APPARATUS AND METHOD FOR INSPECTING AN INNER WALL SURFACE OF A PIPE

Abstract

Device for inspecting an inner wall surface of a metal tube having a linear drive, an elongated probe holder and an eddy current probe. The eddy current probe is mounted on probe holder and the probe holder is operatively connected to linear drive in such manner that probe holder is movable together with eddy current probe in an axial feed direction through tube to be tested when device is in operation.

Claims

1. A device for inspecting an inner wall surface of a metal tube, comprising: a linear drive; an elongated probe holder; and an eddy current probe, wherein the eddy current probe is mounted on the probe holder, wherein the elongated probe holder is operatively connected to the linear drive such that the elongated probe holder with the eddy current probe will be movable in an axial feed direction through the metal tube to be tested during operation of the device, and wherein an elastically deformable scraper (5) wiper, which surrounds the probe holder in a circumferential direction, is arranged on the probe holder in front of the eddy current probe in the axial feed direction for scraping off chips or other impurities from an inner wall surface of the tube.

2. The device according to the preceding claim 1, wherein the wiper is an O-ring.

3. The device according to claim 1, wherein the device comprises at least one inlet sleeve, wherein the inlet sleeve is arranged such that the tube is arranged concentrically with the inlet sleeve and is receivable in the device with a first end of the tube in contact with the inlet sleeve, and wherein an inner diameter of an inner wall surface of the inlet sleeve and an outer diameter of the wiper are adapted to each other such that wiper forms a contact surface with the inlet sleeve extending along an entire circumference of the inner wall surface of the inlet sleeve.

4. The device according to claim 3, comprising a centering guide, wherein the centering guide is designed and arranged in such manner that, when the tube is fed into the device, the tube can be received in the centering guide in such manner that the centering guide comes into contact with an exterior wall surface of the tube and thus centers the inner wall surface of the tube and the inner wall surface of the inlet sleeve.

5. The device according to claim 4, comprising a stop, wherein the stop is arranged such that a second end of the tube will be in contact with the stop in the device, and wherein the inlet sleeve and the stop are movable relative to each other in and against the feed direction so that the tube can be clamped between the inlet sleeve and the outlet sleeve.

6. The device according to claim 5, comprising a motor-driven infeed device, wherein the infeed device is arranged in such a manner that, while the device is being operated, the infeed device moves the inlet sleeve and the stop relative to one another in and against the feed direction, and wherein the infeed device comprises a sensor configured such that, while operating the device, the sensor detects a measure of a distance between the infeed sleeve and stop after the tube has been clamped between the infeed sleeve and stop.

7. The device according to claim 5, wherein the stop comprises a discharge sleeve, wherein an inner diameter of an inner wall surface of the outlet sleeve and an outer diameter of the wiper are adapted to each other such that the wiper forms an annular contact surface with the inlet sleeve, and wherein the inlet sleeve and the outlet sleeve are arranged and configured such that the tube is receivable in the device concentrically to the inlet sleeve and to the outlet sleeve (9) and between the inlet sleeve and the outlet sleeve.

8. The device according to claim 7, wherein the device comprises a latch, wherein the latch is arranged such that the latch fixes the tube after feeding between the inlet sleeve and the stop and before clamping the tube between the inlet sleeve and the stop.

9. The device according to claim 8, wherein at least the inlet sleeve or the outlet sleeve comprises a reference section of an electrically conductive material with a reference structure for calibrating the eddy current probe.

10. The device according to claim 9, wherein at least one of the inlet sleeve and the outlet sleeve comprises a cylindrical marking portion having an inner wall portion made of a non-conductive material, the marking portion extending, when the tube to be tested is received in the device, between the reference portion and the tube to be tested.

11. The device according to claim 1, comprising a controller, wherein the controller is operatively connected to the eddy current probe such that the controller receives an eddy current measurement signal from the eddy current probe while operating the device, and wherein the controller is arranged to emit an error signal when the eddy current measurement signal exceeds or drops below a predetermined threshold value.

12. An unit for assembling a tube made of metal, comprising: a cutting device for cutting a length of tube from a continuous tube; and the device according to claim 1.

13. A system, comprising: the unit according to claim 12; a device for forming a chamfer on at least one end face of the tube; a chamfer testing device for testing the chamfer; and a system controller, wherein the chamfer testing device includes at least a portion of a taper surface and a stop surface, wherein the chamfer testing device is set up in such manner that the portion of the taper surface can be advanced towards a first end face of the tube received in the chamfer testing device, while a second end face of the tube is in contact with the stop face, wherein the chamfer testing device includes a sensor configured to measure a distance between the portion of the taper surface and the stop surface, wherein the system controller is operatively connected to the sensor of the infeed device in such manner that during operation of the device the system controller receives a length measurement signal from the sensor of the infeed device, the length measurement signal representing a measure of the distance between the infeed sleeve and the stop and thus during operation of the system representing a measure of an absolute length of the tube received between the infeed sleeve and the stop, wherein the system controller is operatively connected to the sensor of the chamfer testing device such that the system controller receives a chamfer measurement signal from the sensor while operating the device, the chamfer measurement signal representing the distance between the portion of the taper surface and the stop surface, and wherein the system controller calculates an actual measurement for a quality of the chamfer based on the length measurement signal and the chamfer measurement signal while operating the device.

14. A method of inspecting an inner wall surface of a tube made of metal, comprising the steps of moving an eddy current probe in an advancing direction through the tube; detecting an eddy current induced in a wall of the tube from an inner wall surface by means of the eddy current probe; and scraping chips or other impurities from the inner wall surface of the tube by means of an elastically deformable scraper arranged upstream of the eddy current probe in the advancing direction and while contacting the tube in an annular manner, wherein the scraping occurs at least in sections simultaneously along with the detecting of the eddy current.

15. The device according claim 3, wherein at least the inlet sleeve or the outlet sleeve comprises a reference section of an electrically conductive material with a reference structure for calibrating the eddy current probe.

16. The device according to claim 15, wherein at least one of the inlet sleeve and the outlet sleeve comprises a cylindrical marking portion having an inner wall portion made of a non-conductive material, the marking portion extending, when the tube to be tested is received in the device, between the reference portion and the tube to be tested.

Description

SHORT DESCRIPTION OF THE FIGURES

[0071] Further advantages, features and potential applications of the present disclosure will become apparent with reference to the following description of an embodiment and the accompanying figures. The foregoing general description and the following detailed description of embodiments will be better understood when read in conjunction with the accompanying drawings. The embodiments shown are not limited to the exact arrangements and devices shown. In the figures, like elements are designated by like reference signs.

[0072] FIG. 1 is a schematic cross-sectional view of a device for inspecting the inner wall surface of a tube in accordance with a variant of the present disclosure.

[0073] FIG. 2 is a schematic block diagram of a system for producing a tube using the device for inspecting the inner wall surface of a tube shown in FIG. 1.

[0074] FIG. 3 is a schematic cross-sectional view of the chamfer testing device of the system shown in FIG. 2.

DETAILED DESCRIPTION

[0075] FIG. 1 is a schematic cross-sectional view of a variant of device 1 for testing an inner wall surface 2 of a tube 3. The tubes to be tested are stainless steel tubes for high pressure applications such as liquid hydrogen guidance.

[0076] Device 1 comprises an eddy current probe 4, a stripper 5, a probe holder 6, a linear drive 7, an inlet sleeve 8, an outlet sleeve 9, and a controller 10.

[0077] Probe holder 6 is elongated in the form of a tube section and extends through inlet sleeve 8 into tube 3 to be tested. Probe holder 6 serves as a carrier for eddy current probe 4 and wiper 5. Probe holder 6 can be moved automatically and motor-driven in a feed direction 11 and against feed direction 11 by means of linear drive 7 shown only schematically in FIG. 1.

[0078] During testing of the tube 3, an excitation coil in the eddy current probe 4 generates an eddy current in the electrically conductive stainless-steel material of tube 3. The induced eddy current in turn radiates an alternating magnetic field, which is detected by means of a detector coil in eddy current probe 4. In the even that the wall of tube 3 shows a defect, the electrical conductivity of the material of tube 3 changes at the position of the defect. The induced eddy current and thus the radiated magnetic field changes compared to the non-defective material of tube 3.

[0079] During an eddy current test, the control unit 10, which is connected to linear drive 7, ensures that probe holder 6 will be advanced in the direction of advance 11, and control unit 10 simultaneously receives a measurement signal from eddy current probe 4. If the eddy current measurement signal falls below a predefined threshold value, control unit 10 assumes the presence of a defect in the wall of tube 3 and emits an error signal. This error signal can, for example, be forwarded to a higherlevel system control system so that tested tube 3 will be ejected as defective from the tube producing system.

[0080] Simultaneously with the eddy current inspection by means of eddy current probe 4, inner wall surface 2 of tube 3 will be cleaned by means of scraper 5. Any impurities on inner wall surface 2 of tube 3 will be scraped off and removed from tube 3.

[0081] In one variant, device 1 is oriented vertically so that feed direction 11 points in the direction of gravity. This facilitates the conveying of impurities out of tube 3.

[0082] Wiper 5 is implemented as an O-ring made of a fluor rubber. The O-ring is accommodated in an annular groove in the probe holder. Wiper 5 is mounted on probe holder 6 upstream of eddy current probe 4 in feed direction 11. To achieve its cleaning effect, the O-ring has is oversized relative to the inner diameter of tube 3. That is, when not inserted into the tube and fully relaxed, O-ring 5 has an outer diameter which is slightly larger than the inner diameter of tubes 3 to be tested. Due to its own elasticity, the O-ring, when inside tube 3, presses against the inner wall surface 2 of tube 3. The O-ring then forms an annular contact surface with inner wall surface 2 of tube 3.

[0083] On the other hand, however, the oversize of O-ring 5 compared to the inner diameter of tube 3 makes it difficult to insert sensor holder 6 using the eddy current probe and wiper 5 into the tube. Therefore, device 1 exhibits inlet sleeve 8 and outlet sleeve 9.

[0084] These sleeves 8, 9 have the same inner diameter as tube 3. Both inlet sleeve 8 and outlet sleeve 9 have cylindrical inner wall surfaces 18, 19 inside of them. Since end face 12 of a first end 13 of tube 3 is in contact with an end face 14 of inlet sleeve 8 during the test, wiper 5 can be moved from inlet sleeve 8 into tube 3 without any interruption, starting from inlet sleeve 8. The same applies to the outlet from tube 3 to be tested at the second end 15 of tube 3, where end face 16 of tube 3 is in contact with end face 17 of outlet sleeve 9.

[0085] Tube 3 is received in the device in such a manner that inner wall surface 2 is concentric with inner wall surfaces 18, 19 of inlet sleeve 8 and outlet sleeve 9. Since inlet sleeve 8 and outlet sleeve 9 have the same inner diameter of their inner wall surfaces 18, 19 as inner wall surface 2 of the tube, inlet sleeve 8 and outlet sleeve 9 form an extension of inner wall surface 2 of tube 3.

[0086] In order to be able to clamp tube 3 between infeed sleeve 8 and outfeed sleeve 9 for the test, infeed sleeve 8 can be moved automatically in relation to outfeed sleeve 9 in and against the feed direction 11. After tube 3 has been fed between inlet sleeve 8 and outlet sleeve 9, inlet sleeve 8 is motor-driven towards outlet sleeve 9 until it clamps the tube between end faces 14, 17 of inlet sleeve 8 outlet sleeve 9.

[0087] Since the position of outlet sleeve 9 in device 1 is fixed and constant, the position of its end face 17 is also fixed. Knowing the position of end face 17, the absolute length of tube 3 being tested can be determined after determining the position of inlet sleeve 8 or its end face 14 along its feed path 20.

[0088] In this case, control 10 is set up in such a way that when inlet sleeve 8 has reached end face 12 of tube 3 to be tested, it determines an absolute length of tube 3 from the position of inlet sleeve 8. Control 10 outputs an error signal if the absolute length of tube 3 is outside the tolerance for the target value of the absolute length of tubes 3 to be tested. When integrated in a system for producing tubes as schematically outlined in FIG. 2, this error signal causes tested tube 3 to be rejected as defective, preferably before the actual testing with eddy current probe 4.

[0089] In the depicted variant, inlet sleeve 8 is largely made of plastic and outlet sleeve 9 is made entirely of plastic. Therefore, eddy current probe 4 does not show any characteristic signal in the area of inlet sleeve 8 and outlet sleeve 9, and the beginning and end of the test specimen in the form of tube 3 can be clearly determined from the eddy current measurement signal of eddy current probe 4.

[0090] However, inlet sleeve 8 has an annular insert as reference section 21. This reference section 21 is made of metal. Its inner wall surface 22 shows an engraving 23 as a reference structure. This engraving 23 leads not only to a change in the surface structure of ring 21, but also to a change in the microstructure, so that the eddy current measurement signal is changed in a controlled manner in the area of the engraving. Hence, engraving 23 to calibrate eddy current probe 4. Since reference section 21 is integrated into inlet sleeve 8, calibration of eddy current probe 4 can be performed before testing each tube 3.

[0091] Inlet sleeve 8 has a marking section 36 made of plastic between reference section 21 and tube 3 to be tested. If eddy current probe 4 experiences a translational movement starting from inlet sleeve 8, calibration of eddy current probe 4 occurs in the area of reference section 21, and by marking section 36 comprising the wall of electrically non-conductive material, a signal appears indicating that signals from tube 3 to be tested will follow next.

[0092] FIG. 2 illustrates in a block diagram the integration of device 1 for checking inner wall surface 2 of tube 3 of FIG. 1 into a system 24 for assembling tubes 3.

[0093] In addition to device 1 for inspecting the inner wall surface of the tube, system 24 comprises the following additional processing stations in the order listed: A cut-off bench 25 is used to cut individual tubes 3 from a provided seamless continuous tube. An end face lathe 26 is for forming a chamfer 27 on an edge between end face 12 and inner wall surface 2 of respective tube 3. In addition, system 24 has a wet cleaning device 28, an outer cleaning device 29 for cleaning the exterior wall surface of respective tube 3 before device 1 for inspecting respective tube 3, and a chamfer testing device 30, an inner drying device 31 for drying inner wall surface 2, and an outer drying device 32 for drying the exterior wall surface of the respective tube after device 1 for inspecting. The individual stations of system 24 are controlled by a system controller 33.

[0094] FIG. 3 schematically shows chamfer testing device 30 of system 24 of FIG. 2. Chamfer testing device 30 comprises at least a truncated cone 34 with a truncated cone surface and a stop surface 35. Truncated cone 34 can be fed onto stop surface 35 and thus onto a first end surface 12 of a tube 3 received in chamfer testing device 30. At the same time, a second end surface 16 of tube 3 is in contact with stop surface 35. Chamfer testing device 30 also has a sensor that detects distance between conic section 34 and stop surface 35. System controller 33 receives the length measurement signal from the sensor of the infeed device of device 1 to inspect the tube's inner wall surface, and a chamfer measurement signal from the sensor of chamfer inspection device 30. From the length measurement signal and the chamfer measurement signal, system controller 33 determines an actual measurement for a quality of chamfer 27.

[0095] For purposes of the original disclosure, reference is made to the fact that all features which are apparent to a person skilled in the art on the basis of the present description, the drawings and the claims, even if they have been specifically described only in conjunction with certain additional features, may be combined both individually and in any combination with other features or groups of features disclosed herein, unless this has been expressly excluded or unless technical circumstances render such combinations impossible or impractical. For the sake of brevity and readability of the description, a comprehensive, explicit presentation of all conceivable combinations of characteristics will not be provided below.

[0096] While the invention has been illustrated and described in detail in the drawings and the foregoing description, this illustration and description are merely illustrative and are not intended to limit the scope of protection as defined by the claims. The invention shall not be limited to the disclosed embodiments.

[0097] Any variations of the disclosed embodiments would be obvious to those skilled in the art based on the drawings, the description, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “one” or “a” does not exclude a plurality. The mere fact that certain features are claimed in different claims does not preclude their combination. Reference signs in the claims are not intended to limit the scope of protection.

REFERENCE LIST

[0098] 1 Device [0099] 2 Inner wall surface of the tube [0100] 3 Tube [0101] 4 Eddy current probe [0102] 5 Scraper [0103] 6 Probe holder [0104] 7 Linear actuator [0105] 8 Inlet sleeve [0106] 9 Outlet sleeve [0107] 10 Control [0108] 11 Feed direction [0109] 12 Face of the tube [0110] 13 First end of the tube [0111] 14 Face of the inlet sleeve [0112] 15 Second end of the tube [0113] 16 Face of the tube [0114] 17 Face of the outlet sleeve [0115] 18 Inner wall surface of the inlet sleeve [0116] 19 Inner wall surface of the outlet sleeve [0117] 20 Feed route [0118] 21 Reference section [0119] 22 Interior wall surface [0120] 23 Engraving [0121] 24 Fabrication system [0122] 25 Cut-off bench [0123] 26 Face lathe [0124] 27 Chamfer [0125] 28 Wet cleaning device [0126] 29 Exterior cleaning device [0127] 30 Chamfer testing device [0128] 31 Interior drying device [0129] 32 Outdoor drying device [0130] 33 System controller [0131] 34 Truncated cone [0132] 35 Stop surface [0133] 36 Marking section