A nondestructive testing device and method for inner wall of large underwater pipeline

Abstract

The present invention provides a nondestructive testing device and method for the inner wall of a large underwater pipeline, which includes a main body for carrying the entire device; the main body is equipped with supporting and fixing legs for supporting it on the inner wall of the pipeline and cooperating with the main body to achieve walking inside the pipeline; the main body is equipped with a nondestructive testing bracket device for detecting the inner wall of the pipeline; the main body is equipped with a plurality of power fans for driving the entire detection device to achieve underwater sinking, floating, forward, backward, steering and balancing functions; the main body and the supporting and fixing legs are connected to a hydraulic control system for controlling their movements; the main body is equipped with a visual camera for providing visual inspection images and videos of the inner wall of the pipeline. It is used to solve the problems of difficult nondestructive testing of the inner wall of large underwater pipelines and poor flexibility of the detection device, and improve the efficiency of visual and ultrasonic nondestructive testing of the inner wall of the pipeline.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline detection, and in particular relates to a device and method for nondestructive detection of the inner wall of a large underwater pipeline. Background Art

[0002] With the continuous development of modern industry, the construction of underwater facilities has become an important part of infrastructure. Due to the particularity of the underwater environment and the superiority of non-destructive testing, non-destructive testing has become an indispensable means in the process of industrial development and underwater equipment and facility testing. In terms of underwater pipeline equipment, it reflects a country's modern industrial level to a certain extent. Effective non-destructive testing evaluation and convenient non-destructive testing devices can greatly improve the efficiency of pipeline inspection, ensure the safe and stable operation of pipeline equipment, and bring better economic and social benefits to enterprises.

[0003] At present, the inspection of large underwater pipelines mainly uses large inspection equipment carrying various inspection tools to inspect different parts. This has high manufacturing costs, requires a large area, requires a large number of operators, and has high risks in equipment operation and installation.

[0004] Patent "CN 207882220 U A Reactor Pressure Vessel Pipeline Ultrasonic Inspection Device" uses a suction cup device and a cylinder leg to achieve fixed support for the device, and uses a rotating body and a circular motion component to achieve an annular scanning of the pipeline. However, the ultrasonic inspection device described in the application lacks a power system, and the positioning and adjustment of the device are difficult to achieve. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a nondestructive testing device for the inner wall of a large underwater pipeline, which is used to solve the problems of difficult nondestructive testing of the inner wall of a large underwater pipeline and poor flexibility of the testing device, and to improve the efficiency of visual and ultrasonic nondestructive testing of the inner wall of the pipeline.

[0006] In order to realize the above technical features, the object of the present invention is achieved as follows: a nondestructive testing device for the inner wall of a large underwater pipeline, which includes a main body trunk for carrying the entire device;

[0007] The main body is provided with supporting and fixing legs for supporting it on the inner wall of the pipeline and cooperating with the main body to achieve walking inside the pipeline;

[0008] A non-destructive testing bracket device for testing the inner wall of the pipeline is installed on the main body trunk;

[0009] The main body is equipped with a plurality of power fans for driving the entire detection device to realize underwater sinking, floating, forward, backward, turning and balancing functions;

[0010] The main body trunk and the supporting fixed legs are connected to a hydraulic control system for controlling their movements;

[0011] The main body is equipped with a visual camera for providing visual inspection images and videos of the inner wall of the pipeline.

[0012] The main trunk includes a main cylinder body; a main piston rod is installed inside the main cylinder body, and the two form a piston cooperation and realize the telescopic function of the main trunk;

[0013] Also included is a driving gear for driving the nondestructive testing bracket device to achieve rotation;

[0014] The driving gear includes a steering gear, which is fixedly mounted on the main cylinder body through a steering gear bracket. The output shaft of the steering gear is equipped with a driving bevel gear, which meshes and drives with a driven bevel gear mounted on the non-destructive testing bracket device, and drives the entire non-destructive testing bracket device to realize rotating annular scanning.

[0015] The supporting fixed legs include a plurality of first telescopic legs and a second telescopic legs; the cylinder bases of the plurality of first telescopic legs are evenly fixed on the outer wall of the main cylinder body of the main body; the cylinder bases of the plurality of second telescopic legs are evenly fixed on the outer wall of the end of the main piston rod of the main body;

[0016] The first telescopic leg and the second telescopic leg are both equipped with pressure sensors for monitoring the rod cavity pressure, and ensure that when the first telescopic leg and the second telescopic leg are extended to their full length, the rod cavity pressure increases until it reaches a preset value, and the compression signal of the pressure sensor is triggered, causing the hydraulic control system to shut down and maintain pressure.

[0017] It also includes a third telescopic leg, the cylinder base of the third telescopic leg is rotatably mounted on the main piston rod through a connecting sleeve, and the telescopic end of the third telescopic leg is connected to the non-destructive testing bracket device;

[0018] The connecting sleeve is used for mounting the driven bevel gear, and is meshed with the driving bevel gear of the driving gear for transmission.

[0019] There are eight groups of power fans, two of which are arranged at the head and tail of the main body respectively; three of which are evenly distributed on the outer wall of the main cylinder body of the main body; and the other three are evenly distributed on the outer wall of the main piston rod of the main body; the entire nondestructive testing device is transported to the working point to be tested by controlling the eight groups of power fans.

[0020] The nondestructive testing bracket device includes a flexible bracket connected to the end of the third telescopic leg supporting the fixed leg, and multiple groups of ultrasonic nondestructive testing universal trays that can adaptively fit the surface to be tested are installed on the flexible bracket.

[0021] The flexible bracket is made of flexible material and can be closely fitted to inspected work surfaces of different shapes;

[0022] The ultrasonic non-destructive testing universal pallet includes a pallet outer bracket, a universal rotator rotatably matched with the pallet outer bracket, an ultrasonic testing probe embedded and fixed on the top of the universal rotator, and a reset spring for automatically resetting the universal rotator after rotation.

[0023] The hydraulic control system includes a flow direction control cartridge valve, a relief valve, a first directional control solenoid valve, a first manual control valve, a second directional control solenoid valve, a second manual control valve, a first telescopic leg hydraulic control subsystem of a main cylinder body supporting a fixed main body trunk, a second telescopic leg hydraulic control subsystem of a main piston rod supporting a fixed main body trunk, a main body trunk hydraulic control subsystem for driving the main cylinder body to telescope, and a third telescopic leg detection mechanism hydraulic control subsystem for driving a non-destructive detection bracket device.

[0024] The flow direction control cartridge valve is powered off and closed, and the pressure oil flows to the left path, and the relief valve is used for pressure stabilization protection; the cartridge valve is powered on and opened, and there is pressure oil in both the left and right paths, and the pressure stabilization protection function of the relief valve continues to be effective;

[0025] When the first direction control solenoid valve is powered, the second telescopic leg moves; when the first direction control solenoid valve is powered off, the first telescopic leg moves; the first manual control valve serves as a backup for the failure of the first direction control solenoid valve;

[0026] When the second direction control solenoid valve is energized, the third telescopic leg is activated; when the second direction control solenoid valve is de-energized, the main cylinder is activated; the second manual control valve serves as a failure standby for the second direction control solenoid valve.

[0027] Each group of corresponding first telescopic leg hydraulic control subsystem, second telescopic leg hydraulic control subsystem, main trunk hydraulic control subsystem and detection mechanism hydraulic control subsystem respectively realizes the telescopic control function of the corresponding first telescopic leg, second telescopic leg, third telescopic leg and main cylinder body through a three-position four-way solenoid reversing valve; a manual three-position four-way reversing valve is connected in parallel with the three-position four-way solenoid reversing valve as a redundant protection in case of failure of the three-position four-way solenoid reversing valve, and two overflow valves are connected in parallel with the three-position four-way solenoid reversing valve to realize the voltage stabilizing protection function of the corresponding telescopic leg hydraulic control subsystem, and a one-way valve is connected in series with the three-position four-way solenoid reversing valve to prevent the hydraulic oil from flowing back and unloading, and two one-way throttle valves are connected in series with the three-position four-way solenoid reversing valve to control the flow rate of the hydraulic control circuit.

[0028] The method for nondestructive testing of the inner wall of a large underwater pipeline using a detection device comprises the following steps:

[0029] Step 1: Place the entire detection device in the water area to be detected, and then control multiple power fans to transport the entire detection device to the working point to be detected;

[0030] Step 2: After the device to be inspected enters the pipeline to be inspected, the supporting fixed legs are controlled by the hydraulic control system to position the entire inspection device inside the pipeline;

[0031] Step three, by controlling the second telescopic leg, the nondestructive testing bracket device is extended, and the nondestructive testing bracket device is turned on, and the inner wall of the pipeline is subjected to ultrasonic nondestructive testing by the nondestructive testing bracket device; during the testing process, the nondestructive testing bracket device is synchronously driven by the active gear to rotate along the inner wall of the pipeline, thereby realizing annular testing;

[0032] Step 4: Provide visual inspection images and videos of the inner wall of the pipeline through a visual camera;

[0033] Step 5: After a circumferential length test is completed, the main body is controlled to be extended and retracted through the hydraulic control system, and the non-destructive testing bracket device is moved forward inside the pipeline with the help of the supporting fixed legs;

[0034] Step 6, controlling the nondestructive testing bracket device again to test the next circumferential testing part;

[0035] Step 7: Repeat steps 5 to 6 until the entire pipeline has been inspected.

[0036] The present invention has the following beneficial effects:

[0037] 1. By adopting the nondestructive testing device for the inner wall of a large underwater pipeline of the present invention, it can be used to solve the problems of difficulty in nondestructive testing the inner wall of a large underwater pipeline and poor flexibility of the testing device, and improve the efficiency of visual and ultrasonic nondestructive testing of the inner wall of the pipeline.

[0038] 2. The entire detection device can sink, float, move forward, move backward, turn and balance through eight power and balancing fans. The device can be fixed through two sets of hydraulic support legs. The flexible detection tray and universal rotating probe can be used to make the ultrasonic probe fit closely with the inspected plane. The four hydraulic air separation systems can realize the telescopic function of each hydraulic cylinder of the device, so as to flexibly and safely realize the movement, support balance and dynamic detection functions of the detection device.

[0039] 3. Each hydraulic control subsystem realizes the cylinder extension and retraction function through a three-position four-way solenoid reversing valve, and connects a manual three-position four-way reversing valve in parallel as a redundant protection in case of failure of the three-position four-way solenoid reversing valve. Two overflow valves are connected in parallel to realize the pressure stabilization protection function of the hydraulic control subsystem. A one-way valve is connected in series to prevent the hydraulic oil from flowing back and unloading, and two one-way throttle valves are connected in series to control the flow of the hydraulic control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] Figure 1 Three-dimensional diagram of the overall structure of the present invention.

[0042] Figure 2 The front view of the overall structure of the present invention.

[0043] Figure 3 The overall structure of the present invention is shown in the right side view.

[0044] Figure 4 It is a cross-sectional view of the ultrasonic nondestructive testing universal tray of the present invention.

[0045] Figure 5 It is a three-dimensional diagram of the ultrasonic non-destructive testing of the universal tray of the present invention.

[0046] Figure 6 This is a diagram of the hydraulic control system of the present invention.

[0047] In the figure: main body 1, supporting fixed legs 2, non-destructive testing bracket device 3, hydraulic control system 4, pressure sensor 5, power and balancing fan 6, visual camera 7;

[0048] Main cylinder 101, main piston rod 102, driving gear 103;

[0049] A first telescopic leg 201, a second telescopic leg 202, and a third telescopic leg 203;

[0050] Flexible bracket 301, ultrasonic non-destructive testing universal tray 302;

[0051] The tray outer bracket 302-1 is embedded and fixed on the universal rotating body 302-2, the ultrasonic detection probe 302-3, and the return spring 302-4;

[0052] Liquid flow direction control cartridge valve 401, relief valve 402, first direction control solenoid valve 403, first manual control valve 404, second direction control solenoid valve 433, second manual control valve 434;

[0053] Three-position four-way solenoid reversing valves 405, 416, 423, 432;

[0054] Manual three-position four-way reversing valves 406, 415, 422, 429;

[0055] Relief valves 407 / 411, 414 / 417, 421 / 424, 428 / 431;

[0056] Check valves 408, 413, 420, 427;

[0057] One-way throttle valves 409 / 410, 412 / 418, 419 / 425, 426 / 430. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0059] Embodiment 1:

[0060] See also Figure 1-6 , a nondestructive testing device for the inner wall of a large underwater pipeline, which includes a main body 1 for carrying the entire device; the main body 1 is equipped with a supporting and fixing leg 2 for supporting it on the inner wall of the pipeline and cooperating with the main body 1 to realize walking inside the pipeline; the main body 1 is equipped with a nondestructive testing bracket device 3 for realizing the detection of the inner wall of the pipeline; the main body 1 is equipped with a plurality of power fans 6 for driving the entire detection device to realize underwater sinking, floating, forward, backward, steering and balancing functions; the main body 1 and the supporting and fixing leg 2 are connected to a hydraulic control system 4 for controlling their actions; the main body 1 is equipped with a visual camera 7 for providing visual inspection images and videos of the inner wall of the pipeline. By adopting the above-mentioned nondestructive testing device, nondestructive testing of the inner wall of the pipeline can be realized. In the specific detection process, the main body 1 can move and walk on the inner wall of the pipeline, the supporting and fixing leg 2 can support the entire main body 1 inside the pipeline, and the power fan 6 can realize the movement and walking of the entire detection device.

[0061] Furthermore, the main trunk 1 includes a main cylinder 101; a main piston rod 102 is installed inside the main cylinder 101, and the two form a piston cooperation and realize the telescopic function of the main trunk 1; it also includes a driving gear 103 for driving the non-destructive testing bracket device 3 to realize rotation; the driving gear 103 includes a steering gear, which is fixedly installed on the main cylinder 101 through a steering gear bracket, and the output shaft of the steering gear is installed with a driving bevel gear, which is meshed with the driven bevel gear installed on the non-destructive testing bracket device 3 for transmission, and drives the entire non-destructive testing bracket device 3 to realize rotating circular scanning. The main trunk 1 mentioned above is mainly used to realize the movement of the entire detection device. During the working process, the extension of the main piston rod 102 is controlled to realize the extension of the entire main trunk 1 inside the pipeline.

[0062] Furthermore, the supporting and fixing legs 2 include a plurality of first telescopic legs 201 and a second telescopic leg 202; the cylinder bases of the plurality of first telescopic legs 201 are evenly fixed on the outer wall of the main cylinder 101 of the main trunk 1; the cylinder bases of the plurality of second telescopic legs 202 are evenly fixed on the outer wall of the end of the main piston rod 102 of the main trunk 1. The above-mentioned plurality of supporting and fixing legs 2 are used to fix the entire detection device inside the pipeline on the one hand, and can cooperate with the main piston rod 102 to realize the movement of the detection device inside the pipeline on the other hand.

[0063] Furthermore, the first telescopic leg 201 and the second telescopic leg 202 are both equipped with a pressure sensor 5 for monitoring the pressure in the rod cavity, and when the first telescopic leg 201 and the second telescopic leg 202 are fully extended, the pressure in the rod cavity increases until it reaches a preset value, and the compression signal of the pressure sensor 5 is triggered, so that the hydraulic control system 4 stops and maintains pressure. The above-mentioned pressure sensor 5 facilitates the automatic extension and retraction control of the telescopic leg, thereby realizing the full automation of the entire detection process, thereby improving the degree of automation.

[0064] Furthermore, it also includes a third telescopic leg 203, the cylinder base of the third telescopic leg 203 is rotatably mounted on the main piston rod 102 through a connecting sleeve, and the telescopic end of the third telescopic leg 203 is connected to the non-destructive testing bracket device 3; the connecting sleeve is used to install a driven bevel gear, which is meshed with the driving bevel gear of the driving gear 103. The above-mentioned driving gear 103 can be used to drive the non-destructive testing bracket device 3 to realize rotational movement inside the pipeline, thereby realizing circumferential detection of the inner wall of the pipeline.

[0065] Furthermore, there are eight groups of power fans 6, two of which are arranged at the head and tail of the main body 1 respectively; three of which are evenly arranged on the outer wall of the main cylinder 101 of the main body 1; and the other three are evenly arranged on the outer wall of the main piston rod 102 of the main body 1; the entire nondestructive testing device is transported to the working point to be tested by controlling the eight groups of power fans 6. The above-mentioned power fans 6 provide the entire testing device with underwater movement.

[0066] Furthermore, the nondestructive testing bracket device 3 includes a flexible bracket 301 connected to the end of the third telescopic leg 203 supporting the fixed leg 2, and multiple groups of ultrasonic nondestructive testing universal trays 302 that can adaptively fit the surface to be tested are installed on the flexible bracket 301. The nondestructive testing bracket device 3 can realize nondestructive testing of the inner wall of the pipeline.

[0067] Furthermore, the flexible bracket 301 is made of flexible material and can be closely fitted to the inspected working surface of different shapes; the ultrasonic non-destructive testing universal tray 302 includes a tray outer bracket 302-1, a universal rotating body 302-2 that rotates with the tray outer bracket 302-1, an ultrasonic detection probe 302-3 embedded and fixed on the top of the universal rotating body 302-2, and a reset spring 302-4 that automatically resets the universal rotating body 302-2 after rotation. The ultrasonic non-destructive testing universal tray 302 can effectively fit the inner wall of different pipes and ensure the detection quality.

[0068] Further, the hydraulic control system 4 includes a flow direction control cartridge valve 401, a relief valve 402, a first direction control solenoid valve 403, a first manual control valve 404, a second direction control solenoid valve 433, a second manual control valve 434, a first telescopic leg hydraulic control subsystem I for supporting the main cylinder 101 of the fixed main body trunk 1, a second telescopic leg hydraulic control subsystem II for supporting the main piston rod 102 of the fixed main body trunk 1, a main body trunk hydraulic control subsystem III for driving the main cylinder 101 to telescope, and a detection mechanism hydraulic control subsystem IV for driving the third telescopic leg 203 of the non-destructive detection bracket device 3. By adopting the above-mentioned hydraulic control system 4, it is possible to realize full automatic control of the entire detection device.

[0069] Furthermore, the flow direction control cartridge valve 401 is powered off and closed, at which time the pressure oil flows to the left path, and the overflow valve 402 is used for voltage stabilization protection; the cartridge valve 401 is powered on and opened, at which time there is pressure oil in both the left and right paths, and the voltage stabilization protection function of the overflow valve 402 continues to be effective; the first direction control solenoid valve 403 is powered on, and the second telescopic leg 202 is actuated; the first direction control solenoid valve 403 is powered off, and the first telescopic leg 201 is actuated; the first manual control valve 404 serves as a fault standby for the first direction control solenoid valve 403; the second direction control solenoid valve 433 is powered on, and the third telescopic leg 203 is actuated; the second direction control solenoid valve 433 is powered off, and the main cylinder body 101 is actuated; the second manual control valve 434 serves as a fault standby for the second direction control solenoid valve 433.

[0070] Furthermore, each corresponding first telescopic leg hydraulic control subsystem I, second telescopic leg hydraulic control subsystem II, main body trunk hydraulic control subsystem III and detection mechanism hydraulic control subsystem IV respectively realizes the telescopic control function of the corresponding first telescopic leg 201, second telescopic leg 202, third telescopic leg 203 and main cylinder 101 through a three-position four-way solenoid reversing valve 405, 416, 423, 432; and a manual three-position four-way reversing valve 405, 416, 423, 432 is respectively connected in parallel with the three-position four-way solenoid reversing valve 405, 416, 423, 432. 06, 415, 422, 429 serve as redundant protection in case of failure of the three-position four-way solenoid reversing valve. Two overflow valves 407 / 411, 414 / 417, 421 / 424, 428 / 431 are respectively connected in parallel with them to realize the voltage stabilizing protection function of the corresponding telescopic leg hydraulic control subsystem. A one-way valve 408, 413, 420, 427 is respectively connected in series with them to prevent the hydraulic oil from flowing back and unloading. Two one-way throttle valves 409 / 410, 412 / 418, 419 / 425, 426 / 430 are respectively connected in series with them to control the flow of the hydraulic control circuit.

[0071] Embodiment 2:

[0072] The method for nondestructive testing of the inner wall of a large underwater pipeline using a detection device comprises the following steps:

[0073] Step 1: Place the entire detection device in the water area to be detected, and then control multiple power fans 6 to transport the entire detection device to the working point to be detected;

[0074] Step 2: After the device to be inspected enters the interior of the pipeline to be inspected, the supporting fixed legs 2 are controlled by the hydraulic control system 4, thereby positioning the entire inspection device inside the pipeline;

[0075] Step 3: by controlling the second telescopic leg 202, the nondestructive testing bracket device 3 is extended and opened, and the inner wall of the pipeline is subjected to ultrasonic nondestructive testing through the nondestructive testing bracket device 3; during the testing process, the nondestructive testing bracket device 3 is synchronously driven by the active gear 103 to rotate along the inner wall of the pipeline, thereby realizing annular testing;

[0076] Step 4, providing visual inspection images and videos of the inner wall of the pipeline through the visual camera 7;

[0077] Step 5: After a circumferential length test is completed, the main body 1 is controlled to be extended and retracted by the hydraulic control system 4, and the non-destructive testing bracket device 3 is moved forward inside the pipeline by means of the supporting fixed legs 2;

[0078] Step 6, controlling the nondestructive testing bracket device 3 again to test the next circumferential testing position;

[0079] Step 7: Repeat steps 5 to 6 until the entire pipeline has been inspected.

Claims

1. A nondestructive testing device for the inner wall of a large underwater pipeline, characterized in that: It includes a main body trunk (1) for carrying the entire device; The main body trunk (1) is provided with supporting fixed legs (2) for supporting it on the inner wall of the pipeline and cooperating with the main body trunk (1) to achieve walking inside the pipeline; The main body (1) is provided with a non-destructive testing bracket device (3) for testing the inner wall of the pipeline; The main body (1) is equipped with a plurality of power fans (6) for driving the entire detection device to achieve underwater sinking, floating, forward movement, backward movement, steering and balancing functions; The main body trunk (1) and the supporting fixed legs (2) are connected to a hydraulic control system (4) for controlling their movements; The main body (1) is equipped with a visual camera (7) for providing images and videos of visual inspection of the inner wall of the pipeline; The supporting fixed legs (2) comprise a plurality of first telescopic legs (201) and a second telescopic leg (202); the cylinder bases of the plurality of first telescopic legs (201) are evenly fixed on the outer wall of the main cylinder (101) of the main trunk (1); the cylinder bases of the plurality of second telescopic legs (202) are evenly fixed on the outer wall of the end of the main piston rod (102) of the main trunk (1); The first telescopic leg (201) and the second telescopic leg (202) are both equipped with a pressure sensor (5) for monitoring the pressure in the rod cavity, and ensure that when the first telescopic leg (201) and the second telescopic leg (202) are fully extended, the pressure in the rod cavity increases until it reaches a preset value, and a compression signal from the pressure sensor (5) is triggered, causing the hydraulic control system (4) to shut down and maintain pressure; It also comprises a third telescopic leg (203), the cylinder base of the third telescopic leg (203) being rotatably mounted on the main piston rod (102) via a connecting sleeve, and the telescopic end of the third telescopic leg (203) being connected to the non-destructive testing bracket device (3); The connecting sleeve is used to mount the driven bevel gear, and is meshed with the driving bevel gear of the driving gear (103) for transmission.

2. According to claim 1, a nondestructive testing device for the inner wall of a large underwater pipeline is characterized in that: The main body (1) comprises a main cylinder (101); a main piston rod (102) is installed inside the main cylinder (101), and the two form a piston cooperation and realize the telescopic function of the main body (1); It also includes a driving gear (103) for driving the non-destructive testing bracket device (3) to rotate; The driving gear (103) comprises a steering gear, which is fixedly mounted on the main cylinder body (101) via a steering gear bracket, and an output shaft of the steering gear is mounted with a driving bevel gear, which meshes with a driven bevel gear mounted on the non-destructive testing bracket device (3) to drive the entire non-destructive testing bracket device (3) to achieve a rotating annular scanning.

3. According to claim 1, a nondestructive testing device for the inner wall of a large underwater pipeline is characterized in that: There are eight groups of power fans (6), two of which are arranged at the head and tail of the main body trunk (1), three of which are evenly distributed on the outer wall of the main cylinder body (101) of the main body trunk (1), and the other three of which are evenly distributed on the outer wall of the main piston rod (102) of the main body trunk (1). The entire nondestructive testing device is transported to a working point to be tested by controlling the eight groups of power fans (6).

4. The nondestructive testing device for the inner wall of a large underwater pipeline according to claim 1, characterized in that: The nondestructive testing bracket device (3) comprises a flexible bracket (301) connected to the end of a third telescopic leg (203) supporting the fixed leg (2), and a plurality of groups of ultrasonic nondestructive testing universal trays (302) capable of adaptively fitting with a surface to be tested are mounted on the flexible bracket (301).

5. According to claim 4, a nondestructive testing device for the inner wall of a large underwater pipeline is characterized in that: The flexible support (301) is made of a flexible material and is capable of closely fitting to inspected working surfaces of different shapes; The ultrasonic non-destructive testing universal pallet (302) comprises a pallet outer bracket (302-1), a universal rotating body (302-2) rotatably matched with the pallet outer bracket (302-1), an ultrasonic testing probe (302-3) embedded and fixed on the top of the universal rotating body (302-2), and a reset spring (302-4) for achieving automatic reset of the universal rotating body (302-2) after rotation.

6. The nondestructive testing device for the inner wall of a large underwater pipeline according to claim 1, characterized in that: The hydraulic control system (4) comprises a flow direction control cartridge valve (401), a relief valve (402), a first direction control solenoid valve (403), a first manual control valve (404), a second direction control solenoid valve (433), a second manual control valve (434), a first telescopic leg hydraulic control subsystem (I) of a main cylinder (101) supporting a fixed main body trunk (1), a second telescopic leg hydraulic control subsystem (II) of a main piston rod (102) supporting a fixed main body trunk (1), a main body trunk hydraulic control subsystem (III) for driving the main cylinder (101) to telescope, and a detection mechanism hydraulic control subsystem (IV) for driving a third telescopic leg (203) of a non-destructive detection bracket device (3).

7. The nondestructive testing device for the inner wall of a large underwater pipeline according to claim 6, characterized in that: The flow direction control cartridge valve (401) is powered off and closed, and the pressure oil flows to the left path, and the overflow valve (402) is used for pressure stabilization protection; the cartridge valve (401) is powered on and opened, and pressure oil flows to both the left and right paths, and the pressure stabilization protection function of the overflow valve (402) remains effective; When the first direction control solenoid valve (403) is energized, the second telescopic leg (202) is activated; when the first direction control solenoid valve (403) is de-energized, the first telescopic leg (201) is activated; the first manual control valve (404) serves as a backup in case of failure of the first direction control solenoid valve (403); When the second directional control solenoid valve (433) is energized, the third telescopic leg (203) is activated; when the second directional control solenoid valve (433) is de-energized, the main cylinder (101) is activated; and the second manual control valve (434) serves as a backup valve in case of failure of the second directional control solenoid valve (433).

8. The nondestructive testing device for the inner wall of a large underwater pipeline according to claim 7, characterized in that: Each corresponding first telescopic leg hydraulic control subsystem (I), second telescopic leg hydraulic control subsystem (II), main body trunk hydraulic control subsystem (III) and detection mechanism hydraulic control subsystem (IV) respectively realizes the telescopic control function of the corresponding first telescopic leg (201), second telescopic leg (202), third telescopic leg (203) and main cylinder body (101) through a three-position four-way electromagnetic reversing valve (405), (416), (423) and (432); and a manual three-position four-way reversing valve (406), (415) and (432) are respectively connected in parallel with the three-position four-way electromagnetic reversing valve (405), (416), (423) and (432). (422) and (429) serve as redundant protection in case of failure of the three-position four-way solenoid reversing valve. Two overflow valves (407) / (411), (414) / (417), (421) / (424), (428) / (431) are respectively connected in parallel with them to realize the voltage stabilizing protection function of the corresponding telescopic leg hydraulic control subsystem. A one-way valve (408), (413), (420), (427) is respectively connected in series with them to prevent the hydraulic oil from flowing back and unloading. Two one-way throttle valves (409) / (410), (412) / (418), (419) / (425), (426) / (430) are respectively connected in series with them to control the flow of the hydraulic control circuit.

9. A method for nondestructive testing of the inner wall of a large underwater pipeline using the detection device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: placing the entire detection device in the water area to be detected, and then controlling a plurality of power fans (6) to transport the entire detection device to the working point to be detected; Step 2: After the device to be inspected enters the interior of the pipeline to be inspected, the supporting fixed legs (2) are controlled by the hydraulic control system (4), thereby positioning the entire inspection device inside the pipeline; Step three, by controlling the second telescopic leg (202), the non-destructive testing bracket device (3) is extended, and the non-destructive testing bracket device (3) is turned on, and the inner wall of the pipeline is subjected to ultrasonic non-destructive testing by the non-destructive testing bracket device (3); during the testing process, the non-destructive testing bracket device (3) is synchronously driven by the active gear (103) to rotate along the inner wall of the pipeline, thereby achieving an annular testing; Step 4, providing visual inspection images and videos of the inner wall of the pipeline through a visual camera (7); Step 5: After a circumferential length test is completed, the main body (1) is controlled to be extended and retracted by means of the hydraulic control system (4), and the non-destructive testing bracket device (3) is moved forward inside the pipeline by means of the supporting fixed legs (2); Step 6, controlling the nondestructive testing bracket device (3) again to test the next circumferential testing position; Step 7: Repeat steps 5 to 6 until the entire pipeline has been inspected.

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