Method for checking air tightness of aircraft conduit joint

Abstract

The invention belongs to the technical field of aircraft assembly detection, and relates to a method for checking the air tightness of an aircraft conduit joint. According to the novel detection device, the technology is used for detecting airtight leakage points of the aircraft conduit in actual production, a fault connector can be quickly positioned, and the severity of nitrogen leakage can be accurately judged. The method is very important for rapid and accurate positioning and repairing directly carried out on the aircraft maintenance or assembly site, and it is helpful to ensure that the aircraft recovers the flight or assembly state within the shortest time. In practical application, the detection device can automatically record nitrogen leakage data and carry out real-time analysis. Therefore, assembly workers or maintenance personnel can quickly obtain accurate data, deeply analyze the air tightness of the conduit joint, accurately find out the root of the problem and perform corresponding processing, and the troubleshooting or maintenance efficiency is greatly improved. For air tightness detection of a conduit joint, accurate recording and traceability of data are crucial for aircraft safety.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft assembly detection, and relates to a method for checking the air tightness of an aircraft conduit joint. Background Art

[0002] In view of the importance of air tightness inspection of aircraft duct joints and the limitations of traditional methods, the present invention proposes a method for directly detecting nitrogen leakage of aircraft duct joints, and judges the nitrogen leakage of duct joints by real-time monitoring of changes in nitrogen content in the atmosphere, thereby achieving rapid and accurate identification of trace gas leakage.

[0003] Traditional methods for testing the air tightness of aircraft duct joints often use indirect detection methods, such as liquid detection or observing pressure values, to infer the air tightness of duct joints. However, the above methods are cumbersome, time-consuming, and difficult to ensure accuracy, especially for the rapid identification of trace gas leakage. Therefore, it is necessary to propose a more direct, fast and accurate method to evaluate the air tightness of aircraft duct joints.

[0004] The present invention has proposed a breakthrough method for directly detecting nitrogen leakage in aircraft duct joints. Through specific detection devices and sensor technology, it is possible to detect slight changes in the nitrogen content in the atmosphere in a confined space in real time. Once there is nitrogen leakage in the duct joint, it will lead to changes in the nitrogen content in the atmosphere. Through data analysis and algorithm processing, it is possible to quickly and accurately identify trace gas leakage, providing timely and accurate judgment basis for aircraft maintenance personnel.

[0005] This new method of directly detecting nitrogen leaks in conduit joints not only greatly simplifies the process of airtightness testing, improves the accuracy and efficiency of testing, but also makes it possible to quickly identify trace gas leaks. The innovation and practicality of this background technology is expected to bring important breakthroughs in the field of aircraft assembly testing and provide more reliable protection for aircraft safe flight. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for checking the air tightness of an aircraft duct joint.

[0007] The technical solution of the present invention is as follows:

[0008] A method for checking the air tightness of an aircraft duct joint, the steps are as follows:

[0009] Step 1: Check the test device before operation to ensure the cleanliness of the inside and outside of the test device, the pipelines and the outside of the functional accessories; verify whether the pressure gauge is within the regular inspection period; confirm that the display screen and other functions on the test device are in good condition; confirm that the power supply line, airtight sealing strips and other serviceable parts are within the validity period; check whether the airtight sealing strips are in good condition and should not be damaged by aging, cracking, etc.; check whether the spherical reflector has a complete mirror surface and is free of scratches, cracks and other damage.

[0010] Step 2: Before turning on the test device, connect one end of the grounding wire to the test device and the other end to the grounding post; check that the power supply of the device is in the off state.

[0011] Step 3: According to the aircraft test requirements, place the pipe joint to be tested into the detachable sealing housing, adjust the pipeline posture, complete the splicing of the detachable sealing housing, and adjust the adjustable variable diameter sealing cover according to the catheter diameter to ensure the sealing of the device.

[0012] Step 4: Connect the laser emitter and optical sensor equipped with the airtight inspection device to the detachable optical sealing device through the equipment interface, and use the device bracket to ensure the stability of the optical sealing device.

[0013] Step 5: Start the computer and use the computer to send a command to the PLC control unit to initialize the system of the inspection device. The PLC control unit will test the device circuit. If a circuit fault occurs, the PLC control unit will retest the device circuit after manual troubleshooting. The test will be started after there is no circuit fault. During the test, observe the gas pressure display. If the pressure inside the device exceeds the warning line, immediately open the exhaust valve to reduce the pressure inside the device to a safe range.

[0014] Step 6: Send commands to the PLC control unit through the computer, adjust the electronic control equipment and temperature control equipment, control the laser transmitter to emit infrared laser with a wavelength that meets the test requirements, receive the laser signal emitted from the optical sealing device through the optical sensor, convert the optical signal into an electrical signal through the signal processor, use the frequency modulation amplifier to modulate the wavelength and reduce the influence of stray noise, and finally return the signal to the computer for analysis and processing. Judge whether the air tightness of the aircraft duct joint is good through the computer display. If there is a problem with the air tightness, open the exhaust valve, release the pressure in the device, disassemble the device for troubleshooting, and re-test until the joint air tightness shows good.

[0015] Step 7: After the test, open the exhaust valve, complete the pressure relief work and disassemble the device, control the PLC control unit through the computer, turn off the electronic control equipment and temperature control equipment, and after confirming that the device is in the off state, disconnect the laser emitter and optical sensor from the detachable optical sealing device.

[0016] Step 8: Disconnect the grounding wire from the test bench and the test site grounding piles, and recycle all external devices into the storage box; clean the operation panel and outer surface of the airtight inspection device.

[0017] A test device for the air tightness of an aircraft duct joint comprises a data acquisition part and a data analysis part.

[0018] The data acquisition part includes a detachable sealing shell, an airtight sealing strip, a spherical reflector, an adjustable variable diameter sealing cover, an equipment interface, a gas pressure gauge, an exhaust valve and a device bracket.

[0019] The detachable sealed shell is a sealing component of the present invention, which is mainly composed of eight detachable split structures. It is designed in a split splicing form, which is conducive to the splicing of tooling in a closed space and improves the efficiency of tooling disassembly and assembly of operators. The airtight sealing strip is a sealing component of the present invention, which is mostly a rectangular cross-section adhesive sealing strip with a material grade of 5180 / 5080, used to ensure the sealing of the gap between the spliced ​​shells. The spherical reflector is an optical path adjustment device of the present invention, which is located in the optical sealing device, wherein two mirrors are installed in one section of the device, and another larger mirror is installed at the other end. The laser realizes optical path adjustment through multiple reflections of the reflector to ensure the accuracy of nitrogen concentration parameter collection. The adjustable variable diameter sealing cover is a sealing component of the present invention, which realizes the inspection of multiple diameter catheters with a maximum diameter of 150mm through a flexible adjustment interface, and ensures the overall sealing of the optical sealing device through the contraction of the flexible cover. The equipment interface is used to connect the laser emitter and the optical sensor with the optical sealing device, and a sealing strip is bonded at the connection with the electrical components inside the device to ensure the overall sealing of the optical sealing device. The gas pressure gauge is a monitoring device of the present invention, which is used to monitor the gas pressure in the optical sealing device. The exhaust valve is a safety device of the present invention, which is used to release the gas in the optical sealing device to prevent the device from being over-pressured and causing danger. The device bracket is a structural support member of the present invention, which plays a role in stably supporting the data acquisition device and improving the accuracy of the test.

[0020] The data analysis part includes a computer, a PLC control unit, an electric control device, a temperature control device, a laser transmitter, an optical sensor, a signal processor, a frequency modulation amplifier, a device housing, a mobile wheel and a storage box. The computer is the instruction and analysis device of the present invention. The computer and the PLC control unit communicate through the core control software, send out system operation signals, and receive the collected data signals for analysis. The PLC control unit is the control device of the present invention. It receives the communication command of the computer through the external interface provided by the PLC, performs logical operations and outputs control signals to control the operation of various electronic devices. The electric control device is the control device of the present invention, which is used to output a stable current source to provide working current to the laser transmitter. The temperature control device is the control device of the present invention, which is used to accurately control the working temperature of the laser transmitter so that the laser transmitter can stably output a certain wavelength of laser. The laser transmitter is the output device of the present invention, which is used to output an infrared laser with a wavelength of 2700nm to ensure the absorption of nitrogen concentration. The optical sensor is the receiving device of the present invention, which is used to collect the infrared laser emitted after reflection in the optical sealing device. The signal processor is the conversion device of the present invention, which is used to convert the optical signal into an electrical signal. The frequency modulation amplifier is the regulating device of the present invention, which mainly reduces the influence of stray noise by wavelength modulation of the converted electrical signal, improves the sensitivity of the detection system, and sends it to the computer for data processing. The device housing is the main load-bearing and containing structure of the present invention, which plays the role of supporting the device components and accommodating internal equipment. The mobile wheels are the movable structures of the present invention, which facilitate the overall transfer of the inspection device. The storage box is the storage structure of the present invention, which adopts a push-pull storage box to replace the original external storage form, and directly stores the hose, transmitter, sensor, etc. of the inspection device into the interior of the inspection device, thereby improving the convenience of storage of the inspection device.

[0021] Beneficial effects of the present invention:

[0022] 1) Accurate detection capability: Through the new detection device, the technology is used in actual production to check the airtight leakage points of aircraft ducts, quickly locate the faulty joints, and accurately determine the severity of nitrogen leakage. This is very important for rapid and accurate positioning and repair directly at the aircraft maintenance or assembly site, helping to ensure that the aircraft returns to flight or assembly status in the shortest time.

[0023] 2) Data collection and analysis: In actual applications, the detection device can automatically record nitrogen leakage data and conduct real-time analysis. This allows assembly workers or maintenance personnel to quickly obtain accurate data, conduct in-depth analysis of the air tightness of the catheter joint, accurately identify the root cause of the problem and take corresponding measures, greatly improving the efficiency of troubleshooting or maintenance.

[0024] 3) Traceability: For the air tightness test of the duct joint, accurate recording and traceability of data are crucial to aircraft safety. By combining with the PLC automatic control unit, the accuracy and traceability of the test results can be ensured, which helps to track the causes and consequences of duct air tightness problems.

[0025] 4) Reduce human factors: In the actual test process, traditional methods have the risk of human operation errors, while new technologies have a higher degree of automation, which reduces the impact of human factors, further improves detection accuracy and stability, and ensures the smooth progress of aircraft assembly work.

[0026] 5) Improved production efficiency: The implementation of this technology is expected to reduce troubleshooting time, quickly and accurately locate and repair duct airtightness problems, thereby minimizing aircraft assembly cycles or reducing aircraft downtime. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Basic principles of gas flow path detection;

[0028] Figure 2 Schematic diagram of airtightness detection test;

[0029] Figure 3 Basic principle diagram of laser acquisition;

[0030] Figure 4 PLC control flow chart of airtight system;

[0031] Figure 5 This is the schematic diagram of the air tightness inspection of the aircraft duct joint;

[0032] Figure 6 is a diagram of a detachable optical sealing device;

[0033] Fig. 7(a) is a diagram of an airtight inspection device;

[0034] FIG. 7( b ) is a diagram of an airtightness inspection device.

[0035] Among them, the solid line in the figure is the signal transmission path, the dotted line is the PLC control path, 1-detachable sealing shell, 2-airtight sealing strip, 3-spherical reflector, 4-adjustable variable diameter sealing cover, 5-device interface, 6-gas pressure gauge, 7-exhaust valve, 8-device bracket, 9-computer, 10-PLC control unit, 11-electric control equipment, 12-temperature control equipment, 13-laser transmitter, 14-optical sensor, 15-signal processor, 16-FM amplifier, 17-device housing, 18-moving wheels, 19-storage box. DETAILED DESCRIPTION

[0036] Embodiment 1:

[0037] A method for checking the air tightness of an aircraft duct joint, the steps are as follows:

[0038] Step 1: Check the test device before operation to ensure the cleanliness of the inside and outside of the test device, the pipelines and the outside of the functional accessories; verify whether the pressure gauge is within the regular inspection period; confirm that the display screen and other functions on the test device are in good condition; confirm that the power supply line, airtight sealing strip 2 and other serviceable parts are within the validity period; check whether the airtight sealing strip 2 is in good condition and should not be damaged by aging, cracking, etc.; check whether the spherical reflector 3 has a complete mirror surface and is free of scratches, cracks and other damage.

[0039] Step 2: Before turning on the test device, connect one end of the grounding wire to the test device and the other end to the grounding post; check that the power supply of the device is in the off state.

[0040] Step 3: According to the aircraft test requirements, place the pipe joint to be tested into the detachable sealing housing 1, adjust the pipeline posture, complete the splicing of the detachable sealing housing 1, and adjust the adjustable variable diameter sealing cover 4 according to the catheter diameter to ensure the sealing of the device.

[0041] Step 4: Connect the laser emitter 13 and the optical sensor 14 of the airtight inspection device to the detachable optical sealing device through the device interface 5, and use the device bracket 8 to ensure the stability of the optical sealing device.

[0042] Step 5: Start the computer 9, and use the computer 9 to send a command to the PLC control unit 10 to initialize the system of the inspection device. The PLC control unit 10 tests the device circuit. If a circuit fault occurs, the PLC control unit 10 retests the device circuit after manual troubleshooting. The test is started after there is no circuit fault. During the test, observe the reading of the gas pressure gauge 6. If the pressure in the device exceeds the warning line, immediately open the exhaust valve 7 to reduce the pressure in the device to a safe range.

[0043] Step six: Send a command to the PLC control unit 10 through the computer 9, adjust the electronic control equipment 11 and the temperature control equipment 12, control the laser transmitter 13 to emit an infrared laser with a wavelength that meets the test requirements, receive the laser signal emitted from the optical sealing device through the optical sensor 14, convert the optical signal into an electrical signal through the signal processor 15, use the frequency modulation amplifier 16 to modulate the wavelength and reduce the influence of stray noise, and finally return the signal to the computer 9 for analysis and processing, and judge whether the air tightness of the aircraft duct joint is good through the display screen of the computer 9. If there is a problem with the air tightness, open the exhaust valve 7, release the pressure in the device, disassemble the device for troubleshooting, and re-test until the air tightness of the joint is good.

[0044] Step 7: After the test, open the exhaust valve 7, complete the pressure relief work and disassemble the device, control the PLC control unit 10 through the computer 9, turn off the electronic control equipment 11 and the temperature control equipment 12, and after confirming that the device is in the closed state, disconnect the laser emitter 13 and the optical sensor 14 from the detachable optical sealing device.

[0045] Step 8: Disconnect the grounding wire from the test bench and the test site grounding piles, and recycle all external devices into the storage box 19; clean the operation panel and outer surface of the airtight inspection device.

[0046] Embodiment 2:

[0047] 3.1 Basic principles of airtightness detection

[0048] Nitrogen is a commonly used gas for testing the tightness of system ducts in aircraft fuel tanks. Its concentration measurement under normal conditions is affected by the nitrogen content in the atmosphere (about 78%). For detection methods with low detection sensitivity, such as traditional water detection methods (foam smearing and water bubbles), it is difficult to accurately measure the change in the content of trace nitrogen when the duct joint leaks. Ultrasonic and halogen detection methods are limited by the assembly environment and product design and cannot be used for airtight detection of system pipelines in aircraft. The present invention designs airtight detection technology based on the principle of tunable semiconductor laser spectroscopy technology. It uses the principle that laser energy is absorbed by the "selective frequency" of gas molecules to form a unique spectrum of nitrogen to measure subtle concentration changes of the test gas. It has the advantages of high sensitivity, high response, and high safety. The detection limit can reach the ppb (parts per billion) level. The present invention involves the basic principle of test gas flow path detection. Figure 1 .

[0049] 3.2 Principle of airtightness detection test

[0050] Figure 2 The figure is a schematic diagram of the principle of the airtight detection test. The laser wavelength used in the present invention is 2700nm. The single absorption line of nitrogen near 2700nm is detected to achieve rapid online detection of nitrogen concentration. The temperature control device is controlled by a computer to stabilize the working temperature of the laser transmitter, so that the laser transmitter can stably output 2700nm wavelength laser. The electric control device is used to provide a stable working voltage for the laser. The laser transmitter sends a signal laser into the airtight acquisition device of the catheter joint. The detection joint is sealed in the airtight acquisition device. The laser is optically reflected in the sealed device, received by the probe of the optical sensor and converted into an optical signal, which is converted into an electrical signal by the signal processor, and demodulated by the frequency modulation amplifier to obtain a harmonic signal, thereby reducing the influence of useless frequency noise. Finally, the computer performs data processing.

[0051] 3.3 Catheter joint airtight collection principle

[0052] The catheter joint airtight acquisition device adopts a detachable optical sealing device based on the characteristics of the system catheter in the fuel tank of an aircraft. The detection sensitivity is improved by installing three spherical reflectors with the same curvature radius. Two of the mirrors are installed at one end of the device, and the larger mirror is installed at the other end. The optical path is adjusted by the number of laser reflections to ensure that the optical path meets the test requirements. While ensuring excellent sealing performance, it can effectively ensure that the laser absorbs the trace nitrogen leaked from the catheter joint. The basic principle of laser acquisition involved in the present invention can be found in Figure 3 .

[0053] 3.4 Structural design of detachable optical sealing device

[0054] The device mainly includes a detachable sealing shell, an airtight sealing strip, a spherical reflector, a device bracket, and an adjustable variable diameter sealing cover. The above components ensure the sealing and stability of the detachable optical sealing device. In view of the diversity of aircraft system duct sizes, the adjustable variable diameter sealing cover is designed to support the test of system ducts with an outer diameter of up to 150mm. Considering the disassembly frequency and operation convenience of the operator during the test, the split housing is designed as eight detachable split structures to achieve rapid disassembly and assembly of the test device.

[0055] 3.5 Automatic control design of airtight detection method

[0056] The control of all electrical components of the corresponding detection device of the present invention and the collection and feedback of corresponding data are all controlled by the PLC unit. The automatic control is composed of the PLC unit and the interface. The core of the control unit is the system software loaded inside the PLC. The core control software is designed using mainstream PLC programming software. The entire program mainly includes: system initial control, photoelectric signal acquisition program, filter signal processing program, temperature control and electrical control program, etc. Through modular design programming, it is easy to debug and maintain the system, realize rapid diagnosis of its own software and hardware, implement monitoring of program operation, and automatically reset after the system issues an alarm. Figure 4 PLC software control process for airtight system.

Claims

1. A method for checking the air tightness of an aircraft duct joint, characterized in that: Here are the steps: Step 1: Check the test device before operation to ensure the cleanliness of the inside and outside of the test device, the pipelines and the outside of the functional accessories; verify whether the pressure gauge is within the regular inspection period; confirm that the display screen on the test device is in good condition; confirm that the power supply circuit and the airtight sealing strip (2) are within the validity period; whether the airtight sealing strip (2) is in good condition and should not be damaged by aging or cracking; check whether the spherical reflector (3) is intact and has no scratches or cracks; Step 2: Before starting the test device, connect one end of the grounding wire to the test device and the other end to the grounding stake; check that the power supply of the device is in the off state; Step 3: According to the aircraft test requirements, the pipe joint to be tested is placed into the detachable sealing housing (1), and after adjusting the pipeline posture, the detachable sealing housing (1) is spliced, and the adjustable variable diameter sealing cover (4) is adjusted according to the diameter of the catheter to ensure the sealing of the device; Step 4: Connect the laser emitter (13) and the optical sensor (14) equipped in the airtight inspection device to the detachable optical sealing device through the device interface (5), and use the device bracket (8) to ensure the stability of the optical sealing device; Step 5: Start the computer (9), use the computer (9) to send a command to the PLC control unit (10) to initialize the system of the inspection device, and the PLC control unit (10) tests the device circuit. If a circuit fault occurs, after manual troubleshooting, the PLC control unit (10) retests the device circuit. After no circuit fault occurs, the test is started. During the test, the reading of the gas pressure gauge (6) is observed. If the pressure in the device exceeds the warning limit, the exhaust valve (7) is immediately opened to reduce the pressure in the device to a safe range. Step 6: Send a command to the PLC control unit (10) through the computer (9), adjust the electric control device (11) and the temperature control device (12), control the laser transmitter (13) to emit an infrared laser with a wavelength that meets the test requirements, receive the laser signal emitted from the optical sealing device through the optical sensor (14), convert the optical signal into an electrical signal through the signal processor (15), use the frequency modulation amplifier (16) to modulate the wavelength and reduce the influence of the mixed frequency noise, and finally return the signal to the computer (9) for analysis and processing, and judge whether the air tightness of the aircraft duct joint is good through the display screen of the computer (9). If there is a problem with the air tightness, the exhaust valve (7) should be opened to release the pressure in the device, disassemble the device for troubleshooting, and re-test until the air tightness of the joint is good; Step 7: After the test is completed, the exhaust valve (7) is opened to complete the pressure relief work and disassemble the device. The PLC control unit (10) is controlled by the computer (9) to turn off the electric control device (11) and the temperature control device (12). After confirming that the device is in the off state, the laser emitter (13) and the optical sensor (14) are disconnected from the detachable optical sealing device; Step 8: disconnect the grounding wire from the test bench and the test site grounding piles, and recycle all external devices into the storage box (19); clean the operation panel and outer surface of the airtight inspection device.

2. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 1, characterized in that: The test device comprises a data acquisition part and a data analysis part; The data acquisition part comprises a detachable sealing housing (1), an airtight sealing strip (2), a spherical reflector (3), an adjustable variable diameter sealing cover (4), an equipment interface (5), a gas pressure gauge (6), an exhaust valve (7) and a device bracket (8); The detachable sealed housing (1) comprises eight detachable split structures, which are designed to be split and spliced; the airtight sealing strip (2) is a rectangular cross-section adhesive sealing strip, which is used to ensure the sealing of the gap between the spliced ​​housings; The spherical reflector (3) is located in the optical sealing device, wherein two mirror surfaces are installed at one end of the device and another larger mirror surface is installed at the other end. The laser is reflected multiple times by the reflector to achieve optical path adjustment, so as to ensure the accuracy of nitrogen concentration parameter collection; The data analysis part includes a computer (9), a PLC control unit (10), an electric control device (11), a temperature control device (12), a laser transmitter (13), an optical sensor (14), a signal processor (15), a frequency modulation amplifier (16), a device housing (17), moving wheels (18) and a storage box (19); The computer (9) communicates with the PLC control unit (10) through the core control software, sends out system operation signals, and receives collected data signals for analysis; The PLC control unit (10) receives the communication command of the computer through the external interface provided by the PLC, performs logic operation and outputs the control signal to control the operation of each electronic device; The electric control device (11) is used to output a stable current source to provide an operating current to the laser emitter (13).

3. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The temperature control device (12) controls the working temperature of the laser emitter (13) so that the laser emitter (13) stably outputs laser light of a certain wavelength.

4. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The laser emitter (13) is used to output infrared laser with a wavelength of 2700nm to ensure the absorption of nitrogen concentration.

5. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The optical sensor (14) is used to collect infrared laser light emitted after being reflected in the optical sealing device.

6. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The signal processor (15) is used to convert the optical signal into an electrical signal.

7. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The adjustable variable diameter sealing cover (4) realizes the inspection of multiple diameter catheters with a maximum diameter of 150 mm through a flexible adjustment interface, and ensures the overall sealing performance of the optical sealing device through the contraction of the flexible cover.

8. A method for checking the air tightness of an aircraft conduit joint as claimed in claim 2, characterized in that: The device interface (5) is used to connect the laser emitter (13) and the optical sensor (14) with the optical sealing device. A sealing strip is bonded at the connection with the electrical components inside the device to ensure the overall sealing of the optical sealing device.

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