A metal pipe inner wall defect detection device

Abstract

A metal pipe inner wall defect detection device mainly includes a metal pipe to be tested, an isolation tube, and a capacitance measurement module. The annular gap between the outer wall of the isolation tube and the inner wall of the metal pipe to be tested is filled with insulating liquid, and the isolation tube is filled with conductive liquid. A cylindrical capacitor is formed between the conductive liquid and the metal pipe wall. The corresponding capacitance value can be obtained by changing the height of the conductive liquid. The position and degree of metal loss on the inner wall of the pipe can be determined by the capacitance-liquid level height curve. The invention has the advantages of being able to quickly obtain the metal loss parameters of the coating of the workpiece to be tested along the axial direction, without damaging the pipeline to be tested, being simple and convenient to implement, and having broad prospects for promotion and application.

Description

Technical field:

[0001] The invention belongs to the field of pipeline detection technology, and in particular relates to a metal pipeline inner wall defect detection device. Background technology:

[0002] Pipelines are widely used in various fields of industrial production. During operation, due to corrosion, abrasion, etc., metal loss usually occurs inside the pipeline, resulting in thinning of the pipe wall. Accurately measuring the damage to the inner wall of the cut metal pipe section is a prerequisite for studying the damage law and then proposing control measures. The current methods for measuring damage to the inner wall of the pipeline mainly include ultrasonic method, X-ray method and camera method. The ultrasonic method requires the use of a coupling agent to scan the entire circumference of the pipe, and the measurement efficiency is low. The X-ray method uses a high-energy radiation source and has radiation risks. The camera method detects the inner wall by placing a camera in the pipeline, which is difficult to apply to slender pipelines.

[0003] In view of the shortcomings of existing pipeline inner wall metal damage measurement devices, the present invention proposes a new capacitance measurement method suitable for slender metal pipe sections, which can realize rapid and non-destructive measurement of pipeline inner wall metal damage. Summary of the invention:

[0004] A metal pipe inner wall defect detection device, characterized in that it mainly includes a metal pipe to be tested, an isolation tube, a positioning ring, a top sealing plug, a bottom sealing plug, a connecting pipe, and a capacitance measuring module. The isolation tube has the same height as the metal pipe to be tested and is located inside the metal pipe to be tested. Positioning rings are provided at the top and bottom of the metal pipe to be tested. The positioning rings are placed between the inner wall of the metal pipe and the outer wall of the isolation tube to ensure that the metal pipe to be tested and the isolation tube are coaxial. A top sealing plug is provided at the top of the isolation tube, and a bottom sealing plug is provided at the bottom of the isolation tube. A conductive liquid injection pipe is provided on the top sealing plug to add conductive liquid into the isolation tube. A conductive liquid discharge pipe is provided on the bottom sealing plug. An insulating liquid filling pipe is provided on the positioning ring located at the top to add insulating liquid into the annular gap between the outer wall of the isolation tube and the inner wall of the metal pipe to be tested. One end of the capacitance measuring module is connected to the pipe wall of the metal pipe to be tested through a metal wire, and the other end is connected to the conductive liquid in the isolation tube through a metal wire. One end of the connecting pipe is installed on the top sealing plug, and the other end is installed on the bottom sealing plug.

[0005] The outer diameter of the isolation tube is not less than 95% of the inner diameter of the metal tube to be measured, the wall thickness is less than 1 mm, and it is made of insulating material. The insulating material has the same dielectric constant as the insulating liquid.

[0006] The conductive liquid discharge pipe is provided with a valve, and the connecting pipe is provided with a liquid level gauge.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] (1) Fast response speed, which can realize rapid measurement of defects of the workpiece to be tested;

[0009] (2) The measurement results are not affected by changes in parameters such as the salt content and temperature of the conductive liquid and can be measured over a wide range of flow patterns. Description of the drawings:

[0010] Figure 1 A schematic diagram of the structure of the present invention;

[0011] Figure 2 A schematic top cross-sectional view of the present invention;

[0012] Figure 3 The working principle diagram of the present invention (reference limiter cross section);

[0013] Figure 4 Capacitance-liquid level relationship diagram;

[0014] 1. Metal tube; 2. Isolation tube; 3. Positioning ring; 4. Top sealing plug; 5. Bottom sealing plug; 6. Connecting tube; 7. Capacitance measurement module; 8. Conductive liquid injection tube; 9. Conductive liquid; 10. Conductive liquid discharge tube; 11. Insulating liquid injection tube; 12. Insulating liquid; 13. Drain valve; 14. Liquid level gauge; Specific implementation method:

[0015] like Figure 1 It is a schematic diagram of the structure of the present invention. Figure 2 It is a schematic diagram of the top cross section of the present invention. The present invention mainly comprises a metal tube 1 to be tested, an isolation tube 2, a positioning ring 3, a top sealing plug 4, a bottom sealing plug 5, a connecting tube 6, and a capacitance measurement module 7. The isolation tube 2 has the same height as the metal tube 1 to be tested and is located inside the metal tube 1 to be tested. Positioning rings 3 are provided at the top and bottom of the metal tube 1 to be tested. The positioning rings 3 are placed between the inner wall of the metal tube 1 and the outer wall of the isolation tube 2 to ensure that the metal tube 1 to be tested and the isolation tube 2 are coaxial. A top sealing plug 4 is provided at the top of the isolation tube 2, and a bottom sealing plug 5 is provided at the bottom of the isolation tube 2. A conductive liquid injection pipe 8 is provided on the top sealing plug 4 for filling the isolation tube 2 with conductive liquid 9, and a conductive liquid discharge pipe 10 is provided on the bottom sealing plug 5. An insulating liquid filling pipe 11 is provided on the positioning ring 3 at the top for filling the annular gap between the outer wall of the isolation tube 2 and the inner wall of the metal tube 1 to be tested. 12. One end of the capacitance measurement module 7 is connected to the wall of the metal tube 1 to be measured through a metal wire, and the other end is connected to the conductive liquid 9 in the isolation tube 2 through a metal wire; one end of the connecting tube 6 is installed on the top sealing plug 4, and the other end is installed on the bottom sealing plug 5.

[0016] The outer diameter of the isolation tube 2 is not less than 95% of the inner diameter of the metal tube 1 to be measured, the wall thickness is less than 1 mm, and it is made of insulating material. The insulating material and the insulating liquid 12 have the same dielectric constant.

[0017] The conductive liquid discharge pipe 10 is provided with a valve 13 , and the connecting pipe 6 is provided with a liquid level gauge 14 .

[0018] The working principle of the present invention is as follows:

[0019] like Figure 3 As shown, since the annular gap formed between the inner wall of the metal tube 1 to be tested and the outer wall of the isolation tube 2 is filled with insulating liquid 12, and the dielectric constant of the insulating liquid 12 is the same as that of the material of the isolation tube 2, it can be considered that the inner wall of the metal to be tested is coated with an insulating layer with a thickness of δ. When a conductive liquid 9 with a height of L is injected into the insulating tube, a cylindrical capacitor is formed between the conductive liquid 9 and the tube wall, and the insulating liquid 12 and the material of the isolation tube 2 act as the dielectric of the capacitor, and the capacitance calculation formula is:

[0020]

[0021] Wherein, L is the height of the conductive liquid 9; d is the inner diameter of the insulating tube; δ is the thickness of the insulating layer; ε is the dielectric constant of the insulating layer.

[0022] It can be seen from the formula that d and ε are both constants. For the metal tube 1 with a smooth inner wall and no mass loss, the gap δ between the inside of the metal tube 1 and the inside of the isolation tube 2 is also a constant, and there is a linear relationship between the capacitance value C and the liquid level height L. If metal loss occurs on the inner wall of the metal tube, the gap between the inside of the metal tube 1 and the inside of the isolation tube 2 increases, that is, δ increases, and thus according to formula (1), the measured capacitance value decreases.

[0023] By changing the liquid level of the conductive liquid 9, a series of capacitance values ​​corresponding to the liquid level can be obtained. Figure 4 The figure shows the capacitance comparison between a normal pipeline and a pipeline with metal loss inside. It can be seen that the location of the metal loss can be determined based on the capacitance value, and the size of δ can be calculated based on formula (1), thereby knowing the severity of the metal loss.

[0024] The present invention works as follows:

[0025] (1) Place the isolation tube 2 in the metal tube 1 to be tested, and install positioning rings 3 on the top and bottom of the metal tube 1 to be tested, respectively. The positioning rings 3 are located on the inner wall of the metal tube 1 and the outer wall of the isolation tube 2 to ensure that the metal tube 1 to be tested and the isolation tube 2 are coaxial;

[0026] (2) Install sealing plugs at the top and bottom of the isolation tube 2 respectively;

[0027] (3) Add insulating liquid 12 into the annular gap between the inner wall of the metal tube 1 to be tested and the outer wall of the isolation tube 2 through the insulating liquid injection pipe 11 until the entire annular gap space is filled;

[0028] (4) A certain amount of water or other conductive liquid is injected into the isolation tube 2 through the conductive liquid injection pipe 8, the current liquid level L is recorded through the liquid level gauge 14 on the connecting pipe 6, and the capacitance value at the current liquid level is measured through the capacitance measurement module 7;

[0029] (5) Changing the liquid level by increasing the injection volume or opening the discharge valve 13 of the conductive liquid discharge pipe 10, thereby obtaining a series of liquid level heights uniformly distributed along the metal tube 1 to be tested, and corresponding capacitance values;

[0030] (6) Draw a curve as shown in the figure. If there is metal loss in the metal tube 1 at a certain liquid level, the capacitance value will suddenly decrease, so that the metal loss position can be determined. The specific metal loss thickness can also be calculated by formula (1).

[0031] The present invention can quickly obtain metal damage data of the inner wall of the metal tube 1 along the axial height direction without damaging the workpiece to be measured, is simple and convenient to implement, and has broad prospects for promotion and application.

Claims

1. A metal pipe inner wall defect detection device, characterized in that: The invention mainly comprises a metal tube to be tested (1), an isolation tube (2), a positioning ring (3), a top sealing plug (4), a bottom sealing plug (5), a connecting tube (6), and a capacitance measuring module (7). The isolation tube (2) is at the same height as the metal tube to be tested (1) and is located inside the metal tube to be tested (1). Positioning rings (3) are provided at the top and bottom of the metal tube to be tested (1). The positioning rings (3) are placed between the inner wall of the metal tube (1) and the outer wall of the isolation tube (2) to ensure that the metal tube to be tested (1) and the isolation tube (2) are coaxial. A top sealing plug (4) is provided at the top of the isolation tube (2), and a bottom sealing plug (5) is provided at the bottom of the isolation tube (2). The top sealing plug (4) is provided at the top of the isolation tube (2), and a bottom sealing plug (5) is provided at the bottom of the isolation tube (2). 4) is provided with a conductive liquid injection pipe (8) for filling the insulating tube (2) with conductive liquid (9), and the bottom sealing plug (5) is provided with a conductive liquid discharge pipe (10); the positioning ring (3) at the top is provided with an insulating liquid filling pipe (11) for filling the annular gap between the outer wall of the insulating tube (2) and the inner wall of the metal tube (1) to be measured with insulating liquid (12); one end of the capacitance measurement module (7) is connected to the tube wall of the metal tube (1) to be measured through a metal wire, and the other end is connected to the conductive liquid (9) in the insulating tube (2) through a metal wire; one end of the connecting pipe (6) is installed on the top sealing plug (4), and the other end is installed on the bottom sealing plug (5).

2. A metal pipe inner wall defect detection device according to claim 1, characterized in that: The outer diameter of the isolation tube (2) is not less than 95% of the inner diameter of the metal tube (1) to be measured, the wall thickness is less than 1 mm, and it is made of insulating material. The insulating material and the insulating liquid (12) have the same dielectric constant.

3. The metal pipe inner wall defect detection device according to claim 1, characterized in that: The conductive liquid discharge pipe (11) is provided with a valve (13); and the connecting pipe (6) is provided with a liquid level gauge (14).

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