A method for detecting excessive wear of a wearing part, which wearing part: a) is a dynamic sealing or gasket either consisting primarily of, or being covered at least partially by a sliding layer consisting primarily of, a polymer material such as PolyTetra Flour Ethylen (PTFE), Polychlorotrifluoroethylene (PCTFE), Perfluoroalkoxy, Tetrafluorethylene-perfluoropropylene, ETFE, FEP, LCP, Chlorotrifluoroethylene (E-CTFE), PE, PEEK, PET, PVDF, THV and/or the like, and b) comprises optical fibers interconnected by means of splitters or reflectors and fitted in, embedded in, indented in or fused with said polymer material, of which: - at least one first optical fiber that is in its proximal end connected to a proximal light detecting device, consisting of a lens made from semi-transparent material, which emits visible light when light is emitted from a light emitting device into the proximal end of said at least one first optical fiber, and - at least one second optical fiber that is in its distal end connected to a distal end light detecting device, consisting of a lens made from semi-transparent material, which emits visible light, when light, emitted from said light emitting device into said proximal end of said at least one first optical fiber, is emitted from the distal end of said at least second optical fiber, and which wearing part and optical fibers are further defined in that c) light emitted from said light emitting device into said proximal end of said at least one first optical fiber, has travelled either along the entire circumference of said wearing part, or has traversed the entire length of said wearing part, through said optical fibers, when emitted from the distal end of said at least second optical fiber, and d) the distance travelled by said light along said entire circumference of said wearing part, or when traversing said entire length of said wearing part, between said proximal end of said at least one first optical fiber, and said distal end of said at least second optical fiber is at least 500 mm, and, which method comprises at least the following steps: - turning on said light emitting device, - inspecting whether said proximal and said distal light detecting devices emit visible light, and - concluding that said wearing parts are not subject to excessive wear if both said proximal and said distal light detecting devices emit visible light. a) is a dynamic sealing or gasket either consisting primarily of, or being covered at least partially by a sliding layer consisting primarily of, a polymer material such as PolyTetra Flour Ethylen (PTFE), Polychlorotrifluoroethylene (PCTFE), Perfluoroalkoxy, Tetrafluorethylene-perfluoropropylene, ETFE, FEP, LCP, Chlorotrifluoroethylene (E-CTFE), PE, PEEK, PET, PVDF, THV and/or the like, and b) comprises optical fibers interconnected by means of splitters or reflectors and fitted in, embedded in, indented in or fused with said polymer material, of which: - at least one first optical fiber that is in its proximal end connected to a proximal light detecting device, consisting of a lens made from semi-transparent material, which emits visible light when light is emitted from a light emitting device into the proximal end of said at least one first optical fiber, and - at least one second optical fiber that is in its distal end connected to a distal end light detecting device, consisting of a lens made from semi-transparent material, which emits visible light, when light, emitted from said light emitting device into said proximal end of said at least one first optical fiber, is emitted from the distal end of said at least second optical fiber, and which wearing part and optical fibers are further defined in that - at least one first optical fiber that is in its proximal end connected to a proximal light detecting device, consisting of a lens made from semi-transparent material, which emits visible light when light is emitted from a light emitting device into the proximal end of said at least one first optical fiber, and - at least one second optical fiber that is in its distal end connected to a distal end light detecting device, consisting of a lens made from semi-transparent material, which emits visible light, when light, emitted from said light emitting device into said proximal end of said at least one first optical fiber, is emitted from the distal end of said at least second optical fiber, c) light emitted from said light emitting device into said proximal end of said at least one first optical fiber, has travelled either along the entire circumference of said wearing part, or has traversed the entire length of said wearing part, through said optical fibers, when emitted from the distal end of said at least second optical fiber, and d) the distance travelled by said light along said entire circumference of said wearing part, or when traversing said entire length of said wearing part, between said proximal end of said at least one first optical fiber, and said distal end of said at least second optical fiber is at least 500 mm, - turning on said light emitting device, - inspecting whether said proximal and said distal light detecting devices emit visible light, and - concluding that said wearing parts are not subject to excessive wear if both said proximal and said distal light detecting devices emit visible light.