| 摘要 |
A packing assembly for a valve stem, or the like, comprising two groups of "V"-shaped packing rings, "G" and "H", disposed about the valve stem 16 in a stuffing box 32 provided in the stem receiving bore in the vavve body or bonnet 12. Semi-fluid plastic material 69 is injected between the two groups of packing rings to move them apart and thereby axially compress and radially expand the packing rings into sealing engagement with the valve stem and stuffing box wall. The lower group of packing rings is provided with a pair of non-metallic back up adapter rings at its lower and upper ends. A similar back up adapter ring is provided at the top of the upper group of packing rings. The back up adapter rings 61, 62, 68 serve to stabilize the packing structure. They also serve as stem centralizing rings to preclude galling and scarring of the stem and as anti-extrusion rings to impede extrusion of the packing rings along the stem and bonnet. The upper adapter ring of the lower group also prevents the passage of injected plastic material to the lower group packings and thereby prevents their possible distortion and collapse during installation for sealing.
|
