Method, measuring arrangement and system for measuring an internal contour, in particular an internal thread on a sleeve or a sleeve end of a pipe

Abstract

The invention relates to a method for measuring an internal thread (2) on a sleeve or an sleeve end of a pipe (1) using a measuring arrangement having at least two sensors (3, 4), wherein the measuring arrangement comprises a first inner sensor (3) and at least a second outer sensor (4), wherein the first inner sensor (3) and the second outer sensor (4) are arranged at least radially at a defined distance from each other with respect to a longitudinal axis of the pipe (1), wherein the measuring arrangement is arranged in relation to the sleeve or the sleeve end of the pipe (1) such that the first sensor (3) detects the inside of the pipe (1) and that the second sensor (4) detects the outside of the pipe (1), wherein the method comprises the first sensor (3) scanning the internal thread (2) at least in a first measurement pass along a first measurement path parallel to a longitudinal axis of the pipe (1), wherein the measurement signals of the second outer sensor (4) determine the outside diameter of the pipe (1) as a reference for the measurement signal of the first sensor (3), and wherein the detected measurement values are stored and / or processed using means for electronic data processing for the purpose of mapping a thread profile. The invention also relates to a measuring arrangement and to a system for carrying out the method.

Description

[0001] Method, measuring arrangement and system for measuring an internal contour, in particular an internal thread on a socket or socket end of a pipe

[0002] The invention relates to a method for measuring an internal contour, in particular an internal thread on a socket or a socket end of a pipe. The invention further relates to a measuring arrangement for measuring an internal contour, in particular an internal thread on a socket or a socket end of a pipe, in particular for carrying out the method, as well as to a measuring system for measuring an internal contour, in particular an internal thread on a socket or a socket end of a pipe, which is designed in particular for carrying out the method and which comprises a measuring arrangement of the type described above.

[0003] Pipes used to transport pressurized fluids, such as natural gas or crude oil, which are bolted together in a pressure-tight, gas-tight, and liquid-tight manner, must meet stringent tightness requirements. For such OCTG pipes, such as casing pipes or riser pipes for oil or natural gas exploration wells or natural gas or crude oil production pipelines, conical threads with undercut thread flanks are typically used. A sealing lip is typically attached to the thread at the end of the pipe. Both the thread and the sealing lip must meet the highest precision requirements. Optical measurement of threads for pipe quality control is generally known in the art.

[0004] In principle, measuring external pipe threads is straightforward, as the external thread is easily accessible from the outside and can be measured both non-contact and with tactile sensors. Measuring internal threads is more difficult due to their poor accessibility. In this case, it is generally known to measure threads using tactile measuring instruments, such as thread gauges or probe pins.

[0005] Internal thread measurement on pipes with a relatively small diameter, for example, less than 100 mm, is particularly difficult because the inside diameter of the pipe only allows for the insertion of a single sensor. Determining the inside diameter, which is required to map the thread profile, requires the acquisition of at least two, ideally three, measuring points. If non-contact optical sensors are to be used to scan the internal thread, the relatively short distance between the sensor and the thread inside the pipe also poses problems.

[0006] Furthermore, internal thread measurement is often fraught with the difficulty that the inner diameter of the pipe is not always concentric with the outer diameter, particularly due to the manufacturing process, for example, in the case of seamless rolled pipes. Therefore, internal thread measurement requires determining the inner diameter, or rather the position of the inner diameter relative to the outer diameter.

[0007] A method and a device for optically measuring the external thread profile of pipes is known, for example, from WO 2019 / 09371 A1.

[0008] WO 2012 / 069154 A1 discloses a method and a device for inspecting the external thread of an oilfield pipe. The device comprises a sensor mounted on a frame, and the sensor is arranged on a threaded support whose thread is configured to match the thread of the pipe and which encloses a portion of the conical thread of the pipe to be inspected. The sensor is designed as a confocal sensor.

[0009] WO 2020 / 232041 A1 also discloses a device for measuring threads on oilfield tubulars. The device comprises a sensor unit configured to measure a distance between the sensor and a portion of the thread of the metal pipe. The sensor or sensor unit is adjustable radially and axially with respect to the internal thread of the metal pipe using a plurality of actuators, wherein a control device can generate a three-dimensional image of the internal thread from a plurality of distance measurements. The sensor unit comprises a confocal chromatic sensor, which is inserted into the metal pipe on a rod assembly and is centered within the metal pipe by means of sensing rollers.After concentric alignment of the guide rod of the rod, the sensor is adjusted both translationally and rotationally within the metal tube, whereby the thread is scanned and a three-dimensional image of the thread is generated using the measurement data thus obtained.

[0010] The arrangement known from WO 2020 / 232041 A1 is not readily suitable for pipes with a small inner diameter. Tactile centering of the measuring arrangement is complex and requires a relatively large amount of installation space. The sensor's field of view is aligned at a predetermined angle to the longitudinal axis of the metal pipe, and the rod to which the sensor is attached can be actuated by means of three different actuators: one actuator for the rotational movement of the rod about its own longitudinal axis, one actuator for a rotational movement of the rod about the longitudinal axis of the metal pipe, and one actuator for a linear movement of the rod within the metal pipe, i.e., parallel to the longitudinal axis of the metal pipe. Scanning undercut and / or conical threads is difficult with this arrangement.CN 112871737 A discloses a non-contact, sensor-based measurement method for internal threads in pipes. The method initially determines the position of the symmetry axis of the external thread and the position of the symmetry axis of the internal thread relative to that of the external thread. For this purpose, CN 112871737 A proposes rotating the pipe to be measured around its own axis using a sensor aligned longitudinally along the pipe, thereby measuring the axial offset. Alternatively, the pipe can be clamped and the relative position of the axes determined in a centering device by adjusting the clamp accordingly. The internal thread is detected by guiding the optical sensor along the previously determined longitudinal axis of the pipe's internal diameter.

[0011] This process is relatively complex.

[0012] The invention is based on the object of providing a method, a measuring arrangement, and a system that enable optical, non-contact measurement of the internal thread on pipes, particularly on metal pipes with a small inner diameter. In particular, the method should be designed so that it can be carried out with only one sensor on the inside of the pipe.

[0013] The object is achieved by providing a method having the features of claim 1 and by providing a measuring arrangement having the features of claim 11. Furthermore, according to the invention, a measuring system having the features of claim 13 is provided.

[0014] Advantageous embodiments of the invention emerge from the subclaims. A first aspect of the invention relates to a method for measuring an inner contour, in particular an internal thread on a socket or socket end of a pipe using a measuring arrangement with at least two sensors, wherein the measuring arrangement comprises a first inner sensor and at least one second outer sensor, wherein the first inner sensor and the second outer sensor are arranged at least radially with a defined distance from each other with respect to a longitudinal axis of the pipe, wherein the measuring arrangement is arranged with respect to the socket or socket end of the pipe such that the first sensor detects the inside of the pipe and the second sensor detects the outside of the pipe, wherein the method comprisesThe first sensor scans the internal thread at least in a first measurement run along a first measurement path parallel to a longitudinal axis of the pipe, wherein the measurement signals of the second outer sensor determine the outer diameter of the pipe as a reference for the measurement signal of the first sensor, and wherein the recorded measurement values ​​are stored and / or processed using electronic data processing means for the purpose of mapping a thread profile. The recorded actual thread profile is preferably compared with a target thread profile in a further method step, so that the pipe can be rejected if its dimensions are outside specified tolerances.

[0015] The term internal thread in the sense of the invention also includes threadless sections of the socket, in particular a sealing lip provided on OTCG pipes.

[0016] The measurement of the internal thread can, in particular, be coupled with an automated thread-cutting process of a machine tool. For example, the method according to the invention can utilize a preferably closed control loop between the machining of the metal pipe and the thread measurement, whereby, advantageously, a direct evaluation and derivation of control commands for the machine tool takes place based on the comparison of the recorded actual thread profile with a desired thread profile.

[0017] A control device for evaluating and deriving control commands, provided for example in a machine control system of the machine tool, can comprise at least one self-learning algorithm for deriving the control commands.

[0018] In principle, the pipe can be rotated around its longitudinal axis during a measurement run. With precise rotation of the pipe around its longitudinal axis, exactly two sensors, positioned inside and outside at a defined distance from each other, are sufficient to determine the pipe's contour.

[0019] In the method according to the invention, it is provided to establish a metrological reference to the outer diameter of the pipe for measuring the internal thread of the pipe, so that the internal thread of a socket or a pipe can be measured with only a single sensor inside the pipe.

[0020] In order to fully describe the internal thread, the thread fine structure including the tooth height, the tooth width, the flank angle, the rounding angle and the pitch is precisely determined according to the invention.

[0021] For this purpose, provision can be made to clearly and precisely define the exact position of the internal thread in space, i.e. also the position of the internal diameter in relation to the external diameter of the pipe. For this purpose, at least three measuring points are advantageous. This can be achieved, for example, with two sensors when the pipe is rotated about its longitudinal axis. Preferably, an internal sensor and a plurality of external sensors are provided, which are preferably mechanically connected to one another and have a precisely defined radial distance from one another. According to the invention, the external diameter of the pipe determined by the external sensor system forms a reference for the measurement signal of the internal sensor. Preferably, the measuring arrangement comprises at least one third external sensor, which likewise has a defined radial distance from the first and second sensors and which likewise detects the outside of the pipe.By recording three measuring points on the outer circumference of the pipe, a mathematically exact description of the circular surface of the pipe is possible.

[0022] However, the method can also be carried out with satisfactory results if only two measuring points are recorded on the outer circumference of the pipe.

[0023] The inner sensor and the outer sensors are preferably moved parallel to each other in the longitudinal direction of the pipe during a measuring run.

[0024] The measuring arrangement can be designed such that the radial distance between the inner and the outer sensor(s) is changed according to the taper of the socket during a measuring run in the longitudinal direction of the pipe. This ensures that the sensors are spaced apart accordingly on each pipe cross-section over the length of a measuring section so that the measurement can be carried out with appropriate accuracy. For example, the distance of the sensors can be calibrated at the beginning and end of a provided reference section, for example on a reference object. During a measuring run on the pipe to be measured, the radial distance between the sensors, i.e. the distance between the inner sensor and that of the at least one outer sensor, can be adjusted. Preferably, the radial distance between the outer sensors is also adjustable.The inner sensor and / or the at least one outer sensor can be moved radially.

[0025] The measuring arrangement according to the invention preferably comprises a measuring head movable relative to the pipe. The measuring head can, for example, comprise at least two sensors or measuring arms with sensors arranged on the outer circumference of the pipe, which are adjusted in the manner of a fork or pliers by means of at least one linear drive to vary the distance between the inner sensor and the outer sensors.

[0026] In a preferred variant of the method according to the invention, it is provided that in at least one second measuring run, the internal thread of the pipe is scanned along a second measuring section parallel to the longitudinal axis of the pipe, wherein the second measuring run is carried out along a measuring section with an angular offset relative to the circumference of the pipe.

[0027] The internal thread can be measured using a plurality of measurement runs, each with an angular offset relative to the pipe circumference. Preferably, two measurements are performed with an angular offset of 180° relative to the pipe circumference. Alternatively, three measurement runs can be performed with an angular offset of 120 degrees.

[0028] The method preferably includes the step of calibrating the radial distance between all sensors, for example, using a reference object. The reference object can be a sample pipe or test specimen with dimensions within a defined tolerance.

[0029] Furthermore, it can be provided to trace the conical inner contour of the pipe in parallel by moving a calibrated, fixed measuring range of the inner and outer sensors within the area of ​​a measuring window of the outer sensor. By rotating the sensor while simultaneously measuring over the entire or partial circumference of the pipe, structures caused, for example, by the pipe's manufacturing process can be resolved. In seamlessly rolled pipes, for example, hexagonal wall thickness structures can be observed, which are still visible even after a thread cut and can impair the quality of the socket and / or pipe.

[0030] In principle, the method can be carried out using an internal optical sensor and one or more tactile external sensors. Preferably, however, at least the first and second sensors are optical sensors selected from a group of sensors comprising laser scanners, sensors designed for laser triangulation, laser micrometers or light band micrometers, telecentric measuring arrangements with at least one light-sensitive sensor, for example, a CMOS or CCD sensor, and at least one light source for backlighting an object to be measured, as well as confocal displacement measuring sensors, in particular confocal chromatic displacement measuring sensors.

[0031] An optical sensor in the sense of the present invention is also understood to mean an arrangement of several optical elements in a measuring section.

[0032] According to the invention, for example, the first inner sensor can be designed as a confocal chromatic displacement sensor, whereas two second outer sensors can be designed, for example, as light section sensors.

[0033] The inner sensor can, for example, be designed in combination with another optical element, for example in the form of a mirror adjustable about at least one axis, so that an elongated internal sensor can be arranged inside the tube, which extends parallel to the longitudinal axis of the tube and which, with the mirror, enables scanning of the inner wall of the tube at a right angle to the longitudinal axis of the tube. The optical element can be designed as a so-called galvo scanner, the mirror of which is rotatable and pivotable relative to the optical axis, so that at least a partial circumference of the internal thread of the metal tube can be optically scanned. The signal detected by the mirror of the optical element is transmitted to the sensor along the optical axis of the arrangement.

[0034] The measuring arrangement according to the invention, which is preferably designed to carry out the method, expediently comprises a first optical inner sensor and at least two second outer, preferably optical sensors, which are arranged at a defined and preferably calibrated distance from one another, wherein the arrangement is arranged to be movable linearly and along a measuring axis over a defined measuring distance and to be rotatable about the measuring axis during a measuring run.

[0035] The radial distance between the sensors is preferably adjustable, further preferably by means of at least one electromotive actuator, so that in particular the arrangement of the second outer sensors relative to one another can be adjusted with respect to the nominal diameter of the pipes to be measured.

[0036] A measuring system for measuring an internal thread on a socket or a socket end of a pipe, which is designed, suitable, and intended for carrying out the method, comprising at least one frame that accommodates an optical bench with a measuring arrangement of the type described above, wherein the optical bench and / or the frame are adjustable at least linearly in the longitudinal axis or parallel to a longitudinal axis of the pipe by means of at least one drive, and with at least one data processing and data storage device with which the thread profile of the internal thread can be partially or completely displayed. In particular, it is provided to compare the detected or measured internal thread profile with target data of a reference model stored in the data processing device.

[0037] The invention is explained below using an embodiment shown in the drawings.

[0038] They show:

[0039] Figure 1 is a schematic representation of the measuring principle according to the invention,

[0040] Figure 2 is a highly simplified schematic representation of the measuring arrangement according to the invention and

[0041] Figure 3 is a representation according to Figure 2, in which the measuring arrangement is rotated by 180°.

[0042] Figure 1 shows a highly simplified representation of a socket end of a pipe 1 with an internal thread 2, which is scanned by a first inner sensor 3 and two second outer sensors 4. The pipe 1 is designed as a metal pipe, for example, as a seamless rolled metal pipe with a conical internal thread, and for the sake of simplicity, is shown only in a very schematic manner. The first inner sensor 3 and the second outer sensors 4 are part of a measuring arrangement shown only schematically in Figures 2 and 3 and can be a component of a measuring head that is movable along a measuring axis 6 of a measuring section in the direction of the arrow shown in Figure 1, parallel to the longitudinal axis of the pipe 1, and is arranged to rotate about the corresponding axis. The terms "inside" and "outside" in this context refer to the position of the sensors 3, 4 during the measuring process or in a position ready for measurement in relation to the pipe 1.By means of the second outer sensors 4, which are arranged on diametrically opposite sides of the outer casing 5 of the metal pipe 1, the outer diameter of the pipe 1 is recorded as a reference for the measurement signal of the first inner sensor 3. The first inner sensor 3 is moved into the pipe 1 over a predetermined distance along the measuring axis 6 during a measurement run and in doing so scans the internal thread of the pipe 1 optically, i.e. without contact. During a measurement run, the first inner sensor 3 and the outer sensors 4 are moved in parallel, i.e. each aligned radially opposite one another over the same cross-section of the pipe 1. The sensors 3 and 4 are arranged at a fixed axial and radial distance from one another in a measuring arrangement shown schematically in Figures 2 and 3.

[0043] As indicated in Figure 1, the first inner sensor 3 can be designed as a confocal sensor with a further optical element in the form of a mirror 7, so that the sensor 3 can have a radiation source aligned in the direction of the measuring axis 6, which is deflected by the mirror 7 at an adjustable angle, so that scanning of the internal thread 2 of the tube 1 is possible in a relatively small installation space.

[0044] However, the inner sensor 3 can also be designed as a laser scanner or as another measuring device for detecting the inner contour of the pipe 1 with a different measuring characteristic.

[0045] The measuring arrangement shown in the drawings is designed with two measuring channels. Those skilled in the art will recognize that the measuring arrangement can have more than two channels, thereby increasing the measurement accuracy.

[0046] The arrangement shown in Figures 2 and 3, for example, shows two diametrically opposed outer sensors 4, each having a telecentric lens with a light-sensitive sensor (receiver), for example a CMOS or a CCD sensor. A light source 8 is arranged opposite each of the light-sensitive sensors, generating a projection of a portion of the outer surface 5 of the pipe 1 onto the light-sensitive sensor 4. The use of telecentric lenses ensures that the projection detected by the respective sensor 4 can be recorded undistorted and true to scale. The measurement data thus acquired by the second outer sensors 4 are used to determine the outer diameter of the pipe 1 in relation to the distance to the internal thread 2 or to the inner surface of the pipe 1, as determined by the inner sensor 3.

[0047] In a further measurement, which is shown schematically in Figure 3, the measuring arrangement is rotated by 180° and the first inner sensor 3 scans the internal thread 2 of the pipe 1 at the diametrically opposite point in relation to the outer diameter of the pipe 1 determined by the second outer sensors 4. All sensors 3, 4 have a precisely defined radial distance from one another, which was preferably calibrated using a test specimen before the start of the measurement. The measuring arrangement comprising the first inner sensor 3 and the second outer sensors 4, which are arranged together on a rotatable measuring head, was rotated completely from the position shown in Figure 2 to the position shown in Figure 3 in the described embodiment, whereby a measurement can be carried out intermittently at specific angular positions or continuously during the rotational movement of the arrangement of sensors 3 and 4.

[0048] The entire arrangement can be moved back and forth linearly in the direction of the longitudinal axis of the pipe 1 and can also be rotated about the longitudinal axis of the pipe 1. In this case, it can be provided that both the radial distance and the axial distance between the sensors 3 and 4 are fixed and cannot be changed, at least during the measuring runs. If the conicity of the pipe 1 in the area of ​​the socket exceeds a certain amount, it can be advantageous to adjust at least one of the sensors 3, 4 during the measuring runs, i.e. to adjust it radially in a defined manner via a linear guide in order to increase the measuring range of the sensors 3, 4. The radial distance between the second outer sensors 4 can also be designed to be variable, for example to adapt to different pipe diameters.

[0049] List of reference symbols

[0050] 1 pipe 2 internal thread

[0051] 3 first inner sensor

[0052] 4 second outer sensors

[0053] 5 Outer jacket

[0054] 6 Measuring axis 7 Mirror

[0055] 8 Light source

Claims

Patent claims 1. A method for measuring an inner contour, in particular an internal thread (2), on a socket or socket end of a pipe (1) using a measuring arrangement with at least two sensors (3, 4), wherein the measuring arrangement comprises a first inner sensor (3) and at least one second outer sensor (4), wherein the first inner sensor (3) and the second outer sensor (4) are arranged at least radially with a defined distance from one another with respect to a longitudinal axis of the pipe (1), wherein the measuring arrangement is arranged with respect to the socket or socket end of the pipe (1) such that the first sensor (3) detects the inside of the pipe (1) and the second sensor (4) detects the outside of the pipe (1), wherein the method comprises the first sensor (3) scanning the inner contour at least in a first measuring run along a first measuring section parallel to a longitudinal axis of the pipe (1),wherein the measurement signals of the second outer sensor (4) determine the outer diameter of the pipe (1) as a reference for the measurement signal of the first sensor (3), and wherein the recorded measurement values ​​are stored and / or processed by means for electronic data processing for the purpose of imaging a thread profile.

2. Method according to claim 1, characterized in that the pipe (1) is rotated at least about its longitudinal axis during a measuring run.

3. Method according to one of claims 1 or 2, characterized in that the measuring arrangement comprises at least one second outer sensor (4) and further preferably at least one third outer sensor (4) which is arranged at a defined radial distance from the first inner sensor (3) and which detects the outside of the pipe.

4. Method according to one of claims 1 to 3, characterized in that the radial distance between the inner sensor (3) and at least one outer sensor (4) is varied during at least one measuring run depending on a conicity of the sleeve.

5. Method according to one of claims 1 to 4, characterized in that in at least one second measuring run the internal thread (2) of the pipe (1) is scanned along a second measuring section parallel to the longitudinal axis of the pipe, wherein the second measuring run is carried out along a measuring section with an angular offset relative to the circumference of the pipe (1).

6. Method according to claim 5, characterized in that the angular offset of the measuring sections is at least 180, preferably 120 degrees.

7. Method according to one of claims 1 to 6, characterized by the step of calibrating the radial distance of the sensors (3, 4) from one another.

8. Method according to claim 7, characterized in that the calibration is carried out using a reference object.

9. Method according to one of claims 1 to 8, characterized in that the measuring arrangement is rotated with respect to the pipe (1) between at least two measuring runs.

10. The method according to one of claims 1 to 9, characterized in that at least the first and second sensors (3, 4) are optical sensors selected from a group of sensors comprising laser scanners; sensors designed for laser triangulation; laser micrometers or light band micrometers; telecentric measuring arrangements with at least one light-sensitive sensor (CMOS or CCD) and at least one light source 8 for backlighting an object to be measured, and confocal displacement measuring sensors, in particular confocal chromatic displacement measuring sensors. 11 . Measuring arrangement for measuring an inner contour, in particular an internal thread (2), on a socket or a socket end of a pipe (1), in particular for carrying out the method according to one of claims 1 to 10, wherein the measuring arrangement comprises a first optical inner sensor (3) and at least one outer, preferably two optical sensors (4) which are arranged at a defined radial distance from one another, wherein the arrangement is arranged to be movable linearly and along a measuring section defined in a measuring axis (6) during a measuring run and to be rotatable about the measuring axis (6).

12. Measuring arrangement according to claim 11, characterized in that the distance between the sensors (3,4) is adjustable, preferably by means of at least one electromotive actuator.

13. Measuring system for measuring an internal contour, in particular an internal thread (2) on a socket or a socket end of a pipe (1), in particular for carrying out the method according to one of the Claims 1 to 10, comprising at least one frame which accommodates an optical bench with a measuring arrangement according to one of claims 11 or 12, wherein the optical bench and / or the frame are adjustable at least linearly in the longitudinal axis or parallel to a longitudinal axis of the tube (1) by means of at least one drive, and with at least one data processing and data storage device.

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