<p>The system has a wear-resistant floating body e.g. metallic floating body, floatable on a medium in an operating mode of the system as long as a density of the medium is changed such that the body is downwardly moved and an outlet for the medium containing solid materials is blocked. The body is held in the medium in a sealing position till pressure balance is achieved by a back pressure of the medium. The body is made of ceramic. The ceramic body is harder than the solid materials contained in the medium.</p>
