A petroleum product pipe longitudinal defect depth measuring instrument

Abstract

The present application relates to the technical field of defect depth measurement, and discloses a petroleum product pipe longitudinal defect depth measuring instrument, which comprises a laser intelligent sensor measuring module and a centering arm, a jaw one arranged at the top of one end of the centering arm, a jaw two arranged at the top of the jaw one, an upper centering adjusting arm arranged at the bottom of the end of the jaw two away from the jaw one, a radius measuring arm arranged at the top of the end of the jaw two away from the jaw one, a measuring scale arranged at the top of an auxiliary measuring arm, a moving hole arranged in the middle of the centering arm, through holes linearly arranged on the upper and lower centering adjusting arms respectively, and a groove arranged on the auxiliary measuring arm, and the laser intelligent sensor measuring module is used for measuring an incident point and a front length. Through non-contact measurement of the laser intelligent sensor, automatic calculation and millimeter-level precision control, the subjective error and low efficiency of the traditional method are solved, and the accuracy of detection data is guaranteed from the source.

Description

Technical Field

[0001] This invention relates to the field of defect depth measurement technology, and in particular to a longitudinal defect depth measuring instrument for petroleum product pipes. Background Technology

[0002] The depth of defects in oil pipelines refers to the extent of damage to the pipeline caused by various factors, including manufacturing defects, welding problems, and external environmental influences during use. Defect depth is typically determined using non-destructive testing (NDT) methods such as magnetic particle testing, penetrant testing, and ultrasonic testing. NDT primarily identifies internal defects by observing magnetic particle and penetrant traces or sound wave reflections on the pipeline surface to determine the presence of cracks, inclusions, folds, or other issues. Based on the depth of defects, oil pipeline defects can be categorized into three levels: minor, moderate, and severe.

[0003] Longitudinal defects in forged and rolled tubular materials are typically measured circumferentially using a slant probe. In this case, the positioning technique using a transverse wave slant probe for planar workpieces is unsuitable. To accommodate workpieces with wall thicknesses and radii greater than 0.226 or 0.26, the refraction angle of the slant probe is reduced accordingly. The probe emits both transverse and longitudinal waves. Therefore, when applying the circumferential detection positioning formula, it is necessary to determine the wave type (transverse or longitudinal wave), which can easily lead to misjudgments and positioning errors; furthermore, the calculations are more complex. Using a depth measuring instrument allows for direct reading of defect depth and refraction angle, providing fast and accurate positioning, and also enabling the determination of the generated waveform.

[0004] Existing defect depth measurements are not fast or accurate enough, and adjustments are cumbersome. Defect depth and refraction angle cannot be read intuitively, and the precision and accuracy are not high enough. Furthermore, after measurement, existing devices require a large number of complex calculations and conversions, making the operation process cumbersome, the measurement efficiency low, and the adaptability not strong enough. Summary of the Invention

[0005] Given the problems of existing technologies, such as the inability to intuitively read the depth and refraction angle of defects, the need for extensive and complex calculations, and insufficient precision and accuracy, a longitudinal defect depth measuring instrument for petroleum product pipes is proposed.

[0006] Its purpose is to improve the accuracy and precision of measurements, achieve rapid and intuitive measurements, simplify the operation process, and improve measurement efficiency.

[0007] The technical solution of the present invention is a longitudinal defect depth measuring instrument for petroleum product pipes, including a laser intelligent sensor measuring module and a centering arm, a jaw 1 set at the top of one end of the centering arm, a jaw 2 set at the middle position of the top of jaw 1, an upper centering adjustment arm set at the bottom of jaw 2 away from the jaw 1 end, a radius measuring arm set at the top of jaw 2 away from the jaw 1 end, a vernier set on the radius measuring arm, a lower centering adjustment arm set at the bottom of the upper centering adjustment arm near the bottom of one end of the centering arm, with the upper centering adjustment arm set at the bottom of the centering arm, and the lower centering adjustment arm set at the bottom of jaw 1 away from the centering arm, an auxiliary measuring arm set at the top of jaw 1 away from the centering arm, a measuring ruler set at the top of the auxiliary measuring arm, with the measuring ruler located at the top of the radius measuring arm, a moving hole opened in the middle of the centering arm, through holes linearly arrayed on the upper and lower centering adjustment arms, and a groove opened on the auxiliary measuring arm;

[0008] The laser intelligent sensor module is used to measure the incident point and the length of the leading edge;

[0009] It also includes a locking assembly disposed between the radius measuring arm, the auxiliary measuring arm and the centering arm, and the centering arm, the upper centering adjustment arm and the lower centering adjustment arm are also connected by the locking assembly;

[0010] The locking component is used to lock the measuring instrument after measurement.

[0011] Furthermore, the jaws 2, jaw 1, and centering arm are riveted from top to bottom. One side of jaw 1 and jaw 2 are both arc-shaped, and their jaws can form a semi-circle together. Both of their ends are pointed.

[0012] Furthermore, the radius measuring arm is engraved with graduations, the measuring ruler consists of a measuring straight ruler and an angle ruler, the radius measuring arm, jaw two and the upper centering adjustment arm are connected from top to bottom by a pin shaft provided with the radius measuring arm, and the measuring ruler, auxiliary measuring arm, jaw one and the lower centering adjustment arm are connected from top to bottom by a pin shaft provided with the measuring ruler.

[0013] Furthermore, the interconnected arms are adjusted using shims of appropriate thickness to ensure they are on the same plane, facilitating rotational adjustment.

[0014] Furthermore, the fastening assembly located at the radius measuring arm includes a fastening bolt that passes through the radius measuring arm, the auxiliary measuring arm, and the centering arm sequentially from top to bottom, and the fastening bolt is slidably connected in the moving hole, a fastening nut disposed at the bottom of the fastening bolt, a fastening spring disposed at the top of the fastening nut, and a compression plate disposed at the top of the fastening spring, and the top of the compression plate abuts against the bottom of the centering arm.

[0015] Furthermore, the fastening assembly is also provided with an adjustment assembly, which includes a knob on the top of the fastening bolt, a rotating shaft at the bottom of the knob and the rotating shaft being limited to rotating inside the fastening bolt, rotating holes symmetrically opened on both sides of the bottom of the fastening bolt and connected to its interior, adjustment plates symmetrically arranged on both sides of the bottom of the rotating shaft and passing through the rotating holes, and adjustment grooves arranged in a ring array on the top of the extrusion plate.

[0016] Furthermore, the interior of the adjusting groove is an arc-shaped slope, and the bottom of the adjusting plate abuts against the slope of the adjusting groove.

[0017] Furthermore, rubber strips are symmetrically arranged on both sides of the extrusion disc that do not overlap with the two adjustment grooves, and the middle of the rubber strips is V-shaped.

[0018] Furthermore, the set bolt includes a threaded groove formed at the bottom of the set bolt, a smooth surface provided at the bottom of the threaded groove, and the threaded groove is located at the bottom of the extrusion plate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. Through non-contact measurement, automated calculation and millimeter-level precision control of laser intelligent sensors, the measurement of the incident point and leading edge has been transformed from "experience-driven" to "data-driven". This not only solves the problems of subjective error and low efficiency of traditional methods, but also ensures the accuracy of the test data from the source. It is especially suitable for industrial non-destructive testing scenarios with strict accuracy requirements.

[0021] 2. The movable center structure design allows the measuring instrument to directly read the defect depth and refraction angle, resulting in higher precision and accuracy. Furthermore, it is unaffected by viewing angle and lighting conditions, thus providing more accurate depth and angle information. Measurement is convenient and quick, with direct readings avoiding complex calculations and conversions, greatly simplifying the operation process and improving work efficiency. It also enables rapid and accurate positioning and quick waveform determination.

[0022] 3. It uses a set spring to compress and fix the centering arm, unlike the existing bolt and nut direct rigid compression fixation. This eliminates the need for the cumbersome operation of loosening the bolt with tools before adjustment and then tightening it again. The adjustment can be achieved by rotating the adjustment component. Furthermore, due to the compression effect of the set spring, there will be no large-scale movement during adjustment, which can easily lead to excessive or insufficient adjustment distance. It can achieve fast and accurate adjustment, and the adjustment is convenient and quick.

[0023] 4. By adjusting the knob, the rotation range of the adjusting plate within the adjusting groove can be controlled, thus controlling the degree of pressure exerted by the adjusting plate on the pressing disc. This allows the pressing disc, under the pressure of the retaining spring, to continuously exert frictional pressure on the bottom of the centering arm, avoiding the instability caused by the traditional method of loosening the nut and immediately disengaging from the bolt. This improves the stability and accuracy of the adjustment, thereby increasing measurement and adjustment efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall three-dimensional structure of the present invention;

[0025] Figure 2 This is a top view of the overall structure of the present invention;

[0026] Figure 3 This is a schematic diagram of the overall bottom-view three-dimensional structure of the present invention;

[0027] Figure 4 This is a schematic diagram of the overall structure of the clamping component of the present invention during clamping.

[0028] Figure 5 This is a three-dimensional structural diagram of the overall fit between the locking component and the adjusting component of the present invention;

[0029] Figure 6 This is an exploded overall structural diagram of the locking assembly and adjusting assembly of the present invention;

[0030] Figure 7 This is a partial cross-sectional view of the set bolt of the present invention.

[0031] In the picture:

[0032] 1. Centering arm; 2. Jaw 1; 3. Jaw 2; 4. Upper centering adjustment arm; 5. Radius measuring arm; 6. Vernier; 7. Lower centering adjustment arm; 8. Auxiliary measuring arm; 9. Measuring ruler; 10. Moving hole; 11. Through hole; 12. Groove; 13. Washer; 14. Set bolt; 15. Set nut; 16. Set spring; 17. Extrusion plate; 18. Knob; 19. Rotating shaft; 20. Rotating hole; 21. Adjusting plate; 22. Adjusting groove; 23. Rubber strip; 24. Threaded groove; 25. Smooth surface. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] Example 1, referring to Figures 1-3This invention provides a longitudinal defect depth measuring instrument for petroleum product pipes, with an overall length of 460 mm. It includes a laser intelligent sensor measuring module and a centering arm 1 mounted on the instrument; a jaw 2 rotatably connected to the top of one end of the centering arm 1; a jaw 3 rotatably connected to the middle of the top of jaw 2; an upper centering adjustment arm 4 rotatably connected to the bottom of jaw 3 away from jaw 2; a radius measuring arm 5 rotatably connected to the top of jaw 3 away from jaw 2; a vernier 6 slidably connected to the radius measuring arm 5; and a lower centering adjustment arm 7 rotatably connected to the upper centering adjustment arm 4 near the bottom of one end of the centering arm 1. The upper centering adjustment arm 4 is located at the bottom of the centering arm 1, and the lower centering adjustment arm 7, away from the centering arm 1, is movably connected to the bottom of jaw 2 at one end. 2. An auxiliary measuring arm 8 is located at the top of the auxiliary measuring arm 8 away from the centering arm 1. A measuring ruler 9 is rotatably connected to the top of the auxiliary measuring arm 8 and is located at the top of the radius measuring arm 5. A movable hole 10 is opened in the middle of the centering arm 1. Through holes 11 are linearly arrayed on the upper centering adjustment arm 4 and the lower centering adjustment arm 7, respectively. A groove 12 is opened on the auxiliary measuring arm 8. The laser intelligent sensor module is used to measure the incident point and the leading edge length. It integrates an intelligent chip, which can autonomously control the transmission and reception of signals and automatically calculate the signals to calculate the incident point coordinates and the leading edge length. It also includes a locking component installed between the radius measuring arm 5, the auxiliary measuring arm 8 and the centering arm 1. The centering arm 1, the upper centering adjustment arm 4 and the lower centering adjustment arm 7 are also connected by the locking component. The locking component is used to lock the measuring instrument after measurement.

[0035] Specifically, when probing a cylindrical workpiece with shear waves, the location of defects can be determined by the arc length (or chord length) and depth of the defect. During the measurement, the same defect and the same sound path (reaching the reference wave height) of the shear wave and secondary wave are located on the same circumference from both positive and negative directions. The position of the leading edge or incident point on the workpiece is calibrated. The midpoint of the distance between the two leading edges is the radial position of the defect on the circumference. The distance between the incident point and the midpoint is the arc length (or chord length) of the defect. The depth of the defect can be read by measuring the intersection of the sound path (displayed on the flaw detector) and the radius. In this way, the location of the defect is determined.

[0036] During the specific measurement, the incident point of the probe is measured first. When the angled probe wedge curvature has been ground, a vertical laser beam can be emitted through the laser displacement sensor in the laser intelligent sensor measurement module to capture the distance between the probe and the edge of the test block in real time, and automatically calculate the coordinates of the incident point (accuracy ±0.02mm), replacing manual visual interpretation and eliminating subjective errors. When the wedge is not ground, a three-dimensional model of the probe end face is constructed using a line laser scanner, and the incident point and the leading edge length are fitted together with the echo signal (accuracy ±0.05mm). A baseline is projected by a laser line marker to assist in grinding, ensuring that the incident point is accurately positioned along the direction of the sound beam. Traditional methods rely on manual observation of echo peaks, scale alignment, or manual engraving, which are easily affected by visual judgment and operating techniques (e.g., in the edge reflection method, finding the strongest echo based on experience can result in an error of ±0.5mm). Through the non-contact measurement, automated calculation, and millimeter-level precision control of laser intelligent sensors, the measurement of the incident point and leading edge has been transformed from "experience-driven" to "data-driven." This not only solves the problems of subjective error and low efficiency of traditional methods but also ensures the accuracy of the test data from the source, making it particularly suitable for industrial non-destructive testing scenarios with stringent precision requirements. Next, measure the arc length (chord length). Align jaw 2 and jaw 3 with the incident point and center point respectively, and lock the locking assembly between points D. This will measure the arc length (chord length). Then, locate the center. After locking jaw 2 and jaw 3, adjust the horizontal line on the end face of knob 18 at point E to coincide with the corresponding radius value scale line on the radius measuring arm 5, and lock the locking assembly at E. At this point, the center and radius are determined. Finally, start the scale of measuring ruler 9 from point C and the scale of radius measuring arm 5 from point B. The intersection of the sound path scale point of measuring ruler 9 and the edge of the center line of vernier 6 is the sound path. The intersection of the edge of vernier 6 and the radius measuring arm 5 is the defect depth. The intersection of measuring ruler 9 and the left edge of the groove 12 of auxiliary measuring arm 8 can be used to read the incident angle, thereby determining the waveform (transverse wave or longitudinal wave). When the waveform is correct, the intersection point will definitely be within the wall thickness range for depth measurement.

[0037] If the workpiece radius is ≤140 mm, satisfactory results can be obtained when the measurement refraction angle reaches approximately 17°; when the workpiece radius is ≥140 mm, the radius is R1; within the measurement range, the radius is R2, let... Adjust the jaw length to For a given arc length (chord length) corresponding to a specific value, the radius measuring arm 5 and the measuring ruler 9 are proportionally enlarged to K times their original size, thus enabling the positioning of large workpieces. When the required defect range is radially extended, it can be roughly measured at the endpoints or obtained approximately from the defect equivalent on the distance amplitude curve.

[0038] The aforementioned movable center structure design allows the measuring instrument to directly read the defect depth and refraction angle, resulting in higher precision and accuracy. Furthermore, it is unaffected by viewing angle and lighting conditions, thus providing more accurate depth and angle information. Measurement is convenient and quick, with direct readings avoiding complex calculations and conversions, greatly simplifying the operation process and improving work efficiency. It also enables rapid and accurate positioning and quick waveform determination.

[0039] Reference Figures 1-3 The jaws 2, 3, 2 and centering arm 1 are riveted from top to bottom. One side of jaws 2 and 3 is arc-shaped, and their jaws can form a semi-circle together. Both of their ends are pointed.

[0040] Specifically, the arc-shaped jaws 1 and 2 can expand the measurement range and facilitate clamping, while the pointed ends facilitate accurate clamping of defects.

[0041] Reference Figures 1-3 The radius measuring arm 5 is engraved with graduations. The measuring ruler 9 consists of a measuring straight ruler and an angle ruler. The radius measuring arm 5, jaw 2 3 and the upper centering adjustment arm 4 are connected from top to bottom by the pins that come with the radius measuring arm 5. The measuring ruler 9, the auxiliary measuring arm 8, jaw 1 2 and the lower centering adjustment arm 7 are connected from top to bottom by the pins that come with the measuring ruler 9.

[0042] Specifically, during measurement, data can be directly read from the scale and angle on the radius measuring arm 5 and the measuring ruler 9, which is convenient, quick, and improves the accuracy and efficiency of measurement.

[0043] Reference Figure 1 and 3 The interconnected arms are adjusted by shims 13 of appropriate thickness to make them lie on the same plane, which facilitates rotation and adjustment.

[0044] Specifically, the gasket 13 ensures that the contact points of several interconnected arms are on the same plane, facilitating rotation during measurement.

[0045] Example 2, refer to Figures 1-5 This is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that the fastening assembly located at the radius measuring arm 5 includes a fastening bolt 14 that passes through the radius measuring arm 5, the auxiliary measuring arm 8 and the centering arm 1 from top to bottom. The fastening bolt 14 is slidably connected in the moving hole 10. A fastening nut 15 is threaded to the bottom of the fastening bolt 14. A fastening spring 16 abuts against the top of the fastening nut 15. A compression plate 17 abuts against the top of the fastening spring 16. The top of the compression plate 17 abuts against the bottom of the centering arm 1.

[0046] Specifically, during adjustment, the positions at points D and E need to be adjusted. This can be done by first tightening the set nut 15, which compresses the set spring 16. The set spring 16 then presses against the extrusion plate 17, which, under the pressure of the set spring 16, compresses the bottom of the centering arm 1. This compression and fixation of the centering arm 1 is achieved through the set spring 16, unlike the existing method of directly and rigidly compressing and fixing with bolts and nuts. This eliminates the cumbersome process of loosening the bolts with tools before adjustment and then tightening them again. Adjustment can be achieved by rotating the adjustment assembly, allowing for direct movement. Furthermore, due to the compression effect of the set spring 16, large movements during adjustment are prevented, avoiding excessive or insufficient adjustment distances. This enables quick and precise adjustment, and is convenient and fast. The remaining structure is the same as in Embodiment 1.

[0047] Example 3, referring to Figures 1-7 This is the third embodiment of the present invention. The difference between this embodiment and the second embodiment is that an adjustment assembly is also installed inside the fastening assembly. The adjustment assembly includes a knob 18 rotatably connected to the top of the fastening bolt 14, a rotating shaft 19 fixedly connected to the bottom of the knob 18 and the rotating shaft 19 is limited to rotating inside the fastening bolt 14, rotating holes 20 symmetrically opened on both sides of the bottom of the fastening bolt 14 and communicating with the inside therein, an adjustment plate 21 symmetrically fixedly connected to both sides of the bottom of the rotating shaft 19 and passing through the rotating holes 20, and an adjustment groove 22 arranged in a ring array on the top of the extrusion plate 17.

[0048] Specifically, during adjustment, by gripping the computer knob 18, the knob 18 drives the rotating shaft 19 and the adjusting plates 21 on both sides to rotate within the rotating hole 20. The bottom of the adjusting plate 21 rotates within the adjusting groove 22, causing the pressing disc 17 to be pressed downwards, thus disengaging from the pressure on the bottom of the centering arm 1, thereby adjusting the tightening bolt. Furthermore, the rotation amplitude of the knob 18 can be controlled to control the rotation amplitude of the adjusting plate 21 within the adjusting groove 22, thereby controlling the downward pressure of the adjusting plate 21 on the pressing disc 17. In this way, under the pressure of the retaining spring 16, the pressing disc 17 continuously exerts frictional pressure on the bottom of the centering arm 1, avoiding the instability caused by the traditional method of the nut directly disengaging from the bolt after being loosened. This improves the stability and accuracy of the adjustment, thereby increasing the efficiency of measurement and adjustment.

[0049] Reference Figure 5 and Figure 7 The interior of the adjusting groove 22 is an arc-shaped slope, and the bottom of the adjusting plate 21 abuts against the slope of the adjusting groove 22.

[0050] Specifically, when the adjusting plate 21 rotates, the slope in the extrusion adjusting groove 22 causes the extrusion disc 17 to move downward, thereby controlling the degree of extrusion of the extrusion disc 17.

[0051] Reference Figure 7 Rubber strips 23 are symmetrically fixedly connected to the two sides of the extrusion plate 17 that do not overlap with the two adjustment grooves 22, and the middle part of the rubber strips 23 is V-shaped.

[0052] Specifically, the V-shaped rubber strip 23 in the middle can improve the degree of compression and fixation of the compression plate 17 on the centering arm 1 after tightening. It can also increase the friction between the compression plate 17 and the bottom of the centering arm 1 during adjustment and movement, so as to avoid the adjustment range being too large or too small.

[0053] Reference Figure 6 The set bolt 14 includes a threaded groove 24 formed at the bottom of the set bolt 14, a smooth surface 25 provided at the bottom of the threaded groove 24, and the threaded groove 24 is located at the bottom of the extrusion plate 17.

[0054] Specifically, since the thickness of the centering arm 1 is fixed, when the set nut 15 moves in the threaded groove 24 at the bottom, the centering arm 1 can be pressed and fixed by squeezing the tightening spring and the squeezing circular plate 17. When the knob 18 is turned, the adjusting plates 21 on both sides at the bottom can rotate within the moving hole 10. The rest of the structure is the same as that of Embodiment 2.

[0055] Based on embodiments 1-3, the working principle of this invention is as follows: During measurement, the jaws 2 and 3 are aligned with the incident point and center point respectively, and the set screw 14 between the upper centering adjustment arm 4 and the lower centering adjustment arm 7 is locked to measure the arc length. Then, the center of the circle is determined by aligning the horizontal line on the end face of the adjustment knob 18 with the corresponding radius value scale line on the radius measuring arm 5 and locking the settling assembly. Finally, the sound path, defect depth, and incident angle are read by adjusting the measuring ruler 9 and the radius measuring arm 5, and the waveform is determined. During measurement and adjustment, the knob 18 is turned so that the adjusting plate 21 presses the adjusting groove 22, and the pressing circular plate 17 presses the settling spring 16 to achieve movement during adjustment. The friction force during adjustment movement is controlled by controlling the rotation amplitude of the knob 18.

[0056] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A longitudinal defect depth measuring instrument for petroleum product pipes, characterized in that: The system includes a laser intelligent sensor measurement module and a centering arm (1), a jaw 1 (2) located at the top of one end of the centering arm (1), a jaw 2 (3) located at the middle of the top of the jaw 1 (2), an upper centering adjustment arm (4) located at the bottom of the jaw 2 (3) away from the jaw 1 (2), a radius measuring arm (5) located at the top of the jaw 2 (3) away from the jaw 1 (2), a vernier (6) on the radius measuring arm (5), and a lower centering adjustment arm (7) located at the bottom of the upper centering adjustment arm (4) near the bottom of one end of the centering arm (1). The upper centering adjustment arm (4) is located at... The bottom of the centering arm (1), the end of the lower centering adjustment arm (7) away from the centering arm (1) is set at the bottom of the jaw (2), the top of the jaw (2) away from the centering arm (1) is set at the top of the auxiliary measuring arm (8), the measuring ruler (9) is set at the top of the auxiliary measuring arm (8), and the measuring ruler (9) is located at the top of the radius measuring arm (5), the moving hole (10) is opened in the middle of the centering arm (1), the through holes (11) are linearly arrayed on the upper centering adjustment arm (4) and the lower centering adjustment arm (7), and the groove (12) is opened on the auxiliary measuring arm (8); The laser intelligent sensor measurement module is used to measure the incident point and the length of the leading edge. It also includes a locking assembly disposed between the radius measuring arm (5), the auxiliary measuring arm (8) and the centering arm (1), and the centering arm (1), the upper centering adjustment arm (4) and the lower centering adjustment arm (7) are also connected by the locking assembly; the locking assembly is used to lock the measuring instrument after measurement.

2. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 1, characterized in that: The jaws 2 (3), jaw 1 (2) and centering arm (1) are riveted from top to bottom. One side of jaw 1 (2) and jaw 2 (3) are both arc-shaped, and their jaws can form a semi-circle together. Both of their ends are pointed.

3. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 1, characterized in that: The radius measuring arm (5) is engraved with scales. The measuring ruler (9) consists of a measuring straight ruler and an angle ruler. The radius measuring arm (5), jaw two (3) and upper centering adjustment arm (4) are connected from top to bottom by a pin shaft that comes with the radius measuring arm (5). The measuring ruler (9), auxiliary measuring arm (8), jaw one (2) and lower centering adjustment arm (7) are connected from top to bottom by a pin shaft that comes with the measuring ruler (9).

4. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 1, characterized in that: The interconnected arms are adjusted by shims (13) of appropriate thickness to make them lie on the same plane, which facilitates rotation and adjustment.

5. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 1, characterized in that: The fastening assembly located at the radius measuring arm (5) includes a fastening bolt (14) that passes through the radius measuring arm (5), the auxiliary measuring arm (8) and the centering arm (1) from top to bottom, and the fastening bolt (14) is slidably connected in the moving hole (10), a fastening nut (15) is provided at the bottom of the fastening bolt (14), a fastening spring (16) is provided at the top of the fastening nut (15), and a pressing plate (17) is provided at the top of the fastening spring (16), and the top of the pressing plate (17) abuts against the bottom of the centering arm (1).

6. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 5, characterized in that: The fastening assembly is further provided with an adjustment assembly, which includes a knob (18) on the top of the fastening bolt (14), a rotating shaft (19) on the bottom of the knob (18) and the rotating shaft (19) is limited to rotating inside the fastening bolt (14), rotating holes (20) symmetrically opened on both sides of the bottom of the fastening bolt (14) and connected to its interior, adjustment plates (21) symmetrically arranged on both sides of the bottom of the rotating shaft (19) and passing through the rotating holes (20), and adjustment grooves (22) arranged in a ring array on the top of the extrusion plate (17).

7. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 6, characterized in that: The interior of the adjustment groove (22) is an arc-shaped slope, and the bottom of the adjustment plate (21) abuts against the slope of the adjustment groove (22).

8. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 6, characterized in that: Rubber strips (23) are symmetrically arranged on both sides of the extrusion plate (17) that do not overlap with the two adjustment grooves (22), and the middle part of the rubber strips (23) is V-shaped.

9. The longitudinal defect depth measuring instrument for petroleum product pipes according to claim 5, characterized in that: The set bolt (14) includes a threaded groove (24) at the bottom of the set bolt (14), a smooth surface (25) at the bottom of the threaded groove (24), and the threaded groove (24) is located at the bottom of the extrusion plate (17).

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