Low diffusivity barrier fluid packing system
In accordance with the present invention, there is provided a fluid or liquid barrier packing system which is adapted to minimize VOC emissions, while also providing live-loading and continuous load monitoring functions. The components of the packing system (including the liquid barrier) are adapted to be installed in a traditional stuffing box of a valve utilizing a top entry method, and without the necessity of having to inject the liquid through any side ports of the valve. The packing system reduces leakage levels as required by low emission leakage specifications by creating a reverse osmosis effect, limiting the diffusivity of a gas through the packing elements of the system. Thus, the packing system of the present invention provides a simplified method to load and monitor a barrier in the stuffing box of the valve to slightly higher pressure than processed fluid pressure.
1. A valve adapted to satisfy low fugitive emission leakage standards, the valve comprising:
a valve body defining a central passageway;
a valve stem advanced through and reciprocally movable within the passageway;
a packing system at least partially disposed within the passageway and including:
an annular upper packing which circumvents the valve stem and is disposed in fluid tight engagement to the valve stem and the valve body;
an annular lower packing which circumvents the valve stem and is disposed in fluid tight engagement to the valve stem and the valve body, the upper packing being separated from the lower packing by an annular gap which is further bounded by portions of the valve body and the valve stem;
a fluid barrier filled into the gap, the upper and lower packings and the fluid barrier collectively defining a seal of the packing system; and
a live-loading sub-assembly cooperatively engaged to the seal and operative to apply a load thereto in a manner which maintains the fluid barrier thereof at a prescribed fluid pressure level; and
an annular load sensor having a body which circumvents the valve stem and is positioned adjacent the upper packing.
2. The valve of claim 1 wherein the fluid barrier is a viscous liquid.
3. The valve of claim 1 wherein the live-loading sub-assembly of the packing system comprises:
a loading piston which circumvents the valve stem and is cooperatively engaged to the lower packing;
a retainer which circumvents the valve stem and is disposed in spaced relation to the loading piston; and
at least one biasing spring extending between the loading piston and the retainer, and operative to normally bias the loading piston toward the seal.
4. The valve of claim 3 wherein the live-loading sub-assembly further comprises a spacer which circumvents the valve stem and is interposed between the loading piston and the lower packing.
5. The valve of claim 1 wherein the packing system further comprises:
a packing follower which circumvents the valve stem and is abutted against the body of the load sensor;
the load sensor being operative to monitor the load applied to the seal of the packing system by the live-loading sub-assembly.
6. The valve of claim 5 wherein the packing follower comprises:
an annular upper section which is of a first outer diameter and disposed exteriorly of the valve body;
a tubular lower section which protrudes from the upper section and is of a second outer diameter less than the first outer diameter, the lower section being slidably advanced into the passageway and abutted against the load sensor; and
a central bore which extends through the upper and lower sections, and slidably accommodates the vale stem.
7. The valve of claim 6 wherein the packing follower further includes a passage which extends through the upper and lower sections thereof to the load sensor, the passage being sized and configured to accommodate at least one electrical wire extending from the load sensor.
8. The valve of claim 1 wherein the live-loading sub-assembly of the packing system comprises:
an upper spacer which circumvents the valve stem and is cooperatively engaged to the lower packing;
a lower spacer which circumvents the valve stem and is disposed in spaced relation to the upper spacer; and
at least one biasing spring extending between the upper and lower spacers, and operative to normally bias the upper spacer toward the seal.
9. The valve of claim 1 wherein the upper and lower packings are independently moveable relative to the valve body in an axial direction and are identically configured to each other, and each have a generally U-shaped cross-sectional configuration and define a continuous, annular channel, the upper and lower packing being oriented relative to each other such that the channels thereof communicate with the gap.
10. A valve adapted to satisfy low fugitive emission leakage standards, the valve comprising:
a valve body;
a valve stem reciprocally movable relative to the valve body; and
a packing system at least partially disposed within the valve body and including:
an upper packing which is disposed in fluid tight engagement to the valve stem and the valve body;
a lower packing which is disposed in fluid tight engagement to the valve stem and the valve body, the upper packing being separated from the lower packing by a gap which is further bounded by portions of the valve body and the valve stem;
a fluid barrier filled into the gap, the upper and lower packings and the fluid barrier collectively defining a seal of the packing system; and
a live-loading sub-assembly cooperatively engaged to the seal and operative to apply a load thereto in a manner which maintains the fluid barrier thereof at a prescribed fluid pressure level; and
a load sensor having a body which is abutted against the upper packing.
11. The valve of claim 10 wherein the fluid barrier is a viscous liquid.
12. The valve of claim 10 wherein the live-loading sub-assembly of the packing system comprises:
a loading piston which is cooperatively engaged to the lower packing;
a retainer which is disposed in spaced relation to the loading piston; and
at least one biasing spring extending between the loading piston and the retainer, and operative to normally bias the loading piston toward the seal.
13. The valve of claim 12 wherein the live-loading sub-assembly further comprises a spacer which is interposed between the loading piston and the lower packing.
14. The valve of claim 10 wherein the packing system further comprises:
a packing follower which is abutted against the load sensor;
wherein the load sensor is operative to monitor the load applied to the seal of the packing system by the live-loading sub-assembly.
15. The valve of claim 14 wherein the packing follower comprises:
an upper section which is disposed exteriorly of the valve body;
a lower section which protrudes from the upper section which is slidably advanced into the passageway and abutted against the load sensor; and
a central bore which extends through the upper and lower sections, and slidably accommodates the vale stem.
16. The valve of claim 15 wherein the packing follower further includes a passage which extends through the upper and lower sections thereof to the load sensor, the passage being sized and configured to accommodate at least one electrical wire extending from the load sensor.
17. The valve of claim 10 wherein the live-loading sub-assembly of the packing system comprises:
an upper spacer which is cooperatively engaged to the lower packing;
a lower spacer which is disposed in spaced relation to the upper spacer; and
at least one biasing spring extending between the upper and lower spacers, and operative to normally bias the upper spacer toward the seal.
18. The valve of claim 10 wherein the upper and lower packings are identically configured to each other, and each have a generally U-shaped cross-sectional configuration and define a channel, the upper and lower packing being oriented relative to each other such that the channels thereof communicate with the gap.
19. A valve adapted to satisfy low fugitive emission leakage standards, the valve comprising:
a valve stem; and
a packing system including:
an upper packing which is disposed in slidable, fluid tight engagement to the valve stem;
a lower packing which is disposed in slidable, fluid tight engagement to the valve stem, the upper packing being separated from the lower packing by a gap;
a fluid barrier filled into the gap, the upper and lower packings and the fluid barrier collectively defining a seal of the packing system; and
a live-loading sub-assembly cooperatively engaged to the seal and operative to apply a load thereto in a manner which maintains the fluid barrier thereof at a prescribed fluid pressure level; and
a load sensor having a body which is abutted against the upper packing.
20. The valve of claim 19 wherein the packing system further comprises:
a packing follower which is abutted against the load sensor;
wherein the load sensor is operative to monitor the load applied to the seal of the packing system by the live-loading sub-assembly.