Small local open fire test device and method for cable protection material fire resistance test

Abstract

The invention discloses a small local open fire test device and method for a cable protection material fire resistance test. The device comprises a test furnace system, a cable model and a temperature monitoring system, the test furnace system comprises a test furnace, a fan subsystem and a gas subsystem; the cable model comprises a steel cylinder type cable model and a cable strand assembly type cable model; real-time monitoring, regulation and control of the temperature in the furnace are achieved through the combined action of the temperature monitoring system, the computer and the controller. The device can simulate a local high-temperature exposure environment of a bridge cable in a real fire scene, rapidly detects the fire resistance of a cable model protection material, and has the characteristics of convenient operation, convenient movement, accurate temperature control, small size, low gas consumption and the like.

Description

Technical Field

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

[0002] With the continuous densification of the urban spatial pattern, the increasing transportation volume has raised the risk of vehicle fire accidents on long-span bridges, posing a severe 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, they have weak fire resistance. Bridge fire accidents usually occur above the bridge deck. Since the flame spreads upward, the cable quickly heats up in a high-temperature environment, and its load-bearing capacity will rapidly decline, seriously threatening the safety performance of the entire bridge. However, it is difficult and expensive to repair the cable after fire damage. Therefore, reasonable fire protection is required, and appropriate fire protection materials and fire protection structures need to be selected.

[0003] Currently, numerical simulation is the main approach for studying the fire resistance performance of cables and designing fire protection, but there is a lack of relevant experimental verification. At present, the experimental research on the fire resistance performance of cables is in the development stage. The fire environment of the fire resistance test in a closed space is a uniform temperature field, which is difficult to reproduce the non-uniform high-temperature exposure environment of bridge cables in a real fire scenario, and it consumes a large amount of gas and is expensive. In terms of open-space open fire tests, precise temperature control technology has not been achieved yet. Summary of the Invention

[0004] Aiming at the above-mentioned technical deficiencies, the purpose of the present invention is to provide a small-scale local open fire test device and method for testing the fire resistance of cable protection materials, which can carry out rapid and convenient fire resistance tests on cable models with different external fire protection materials, conduct fire protection design and optimization, and have the characteristics of convenient operation, easy movement, real-time and precise temperature control, small volume, high space utilization rate, low gas consumption, and strong economy.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

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

[0007] A test furnace system, including a test furnace, a fan subsystem, and a gas subsystem. The test furnace is a cubic structure with one side open and the rest closed, and its opening is aligned with a cable model in the form of a steel cylinder or a strand assembly.

[0008] A model support, arranged outside the opening of the test furnace for fixing the cable model, and reserving the distance between the model support and the test furnace according to the temperature field of the fire-exposed area on the fire-facing surface of the cable model and the target temperature field.

[0009] The flame - spraying burners are distributed in a rectangular array inside the test furnace; the gas sub - system and the fan sub - system respectively supply gas and air to the flame - spraying burners, so that the two are mixed in a non - premixed combustion form to form a flame.

[0010] The temperature monitoring system includes armored thermocouples arranged above the flame - spraying burners and thermocouples arranged at each measuring point of the cable model. The armored thermocouples and the thermocouples are respectively connected to a temperature data acquisition instrument; the gas sub - system and the fan sub - system can, according to the data obtained by the temperature data acquisition instrument, achieve 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, whose cross - sectional diameter is reduced in proportion according to the full - scale cable. The cable test model is composed of multiple bundles of parallel, same - length and end - aligned strands locked and fixed by several 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 bundles of fine wires into a round shape and the fine wires at both ends and the middle position are stagger - tied and fixed 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 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] Wires are wound around 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 fire - proof 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 fire - proof 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 contains 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 the main air supply duct. The main air supply duct branches out into four air supply sub - ducts, corresponding to the burner ducts of four groups of flame - spraying burners respectively.

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

[0019] In a second aspect, the present invention also provides a test method for a small - scale local open - fire test device based on the fire - resistance test of the cable protection material, including the following steps:

[0020] Step 1: Fabricate a cable model and arrange thermocouples at each temperature measurement 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 to ensure 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 thermocouples of the cable model and the armored thermocouples in the test furnace to a temperature data acquisition instrument respectively. Connect the centrifugal induced draft fan and the gas control valve to an adapted controller, and connect the temperature data acquisition instrument and the controller to a computer respectively.

[0023] Step 4: According to the set target heating curve, preset the air supply frequency of the centrifugal induced draft fan and the valve opening of the gas control valve through the controller, and ignite the flame.

[0024] Step 5: At regular intervals, the temperature monitoring system obtains the temperatures of each measurement point and transmits the data to the computer. Compare the data with the target heating curve, and adjust the air supply frequency of the centrifugal induced draft fan and the valve opening of the gas control valve in real - time through the controller to achieve real - time monitoring and control of the furnace temperature.

[0025] Step 6: When the predetermined temperature or the fire - exposure time is reached, stop the test. Based on the temperature rise curves of each measurement point of the cable model, analyze the fire - resistance performance of the protection material.

[0026] Step 7: Replace the cable models with different fire - proof materials, conduct multiple tests and analyses, and finally select the optimal cable protection material.

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

[0028] 1. The test environment is more in line with reality: In the current cable fire resistance tests, it is difficult to reproduce the non-uniform high-temperature exposure environment of bridge cables in a real fire scenario in the enclosed space fire resistance test. However, in the small-scale local open fire test device of the present invention, through the test furnace system, the opening is aligned with the cable model, which can better simulate the actual fire exposure situation of the cable in a bridge fire accident, making the test results more valuable for reference.

[0029] 2. It has real-time and precise temperature control: The existing open space open fire tests have not achieved precise temperature control technology. The present invention, through the temperature monitoring system, uses armored thermocouples and thermocouples arranged at each measuring point of the cable model to monitor the temperature changes at each measuring point of the cable model in real time during the test. At the same time, after obtaining the required adjusted gas supply amount and air supply frequency according to the set target temperature rise curve, the real-time dynamic regulation of the furnace temperature throughout the test is realized by controlling the gas and air supply, ensuring that the test is carried out under precise temperature conditions.

[0030] 3. It is convenient to operate: First, set the air supply frequency of the centrifugal induced draft fan and the valve opening of the gas control valve through the controller and ignite the flame. Subsequently, only by adjusting the relevant parameters in real time according to the monitored temperature, the test can be completed. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention 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 following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic structural diagram of the small-scale local open fire test device for the fire resistance test of cable protection materials provided by the embodiment of the present invention;

[0033] Figure 2 It is a schematic structural diagram of the fan subsystem and the gas subsystem provided by the embodiment of the present invention;

[0034] Figure 3 It is a schematic structural diagram of four groups of flame spraying burners provided by the embodiment of the present invention;

[0035] Figure 4 It is a schematic structural diagram of the cable model being a steel cylinder type cable model provided by the embodiment of the present invention;

[0036] Figure 5 It is a schematic structural diagram of the cable test model provided by the embodiment of the present invention;

[0037] Figure 6 It is a schematic cross-sectional diagram of the cable test model provided by the embodiment of the present invention.

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

[0039] 1 - test furnace; 2 - cable model; 3 - model support; 4 - controller; 5 - computer; 6 - temperature data collector; 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 - flame jet burner; 19 - flame detector; 20 - cable test model; 21 - annular steel hoop; 22 - steel wire; 23 - cable strand. Detailed implementation manners

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without 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 testing the fire resistance of cable protection materials, specifically including:

[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 a cable model 2 in the form of a steel cylinder type or a cable strand assembly type for testing;

[0043] Flame jet burners 18 are distributed in a rectangular array inside the test furnace 1; the gas subsystem is connected to the flame jet burners 18 and supplies gas thereto, and the fan subsystem is connected to the flame jet burners 18 and supplies air thereto. The gas and air are mixed in a non-premixed combustion form 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 flame jet burners 18 are arranged in a "field" shape perpendicular to the ground, and their flame jet ports are placed on the inner wall of the test furnace 1, facing the opening direction of the test furnace 1. The gas and air are transmitted to the flame jet ports of the flame jet burners 18 through the burner pipelines 16 and are mixed in a non-premixed combustion form to form a flame; each flame jet burner 18 includes an "L"-shaped flame detector 19. When the flame detector 19 detects a flame, gas is normally ejected. 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 spraying burner 18 in the furnace and thermocouples arranged at each measuring point of the cable model 2. The armored thermocouple 17 and the thermocouples are respectively connected to a temperature data collector 6 outside the test furnace 1 to monitor in real time the temperature changes of the furnace temperature and each measuring point of the cable model 2 during the test process.

[0046] A computer 5 and a controller 4. The computer 5 is electrically connected to the temperature data collector 6. The temperature data collector 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 adjusted gas supply amount and air supply frequency according to the set target temperature rise curve, and adjusts and controls the gas and air supply through the controller 4 to realize the real-time dynamic control of the furnace temperature throughout the 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 fire 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-exposed 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 of the strand assembly type, and the cable model 2 includes:

[0049] A cable test model 20, the cross-sectional diameter of which is reduced in proportion according to the full-scale cable. The cable test model 20 is composed of a plurality of strands 23 that are parallel to each other, have the same length and are aligned at both ends, and are locked and fixed by a number of annular steel hoops 21. The reduction ratio of the strands 23 is the same as that of the cable test model 20, and the strands 23 are formed by squeezing a plurality of fine wires into a round shape and the fine 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 20 and make it close to the porosity of the real cable;

[0050] Thermocouples are welded to the surface of the measuring points of a number 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 surface of the thermocouples exposed outside the cable test model 20 to isolate the flame; the strands 23 welded with thermocouples are arranged and positioned in sequence in the cable test model 20 according to the target measuring point positions.

[0051] Steel wires 22 are 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 value of the diameter of the cable test model 20 is within the allowable error range of 5%, and its diameter is not less than the result determined by the following formula;

[0053]

[0054] In the formula, R 0For the cable test model 20, the recommended minimum cross-sectional diameter is given, where R is the prototype diameter of the cable test model 20, e is the natural constant, and 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. The centrifugal induced draft fan 7 is connected to the main air supply pipe 8. The main air supply pipe 8 is located at the back of the test furnace 1, placed on the pipe support 10, and fixed to the test furnace 1 as a whole. The main air supply pipe 8 branches out into four air supply branch pipes 9, corresponding to the burner pipes 16 of the four groups of flame spraying burners 18 respectively.

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

[0057] The present invention also provides a test method for the small-scale local open fire test device for the fire resistance test of the cable protection material, including the following steps:

[0058] Step 1, fabricate the cable model 2 and arrange thermocouples at each temperature measurement 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 to ensure 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 thermocouples of the cable model 2, 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; connect the temperature data acquisition instrument 6 and the controller 4 to the computer 5 respectively.

[0061] Step 4, according to the set target heating curve, pre-set the air supply frequency of the centrifugal induced draft fan 7 and the valve opening degree of the gas control valve 13 through the controller 4, and ignite the flame.

[0062] Step 5, at regular intervals, the temperature monitoring system obtains the temperatures of each measurement point and transmits the data to the computer 5. The computer 5 compares the data with the target heating curve, and adjusts the air supply frequency of the centrifugal induced draft fan 7 and the valve opening degree 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 the fire exposure time is reached, stop the test, and analyze the fire resistance performance of the protection material based on the temperature rise curves of each measurement point of the cable model 2.

[0064] Step 7: Replace the cable model 2 with different fireproof materials and fireproof structures, conduct multiple experimental analyses, and finally select the optimal cable protection material.

[0065] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A small local open flame test device for fire resistance test of cable protection materials, characterized in that: Including: A test furnace system, including a test furnace (1), a blower subsystem, and a gas subsystem. The test furnace (1) has a cubic structure with one side open and the rest closed, and its opening is aligned with a cable model (2) in the form of a steel cylinder type or a strand assembly type; A model support (3), arranged outside the opening of the test furnace (1) for fixing the cable model (2), and reserving the distance between the model support (3) and the test furnace (1) according to the temperature field of the fire-exposed area on the fire-facing surface of the cable model (2) and the target temperature field; Spherical combustion burners (18), distributed in a rectangular array inside the test furnace (1); the gas subsystem and the blower subsystem respectively supply gas and air to the spherical combustion burners (18) so that the two are mixed in the form of non-premixed combustion to form a flame; A temperature monitoring system, including armored thermocouples (17) arranged above the spherical combustion burners (18) and thermocouples arranged at each measuring point of the cable model (2). The armored thermocouples (17) and the thermocouples are respectively connected to a temperature data acquisition instrument (6); the gas subsystem and the blower subsystem can, according to the data obtained by the temperature data acquisition instrument (6), achieve dynamic control of the furnace temperature by adjusting the gas supply amount and the air supply frequency.

2. The small-scale local open flame test device for fire resistance test of cable protective materials according to claim 1, characterized in that: When the cable model (2) is of the strand assembly type, the cable model (2) includes: A cable test model (20), the cross-sectional diameter of which is reduced in proportion according to the full-scale cable. The cable test model (20) is composed of multiple strands of parallel, same-length and end-aligned strands (23) locked and fixed by a number of annular steel hoops (21). The reduction ratio of the strands (23) is the same as that of the cable test model (20), and the strands (23) are formed by squeezing multiple bundles of fine wires into a round shape and the fine wires are stagger-bundled and fixed at both ends and the middle position thereof 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, welded on the surface of the measuring points of several strands (23) inside the cable test model (20) and led out through the gaps between the strands (23). Steel gaskets are installed on the surface of the thermocouples exposed outside the cable test model (20) to isolate the flame; the strands (23) welded with thermocouples are arranged and positioned in sequence in the cable test model (20) according to the target measuring point positions; Wires (22), wound around the surface of the cable test model (20) to prevent the flame from directly contacting the cable test model (20).

3. The small-scale local open flame test device for fire resistance test of cable protective materials according to claim 1, characterized in that: When the cable model (2) is of the steel cylinder type, temperature measuring points are arranged on the outer surface of the fireproof material on the fire-facing surface of the cable model (2), 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 avoid the influence of heat convection on the measurement accuracy.

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

5. 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 comprises a centrifugal induced draft fan (7), the centrifugal induced draft fan (7) is connected to an air supply main pipeline (8), and the air supply main pipeline (8) branches into four air supply branch pipelines (9), which respectively correspond to the burner pipelines (16) of four groups of flame-spraying burners (18).

6. The small-scale local open flame test device for fire resistance test of cable protective materials according to claim 5, characterized in that: The gas subsystem comprises a gas main pipeline (11) provided with a pressure reducing valve (14); the gas main pipeline (11) is connected to a gas bottle (15) and branches out into four gas branch pipelines (12) which are respectively connected to four corresponding burner pipelines (16); and a gas control valve (13) is also provided on the gas main pipeline (11).

7. The test method of the small local open flame test device for fire resistance test of cable protective materials according to claim 6, characterized in that: The following steps are involved: Step 1, making a cable model (2), and arranging thermocouples at each temperature measuring point of the cable model (2); Step 2: determine the distance between the cable model (2) and the test furnace (1), place the model support (3) at a specified 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, connecting the thermocouple of the cable model (2) and the armored thermocouple (17) in the test furnace (1) to the temperature data acquisition instrument (6), connecting the centrifugal induced draft fan (7) and the gas control valve (13) to the adapted controller (4), and connecting the temperature data acquisition instrument (6) and the controller (4) to the computer (5); 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 set in advance through the controller (4), and the flame is ignited; Step 5: At regular intervals, the temperature monitoring system acquires the temperature of each measuring point and transmits the data to a computer (5), compares the data with a 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 a controller (4), thereby achieving real-time monitoring and control of the furnace temperature; 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); Step seven, replace the cable model (2) with different fireproof materials, conduct multiple tests and analyses, and finally select the optimal cable protection material.

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