A flame-resistant cable and a preparation method thereof

Abstract

The present invention provides a fire-resistant cable and a preparation method thereof, relating to the technical field of cables. The cable includes an inner layer, and an intermediate layer is arranged outside the inner layer, including a plurality of fire-blocking rings arranged on the inner layer. Communication lines are connected to the plurality of fire-blocking rings, and fusing wires are arranged on the fire-blocking rings. A fire-blocking layer is filled in the cylindrical area between adjacent fire-blocking rings. An outer layer is arranged outside the intermediate layer. The fusing wires are arranged in a U shape and the turning part passes through the fire-blocking rings on the side. A communication module and a detection circuit for detecting whether the fusing wires are fused are arranged in the fire-blocking rings. The communication lines are electrically connected to a fire alarm system. The fire-blocking layer includes a heat-insulating filler, and a plurality of fire-blocking capsules are arranged in the heat-insulating filler. The preparation method includes: preparing the inner layer, clamping the fire-blocking rings, and then successively preparing the intermediate layer and the outer layer. When a fire breaks out in the cable, the present invention automatically triggers the alarm of the fire alarm system, and the fire-fighting personnel can quickly find the location of the fire so as to quickly put out the fire and avoid serious consequences caused by the spread of the fire.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and particularly to a fire-resistant cable and a preparation method thereof. Background Art

[0002] A cable is made of one or more mutually insulated conductors and an outer insulating protective layer, and is a wire for transmitting electricity or information from one place to another.

[0003] At present, for ordinary cables, their fire resistance is poor and they are prone to burning when encountering fire. For some fire-resistant cables, although their fire resistance performance is increased, once the cable catches fire, the fire is still prone to spread. Most importantly, cable fires often cannot be detected in the first place, especially when cables often run through some enclosed spaces or corners. Generally, it is not until the cable is burned out and there is an abnormality in power or communication that an inspection will be carried out. At this time, the time interval from the occurrence of the fire is relatively long, and serious consequences often occur. Summary of the Invention

[0004] The purpose of the present invention is to develop a fire-resistant cable and a preparation method thereof, which can automatically trigger an alarm of a fire alarm system when a fire occurs in the cable, so that the fire-fighting personnel can quickly find the location of the fire for rapid fire-fighting and avoid serious consequences caused by the spread of the fire.

[0005] The present invention is achieved through the following technical solutions:

[0006] A fire-resistant cable, comprising:

[0007] An inner layer, in which conductors are arranged;

[0008] A middle layer, provided on the outside of the inner layer, comprising:

[0009] A plurality of fire-blocking rings, arranged on the inner layer;

[0010] A communication line, connected to the plurality of fire-blocking rings;

[0011] A fusing wire, provided on the fire-blocking ring;

[0012] A fire-blocking layer, filled in the cylindrical area between adjacent fire-blocking rings;

[0013] An outer layer, provided on the outside of the middle layer;

[0014] Wherein, the fusing wire is arranged in a U shape and the turning part passes through the fire-blocking ring on the side. A communication module and a detection circuit for detecting whether the fusing wire is fused are provided in the fire-blocking ring. The communication module is electrically connected to the detection circuit and the communication line. The fusing wire is electrically connected to the detection circuit. The communication line is electrically connected to the fire alarm system;

[0015] The fire-blocking layer includes a heat-insulating filler, and a plurality of fire-blocking capsules are provided in the heat-insulating filler.

[0016] Optionally, the firestop ring is in a circular shape and coaxially arranged with the cable. A plurality of the firestop rings are arranged at equal intervals in the length direction of the cable. The inner edge and the outer edge of the firestop ring are both covered with a plurality of sawteeth.

[0017] Optionally, a rigid protective shell connected to the firestop ring is sleeved outside the communication line, and the communication line is arranged close to the fusing wire.

[0018] Optionally, the heat insulation filler includes a mixed granular filler and a powdery filler, and the powdery filler is filled in the gaps of the granular filler;

[0019] The granular filler is expanded perlite or ceramic microspheres, and the powdery filler is quartz sand or alumina powder.

[0020] Optionally, the firestop capsule includes any one or more of a first capsule, a second capsule, and a third capsule. The first capsule, the second capsule, and the third capsule all include a sealing layer on the outside. The sealing layer is a low-melting-point polymer. The sealing layer of the first capsule is filled with sodium silicate and a foaming agent. The sealing layer of the second capsule is filled with water or perfluoromethyl hexanone. The sealing layer of the third capsule is filled with sodium bicarbonate and an acidic trigger agent.

[0021] Optionally, the outer layer includes an outer sheath, which is the outermost layer of the cable. A heat conduction layer is arranged inside the outer sheath, a steel strip is arranged inside the heat conduction layer, and a wrapping layer is arranged inside the steel strip.

[0022] Optionally, the outer sheath is a low-smoke and halogen-free polyolefin, the heat conduction layer is an aluminum alloy mesh, silicon carbide nanowires are adhered to the aluminum alloy mesh, and the wrapping layer is a thermoplastic polyurethane.

[0023] A preparation method of a flame-resistant cable includes the following steps:

[0024] S1. Preparation of the inner layer of the cable;

[0025] S2. Sequentially snap a plurality of firestop rings on the periphery of the inner layer of the cable;

[0026] S3. The cable passes through a feeding cylinder, and while the cable is axially conveyed in the feeding cylinder, it keeps rotating at a constant speed;

[0027] S4. The feeding cylinder fills heat insulation filler and firestop capsules between the firestop rings to form an intermediate layer;

[0028] S5. Inject a thermoplastic outer layer onto the intermediate layer, and cure the outer layer by cooling;

[0029] Among them, the injection barrel includes a first pipe section, a second pipe section, and a third pipe section that are coaxially connected. The first pipe section is filled with heat-insulating filler and fire-resistant capsules. The second pipe section is filled with an outer layer. The third pipe section cools the outer layer.

[0030] Optionally, a plurality of first injection ports are equidistantly arranged at the top of the first pipe section;

[0031] The interior of the second pipe section includes an extrusion section and a shaping section. The cross-section of the extrusion section is arched. The extrusion section is connected to the first pipe section. The extrusion section first flares, then straightens, and finally constricts. A second injection port is provided above the flared portion of the extrusion section. The shaping section is cylindrical;

[0032] The interior of the third pipe section is frustum-shaped, and its inner diameter gradually increases in the direction away from the second pipe section. A liquid injection pipe is provided near the second pipe section at the top of the third pipe section, and a coolant is injected through the liquid injection pipe.

[0033] Optionally, in step S2, the inner diameter of the inner edge of the fire-resistant ring is smaller than the outer diameter of the inner layer. There is a notch on the fire-resistant ring. The fire-resistant ring at the notch is a thermoplastic polymer. The fire-resistant ring is arc-shaped before surrounding the outer part of the inner layer. When the fire-resistant ring is clamped on the outer layer, the inner layer of the cable is located inside the fire-resistant ring. Use an electric heating device to heat the notch, and then surround the fire-resistant ring on the inner layer of the cable. The serrations on the inner edge of the fire-resistant ring are embedded in the surface of the inner layer. The two sides of the notch of the fire-resistant ring are in close contact to achieve surrounding, and then the hot joint of the notch is quickly cooled and solidified, so that the fire-resistant ring is clamped on the inner layer.

[0034] The beneficial effects of the present invention are:

[0035] When the local temperature of the cable rises abnormally, the provided heat-conducting layer can conduct the heat to both sides as much as possible, so that the heat dissipates, avoiding the occurrence of a fire in the cable or prolonging the time required for the cable to burn;

[0036] Due to an external fire source, when the cable inevitably catches fire, the fusing wire is heated and melted, triggering the alarm of the fire alarm system. According to the position of the communication module configured with the fusing wire, the fire-fighting personnel can quickly find the location of the fire, so as to quickly fight the fire and avoid the serious consequences caused by the spread of the fire. Moreover, the fire alarm system can be configured with a plurality of sprinkler heads corresponding to the positions of the communication modules. When the alarm of the fire alarm system is triggered, the fire alarm system controls the corresponding sprinkler heads to directly spray water for fire extinguishing, minimizing the loss to the greatest extent;

[0037] When a fire breaks out, the fireproof layer set can block the spread of the fire to the internal conductor of the cable or directly extinguish the fire. After the fireproof capsule melts and ruptures under high temperature, some fireproof capsules form a foaming structure to isolate oxygen, some of the liquid inside the fireproof capsules soaks into the heat-insulating filler, and some fireproof capsules quickly generate carbon dioxide gas, which soaks into the heat-insulating filler. The gaps in the heat-insulating filler are very small. The liquid that enters the gaps evaporates and absorbs heat to lower the temperature. The carbon dioxide fills the heat-insulating filler to prevent combustion inside the heat-insulating filler, achieving the purpose of delaying or extinguishing the fire. The fireproof ring set can also slow down the spread of the fire in the axial direction of the cable to a certain extent, further reducing the losses caused by the fire. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0039] Figure 1 It is a layered structure diagram of the cable;

[0040] Figure 2 It is a connection structure diagram of the fireproof ring, communication line and fusing wire;

[0041] Figure 3 It is a structure diagram of the injection barrel.

[0042] Reference numerals: 1, inner sheath; 2, fireproof ring; 3, communication line; 4, fusing wire; 5, wrapping layer; 6, steel strip; 7, heat-conducting layer; 8, outer sheath; 9, first pipe section; 10, second pipe section; 11, third pipe section; 12, first injection port; 13, second injection port; 14, liquid injection pipe. Detailed Embodiments

[0043] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0044] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0045] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0046] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] like Figure 1 As shown, the present invention discloses a flame-resistant cable, comprising an inner layer, a middle layer and an outer layer, wherein the conductor is arranged in the inner layer, and the middle layer and the outer layer are both fire-resistant structures.

[0048] The inner layer includes an inner sheath 1, a fire-resistant mica tape is provided on the outside of the inner sheath 1, the conductor is coated with a boron nitride coating, an insulating layer is provided on the outside of the conductor, a conductor shielding layer is provided between the conductor and the insulating layer, an insulating shielding layer is provided on the outside of the insulating layer, and a filler is provided between the insulating shielding layer and the inner sheath 1.

[0049] The middle layer includes multiple firestop rings 2, spaced evenly along the cable's length. These rings are annular and coaxial with the cable, their inner walls connected to the inner sheath 1. Both the inner and outer edges of the firestop rings are covered with serrations, which engage the inner layer at the inner edge and the outer layer at the outer edge, ensuring a stable structure within the cable and preventing displacement.

[0050] The middle layer also includes two communication lines 3 connected to multiple fire-blocking rings 2. The two communication lines 3 are located in the same radial direction of the fire-blocking rings 2 and are symmetrical. The communication lines 3 are sheathed with a protective shell connected to the fire-blocking rings 2. The protective shell is a rigid structure that keeps the multiple fire-blocking rings 2 fixed.

[0051] like Figure 2 As shown, four groups of fusible wires 4 are provided on the fire arrester ring 2, and the two communication lines 3 are arranged close to the fusible wires 4. Even if there is fire or high temperature at the communication line 3, there is a protective shell outside the communication line 3, so that the fusible wires 4 are melted or broken before the communication line 3. A communication module and a detection circuit for detecting whether the fusible wire 4 is melted are provided in the fire arrester ring 2. The communication module is electrically connected to the detection circuit and the communication line 3. The communication module has a built-in unique address or position code, and the communication line 3 is electrically connected to the fire alarm system.

[0052] When a fuse wire 4 fuses or breaks, the communication module electrically connected to the fuse wire 4 transmits an electrical signal through the communication line 3 to the fire alarm system, triggering a fire alarm. According to the address or position code of the communication module, the approximate location of the cable fire can be directly shown, so that the fire-fighting personnel can quickly find the ignition point to fight the fire and avoid the further spread of the fire. When conditions permit at the site, fire extinguishing components such as sprinkler heads can be installed on the side of the cable laying track. The position of the sprinkler head is installed corresponding to the position of the communication module. When the fuse wire 4 on the communication module fuses, the fire alarm system receives the signal and controls the sprinkler head on the side of the communication module to work for fire extinguishing operations, further quickly controlling the fire.

[0053] The fuse wire 4 is arranged in a U shape. The fuse wire 4 includes a first straight segment, a turning segment, and a second straight segment. The first straight segment extends from the fireproof ring 2 and enters the adjacent fireproof ring 2. The turning segment is located within the adjacent fireproof ring 2. The second straight segment extends from the adjacent fireproof ring 2 and then returns to the fireproof ring 2. Both the first straight segment and the second straight segment are arranged parallel to the axial direction of the cable.

[0054] The cylindrical area between adjacent fireproof rings 2 is filled with a fireproof layer. The fireproof layer includes a heat-insulating filler, and several fireproof capsules are provided in the heat-insulating filler.

[0055] The heat-insulating filler includes a mixed granular filler and a powdery filler. The powdery filler is filled in the gaps of the granular filler, making the heat-insulating filler as compact as possible and reducing pores. The granular filler can be expanded perlite or ceramic microspheres, and the powdery filler can be quartz sand or alumina powder.

[0056] The fireproof capsule includes any one or more of the first capsule, the second capsule, and the third capsule. The first capsule, the second capsule, and the third capsule all include an outer sealing layer. The sealing layer is a low-melting-point polymer, which can be polyethylene. The sealing layer melts and ruptures when the cable burns or is at a high temperature.

[0057] The sealing layer of the first capsule is filled with sodium silicate and a foaming agent. The sodium silicate is hydrated sodium silicate, and the foaming agent is sodium bicarbonate or ammonium bicarbonate. When the cable burns or is at a high temperature, the sodium silicate and the foaming agent react to form a foam structure to isolate oxygen.

[0058] The sealing layer of the second capsule is filled with water or perfluoromethyl hexanone, which absorbs heat when the cable burns or is at a high temperature.

[0059] The sealing layer of the third capsule is filled with sodium bicarbonate and an acidic trigger agent. The acidic trigger agent can be any one of citric acid, tartaric acid, sodium bisulfate, and ammonium dihydrogen phosphate. When the cable burns or is at a high temperature, the added acidic trigger agent causes the sodium bicarbonate to react quickly to generate a large amount of carbon dioxide, and the carbon dioxide fills the heat-insulating filler to achieve the purpose of fire extinguishing.

[0060] The outer layer includes an outer sheath 8, which is the outermost layer of the cable. A heat-conducting layer 7 is arranged inside the outer sheath 8, a steel strip 6 is arranged inside the heat-conducting layer 7, and a wrapping layer 5 is arranged inside the steel strip 6. The outer sheath 8 is made of low-smoke and halogen-free polyolefin, the heat-conducting layer 7 is an aluminum alloy mesh, and silicon carbide nanowires are adhered to the aluminum alloy mesh. The wrapping layer 5 is made of thermoplastic polyurethane.

[0061] The present invention also discloses a preparation method of the above-mentioned fire-resistant cable, which includes the following steps:

[0062] S1. Preparation of the inner layer of the cable;

[0063] S2. Sequentially snap a plurality of fire-resistant rings 2 around the periphery of the inner layer of the cable;

[0064] S3. The cable passes through the injection barrel, and while the cable is axially conveyed in the injection barrel, it rotates uniformly around its own axis;

[0065] S4. The injection barrel fills heat-insulating filler and fire-resistant capsules between the fire-resistant rings 2 to form an intermediate layer;

[0066] S5. The injection barrel injects the thermoplastic wrapping layer 5 onto the intermediate layer, and the wrapping layer 5 is cured by cooling;

[0067] S6. Wrap the steel strip 6 on the wrapping layer 5;

[0068] S7. Wind or wrap the heat-conducting layer 7 on the steel strip 6;

[0069] S8. Inject the thermoplastic outer sheath 8 onto the heat-conducting layer 7, and the outer sheath 8 is cured by cooling;

[0070] Among them, the structure of the inner layer of the cable is prior art and will not be elaborated here.

[0071] In step S2, the inner diameter of the inner edge of the fire-resistant ring 2 is smaller than the outer diameter of the inner layer. The fire-resistant ring 2 is provided with a notch. The internal circuit of the fire-resistant ring 2 does not pass through the notch, and the fusing wire 4 and the communication line 3 are at a certain distance from the notch. The fire-resistant ring 2 at the notch is made of thermoplastic polymer. The fire-resistant ring 2 is arc-shaped before surrounding the outside of the inner layer. When the fire-resistant ring 2 is snapped, the inner layer of the cable is located inside the fire-resistant ring 2. Use an electric heating device to heat the notch, and then surround the fire-resistant ring 2 on the inner layer of the cable. The serrations on the inner edge of the fire-resistant ring 2 are embedded into the surface of the inner layer to a certain depth, and the two sides of the notch of the fire-resistant ring 2 are in close contact to achieve surrounding, and then air cooling is carried out to quickly cool and cure the hot joint at the notch, so that the fire-resistant ring 2 is snapped onto the inner layer. During the snapping process of the fire-resistant ring 2, keep the sheath of the communication line 3 straight and parallel to the axis of the cable.

[0072] In steps S3 to S5, the structure of the injection barrel is as Figure 3As shown in the figure, it includes a first pipe section 9, a second pipe section 10, and a third pipe section 11 that are coaxially connected. Heat-insulating filler and fire-resistant capsules are injected into the first pipe section 9, a wrapping layer 5 is injected into the second pipe section 10, and the wrapping layer 5 is cooled in the third pipe section 11.

[0073] The inner diameter of the first pipe section 9 is adapted to the outer diameter of the fire-resistant ring 2. Three first injection ports 12 are provided at the top of the first pipe section 9, and the three first injection ports 12 are arranged at equal intervals on the first pipe section 9. The first injection ports 12 convey heat-insulating filler and fire-resistant capsules between the fire-resistant rings 2 of the cables in the first pipe section 9.

[0074] The interior of the second pipe section 10 includes an extrusion section and a shaping section. The cross-section of the extrusion section is arched. The extrusion section is connected to the first pipe section 9. The extrusion section first flares, then becomes straight, and finally constricts. The cross-section at the flaring part is a circular arc surface and the inner diameter gradually increases. The straight part is cylindrical. The cross-section at the constricting part is a circular arc surface and the inner diameter gradually decreases. The constricting part is connected to the shaping section. The shaping section is cylindrical and its inner diameter is adapted to the outer diameter of the wrapping layer 5. Above the flaring part of the extrusion section, there is a second injection port 13. The material of the extruder is injected through the second injection port 13 to realize the extrusion molding of the wrapping layer 5.

[0075] The interior of the third pipe section 11 is frustum-shaped, and its inner diameter gradually increases in the direction away from the second pipe section 10. A liquid injection pipe 14 is provided at the top of the third pipe section 11 near the second pipe section 10, and the liquid injection pipe 14 injects coolant.

[0076] The above embodiments are only the preferred embodiments of the present invention and do not limit the technical solutions of the present invention. Any technical solutions that can be achieved on the basis of the above embodiments without creative labor shall be regarded as falling within the scope of the patent rights of the present invention.

Claims

1. A flame-resistant cable, characterized in that, Comprising: An inner layer, in which conductors are arranged; An intermediate layer, disposed outside the inner layer, comprising: A plurality of firestop rings, arranged on the inner layer; Communication lines, connected to the plurality of firestop rings; Fuse wires, disposed on the firestop rings; A firestop layer, filled in the cylindrical area between adjacent firestop rings; An outer layer, disposed outside the intermediate layer; Wherein, the fuse wires are arranged in a U shape and the turning part passes through the firestop rings on the side. A communication module and a detection circuit for detecting whether the fuse wires are fused are provided in the firestop rings. The communication module is electrically connected to the detection circuit and the communication lines. The fuse wires are electrically connected to the detection circuit. The communication lines are electrically connected to the fire alarm system; The firestop layer comprises a heat-insulating filler, and a plurality of firestop capsules are provided in the heat-insulating filler; The heat-insulating filler comprises a mixed granular filler and a powdery filler, and the powdery filler is filled in the gaps of the granular filler; The granular filler is expanded perlite or ceramic microspheres, and the powdery filler is quartz sand or alumina powder.

2. The flame-retardant cable according to claim 1, characterized in that, The firestop rings are circular and coaxially arranged with the cable. The plurality of firestop rings are equidistantly arranged in the cable length direction. The inner edge and the outer edge of the firestop rings are both covered with a plurality of sawteeth.

3. The flame-retardant cable according to claim 1, wherein, A rigid protective shell connected to the firestop rings is sleeved outside the communication lines, and the communication lines are arranged close to the fuse wires.

4. The flame-retardant cable according to claim 1, wherein, The firestop capsules include any one or more of a first capsule, a second capsule, and a third capsule. The first capsule, the second capsule, and the third capsule all include a sealing layer on the outside. The sealing layer is a low-melting-point polymer. The sealing layer of the first capsule is filled with sodium silicate and a foaming agent. The sealing layer of the second capsule is filled with water or perfluoromethyl hexanone. The sealing layer of the third capsule is filled with sodium bicarbonate and an acidic trigger agent.

5. The flame-retardant cable according to claim 1, characterized in that, The outer layer comprises an outer sheath, which is the outermost layer of the cable. A heat-conducting layer is provided inside the outer sheath. A steel strip is provided inside the heat-conducting layer. A wrapping layer is provided inside the steel strip.

6. The flame-retardant cable according to claim 5, wherein, The outer sheath is a low-smoke and halogen-free polyolefin. The heat-conducting layer is an aluminum alloy mesh, and silicon carbide nanowires are adhered to the aluminum alloy mesh. The wrapping layer is a thermoplastic polyurethane.

7. A method for preparing a flame-resistant cable according to any one of claims 1 to 6, characterized in that, Including the following steps: S1. Preparation of the cable inner layer; S2. Sequentially snap a plurality of firestop rings around the cable inner layer; S3. The cable passes through a feeding cylinder, and the cable rotates uniformly at a constant speed while being axially conveyed in the feeding cylinder; S4. The feeding cylinder fills the space between the firestop rings with a heat-insulating filler and firestop capsules to form an intermediate layer; S5. The feeding cylinder injects a thermoplastic outer layer onto the intermediate layer, and the outer layer is cured by cooling; Wherein, the feeding cylinder comprises a first pipe section, a second pipe section, and a third pipe section that are coaxially connected. The first pipe section injects a heat-insulating filler and firestop capsules. The second pipe section injects the outer layer. The third pipe section cools the outer layer.

8. The preparation method of the flame-resistant cable according to claim 7, characterized in that, A plurality of first injection ports are equidistantly provided at the top of the first pipe section; The inside of the second pipe section comprises an extrusion section and a shaping section. The cross-section of the extrusion section is arched. The extrusion section is connected to the first pipe section. The extrusion section first expands, then becomes straight, and finally contracts. A second injection port is provided above the expanded part of the extrusion section. The shaping section is cylindrical; The interior of the third pipe section is frustum-shaped, and its inner diameter gradually increases in the direction away from the second pipe section. A liquid injection pipe is provided at the top of the third pipe section near the second pipe section, and the liquid injection pipe injects coolant.

9. The manufacturing method of the flame-retardant cable according to claim 7, characterized in that, In the step S2, the inner diameter of the inner edge of the firestop ring is smaller than the outer diameter of the inner layer. There is a notch on the firestop ring, and the firestop ring at the notch is a thermoplastic polymer. The firestop ring is arc-shaped before surrounding the outer part of the inner layer. When the firestop ring is clamped on the outer layer, the inner layer of the cable is located inside the firestop ring. Use an electric heating device to heat the notch, and then surround the firestop ring on the inner layer of the cable. The serrations on the inner edge of the firestop ring are embedded in the surface of the inner layer. The two sides of the notch of the firestop ring are in close contact to achieve enclosure, and then the heat-sealed part of the notch is quickly cooled and solidified, so that the firestop ring is clamped on the inner layer.

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