Packing gland assembly

In a high pressure valve having a valve body presenting a fluid flow passage therethrough for receiving a pressurized working fluid, a valve member 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 to effect movement thereof between the open and closed positions, the improvement comprising:

• a bonnet on the valve body and having a bore therethrough which receives the valve stem;
• a packing chamber provided in the valve stem receiving bore and being defined by an annular space provided by an enlargement of said bore, said packing chamber terminating at its lower end in a packing stop provided by an annular shoulder in the bore facing away from the flow passage and at its upper end by a packing stop provided by a retainer ring mounted in said bore;
• a packing assembly in said packing chamber, said packing assembly consisting of a first lower set of packing rings, each of said packing rings being of a polymeric composition and of the V-type configuration in radial cross-section with a convex surface and a concave surface, said packing rings being arranged in internested relationship in a stack about the valve stem in contacting relationship with the stem and bonnet;
• a second upper set of packing rings, each of said packing rings in said upper set being of a polymeric composition and of the V-type configuration in radial cross-section with a convex surface and a concave surface, said upper set of packing rings being arranged in an internested stacked relationship about the valve stem in contacting relationship with the stem and bonnet, said upper and lower sets of packing rings being disposed in said packing chamber with all the concave surfaces of the upper sets of packing rings facing in the direction of fluid pressure from said flow passage;
• a pair of anti-extrusion rings arranged about the valve stem at opposite ends of the stack of the lower set of packing rings to sandwich the packing rings of said lower set between said pair of anti-extrusion rings;
• a third anti-extrusion ring arranged about the valve stem and disposed atop the stack of the upper set of packing rings, said anti-extrusion rings contacting the stem and bonnet and being formed of a non-metallic, harder, more rigid substance than said packing rings with a yield strength which exceeds the expected working pressure for the valve in the range of 25% to 50% and corresponds to the test pressure for the valve to permanently deform said anti-extrusion rings to impede extrusion of the packing rings along the stem and bonnet when said packing rings are subjected to axial compression;
• a soft, plastic sealing material interjected in the packing chamber between said upper and lower sets of packing rings;
• and a fitting means provided in said bonnet and communicating with said packing chamber for selective injection of an additional quantity of said soft, plastic sealing material between said upper and lower sets of packing rings to axially compress the packing assembly and induce a radial expansion of said packing rings to effect a tight, sealing relationship between said packing rings and said valve stem and bonnet.