Mixed gas flow online calibration device and method for cable combustion test device

Abstract

The invention discloses a mixed gas flow online calibration device and method for a cable combustion test device, and belongs to the technical field of cable and optical cable combustion performance detection. The device comprises a propane gas source, an air source, a pressure reducing valve group, a mass flow controller, a mixed gas online calibration module group, a Venturi mixer and a blowtorch, a mixed gas online calibration module is arranged on the downstream of a mass flow controller, and a temperature and pressure sensor, a differential pressure mass flow meter and an embedded processor are combined, so that real-time monitoring and online calibration of mixed gas flow are achieved; according to the method, a flow drift curve can be fitted, the output error of the controller is corrected, and the influence of dismounting calibration and pipeline leakage is avoided; compared with the prior art, the device has the advantages of being high in precision, simple in structure, capable of self-checking, high in stability and the like, the consistency of the blast burner fire source power and the flame shape in a GB / T 31248 test is effectively improved, and the accuracy and repeatability of a cable combustion performance test are guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant testing of cables and optical fibers, and specifically relates to an online calibration device and testing method for mixed gas flow in a cable combustion test apparatus. Background Technology

[0002] In the field of flame retardant performance testing of cables and optical fibers, the combustion performance test conducted according to the GB / T 31248-2014 standard is a key step in evaluating the flame retardant characteristics of cables. The test requires a fixed blowtorch ignition source with a stable power of 20.5kW to ensure the comparability of the combustion state and results of the cables under standardized flame conditions. The stability of the ignition source directly depends on the mixing ratio of propane and air and the accuracy of the flow rate. Currently, the industry generally uses mass flow controllers to meter and control the mixed gas, but the following technical problems and shortcomings still exist in actual use.

[0003] First, the accuracy of mass flow controllers is difficult to guarantee in the long term. Traditional metrological calibration methods require disassembling the flow controller and sending it for inspection. This method can only calibrate the accuracy of the equipment itself under ideal experimental conditions and fails to reflect the actual usage status of the test device as a whole. It cannot detect problems such as micro-leakage or improper installation in the pipeline. As the usage time increases, the flow controller will drift. However, the experimenters lack effective online self-testing methods, which will cause deviations in the flame power and shape of the blowtorch, affecting the repeatability and accuracy of the test results.

[0004] Secondly, the traditional mass loss method has the problems of complicated operation and large measurement error. Although this method calculates the flow rate by weighing the mass loss of the standard gas cylinder, it can avoid disassembling the flow controller. However, factors such as heat absorption of the standard gas, condensation generation, and temperature fluctuation of the gas cylinder will introduce errors during the weighing process, and real-time monitoring cannot be achieved. As a result, the instantaneous fluctuation of the mixed gas flow rate cannot be reflected, and the flame power and temperature distribution of the blowtorch are difficult to control accurately.

[0005] The aforementioned problems have led to key technical bottlenecks in the field operation of the GB / T 31248-2014 test device, such as low flow control accuracy, unstable torch flame source, and poor repeatability of test results. In response to this situation, there is an urgent need for a device and method that can realize real-time monitoring, automatic calibration, and online correction of the mass flow rate of mixed gas to ensure the long-term stability of the torch flame power and shape. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by proposing an online calibration device and testing method for the mixed gas flow rate of a cable combustion test apparatus. This device and method improve the accuracy of the mixed gas flow rate measurement in the GB / T 31248-2014 test apparatus. By connecting an online calibration module for the mixed gas flow rate in series downstream of the propane and air mass flow controller, and utilizing temperature and pressure sensors, a differential pressure mass flow meter, and an embedded processing unit, flow parameters are collected in real time, and the drift trend is fitted, thereby achieving on-site online calibration and error compensation. This solution avoids the need for disassembly and reassembly calibration of the flow controller, incorporates pipeline leak detection and self-testing functions, and significantly improves the accuracy and stability of flow measurement.

[0007] An online calibration device for mixed gas flow in a cable combustion test apparatus includes a propane gas source, an air gas source, a pressure reducing valve assembly, a ball valve assembly, a propane mass flow controller, an air mass flow controller, a pressure detection assembly, an online calibration module assembly for mixed gas, a mixer, and a blowtorch.

[0008] During the installation and commissioning phase, the torch is used for combustion to avoid the risk of explosion or combustion on site due to emissions; after calibration meets the requirements, it can be used directly for testing.

[0009] The pressure reducing valve assembly includes pressure reducing valve I and pressure reducing valve II; the ball valve assembly includes ball valve I and ball valve II; and the pressure detection assembly includes pressure gauge I and pressure gauge II.

[0010] The online calibration module group for mixed gas includes online calibration module I for mixed gas, online calibration module II for mixed gas, temperature and pressure sensors, differential pressure mass flow meter, embedded processor, and display screen, which are used to collect temperature, pressure and flow data and perform real-time calibration and correction of the flow controller;

[0011] The online calibration module for the mixed gas is located downstream of the propane mass flow controller and the air mass flow controller to perform real-time flow detection and calibration of the mixed gas entering the mixer.

[0012] The propane gas source, pressure reducing valve I, ball valve I, propane mass flow controller, pressure gauge I, and mixed gas online calibration module I are connected in series. The air source, pressure reducing valve II, ball valve II, air mass flow controller, pressure gauge II, and mixed gas online calibration module II are connected in series. The output terminals of mixed gas online calibration module I and mixed gas online calibration module II are connected in parallel to the mixer. The mixer is connected to the blowtorch.

[0013] The technical solution of this application integrates a temperature and pressure sensor, a differential pressure mass flow meter, and an embedded processor by connecting a mixed gas online calibration module in series downstream of a propane and air mass flow controller. This enables real-time acquisition, online calibration, and automatic error compensation of gas flow, pressure, and temperature. It solves the problems of long-term flow controller drift, cumbersome disassembly and calibration, inability to monitor micro-leakage in on-site pipelines, and unstable torch power and flame shape in existing technologies. It also overcomes the shortcomings of traditional standard gas weighing methods, such as complex operation and poor real-time performance. Through a modular structure and parallel mixer design, this invention achieves uniform mixing of the mixed gas, constant torch power output, visualization of the experimental process, and data traceability. This improves the accuracy and stability of the mixed gas flow, simplifies the operation process, and enhances experimental safety and repeatability, thereby comprehensively optimizing the reliability and reproducibility of the GB / T 31248-2014 cable flame retardant test.

[0014] The technical solution provided in this application also has the following technical features:

[0015] Preferably, in one embodiment of this application, the embedded processor is electrically connected to the display screen to display the mass flow rate, temperature, pressure and their change curves of the mixed gas in real time for online monitoring.

[0016] Preferably, in one embodiment of this application, the embedded processor is configured with a least squares-based fitting calculation unit, which calculates the drift amount based on the collected flow data and automatically compensates the outputs of the propane mass flow controller and the air mass flow controller to stabilize the torch output power.

[0017] Preferably, in one embodiment of this application, the online calibration module group for mixed gas has a modular structure to meet the test requirements of different flow levels or different gas types.

[0018] Preferably, in one embodiment of this application, the mixer is a Venturi mixer.

[0019] Preferably, in one embodiment of this application, the differential pressure mass flow meter is used to measure the mass flow rate of gas under unsteady flow conditions, and the embedded processor completes the flow rate calculation by calculating the pressure difference and temperature correction coefficient.

[0020] Preferably, in one embodiment of this application, the pressure reducing valve assembly and the valve assembly are made of high temperature and corrosion resistant materials, and the valve assembly is disposed between the gas source end and the mass flow controller for gas circuit opening and closing and safety control.

[0021] Preferably, in one embodiment of this application, the cable flame retardant testing device is provided with a pipeline leakage detection module for detecting pressure changes in propane or air pipelines.

[0022] Preferably, in one embodiment of this application, the online calibration module group for mixed gas is connected to the data recording system, which is used to store the mixed gas flow rate, temperature and pressure data throughout the test process.

[0023] Preferably, in one embodiment of this application, a method for online calibration of mixed gas flow in a cable combustion test includes the following steps:

[0024] Step 1: Turn on the propane gas source and the air gas source, and adjust the pressure reducing valve group to make the gas line pressure between 0.1MPa and 0.2MPa;

[0025] Step 2: Start the online calibration module group for mixed gas and perform zero-point calibration;

[0026] Step 3: Set the propane mass flow rate to approximately 400–480 mg / s and the air mass flow rate to approximately 1400–1700 mg / s, and ignite the blowtorch;

[0027] Step 4: Collect and display real-time traffic data using an embedded processor, and obtain the drift curve by fitting 30 minutes of data using the least squares method;

[0028] Step 5: Adjust the outputs of the propane mass flow controller and the air mass flow controller based on the fitting results until the mixed gas power and flame shape reach the target range.

[0029] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0030] The technical solution of this application has achieved the following technical advancements:

[0031] 1. In order to solve the problems of insufficient control accuracy of mixed gas flow and unstable blowtorch power and flame shape in GB / T 31248 test, a structural design of an online calibration module for mixed gas is adopted in series downstream of the propane and air mass flow controller. The gas flow data is monitored in real time through temperature and pressure sensors, differential pressure mass flow meter and embedded processor. This overcomes the defects of traditional calibration methods, such as the need to disassemble the flow controller and the inability to detect gas leaks in the pipeline. The technical effect of real-time visualization of mixed gas flow and constant output of blowtorch power is achieved.

[0032] 2. In order to solve the problems of drift after long-term use of mass flow controllers and the inability of ordinary experimental personnel to perform self-checks, a flow data fitting calculation unit based on the least squares method and an online calibration mechanism are adopted to achieve automatic correction and drift compensation. This overcomes the shortcomings of traditional calibration, which can only be performed in ideal experimental environments and cannot reflect the actual operating status. It achieves the technical effect of long-term stability of the test device and intelligent calibration process.

[0033] 3. In order to solve the problems of complex operation, condensation error and poor real-time performance of the standard gas weighing method, a detection method that integrates differential pressure mass flow measurement and embedded computing module control is adopted. This method overcomes the defects of gas cylinder heat absorption and condensation water causing measurement inaccuracy, and achieves the technical effect of high detection efficiency, fast real-time response and high result accuracy.

[0034] 4. In order to solve the problems of complex maintenance of the test device and insufficient safety of the testing process, a modular hardware and software structure and a pressure anomaly detection mechanism are adopted to overcome the limitations of the existing system in lacking pipeline status monitoring, and achieve the technical effects of convenient use, safety and reliability, and low maintenance cost.

[0035] 5. In order to solve the problems of poor repeatability and insufficient traceability of experimental results, a real-time data acquisition and recording display system was adopted to realize data tracking and visualization throughout the entire experimental process. This overcame the shortcomings of traditional experiments in lacking process control and feedback, and achieved the technical effect of quantifiable, highly comparable and reproducible experimental results. Attached Figure Description

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0037] Figure 1 This is a schematic diagram of the pipeline installation of an online calibration device for the mixed gas flow rate of a cable combustion testing apparatus according to the present invention;

[0038] Figure 2 This is a structural diagram of the mixed gas online calibration module group of the mixed gas flow online calibration device of the cable combustion test apparatus of the present invention;

[0039] Components in the diagram:

[0040] 1. Propane gas source

[0041] 2. Air source

[0042] 301. Pressure reducing valve I

[0043] 302. Pressure reducing valve II

[0044] 401. Ball Valve I

[0045] 402. Ball Valve II

[0046] 5. Propane mass flow controller

[0047] 6. Air mass flow controller

[0048] 701. Pressure Gauge I

[0049] 702, Pressure Gauge II

[0050] 801. Online Calibration Module for Mixed Gas

[0051] 802. Online Calibration Module for Mixed Gas

[0052] 9. Mixer

[0053] 10. Blowtorch

[0054] 11. Temperature and pressure sensors

[0055] 12. Differential pressure mass flow meter

[0056] 13. Embedded processor

[0057] 14. Display screen. Detailed Implementation

[0058] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings. These embodiments are only for illustrating this application and are not intended to limit the invention.

[0059] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0060] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0062] like Figures 1-2A mixed gas flow online calibration device for a cable combustion test apparatus includes a propane gas source 1, an air gas source 2, a pressure reducing valve group, a ball valve group, a propane mass flow controller 5, an air mass flow controller 6, a pressure detection group, a mixed gas online calibration module group, a mixer 9, and a blowtorch 10.

[0063] The pressure reducing valve assembly includes pressure reducing valve I 301 and pressure reducing valve II 302; the ball valve assembly includes ball valve I 401 and ball valve II 402; and the pressure detection assembly includes pressure gauge I 701 and pressure gauge II 702.

[0064] The online calibration module group for mixed gas includes online calibration module I 801, online calibration module II 802 for mixed gas, temperature and pressure sensor 11, differential pressure mass flow meter 12, embedded processor 13, and display screen 14, which are used to collect temperature, pressure and flow data and perform real-time calibration and correction of the flow controller.

[0065] The online calibration module for the mixed gas is located downstream of the propane mass flow controller 5 and the air mass flow controller 6 to perform real-time flow detection and calibration of the mixed gas entering the mixer 9.

[0066] Propane gas source 1, pressure reducing valve I 301, ball valve I 401, propane mass flow controller 5, pressure gauge I 701, and mixed gas online calibration module I 801 are connected in series. Air source 2, pressure reducing valve II 302, ball valve II 402, air mass flow controller 6, pressure gauge II 702, and mixed gas online calibration module II 802 are connected in series. The output terminals of mixed gas online calibration module I 801 and mixed gas online calibration module II 802 are connected in parallel to mixer 9. Mixer 9 is connected to blowtorch 10.

[0067] When implementing this application, the key points are as follows:

[0068] By setting up online calibration modules for mixed gas downstream of propane and air mass flow controllers respectively, real-time monitoring, dynamic correction and automatic compensation of gas flow can be achieved. The system inputs temperature, pressure and differential pressure flow signals into an embedded processor. After algorithm fitting and data analysis, the output of the flow controller is corrected by feedback, thereby ensuring the long-term stability of the torch flame power and shape.

[0069] The working principle or process of this application is as follows:

[0070] Before the test, the propane and air gas sources were turned on, and the gas pressure was adjusted to the set range through the pressure reducing valve group. Then, the online calibration module of the mixed gas was started, and the system automatically performed zero-point calibration to eliminate the initial error of the sensor. During the test, propane and air were accurately measured by the mass flow controller and then entered their respective online calibration modules. The temperature and pressure sensors and differential pressure mass flow meters in the modules synchronously collected the gas flow and status parameters and transmitted the real-time data to the embedded processor for analysis.

[0071] Furthermore, by combining the least squares-based fitting algorithm built into the embedded processor, the flow rate drift trend over time can be calculated, and the flow rate setpoints of propane and air can be automatically corrected according to the fitting results to achieve closed-loop flow control. When flow fluctuations or abnormalities are detected, the system can immediately alarm or adjust the output to ensure a constant mixed gas ratio and stable torch power. The mixed gas is uniformly mixed by a Venturi mixer before entering the torch to form a standardized flame for flame retardant performance testing.

[0072] The device is designed to achieve real-time calibration and process self-checking of gas flow. It can monitor pipeline leaks and maintain a constant torch ignition power over a long period of time, significantly improving the accuracy, repeatability and traceability of flame retardant tests.

[0073] Specifically, in one embodiment of this application, the embedded processor 13 is electrically connected to the display screen 14 to display the mass flow rate, temperature, pressure, and their change curves of the mixed gas in real time for online monitoring; the embedded processor 13 is equipped with a fitting calculation unit based on the least squares method, which calculates the drift amount based on the collected flow data and automatically compensates the outputs of the propane mass flow controller 5 and the air mass flow controller 6 to stabilize the output power of the blowtorch 10; the mixed gas online calibration module group has a modular structure to meet the test requirements of different flow levels or different gas types; the mixer 9 is a Venturi mixer;

[0074] To address the issues of insufficient accuracy in mixed gas flow measurement and unstable torch power and flame shape, an embedded processor 13 is electrically connected to a display screen 14 to display the mixed gas mass flow rate, temperature, pressure, and their variation curves in real time, enabling online monitoring. Simultaneously, a least-squares-based fitting calculation unit is configured to perform drift calculations on the collected flow data and automatically correct the outputs of the propane mass flow controller 5 and the air mass flow controller 6. This overcomes the shortcomings of traditional flow controllers, such as the inability to perform real-time self-checks and difficulties in drift compensation, achieving the technical effects of constant torch output power, stable flame shape, and repeatable test results. The mixed gas online calibration module adopts a modular structure, allowing for flexible replacement or expansion according to different flow levels or gas types, achieving structural adaptation and upgrades. Meanwhile, the mixer 9 uses a Venturi mixer or an equivalent eddy current mixer to ensure thorough and uniform gas mixing, guaranteeing torch flame stability. The entire implementation scheme, through reasonable pipeline and sensor placement, the use of high-temperature and corrosion-resistant materials, and the setting of online calibration and drift compensation logic, achieves the expected technical effects of simple operation, safety and reliability, traceable testing, and highly consistent results.

[0075] Specifically, in one embodiment of this application, the differential pressure mass flow meter 12 is used to measure the mass flow rate of gas under non-steady-state flow conditions, and the embedded processor 13 calculates the flow rate by calculating the pressure difference and temperature correction coefficient; the pressure reducing valve group and the valve group are made of high-temperature resistant and corrosion-resistant materials, and the valve group is set between the gas source end and the mass flow controller for gas path opening and closing and safety control; the cable flame retardant testing device is equipped with a pipeline leakage detection module for detecting pressure changes in propane or air pipelines; the mixed gas online calibration module group is connected to the data recording system, and the data recording system is used to store the mixed gas flow rate, temperature and pressure data of the entire test process;

[0076] To address the issues of inaccurate gas flow measurement, inability to monitor pipeline leaks in real time, and lack of traceability of test data under unsteady flow conditions, a differential pressure mass flow meter 12 is used in conjunction with an embedded processor 13. The mixed gas flow rate is obtained in real time through pressure difference calculation and temperature correction coefficient. A pressure reducing valve assembly and valve assembly made of high-temperature and corrosion-resistant materials are used to achieve gas path opening and closing and safety control. Simultaneously, a pipeline leak detection module is set up to monitor changes in propane or air pipeline pressure in real time. The mixed gas online calibration module is connected to the data recording system, enabling the storage and tracking of mixed gas flow, temperature, and pressure data throughout the entire test process. This overcomes the shortcomings of traditional methods, such as large measurement errors, inability to perform online self-checks, and lack of data traceability. The solution achieves high flow measurement accuracy, system safety and reliability, monitorable pipeline status, and quantifiable and reproducible test data. This implementation scheme can replace the differential pressure mass flow meter with an equivalent differential pressure or turbine mass flow meter, and the pipeline material can be other high-temperature and corrosion-resistant metals or composite materials to achieve the same functionality and technical effects.

[0077] Specifically, in one embodiment of this application, a method for online calibration of mixed gas flow in a cable combustion test includes the following steps:

[0078] Step 1: Turn on propane gas source 1 and air gas source 2, and adjust the pressure reducing valve group to make the gas line pressure between 0.1MPa and 0.2MPa;

[0079] Step 2: Start the online calibration module group for mixed gas and perform zero-point calibration;

[0080] Step 3: Set the propane mass flow rate to approximately 400–480 mg / s and the air mass flow rate to approximately 1400–1700 mg / s, and ignite the blowtorch 10;

[0081] Step 4: Collect and display real-time traffic data through embedded processor 13, and obtain the drift curve by fitting 30 minutes of data using the least squares method;

[0082] Step 5: Adjust the outputs of propane mass flow controller 5 and air mass flow controller 6 based on the fitting results until the mixed gas power and flame shape reach the target range.

[0083] To address the issues of insufficient flow control accuracy of mixed gas and unstable torch power and flame shape in cable flame retardant testing, an online mixed gas calibration module, coupled with an embedded processor 13, was used to collect flow, temperature, and pressure data in real time. The least squares method was used to fit 30 minutes of data to obtain flow drift trends. Combined with zero-point calibration and dynamic correction of the outputs of propane and air mass flow controllers, stable control of torch power and flame shape was achieved. This overcomes the shortcomings of traditional calibration methods, which require disassembling and reassembling flow controllers and cannot reflect on-site pipeline leaks and real-time drift. The result is a technically effective system with monitorable testing process, high flow accuracy, strong flame stability, and repeatable results. During implementation, it is essential to ensure accurate opening and closing of pressure reducing valves and other valves, and good pipeline sealing. The least squares method can be replaced with other equivalent curve fitting or filtering algorithms to achieve the same calibration and correction effects.

[0084] Specifically, in one embodiment of this application, the cable flame retardant testing device includes a device for online calibration of the mixed gas flow rate of the test device according to GB / T 31248-2014.

[0085] The cable flame retardant testing device includes a propane gas source 1, an air gas source 2, a pressure reducing valve group, a ball valve group, a propane mass flow controller 5, an air mass flow controller 6, a pressure detection group, a mixed gas online calibration module group, a Venturi mixer 9, and a blowtorch 10.

[0086] The pressure reducing valve assembly includes pressure reducing valve I 301 and pressure reducing valve II 302; the ball valve assembly includes ball valve I 401 and ball valve II 402; and the pressure detection assembly includes pressure gauge I 701 and pressure gauge I 702.

[0087] The online calibration module group for mixed gas includes online calibration module I 801 and online calibration module II 802 for mixed gas. Online calibration modules I 801 and online calibration module II 802 for mixed gas are equipped with temperature and pressure sensors 11, differential pressure mass flow meters 12, embedded processors 13 and displays 14.

[0088] Pressure reducing valve I301 is connected to propane gas source 1 via a stainless steel pipe;

[0089] Pressure reducing valve II302 is connected to air source 2 via a stainless steel pipe;

[0090] Ball valve I 401 is connected to pressure reducing valve I 301 via a stainless steel pipe, and ball valve II 402 is connected to pressure reducing valve II 302 via a stainless steel pipe.

[0091] The propane mass flow controller 5 is connected to the ball valve I401 via a stainless steel pipe;

[0092] The air mass flow controller 6 is connected to the ball valve II402 via a stainless steel pipe;

[0093] Pressure gauge I701 is connected to propane mass flow controller 5 via a stainless steel pipe;

[0094] Pressure gauge II702 is connected to air mass flow controller 6 via a stainless steel pipe;

[0095] The mixed gas online calibration module I801 is connected to the propane mass flow controller 5 via a hose;

[0096] The mixed gas online calibration module II802 is connected to the air mass flow controller 6 via a hose;

[0097] Mixer 9 is connected to online calibration module I 801 and online calibration module II 802 for mixed gas via flexible hoses;

[0098] The blowtorch 10 and the mixer 9 are connected by a copper pipe;

[0099] The specific implementation is as follows:

[0100] Step 1: The online calibration module group for mixed gas is connected in series downstream of the propane mass flow controller 5 and the air mass flow controller 6 according to the pipeline connection diagram;

[0101] Step 2: Turn on propane gas source 1 and air gas source 2;

[0102] Step 3: Open the ball valve assembly, observe the pressure gauge assembly, and adjust the pressure reducing valve assembly to make the pipeline pressure 0.1MPa~0.2MPa;

[0103] Step 4: Turn on the online calibration module group for mixed gas, preheat the propane mass flow controller of propane source 1 for 5 minutes, and then perform zero-point calibration.

[0104] Step 5: Turn on and adjust the propane mass flow controller 5 and the air mass flow controller 6 so that the input flow rate is 442 mg / s for propane and 1550 mg / s for air. Ignite the blowtorch 10.

[0105] Step 6: Display screen 14 shows the real-time pipeline mixed gas flow rate. After collecting 30 minutes of data, the curve is fitted using the least squares method.

[0106] Step 7: The test personnel calibrate the mass flow controller based on the real-time pipeline flow rate and the 30-minute fitting data;

[0107] First, existing technologies fail to consider issues such as leaks in the manufacturer's pipelines, inaccuracies in the mass flow controller after calibration due to improper installation by installers, and drift in mass flow control after prolonged and repeated use, which ordinary laboratory personnel cannot effectively self-check. Second, the standard gas absorbs heat during use, leading to condensation on the gas cylinder and pipeline, affecting the weighing quality, and cannot measure the real-time mass flow rate of the mixed gas in the pipeline, thus failing to guarantee the stability of the mass flow controller throughout the entire process.

[0108] This invention relates to an apparatus and method for online calibration of mixed gas flow rate in a GB / T 31248-2014 test device. By using on-site online calibration, it solves practical problems inherent in traditional calibration methods, such as improper disassembly and installation of the flow controller, inability to monitor on-site pipeline leaks, and the inability of ordinary laboratory personnel to perform self-inspections. This invention adds the function of real-time monitoring of the mixed gas flow rate in the GB / T 31248 test device, facilitating laboratory personnel to check for pipeline leaks. By fitting real-time values ​​over a period of time, this invention confirms the drift and noise of the mixed gas flow rate in the test device, thereby more accurately calibrating the test device, improving the accuracy and stability of the mixed gas flow rate in the GB / T 31248 test device, improving the accuracy and stability of the fixed torch flame source power and flame shape, and thus improving the stability of the cable combustion process and the accuracy of the test results.

[0109] This invention is an independently developed technology that fills a gap in this field both domestically and internationally. The process is simple and the workflow is clear, which can effectively improve the stability and reproducibility of the experiment.

[0110] In summary, this invention aims to address the technical problems in existing GB / T 31248-2014 cable flame retardancy testing, such as insufficient accuracy in mixed gas flow control, unstable blowtorch ignition power and flame shape, and the need for disassembly and calibration of mass flow controllers with no on-site self-testing capability. By constructing a testing device and method capable of real-time monitoring, online calibration, and automatic correction of mixed gas, this invention improves the accuracy and stability of gas flow control, ensures constant blowtorch ignition power and consistent combustion state, thereby enhancing the reliability and reproducibility of cable combustion performance testing.

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. An online calibration device for the mixed gas flow rate of a cable combustion test apparatus, characterized in that, It includes a propane gas source (1), an air gas source (2), a pressure reducing valve group, a ball valve group, a propane mass flow controller (5), an air mass flow controller (6), a pressure detection group, a mixed gas online calibration module group, a mixer (9), and a blowtorch (10); The pressure reducing valve assembly includes pressure reducing valve I (301) and pressure reducing valve II (302); the ball valve assembly includes ball valve I (401) and ball valve II (402); and the pressure detection assembly includes pressure gauge I (701) and pressure gauge II (702). The online calibration module group for mixed gas includes online calibration module I (801), online calibration module II (802), temperature and pressure sensor (11), differential pressure mass flow meter (12), embedded processor (13), and display screen (14), which are used to collect temperature, pressure and flow data and perform real-time calibration and correction of the flow controller. The online calibration module for mixed gas is located downstream of the propane mass flow controller (5) and the air mass flow controller (6) to perform real-time flow detection and calibration of the mixed gas entering the mixer (9); Propane gas source (1), pressure reducing valve I (301), ball valve I (401), propane mass flow controller (5), pressure gauge I (701), and mixed gas online calibration module I (801) are connected in series. Air source (2), pressure reducing valve II (302), ball valve II (402), air mass flow controller (6), pressure gauge II (702), and mixed gas online calibration module II (802) are connected in series. The output terminals of mixed gas online calibration module I (801) and mixed gas online calibration module II (802) are connected in parallel to mixer (9). Mixer (9) is connected to blowtorch (10).

2. The online calibration device for mixed gas flow rate of a cable combustion test apparatus as described in claim 1, characterized in that, The embedded processor (13) is electrically connected to the display screen (14) to display the mass flow rate, temperature, pressure and their change curves of the mixed gas in real time for online monitoring.

3. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 2, characterized in that, The embedded processor (13) is equipped with a least squares-based fitting calculation unit, which calculates the drift based on the collected flow data and automatically compensates the outputs of the propane mass flow controller (5) and the air mass flow controller (6) to stabilize the output power of the blowtorch (10).

4. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 1, characterized in that, The mixed gas online calibration module group has a modular structure to meet the test requirements of different flow levels or different gas types.

5. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 1, characterized in that, The mixer (9) is a Venturi mixer.

6. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 3, characterized in that, The differential pressure mass flow meter (12) is used to measure the mass flow of gas under unsteady flow conditions, and the embedded processor (13) calculates the flow rate by calculating the pressure difference and temperature correction factor.

7. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 1, characterized in that, The pressure reducing valve assembly and valve assembly are made of high temperature and corrosion resistant materials. The valve assembly is located between the gas source and the mass flow controller and is used for gas circuit opening and closing and safety control.

8. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 1, characterized in that, The cable flame retardant testing device is equipped with a pipeline leakage detection module, which is used to detect pressure changes in propane or air pipelines.

9. The online calibration device for mixed gas flow of a cable combustion test apparatus as described in claim 6, characterized in that, The online calibration module for mixed gas is connected to the data recording system, which stores the flow rate, temperature, and pressure data of the mixed gas throughout the entire test process.

10. A method for online calibration of mixed gas flow rate in a cable combustion test, using the online calibration device for mixed gas flow rate of the cable combustion test apparatus according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Turn on the propane gas source (1) and the air gas source (2), and adjust the pressure reducing valve group to make the gas line pressure between 0.1MPa and 0.2MPa; Step 2: Start the online calibration module group for mixed gas and perform zero-point calibration; Step 3: Set the propane mass flow rate to 400-480 mg / s and the air mass flow rate to 1400-1700 mg / s, and ignite the blowtorch (10); Step 4: Collect and display real-time traffic data through the embedded processor (13), and obtain the drift curve by fitting 30 minutes of data using the least squares method; Step 5: Adjust the outputs of the propane mass flow controller (5) and the air mass flow controller (6) according to the fitting results until the mixed gas power and flame shape reach the target range.

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