Valve stem packing structure

A packing structure for use in a valve having a valve body with a fluid flow passage, a valve element mounted for movement between an open position and a closed position relative to the flow passage, and a movable valve stem connected with the valve member and extending through a valve stem bore in the valve body and a packing chamber formed by an enlargement of said bore for effecting movement of the valve element between the open and closed positions, said packing structure comprising:

• a first lower set of packing rings arranged within said bore enlargement in stacked coaxial relationship about said valve stem;
• a second upper set of packing rings arranged within said packing chamber in stacked coaxial relationship about said valve stem, said packing chamber including a lower packing stop provided in said bore and at its upper end an upper packing stop provided in said bore;
• spring means in said packing chamber in a space between said upper and lower sets of packing rings for exerting a force for axial compression of said lower set of packing rings against said lower packing stop and a force for axial compression of said upper set of packing rings against said upper packing stop to thereby urge the radial expansion of said packing rings and provide an enhanced substantially uniform sealing effectiveness of the packing rings, said spring means comprising at least one spring washer of frusto-conical configuration positioned between said retainer rings in encircling sleeved relation with said valve stem for exerting an axially compressive force on each set of packing rings;
• said valve bonnet being provided with a port formed by a passage through the wall thereof which communicates with said spring means in said packing chamber in the space between said upper and lower sets of packing rings, and a pressure fitting provided in the outer end of said passage for allowing the detection of fluid leakage past said packing rings into said space or the selective pressurized injections of a sealing material or fluid into said space;
• at least one of said spring washers being provided with a notch therein allowing communication between said port and the annulus defined by the valve stem and the inner surfaces of said frusto-conical washer and between said port and the annulus defined by the wall of said valve stem bore and the outer surfaces of said spring washers whereby said pressurized sealing material is allowed to fill said annuluses to enhance the uniform sealing effectiveness of the packing rings;
• and
• means for axially compressing said upper and lower sets of packing rings and said spring means for preloading both sets of said packing rings and for inducing an internal spring loaded force for axial compression of said sets of packing rings.