A flame retardant device for stay cables that can expand in both directions when exposed to heat, and its installation method

Abstract

The present invention relates to a bidirectionally expandable stay cable flame retardant device and its installation method. The device includes a fire retardant ring 1 and a positioning jig 2. The fire retardant ring is fixed to the surface of the stay cable body 7 using the positioning jig. The fire retardant ring covers the stay cable body. When exposed to heat, the fire retardant ring expands inward to encase the stay cable body and expands outward to insulate the stay cable body on both sides of the fire retardant ring. The stay cable body where the fire retardant ring is installed is wrapped with weather-resistant fire tape, and the fire retardant ring is installed outside the fire retardant tape. The fire retardant ring includes a fire retardant ring casing 9 and a fire retardant core 10, which is installed inside the fire retardant ring casing. This application uses a bidirectionally expandable fire retardant core as the central component of the fire retardant. Taking advantage of its thermal expansion properties, the fire retardant core envelops the cable body inward and expands outward to insulate the cable body on both sides, preventing the spread of fire.

Description

[Technical Field]

[0001] The present invention relates to a flame retardant for stay cables, and more particularly to a flame retardant based on the principle of expansion when exposed to heat, and a method for installing the same. [Background technology]

[0002] While a large cable-stayed bridge was in use, smoke and fire broke out at the end of the 2# stay cable on the east side of a certain bridge, near the main tower. Relevant agencies, including construction, design, installation, fire department, and traffic police, rushed to the scene within the first hour and took action. The 2# stay cable broke and fell to the bridge deck, but no personnel were killed or injured, and no vehicles were damaged. Initial analysis revealed that the cause of the fire was a short circuit in the wire connector of the 2# stay cable's lighting circuit, causing part of the cable to ignite and burn. Because there was no fire protection device, the flames spread along the stay cable sheath and cable body, deforming and burning some of the cable support members, which are relatively sensitive to temperature.

[0003] The two main types of stay cables that are commonly used in cable-stayed bridges are parallel wire stay cables and strand stay cables. Parallel wire stay cables are made by tightly arranging high-strength galvanized or zinc-aluminum alloy wires in a regular hexagon or a notched regular hexagon, lightly twisting them counterclockwise at a twist angle of 2° to 4°, wrapping them clockwise with high-strength polyester fiber tape, and then hot-extruding a high-density polyethylene (PE) sheath directly around the wires for protection. These are then combined with cold-forged bolt-head anchors. The free area of ​​parallel wire stay cables uses a two-layer protection system consisting of galvanized aluminum alloy wires and a two-layer hot-extruded HDPE jacket.

[0004] The strand stay cable is made of a single strand with a hot-extruded polyethylene (PE) sheath to form a strand bundle, and the outer layer of the entire bundle is a two-layer synchronously extruded high-density polyethylene (HDPE) protective sleeve to form a free stretch area, and one clip-type tension end anchor (including a nut) and one fixed end anchor (excluding a nut) are arranged at both ends. The free area of ​​the strand stay cable adopts a four-layer protection system consisting of a zinc-plated / epoxy layer on the strand, oil-based wax, a strand hot-extruded PE sheath, and an HDPE jacket.

[0005] In both of these stay cable structures, the melting points of the wires, which are the main load-bearing members, are relatively high. Therefore, short-term heating only reduces their strength and elastic modulus, making breakage relatively unlikely. However, the high-density polyethylene sheaths protecting the stay cable wires have fairly low softening, melting, and ignition points. They soften at around 120°C, melt at around 200°C, and burn at around 342°C. Therefore, if a fire breaks out in a stay cable, the high-density polyethylene sheath first softens and melts, and once it has burned to a certain extent, the high-density sheath will burn. The flames will spread along the polyethylene sheath of the stay cable. The high-density polyethylene sheath melts and deforms due to the flames and high temperatures, and if it burns through, a hole will form. The flames will then spread further through the hole, increasing the area of ​​the stay cable that is damaged by the fire. Furthermore, in strand stay cable systems, the cable itself and anchorages contain large amounts of grease, which acts as a fuel additive, accelerating the spread of fire. Therefore, it is extremely important for fire protection of stay cables to prevent and block the spread of flames on the polyethylene sheath and cable body of the stay cable. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] (none) Summary of the Invention

[0007] In contrast to the conventional operation of stay cables, the present invention presents a stay cable fire prevention device and its installation method that can be installed on the stay cable and achieve bidirectional expansion by preheating (heat reception) to prevent the spread of fire.

[0008] The technical method adopted in this invention is as follows: A flame-retardant device for stay cables that can be expanded bidirectionally by preheating (heat reception) includes a flame-retardant ring and a positioning jig, the flame-retardant ring is fixed to the surface of the stay cable body by the positioning jig, the flame-retardant ring covers the stay cable body, and when heated, the flame-retardant ring expands inward to encase the stay cable body and expands outward to insulate the stay cable body on both sides of the flame-retardant ring.

[0009] In one embodiment of the present application, the fire-retardant ring has an integral structure, and the stay cable body passes through the fire-retardant ring, or the fire-retardant ring has a half structure, and is installed so as to wrap around the stay cable body.

[0010] In one embodiment of the present application, the stay cable body portion where the flame retardant ring is to be installed is wrapped with weather-resistant fire tape, and the flame retardant ring is installed further outside the fire retardant tape. Because the flame retardant ring does not come into direct contact with the cable body, it is possible to avoid pressing and destroying the high-density polyethylene layer on the surface of the cable body.

[0011] In one embodiment of the present application, the fire-retardant ring includes a fire-retardant ring casing, a fire-retardant core, and a buckle, the fire-retardant core being installed inside the fire-retardant ring casing, and the buckle being fitted to the outside of the fire-retardant ring casing. The fire-retardant ring casing is used to provide daily protection for the fire-retardant core and reduce environmental interference with the fire-retardant core. The fire-retardant ring casing is preferably made of high-density polyethylene.

[0012] In one embodiment of the present application, the flame-retardant core material has a ring structure, the flame-retardant ring casing has a hollow ring structure, the flame-retardant ring casing includes a flame-retardant ring cylinder, a flame-retardant ring upper cover plate, and a flame-retardant ring lower cover plate, the flame-retardant core material is installed inside the flame-retardant ring cylinder, the flame-retardant ring upper cover plate and the flame-retardant ring lower cover plate are installed at the upper and lower ends of the flame-retardant ring cylinder, respectively, and the flame-retardant core material is fixed inside the flame-retardant ring cylinder.

[0013] In one embodiment of the present application, the flame-retardant ring casing is made of high-density polyethylene material, and its thickness is not less than 3 mm. The inner diameter of the flame-retardant ring casing is 1 to 3 mm larger than the outer diameter of the stay cable body. The inner diameter D1, outer diameter D2 and height H of the flame-retardant core material shall be determined by referring to the table below.

[0014] [Table 1]

[0015] In one embodiment of the present application, the surface of the fire-retardant ring casing is machined with a positioning groove, which is used to install the buckle, and the buckle fastens the half-structured fire-retardant ring casing together. The half-structure of the fire-retardant ring casing is convenient for installing the fire-retardant ring, adjusting the installation position of the fire-retardant ring on the cable body, and for subsequent maintenance and replacement.

[0016] In one embodiment of the present application, the positioning jig is installed at the lower end of the flame retardant ring, the bottom of the flame retardant ring is supported on the positioning jig, the positioning jig has a half structure and wraps around the outside of the diagonal cable body, and a 5mm to 10mm thick silicone rubber is installed in the inner hole of the positioning jig, and the silicone rubber wraps around the outside of the diagonal cable body. The contact between the silicone rubber and the cable body protects the polyethylene sheath layer on the surface of the cable body on a daily basis and prevents damage to the cable body surface caused by the installation of the positioning jig.

[0017] In one embodiment of the present application, a connecting hole is provided on the surface of the positioning jig, and a connecting member is installed in the connecting hole to connect the positioning jig to the flame-retardant ring, or a positioning member is installed in the connecting hole to form an outer positioning limit for the flame-retardant ring, thereby ensuring reliable support and positioning of the positioning jig relative to the flame-retardant ring.

[0018] Since fires in stay cables are mainly caused by combustion from vehicles traveling on the bridge surface or construction work at the tower ends and bridge ends, not only are pipes buried in advance at the bridge ends, but flame retardant devices that can achieve bidirectional expansion (can expand both inward and outward) through preheating (heat reception) are installed in areas that will be affected by flames when vehicles burn and in important locations such as the tower ends, forming isolation at the point where the fire breaks out in the stay cable, blocking the flames from spreading along the surface of the cable body, and preventing the flames from spreading along the body of the stay cable after the high-density polyethylene sheath has burned and causing further damage.

[0019] The flame retardant device designed in this application has a simple structure, is easy to attach to the cable body, and does not interfere with the structure of the stay cable itself, making it convenient for widespread application. This application uses a two-way expanding flame retardant core material as the central component of the flame retardant, and utilizes its property of expanding when exposed to heat to wrap the cable body inward to prevent the spread of flames, and expands outward to block the cable bodies on both sides to prevent the spread of fire.

[0020] The inventor of the present application further hopes to achieve the function of extinguishing the fire through the structural design of the fire prevention ring and the positioning jig, and the related embodiment is as follows:

[0021] a low-melting-point colloid is disposed at the bottom of the cavity; the inner sleeve and the outer sleeve are fixed together by the low-melting-point colloid; a liquid outlet is disposed at the inner lower part of the outer sleeve, communicating with the double layer; the outer end face of the liquid outlet is bonded to the outer wall of the inner sleeve; a low-melting-point seal is fixed to the inner end of the liquid outlet; a core ring with a C-shaped cross section is fixed to the lower part of the inner sleeve; a flame-retardant core is disposed within the core ring; and the flame-retardant core is fixed to the core ring with fireproof tape.

[0022] The inner sleeve is composed of two symmetrically arranged inner half sleeves, and a first fastening groove is provided on the outer side of the bottom end of each of the two inner half sleeves, and the bottom end between the two inner half sleeves is fixed by the first fastening groove and a first buckle.

[0023] The outer sleeve is composed of two symmetrically arranged outer half sleeves, and the two outer half sleeves each have a second fastening groove on their circumferential sides, and the two outer half sleeves are fixed together by the second fastening groove and the second buckle.

[0024] An end sleeve is provided at the top end of the outer sleeve, and a locking edge is provided on the peripheral side of the end sleeve. The tightening jig includes a pair of symmetrically arranged half-ring bodies, the two half-ring bodies being connected to each other by tightening bolts, and a locking groove that engages with the locking edge is fixed to the lower part of the half-ring body.

[0025] The fireproof ring and tightening jig are fitted to the outside of the diagonal cable body, silicone rubber is provided inside the half-ring body, the inner wall of the silicone rubber is bonded to the outer wall of the diagonal cable body, and an avoidance gap is formed between the inside of the core ring and the outer wall of the diagonal cable body.

[0026] An escape port is formed at the top end of the inner sleeve, and the escape port is opposite the position of the liquid outlet. A guide rib is provided on the peripheral side surface of the inner sleeve, and a notch is provided on the barrier edge, and the guide rib slides along the guide groove.

[0027] The above-mentioned flame prevention device having a fire extinguishing function has the following beneficial effects. 1. In this invention, the expandable inner and outer sleeves are designed as a fire-retardant ring, so that when the fire spreads to a predetermined point, the inner sleeve will expand spontaneously. At the same time, combined with the design of a fire-retardant core that can expand when exposed to heat, the fire-retardant point can be completely covered within the inner sleeve, and the fire-retardant core provides fire protection below the fire-spread point. The fire-extinguishing liquid in the outer sleeve is designed to extinguish the space between the inner sleeve and the stay cable body, providing fire-extinguishing protection above the fire-spread point, preventing the fire from spreading along the surface of the cable body and preventing the fire from spreading along the stay cable body after the high-density polyethylene sheath has burned and causing further damage.

[0028] 2. The present invention is characterized in that the flame-retardant core material is designed to expand when preheated (exposed to heat), and when exposed to heat, the polyethylene sheath, which has already softened or melted, is pressed inward, thereby blocking the fire spread point below the fire spread point. At the same time, the space between the inner sleeve and the diagonal cable body is blocked, and the fire spread point is completely limited to within the inner sleeve. This not only blocks air for combustion, but also provides space for the fire-extinguishing liquid, thereby improving the fire-retardant effect of the flame-retardant ring.

[0029] 3. The inner sleeve and outer sleeve of the present invention are connected and fixed via a low-melting-point colloid, which has the function of identifying when a fire has spread to a specified location. When the fire has spread to a location close to the flame-retardant ring, the low-melting-point colloid spontaneously melts, causing the inner sleeve to spontaneously extend and cover the spread point.

[0030] 4. In this invention, the liquid outlet is sealed with a low-melting-point seal, which functions as a switch when the fire spreads to a specified location. When the fire spreads to a location close to the flame-retardant ring, the low-melting-point seal melts spontaneously, opening the liquid outlet.

[0031] 5. The present invention designs the inner sleeve, outer sleeve and fastening jig as two symmetrically installed structural members, which can be quickly installed on the stay cable body, which is convenient for the installation, removal, maintenance and replacement of the fire protection device, and also convenient for workers to operate.

[0032] Of course, it is not necessary to simultaneously achieve all of the above advantages in order to practice any product of the present invention. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a schematic view of the installation of a stay cable flame retardant device in accordance with the first embodiment of the present invention. [Figure 2] FIG. 2 is a central cross-sectional view of the flame retardant device in Example 1 of the present invention. [Figure 3] FIG. 3 is a central cross-sectional view of the flameproof ring cylinder in Example 1 of the present invention. [Figure 4] FIG. 4 is a structural schematic diagram of the upper cover plate of the flame retardant ring or the lower cover plate of the flame retardant ring in Example 1 of the present invention. [Figure 5] FIG. 5 is a schematic diagram of the structure of the flameproof ring casing in Example 1 of the present invention. [Figure 6] FIG. 6 is a central cross-sectional view of the flame retardant device according to the first embodiment of the present invention after assembly. [Figure 7] FIG. 7 is a schematic view of the installation of the flame retardant device in Example 1 of the present invention. [Figure 8] Figure 8 is a structural schematic diagram of the positioning jig in Example 1 of the present application (the explanations of the symbols in Figures 1 to 8 are moved to the end of this specification). [Figure 9] FIG. 9 is a structural schematic diagram of the flame retardant device in Example 2 of the present invention. [Figure 10] FIG. 10 is a structural cross-sectional view of the flame retardant device in the normal state according to the second embodiment of the present invention. [Figure 11] 11 is a cross-sectional view of the structure of the flame retardant device in Example 2 of the present invention when flame retardant is in operation (the explanation of the symbols in FIGS. 9 to 11 is moved to the end of this specification). DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in more detail below in connection with the drawings, but the described embodiments are merely illustrative and are intended to be used to interpret the present invention and should not be understood as limiting the present invention. The text descriptions in the present embodiments correspond to the drawings, and the orientation descriptions are also based on the drawings, so they should not be understood as limiting the scope of protection of the present invention.

[0035] [Example 1] As shown in Figures 1 to 9, the stay cable fireproofing device includes a fireproof ring 1 and a positioning jig 2, and the fireproof ring 1 includes a fireproof ring casing 9, a fireproof core material 10, and a buckle 11. The principle by which the fireproofing device can prevent the spread of fire along the high-density polyethylene sheath is as follows. When a fire breaks out in the stay cable's main body, the polyethylene flame-retardant ring casing of the flame-retardant device first softens (around 120°C), melts (around 180°C), and burns (345°C). The flame-retardant core of the flame-retardant device, attached to the outside of the stay cable's polyethylene sheath, is exposed to the flame and high temperature, and a chemical reaction occurs, causing it to rapidly expand. This expansion forms a dense, strong carbonized layer, which expands outward to form a large flame-retardant ring. At the same time, the softened or melted polyethylene sheath is pressed inward, quickly sealing any holes formed by the heat-induced softening or burning of the polyethylene sheath. This prevents the flame from spreading along the polyethylene sheath to the tower or bridge end, preventing the fire from spreading. This prevents the cable's support from failing, especially at anchor points, due to widespread combustion in the main cable. The flame-retardant ring can be either a one-piece or half-piece type. When an integrated flame retardant is used as the flame retardant, the cable body is pulled in before the anchor is driven into the stay cable.

[0036] The technical requirements for stay cable fire protection devices and their associated components are as follows: 1. The flame-retardant ring casing of the flame-retardant device is made of high-density polyethylene and is no less than 3mm thick. The inner diameter of the casing (fire-retardant ring casing) is 1-3mm larger than the outer diameter of the polyethylene sheath of the stay cable body. When the polyethylene sheath of the stay cable burns, the fire-retardant ring casing melts first, ensuring that the fire-retardant core can rapidly expand 20-40 times inward and outward at the same time, forming a huge fire-retardant ring and effectively preventing the fire from spreading along the cable body. The fire-retardant ring casing is made of high-density polyethylene, which has relatively high aging resistance. The performance parameters of this polyethylene material are as shown in the table below.

[0037] [Table 2]

[0038] The processing method for high-density polyethylene casing (fire-retardant ring casing) is as follows. 1) Hot extrude a high-density polyethylene sleeve based on the design dimensions, cut the material according to the required height to form a cylindrical body for the high-density polyethylene casing of the stay cable flame retardant device, process two positioning grooves with a width of 10 to 20 mm and a depth of 1 to 2 mm on the cylindrical body, and then cut the cylindrical body open from the center line. 2) Based on the design requirements, the upper and lower cover plates of the high density polyethylene casing of the flame retardant device are processed and cut along the center line to form two semicircular rings. 3) Using a hot melt welding gun specifically for polyethylene or an ultrasonic welding gun specifically for polyethylene, the upper and lower cover plates of the high-density polyethylene casing and the cylindrical body are welded together to form the high-density polyethylene casing of the flame retardant device, i.e., the flame retardant ring casing.

[0039] 2. The flame-retardant core material of the flame-retardant device may be either a chemical expansion type flame retardant or a physical expansion type flame retardant.

[0040] Chemical intumescent flame retardants are composed of three components: an acid source (dehydrating agent), a carbon source (carbon-forming agent), and a gas source (blowing agent). The acid source is typically phosphoryl phosphate chloride or ammonium polyphosphate. The carbon source is typically a polyhydroxy compound or carbohydrate with a relatively high carbon content, forming the base for the foamed carbonized layer. Examples include polyhydroxy compounds with a relatively high carbon content, such as phenolic resins, polyamides, erythritol, maltose, and starch. The gas source, also known as the foaming source, includes melamine, dicyandiamide, ammonium polyphosphate, and urea. These gas source materials release large amounts of flame-retardant gas upon thermal decomposition, and the foaming effect is achieved by the expansion of the resulting carbonized layer. To summarize, the flame-retardant mechanism of chemical intumescent flame retardants is as follows: When heated, the acid source decomposes to produce a dehydrating agent, which then forms an ester with the carbon-forming agent. The ester then undergoes dehydration cross-linking to form carbon. At the same time, the foaming agent releases a large amount of gas, helping to expand the carbonized layer. A thick carbon layer increases the temperature gradient between the polymer surface and the carbon layer surface, making the polymer surface temperature significantly lower than the flame temperature, reducing the possibility of the polymer further decomposing and releasing flammable gases, while also blocking the intrusion of external oxygen, so it can act as a flame retardant for the polymer for a considerably long time.

[0041] The core material of the flame retardant device can also be made of physical expandable graphite material, which expands rapidly at high temperatures to extinguish the flame, and the resulting graphite expander material coats the surface of the substrate, blocking the radiation of heat energy and contact with oxygen. The acid groups in the double layer are also released during expansion, accelerating the carbonization of the substrate, and a variety of flame retardant methods can be used to achieve good results.

[0042] The thermal expansion volume of the flame retardant core material of the flame retardant device can reach 20 to 40 times its original volume.

[0043] The flame retardant core material of the flame retardant device is a half-ring shape, and the relevant dimensions of the ring shape are determined according to the table below.

[0044] [Table 3]

[0045] The schematic diagram of the flame retardant device after assembly is shown in Figure 6.

[0046] 3. To prevent the flame retardant device housing and flame retardant core material from colliding with or rubbing against the high-density polyethylene sheath during operation of the stay cable, a 3 to 6 mm thick weather-resistant fire tape (e.g., polyvinyl fluoride tape) is wrapped around the location where the flame retardant device is installed.

[0047] 4. To prevent the fire-retardant ring from falling off, a flange with holes is installed on the fire-retardant ring casing and connected to a positioning jig below, thereby realizing the positioning of the fire-retardant ring and preventing it from slipping off during operation of the cable-stayed bridge.The positioning jig for the half-type fire-retardant device can be installed before driving anchors into the stay cables, or after driving the anchors into the stay cables, or after the stay cables have been erected.

[0048] 5. A positioning jig 2 is installed at the bottom of the flame retardant device. The positioning jig has a half-type structure, and the two components are connected with screws 13. To protect the polyethylene sheath of the stay cable from damage caused by the jig, a silicone rubber 12 with a thickness of 5 to 10 mm is installed in the inner hole of the jig. The Shore hardness is 50 to 60.

[0049] [Example 2] As shown in Figures 9 to 11, this embodiment relates to a fire-extinguishing device, which includes a fire-retardant ring and a clamping jig 1, the fire-retardant ring includes an inner sleeve 2 and an outer sleeve 3, the outer sleeve 3 is provided with a double layer 301, the double layer 301 is filled with a fire-extinguishing liquid (clean water or fine sand), the inner sleeve 2 is slidably installed in the outer sleeve 3, the outer edge of the top end of the inner sleeve 2 and the inner edge of the bottom end of the outer sleeve 3 are both provided with barrier edges 201, a cavity 202 is formed between the inner sleeve 2 and the outer sleeve 3, and a low-melting-point colloid 203 is filled at the bottom of the cavity 202. The inner sleeve 2 and the outer sleeve 3 are fixed together by a low-melting colloid 203, and a liquid outlet 302 communicating with the double layer 301 is provided at the lower inside of the outer sleeve 3, the outer end surface of the liquid outlet 302 is attached to the outer wall of the inner sleeve 2, and a low-melting seal 303 is fixed to the inner end of the liquid outlet 302, and a core ring 204 with a C-shaped cross section is fixed to the lower inside of the inner sleeve 2, and a flame-retardant core 205 is provided within the core ring 204, and the flame-retardant core 205 is fixed within the core ring 204 by fireproof tape 206 (e.g., polyvinyl fluoride tape).

[0050] The inner sleeve 2 is composed of two symmetrically arranged inner half sleeves 207, each with a first fastening groove 208 on the outside of the bottom end of the two inner half sleeves 207, and the bottom end between the two inner half sleeves 207 is fixed by the first fastening groove 208 and a first buckle (209). An escape port 210 is opened at the top end of the inner sleeve 2, and the escape port 210 is opposite the position of the liquid outlet 302. A guide rib is provided on the peripheral side of the inner sleeve 2, and a notch is provided on the barrier edge 201, and the guide rib slides along the guide groove.

[0051] The outer sleeve 3 is composed of two symmetrically arranged outer half sleeves 306, each of which has a second fastening groove 307 formed on its circumferential surface, and the two outer half sleeves 306 are fastened together by the second fastening groove 307 and a second buckle 308. An end sleeve 304 is provided at the top end of the outer sleeve 3, and a locking edge 305 is provided on the circumferential surface of the end sleeve 304. The fastening jig 1 includes a pair of symmetrically arranged half rings 101, which are connected to each other by a fastening bolt, and a locking groove 102 that engages with the locking edge 305 is fixed to the bottom of the half rings 101.

[0052] The fireproof ring and tightening jig 1 are fitted to the outside of the diagonal cable main body 4, a silicone rubber pad 103 is provided inside the half-ring body 101, the inner wall of the silicone rubber pad 103 is bonded to the outer wall of the diagonal cable main body 4, and an avoidance gap is formed between the inside of the core ring 204 and the outer wall of the diagonal cable main body 4.

[0053] The operating principle of the flame retardant device of this embodiment is as follows. When a fire breaks out in the sheath layer on the surface of the stay cable main body 4 and spreads to a position close to this device, the combustion temperature spreads and melts the low-melting-point colloid 203 and the low-melting-point seal 303. The low-melting-point seal 303 is a sealing point formed by the low-melting-point colloid. The low-melting-point colloid melts in the high-temperature environment caused by the flames.

[0054] As the low-melting-point colloid 203 melts, the bond between the inner sleeve 2 and the outer sleeve 3 is released, and the inner sleeve 2 descends due to gravity, at which point the burning point is within the inner sleeve 2 and above the flame-retardant core 205, so the burning point is enveloped within the inner sleeve 2. The fire-resistant tape 206 melts with the high temperature, and the flame-retardant core 205 expands due to the heat, and the inside of the expanded flame-retardant core 205 envelopes the outside of the already burning cable body below the burning point.

[0055] The melting of the low-melting-point seal 303 corresponds to the opening of the liquid outlet 302. As the inner sleeve 2 slides downward along the outer sleeve 3, the end of the liquid outlet 302 is stuck to the outer wall of the inner sleeve 2, continuing to seal to a certain extent. After the inner sleeve 2 completely falls, the liquid outlet 302 is exposed to the outside, and the fire-extinguishing liquid in the double layer 301 is discharged by gravity into the gap between the inner sleeve 2 and the diagonal cable body 4, and the bottom of the gap is sealed by the expanded flame-retardant core material 205, thereby extinguishing the fire points remaining in the inner sleeve 2 and directly blocking the spread of fire points. [Explanation of symbols]

[0056] In Figures 1 to 8, 1 is a fire-retardant ring, 2 is a positioning jig, 201 is a connection hole, 3 is a rain cover for the bridge end of the stay cable, 4 is a pre-buried pipe for the bridge end of the stay cable, 5 is a white high-density polyethylene sheath, 6 is a black high-density polyethylene sheath, 7 is a bundle of stay cable wires, 8 is weather-resistant fire tape, 9 is a fire-retardant ring casing, 10 is a fire-retardant core material, 11 is a buckle, 12 is silicone rubber, and 13 is a screw.

[0057] In Figures 9 to 11, 1 is a tightening jig, 2 is an inner sleeve, 3 is an outer sleeve, 4 is a diagonal cable body, 101 is a half ring body, 102 is a locking groove, 103 is a silicone rubber pad, 201 is a barrier edge, 202 is a cavity, 203 is a low-melting-point colloid, 204 is a core ring, 205 is a flame-retardant core material, 206 is a fire-resistant tape, 207 is an inner half sleeve, 208 is a first tightening groove, 209 is a first buckle, 210 is an escape port, 301 is a double layer, 302 is a liquid outlet, 303 is a low-melting-point seal, 304 is an end sleeve, 305 is a locking edge, 306 is an outer half sleeve, 307 is a second tightening groove, and 308 is a second buckle.

Claims

1. A flame retardant device for a stay cable that can expand in two directions when exposed to heat, comprising a flame retardant ring and a positioning jig, the flame retardant ring being fixed to the surface of the stay cable main body by the positioning jig, the flame retardant ring covering the stay cable main body, and the flame retardant ring expanding inward when exposed to heat to encase the stay cable main body and expanding outward to insulate the stay cable main body on both sides of the flame retardant ring.

2. The flame retardant ring of claim 1 is a one-piece structure in which the cable main body passes through the flame retardant ring, or the flame retardant ring is a half-type structure in which the cable main body is wrapped around the flame retardant ring.

3. The flame retardant ring is installed on the outer surface of the fire retardant tape, and the flame retardant ring is installed on the outer surface of the fire retardant tape.

4. The flame-retardant ring of claim 1 includes a flame-retardant ring casing, a flame-retardant core material, and a buckle, the flame-retardant core material being installed inside the flame-retardant ring casing, and the buckle being fitted to the outside of the flame-retardant ring casing.

5. The flame-retardant core material has an annular structure, the flame-retardant ring casing has a hollow annular structure, the flame-retardant ring casing includes a flame-retardant ring cylinder, an upper flame-retardant ring cover plate, and a lower flame-retardant ring cover plate, the flame-retardant core material is installed inside the flame-retardant ring cylinder, the upper flame-retardant ring cover plate and the lower flame-retardant ring cover plate are installed at the upper and lower ends of the flame-retardant ring cylinder, respectively, and gaskets are installed at the joints, and the flame-retardant core material is fixed inside the flame-retardant ring cylinder.

6. The flame-retardant ring casing is made of high-density polyethylene material, and its thickness is not less than 3 mm. The inner diameter of the flame-retardant ring casing is 1 to 3 mm larger than the outer diameter of the stay cable body. The inner diameter D1, outer diameter D2 and height H of the flame retardant core material are set as shown in the table below. Table 1 The flame retardant for stay cables capable of achieving two-way expansion when subjected to heat according to claim 4, characterized in that:

7. The flame retardant cable fire prevention device capable of achieving two-way expansion when exposed to heat as described in claim 1, characterized in that a positioning groove is machined on the surface of the flame retardant ring casing, the positioning groove is used to install the buckle, and the buckle fixes the half-structured flame retardant ring casing together.

8. The flame retardant device for a stay cable that can achieve two-way expansion when exposed to heat, as described in claim 1, is characterized in that the positioning jig is installed at the lower end of the flame retardant ring, the bottom of the flame retardant ring is supported on the positioning jig, the positioning jig has a half structure and wraps around the outside of the stay cable body, and a silicone rubber with a thickness of 5 mm to 10 mm is installed in the inner hole of the positioning jig, and the silicone rubber wraps around the outside of the stay cable body.

9. The flame retardant cable device capable of achieving two-way expansion when exposed to heat, as described in claim 8, is characterized in that a connection hole is provided on the surface of the positioning jig, and a connection member is installed in the connection hole to connect the positioning jig to the flame retardant ring, or a position limiting member is installed in the connection hole to form an outer position limit for the flame retardant ring.

10. 10. The heat-responsive bidirectionally expandable flame retardant device for stay cable according to claim 1, wherein the positioning jig is a clamping jig, the flame retardant ring includes an inner sleeve and an outer sleeve, the outer sleeve is provided with a double layer, the double layer is filled with fire extinguishing liquid, the inner sleeve is slidably installed within the outer sleeve, the outer edge of the top end of the inner sleeve and the inner edge of the bottom end of the outer sleeve are both provided with barrier edges, a cavity is formed between the inner sleeve and the outer sleeve, the bottom of the cavity is provided with low-melting-point colloid, the inner sleeve and the outer sleeve are fixed by the low-melting-point colloid, a liquid outlet is provided at the inner lower part of the outer sleeve and communicates with the double layer, the outer end face of the liquid outlet is bonded to the outer wall of the inner sleeve, and a low-melting-point seal is fixed at the inner end of the liquid outlet, a core ring with a C-shaped cross section is fixed at the bottom of the inner sleeve, a flame retardant core is installed within the core ring, and the flame retardant core is fixed within the core ring with fire retardant tape.

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