Abstract: A device for separating tramp metals from liquid raw materials includes a body unit, a holding unit, a magnetic unit, a rinsing unit, and a driving unit. The body unit includes a tank for feeding-in and feeding-out liquid raw materials. The holding unit is coupled to the tank and includes and a plurality of non-magnetic holders received in the tank. The magnetic unit is mounted on the tank and includes an enclosure haying a telescopic wall to be in a compressed or extended state. The rinsing unit is fixed on the interior of the tank to rinse the non-magnetic holders. The driving unit is coupled the tank and the magnetic unit for driving the magnet unit moving between a first and second positions. An assembly is assembled from the device. And a method is carried out by the device or the assembly.