Systems, methods and tools for the interrogation of composite strength members
Systems, methods and tools for the interrogation of fiber-reinforced composite strength members to assess the structural integrity of the strength members. The systems and methods utilize the transmission of light through optical fibers that are embedded along the length of the strength members. The inability to detect light through one or more of the optical fibers may be an indication that the structural integrity of the strength member is compromised. The systems and methods may be implemented without great difficulty and may be implemented at any time in the life cycle of the strength member, from production through installation. The systems and methods have particular applicability to bare overhead electrical cables that include a fiber-reinforced strength member.
1. A method for the interrogation of an elongate fiber-reinforced composite strength member, the strength member comprising at least a first strength element, the strength element comprising a binding matrix and a plurality of reinforcing fibers operatively disposed within the binding matrix to form a fiber-reinforced composite, and at least a first optical fiber embedded in the fiber-reinforced composite and extending along a length of the fiber-reinforced composite, the method comprising the steps of:
operatively attaching a light transmitting device to a first end of the strength member, the light transmitting device comprising a light source that is operatively connected to a power source;
operatively attaching a light detecting device to a second end of the strength member;
transmitting light from the light source into a first end of the first optical fiber and towards the light detecting device, where the transmitted light is incoherent; and
detecting the transmitted light by the light detecting device through a second end of the first optical fiber.
2. The method recited in claim 1 , wherein the transmitted light has a wavelength of at least about 300 nm and not greater than about 1700 nm.
3. The method recited in claim 2 , wherein the transmitted light has a wavelength in the infrared region.
4. The method recited in claim 2 , wherein the transmitted light has a primary wavelength of at least about 800 nm.
5. The method recited in claim 2 , wherein the transmitted light has a primary wavelength of not greater than about 1000 nm.
6. The method recited in claim 2 , wherein the step of transmitting light comprises energizing a light emitting diode (LED).
7. The method recited in claim 6 , wherein the step of transmitting light comprises rotating the LED while transmitting the light.
8. The method recited in claim 1 , wherein the first optical fiber is a single mode optical fiber.
9. The method recited in claim 1 , comprising the step of applying an index-matching gel onto the first end of the strength member to facilitate the transmission of light into the first optical fiber.
10. The method recited in claim 1 , wherein:
the first optical fiber extends from a first end surface of the fiber-reinforced composite to a second end surface of the fiber-reinforced composite;
the first end of the first optical fiber does not extend beyond the first end surface of the fiber-reinforced composite; and
the second end of the first optical fiber does not extend beyond the second end surface of the fiber-reinforced composite.
11. The method recited in claim 10 , wherein the first strength element includes at least a second optical fiber embedded in the fiber-reinforced composite and extending along the length of the fiber-reinforced composite, and wherein the step of transmitting the light transmits the light into a first end of the second optical fiber.
12. The method recited in claim 11 , wherein:
the second optical fiber extends from the first end surface of the fiber-reinforced composite to the second end surface of the fiber-reinforced composite;
the first end of the second optical fiber does not extend beyond the first end surface of the fiber-reinforced composite; and
the second end of the second optical fiber does not extend beyond the second end surface of the fiber-reinforced composite.
13. The method recited in claim 11 , wherein the first strength element includes at least a third optical fiber embedded in the fiber-reinforced composite and extending along the length of the fiber-reinforced composite, and wherein the step of transmitting the light transmits the light into a first end of the third optical fiber.
14. The method recited in claim 13 , wherein:
the third optical fiber extends from the first end surface of the fiber-reinforced composite to the second end surface of the fiber-reinforced composite;
the first end of the third optical fiber does not extend beyond the first end surface of the fiber-reinforced composite; and
the second end of the third optical fiber does not extend beyond the second end surface of the fiber-reinforced composite.
15. The method recited in claim 12 , wherein the first strength element includes at least a fourth optical fiber embedded in the fiber-reinforced composite and extending along the length of the fiber-reinforced composite, and wherein the step of transmitting the light transmits the light into a first end of the fourth optical fiber.
16. The method recited in claim 15 , wherein:
the fourth optical fiber extends from the first end surface of the fiber-reinforced composite to the second end surface of the fiber-reinforced composite;
the first end of the fourth optical fiber does not extend beyond the first end surface of the fiber-reinforced composite; and
the second end of the fourth optical fiber does not extend beyond the second end surface of the fiber-reinforced composite.
17. The method recited in claim 10 , further comprising the step of:
polishing the first end surface of the fiber-reinforced composite before the step of operatively attaching the light transmitting device to the first end of the strength member.
18. The method recited in claim 17 , further comprising the step of:
polishing the second end surface of the fiber-reinforced composite before the step of operatively attaching the light detecting device to the second end of the strength member.
19. The method recited in claim 1 , wherein the composite strength member is a single element strength member.
20. The method recited in claim 1 , wherein the composite strength member has a length of at least about 500 meters.
21. The method recited in claim 1 , wherein the composite strength member has a length of at least about 3500 meters.
22. The method recited in claim 1 , wherein the composite strength member has a length of not greater than about 7500 meters.
23. The method recited in claim 1 , wherein, during the steps of transmitting light and detecting the transmitted light, the composite strength member is wrapped onto a spool.
24. The method recited in claim 1 , further comprising the step of stress testing the composite strength element before the steps of transmitting light and detecting the transmitted light.
25. The method recited in claim 1 , wherein an electrical conductor is stranded around the composite strength member to form an overhead electrical cable.
26. The method recited in claim 25 , wherein the steps of transmitting light and detecting the transmitted light are performed after stranding the composite strength member with the electrical conductor and before installation of the overhead electrical cable onto support towers.
27. The method recited in claim 25 , wherein the steps of transmitting light and detecting the transmitted light are performed after installation of the overhead electrical cable onto support towers.