to generate a bulk flow of liquid in the tank, wherein the liquid flow is directed from an upstream side of the propeller towards a downstream side of the propeller, wherein the main body is located at the upstream side of the propeller,
• b) performing a cleaning sequence in response to a main body cleaning signal, wherein the cleaning sequence comprises the steps of:
• i) stopping the propeller from rotating in the normal direction of rotation,
• ii) driving the propeller in a reverse direction of rotation in order to generate a local flow of liquid from the downstream side of the propeller towards the upstream side of the propeller and along the main body in order to remove any solid matter accumulated on the main body, and
• iii) stopping the propeller from rotating in the reverse direction of rotation,
• c) resume driving of the propeller in the normal direction of rotation,
• wherein the duration of the reverse operation of the propeller during the cleaning sequence is equal to or more than 5 seconds and is equal to or less than 60 seconds, and
• wherein the rotational speed of the flow generator during the reverse operation of the propeller during the cleaning sequence is equal to or more than 25 % of the max rotational speed of the flow generator and is equal to or less than 100 % of the max rotational speed of the flow generator.