Valve stem packing system

In a valve including a valve body defining a valve chamber with a valve element mounted therein for controlling flow between inlet and outlet ports, and a cylindrical stem operatively connected to the valve element and extending out of the valve chamber through a cylindrical passageway, the improvement comprising:

• a first counterbore in the cylindrical passageway;
• a first packing assembly carried by the body and positioned in the first counterbore about the stem for sealing the valve chamber;
• a first adjustable packing nut adjustably received in first threads disposed within a second counterbore in the cylindrical passageway and located about the stem axially outwardly of the first packing assembly for applying adjustable compressive loading thereto;
• a second packing assembly carried by the first packing nut and encircling the stem at a location axially outward of the first packing assembly;
• a second adjustable packing nut carried in threads formed in the first packing nut and located about the stem axially outwardly the second packing assembly for applying adjustable compressive loading thereto;
• and,
• seal means disposed at a lower end of the first adjustable packing nut adjacent the first packing assembly sealing between the first packing nut and the second counterbore at a location between the threads which carry the first packing nut and the first packing assembly to provide a sealed chamber between the first and second packing assemblies such that leakage through the first packing assembly cannot pass through the first threads in the second counterbore in the cylindrical passageway.