Springs and metal bellows are subjected to high stress. Too much spring or bellows movement will cause an early fatigue of the metal. Some elastomers do not move to a clean surface as the face wears. Spring loaded elastomers stick to the shaft or sleeve and are sensitive to the shaft diameter and finish. Elastomers positioned in the seal face are subject to the heat generated between the seal faces.
Dynamic elastomers are very sensitive to the shaft tolerance and finish.
Operating conditions too severe for the design. Elastomers and some seal faces are sensitive to temperature extremes. Excessive pressure can distort seal faces causing them to go out of flat. Excessive pressure can cause elastomer extrusion. High speed can separate the seal faces in rotating seal designs.