Washing machine model Robus cleans the inside of round tanks by means of a highly efficient brush while also washing with a solvent or cleaning agent. The rotating brush is equipped with arms that open by centrifugal or mechanical force, depending on the model, thereby automatically adapting to the size of the container. At the same time the brush travels up and down, ensuring an effective and efficient cleaning of the inside surfaces. With optional nitrogen purging and other safety-related details, the machine meets the highest standards of explosion proof design.