Small local open flame test device and method for fire resistance testing of cable protective materials

Abstract

This invention discloses a small-scale localized open flame test device and method for testing the fire resistance of cable protective materials. The device comprises a test furnace system, a cable model, and a temperature monitoring system. The test furnace system includes a test furnace, a fan subsystem, and a gas subsystem. The cable models include a steel drum cable model and a cable strand assembly cable model. The temperature monitoring system, a computer, and a controller work together to achieve real-time monitoring and control of the furnace temperature. This device can simulate the localized high-temperature exposure environment of bridge cables in real-world fire scenarios, allowing for rapid testing of the fire resistance of cable model protective materials. It features convenient operation, ease of movement, precise temperature control, compact size, and low gas consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of local real fire testing of cables, and in particular to a small-scale local open fire testing device and method for fire resistance testing of cable protective materials. Background Art

[0002] As urban spatial patterns continue to intensify, the rapidly increasing volume of traffic has increased the risk of vehicle fire accidents on long-span bridges, posing a serious challenge to the safe operation of bridges. Cables composed of high-strength steel wires are the main load-bearing components of cable-supported bridges such as long-span suspension bridges and cable-stayed bridges. Due to the high thermal conductivity and low specific heat capacity of steel, it has weak fire resistance. Bridge fire accidents usually occur on the upper part of the bridge deck. As the flames spread upward, the cables heat up rapidly in the high temperature environment, and their load-bearing capacity will rapidly decrease, seriously threatening the safety performance of the entire bridge. However, cable fire damage is difficult and expensive to repair. Therefore, they need to be properly protected from fire and the appropriate fireproof materials and structures must be selected.

[0003] Currently, numerical simulation is the primary approach for studying the fire resistance of cables and designing fire protection, but this approach lacks relevant experimental verification. Cable fire resistance testing is still in its developmental stages. Closed-space fire tests employ a uniform temperature field, making it difficult to replicate the non-uniform high-temperature exposure of bridge cables in real-world fire scenarios. Furthermore, these tests consume significant gas and are expensive. Furthermore, precise temperature control technology is not yet available for open-space flame testing. Summary of the Invention

[0004] In response to the above-mentioned technical deficiencies, the purpose of the present invention is to provide a small-scale local open flame test device and method for fire resistance testing of cable protective materials, which can carry out fast and convenient fire resistance tests on cable models with different fireproof materials attached, and conduct fire protection design and optimization. It has the characteristics of easy operation, easy mobility, real-time and precise temperature control, compact size, high space utilization, low gas consumption and strong economy.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a small-scale local open flame test device for fire resistance testing of cable protective materials, comprising:

[0007] A test furnace system, comprising a test furnace, a fan subsystem, and a gas subsystem. The test furnace is a cubic structure with one side open and the other sides closed, with the opening aligned with a steel cylinder-type or strand-assembled cable model.

[0008] The model support is arranged outside the test furnace opening to fix the cable model. The distance between the model support and the test furnace is reserved according to the temperature field of the fire area on the fire-facing surface of the cable model and the target temperature field;

[0009] A flame-spraying burner, which is distributed in a rectangular array inside the test furnace; a gas subsystem and a fan subsystem respectively supply gas and air to the flame-spraying burner, so that the two are mixed in a non-premixed combustion form to form a flame.

[0010] A temperature monitoring system, including an armored thermocouple arranged above the flame-spraying burner and thermocouples arranged at each measuring point of the cable model. The armored thermocouple and the thermocouples are respectively connected to a temperature data acquisition instrument; the gas subsystem and the fan subsystem can, according to the data obtained by the temperature data acquisition instrument, realize dynamic control of the furnace temperature by adjusting the gas supply amount and the air supply frequency.

[0011] Preferably, when the cable model is of the strand-assembled type, the cable model includes:

[0012] A cable test model, the cross-sectional diameter of which is reduced in proportion according to the full-scale cable. The cable test model is composed of multiple strands of parallel, same-length and end-aligned strands locked and fixed by a number of annular steel hoops. The reduction ratio of the strands is the same as that of the cable test model, and the strands are formed by squeezing multiple strands of fine steel wires into a round shape and the fine steel wires are staggeredly tied and fixed at both ends and the middle position thereof by steel straps to reduce the porosity of the cable test model and make it close to the porosity of the real cable.

[0013] Thermocouples, which are welded on the surface of the measuring points of several strands inside the cable test model and led out through the gaps between the strands. Steel gaskets are installed on the surface of the thermocouples exposed outside the cable test model to isolate the flame; the strands welded with thermocouples are arranged and positioned in sequence in the cable test model according to the target measuring point positions.

[0014] Steel wires, which are wound on the surface of the cable test model to prevent the flame from directly contacting the cable test model.

[0015] Preferably, when the cable model is of the steel cylinder type, temperature measuring points are arranged on the outer surface of the fireproof material on the fire-facing side of the cable model, the outer wall of the steel cylinder and the inner wall of the steel cylinder. Steel gaskets are installed on the surface of the thermocouples at the measuring points on the outer surface of the fireproof material of the cable model to reduce the damage to the thermocouples caused by direct fire and avoid the influence of heat convection on the measurement accuracy.

[0016] Preferably, the flame-spraying burners are arranged in a "field" shape perpendicular to the ground, and their flame-spraying ports face the opening direction of the test furnace. Each flame-spraying burner includes an "L"-shaped flame detector. When the flame detector detects a flame, gas is normally sprayed. When the flame detector does not detect a flame, the gas supply is closed within a set time.

[0017] Preferably, the fan subsystem includes a centrifugal induced draft fan, which is connected to an air supply main duct. The air supply main duct branches into four air supply branch ducts, which respectively correspond to the burner ducts of the four groups of flame burners.

[0018] Preferably, the gas subsystem includes a gas main pipeline provided with a pressure reducing valve. The gas main pipeline is connected to the gas cylinder and branches out into four gas branch pipelines, which are respectively connected to the corresponding four burner pipelines. A gas control valve is also provided on the gas main pipeline.

[0019] In a second aspect, the present invention further proposes a test method for a small-scale local open flame test device based on the fire resistance test of the cable protective material, comprising the following steps:

[0020] Step 1: Make a cable model and arrange thermocouples at each temperature measuring point of the cable model;

[0021] Step 2: Determine the distance between the cable model and the test furnace, place the model support at the designated position, and move the cable model into the model support, ensuring that the fire-facing surface of the cable model is parallel and aligned with the opening surface of the test furnace;

[0022] Step 3: Connect the thermocouple of the cable model and the armored thermocouple in the test furnace to the temperature data acquisition instrument respectively, connect the centrifugal induced draft fan and the gas control valve to the corresponding controller, and connect the temperature data acquisition instrument and the controller to the computer respectively;

[0023] Step 4: According to the set target temperature rise curve, the centrifugal induced draft fan air supply frequency and the valve opening of the gas control valve are pre-set through the controller, and the flame is ignited;

[0024] Step 5: At regular intervals, the temperature monitoring system acquires the temperature of each measuring point and transmits the data to the computer. The data is compared with the target temperature rise curve, and the controller adjusts the air supply frequency of the centrifugal induced draft fan and the valve opening of the gas control valve in real time to achieve real-time monitoring and control of the furnace temperature.

[0025] Step 6: When the predetermined temperature or fire exposure time is reached, the test is stopped and the fire resistance performance of the protective material is analyzed based on the temperature rise curve of each measuring point of the cable model;

[0026] Step seven: Replace the cable model with different fireproof materials, conduct multiple tests and analyses, and finally select the optimal cable protection material.

[0027] The beneficial effects of the present invention are:

[0028] 1. The test environment is more realistic: In current cable fire resistance tests, closed space fire resistance tests are difficult to replicate the non-uniform high-temperature exposure environment of bridge cables in real fire scenarios. The small-scale local open flame test device of the present invention, through a test furnace system, aligns the opening with the cable model, which can better simulate the actual fire conditions of the cable in a bridge fire accident, making the test results more valuable for reference.

[0029] 2. Real-time and precise temperature control: Existing open space open flame tests have not yet achieved precise temperature control technology. The present invention uses a temperature monitoring system, armored thermocouples and thermocouples arranged at various measuring points of the cable model to monitor the temperature changes of each measuring point of the cable model in real time during the test; at the same time, after obtaining the required gas supply and air supply frequency according to the set target temperature rise curve, the gas and air supply are controlled to achieve real-time dynamic regulation of the furnace temperature throughout the test process, ensuring that the test is carried out under precise temperature conditions.

[0030] 3. Easy operation: The air supply frequency of the centrifugal induced draft fan and the valve opening of the gas control valve are set in advance through the controller and the flame is ignited. Subsequently, the test can be completed by adjusting the relevant parameters in real time according to the monitored temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A schematic structural diagram of a small-scale local open flame test device for fire resistance testing of cable protective materials provided by an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the structure of the fan subsystem and the gas subsystem provided in an embodiment of the present invention;

[0034] Figure 3 A schematic structural diagram of four groups of flame burners provided in an embodiment of the present invention;

[0035] Figure 4 The cable model provided in the embodiment of the present invention is a structural schematic diagram of a steel cylinder cable model;

[0036] Figure 5 A schematic structural diagram of a cable test model provided in an embodiment of the present invention;

[0037] Figure 6 A schematic cross-sectional view of a cable test model provided in an embodiment of the present invention.

[0038] Explanation of the reference numerals in the drawings:

[0039] 1 - Test furnace; 2 - Cable model; 3 - Model support; 4 - Controller; 5 - Computer; 6 - Temperature data acquisition instrument; 7 - Centrifugal induced draft fan; 8 - Main air supply duct; 9 - Branch air supply duct; 10 - Duct support; 11 - Main gas pipeline; 12 - Branch gas pipeline; 13 - Gas control valve; 14 - Pressure reducing valve; 15 - Gas cylinder; 16 - Burner pipeline; 17 - Armored thermocouple; 18 - Spraying burner; 19 - Flame detector; 20 - Cable test model; 21 - Ring-shaped steel hoop; 22 - Steel wire; 23 - Cable strand. Specific implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0041] As Figures 1 to 6 shown, this embodiment provides a small-scale local open fire test device for the fire resistance test of cable protection materials, which specifically includes:

[0042] A test furnace system, including a test furnace 1, a fan subsystem and a gas subsystem. The test furnace 1 is a cube structure with one side open and the rest closed, forming a semi-closed space, and its opening is aligned with the cable model 2 in the form of a steel cylinder type or a cable strand assembled type for the test;

[0043] Spraying burners 18, which are distributed in a rectangular array inside the test furnace 1; the gas subsystem is connected to the spraying burners 18 and supplies gas for them, and the fan subsystem is connected to the spraying burners 18 and conveys air for them. Gas and air are mixed in the form of non-premixed combustion to form a flame; the gas subsystem and the fan subsystem can achieve dynamic control of the furnace temperature by adjusting the gas supply amount and the air supply frequency;

[0044] The spraying burners 18 are arranged in a "field" shape perpendicular to the ground, and their spraying ports are placed on the inner wall of the test furnace 1, facing the opening direction of the test furnace 1. Gas and air are transmitted to the spraying ports of the spraying burners 18 through the burner pipeline 16, and are mixed in the form of non-premixed combustion to form a flame respectively; each spraying burner 18 includes an "L"-shaped flame detector 19. When the flame detector 19 detects a flame, gas is normally sprayed. When the flame detector 19 does not detect a flame, the gas control valve 13 is closed within three seconds to ensure the safety of the test.

[0045] The temperature monitoring system includes an armored thermocouple 17 arranged above the flame burner 18 in the furnace and thermocouples arranged at various measuring points of the cable model 2. The armored thermocouple 17 and thermocouples are respectively connected to the temperature data acquisition instrument 6 outside the test furnace 1 to monitor the furnace temperature and the temperature changes of each measuring point of the cable model 2 in real time during the test;

[0046] The computer 5 is electrically connected to the controller 4 and the temperature data acquisition instrument 6. The temperature data acquisition instrument 6 obtains the temperature of each measuring point in real time and transmits the data to the computer 5. The computer 5 obtains the required gas supply amount and air supply frequency according to the set target temperature rise curve, and adjusts the gas and air supply through the controller 4 to achieve real-time dynamic regulation of the furnace temperature during the entire test process.

[0047] It also includes a model support 3 for fixing the cable model 2, which is arranged outside the opening of the open flame test furnace 1. The distance between the model support 3 and the test furnace 1 is determined according to the temperature field of the fire area on the fire-facing surface of the cable model 2 and the target temperature field.

[0048] In this embodiment, the cable model 2 is a cable strand assembly type, and the cable model 2 includes:

[0049] The cable test model 20 has a cross-sectional diameter proportionally reduced from that of a full-scale cable. The cable test model 20 is composed of multiple parallel strands 23 of equal length and aligned at both ends, secured by a plurality of annular steel clamps 21. The strands 23 are reduced in scale to that of the cable test model 20. The strands 23 are formed by extruding multiple bundles of fine steel wires into round shapes, and the fine steel wires are staggered and secured at both ends and in the middle with steel ties to reduce the porosity of the cable test model 20 to approximate the porosity of an actual cable.

[0050] Thermocouples are welded to the measuring point surfaces of several strands 23 inside the cable test model 20 and lead out through the gaps between the strands 23. Steel gaskets are installed on the thermocouple surfaces exposed outside the cable test model 20 to isolate the flame. The strands 23 welded with thermocouples are positioned in sequence within the cable test model 20 according to the target measuring point locations.

[0051] The steel wire 22 is wound around the surface of the cable test model 20 to prevent the flame from directly contacting the cable test model 20 .

[0052] The minimum diameter of the cable test model 20 is within the tolerance range of 5%, and its diameter is not less than the result determined by the following formula:

[0053]

[0054] Where R0 is the recommended minimum cross-sectional diameter of the cable test model 20, R is the prototype diameter of the cable test model 20, and e is a natural constant, 80 mm ≤ R ≤ 1500 mm.

[0055] The fan subsystem includes a centrifugal induced draft fan 7 placed on the side of the test furnace 1, and the centrifugal induced draft fan 7 is connected to the main air supply duct 8. The main air supply duct 8 is located at the back of the test furnace 1, placed on a duct bracket 10, and fixed to the test furnace 1 as a whole. The main air supply duct 8 branches into four air supply branch ducts 9, which correspond to the burner ducts 16 of four groups of flame burners 18 respectively.

[0056] The gas subsystem includes a gas main pipeline 11 provided with a pressure reducing valve 14. The gas main pipeline 11 is placed on a pipeline bracket 10. The gas main pipeline 11 is connected to a gas cylinder 15 and branches out into four gas branch pipelines 12, which are respectively connected to the corresponding four burner pipelines 16. A gas control valve 13 is also provided on the gas main pipeline 11 to display the gas opening in real time.

[0057] The present invention also provides a test method of a small-scale local open flame test device for fire resistance testing of cable protective materials, comprising the following steps:

[0058] Step 1: Make a cable model 2 and arrange thermocouples at each temperature measuring point of the cable model 2;

[0059] Step 2: Determine the distance between the cable model 2 and the test furnace 1, place the model support 3 at the designated position, and move the cable model 2 into the model support 3, ensuring that the fire-facing surface of the cable model 2 is parallel and aligned with the opening surface of the test furnace 1;

[0060] Step 3: Connect the thermocouple of the cable model 2 and the armored thermocouple 17 in the test furnace 1 to the temperature data acquisition instrument 6, and connect the centrifugal induced draft fan 7 and the gas control valve 13 to the adapted controller 4; and connect the temperature data acquisition instrument 6 and the controller 4 to the computer 5 respectively;

[0061] Step 4: According to the set target temperature rise curve, the air supply frequency of the centrifugal induced draft fan 7 and the valve opening of the gas control valve 13 are pre-set by the controller 4, and the flame is ignited;

[0062] Step 5: At regular intervals, the temperature monitoring system acquires the temperature of each measuring point and transmits the data to the computer 5. The computer 5 compares the data with the target temperature rise curve and adjusts the air supply frequency of the centrifugal induced draft fan 7 and the valve opening of the gas control valve 13 in real time through the controller 4 to achieve real-time monitoring and control of the furnace temperature.

[0063] Step 6: When the predetermined temperature or fire exposure time is reached, the test is stopped and the fire resistance performance of the protective material is analyzed based on the temperature rise curve of each measuring point of the cable model 2;

[0064] Step seven, replace the cable model 2 with different fireproof materials and fireproof structures, conduct multiple tests and analyses, and finally select the optimal cable protection material.

[0065] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A test method for a small local open flame test device for fire resistance testing of cable protective materials, involving a local real fire test of a cable, characterized in that: The device comprises: A test furnace system comprises a test furnace (1), a fan subsystem and a gas subsystem, wherein the test furnace (1) is a cubic structure with one side open and the other sides closed, and the opening is aligned with a steel cylinder type or a cable strand assembly type cable model (2); A model support (3) is arranged outside the opening of the test furnace (1) and is used to fix the cable model (2); The flame burners (18) are arranged in a rectangular array inside the test furnace (1); the gas subsystem and the fan subsystem respectively provide the flame burners (18) with gas and air so that the gas and air are mixed in a non-premixed combustion form to form a flame; The temperature monitoring system includes an armored thermocouple (17) arranged above the flame burner (18) and thermocouples arranged at each measuring point of the cable model (2), wherein the armored thermocouple (17) and the thermocouple are respectively connected to a temperature data acquisition instrument (6); the gas subsystem and the fan subsystem can realize dynamic control of the furnace temperature by adjusting the gas supply amount and the air supply frequency according to the data obtained by the temperature data acquisition instrument (6); When the cable model (2) is a cable strand assembly type, it comprises: A cable test model (20) has a cross-sectional diameter that is proportionally reduced based on a full-scale cable and can reach a maximum of 1500 mm. The cable test model (20) is composed of a plurality of strands (23) that are parallel to each other, of the same length, and aligned at both ends, which are locked and fixed by a plurality of annular steel clamps (21). The reduction ratio of the strands (23) is consistent with the reduction ratio of the cable test model (20), and the strands (23) are formed by extruding a plurality of bundles of thin steel wires and the thin steel wires are staggered and fixed at both ends and the middle position by steel ties to reduce the porosity of the cable test model (20) and make it close to the porosity of the real cable. Thermocouples are welded to the measuring point surfaces of a plurality of strands (23) inside the cable test model (20) and are led out through the gaps between the strands (23). Steel gaskets are installed on the thermocouple surfaces exposed outside the cable test model (20) to isolate the flame. The strands (23) welded with thermocouples are positioned in sequence within the cable test model (20) according to the target measuring point positions. A steel wire (22) is wound around the surface of the cable test model (20) to prevent the flame from directly contacting the cable test model (20); When the cable model (2) is a steel cylinder type, its temperature measuring points are arranged on the outer surface of the fireproof material of the cable model (2) facing the fire, the outer wall of the steel cylinder and the inner wall of the steel cylinder. Steel gaskets are installed on the surface of the thermocouples at the measuring points on the outer surface of the fireproof material of the cable model (2) to reduce the damage to the thermocouples caused by direct fire and to prevent heat convection from affecting the measurement accuracy. The test method comprises the following steps: Step 1: making a cable model (2), and arranging thermocouples at each temperature measuring point of the cable model (2); Step 2: reserve a distance between the model support (3) and the test furnace (1) according to the temperature field of the fire-facing area of ​​the cable model (2) and the target temperature field, place the model support (3) at a designated position, move the cable model (2) into the model support (3), and ensure that the fire-facing surface of the cable model (2) is parallel and aligned with the opening surface of the test furnace (1); Step 3: Connect the thermocouples of the cable model (2) and the armored thermocouples (17) in the test furnace (1) to the temperature data acquisition instrument (6) respectively. Connect the fan subsystem and the gas subsystem to the appropriate controller (4). Connect the temperature data acquisition instrument (6) and the controller (4) to the computer (5) respectively. Use the armored thermocouples (17) and the thermocouples arranged at each measuring point of the cable model (2) to monitor the temperature changes of the furnace temperature and each measuring point of the cable model (2) during the test in real time. Step 4: According to the set target heating curve, pre-set the air supply frequency of the fan subsystem and the valve opening of the gas subsystem through the controller (4), and ignite the flame. Step 5: At regular intervals, the temperature monitoring system obtains the temperatures of each measuring point and transmits the data to the computer (5). Compare the data with the target heating curve. After obtaining the required gas supply and air supply frequency to be adjusted according to the set target temperature rise curve, adjust the air supply frequency of the fan subsystem and the valve opening of the gas subsystem in real time through the controller (4) to achieve real-time dynamic monitoring and control of the furnace temperature during the whole test process, ensuring that the test is carried out under precise temperature conditions. Replicate the non-uniform high-temperature exposure environment of the bridge cable under the real fire scene, and better simulate the actual fire situation of the cable in the bridge fire accident. Step 6: When the predetermined temperature or the fire exposure time is reached, stop the test, and analyze the fire resistance performance of the protective material based on the temperature rise curves of each measuring point of the cable model (2). Step 7: Replace the cable model (2) with different fireproof materials, conduct multiple test analyses, and finally select the optimal cable protective material.

2. The test method of the small-scale local open flame test device for fire resistance test of cable protective materials according to claim 1, characterized in that: The flame burners (18) are arranged in a "field" shape perpendicular to the ground, and their flame outlets face the opening direction of the test furnace (1). Each flame burner (18) includes an "L"-shaped flame detector (19). When the flame detector (19) detects a flame, the gas is normally ejected. When the flame detector (19) does not detect a flame, the gas supply is closed within the set time.

3. The test method of the small-scale local open flame test device for fire resistance test of cable protective materials according to claim 1, characterized in that: The fan subsystem includes a centrifugal induced draft fan (7). The centrifugal induced draft fan (7) is connected to the main air supply duct (8). The main air supply duct (8) branches out four air supply sub-ducts (9), which respectively correspond to the burner ducts (16) of the four groups of flame burners (18).

4. The test method of the small-scale local open flame test device for fire resistance test of cable protective materials according to claim 3, characterized in that: The gas subsystem includes a gas main pipe (11) provided with a pressure reducing valve (14). The gas main pipe (11) is connected to the gas cylinder (15) and branches out four gas sub-ducts (12), which are respectively connected to the corresponding four burner ducts (16). A gas control valve (13) is also provided on the gas main pipe (11).

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