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The annular space surrounding a flow tube in a subsurface safety valve is sealingly isolated at opposed ends of the flow tube and pressure compensated to the tubing pressure. The subsurface safety valve is inserted and aligned in an outer housing so that hydraulic operating connections are sealingly

The annular space surrounding a flow tube in a subsurface safety valve is sealingly isolated at opposed ends of the flow tube and pressure compensated to the tubing pressure. The subsurface safety valve is inserted and aligned in an outer housing so that hydraulic operating connections are sealingly aligned with opposite hand split ring seals that are properly compressed when the safety valve is secured in its surrounding housing. The assembly is then able to meet high pressure, heavy debris, and marine environment service requirements for subsea conditions with minimal reconfiguration for what would otherwise serve as a borehole subsurface safety valve.

대표청구항 ▼

1. A safety valve assembly for use in a tubular string, comprising: a body having a hydraulically operated flow tube to selectively move into and out of contact with a flapper to selectively open and close a passage through said body and said flow tube wherein movement of said flapper selectively op

1. A safety valve assembly for use in a tubular string, comprising: a body having a hydraulically operated flow tube to selectively move into and out of contact with a flapper to selectively open and close a passage through said body and said flow tube wherein movement of said flapper selectively opens and closes said passage;said flow tube sealed to said body defining an isolated annular space in between when said flapper is in an open and a closed position;a pressure compensation system operable between the passage and said isolated annular space to control differential pressure between said passage in said flow tube and said isolated annular space, said pressure compensation system comprising a movably mounted piston between opposed stops with a pressure relief device that selectively opens if pressure differential across said piston exceeds a predetermined amount. 2. The valve assembly of claim 1, wherein: said annular space is substantially filled with at least one incompressible fluid. 3. The valve assembly of claim 2, wherein: said incompressible fluid is initially pressurized. 4. The valve assembly of claim 2, wherein: said pressure compensation system comprises at least one floating piston containing said incompressible fluid on one side and pressure in said passage of said flow tube on an opposite side. 5. The valve assembly of claim 4, wherein: said floating piston comprises a flowpath therethrough initially blocked by a breakable member. 6. The valve assembly of claim 5, wherein: said breakable member is pressure responsive to break at a predetermined differential pressure. 7. The valve assembly of claim 4, wherein: said floating piston is slidable between opposed travel stops in a respective axial bore in said body. 8. The valve assembly of claim 3, wherein: said incompressible fluid is delivered through a pressurizing bore extending axially through said body and further comprising a check valve to retain said incompressible fluid in said annular space. 9. The valve assembly of claim 1, further comprising: an outer housing comprising a passage therethrough into which said body is inserted, said outer housing comprising end connections for attachment to a tubular string, said body sealingly secured to said housing by virtue of being inserted and secured in said passage of said outer housing so that at least one connection on said body for operation of said flow tube is sealingly extended to an outer surface of said housing. 10. The valve assembly of claim 9, wherein: said outer housing protects said body from tensile, compressive and bending loads associated with subsea service. 11. The valve assembly of claim 9, wherein: said body comprising at least one alignment pin to enter an alignment bore in said housing to align said connection on said body with an extending path to the outer surface of said housing. 12. The valve assembly of claim 9, wherein: said body is secured to said housing with a threaded inner driver in the passage of said housing after insertion of said body in said housing. 13. The valve assembly of claim 11, wherein: said connection on said body and said extending path on said housing are sealed on insertion of said body into said housing using at least one circumferentially split seal ring. 14. The valve assembly of claim 13, wherein: said at least one circumferentially split seal ring comprises a plurality of concentric seal rings;said circumferential splits in two said split rings are oriented away from each other. 15. The valve assembly of claim 13, wherein: said circumferentially split seal rings defining opposed sealing legs that are pressed together between said body and said housing upon assembly of said body to said housing. 16. The valve assembly of claim 14, wherein: said concentric circumferentially split seal rings comprise at least three split ring seals with the two outermost said split rings having their respective circumferential splits oriented open toward an outer surface of said body. 17. The valve assembly of claim 1, wherein: said sealing between said flow tube and said body is accomplished with spaced seals;movement of said movably mounted piston keeps said spaced seals in pressure balance with each other. 18. The valve assembly of claim 1, wherein: said pressure compensation system enables a decrease in the wall thickness of said flow tube to resist burst or collapse, which enables greater production through said body, as compared to not having said pressure compensation system. 19. The valve assembly of claim 17, wherein: said pressure balance between said seals minimizes seal friction to said body to reduce pressure needed for said hydraulic operation of said flow tube. 20. The valve assembly of claim 1, wherein: said piston comprises a passage therethrough selectively covered by a breakable member that allows said passage to open when a predetermined pressure across said piston is reached. 21. The valve assembly of claim 1, wherein: said piston is operably connected with a pressure relief device on opposed sides of said piston to relieve at a predetermined differential pressure across said piston in either direction. 22. A valve assembly that coverts a safety isolation valve to subsea use, said safety isolation valve comprising a body having a flowpath therethrough, said valve assembly comprising: an outer housing comprising flanged end connections adapted to connect to a marine riser and a passage therethrough into which said body further comprising opposed ends is inserted with said flowpath nested in said passage and said opposed ends secured to said outer housing in said passage within said outer housing with a fastener independently of said end connections on said outer housing for attachment to said marine riser, said body sealingly secured to said housing by virtue of being inserted and secured in said passage of said outer housing so that at least one connection on said body for operation of a valve member is sealingly extended to an outer surface of said housing, said body protected by said housing from tensile, compressive and bending loads associated with subsea service acting on said housing. 23. The valve assembly of claim 22, wherein: said body comprising at least one alignment pin to enter an alignment bore in said housing to align said connection on said body with an extending path to the outer surface of said housing. 24. The valve assembly of claim 22, wherein: said body is secured to said housing with a threaded inner driver in the passage of said housing after insertion of said body in said housing energizing at least one seal between said body and said housing with no applied pressure in said housing. 25. A valve assembly that coverts a safety isolation valve to subsea use, said safety isolation valve comprising a body, the valve assembly comprising: an outer housing comprising a passage therethrough into which said body is inserted, said outer housing comprising end connections for attachment to a tubular string, said body sealingly secured to said housing by virtue of being inserted and secured in said passage of said outer housing so that at least one connection on said body for operation of a valve member is sealingly extended to an outer surface of said housing, said body protected by said housing from tensile, compressive and bending loads associated with subsea service acting on said housing;said body comprising at least one alignment pin to enter an alignment bore in said housing to align said connection on said body with an extending path to the outer surface of said housing;said connection on said body and said extending path on said housing are sealed on insertion of said body into said housing using concentric circumferentially split seal rings. 26. The valve assembly of claim 25, wherein: said circumferential splits in two said split rings are oriented away from each other. 27. The valve assembly of claim 25, wherein: said circumferentially split seal rings defining opposed sealing legs that are pressed together between said body and said housing upon assembly of said body to said housing. 28. The valve assembly of claim 26, wherein: said concentric circumferentially split seal rings comprise at least three split ring seals with the two outermost said split rings having their respective circumferential splits oriented open toward an outer surface of said body. 29. The valve assembly of claim 25, wherein: said seal rings define a low pressure region between said body and said housing allowing pressure elsewhere in said housing to place an energizing force on said concentric circumferentially split seal rings. 30. A valve assembly that coverts a safety isolation valve to subsea use, said safety isolation valve comprising a body, the valve assembly comprising: an outer housing comprising a passage therethrough into which said body is inserted, said outer housing comprising end connections for attachment to a tubular string, said body sealingly secured to said housing by virtue of being inserted and secured in said passage of said outer housing so that at least one connection on said body for operation of a valve member is sealingly extended to an outer surface of said housing, said body protected by said housing from tensile, compressive and bending loads associated with subsea service acting on said housing;a pressure compensation system operable between a passage in said body and an isolated annular space between said valve member and said body, said pressure compensation system comprising a movably mounted piston between opposed stops with a pressure relief device that selectively opens if pressure differential across said piston exceeds a predetermined amount. 31. The valve assembly of claim 30, wherein: said movably mounted piston retaining an incompressible fluid initially delivered to minimize volume of compressible fluid isolated by said movably mounted piston. 32. The valve assembly of claim 30, wherein: said movably mounted piston comprises a floating piston.