Centrifugal pump unit and method for moving a valve element in a pump unit

A method for moving a valve element which is arranged in a centrifugal pump assembly, said valve element being arranged and configured such that the valve element is movable from a switching position into a second switching position by way of a flow which is produced by the impeller of the centrifugal pump assembly and that at least one section of the valve element is movable from a released position into a bearing position, in which the at least one section of the valve element is fixed on a contact surface, by way of pressure which is produced by the impeller, the method comprising the steps of:

• reducing the speed or switching off a drive motor, by which means the pressure at the outlet side of the impeller is reduced to such an extent that the valve element or the at least one section of the valve element gets into the released position and the valve element is moved from a first into a second switching position by way of the flow which is produced by the impeller;
• increasing the speed or switching on the drive motor, so that the pressure at the outlet side of the impeller is increased to such an extent that the valve element or the at least one section of the valve element is moved into the bearing position.