Dehumidification system and dehumidification method for main cable of suspension bridge

Abstract

The present invention discloses a dehumidification system and method for the main cable of a suspension bridge. The dehumidification system includes a dehumidification device and a pipeline connecting the air holes of each dehumidification cable clamp. The dehumidification cable clamp can be a dedicated cable clamp or a sling clamp for hanging slings. The pipeline is located outside the main cable, and the air holes are located at the bottom and top of the dehumidification cable clamp. During the dehumidification process, dry gas is input into the top pipeline at night and maintained at a relatively low pressure compared to conventional dehumidification methods, so that the gas in the main cable is discharged through the bottom air holes; alternatively, dry gas is input into the bottom pipeline during the day and maintained at a relatively low pressure compared to conventional dehumidification methods, so that the gas in the main cable is discharged through the top air holes. The present invention cleverly utilizes the cycle of rising and falling moisture in the main cable during the day and night. The technical solution of the present invention can be used to carry out energy-saving renovation of the dehumidification system in an existing suspension bridge, reduce energy consumption, and save construction investment or maintenance costs.

Description

Technical Field

[0001] The invention relates to the anti-corrosion of steel wires of a main cable of a suspension bridge in a bridge project, and in particular to a dehumidification system and a dehumidification method for the main cable of a suspension bridge. Background Art

[0002] The main cable is one of the most important load-bearing components of a suspension bridge, known as its "lifeline." It is exposed to the atmosphere for long periods of time, subjecting it to various adverse environmental erosion conditions. Furthermore, since the main cable is a non-replaceable component, its lifespan directly impacts the service life of the suspension bridge.

[0003] The usual main cable protection system is to apply a layer of protective putty, such as red lead or zinc powder paste, on the surface of the main cable, wrap it with round galvanized soft steel wire, and then apply anti-corrosion paint on the outer surface of the wrapped steel wire. This traditional main cable protection system actually prevents moisture from invading its interior by sealing the outer layer of the main cable to achieve the purpose of corrosion protection. The vast majority of suspension bridges built in the last century adopted this main cable protection system. However, the results of recent investigations and studies abroad have shown that the protective effect of this protection system is not ideal. This traditional main cable protection measure has been observed and studied for a long time at home and abroad. For example, when Japan opened the main cable steel wire of the Seto Bridge for inspection, it was found that the surface of the main cable was severely corroded over the past ten years, and the rust mainly occurred on the sides and bottom of the main cable, and the protective effect was not good. There is water in the main cable. When the main cable protection system is completed, only a small amount of water is removed from the main cable, and the main cable steel wire will still be corroded by the water trapped inside the main cable. The putty layer and paint layer deteriorate. The paint on the winding surface is affected by harsh external environments such as ultraviolet rays. After aging and cracking, the putty will be directly exposed to the external environment. In addition, the moisture accumulated inside the main cable gradually forms a corrosive environment. A series of factors such as air, moisture, and temperature changes affect the physical and chemical properties of the putty, and eventually cracks, oxidative deterioration, and even powdering will occur, thus losing its protective function. After the paint layer on the surface of the main cable cracks, it is unable to prevent water from penetrating into the main cable.

[0004] Research has found that moisture trapped inside the main cable, which is difficult to drain, evaporates during the day and accumulates at the top. It then condenses at night and sinks to the bottom, a cycle that repeats and is the primary cause of corrosion on the surface and bottom of the wire bundles. However, the wires in the center of the main cable are virtually corrosion-free. Furthermore, simulations have shown that as long as the relative humidity at the sides, top, and bottom of the main cable is kept below 60%, the wires will not rust.

[0005] Japan began researching main cable dehumidification systems in the 1990s. By introducing dry air into the main cables, the system reduces humidity within them, thereby preventing corrosion of the main cable wires. The Runyang Bridge pioneered the use of a main cable dehumidification system for main cable protection on a large-span suspension bridge in China. Typically, the dehumidifier is installed in two relatively spacious locations: on the main tower beam or within the stiffening beam. Fans and cooling equipment, along with control and monitoring systems, are installed simultaneously. Specialized air supply and exhaust clamps are placed along a defined length of the main cable, allowing dry air to enter through the supply clamps and moist air to exit through the exhaust clamps. Monitoring, control, and regulation equipment are also installed at the clamps.

[0006] The air supply pressure should generally not exceed 3kPa to prevent damage to the outer protective layer. At this pressure, the dry gas can be transported along the gaps between the main cable wires for a maximum distance of approximately 200 meters. This requires the installation of multiple dedicated air supply and exhaust clamps along the main cable to provide segmented air supply to the main cable. Conventional cable clamps can be used to double as both air supply and exhaust clamps, reducing the number of dedicated air supply and exhaust clamps. Due to the narrow gaps between the main cable wires and the high resistance to air flow, multiple dehumidification systems are required throughout the bridge, consuming significant power and increasing costs.

[0007] Therefore, it is urgent to change the current situation and find an efficient method for dehumidifying the main cable to reduce the use of dehumidification equipment, reduce electricity consumption, and reduce maintenance costs during bridge operation. Summary of the Invention

[0008] The purpose of the present invention is to solve the deficiencies in the prior art and to propose a dehumidification system and a dehumidification method for the main cable of a suspension bridge.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A dehumidification system for the main cable of a suspension bridge mainly includes a dehumidification device, a wrapping layer on the surface of the main cable of the suspension bridge, a dehumidification cable clamp, air holes connected to the dehumidification cable clamp, and a pipeline of the dehumidification device, wherein the pipeline is located outside the main cable; the air holes are located at the bottom and top of the dehumidification cable clamp, the air holes located at the top are called top air holes, and the air holes located at the bottom are called bottom air holes; the main cable of the entire bridge is divided into multiple dehumidification sections, the top air holes in each dehumidification section are connected in sequence by pipelines to form a top pipeline, and are connected to the dehumidification device; the bottom air holes in each dehumidification section are connected in sequence by pipelines to form a bottom pipeline, and are connected to the dehumidification device.

[0011] A method for dehumidifying the main cable of a suspension bridge adopts the dehumidification system described in claim 1. At night, dry gas is input into the top pipeline and maintained at a set low pressure, and a set negative pressure is maintained in the bottom pipeline; the moisture in the main cable is discharged through the bottom air holes, enters the bottom pipeline, and flows back to the dehumidification equipment.

[0012] Another dehumidification method for the main cable of a suspension bridge adopts the dehumidification system described in claim 1. During the day, dry gas is input into the bottom pipeline and maintained at a set low pressure, and a set negative pressure is maintained in the top pipeline; the moisture in the main cable is discharged through the top air hole, enters the top pipeline, and flows back to the dehumidification equipment.

[0013] Preferably, the dehumidification equipment mainly includes a purification and filtering device, a dehumidifier, a blower and a cooler.

[0014] Preferably, the dehumidification cable clamp includes a dedicated cable clamp and a sling cable clamp for hanging a sling.

[0015] Preferably, the wrapping layer includes a cable-tensioning steel wire layer in a suspension bridge, a sealing material in gaps between adjacent cable-tensioning steel wires, and a sealing material bonded to both inner and outer sides of the cable-tensioning steel wire layer.

[0016] Preferably, the top pipelines of different dehumidification sections are merged into one pipeline and then connected to the dehumidification equipment; the bottom pipelines of different dehumidification sections are merged into one pipeline and then connected to the dehumidification equipment.

[0017] Preferably, a humidity sensor is installed in the pipeline.

[0018] Preferably, a dehumidification system and dehumidification method for the main cable of a suspension bridge, at night, after the humidity in the bottom pipeline exceeds a preset limit, dry gas is input into the top pipeline and maintained at a set low pressure, and a set negative pressure is maintained in the bottom pipeline; the moisture in the main cable will be discharged through the bottom air holes, enter the bottom pipeline, and flow back to the dehumidification equipment until the humidity in the bottom pipeline is lower than the preset limit.

[0019] Preferably, another dehumidification system and dehumidification method for the main cable of a suspension bridge is as follows: during the day, when the humidity in the top pipeline exceeds a preset limit, dry gas is input into the bottom pipeline and maintained at a set low pressure, and a set negative pressure is maintained in the top pipeline; the moisture in the main cable is discharged through the top air hole, enters the top pipeline, and flows back to the dehumidification equipment until the humidity in the top pipeline is lower than the preset limit.

[0020] The beneficial effects of the present invention are:

[0021] 1. The system cleverly utilizes the rising and falling cycle of moisture in the main cable during the day and night, "waiting for the rabbit by the tree" to discharge moisture and reduce energy consumption;

[0022] 2. In this solution, the dry air fed into one side of the main cable is at a lower pressure, while the other side is at negative pressure, which can accelerate dehumidification and reduce the energy consumption of the dehumidification system;

[0023] 3. In addition to being applicable to the initial dehumidification system of a suspension bridge, this technical solution is also convenient for energy-saving transformation of existing dehumidification systems. It is a green and low-carbon technology that does not require additional hardware facilities, thus saving investment.

[0024] 4. The addition of humidity sensors facilitates the automated operation of the dehumidification system, reduces energy consumption and personnel input, and saves expenses.

[0025] 5. The main cable dehumidification system in this solution also solves the corrosion protection of the main cable steel wire in the saddle. Considering its high dehumidification efficiency, the dehumidification equipment has more idle time and can participate in or directly take charge of the dehumidification task in the anchorage during its idle time;

[0026] 6. In this solution, the dry air pressure sent into the main cable side is low, which can avoid damage to the sealing performance of the wrapping layer and reduce maintenance costs;

[0027] 7. The nighttime dehumidification method works during the off-peak period of electricity consumption, making full use of the excess electricity of the nighttime power grid. At the same time, it can enjoy preferential electricity prices and reduce operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a dehumidification system near a dehumidification cable clamp in Example 1;

[0029] Figure 2 A partial enlarged schematic diagram of point C in Example 1;

[0030] Figure 3 A schematic diagram of the structure of a dehumidification system near a dehumidification cable clamp in Example 2;

[0031] Figure 4 A partial enlarged schematic diagram of point D in Example 2.

[0032] In the figure: 1 sling clamp, 2 sling, 3 ear plate, 4 main cable, 5 dehumidification clamp, 6 top pipeline, 7 bottom pipeline, 8 thermometer and hygrometer, 9 data cable, 10 wrapping layer. DETAILED DESCRIPTION

[0033] Example 1

[0034] The technical solution in this embodiment is applicable to regions located in subtropical, temperate, cold temperate, and frigid zones, and operates at night. The nighttime dehumidification method operates during low-power periods, fully utilizing excess power from the nighttime grid while also enjoying preferential electricity prices and reducing operating costs.

[0035] The suspension bridge in this embodiment is a conventional twin-tower, three-span suspension bridge, which already has a dehumidification system. This existing dehumidification system delivers dry gas into the main cables through the air supply clamps. The dry gas, at a pressure of 3 kPa, travels longitudinally through the main cables and is discharged through the exhaust clamps. This high air supply pressure consumes significant energy and can easily damage the protective coating on the main cables. Energy-saving and consumption-reducing improvements are urgently needed.

[0036] The energy-saving renovation fully utilizes the equipment and components of the existing dehumidification system. The existing dehumidification system consisted of two sets, housed within the top beams of the two main towers. Each set primarily consisted of a purification filter, a dehumidifier, a blower, a cooler, and a newly installed controller. Each set of dehumidification equipment was responsible for the main cables of the upstream and downstream side spans of its respective tower, as well as the half-span main cables of the upstream and downstream main spans. The bridge's main cables were divided into eight dehumidification sections. The outer layer of the suspension bridge's main cables, known as the sheath, primarily consists of a layer of tensioning wires, sealing material within the gaps between adjacent tensioning wires, sealing material bonded to both the inner and outer sides of the tensioning wires, and additional wrapping tape for enhanced airtightness. The protective covers on the tower saddles of the suspension bridge were sealed, ensuring an airtight space between the covers and the saddles. The dehumidification cable clamps still utilized the air supply and exhaust clamps from the existing dehumidification system, but the air holes were modified to seal the existing holes and re-perforate the dehumidification cable clamps. The new air holes are located at the bottom and top of the dehumidification cable clamp and have internal threads. The one at the top is called the top air hole, and the one at the bottom is called the bottom air hole. The pipeline is made of polyethylene tube, which is a hot-melt transparent plastic with an inner diameter of 12mm and a wall thickness of 2mm. On the outside of the main cable, the top air holes in each dehumidification section are connected in sequence with pipelines to form a top pipeline, and are connected to the dehumidification equipment; the various pipeline sections of the top pipeline are connected with a tee by hot-melt connection; the air hole joint has a corresponding external thread and is screwed into the air hole; there is a connecting pipeline to connect the air hole joint to the tee; similarly, the bottom air holes in each dehumidification section are connected in sequence with pipelines to form a bottom pipeline, and are connected to the dehumidification equipment. See the structural diagram of the dehumidification system near a dehumidification cable clamp in the dehumidification section. Figure 1 The left side of the figure is the bridge tower side. The outer layer of the main cable 4 is a conventional cable tensioning wire layer. The suspension bridge adopts a sling clamp 1 with an upper and lower ear plate 3. The sling 2 adopts a prefabricated parallel steel wire form. The dehumidification cable clamp 5 is also an upper and lower half type. The top pipeline 6 is connected to the upper air hole of the dehumidification cable clamp 5 through a connecting pipeline, and the bottom pipeline 7 is connected to the lower air hole of the dehumidification cable clamp 5 through a connecting pipeline. A partial enlarged schematic diagram of the dehumidification cable clamp 5 is shown in FIG. Figure 2 A thermometer and hygrometer 8 is installed on the bottom pipeline 7. A data cable 9 is routed above the main cable and connected to a controller inside the pylon. The outer layer 10 protects the main cable wires and is required to be highly airtight in the dehumidification system. High airtightness is also required at the connections between the wrapping 10 and all cable clamps, as well as at the connections between the wrapping 10 and all cable saddles.

[0037] The corresponding dehumidification method is that at night, according to the settings in the controller, when the humidity in the bottom pipeline 7 exceeds 50%, the dehumidification equipment starts, inputs dry gas into the top pipeline 6 of the section, and maintains a low pressure of 300Pa, and maintains a negative pressure of -200Pa in the bottom pipeline 7; the moisture in the main cable 4 will be discharged through the bottom air holes, enter the bottom pipeline 7, and flow back to the dehumidification equipment until the humidity in the bottom pipeline 7 is lower than 40%, and the dehumidification equipment stops working.

[0038] This solution mainly utilizes the fact that the temperature is low at night and the moisture in the main cable sinks inside the main cable.

[0039] This technical solution cleverly utilizes the rising and falling cycle of moisture in the main cable during the day and night, "sitting by the tree and waiting for the rabbit", expelling moisture and reducing energy consumption; the pressure of dry air sent into the main cable is one order of magnitude lower than the air supply pressure of the original dehumidification system, reducing the energy consumption of the dehumidification system; the addition of temperature and humidity sensors facilitates the automatic operation of the dehumidification system, reduces energy consumption and personnel input, and saves expenses; this technical solution achieves the goal of green and low carbon by carrying out consumption-reducing transformation of the existing dehumidification system, and the consumption-reducing transformation does not require the addition of large hardware facilities, saving investment; using a lower gas pressure can avoid damage to the sealing performance of the wrapping layer and reduce maintenance costs; the main cable dehumidification system in this solution also solves the corrosion protection of the main cable steel wire in the saddle. Considering its high dehumidification efficiency, the dehumidification equipment has more idle time and can participate in or be directly responsible for the dehumidification task in the anchor during idle time.

[0040] Example 2

[0041] The technical solution in this embodiment is applicable to the equatorial zone, tropical, subtropical and subtropical regions, and the dehumidification system works during the day. Figure 3 and Figure 4 To facilitate installation and maintenance, the bottom pipeline 7 is placed above the main cable 4 , and the thermometer and hygrometer 8 is installed on the top pipeline 6 .

[0042] During the day, when the thermometer and hygrometer 8 shows that the humidity in the top pipeline 6 exceeds 50%, the controller starts the dehumidification equipment, inputs dry gas into the bottom pipeline 7, and maintains a low pressure of 300Pa, and maintains a negative pressure of -200Pa in the top pipeline 6; the moisture in the main cable 4 is discharged through the top air hole of the dehumidification cable clamp 5, enters the top pipeline 6, and flows back to the dehumidification equipment until the humidity in the top pipeline 6 is lower than 40%, and the dehumidification equipment stops working.

[0043] This solution mainly utilizes the fact that the temperature is high during the day and the moisture inside the main cable rises inside the main cable.

Claims

1. A dehumidification system for a suspension bridge main cable, comprising a dehumidification device, a wrapping layer on the surface of the suspension bridge main cable, a dehumidification cable clamp, an air hole connecting the dehumidification cable clamp, and a pipeline for the dehumidification device, characterized in that: The pipeline is located outside the main cable; The air holes are located at the bottom and top of the dehumidification cable clamps. The top air holes are called top air holes, and the bottom air holes are called bottom air holes. The main cables of the entire bridge are divided into multiple dehumidification sections. The top air holes in each dehumidification section are connected in sequence by pipelines to form a top pipeline, which is connected to the dehumidification equipment. The bottom air holes in each dehumidification section are connected in sequence by pipelines to form a bottom pipeline, which is also connected to the dehumidification equipment. At night, dry gas is input into the top pipeline, and moisture in the main cables is discharged through the bottom air holes. During the day, dry gas is input into the bottom pipeline and the moisture in the main cable is discharged through the top air holes.

2. The dehumidification system for a suspension bridge main cable according to claim 1, characterized in that: The dehumidification equipment includes a purification and filtering device, a dehumidifier, a blower and a cooler.

3. The dehumidification system for a suspension bridge main cable according to claim 1, characterized in that: The dehumidification rope clamp comprises a special rope clamp and a sling rope clamp for hanging a sling.

4. The dehumidification system for a suspension bridge main cable according to claim 1, characterized in that: The wrapping layer includes a cable-tightening steel wire layer in a suspension bridge, sealing materials in gaps between adjacent cable-tightening steel wires, and sealing materials bonded to both sides of the cable-tightening steel wire layer.

5. The dehumidification system for a suspension bridge main cable according to claim 1, characterized in that: The top pipelines of different dehumidification sections are merged into one pipeline and then connected to the dehumidification equipment; the bottom pipelines of different dehumidification sections are merged into one pipeline and then connected to the dehumidification equipment.

6. The dehumidification system for a suspension bridge main cable according to claim 1, characterized in that: A humidity sensor is installed in the pipeline.

7. A method for dehumidifying a main cable of a suspension bridge, characterized in that: The dehumidification system according to claim 1 is used. At night, dry gas is input into the top pipeline and the air supply pressure is maintained at an order of magnitude lower than that of a conventional main cable dehumidification system, and a set negative pressure is maintained in the bottom pipeline. The moisture in the main cable will be discharged through the bottom air holes, enter the bottom pipeline, and flow back to the dehumidification equipment.

8. A method for dehumidifying the main cable of a suspension bridge, characterized by: The dehumidification system according to claim 1 is used. During the day, dry gas is input into the bottom pipeline and the air supply pressure is maintained at an order of magnitude lower than that of a conventional main cable dehumidification system, and a set negative pressure is maintained in the top pipeline; the moisture in the main cable is discharged through the top air holes, enters the top pipeline, and flows back to the dehumidification equipment.

9. A method for dehumidifying a main cable of a suspension bridge according to claim 7, wherein the method adopts the dehumidification system according to claim 6, characterized in that: At night, when the humidity in the bottom pipeline exceeds the preset limit, dry gas is input into the top pipeline and the air supply pressure is maintained at an order of magnitude lower than that of the conventional main cable dehumidification system, and the set negative pressure is maintained in the bottom pipeline; the moisture in the main cable will be discharged through the bottom air holes, enter the bottom pipeline, and flow back to the dehumidification equipment until the humidity in the bottom pipeline is lower than the preset limit.

10. A dehumidification method for a main cable of a suspension bridge according to claim 8, wherein the method adopts the dehumidification system according to claim 6, characterized in that: During the day, when the humidity in the top pipeline exceeds the preset limit, dry gas is input into the bottom pipeline, and the air supply pressure is maintained at an order of magnitude lower than that of the conventional main cable dehumidification system, and a set negative pressure is maintained in the top pipeline; the moisture in the main cable is discharged through the top air holes, enters the top pipeline, and flows back to the dehumidification equipment until the humidity in the top pipeline is lower than the preset limit.

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