Double barrier gas lift flow control device

1. A reverse flow check valve sub-assembly configured to engage a down-hole flow control device, comprising:

an annular housing having a first end and a second end, the first end being generally hollow, the second end having a central opening and being free of internal or external threads for attaching the annular housing to another component;

an annular sleeve having an inlet end and an outlet end, the outlet end of the sleeve disposed within the first end of the housing and the inlet end of the sleeve having threads for attaching the check-valve sub-assembly to said flow control device;

an annular valve seat disposed within an interior of the housing between the outlet end of the sleeve and the second end of the housing;

a check dart disposed within the interior of the housing between the valve seat and the second end of the housing, the check dart having:

a valve head, wherein the check dart is configured to move between a closed position where the valve head is seated against the valve seat and an open position where the valve head is spaced from the valve seat; and

a valve stem, wherein the valve stem is configured to move through the central opening through the second end of the housing; and

at least one port extending through a sidewall surface of the housing between the annular valve seat and the second end of the housing.

2. The assembly of claim 1 , wherein the outlet end of the sleeve incudes external threads that engage internal threads within the first end of the housing.

3. The assembly of claim 2 , wherein a portion of a body of the sleeve between the inlet end and outlet end extends beyond the first end of the housing.

4. The assembly of claim 3 , wherein the portion of the sleeve extending beyond the housing has an outside diameter substantially equal to an outside diameter of the first end of the annular housing.

5. The assembly of claim 1 , wherein the outlet end of the sleeve is in direct contact with the annular valve seat.

6. The assembly of claim 5 , wherein the outlet end of the sleeve retains the valve seat against a retaining surface within the interior of the housing.

7. The assembly of claim 5 , wherein:

an upper surface of the valve seat is tapered relative to a centerline axis of the housing; and

an outside surface about the outlet end of the sleeve is tapered relative to the centerline axis, wherein the outlet end of the sleeve is partially received within the valve seat between the upper surface and a lower surface of the valve seat.

8. The assembly of claim 1 , further comprising

a check dart support attached to the housing via the sidewall surface of the housing, the check dart support having the central opening sized to receive the valve stem of the check dart.

9. The assembly of claim 8 , further comprising:

a spring disposed between the check dart support and the check dart, wherein the spring biases the valve head toward the valve seat.

10. The assembly of claim 8 , wherein a lower end of the check dart support forms the second end of the housing.

11. The assembly of claim 8 , wherein an outer cross-dimension of the lower end of the check dart support is less than an outside diameter of the first end of the housing.

12. The assembly of claim 8 , wherein the central opening extends through the lower end of the check dart support.

13. The assembly of claim 1 , wherein the valve head comprises:

a flange extending about a periphery of the valve head, wherein an upper surface of the flange engages a bottom surface of the valve seat when the check dart is in the closed position.

14. The assembly of claim 13 , wherein the valve head includes an upper surface that extends through a central opening of the annular valve seat when the check dart is in the closed position.

15. The assembly of claim 14 , wherein the upper surface of the valve head contacts the outlet end of the sleeve when the check dart is in the closed position.

16. The assembly of claim 1 , wherein the valve seat is a pliable element.

17. A flow control device for injecting gas in a down-hole application, comprising:

an injection housing having an upper end, a lower end, an upper external seal extending around an outside surface of the injection housing and a lower external seal extending around the outside surface of the injection housing;

an inlet port extending though a sidewall of the injection housing between the upper external seal and the lower external seal;

an interior reverse flow check valve disposed within the interior of the injection housing, wherein the interior reverse flow check valve is disposed along a length of the injection housing between the inlet port and the lower external seal; and

a lower reverse flow check valve sub-assembly attached to the lower end of the injection housing below the external seal, the lower reverse check flow valve including:

an annular valve housing having a first end and a second end, the first end being generally hollow, the second end having a central opening and being free of internal or external threads for attaching the valve housing to another component;

an annular sleeve having an inlet end and an outlet end, the outlet end of the sleeve disposed within the first end of the valve housing and the inlet end of the sleeve having threads for attaching the check-valve sub-assembly to the lower end of the injection housing;

an annular valve seat disposed within an interior of the valve housing between the outlet end of the sleeve and the second end of the valve housing, wherein the outlet end of the sleeve is in direct contact with the valve seat and compresses the valve seat against a retaining surface in the valve housing;

a check dart disposed within the interior of the valve housing between the valve seat and the second end of the valve housing, the check dart having:

a valve head, wherein the check dart is configured to move between a closed position where the valve head is seated against the valve seat and an open position where the valve head is spaced from the valve seat; and

a valve stem, wherein the valve stem is configured to move through the central opening through the second end of the valve housing.

18. The device of claim 17 , wherein the outlet end of the sleeve is threadedly engaged with the first end of the valve housing and a portion of a body of the sleeve between the inlet end and outlet end extends beyond the first end of the valve housing.

19. A reverse flow check valve sub-assembly configured to engage a down-hole flow control device, comprising:

an annular housing having a first end and a second end, the first end being generally hollow, the second end having a central opening and being free of internal or external threads for attaching the annular housing to another component;

an annular sleeve having an inlet end and an outlet end, the outlet end of the sleeve disposed within the first end of the housing and the inlet end of the sleeve having threads for attaching the check-valve sub-assembly to said flow control device;

an annular valve seat disposed within an interior of the housing between the outlet end of the sleeve and the second end of the housing, wherein the valve seat is a pliable element;

a check dart disposed within the interior of the housing between the valve seat and the second end of the housing, the check dart having:

a valve head, wherein the check dart is configured to move between a closed position where the valve head is seated against the valve seat and an open position where the valve head is spaced from the valve seat; and

a valve stem, wherein the valve stem is configured to move through the central opening through the second end of the housing.

20. The assembly of claim 19 , wherein the outlet end of the sleeve is in direct contact with the valve seat and compresses the valve seat against a retaining surface in the valve housing.

21. The assembly of claim 19 , wherein the outlet end of the sleeve incudes external threads that engage internal threads within the first end of the housing.

22. The assembly of claim 19 , further comprising at least one port extending through a sidewall surface of the housing between the annular valve seat and the second end of the housing.