In-service Christmas tree valve rod defect detection method and system

Abstract

The invention discloses an in-service Christmas tree valve rod defect detection method and system, and relates to the technical field of ultrasonic detection, and the method comprises the following steps: making a valve rod simulation test piece with defect characteristics and a reference test piece without defect characteristics; performing ultrasonic phased array scanning on the comparison test piece to obtain a standard echo parameter comparison table of the disassembly state of the comparison test piece; loading the reference test piece into the gas production tree wellhead valve, and performing ultrasonic phased array scanning again to obtain a standard echo parameter comparison table of the reference test piece in a non-disassembly state; making an echo feature comparison graph; and loading the valve rod simulation test piece into a gas production tree wellhead valve, performing ultrasonic phased array scanning to obtain a structural characteristic oscillogram of the valve rod simulation test piece, and performing comparative analysis on the structural characteristic oscillogram and the echo characteristic comparison diagram. On-line detection of corrosion defects on the surface of the valve rod in the valve can be realized under the condition that the valve is not disassembled.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic detection, and in particular to a method and system for detecting defects in valve stems of in-service gas production trees. Background Art

[0002] The wellhead gas tree at the wellhead of a natural gas well is a wellhead device used for shutting in the well, adjusting pressure, gas volume, circulating well killing and other operations in the ground process of natural gas extraction. It connects the gas well oil, casing and ground process equipment and is one of the core equipment for natural gas extraction. During use, it was found that due to a small amount of corrosive media entering the upper area of ​​the gas tree valve, the upper area of ​​the valve stem that theoretically does not contact the corrosive medium has suffered relatively serious local corrosion, which seriously affects the service performance and reliability of the valve. Therefore, regular inspection and evaluation of the internal valve stem corrosion of the gas tree valve, especially the valve stem inspection and evaluation without affecting production and without disassembly, has important engineering application value.

[0003] In the non-disassembly state, the wellhead valve inlet and outlet channels and flange end faces are located outside the overall structure, so phased array detection technology can usually be used to detect corrosion defects. In addition, due to the large overall thickness of the valve body and valve plate, corrosion damage generally does not cause valve failure. However, in view of the demand for internal valve stem detection, due to the limitations of factors such as the valve stem being inside the valve, the complex internal structure of the valve, and the large thickness of the valve body, there is currently no technology that can effectively detect the internal valve stem of the valve without disassembly. For this reason, for valve stem detection, the wellhead valve is currently returned to the site and disassembled for detection, which not only affects the normal production efficiency of the oil and gas field, has a long cycle and high cost, but also cannot solve the online detection and evaluation of the in-service wellhead device from the perspective of intrinsic safety. Therefore, conducting online detection of the internal valve stem of the in-service wellhead valve is of great engineering significance to eliminate the safety hazards caused by internal valve stem defects and ensure the safety of gas well production. Summary of the invention

[0004] The present invention aims to solve the deficiencies of the prior art and to provide a method and system for detecting valve stem defects of an in-service gas tree, which can realize online detection of corrosion defects on the surface of the valve stem inside the valve without disassembling the valve.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for detecting valve stem defects of an in-service gas tree comprises the following steps:

[0007] Step 1: Prepare a valve stem simulation specimen with defect characteristics and a comparison specimen without defect characteristics;

[0008] Step 2: Performing ultrasonic phased array scanning on the comparison specimen to obtain structural echo characteristics of the comparison specimen, and obtaining a standard echo parameter comparison table of the comparison specimen in a disassembled state according to the structural echo characteristics;

[0009] Step 3: Install the comparison specimen into the wellhead valve of the gas tree, and perform ultrasonic phased array scanning again to obtain a standard echo parameter comparison table of the comparison specimen in the undisassembled state; and prepare an echo feature comparison chart according to the standard echo parameter comparison table of the comparison specimen in the disassembled state and the standard echo parameter comparison table of the comparison specimen in the undisassembled state;

[0010] Step 4: Install the valve stem simulation specimen into the wellhead valve of the gas tree, and perform ultrasonic phased array scanning to obtain a structural characteristic waveform diagram of the valve stem simulation specimen, and compare and analyze the structural characteristic waveform diagram with the echo characteristic comparison diagram.

[0011] Compared with the prior art, for valve stem detection, the wellhead valve is currently returned to the field and disassembled for detection, which not only affects the normal production efficiency of the oil and gas field, has a long cycle and high cost, but also cannot solve the problem of online detection and evaluation of the in-service wellhead device from the perspective of intrinsic safety. The present invention provides a method for detecting defects in valve stems of in-service gas trees, which can directly detect the corrosion defects hidden in the valve stems without disassembling the valve stems inside the in-service valves. In the specific scheme, firstly, it is necessary to make a corresponding valve stem simulation specimen according to the defect characteristics of the valve stem inside the wellhead valve of the gas tree, and carve artificial groove defects at the end of the valve stem and the threaded minor diameter part where corrosion is prone to occur; at the same time, a valve stem comparison specimen is made, and the comparison specimen is used to obtain the characteristic waveform diagram under the standard defect-free condition, and the comparison specimen is a valve stem specimen without artificial groove defects. The comparison specimen is subjected to ultrasonic phased array scanning, and an ultrasonic phased array device is used to emit an ultrasonic sound beam, and the end of the specimen is used as the emission position of the ultrasonic phased array probe to obtain the structural echo characteristics of the comparison specimen, and a standard echo parameter comparison table under the valve stem disassembly state is made according to the structural echo characteristics of the specimen. The comparison specimen, i.e. the defect-free valve stem specimen, is installed into the wellhead valve of the gas production tree and filled with sealing grease. An ultrasonic phased array detection device is used to emit an ultrasonic sound beam from the exposed end of the valve stem during assembly to obtain a standard echo parameter comparison table in the non-disassembly state, and the standard echo parameter feature comparison table in the disassembled state and the non-disassembly state is made into a feature comparison chart containing both states. Finally, the defect simulation specimen is installed into the wellhead valve of the gas production tree, and an ultrasonic phased array device is used to emit an ultrasonic sound beam to the exposed end of the defect simulation specimen to obtain an artificial defect and a valve stem structure feature waveform. The detection waveform of the defective specimen is compared and analyzed with the standard echo parameter comparison chart, and the difference in the analysis is the possible defect.

[0012] The above scheme aims to achieve: online detection of corrosion defects on the valve stem surface inside the valve without disassembling the valve; and to ensure that the valve stem defects can be detected while the gas tree valve is in normal service without affecting normal production efficiency, thereby eliminating safety hazards and reducing economic losses.

[0013] In a further embodiment, the defect characteristic is a groove-shaped defect.

[0014] In a further embodiment, the ultrasonic phased array scanning comprises the following steps:

[0015] Adjust the ultrasonic probe posture of the ultrasonic phased array detection equipment to ensure that the ultrasonic probe is concentric with the end of the valve stem;

[0016] Then turn on the ultrasonic phased array detection equipment, set the corresponding ultrasonic probe center frequency and number of chips, and stimulate the ultrasonic signal through the ultrasonic transducer to perform a rotating scan of the ultrasonic probe.

[0017] In a further embodiment, the rotation scanning further comprises the following steps:

[0018] In the ultrasonic phased array detection device, the deflection angle is set by adjusting the focal law, and the focal law of the end of the ultrasonic probe is adjusted in turn to each wafer module, and excited in turn;

[0019] The ultrasonic beam is deflected to the valve stem surface after being controlled by the focusing law. The ultrasonic phased array detection equipment controls the deflection angle of each chip module, and scans from small to large angles to obtain the structural information of the circumferential surface of the valve stem.

[0020] Input the actual depth of the specimen into the ultrasonic phased array instrument to obtain the propagation time required for the single excitation bottom wave signal echo;

[0021] The intermittent working time of each chip module is set to be the total time from exciting the ultrasonic sound beam to receiving the bottom wave signal once, and several chip modules are stimulated in turn to obtain a single scanning result;

[0022] Then rotate the ultrasonic probe by a certain angle and perform several scans to cover the entire circumferential surface of the valve stem, repeating the above steps for each scan; when the ultrasonic probe is rotated by a certain angle, the center of the ultrasonic probe does not deviate from the center of the valve stem, and the vertical distance between the ultrasonic probe and the valve stem remains unchanged.

[0023] In a further solution, a gap for injecting coupling agent is left between the end of the ultrasonic probe and the end of the valve stem.

[0024] A further solution is to perform a phased array probe sound velocity calibration before performing an ultrasonic phased array scan on the comparison specimen.

[0025] In a further embodiment, a valve stem defect detection system for an in-service gas tree includes an ultrasonic probe;

[0026] The ultrasonic probe comprises a probe body, a rotation positioning auxiliary tooling and a chip module. A plurality of chip modules are evenly distributed in a circumferential direction and detachably at the end of the probe body. The chip module is connected to the communication part of the probe body and is used to excite the ultrasonic phased array.

[0027] The rotation positioning auxiliary tooling is located at the center of the end of the probe body, the lower end of the rotation positioning auxiliary tooling is connected to the end of the valve stem, the upper end of the rotation positioning auxiliary tooling is rotatably connected to the probe body, and the probe body can rotate around its own axis.

[0028] In a further solution, a plurality of sockets are evenly distributed around the end of the probe body, each of the sockets has a slot, and the slot is connected to the communication part in the probe body through a communication cable;

[0029] The wafer module comprises a module housing, the upper end of which is used to be inserted into the socket, and a plug adapted to the slot is provided on the side of the upper end of the module housing facing the socket;

[0030] The lower end of the module housing is provided with a plurality of bottom wafers which are sequentially arranged along the radial direction of the probe body, and the plurality of bottom wafers are connected with the communication part in the probe body through the slots.

[0031] In a further solution, the socket is a T-shaped socket, and the upper end of the module housing is a T-shaped plug that is compatible with the T-shaped socket.

[0032] In a further solution, the rotary positioning auxiliary tooling includes a positioning pillar, the bottom of the positioning pillar is provided with a suction cup, and the positioning pillar is also rotatably sleeved with a bearing;

[0033] The axis of the probe body is provided with a through hole, the upper end of which is used to install the inserted communication part; the lower end of the through hole is provided with a bearing mounting hole for installing the bearing; the bottom of the communication part is provided with a circular hole for positioning with the upper end of the positioning pillar.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] The present invention provides a method and system for detecting defects in valve stems of in-service gas trees, which can realize online detection of corrosion defects on the surface of the valve stem inside the valve without disassembling the valve; and can ensure that the valve stem defects can be detected when the gas tree valve is in normal service without affecting normal production efficiency, thereby eliminating safety hazards and reducing economic losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0037] Figure 1 An assembly diagram of an ultrasonic probe according to an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the structure of an ultrasonic body according to an embodiment of the present invention;

[0039] Figure 3 An internal cross-sectional view of an ultrasonic body according to an embodiment of the present invention;

[0040] Figure 4 A schematic structural diagram of a wafer module according to an embodiment of the present invention;

[0041] Figure 5 A bottom schematic diagram of a wafer module according to an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the structure of a rotation positioning auxiliary tooling provided by an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of the structure of a communication part of an embodiment provided by the present invention;

[0044] Figure 8 A schematic diagram simulating the working condition of a valve stem probe inside a wellhead valve of a gas tree according to an embodiment of the present invention;

[0045] Fig. 9 A schematic structural diagram of a valve stem according to an embodiment of the present invention.

[0046] Marks and corresponding parts names in the attached drawings:

[0047] 1-ultrasonic probe, 11-probe body, 12-slot, 13-groove, 14-bearing mounting hole, 16-communication cable, 2-chip module, 22-plug, 23-module housing, 24-plug board, 25-bottom chip, 3-rotational positioning auxiliary tooling, 31-positioning pillar, 32-suction cup, 33-boss, 34-bearing, 41-main cable, 42-communication part, 43-communication head, 5-valve stem. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0049] Embodiment 1:

[0050] This embodiment 1 provides a method for detecting valve stem defects of an in-service gas tree, including the following specific steps:

[0051] Select appropriate probes and ultrasonic phased array testing instruments.

[0052] Step 1: According to the internal valve stem defect characteristics of the gas tree wellhead valve, a corresponding valve stem simulation specimen is made, and artificial groove defects are engraved at the end of the valve stem and the thread diameter part where corrosion is prone to occur. At the same time, a valve stem comparison specimen is made. The comparison specimen is used to obtain the characteristic waveform diagram under the standard defect-free condition. The comparison specimen is a valve stem specimen without an artificial groove defect.

[0053] The defect shape of the artificial defect simulation specimen in step 1 is a groove defect. The defect size parameters of two locations in the same specimen are the same. The defect size parameters are as follows:

[0054] Defective area Length(mm) Width(mm) Depth(mm) Distance from end (mm) end 10 0.5 2 160 end 10 0.5 2 180 end 10 0.5 2 200

[0055] Step 2: Perform an ultrasonic phased array scan on the comparison specimen, use an ultrasonic phased array device to emit an ultrasonic sound beam, and use the end of the specimen as the launch position of the ultrasonic phased array probe to obtain the structural echo characteristics of the comparison specimen. Based on the structural echo characteristics of the specimen, make a comparison table of standard echo parameters when the valve stem 5 is disassembled.

[0056] The specific method of using ultrasonic scanning in step 2 is as follows: First, select a suitable ultrasonic phased array detection device and choose a 64-chip special ultrasonic phased array probe. Adjust the equipment scanning form to S-type scanning. Adjust the position of ultrasonic probe 1 and ensure that the probe is concentric with the end of valve stem 5. The center position of the probe is 0.5mm away from the end of valve stem 5, and a position for coupling agent filling is reserved. Use auxiliary tooling for rotational scanning. The auxiliary tooling can ensure that the center of the probe does not deviate from the center of valve stem 5 during rotational scanning, and at the same time ensure that the vertical distance between the probe and valve stem 5 does not change. Reduce the impact of the instability of the handheld probe on the scanning results of ultrasonic phased array technology. After setting the probe position and installing the auxiliary tooling, turn on the ultrasonic phased array equipment and set the corresponding probe center frequency and number of chips. Before performing ultrasonic phased array scanning on the comparison specimen, perform the phased array probe sound velocity calibration first. Sound velocity calibration is an important step for the ultrasonic phased array to ensure the accuracy of the depth and position of the detected defects.

[0057] When using the ultrasonic phased array to detect the valve stem 5, the ultrasonic signal is first excited by the ultrasonic transducer. The ultrasonic sound beam generated after the excitation will propagate inside the valve stem 5. When the ultrasonic sound beam encounters the area where the geometric shape of the valve stem 5 changes, a reflected echo will appear. After the special ultrasonic probe receives the reflected echo, it transmits the received data to the ultrasonic phased array detection instrument. The instrument exports the data to draw the ultrasonic phased array detection map of the comparison test piece.

[0058] Step 3: Install the comparison specimen, i.e. the defect-free valve stem 5 specimen, into the wellhead valve of the gas production tree and fill it with sealing grease. Use an ultrasonic phased array detection device to emit an ultrasonic sound beam from the exposed end of the valve stem 5 during assembly. Obtain a standard echo parameter comparison table in the non-disassembly state. Make a feature comparison chart containing both states by comparing the standard echo parameter characteristics in the disassembled state and the non-disassembled state.

[0059] Step 4: Install the defect simulation specimen into the wellhead valve of the gas production tree. Use the ultrasonic phased array device to launch the ultrasonic sound beam to scan the defect simulation specimen at the exposed end to obtain the artificial defect and the valve stem 5 structural characteristic waveform. Compare and analyze the detection waveform of the defect specimen with the standard echo parameter comparison diagram. The part with difference in the analysis is the possible defect.

[0060] Embodiment 2:

[0061] like Figure 1-Figure 9 As shown, this embodiment 2 provides a system for detecting defects in a valve stem 5 of an in-service gas tree for implementing the embodiment 1, such as Figure 1-Figure 7 As shown. It includes an ultrasonic probe 1; the ultrasonic probe 1 includes a probe body 11, a rotation positioning auxiliary tool 3 and a chip module 2; a plurality of chip modules 2 are detachably distributed around the end of the probe body 11, and the chip module 2 is connected to the communication part 42 of the probe body 11 and is used to excite the ultrasonic phased array;

[0062] The rotation positioning auxiliary tooling 3 is located at the end center of the probe body 11, the lower end of the rotation positioning auxiliary tooling 3 is connected to the end of the valve stem 5, and the upper end of the rotation positioning auxiliary tooling 3 is rotatably connected to the probe body 11: the probe body 11 can rotate around its own axis.

[0063] In the above scheme, the ultrasonic probe 1 is mainly composed of three main parts, including a probe body 11, a rotation positioning auxiliary tooling 3, and a detachable chip module 2. There are six sockets evenly distributed in the annular direction at the end of the probe body 11, which are used to connect the chip module 2, and the center line of each socket is at a 60-degree angle. Each socket contains 16 symmetrical slots 12, which can be used to connect two different types of ultrasonic phased array detachable chip modules 2 with 16 chips and 8 chips. The number of slots 12 of the probe body 11 can also be increased to connect detachable chip modules 2 with 32 chips and more chips. When using linear scanning, detachable chips with 32 chips or more are selected to achieve large-area scanning. When using the focal law for multi-angle scanning, 8 chips or 16 chips are selected to ensure the superposition effect of sound waves. The detachable design of the chip allows the probe to be flexibly applied to valve stem 5 detection scenarios in different situations. The probe body 11 slot 12 is provided with a mounting buckle to ensure that the detachable chip will not fall off due to rotation during the detection process. When the ultrasonic probe 1 is used to detect the valve stem 5, the ultrasonic phased array is excited by the chip module 2, and the ultrasonic sound beam passes through the internal structure of the valve stem 5 and the defect reflection, and then is received by the chip, realizing self-emission and self-reception. The peripheral surface of the probe body is provided with a depression, that is, a groove 13, which is convenient for handheld operation.

[0064] In this embodiment, in order to realize the detachable connection of the chip module 2, the end of the probe body 11 is evenly distributed with a plurality of sockets in the circumference, each of which is provided with a slot 12, and the slot 12 is connected to the communication part 42 in the probe body 11 through a communication cable 16; the chip module 2 includes a module housing 23, the upper end of the module housing 23 is used to be inserted into the socket, and the upper end of the module housing 23 is provided with a plug 22 adapted to the slot 12 on the side facing the socket; the lower end of the module housing 23 is provided with a plurality of bottom chips 25 arranged in sequence along the radial direction of the probe body 11, and the plurality of bottom chips 25 are connected to the communication part 42 in the probe body 11 through the slot 12. In this solution, the module housing 23 of the chip module 2 is similar to the L-shaped plug 22, and the socket is an L-shaped socket adapted to the L-shaped plug 22. The inner side surface of the upper end of the module housing 23 is provided with a plug 22. The plug 22 is inserted into the slot 12 to achieve communication connection; at this time, the chip module 2 and the probe communication part 42 use different numbers of plugs 22 to connect with the bottom chip 25, and the ultrasonic phased array chip is arranged at the bottom of the module housing 23, and is arranged in sequence perpendicular to the symmetry plane. When the focusing law and other control information are communicated with the module from the probe body 11 cable through the plug 22, the bottom chip 25 excites the corresponding chip according to the received focusing law to achieve the deflection and focusing of the ultrasonic sound beam, so that the sound beam angle can be controlled, so that it can scan the circumferential surface of the valve stem 5. The number of bottom chips 25 can range from 8 to 64, and the number of chips is selected according to actual use requirements. The modules with different numbers of chips have the same overall structure and the same chip arrangement gap.

[0065] In this embodiment, in order to prevent the wafer module 2 from shaking along the axial direction of the probe body 11, the socket is a T-shaped socket, and the upper end of the module housing 23 is a T-shaped plug 22 adapted to the T-shaped socket.

[0066] In this embodiment, as a specific implementation of a rotary positioning auxiliary tooling 3, the rotary positioning auxiliary tooling 3 includes a positioning pillar 31, the bottom of the positioning pillar 31 is provided with a suction cup 32, and the positioning pillar 31 is also provided with a bearing 34 rotatably sleeved; the axis of the probe body 11 is provided with a through hole, the upper end of the through hole is used to install and insert the communication part 42; the lower end of the through hole is provided with a bearing mounting hole 14 for installing the bearing 34; the bottom of the communication part 42 is provided with a circular hole positioned with the upper end of the positioning pillar 31. In this scheme, a suction cup 32 is provided at the bottom of the positioning pillar 31, which is used to connect with the end of the valve stem 5 to ensure that the tooling will not move axially. The upper end of the suction cup 32 is a boss 33 fixed on the positioning pillar 31, the size of the boss 33 is slightly smaller than the bearing 34, and is used to resist the inner ring of the bearing 34. The bearing 34 and the positioning pillar 31 adopt an interference fit, and the bottom of the bearing 34 is in direct contact with the supporting boss 33. After the probe is pressed, the auxiliary tooling contacts the probe through the bearing 34, and when the probe rotates, the auxiliary tooling ensures that its axial position will not deviate.

[0067] Specific working principle:

[0068] First, connect the auxiliary tooling to the center position of the end of the valve stem 5 through the suction cup 32, and insert the bearing 34. Then, according to the actual length of the valve stem 5, select a detachable chip module 2 with an appropriate number of chips and connect it to the probe body 11. A total of six detachable chips are used for ultrasonic phased array scanning in one scan, and the six detachable chip modules 2 are connected to the probe body 11 to complete the probe assembly. After the probe body 11 is assembled, the probe body 11 is inserted into the auxiliary tooling through the center hole. A step with the same size as the bearing 34 is opened inside the probe body 11, and the bearing 34 is pressed through the step hole to achieve the axial positioning of the probe body 11. After the installation is completed, inject coupling agent between the probe and the upper end face of the valve stem 5, and connect the main cable 41 to the ultrasonic phased array probe device. Set the probe parameters in the ultrasonic phased array device, select the appropriate number of chips and scanning type, set the deflection angle by adjusting the focal law, and adjust the focal law of each chip module 2 in turn. The phased array chips arranged at the bottom are excited in sequence with the focusing law transmitted from the probe body 11. The ultrasonic beam is deflected to the surface of the valve stem 5 after being controlled by the focusing law. The deflection angle of each chip module 2 is controlled by the phased array instrument, and the angle is scanned from small to large to obtain the structural information of the circumferential surface of the valve stem 5. To complete a scan, the six removable chip modules 2 need to be excited in sequence, and the actual depth of the specimen is input into the ultrasonic phased array instrument to obtain the propagation time required for the single-excitation bottom wave signal echo. The intermittent working time of each chip module 2 is set to the total time from the excitation of the ultrasonic beam to the single reception of the bottom wave signal. The six chip modules 2 are excited in sequence to obtain a single scan result. Then the probe is rotated 60 degrees for a second scan to cover the entire circumferential surface of the valve stem 5. The second scan steps are the same as the first scan results.

[0069] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting valve stem defects of an in-service gas tree, characterized in that: The following steps are involved: Step 1: Prepare a valve stem simulation specimen with defect characteristics and a comparison specimen without defect characteristics; Step 2: Performing ultrasonic phased array scanning on the comparison specimen to obtain structural echo characteristics of the comparison specimen, and obtaining a standard echo parameter comparison table of the comparison specimen in a disassembled state according to the structural echo characteristics; Step 3: Install the comparison specimen into the wellhead valve of the gas tree, and perform ultrasonic phased array scanning again to obtain a standard echo parameter comparison table of the comparison specimen in the undisassembled state; and prepare an echo feature comparison chart according to the standard echo parameter comparison table of the comparison specimen in the disassembled state and the standard echo parameter comparison table of the comparison specimen in the undisassembled state; Step 4: Install the valve stem simulation specimen into the wellhead valve of the gas tree, and perform ultrasonic phased array scanning to obtain a structural characteristic waveform diagram of the valve stem simulation specimen, and compare and analyze the structural characteristic waveform diagram with the echo characteristic comparison diagram.

2. The method for detecting valve stem defects of an in-service gas tree according to claim 1, characterized in that: The defect characteristic is a groove-type defect.

3. The method for detecting valve stem defects of an in-service gas tree according to claim 1, characterized in that: The ultrasonic phased array scanning comprises the following steps: Adjust the ultrasonic probe posture of the ultrasonic phased array detection equipment to ensure that the ultrasonic probe is concentric with the end of the valve stem; Then turn on the ultrasonic phased array detection equipment, set the corresponding ultrasonic probe center frequency and number of chips, and stimulate the ultrasonic signal through the ultrasonic transducer to perform a rotating scan of the ultrasonic probe.

4. A method for detecting valve stem defects of an in-service gas tree according to claim 3, characterized in that: The rotation scanning also includes the following steps: In the ultrasonic phased array detection device, the deflection angle is set by adjusting the focal law, and the focal law of the end of the ultrasonic probe is adjusted in turn to each wafer module, and excited in turn; The ultrasonic beam is deflected to the valve stem surface after being controlled by the focusing law. The ultrasonic phased array detection equipment controls the deflection angle of each chip module, and scans from small to large angles to obtain the structural information of the circumferential surface of the valve stem. Input the actual depth of the specimen into the ultrasonic phased array instrument to obtain the propagation time required for the single excitation bottom wave signal echo; The intermittent working time of each chip module is set to be the total time from exciting the ultrasonic sound beam to receiving the bottom wave signal once, and several chip modules are stimulated in turn to obtain a single scanning result; Then rotate the ultrasonic probe by a certain angle and perform several scans to cover the entire circumferential surface of the valve stem, repeating the above steps for each scan; when the ultrasonic probe is rotated by a certain angle, the center of the ultrasonic probe does not deviate from the center of the valve stem, and the vertical distance between the ultrasonic probe and the valve stem remains unchanged.

5. The method for detecting valve stem defects of an in-service gas tree according to claim 3, characterized in that: A gap for injecting coupling agent is reserved between the end of the ultrasonic probe and the end of the valve stem.

6. The method for detecting valve stem defects of an in-service gas tree according to claim 1, characterized in that: Before performing ultrasonic phased array scanning on the comparison specimen, the phased array probe sound velocity calibration must be performed first.

7. A valve stem defect detection system for an in-service gas tree, characterized in that: Includes ultrasound probe; The ultrasonic probe comprises a probe body (11), a rotation positioning auxiliary tooling and a chip module; a plurality of chip modules are detachably and evenly distributed in a circular direction at the end of the probe body (11); the chip modules are connected to the communication part of the probe body (11) and are used to excite the ultrasonic phased array; The rotational positioning auxiliary tooling is located at the center of the end of the probe body (11), the lower end of the rotational positioning auxiliary tooling is connected to the end of the valve stem, and the upper end of the rotational positioning auxiliary tooling is rotatably connected to the probe body (11): the probe body (11) can rotate around its own axis.

8. The valve stem defect detection system for an in-service gas tree according to claim 7, characterized in that: The end of the probe body (11) is evenly distributed with a plurality of sockets in the circumference, each of the sockets is provided with a slot (12), and the slot (12) is connected to a communication part in the probe body (11) via a communication cable (16); The wafer module comprises a module housing (23), the upper end of the module housing (23) is used to be inserted into the socket, and the upper end of the module housing (23) is provided with a plug (22) adapted to the slot (12) on a side facing the socket; The lower end of the module housing (23) is provided with a plurality of bottom chips (25) arranged in sequence along the radial direction of the probe body (11); the plurality of bottom chips (25) are connected to a communication part in the probe body (11) through the slot (12).

9. The in-service gas tree valve stem defect detection system according to claim 8, characterized in that: The socket is a T-shaped socket, and the upper end of the module housing (23) is a T-shaped plug adapted to the T-shaped socket.

10. The in-service gas tree valve stem defect detection system according to claim 7, characterized in that: The rotary positioning auxiliary tooling comprises a positioning pillar (31), the bottom of the positioning pillar (31) is provided with a suction cup (32), and a bearing (34) is rotatably sleeved on the positioning pillar (31); The axis of the probe body (11) is provided with a through hole, the upper end of which is used to install the inserted communication part; the lower end of the through hole is provided with a bearing mounting hole (14) for installing the bearing (34); the bottom of the communication part is provided with a circular hole for positioning with the upper end of the positioning support (31).

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