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A system and method for predicting structural failure of a wall of a fluid containment vessel, such as a hydraulic hose or other type of pressurized conduit of types used in mobile machinery, automotive, aerospace, manufacturing, and process equipment. The wall of the vessel has an innermost layer f

A system and method for predicting structural failure of a wall of a fluid containment vessel, such as a hydraulic hose or other type of pressurized conduit of types used in mobile machinery, automotive, aerospace, manufacturing, and process equipment. The wall of the vessel has an innermost layer for contact with the fluid contained by the vessel, and an outermost layer parallel with the innermost layer. The system includes strain-sensing means between the innermost and outermost layers and comprising at least one conductor parallel to the innermost layer of the wall. The system and method entail sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor.

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The invention claimed is: 1. A system for predicting structural failure of a wall of a fluid containment vessel, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means

The invention claimed is: 1. A system for predicting structural failure of a wall of a fluid containment vessel, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising at least one conductor parallel to the innermost layer of the wall; means for sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor, the electrical property being chosen from the group consisting of electrical capacitance and electrical resistance; means for establishing an acceptable range for the electrical property; and means for generating a signal that a structural failure of the wall is impending in response to the electrical property deviating outside the acceptable range. 2. A system according to claim 1, wherein the change-sensing means senses the electrical capacitance between the at least one conductor and a second conductor of the strain-sensing means. 3. A system according to claim 1, wherein the change-sensing means senses the electrical resistance of the at least one conductor. 4. A system according to claim 1, wherein the at least one conductor is an inner conductive layer parallel to the innermost layer of the wall, the strain-sensing means further comprising: an electrical insulating layer parallel to and contacting the inner conductive layer; and an outer conductive layer parallel to and contacting the insulating layer, the inner and outer conductive layers being separated by the insulating layer and defining a capacitive coupling comprising the inner conductive layer, the insulating layer, and the outer conductive layer; wherein the change-sensing means senses changes in the electrical capacitance of the capacitive coupling resulting from distortion of the wall of the vessel. 5. A system for monitoring a wall of a fluid containment vessel, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising at least one conductor parallel to the innermost layer of the wall; means for sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor, the electrical property being chosen from the group consisting of electrical capacitance and electrical resistance; wherein the at least one conductor is a helical conductive coil between the innermost and outermost layers and surrounding the innermost layer, the coil defines a helical conductive path along a length of the wall, the helical conductive path has an electrical resistance associated therewith, and the change-sensing means senses changes in the electrical resistance of the helical conductive path resulting from distortion of the wall of the vessel. 6. A system according to claim 5, further comprising: means for establishing an acceptable range for the electrical resistance; and means for generating a signal that a structural failure of the wall is impending in response to the electrical resistance deviating outside the acceptable range. 7. A system for monitoring a wall of a fluid containment vessel, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising at least one conductor parallel to the innermost layer of the wall; means for sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor, the electrical property being chosen from the group consisting of electrical capacitance and electrical resistance; wherein the vessel is a hydraulic hose subjected to pressure cycles that induce fatigue in the wall. 8. A system for predicting structural failure of a wall of a hydraulic hose subjected to pressure cycles that induce fatigue in the wall, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising an inner conductive layer parallel to the innermost layer of the wall, an electrical insulating layer parallel to and contacting the inner conductive layer, and an outer conductive layer parallel to and contacting the insulating layer, the inner and outer conductive layers being separated by the insulating layer and defining a capacitive coupling comprising the inner conductive layer, the insulating layer, and the outer conductive layer; means for sensing changes in the electrical capacitance of the capacitive coupling resulting from distortion of the wall of the vessel; means for establishing an acceptable range for the electrical capacitance of the capacitive coupling; and means for generating a signal that a structural failure of the wall is impending in response to the electrical capacitance deviating outside the acceptable range. 9. A system according to claim 8, wherein the inner conductive layer, the insulating layer, and the outer conductive layer are continuous along the length and circumference of the hose. 10. A system according to claim 8, wherein each of the inner and outer conductive layers comprises a wire braiding. 11. A system according to claim 8, further comprising a fitting on each of two opposite ends of the hose, each of the fittings having first and second electrically-conductive members that are electrically insulated from each other, the first and second electrically-conductive members being individually electrically connected to one of the inner and outer conductive layers so as to create an electric capacitive charge between the inner and outer conductive layers. 12. A system for predicting structural failure of a wall of a hydraulic hose subjected to pressure cycles that induce fatigue in the wall, the wall having an innermost layer for contact with a fluid contained by the vessel and an outermost layer parallel with the innermost layer, the system comprising: strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising a helical conductive coil between the innermost and outermost layers and surrounding the innermost layer, the coil defining a helical conductive path along a length of the wall, the helical conductive path having an electrical resistance associated therewith; means for sensing changes in the electrical resistance of the helical conductive path resulting from distortion of the wall of the hydraulic hose; means for establishing an acceptable range for the electrical resistance of the helical conductive path; and means for generating a signal that a structural failure of the wall is impending in response to the electrical resistance deviating outside the acceptable range. 13. A system according to claim 12, wherein the conductive coil comprises an electrically-conductive silicone material. 14. A system according to claim 12, wherein the conductive coil comprises a layer of an electrically-conductive silicone material on a layer of an electrically-insulating material. 15. A system according to claim 12, wherein the inner conductive layer, the insulating layer, and the outer conductive layer are continuous along the length and circumference of the hose. 16. A system according to claim 12, wherein each of the inner and outer conductive layers comprises a wire braiding. 17. A system according to claim 12, further comprising a fitting on each of two opposite ends of the hose, each of the fittings having first and second electrically-conductive members that are electrically insulated from each other, the first and second electrically-conductive members being individually electrically connected to one of the inner and outer conductive layers so as to create an electric capacitive charge between the inner and outer conductive layers. 18. A method of predicting structural failure of a wall of a vessel containing a fluid, the method comprising the steps of: forming the wall to have an innermost layer for contact with a fluid contained by the vessel, an outermost layer parallel with the innermost layer, and strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising at least one conductor parallel to the innermost layer of the wall; sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor, the electrical property being chosen from the group consisting of electrical capacitance and electrical resistance; establishing an acceptable range for the electrical property; and generating a signal that a structural failure of the wall is impending in response to the electrical property deviating outside the acceptable range. 19. A method according to claim 18, wherein the sensing step comprises sensing the electrical capacitance between the at least one conductor and a second conductor of the strain-sensing means. 20. A method according to claim 19, wherein the at least one conductor is formed as an inner conductive layer parallel to the innermost layer of the wall, and the strain-sensing means is formed to further comprise: an electrical insulating layer parallel to and contacting the inner conductive layer; and an outer conductive layer parallel to and contacting the insulating layer, the inner and outer conductive layers being separated by the insulating layer and defining a capacitive coupling comprising the inner conductive layer, the insulating layer, and the outer conductive layer; wherein the sensing step comprises sensing changes in the electrical capacitance of the capacitive coupling resulting from distortion of the wall of the vessel. 21. A method according to claim 18, wherein the sensing step comprises sensing the electrical resistance of the at least one conductor. 22. A method according to claim 18, further comprising subjecting the vessel to fluctuating fluid pressures during the sensing step. 23. A method of monitoring a wall of a vessel containing a fluid, the method comprising the steps of: forming the wall to have an innermost layer for contact with a fluid contained by the vessel, an outermost layer parallel with the innermost layer, and strain-sensing means between the innermost and outermost layers, the strain-sensing means comprising at least one conductor parallel to the innermost layer of the wall; sensing changes in an electrical property associated with the at least one conductor resulting from distortion of the wall of the vessel causing distortion of the at least one conductor, the electrical property being chosen from the group consisting of electrical capacitance and electrical resistance; wherein the at least one conductor is formed as a helical conductive coil between the innermost and outermost layers and surrounding the innermost layer, the coil defines a helical conductive path along a length of the wall, the helical conductive path having an electrical resistance associated therewith, and the method further comprises causing a direct current to flow through the conductive coil and the sensing step comprises sensing changes in the electrical resistance of the helical conductive path resulting from distortion of the wall of the vessel. 24. A method according to claim 23, further comprising the steps of: establishing an acceptable range for the electrical resistance; and generating a signal that a structural failure of the wall is impending in response to the electrical resistance deviating outside the acceptable range. 25. A system for predicting structural failure of a hydraulic hose, the system comprising: a hydraulic hose having: an innermost layer for contact with a fluid; an outermost layer parallel with the innermost layer; an inner conductive layer disposed between the innermost and outermost layers; an electrical insulating layer parallel to the inner conductive layer; an outer conductive layer parallel to the insulating layer, the inner and outer conductive layers being separated by the insulating layer and defining an electrical property; an electrical property monitor in electrical connection with the inner and outer conductive layers of the hydraulic hose; and a signal generator in electrical connection with the electrical property monitor, the signal generator generating a signal in response to changes in the electrical property of the hydraulic hose changing as a result of distortion of the innermost layer of the hydraulic hose causing distortion of the inner and outer conductive layers. 26. A system according to claim 25, wherein the electrical property is selected from the group consisting of electrical resistance and electrical capacitance. 27. A system according to claim 25, wherein the signal is a visual signal. 28. A system according to claim 25, wherein the signal is an audible signal. 29. A method of predicting structural failure of a hydraulic hose, the method comprising the steps of: providing a hydraulic hose having: an innermost layer for contact with a fluid; an outermost layer parallel with the innermost layer; an inner conductive layer disposed between the innermost and outermost layers; an electrical insulating layer parallel to the inner conductive layer; an outer conductive layer parallel to the insulating layer, the inner and outer conductive layers being separated by the insulating layer and defining an electrical property selected from the group consisting of electrical capacitance and electrical resistance; sensing changes in the electrical property of the hydraulic hose resulting from distortion of the innermost layer causing distortion of the inner conductive layer; generating a signal that a structural failure of the wall is impending in response to changes of the electrical property. 30. A method according to claim 29, further comprising establishing an acceptable limit for the electrical property. 31. A method according to claim 30, wherein the signal is generated in response to the electrical property deviating from the acceptable limit. 32. A method according to claim 31, wherein the acceptable limit is a range of values. 33. A method according to claim 31, wherein the acceptable limit is an upper limit.