Cable air supply monitoring system

Abstract

To provide a cable gas supply monitoring system capable of detecting damage generated in a cable early and inspecting the damaged portion of the cable effectively to enable maintenance.SOLUTION: A cable gas supply monitoring system A of the present invention comprises: a cable 1 including a cable band unit; multiple first cable band units 14a each provided with a gas supply unit 2 for supplying dried gas into the cable 1; a second cable band unit 14b provided with an exhaust unit 3 for discharging the dried gas supplied into the cable 1 to the outside of the cable; a first sensor unit 4 that is installed near the second cable band unit 14b and measures relative humidity of the dried gas flowing through the cable; and a control unit that issues an alarm signal when monitoring standards of the relative humidity are not satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cable air supply monitoring system. [Background technology]

[0002] Suspension bridges have traditionally been used as bridges spanning straits, rivers, etc. The main cables of these suspension bridges transmit the load of the bridge girders to the main towers and the ground via hanger ropes, and are extremely important structural components of suspension bridges.

[0003] The main cable is made up of a large number of metal wires bundled together, and various measures have been taken to prevent or reduce corrosion of the wires.

[0004] Patent Document 1 discloses a corrosion prevention method for a cable having a plurality of bundled wires and a covering tube covering the plurality of wires, the corrosion prevention method comprising the steps of: mixing a low-oxygen gas having an oxygen concentration lower than that of air with the air; and supplying the mixed gas obtained by mixing the low-oxygen gas with the air into the covering tube and flowing it around the plurality of wires.

[0005] Patent Document 2 discloses a corrosion protection method for a cable for a suspension structure, in which an air supply section and an exhaust section that are conductive to the inside of the coating are provided at appropriate intervals along the length of the cable for a suspension structure, which is made by bundling a large number of metal wires and coating the outer periphery of the bundled wires, and dry gas is sent from the air supply section to the gaps between the metal wires and exhausted from the exhaust section. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-94690 [Patent Document 2] Japanese Patent Application Publication No. 10-159019 Summary of the Invention [Problem to be solved by the invention]

[0007] However, although the corrosion prevention method of Patent Document 1 supplies a mixed gas of low-oxygen gas and air into the main cable, it does not measure whether the oxygen concentration in the mixed gas circulating inside the main cable is maintained within a predetermined concentration range, and it was not possible to determine whether the corrosion prevention measures for the main cable were functioning effectively.

[0008] In the corrosion protection method for cables for suspension structures described in Patent Document 2, air supply sections and exhaust sections are attached alternately along the length of the cable for suspension structures, and dry gas is supplied into the cable for suspension structures from the air supply sections, and the dry gas in the cable for suspension structures is exhausted from the exhaust sections.

[0009] A temperature and humidity sensor is attached to the exhaust section of the suspension structure cable to manage the dry gas, but the dry gas discharged from the exhaust section is a mixture of dry gas supplied from the air supply sections on both sides of the exhaust section.

[0010] When the temperature and humidity of the dry gas are measured in the exhaust unit and an abnormality is found in the dry gas, it is not possible to determine which air supply unit supplied the dry gas that is abnormal. Therefore, it is necessary to inspect two air supply sections formed between the exhaust unit and the air supply unit adjacent to this exhaust unit, which requires a great deal of effort.

[0011] The present invention provides a cable air supply monitoring system that detects damage to a cable early and enables efficient inspection and maintenance of damaged areas of the cable in corrosion prevention equipment that supplies dry air into the cable to reduce or prevent rust on the wires inside the cable. [Means for solving the problem]

[0012] The cable air supply monitoring system of the present invention comprises: a cable including a plurality of bundled wires, a plurality of covering tubes covering the wires and arranged in the length direction of the wires while forming gaps between opposing end faces of the covering tubes, and a cable band portion closing the gaps between adjacent covering tubes; a plurality of first cable band portions, each of which is one of the cable band portions in the cable and is provided with an air supply portion for supplying dry gas into the cable; a second cable band portion which is one cable band portion present between the adjacent first cable band portions, with a plurality of cable band portions interposed between it and the first cable band portion, and which is provided with an exhaust portion for exhausting dry gas supplied from the air supply portion of the first cable band portion into the cable to the outside of the cable; a first sensor unit disposed on the cable band near the second cable band and configured to measure the relative humidity of the dry gas flowing through the cable; The humidity sensor is characterized by comprising a control unit that issues a warning signal when the relative humidity measured by the first sensor unit does not satisfy a predetermined monitoring standard for relative humidity. [Effects of the Invention]

[0013] The cable air supply monitoring system of the present invention includes a first sensor unit disposed on a cable tie near a second cable tie having an exhaust section, and the first sensor unit measures the relative humidity of the dry gas flowing through the cable. The first sensor unit can accurately measure the relative humidity of the dry gas flowing through the air supply section formed between the second cable tie near the first sensor unit and the first cable tie. If an abnormality is found in the relative humidity measured by the first sensor unit, it is sufficient to inspect the air supply section. This allows the inspection area to be shortened, shortening the inspection time and improving the inspection accuracy.

[0014] The above-mentioned cable air supply monitoring system is provided with a second sensor unit that measures the relative humidity of the dry gas supplied to the air supply unit of the first cable band unit, and the control unit issues a warning signal when the relative humidity measured by the second sensor unit does not meet a predetermined relative humidity monitoring standard, thereby quickly detecting an abnormality in the dry gas supplied to the air supply unit of the first cable band unit, and supplying dry gas adjusted to an appropriate relative humidity into the cable, thereby effectively preventing or reducing the occurrence of rust and other problems on the wires in the cable. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a suspension bridge with a main cable. [Figure 2] FIG. 2 is a schematic diagram showing a main part of a main cable. [Figure 3] FIG. 2 is a cross-sectional view showing a main cable. [Figure 4] FIG. 1 is a system configuration diagram showing a cable air supply monitoring system. DETAILED DESCRIPTION OF THE INVENTION

[0016] An example of a cable air supply monitoring system of the present invention will be described with reference to the drawings. The cable of the cable air supply monitoring system A is the main cable of a suspension bridge B as an example, but the present invention is not limited to this.

[0017] As shown in Figure 1, suspension bridge B comprises anchorages (abutments) (not shown) installed on both sides of a strait or river, multiple main towers B1, B1... arranged between these anchorages, a main cable 1 stretched across via tower top saddles B11 installed on each of the main towers B1 and with both ends fixed to the abutments, hanger ropes B2, B2... suspended at predetermined intervals from the main cable 1, and a bridge girder B3 supported by the multiple hanger ropes B2, B2...

[0018] As shown in Figures 1 and 2, the cable air supply monitoring system A includes a main cable 1 including a cable band portion 14, a first cable band portion 14a provided on one of the cable band portions 14 of the main cable 1 and having an air supply portion 2 for supplying dry gas, a second cable band portion 14b having an exhaust portion 3 for discharging the dry gas within the main cable 1 to the outside of the main cable 1, a first sensor portion 4 for measuring the relative humidity of the dry gas, and a control portion for issuing an alarm signal under specified conditions based on the relative humidity measured by the first sensor portion 4.

[0019] As shown in FIG. 3, the main cable 1 has hundreds to tens of thousands of metal wires 11 that are bundled together in a drawn-out state. Gaps are formed between opposing longitudinal surfaces of the wires 11, and dry gas is circulated through these gaps. The dry gas is not particularly limited, and examples thereof include air and nitrogen. Dry gas refers to gas with a predetermined moisture content or less. Specifically, dry air refers to gas with a predetermined relative humidity standard or less. The relative humidity standard of the dry gas is preferably 60%, and more preferably 40% or less.

[0020] The first sensor unit 4 and the second sensor unit 5 described later measure the moisture content in the dry gas and the temperature of the dry gas, calculate the saturated water vapor content at that temperature, and calculate the relative humidity (%) by dividing the measured moisture content by the saturated water vapor content and multiplying the result by 100.

[0021] The wire 11 is partially covered with a plurality of cylindrical covering tubes 12 each having a certain length. A gap 13 is formed between the opposing end faces of adjacent covering tubes 12 in the longitudinal direction of the wire 11. A cylindrical cable band 14 is attached and integrated into the gap 13 formed between the covering tubes 12, 12, to airtightly close the gap 13. The structure of the covering tube 12 is not particularly limited, as long as it partially covers the wire 11 airtightly. The covering tube 12 is formed, for example, by tightly winding a long body (e.g., a rubber rope, a metal rope, etc.) around the outer circumferential surface of the bundled wires 11 to form a wound body, and then airtightly covering the entire outer circumferential surface of the wound body with a coating layer.

[0022] The cable band portion 14 is formed into a cylindrical shape by joining a pair of semi-cylindrical members together. The cable band portion 14 is attached to a gap 13 formed between the covering tubes 12, 12 covering the wire 11, with both longitudinal ends of the cable band portion 14 overlapping the ends of the covering tube 12 facing each other. The wire 11 of the main cable 1 is hermetically covered on its entire surface by a plurality of covering tubes 12, 12... and the cable band portion 14 arranged between the covering tubes 12, 12. The gap between the opposing surfaces of the covering tubes 12 and the cable band portion 14 is hermetically filled with a sealing material.

[0023] Among the cable bands 14 of the main cable 1, the plurality of cable bands 14a are provided with an air supply section 2 for supplying dry gas to the wire 11. The cable bands 14 provided with this air supply section 2 are referred to as first cable bands 14a. Specifically, the main cable 1 is provided with a plurality of cable bands (first cable bands) 14a provided with an air supply section 2. A plurality (preferably five or more) of cable bands 14 not provided with an air supply section 2 are arranged between the plurality of first cable bands 14a. In other words, the plurality of first cable bands 14a are arranged at intervals in the longitudinal direction of the main cable 1, with a plurality (preferably five or more) of cable bands 14c sandwiched therebetween. The first cable bands 14a do not have an exhaust section.

[0024] As shown in Fig. 3, the air supply unit 2 of the first cable band portion 14a has a supply hole 21 that penetrates the cable band portion 14a in an inward and outward direction. The inner opening of the supply hole 21 of the air supply unit 2 opens toward the wire 11. The outer opening of the supply hole 21 of the air supply unit 2 is connected to and communicates with a dry gas supply pipe (not shown). A gap through which dry gas can flow is formed between the inner peripheral surface of the first cable band portion 14a and the outer peripheral surface of the wire body formed by bundling multiple wires 11. The dry gas can flow into the gaps between the wires 11, 11 through this gap.

[0025] The dry gas supply pipe has a main pipe, one end of which is connected to and communicates with a dry gas supply source (not shown). The main pipe of the dry gas supply pipe is provided with a plurality of branch pipes. The branch pipes of the dry gas supply pipe are airtightly connected to and communicate with the supply holes 21 of the air supply unit 2 of the first cable bundling portion 14a. Dry gas supplied from the dry gas supply source is supplied into the main cable 1 via the dry gas supply pipe and the supply holes 21 of the air supply unit 2 of the first cable bundling portion 14a.

[0026] One of the cable bands 14 between the first cable bands 14a, 14a is provided with an exhaust section 3 for exhausting dry gas, which is supplied to the wires 11 through the air supply section 2 and which has circulated through the gaps between the wires 11 of the main cable 1, to the outside of the main cable 1. The cable band 14 provided with this exhaust section 3 is referred to as the second cable band 14b. That is, one cable band (second cable band) 14b provided with an exhaust section 3 is disposed between each of the first cable bands 14a, 14a. The second cable band 14b does not have an air supply section. Furthermore, at least two or more third cable bands 14c, which are provided with neither an air supply section 2 nor an exhaust section 3, are disposed between the first cable band 14a and the second cable band 14b.

[0027] The exhaust portion 3 of the cable band portion 14b has an exhaust hole 31 penetrating the cable band portion 14b in an inward and outward direction. The inner opening of the exhaust hole 31 of the exhaust portion 3 opens toward the wire 11. The outer opening of the exhaust hole 31 of the exhaust portion 3 is connected to and communicates with a dry gas exhaust pipe (not shown). A gap through which dry air can flow is formed between the inner circumferential surface of the second cable band portion 14b and the outer circumferential surface of the wire body formed by bundling multiple wires 11. The dry gas that has flowed through the gaps between the wires 11, 11 can flow into the exhaust hole 31 through this gap.

[0028] The dry gas exhaust pipe has a main pipe, one end of which is connected to and communicates with a dry gas recovery section (not shown). The main pipe of the dry gas exhaust pipe has multiple branch pipes. The branch pipes of the dry gas exhaust pipe are airtightly connected to and communicate with the discharge holes 31 of the second cable band section 14b. The dry gas discharged from the discharge holes 31 of the second cable band section 14b is discharged to the dry gas recovery section through the dry gas exhaust pipe. The used dry gas recovered in the dry gas recovery section may be released directly into the air, or the used dry gas may be processed and reused as dry gas. Note that the used dry gas may be discharged to the outside air through the dry gas exhaust pipe or the exhaust section 3 without providing a dry gas recovery section.

[0029] In this way, from the dry gas supply source to the recovery or discharge of the dry gas, the inside of the dry gas supply pipe, the main cable 1 and the dry gas discharge pipe are kept airtightly isolated from the outside air.

[0030] The main cable 1 has first cable bands 14a arranged at intervals along the length of the main cable 1, and a second cable band 14b (only one) arranged between each pair of adjacent first cable bands 14a. Furthermore, a third cable band 14c is arranged between each pair of adjacent first cable bands 14a and 14b. In the present invention, the phrase "adjacent first cable bands 14a and 14b" refers to the adjacent first cable bands 14a and 14b when only the first cable bands 14a and 14b are considered. In the present invention, the phrase "adjacent first cable bands 14a and 14a" refers to the adjacent first cable bands 14a and 14a when only the first cable band 14a is considered.

[0031] The gaps between the wires 11, 11 of the main cable 1 are continuous in the longitudinal direction of the wires 11, and the dry gas supplied from the air supply section 2 of the first cable band section 14a flows through the gaps between the wires 11 of the main cable 1, and then is discharged outside the main cable 1 from the exhaust section 3 of the second cable band section 14b, which is closest to the first cable band section 14a where the air supply section 2 is provided.

[0032] Furthermore, by replacing the cable band section of the existing main cable 1 with the cable band section 14a (14b) having the air supply section 2 (exhaust section 3), the air supply section 2 (exhaust section 3) can also be arranged on the existing main cable 1, making it possible to apply this to existing suspension bridges as well.

[0033] 1 and 2, first cable bundling portions 14a provided with air supply portions 2 and second cable bundling portions 14b provided with exhaust portions 3 are arranged alternately in the longitudinal direction of the main cable 1. For ease of understanding, in FIG. 1, the first cable bundling portions 14a provided with the air supply portions 2 are labeled 14a-1 to 14a-3 from the left, respectively. The second cable bundling portions 14b provided with the exhaust portions 3 are labeled 14b-1 to 14b-4 from the left, respectively.

[0034] The dry gas supplied into the cable 1 from the air supply section 2 of the first cable band section 14a-1 branches into two, flows through the gaps between the wires 11, and is discharged outside the main cable 1 from the exhaust sections 3, 3 of the second cable band sections 14b-1, 14b-2.

[0035] Similarly, the dry gas supplied into the main cable 1 from the air supply section 2 of the first cable band section 14a-2 (14a-3) branches into two, flows through the gaps between the wires 11, and is discharged outside the main cable 1 from the exhaust sections 3, 3 of the second cable band sections 14b-2, 14b-3 (14b-3, 14b-4).

[0036] In Fig. 2, the flow of dry gas supplied into the main cable 1 through the air supply section 2 of the first cable bundling section 14a is indicated by an arrow above the air supply section 2. In Fig. 2, the flow of dry gas discharged to the outside of the main cable 1 from the exhaust section 3 of the second cable bundling section 14b is indicated by an arrow above the exhaust section 3. In Fig. 1, the flow of dry gas supplied into the cable 1 from the air supply section 2 of the first cable bundling section 14a is indicated by an arrow below the main cable 1.

[0037] Furthermore, between the first cable band portion 14a and the second cable band portion 14b, as described above, there are two or more third cable band portions 14c that do not have both the air supply section 2 and the exhaust section 3.

[0038] A first sensor unit 4 is disposed on the third cable band unit 14c located near the second cable band unit 14b, and measures the relative humidity of the dry gas flowing through the gaps formed between the wires 11. The first sensor unit 4 can be a known device for measuring the relative humidity of gas.

[0039] The third cable band 14c near the second cable band 14b refers to the third cable band 14c where the distance L2 to the nearest first cable band 14a is shorter than the distance L1 to the nearest second cable band 14b in the length direction of the main cable 1. Within the third cable band 14c where the first sensor unit 4 is disposed, dry gas flows in one direction from the first cable band 14a side to the second cable band 14b side, and is adjusted so that dry gas does not flow from the second cable band 14b side into the third cable band 14c where the first sensor unit 4 is disposed. This adjustment is performed by controlling (1) the distance between the third cable band portion 14c where the first sensor portion 4 is arranged and the second cable band portion 14b, (2) the supply pressure of the dry gas supplied from the air supply portion 2 of the first cable band portion 14a, or (3) the suction force of the dry gas exhausted from the exhaust portion 3 of the second cable band portion 14b.

[0040] Within the main cable 1, an air supply section is formed between adjacent first and second cable bands 14a, 14b. Two or more third cable bands 14c are disposed between adjacent first and second cable bands 14a, 14b. Within the air supply section, a first sensor unit 4 is provided near the second cable band 14b. The first and second cable bands 14a, 14b forming the air supply section are the first and second cable bands 14a, 14b closest to the third cable band 14c on which the first sensor unit 4 is provided. Therefore, the first sensor unit 4 can pinpoint the relative humidity of only the dry gas flowing through the air supply section.

[0041] That is, within the main cable 1, an air supply section is formed between the adjacent first and second cable bands 14a and 14b. A third cable band 14c, on which a first sensor unit 4 is provided, is provided near the second cable band 14b in this air supply section. In the air supply section, dry gas flows in one direction from the first cable band 14a to the second cable band 14b. Only dry air supplied from the air supply unit 2 of the first cable band 14a, which is the start point of this air supply section, flows through the air supply section. The first sensor unit 4 is disposed near the exhaust unit 3 of the second cable band 14b, which is the end point of the air supply section.

[0042] Therefore, the relative humidity of the dry gas that has circulated over as long a distance as possible in the air supply section can be measured by the first sensor unit 4. Based on the relative humidity of the dry gas, it can be easily detected whether or not an abnormality has occurred in the air supply section, covering most of the air supply section of the main cable 1.

[0043] In particular, it is preferable to provide the first sensor unit 4 on the third cable band 14c adjacent to the second cable band 14b. By providing the first sensor unit 4 on this third cable band 14c, it becomes possible to target a larger portion of the air supply section of the main cable 1 and more easily detect whether or not an abnormality has occurred in the air supply section.

[0044] The cable air supply monitoring system A also includes a second sensor unit 5 that measures the relative humidity of the dry gas supplied to the air supply unit 2 of the first cable band unit 14a. Similar to the first sensor unit 4, the second sensor unit 5 can use a known device for measuring the relative humidity of gas. The second sensor unit 5 is provided in the main pipe or each branch pipe (preferably the main pipe) of the dry gas supply pipe, and measures the relative humidity of the dry gas flowing through the dry gas supply pipe. Based on the relative humidity of the dry gas measured by the second sensor unit 5, it is possible to determine whether dry gas that satisfies a predetermined relative humidity standard is being supplied into the main cable 1.

[0045] As shown in Figure 4, the cable air supply monitoring system A includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, an auxiliary storage device 64, and an output module 65.

[0046] The first sensor unit 4, the second sensor unit 5, the ROM 62, the RAM 63, the auxiliary storage device 64, and the output module 66 are electrically connected to the CPU 61 so as to be able to communicate with each other via an A / D conversion unit as necessary. The A / D conversion unit quantizes the analog signal to generate a digital signal that can be input to the CPU 61.

[0047] The CPU 61 acquires the relative humidity of the dry gas measured by the first sensor unit 4 and the second sensor unit 5 as a digital signal. A general-purpose wireless module may be attached to or installed in the CPU 61, the auxiliary storage device 64, the first sensor unit 4, and the second sensor unit 5, and electrically connected to enable wireless communication with each other. The wireless module is a module for performing wireless data communication and for realizing a typical wireless communication method such as Wi-Fi (registered trademark), Bluetooth (registered trademark), W-CDMA standard, LTE standard, or LPWA (Low Power Wide Area) standard.

[0048] Examples of the auxiliary storage device 64 include a solid state drive (SSD) and a hard disk drive (HDD). Examples of the output module 65 include a display, a speaker, and a mobile terminal device.

[0049] The control unit 7 of the cable air supply monitoring system A includes a CPU 61, and is realized by loading a predetermined program onto the CPU 61 and RAM 63, thereby operating the first sensor unit 4, the second sensor unit 5, the output module 66, and the wireless module under the control of the CPU 61, and reading and writing data in the RAM 63 and the auxiliary storage device 64.

[0050] Next, we will explain the operation and usage of the cable air supply monitoring system A. In the following explanation, we will take an example where air is used as the medium of the dry gas, but a medium other than air may also be used.

[0051] At the dry gas supply source in the cable air supply monitoring system A, a known dehumidifier is used to remove or reduce moisture in the air and adjust the relative humidity to be below a predetermined relative humidity standard to produce dry gas.

[0052] Dry gas is supplied from a dry gas supply source to the dry gas supply pipe, and is supplied to the wires 11 in the main cable 1 through the main pipe and branch pipes of the dry gas supply pipe and the air supply section 2 of the first cable band section 14a.

[0053] At this time, the second sensor unit 5 provided in the dry gas supply pipe constantly or at predetermined time intervals measures the relative humidity of the dry gas flowing through the dry gas supply pipe, and the second sensor unit 5 transmits the relative humidity of the dry gas to the CPU 61 as an electrical signal. Upon receiving the electrical signal, the CPU 61 retrieves the relative humidity standard stored in the ROM 62 or the auxiliary storage device 64 and determines whether the relative humidity of the dry gas is equal to or lower than the relative humidity standard. If the relative humidity of the dry gas exceeds the relative humidity standard, the CPU 61 determines that outside air has mixed with the dry gas and that an abnormality has occurred in the dry gas. The CPU 61 determines that an unexpected event (e.g., a failure of the dry gas supply source, a crack or other damage in the dry gas supply pipe, etc.) may have occurred. The CPU 61 issues a warning signal, such as an audible or visual, from the output module 65 to notify the administrator. The manager shall inspect the equipment included in the dry gas supply source, as well as the main and branch pipes of the dry gas supply pipe, check for any malfunctions of the equipment or damage to the dry gas supply pipe (for example, cracks in the dry gas supply pipe, cracks or peeling in the seal, etc.), and take any necessary measures.

[0054] When the second sensor unit 5 is provided in each branch pipe of the dry gas supply pipe, the second sensor unit 5 provided in which branch pipe is experiencing an abnormality in the dry gas is output to the output module 65, so that the manager need only inspect the branch pipe in which the abnormality in the dry gas is occurring, thereby enabling the manager to perform inspection work efficiently.

[0055] Dry gas supplied through the dry gas supply pipe is supplied from the air supply section 2 of the first cable band section 14a to the multiple wires 11 in the main cable 1. The gaps formed between the wires 11 are fully open in the longitudinal direction of the main cable 1, and the dry gas flows through the gaps between the wires 11 in the longitudinal direction of the main cable 1. Under normal conditions, the gaps between the wires 11 are always filled with dry gas flowing in the longitudinal direction of the main cable 1. Because the relative humidity of the dry gas is adjusted to be below a predetermined relative humidity standard, rusting of the wires 11 due to moisture is prevented or reduced, and the wires 11 are maintained in good condition.

[0056] Next, we will explain the flow state of the dry gas supplied into the main cable 1. For example, the dry gas supplied into the main cable 1 from the air supply section 2 of the first cable band section 14a-2 in Figures 1 and 2 branches into two in the main cable 1. The two branched dry gases flow toward the second cable band section 14b-2 and the second cable band section 14b-3, respectively, and are discharged from the exhaust section 3 of the second cable band section 14b-2 and the exhaust section 3 of the second cable band section 14b-3 into the dry gas exhaust pipes.

[0057] Meanwhile, the dry gas supplied from the air supply section 2 of the first cable band section 14a-1 into the main cable 1 is also branched into two in the same manner as above within the main cable 1. One of the two branches of dry gas flows toward the second cable band section 14b-2 and is discharged from the exhaust section 3 of the second cable band section 14b-2 into the dry gas exhaust pipe.

[0058] In this way, dry gas supplied from both the air supply units 2 of the first cable band unit 14a-2 and 14a-1 flows into the exhaust unit 3 of the second cable band unit 14b-2, and the dry gases mix to form a mixed gas. Therefore, even if the relative humidity of the mixed gas flowing into the exhaust unit 3 of the second cable band unit 14b-2 is measured, it is not possible to determine which of the first cable band units 14a-1 (14a-2) has an abnormality in the dry gas flowing in. Furthermore, even if an abnormality occurs in the dry gas flowing in from one of the first cable band units 14a (first dry gas), the dry gas flowing in from the other first cable band unit 14a (second dry gas) may absorb moisture in the first dry gas that exceeds the relative humidity standard, and the relative humidity of the mixed gas as a whole may be maintained at or below the standard, making it impossible to detect an abnormality.

[0059] In the exhaust section 3 of the second cable band section 14b-2, the relative humidity of the mixed gas flowing into this exhaust section 3 is measured. If an abnormality is found in the dry gas, as described above, it is not possible to determine from which of the first cable band sections 14a-1 (14a-2) the dry gas flowing in is abnormal. Therefore, two air supply sections must be inspected: the air supply section X formed between the first cable band section 14a-2 and the second cable band section 14b-2, and the air supply section Y formed between the first cable band section 14a-1 and the second cable band section 14b-2. As a result, there is a problem in that the inspection work for the main cable 1 increases, which increases the burden.

[0060] Therefore, in the above-described cable air supply monitoring system A, for example, in the air supply section X, the first sensor unit 4 is disposed not in the second cable band unit 14b-2 but in the third cable band unit 14c (preferably the third cable band unit 14b-2 next to the second cable band unit 14b-2) located near the second cable band unit 14b-2. That is, the relative humidity of only the dry air circulating in the air supply section X is measured before it is mixed with the dry gas circulating in the air supply section Y.

[0061] Meanwhile, the dry gas supplied to the air supply section 2 of the first cable band 14a-2 branches into two in the main cable 1. The supply pressure of the dry gas in the air supply section 2 of the first cable band 14a-2 is high before it flows through the main cable 1, and the dry gas that flows from the air supply section 2 of the first cable band 14a-2 into the main cable 1 does not flow back after it branches into two. Furthermore, adjustments are made to prevent dry gas from flowing from the second cable band 14b-2 side into the third cable band 14c in which the first sensor unit 4 is disposed. Therefore, within the third cable band 14c in which the first sensor unit 4 is disposed, dry gas flows in one direction, from the first cable band 14a-2 toward the second cable band 14b-2.

[0062] In this way, only the dry air flowing through the air supply section X is the measurement target, and the relative humidity of the dry air is measured by the first sensor unit 4. Therefore, if an abnormality occurs in the dry air, it is sufficient to inspect only the portion of the main cable 1 that constitutes the air supply section X for damage (for example, cracks in the dry gas supply pipe, cracks or peeling in the seal portion, etc.), which makes it possible to reduce and shorten the inspection work for the main cable 1 and also improve the quality of the inspection by reducing the inspection work. Note that although the above explanation has been given using the air supply section X as an example, the same applies to other air supply sections.

[0063] As described above, an air supply section is formed between the air supply section 2 of the first cable band section 14a and the exhaust section 3 of the second cable band section 14b, which are adjacent to each other, dividing the main cable 1 into multiple air supply sections. In each air supply section, a first sensor section 4 is disposed near the second cable band section 14b. This first sensor section 4 measures the relative humidity of only the dry gas flowing through the target air supply section, either continuously or at predetermined time intervals. The first sensor section 4 transmits the relative humidity of the dry gas as an electrical signal to the CPU 61. Upon receiving the electrical signal, the CPU 61 retrieves the relative humidity standard stored in the ROM 62 or the auxiliary storage device 64 and determines whether the relative humidity of the dry gas is equal to or lower than the relative humidity standard. If the relative humidity of the dry gas exceeds the relative humidity standard (does not satisfy the relative humidity standard), the CPU 61 determines that outside air has mixed into the dry gas, causing an abnormality in the dry gas. The CPU 61 then determines that there is a risk of an unexpected event occurring in the main cable 1 that constitutes the air supply section (for example, damage such as a crack has occurred in the main cable 1). The CPU 61 issues a warning signal such as a sound or a display from the output module 65 to notify the manager. The manager then inspects the main cable 1 portion that constitutes the air supply section, checks for damage to the main cable 1 (for example, cracks in the main cable 1, cracks or peeling in the seal portion, etc.), and takes the necessary measures.

[0064] In the above, we have described a case where the output module 65 is configured to issue a warning signal when the relative humidity of the dry gas measured by the first sensor unit 4 and the second sensor unit 5 exceeds a predetermined relative humidity standard, but the issuance of a warning signal is not limited to this case, and the output module 65 may also be configured to issue a warning signal in the following cases, for example.

[0065] As described above, in each gas supply section, the first sensor unit 4 (second sensor unit 5) measures the relative humidity of the dry gas constantly or at predetermined time intervals. The relative humidity of the dry gas measured by the first sensor unit 4 (second sensor unit 5) (hereinafter referred to as the "measured value") is transmitted to the CPU 61 as an electrical signal each time it is measured. The CPU 61 receives the measured value and stores it sequentially in the RAM 63 or the auxiliary storage device 64. Next, the CPU 61 extracts multiple measured values ​​from the measured values ​​stored in the RAM 63 or the auxiliary storage device 64 based on predetermined conditions (e.g., "extract the most recent 10 measured values"). The CPU 61 calculates the arithmetic mean of the extracted measured values ​​and sets this calculated arithmetic mean as a reference value. The CPU 61 calculates the absolute value of the difference between the calculated reference value and the most recent measured value. A predetermined threshold value is stored in the RAM 63 or the auxiliary storage device 64. If the calculated absolute value exceeds the threshold value, the CPU 61 determines that an abnormality has occurred in the dry gas, and that there is a risk of a malfunction in part of the cable air supply management system. The CPU 61 is configured to issue a warning signal, such as an audible or visual, from the output module 65 in the same manner as described above. By determining the measured value of the dry gas using such a determination criterion, it is possible to quickly detect a change in the relative humidity of the dry gas even if the relative humidity of the dry gas does not exceed the relative humidity standard. Therefore, it is possible to inspect the main cable 1 and the like early on and prevent abnormalities from occurring in the dry air circulating within the main cable 1.

[0066] In the above, an example was given in which the most recent 10 measurement values ​​were extracted when extracting measurement values, but this is not limited to this. In the above, the arithmetic mean of the measurement values ​​was used as the reference value, but this is not limited to the arithmetic mean. The reference value may be other statistically calculated values ​​or values ​​calculated using other calculation formulas.

[0067] One or more of the above-mentioned relative humidity standards and reference values ​​may be used as the relative humidity monitoring standards, and if the measured value does not satisfy these monitoring standards, the output module 65 may be configured to issue a warning signal such as a sound or a display in the same manner as described above.

[0068] In the above description, the first sensor unit 4 and the second sensor unit 5 measure the relative humidity of the dry gas, but they may also measure the pressure of the dry gas in addition to the relative humidity. If an abnormality occurs in the main cable 1, the pressure of the dry gas will decrease. By determining a pressure standard for the dry gas in advance and determining the pressure of the dry gas in the same manner as the relative humidity, it is possible to detect malfunctions in the cable air supply monitoring system. [Explanation of symbols]

[0069] 1 main cable 11 wires 2. Air supply unit 3 Exhaust section 3 Exhaust section 4 First sensor section 5 Second sensor section 14a First cable band 14b Second cable band 14c Third cable band A Cable Air Supply Monitoring System B Bridge B1 Main tower B2 Hanger rope B3 Bridge girder

Claims

1. a cable including a plurality of bundled wires, a plurality of covering tubes covering the wires and arranged in the length direction of the wires while forming gaps between opposing end faces of the covering tubes, and a cable band portion closing the gaps between adjacent covering tubes; a plurality of first cable band portions, each of which is one of the cable band portions of the cable and is provided with an air supply portion for supplying dry gas into the cable; a second cable band portion which is one cable band portion present between the adjacent first cable band portions, the second cable band portion having a plurality of cable band portions interposed between it and the first cable band portion and which is provided with an exhaust portion for exhausting dry gas supplied from the air supply portion of the first cable band portion into the cable to the outside of the cable; a first sensor unit disposed on the cable band near the second cable band and configured to measure the relative humidity of the dry gas flowing through the cable; A cable air supply monitoring system characterized by comprising a control unit that issues a warning signal when the relative humidity measured by the first sensor unit does not meet a predetermined relative humidity monitoring standard.

2. The cable air supply monitoring system of claim 1, further comprising a second sensor unit for measuring the relative humidity of the dry gas supplied to the air supply unit of the first cable band unit, and the control unit issues a warning signal when the relative humidity measured by the second sensor unit does not meet a predetermined relative humidity monitoring standard.

3. 3. A cable air supply monitoring system according to claim 1, wherein the cable is a main cable whose end is fixed to an anchorage of a suspension bridge and which supports the bridge girder via a hanger rope.

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