Expansion compensator with multiple layers with differing stiffness

1. An expansion compensator having a longitudinal axis and comprising:

a) an elongate metal conduit having first and second spaced apart ends, an inner surface, an outer surface, a thickness, and an expansion/contraction section; and

b) an inner plastic liner positioned interior of the elongate metal conduit and having first and second spaced apart ends, an inner surface, an outer surface, a thickness, an expansion/contraction section, and an interior volume extending from the first end to the second end;

wherein the first and second spaced apart ends of the elongate metal conduit and the inner plastic liner are secured together,

and wherein each of the elongate metal conduit and the inner plastic liner have a stiffness along the longitudinal axis, and the stiffness of the elongate metal conduit is greater than the stiffness of the inner plastic liner and

wherein the first spaced apart ends of the elongate metal conduit and the inner plastic liner are secured together by a first connector, the first connector comprising a first arm that is secured to the first end of the inner plastic liner, a second arm that is secured to the first end of the elongate metal conduit and an end portion that is connected to each of the first and second arms and;

and the second spaced apart ends of the elongate metal conduit and the inner plastic liner are secured together by a second connector, the second connector comprising a first arm that is secured to the first end of the inner plastic liner, a second arm that is secured to the first end of the elongate metal conduit and an end portion that is connected to each of the first and second arms.

2. The expansion compensator of claim 1 wherein the stiffness of the elongate metal conduit is at least 25% greater than the stiffness of the inner plastic liner.

3. The expansion compensator of claim 1 wherein the stiffness of the elongate metal conduit is at least 50% greater than the stiffness of the inner plastic liner.

4. The expansion compensator of claim 1 wherein the stiffness of the elongate metal conduit is from at least 150% greater to about 1,000% greater than the stiffness of the inner plastic liner.

5. The expansion compensator of claim 4 wherein the stiffness of the elongate metal conduit is from at least 300% greater to about 375% greater than the stiffness of the inner plastic liner.

6. The expansion compensator of claim 1 wherein the stiffness of the elongate metal conduit is sufficiently greater than the stiffness of the inner plastic liner such that the elongate metal conduit will absorb more than 50% of a compressive force imposed on the expansion compensator by a piping system into which the expansion compensator is positioned.

7. The expansion compensator of claim 6 wherein the stiffness of the elongate metal conduit is sufficiently greater than the stiffness of the inner plastic liner such than the elongate metal conduit will absorb more than 75% of the compressive force.

8. The expansion compensator of claim 6 wherein the stiffness of the elongate metal conduit is sufficiently greater than the stiffness of the inner plastic liner such than the elongate metal conduit will absorb about 90% of the compressive force.

9. The expansion compensator of claim 1 wherein the thickness of the elongate metal conduit and the thickness of the inner plastic liner are each selected to provide the stiffness of the elongate metal conduit that is greater than the stiffness of the inner plastic liner.

10. The expansion compensator of claim 9 wherein the thickness of the elongate metal conduit is from about 0.005 to about 0.030 inches and the thickness of the inner plastic liner is from about 0.005 to about 0.250 inches.

11. The expansion compensator of claim 9 wherein the thickness of the elongate metal conduit is from about 0.012 to about 0.016 inches and the thickness of the inner plastic liner is from about 0.040 to about 0.090 inches.

12. The expansion compensator of claim 1 wherein the first spaced apart ends of the elongate metal conduit and the inner plastic liner are secured together by a first connector that is molded over the first spaced apart ends and the second spaced apart ends of the elongate metal conduit and the inner plastic liner are secured together by a second connector that is molded over the second spaced apart ends.

13. The expansion compensator of claim 12 wherein each of the first and second ends of the elongate metal conduit has a plurality of openings therethrough and each of the first and second connectors further comprise a connecting portion that extends through the plurality of openings.

14. The expansion compensator of claim 12 further comprising a gasket provided on the elongate metal conduit and extending between the outer surface of the elongate metal conduit and an inner surface of the first connector.

15. The expansion compensator of claim 1 wherein the elongate metal conduit comprises at least an inner and an outer elongate metal conduit, the inner elongate metal conduit is positioned intermediate the outer elongate metal conduit and the inner plastic liner, and each of the inner and outer elongate metal conduits has first and second spaced apart ends, an inner surface, an outer surface, and an expansion/contraction section.

16. The expansion compensator of claim 15 wherein the thickness of each of the inner and outer elongate metal conduit is from about 0.004 to about 0.025 inches and the thickness of the inner plastic liner is from about 0.005 to about 0.250 inches.

17. The expansion compensator of claim 15 wherein the thickness of each of the inner and outer elongate metal conduit is from about 0.012 to about 0.016 inches and the thickness of the inner plastic liner is from about 0.040 to about 0.090 inches.

18. The expansion compensator of claim 15 wherein a lubricant is provided between the inner and outer elongate metal conduits.

19. The expansion compensator of claim 1 further comprising a protective layer intermediate the inner surface of the elongate metal conduit and the outer surface of the inner plastic liner.

20. The expansion compensator of claim 19 wherein:

a) the protective layer comprises a coating or a film applied to at least one of the inner surface of the elongate metal conduit and the outer surface of the inner plastic liner; or

b) the inner plastic liner comprises a co-extruded body having the protective layer formed as an outer co-extruded layer; or

c) the protective layer comprises a separately formed sleeve positioned between the inner surface of the elongate metal conduit and the outer surface of the inner plastic liner.

21. The expansion compensator of claim 1 wherein the expansion/contraction sections have a similar profile and are aligned.

22. The expansion compensator of claim 1 wherein the inner plastic liner has a generally uniform thickness.

23. The expansion compensator of claim 22 wherein the sleeve further comprises engagement members positioned to maintain the sleeve in a predetermined axial position along the expansion compensator and to permit the expansion/contraction sections to expand to a full design expansion length.

24. The expansion compensator of claim 1 wherein the expansion/contraction section of the inner plastic liner comprises a bellows comprising in sequence a plurality of radially inner valleys and a plurality of radially outer peaks, a portion of the inner plastic liner defining the radial inner valleys having a greater radial thickness then a portion of the inner plastic liner defining the radial outer peaks.

25. The expansion compensator of claim 1 further comprising a longitudinally extending recess provided in the inner wall of the elongate metal conduit.

26. The expansion compensator of claim 1 further comprising a sleeve, the sleeve having a generally longitudinally extending outer surface and the elongate metal conduit is provided interior of the sleeve.

27. The expansion compensator of claim 26 wherein a lubricant is provided between the sleeve and the elongate metal conduit.