A gas lift apparatus has a gas lift valve that disposes in a mandrel. A housing of the valve has a chamber, and a seat disposes between the inlet and outlet. A piston movably disposed in the housing has one end exposed to the chamber. A distal end can selectively seal with the seat to close the valv
A gas lift apparatus has a gas lift valve that disposes in a mandrel. A housing of the valve has a chamber, and a seat disposes between the inlet and outlet. A piston movably disposed in the housing has one end exposed to the chamber. A distal end can selectively seal with the seat to close the valve. A first edge-welded bellows disposed on the piston separates the inlet and chamber pressures and can fully compress to a stacked height when the distal end of the piston seals with the seat. A dynamic seal can be achieved at closing by using a captive sliding seal between the piston's distal end and the seat. A second edge-welded bellows can also be disposed on the piston, and the two bellows can operate in tandem. Oil filing the interiors and the passage can move from one bellows to the other to transfer the pressure differential between the inlet and the chamber pressures. The second bellows fully compresses to a stacked height and stops opening of the valve.
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1. A gas lift apparatus, comprising: a housing having a chamber, an inlet, and an outlet and having a first seat disposed between the inlet and the outlet;a piston movably disposed in the housing, the piston having a proximal end exposed to chamber pressure and having a distal end exposed to inlet p
1. A gas lift apparatus, comprising: a housing having a chamber, an inlet, and an outlet and having a first seat disposed between the inlet and the outlet;a piston movably disposed in the housing, the piston having a proximal end exposed to chamber pressure and having a distal end exposed to inlet pressure, the distal end sliding relative to the first seat and selectively sealing fluid communication through the first seat;first and second edge-welded bellows disposed on the piston and separating the inlet pressure from the chamber pressure, the first edge-welded bellows fully compressing to a first stacked height at a point when the distal end seals fluid communication through the first seat, the second edge-welded bellows fully compressing to a second stacked height when the distal end is distanced away from the first seat,wherein the piston comprises an internal passage communicating a first interior of the first edge-welded bellows with a second interior of the second edge-welded bellows. 2. The apparatus of claim 1, wherein the first edge-welded bellows fully compressed to the first stacked height stops the sliding of the distal end relative to the first seat. 3. The apparatus of claim 1, further comprising a check valve disposed in the housing, the check valve permitting fluid communication from the inlet to the outlet and restricting fluid communication from the outlet to the inlet. 4. The apparatus of claim 1, wherein the first and second interiors communicate a pressure differential between the inlet pressure and the chamber pressure via the internal passage. 5. The apparatus of claim 1, wherein an incompressible fluid fills the first and second interiors and the internal passage. 6. The apparatus of claim 1, wherein the first edge-welded bellows comprises a plurality of edge-welded diaphragms being stacked on top of one another when fully compressed in the first stacked height. 7. The apparatus of claim 6, wherein the chamber comprises an end wall having a shape corresponding to one of the edge-welded diaphragms and having one end of the first edge-welded bellows affixed thereto; and wherein the piston comprises a shoulder having a shape corresponding to one of the edge-welded diaphragms and having one end of the first edge-welded bellows affixed thereto. 8. The apparatus of claim 1, wherein the first seat comprises an internal surface, and wherein the distal end of the piston comprises a seal disposed on an external surface of the distal end, the seal biased transversely to an axis of the piston and engaging the internal surface when disposed adjacent thereto. 9. The apparatus of claim 8, wherein the seal comprises a sealing ring and a resilient ring disposed in a groove defined around the external surface, the resilient ring biasing the sealing ring away from the external surface. 10. The apparatus of claim 8, wherein the seal comprises a spring-loaded cup seal having a lip biased away from the external surface. 11. The apparatus of claim 1, wherein the distal end comprises an external surface, and wherein the first seat comprises a seal disposed on an internal surface, the seal biased transversely to an axis of the piston and engaging the external surface of the distal end when disposed adjacent thereto. 12. The apparatus of claim 11, wherein the seal comprises a sealing ring and a resilient ring disposed in a groove defined around the internal surface, the resilient ring biasing the sealing ring away from the internal surface. 13. The apparatus of claim 11, wherein the seal comprises a spring-loaded cup seal having a lip biased away from the internal surface. 14. A gas lift apparatus, comprising: a housing having a chamber, an inlet, and an outlet and having an internal surface disposed between the inlet and the outlet;a piston movably disposed along an axis in the housing, the piston having a proximal end exposed to chamber pressure and having a distal end exposed to inlet pressure, the distal end having an external surface selectively movable relative to the internal surface;at least one bellows disposed on the piston and separating the inlet pressure from the chamber pressure, the at least one bellows comprising a first bellows having a first interior and comprising a second bellows having a second interior; anda seal configured between the internal and external surfaces, the seal selectively sealing fluid communication from the inlet to the outlet and allowing the internal surface to slide relative to the external surface with the movement of the piston along the axis,wherein the first bellows compresses when the piston moves the seal in a sealed engagement between the internal and external surfaces, the first bellows when fully compressed stopping further movement of the piston toward the seal,wherein the second bellows compresses when the piston moves the seal in an unsealed engagement between the internal and external surfaces, the second bellows when fully compressed stopping further movement of the piston away relative to the seal, andwherein the piston comprises an internal passage communicating the first interior of the first bellows with the second interior of the second bellows. 15. The apparatus of claim 14, further comprising a check valve disposed in the housing, the check valve permitting fluid communication from the inlet to the outlet and restricting fluid communication from the outlet to the inlet. 16. The apparatus of claim 14, wherein the second bellows comprises: a second edge-welded bellows disposed on the piston and separating the inlet pressure from the chamber pressure, the second edge-welded bellows fully compressing to a second stacked height when the external surface is distanced away from the internal surface in the unsealed engagement, the second edge-welded bellows when fully compressed stopping the movement of the piston in a second direction along the axis. 17. The apparatus of claim 14, wherein the first and second interiors communicate a pressure differential between the inlet pressure and the chamber pressure via the internal passage. 18. The apparatus of claim 14, wherein an incompressible fluid fills the first and second interiors and the internal passage. 19. The apparatus of claim 14, wherein the seal is disposed on the external surface of the distal end, the seal biased transversely to the axis of the piston and engaging the internal surface of the housing when disposed adjacent thereto. 20. The apparatus of claim 19, wherein the seal comprises a sealing ring and a resilient ring disposed in a groove defined around the external surface, the resilient ring biasing the sealing ring away from the external surface. 21. The apparatus of claim 19, wherein the seal comprises a spring-loaded cup seal having a lip biased away from the external surface. 22. The apparatus of claim 14, wherein the seal is disposed on the internal surface of the housing, the seal biased transversely to the axis of the piston and engaging the external surface of the distal end when disposed adjacent thereto. 23. The apparatus of claim 22, wherein the seal comprises a sealing ring and a resilient ring disposed in a groove defined around the internal surface of the housing, the resilient ring biasing the sealing ring away from the internal surface. 24. The apparatus of claim 22, wherein the seal comprises a spring-loaded cup seal having a lip biased away from the internal surface. 25. The apparatus of claim 14, wherein the first bellows comprises a first edge-welded bellows fully compressing to a first stacked height at a point when the seal in the sealed engagement seals fluid communication, the first edge-welded bellows when fully compressed stopping the movement of the piston in a first direction along the axis. 26. The apparatus of claim 25, wherein the first edge-welded bellows comprises a plurality of edge-welded diaphragms being stacked on top of one another when fully compressed in the first stacked height. 27. The apparatus of claim 25, wherein the chamber comprises an end wall having a shape corresponding to one of the edge-welded diaphragms and having one end of the first edge-welded bellows affixed thereto; and wherein the piston comprises a shoulder having a shape corresponding to one of the edge-welded diaphragms and having one end of the first edge-welded bellows affixed thereto. 28. The apparatus of claim 14, wherein the chamber comprises a dome chamber for containing compressed gas providing the chamber pressure. 29. The apparatus of claim 28, wherein the dome chamber comprises a seat, and wherein the piston comprises a seal element engaging the seat when the piston moves to a pinnacle position away from the seal. 30. The apparatus of claim 29, wherein the seal element engaged with the seat seals an amount of incompressible oil in a portion of the chamber around the first bellows. 31. A gas lift apparatus, comprising: a housing having a dome chamber for containing compressed gas providing a chamber pressure, the dome chamber comprising a seat, the housing having an inlet, an outlet, and an internal surface disposed between the inlet and the outlet;a piston movably disposed along an axis in the housing, the piston having a proximal end exposed to the chamber pressure and having a distal end exposed to inlet pressure, the distal end having an external surface selectively movable relative to the internal surface;a bellows disposed on the piston and separating the inlet pressure from the chamber pressure; anda seal configured between the internal and external surfaces, the seal selectively sealing fluid communication from the inlet to the outlet and allowing the internal surface to slide relative to the external surface with the movement of the piston along the axis,wherein the bellows compresses when the piston moves the seal in a sealed engagement between the internal and external surfaces, the bellows when fully compressed stopping further movement of the piston toward the seal, andwherein the piston comprises a seal element engaging the seat of the dome chamber when the piston moves to a pinnacle position away from the seal. 32. The apparatus of claim 31, further comprising a check valve disposed in the housing, the check valve permitting fluid communication from the inlet to the outlet and restricting fluid communication from the outlet to the inlet. 33. The apparatus of claim 31, wherein the seal is disposed on the external surface of the distal end, the seal biased transversely to the axis of the piston and engaging the internal surface of the housing when disposed adjacent thereto. 34. The apparatus of claim 33, wherein the seal comprises: a sealing ring and a resilient ring disposed in a groove defined around the external surface, the resilient ring biasing the sealing ring away from the external surface; ora spring-loaded cup seal having a lip biased away from the external surface. 35. The apparatus of claim 31, wherein the seal is disposed on the internal surface of the housing, the seal biased transversely to the axis of the piston and engaging the external surface of the distal end when disposed adjacent thereto. 36. The apparatus of claim 35, wherein the seal comprises: a sealing ring and a resilient ring disposed in a groove defined around the internal surface of the housing, the resilient ring biasing the sealing ring away from the internal surface; ora spring-loaded cup seal having a lip biased away from the internal surface. 37. The apparatus of claim 31, wherein the bellows comprises an edge-welded bellows fully compressing to a stacked height at a point when the seal in the sealed engagement seals fluid communication, the edge-welded bellows when fully compressed stopping the movement of the piston in a first direction along the axis. 38. The apparatus of claim 37, wherein the edge-welded bellows comprises a plurality of edge-welded diaphragms being stacked on top of one another when fully compressed in the stacked height. 39. The apparatus of claim 37, wherein the chamber comprises an end wall having a shape corresponding to one of the edge-welded diaphragms and having one end of the edge-welded bellows affixed thereto; and wherein the piston comprises a shoulder having a shape corresponding to one of the edge-welded diaphragms and having one end of the edge-welded bellows affixed thereto.
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