Gaskets, rubber bellows,O-rings and wedges provide sealing between the seal ring and shaft (or housing) and the mating ring and shaft (or housing). The secondary sealing element for the mating ring is always static axially (although it may be rotating). Secondary sealing elements for the seal ring are described as being either pusher or non-pusher in the axial direction. The term pusher is applied to secondary seals that must be pushed back and forth by the movement of the shaft or primary ring whereas non-pusher secondary seals are static and associated with bellows seal rings.
