CN103604022B - High-precision inner detecting device for seabed oil and gas pipeline flaws - Google Patents

Abstract

A high-precision internal detection device for defects in submarine oil and gas pipelines. The anti-collision head and the front power cup are connected at the front end of the body support shaft. The rear of the front power cup is connected with the floating magnetization detection block through the front floating hinge mechanism. Lift up the spring to form a floatable magnetization circuit and a magnetic flux leakage detection block unit; install a finger probe on the floating magnetization detection block, install a guide groove and a limit ring at the rear end of the body support shaft, and install it at the rear of the guide groove Power cups, front and rear power cups together form a power drive system, the battery pack unit and electronic recorder are respectively inserted in the front and rear of the sealed compartment in the body support shaft, and the detector mileage wheel unit is installed at the tail of the body support shaft. The invention adopts a floating magnetization detection structure, which well solves the problem of in-line detection of oil and gas pipeline defects under complex working conditions.

Description

High-precision internal detection device for subsea oil and gas pipeline defects

technical field

The invention relates to the technical field of detection of submarine oil and gas pipelines, in particular to a high-precision internal detection device for defects of submarine oil and gas pipelines.

Background technique

With the development of offshore oil and gas extraction technology, the supporting submarine oil and gas pipeline technology is also constantly improving, and the safety of offshore oil pipelines is a key technology in this field. Because there are great differences between submarine oil and gas pipelines and land oil and gas pipelines: first, the risk is high, because offshore oil pipeline construction is difficult and costly, and once leaked or blocked, it will cause great damage to the environment; second, the working conditions are complex, Submarine oil and gas pipelines are generally laid according to the topography of the seabed, especially when there are vertical risers when the pipeline goes up and down the platform, and the elbow on the platform has a turning radius of 1.5D. This requires that the internal detector used in the online detection of offshore oil pipelines has a high passing capacity and adaptability to pipeline deformation. The structural features of existing oil and gas pipeline defect detectors are in the form of a fixed magnetized mandrel and a magnetically conductive steel brush wheel. Its representative is the patent "high-definition pipeline magnetic flux leakage detector mechanical system" with application number 200710118862.4. Due to the use of a fixed magnetized mandrel, the detector is heavy, and the diameter and length of the non-deformable part will be large, which is not suitable for It is applied to the internal detection of defects in offshore oil pipelines with vertical risers and small turning radii.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a high-precision internal detection device for defects in submarine oil and gas pipelines, which adopts a floating magnetization detection structure, which well solves the problem of in-line detection of defects in oil and gas pipelines under complex working conditions.

In order to achieve the above object, the technical scheme that the present invention takes is:

A high-precision internal detection device for defects in submarine oil and gas pipelines, including a body support shaft 2, the front end of the body support shaft 2 is connected to the anti-collision head and the front power cup 1, the back of the front power cup 1 is connected to the front floating hinge mechanism 3, and the front floating hinge mechanism 3 It is connected with two sets of floating magnetization detection blocks 5, and each set of floating magnetization detection blocks 5 is equipped with lateral jacking springs 4 on the front and rear sides, and the floating magnetization detection blocks 5 are opened by the jacking springs 4 to form a floatable magnetization circuit and magnetic flux leakage Detection block unit; finger probe 6 is installed on the floating magnetization detection block 5, the rear portion of the floating magnetization detection block 5 is a sliding form, and a guide groove and a limit ring are installed at the rear end of the body support shaft 2 to constrain the floating magnetization detection block 5 The amount of lateral swing and up and down movement; the rear power cup 9 is installed at the rear of the guide groove, and the front and rear power cups together form the power drive system; the battery pack unit 7 and Electronic recorder 8, the electrode pair of battery pack unit 7 and electronic recorder 8 is plugged in and powered on to electronic recorder 8; Detector mileage wheel unit 10 is installed at body support shaft 2 afterbody.

The floating magnetization detection block 5 includes a magnetizer 19, the front twisted support shaft 11 is placed in the front end shaft hole of the magnetizer 19, the front winch 18 is fixed on the front end of the magnetizer 19 by an inner angle bolt, and the high-strength magnet 14 is placed on the magnetizer 19. The upper part is fixed by the magnetic pole protection plate 12, and the middle is protected by the magnetic pole shock absorber 13. The magnetic pole protection plate 12 is fixed on the front winch 18 and the magnetizer 19, the finger probe twist support 15 is fixed on the magnetizer 19, and the finger probe 16 Fixed on the finger probe twist support 15, the probe hub 21 is installed under the finger probe 16, the inner stopper 17 of the magnetic pole is fixed behind the finger probe 16, and the wiring box 20 is fixed on the lower part of the magnetizer 19, and the two sides of the magnetizer 19 Wire crimping sheet 22 and spring seat hole 23 are arranged, guide slide block 24 after the fixed end of magnetizer 19, and each assembly forms a whole with magnetizer 19 as the center.

The mileage wheel unit 10 includes a swing arm 27, one end of the swing arm 27 is connected to the hinge seat 25 through a pin, and the mileage wheel 29 is installed at the other end, the rotary encoder 28 is located in the shaft hole of the mileage wheel 29, and one end of the tension spring 26 Connect the swing arm 27, the other end is connected with the hinge seat 25, the tension spring 26 pulls up the swing arm 27, makes the mileage wheel 29 press the metal pipe wall, and moves in the pipe with the detection device.

The front floating hinge mechanism 3 is a double-pair structure, which is composed of a rotating sliding hinge arm and a rotating rocker, wherein the hinge shaft at the lower end of the hinge arm of the double-pair structure moves forward and backward in the sliding groove of the fixed winch seat, and the hinge shaft and the fixed winch seat The matching gap of the sliding groove is 0.50-1 mm. The fixed winch seat of the front floating hinge mechanism 3 is fixed on the installation position of the body support shaft 2. The hinge arm of the double-pair structure is a U-shaped structure, and the joint between the hinge arm and the fixed winch seat The lateral gap is 0.50-1 mm. One end of the rocker with double-pair structure rotates in the fixed winch, and the other end is connected with the hinge arm. ~0.20 mm, the lateral gap between the rocker and the fixed winch is 0.50 ~ 1 mm.

The side of the floating magnetization detection block 5 is equipped with a lateral jacking spring support structure, and each group of floating magnetization detection blocks 5 cooperates with the front floating hinge mechanism 3 and the rear guide chute structure, and the front and rear two groups of jacking springs 4 on the side are mutually pushed up. Specifically, on the side of the magnetizer, a lateral jacking spring seat hole is arranged, the jacking spring 4 presses the bottom surface of the spring seat hole, and a spring guide post is installed in the spring seat hole, and the spring guide post and the spring seat hole match the jacking spring 4. Double guide and limit function to prevent the jacking spring 4 from coming out. The spring guide post is installed in the spring seat hole. The gap between the spring guide post and the inner diameter of the spring is 0.5-1 mm, and the gap between the spring seat hole and the spring outer diameter is 1-2 mm. .

Stainless steel pressure plates are installed on the outside of the front power cup 1 and the rear power cup 9, and the front power cup 1 and the rear power cup 9 are pressed on the cup mounting surface of the body support shaft 2. The front power cup 1 The front and rear installation distance with the rear power leather cup 9 is 1～1.5 times of the inner diameter of the application pipeline.

The seal between the battery pack unit 7 and the internal sealing compartment of the body support shaft 2 adopts two seals in the end direction and the axial direction, the sealing medium is an O-shaped rubber seal ring, and the surface of the battery pack unit 7 cylinder is pasted with two seals at the front and back. Shock-absorbing belt, the material of the shock-absorbing belt is polytetrafluoroethylene.

The sealing between the electronic recorder 8 and the internal sealing compartment of the body support shaft 2 adopts two seals in the end direction and the axial direction, and the sealing medium is an O-shaped rubber sealing ring. Shock-absorbing belt, the material of the shock-absorbing belt is polytetrafluoroethylene.

The installation surface of the rear power cup 9 is provided with a cable hole, and the cable of the finger probe 6 is processed by the floating magnetization detection block 5 and the probe hub and the combined cable and cable plug are inserted into the built-in detection device Connect the measurement and recording circuit to the cable socket at the exposed end of the electronic recorder.

The cable plug and cable socket are pressure-resistant underwater rubber plugs and sockets, the rubber material is NBR, and the underwater pressure resistance value is 0-20 MPa.

Compared with the fixed magnetization mandrel type detection device, the pipe passing capacity of the present invention is greatly increased, and can pass through pipes with larger deformation and smaller turning radius, and because the floating structure is lighter than the fixed magnetization mandrel structure, so It is more suitable for defect detection of offshore oil and gas pipelines with vertical pipe sections.

The invention realizes floating magnetization and detection, and the structure is a single floating type magnetic leakage detection device in a pipeline. Combining the drive function, magnetization measurement function, electronic recorder, battery pack, and stroke measurement device into a single device, the number and length of the detector section are simplified to the greatest extent. In the actual pipeline defect detection project, it is suitable for the operation requirements of small offshore platform and simple launch and recovery. The magnetic flux leakage detection device in the pipeline eliminates the attitude instability factors caused by the transition coupling connection existing in the multi-section structure, and the pipeline passing capacity is greatly enhanced.

Description of drawings

Fig. 1 is a developed sectional view of the present invention.

Fig. 2 is a schematic structural diagram of the floating magnetization detection block unit of the present invention.

FIG. 3 is a schematic structural diagram of the mileage wheel unit 10 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with accompanying drawings and embodiments, and an 18-inch (457 mm) floating submarine oil and gas pipeline defect high-precision internal detection device is used as an example for illustration.

The overall length of the 18-inch floating subsea oil and gas pipeline defect high-precision internal detection device is 871 mm, of which the length of the fixed body is 803 mm. The maximum diameter of the floating magnetization detection block 5 is 450 mm. The working diameter of the floating magnetization detection block 5 is 428 mm. The minimum shrinkage diameter of the detection block 5 is 320 mm, the maximum fixed body diameter of the detection device is 315 mm, and the overall weight of the detection device is 260 kg.

Referring to Figure 1, the 18-inch floating submarine oil and gas pipeline defect high-precision internal detection device includes a body support shaft 2, which is supported by the body support shaft 2. The front end of the body support shaft 2 is connected to the anti-collision head and the front power cup 1. The back of the bowl 1 is connected to the front floating hinge mechanism 3; the front floating hinge mechanism 3 hangs two sets of floating magnetization detection blocks 5, and each set of floating magnetization detection blocks 5 is equipped with lateral jacking springs 4 on the front and rear sides, and the floating magnetization is carried out by the jacking springs 4. The detection block 5 is opened to form a floating magnetization circuit and a magnetic flux leakage detection block unit; a finger probe 6 is installed on the floating magnetization detection block 5; in order to ensure the reliability of floating deformation of the floating magnetization detection block 5, the floating magnetization detection block 5 is structured The rear part of the body is a sliding form, and a guide groove and a limit ring are installed on the rear end of the body support shaft 2, which restricts the lateral swing and up and down movement of the floating magnetization detection block 5; the rear power cup is installed on the rear part of the guide groove 9. The front and rear power cups jointly form the power drive system of the detection device; the battery pack unit 7 and the electronic recorder 8 are respectively installed in the front and rear of the sealed cabin in the body support shaft 2, and the battery pack unit 7 and the electronic recorder 8 are respectively inserted. The electrode pair is plugged in to power on the electronic recorder 8; a detector mileage wheel unit 10 is installed at the tail of the body support shaft 2.

Referring to Fig. 2, the floating magnetization detection block 5 includes a magnetizer 19, the front twisted support shaft 11 is placed in the front end shaft hole of the magnetizer 19, the front winch 18 is fixed on the front end of the magnetizer 19 by an inner angle bolt, and the high-strength magnet 14 is placed on the magnetizer. The upper part of 19 is fixed by a magnetic pole protection plate 12, and the middle is protected by a magnetic pole shock absorber 13. The magnetic pole protection plate 12 is fixed on the front winch 18 and the magnetizer 19 with screws, and the finger probe twist support 15 is fixed on the magnetizer 19. The finger probe 16 is fixed on the finger probe twist support 15 by bolts, the probe hub 21 is installed under the finger probe 16, the inner stopper 17 of the magnetic pole is fixed behind the finger probe 16, and the wiring box 20 is fixed on the bottom of the magnetizer 19. The two sides of magnet 19 have crimping sheet 22 and spring seat hole 23, guide slide block 24 after the fixed afterbody of magnetizer 19, and each assembly forms a whole with magnetizer 19 as the center.

When the floating magnetization detection block 5 is attached to the metal pipe wall, the metal pipe wall, the front magnetic pole N pole, the magnetizer 19 and the rear magnetic pole S pole form a closed magnetic flux circuit, and the finger probe 16 is in the middle of the upper magnetic circuit. When there is a metal loss defect, the magnetic force line is distorted and deformed, and the detection value of the finger probe 16 in the middle of the magnetic circuit will change. By comparing with the detection value without defect, the shape and size of the metal loss defect can be obtained. Among them, the front and rear magnetic poles The surface of the magnetic pole protection plate is sprayed with magnetically conductive tungsten carbide powder for wear-resistant treatment, and the spraying thickness is 0.15-0.25mm. 0.20 mm.

Referring to FIG. 3 , the mileage wheel unit 10 is responsible for measuring and recording the mileage of the detector, and integrating the data from the magnetic flux leakage detection to give the position of the metal loss defect. The mileage wheel unit 10 includes a hinge base 25 , a tension spring 26 , a swing arm 27 , a rotary encoder 28 and a mileage wheel 29 . One end of the swing arm 27 is connected with the hinge seat 25 through a pin shaft, and the other end is equipped with a mileage wheel 29. The rotary encoder 28 is located in the shaft hole of the mileage wheel 29, and the tension spring 26 pulls up the swing arm 27, so that the mileage wheel 29 is compressed. The metal pipe wall moves in the pipeline with the detection device, the mileage wheel 29 rotates, the rotary encoder 28 records the rotation angle and the number of turns, and the mileage of the detection device is obtained by calculation.

The front floating hinge mechanism 3 is a double-pair structure, which is composed of a rotating sliding hinge arm and a rotating rocker, wherein the hinge shaft at the lower end of the hinge arm of the double-pair structure moves forward and backward in the sliding groove of the fixed winch seat, and the hinge shaft and the fixed winch seat The matching gap of the sliding groove is 0.50-1 mm. The fixed winch seat of the front floating hinge mechanism 3 is fixed on the installation position of the support shaft of the detector body through positioning flat keys and screws. The hinge arm of the double-pair structure is a U-shaped structure. The lateral gap between the hinge arm and the fixed winch is 0.50-1 mm. One end of the double-pair rocker rotates on the fixed winch, and the other end of the rocker is connected to the hinge arm. The fit is clearance fit, the clearance is 0.10-0.20 mm, and the lateral clearance between the rocker and the fixed winch is 0.50-1 mm. This structural design is different from the single hinge structure in that: when the hinge arm swings up and down, the forward and backward movement distance of the floating magnetization detection block unit is shortened, so that the length of the guide slider behind the floating block is reduced, and at the same time, the distance on the support shaft of the detection device is reduced. The thickness of the sliding limit groove ensures the connection strength and reliability of the detection device, and also controls and shortens the installation distance of the front and rear power cups of the detection device, so as to obtain good sealing performance of the detection device through right-angled bends and reduce the The power loss of the detection device when passing the curve ensures the ability of the detection device to pass through the curve.

The side of the floating magnetization detection block 5 is equipped with a lateral jacking spring support structure. Each group of floating magnetization detection blocks 5 cooperates with the front floating hinge mechanism 3 and the rear guide chute structure. The connection realizes the effect of floating up and down. Specifically, the lateral jacking spring seat hole is arranged on the side of the magnetizer, the jacking spring 4 presses the bottom surface of the spring seat hole, and the spring guide post is installed in the spring seat hole. The spring guide post and the spring seat hole The jacking-up spring 4 is double-guided and position-limited to prevent the jacking-up spring 4 from coming out, and a spring guide column is installed in the spring seat hole. The gap between the spring guide post and the inner diameter of the spring is 0.5-1 mm, and the gap between the spring seat hole and the outer diameter of the spring is 1-2 mm. The advantage of this design is that the floating block can better fit the pipeline wall, adapt to the local deformation of the pipeline, and improve the passing capacity of the detection device in the pipeline. In addition, the rear hinge rigid support is replaced by the side compressible jacking spring 4 support, which also strengthens the adaptability of the floating block under complex stress conditions in the pipeline, and greatly improves the structural strength of the detection device.

High-precision internal detection device for defects in submarine oil and gas pipelines. Each set of floating blocks cooperates with the front floating hinge mechanism 3 to have a sliding and limit structure at the rear end. 9 The front end is composed of a guide chute and a limit ring. When the floating magnetization detection block 5 is in motion, the bar-shaped slider slides up and down, forward and backward in the guide groove without falling out of the guide groove. The upper part of the guide groove is covered with a limit ring to limit sliding. The up and down travel of the block, thereby constraining the floating range of the floating magnetization detection block 5, the sliding lateral gap between the bar slider and the rear guide chute is 1 to 2 mm, and the bar slider is made of S304 stainless steel with passivation treatment on the surface ; The rear guide chute is made of tin bronze or manganese bronze. Such a structure enables the slider to obtain pitch within a certain angle range, so that the front and rear magnetic poles on the slider and the movable probe can better fit the pipe wall, achieving better detection results.

Stainless steel pressure plates are installed on the outside of the front power cup 1 and the rear power cup 9, and the front power cup 1 and the rear power cup 9 are pressed on the cup mounting surface of the detection device body support shaft 2 through connecting bolts. The installation distance between the front power cup 1 and the rear power cup 9 is 1 to 1.5 times the internal diameter of the pipeline used by the detection device.

The seal between the battery pack unit 7 and the internal sealing compartment of the body support shaft 2 adopts two seals in the end direction and the axial direction, the sealing medium is an O-shaped rubber seal ring, and the surface of the battery pack unit 7 cylinder is pasted with two seals at the front and back. Shock-absorbing belt, the material of the shock-absorbing belt is polytetrafluoroethylene.

The sealing between the electronic recorder 8 and the internal sealing compartment of the body support shaft 2 adopts two seals in the end direction and the axial direction, and the sealing medium is an O-shaped rubber sealing ring. Shock-absorbing belt, the material of the shock-absorbing belt is polytetrafluoroethylene.

The installation surface of the rear power cup 9 is provided with a cable hole, and the cable of the finger probe 6 is paralleled by the probe hub 21 of the floating magnetization detection block 5, and the synthesized cable and cable plug are inserted into the built-in Connect the measurement and recording circuit to the cable socket at the exposed end of the electronic recorder of the detection device. After the cable is passed through the cable hole, it is blocked with quick-drying silicone rubber to ensure that the front and rear of the power cup will not release pressure.

The cable plug and cable socket are pressure-resistant underwater rubber plugs and sockets, the rubber material is NBR, and the underwater pressure resistance value is 0-20 MPa.

Working principle of the present invention is:

The floating magnetization detection block 5 is attached to the metal pipe wall. At this time, the metal pipe wall, the front magnetic pole N pole, the magnetizer 19 and the rear magnetic pole S pole form a closed magnetic flux circuit, and the finger probe 6 is in the middle of the upper magnetic circuit. When the metal pipe wall When there is a metal loss defect, the magnetic force line is distorted and deformed, and the detection value of the finger probe 6 in the middle of the magnetic circuit will change. By comparing with the detection value without defect, the shape and size of the metal loss defect can be obtained. Finger probe 6 The cable is processed by the floating magnetization detection block 5 probe hub and the combined cable and cable plug are inserted into the cable socket at the exposed end of the electronic recorder 8 of the built-in detection device through this hole, and the measurement and recording circuit is connected; the detection device Relying on the fluid in the pipeline to push the front power cup 1 and the rear power cup 9 to move in the pipeline; the mileage wheel unit 10 moves in the pipeline with the detection device, and the mileage wheel 29 rotates to drive the rotary encoder 28 to rotate, thereby recording the angle and the number of turns , the moving mileage of the detection device can be obtained through calculation, so as to realize the location of the detection device and the detected pipeline defect.

Claims (10)

1. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy, comprise body back shaft (2), it is characterized in that: body back shaft (2) front end connects anti-raming and front power leather cup (1), floating hinge mechanism (3) before front power leather cup (1) connects below, front floating hinge mechanism (3) is detected block (5) with two groups of magnetization of floating and is connected, before and after often organizing magnetization detection block (5) side of floating, installation side is to jack-up spring (4), by jack-up spring (4) will float magnetization detect block (5) open, form relocatable magnetization cycle and Magnetic Flux Leakage Inspecting module unit, magnetization of floating detects block (5) and installs finger probe (6) above, the rear portion that magnetization of floating detects block (5) is slip form, install guiding groove and limited ring in the rear end of body back shaft (2), the floating magnetization of constraint detects sideshake and the amount of moving up and down of block (5), power leather cup (9) after the rear portion of guiding groove is installed, front and back power leather cup together form power-driven system, in body back shaft (2) before and after seal hatch respectively to slotting installation cell bag unit (7) and electronic recorder (8), the electrode pair of cell bag unit (7) and electronic recorder (8) is inserted and is powered on to electronic recorder (8), at body back shaft (2) afterbody, detector mileage wheel unit (10) is installed.

2. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: described floating magnetization detects block (5) and comprises magnet case (19), front twisted branch axle (11) is placed in magnet case (19) front end axis hole, front twisted seat (18) is fixed on magnet case (19) front end, high-strength magnet (14) is placed on magnet case (19) top, fixed by magnetic pole protection apron (12), middle use magnetic pole beam (13) protection, magnetic pole protection apron (12) is fixed on front twisted seat (18) and magnet case (19), finger probe twisted branch seat (15) is fixed on magnet case (19), finger probe (16) is fixed on finger probe twisted branch seat (15), finger probe (16) is equipped with probe Line concentrator (21) below, after magnetic pole internal stop (17) is fixed on finger probe (16), wiring casing (20) is fixed with in the bottom of magnet case (19), both sides live conductor sheet (22) of magnet case (19) and spring base hole (23), guide runner (24) after magnet case (19) afterbody is fixing, each assembly forms entirety centered by magnet case (19).

3. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: described mileage wheel unit (10) comprises swing arm (27), swing arm (27) one end is connected with hinge base (25) by bearing pin, the other end is provided with mileage wheel (29), rotating coder (28) is positioned at mileage wheel (29) axis hole, stretched spring (26) one end connects swing arm (27), the other end connects hinge base (25), stretched spring (26) is by swing arm (27) pull-up, make mileage take turns (29) and compress metal pipe-wall, move in pipeline with detection device.

4. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: described front floating hinge mechanism (3) is double-twisted structure, be made up of rotational slide hinge arms and rotating rocker, wherein double-twisted structure hinge arms lower end hinge is movable in the sliding-groove of fixing twisted seat, the matching gap of the sliding-groove of hinge and fixing twisted seat is 0.50 ~ 1 millimeter, the fixing twisted seat of front floating hinge mechanism (3) is fixed on the mounting point of body back shaft (2), the hinge arms of double-twisted structure is U-shaped structure, the sideshake of hinge arms and fixing twisted seat is 0.50 ~ 1 millimeter, rocking bar one end of double-twisted structure is rotated in fixing twisted seat, the other end and hinge arms are connected, the hinge axis hole at rocking bar two ends is Spielpassung with coordinating of hinge, gap is 0.10 ~ 0.20 millimeter, the sideshake of rocking bar and fixing twisted seat is 0.50 ~ 1 millimeter.

5. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: described floating magnetization detects the side installation side of block (5) to jack-up spring cupport structure, often group is floated to magnetize and is detected block (5) the front floating hinge mechanism (3) of cooperation and rear guide chute structure, side is with two groups, front and back jack-up spring (4) jack-up mutually, specifically at magnet case side arrangement side direction jack-up spring base hole, jack-up spring (4) holddown spring bore bottom surface, mounting spring directional post in spring base hole, spring directional post and spring base hole play two guiding and position-limiting action to jack-up spring (4), prevent jack-up spring (4) from deviating from, mounting spring directional post in spring base hole, spring directional post and spring inside diameter gap are 0.5 ~ 1 millimeter, the gap of spring base hole and spring outer diameter is 1 ~ 2 millimeter.

6. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: stainless steel platen is installed in described front power leather cup (1) and rear power leather cup (9) outside, be pressed on the leather cup attachment face of body back shaft (2) by front power leather cup (1) and rear power leather cup (9), the front and back mounting distance of front power leather cup (1) and rear power leather cup (9) is 1 ~ 1.5 times of application internal diameter of the pipeline.

7. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: the sealing of the interior seal hatch of described cell bag unit (7) and body back shaft (2) adopt hold to axial two seals form, sealing medium is O type rubber seal, cell bag unit (7) drum surface pastes front and back twice lanyard, and lanyard material is teflon.

8. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: the sealing of the interior seal hatch of described electronic recorder (8) and body back shaft (2) adopt hold to axial two seals form, sealing medium is O type rubber seal, electronic recorder (8) drum surface pastes front and back twice lanyard, and lanyard material is teflon.

9. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 1, it is characterized in that: described rear power leather cup (9) attachment face has cable passing hole, the cable of finger probe (6) detects through magnetization of floating the cable that synthesizes after block (5) probe Line concentrator doubling process and cable plug is inserted on the cable socket of built-in inspection electronic recorder bared end by this cable-through hole, connects and measures and record circuit.

10. detection device in sea-bottom oil-gas pipeline defect highi degree of accuracy according to claim 9, is characterized in that: described cable plug and cable socket are withstand voltage rubber plug under water, socket, and quality of rubber materials is nitrile rubber, and pressure resistance is 0 ~ 20 MPa under water.