Valve vented redundant stem seal system

A valve stem packing assembly for sealing a valve stem to a valve body having a body cavity, the packing assembly comprising:

• a first spring energized seal ring positioned within a valve stem opening extending axially through the body to seal the valve stem to the valve body, the first seal ring comprising:
• a chevron profile defining a first and a second leg extending radially outward from an interior radius defined in an apex of the chevron profile, the first and second legs sealing the stem and the body to opposing annular surfaces;
• a bump formed on an outer surface of the first seal ring opposite an end of the seal ring that seals to the valve stem and the valve body, the bump forming one or more fluid channels, allowing fluid to vent past the sealing surface of the first seal ring;
• and
• an annular seal standoff having a first end and a second end, wherein the first end is positioned on a supportive shoulder of the stem seal assembly and the second end inserts into the interior radius defined in the apex of the chevron profile to support the chevron profile on the standoff;
• a second seal ring positioned within the valve stem opening to seal the valve stem to the valve body;
• and
• a load ring assembly mounted to and forming a part of the body having a first end in engagement with the first seal ring and a second end in engagement with the second seal ring, such that an axial force applied to the first seal ring transfers to load ring assembly, an axial force in an opposite direction on the second seal ring transfers to the load ring assembly.

A seal for a valve stem comprising:

• an annular seal stand off having a first end and a second end;
• a seal ring having a chevron profile positioned on the seal standoff so that the second end of the seal stand off inserts into the chevron profile;
• wherein the seal ring defines a first and a second leg extending from an apex of the chevron profile radially outward, the first and second legs sealing to opposing annular surfaces of the valve stem and a valve body;
• an energizing spring having a chevron profile interposed between the seal stand off and the seal ring, the energizing spring exerting an expanding force on the legs of the seal ring so that the seal ring will remain in sealing contact with the opposing annular surfaces;
• wherein the energizing spring may be deflected in response to a fluid pressure on the seal ring opposite the energizing spring to allow fluid flow past the seal ring;
• a back ring having a chevron channel that receives an apex of the seal ring, the back ring having a greater stiffness to radial movement than the first and second legs of the seal ring to limit radial deformation of the first and second legs of the seal ring;
• wherein the first end of the seal stand off has a substantially flat portion positioned on a supportive shoulder of the packing assembly and the second end of the seal stand off is in operative engagement with the chevron profile;
• wherein the seal ring is formed of a polymer and the back ring is formed of a polymer having a greater hardness than the polymer of the seal ring;
• wherein the channel of the back ring extends only partially to distal ends of each leg of the seal ring;
• wherein a width of the back ring is smaller than a distance between outer sides of the distal ends of the seal ring legs;
• wherein an inner gap is located between the back ring and the stem and an outer gap is located between the back ring and the valve body;
• wherein the channel of the back ring extends from the apex of the se& ring over only part of the seal ring;
• and
• a plurality of circumferentially spaced apart bumps formed on an outer surface of the back ring, defining a plurality of fluid channels so that fluid may vent past the sealing surface of the seal ring.