Method for optical measurement of a thread at one end of a metal pipe or sleeve

Description

[0001] The invention relates to a method for optically measuring a thread, in particular for measuring an internal thread on a socket end of a metal pipe or in a socket.

[0002] 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. Optically measuring threads for pipe quality control is generally known in the art.

[0003] A method and a device for optically measuring the external thread profile of pipes is known, for example, from WO 2019 / 09371 A1.

[0004] WO 2012 / 069154 A1 discloses a method and device for inspecting the external thread of an oilfield tubular member. The method comprises a sensor mounted on a frame. The sensor is arranged on a threaded support whose thread is configured to match the thread of the tubular member and which encloses a portion of the conical thread of the tubular member to be inspected. The sensor is designed as a confocal sensor.

[0005] 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.

[0006] The arrangement known from WO 2020 / 232041 A1 is not readily suitable for pipes with a small inner diameter. The tactile centering of the measuring arrangement is complex and requires a relatively large amount of installation space. The field of view of the sensor 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 rotary 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 activator 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. It can be assumed that the complete acquisition of all distance information for imaging the thread requires a relatively long measuring time.

[0007] An arrangement for the optical measurement of bores with a small inner diameter, comprising at least one optical sensor, at least one further optical element which is adjustable relative to the optical sensor and which is arranged at a certain distance from the sensor in an optical axis and is designed to optically scan the inner diameter of the bore, is known, for example, from WO 2021 / 055736 A1.

[0008] Further prior art is known from the documents KR 101 368 486 B1, US 2015 / 292872 A1, EP 2 887 010 A1, WO 2016 / 000764 A1 and JP H10 142335 A.

[0009] The invention is based on the object of providing a method of the type mentioned above which enables optical measurement, in particular of undercut and / or conical internal threads on sockets of oil field pipes, with a relatively short measuring time and high accuracy.

[0010] The problem is solved by a method having the features of claim 1.

[0011] According to one aspect of the invention, the method according to the invention comprises the use of an arrangement for optically measuring a thread on one end of a metal pipe, in particular for measuring an internal thread on a socket end of a metal pipe or on a socket, comprising at least one optical sensor, at least one further optical element which is adjustable relative to the optical sensor and which is arranged at a specific distance from the sensor in an optical axis on an optical bench and is designed to optically scan the internal thread, and further comprising means for detecting and / or storing and / or evaluating the measurement data recorded by the sensor.

[0012] By combining the sensor with at least one additional optical element, small sensors in angled or straight designs can be used. It is particularly advantageous to provide a single straight sensor, which can, for example, be aligned along the optical axis of the system. In the arrangement according to the invention, the sensor and the additional optical element form a system.

[0013] In the arrangement according to the invention, it is provided that the optical bench and / or the frame are adjustable at least linearly in the longitudinal axis or parallel to a longitudinal axis of the metal tube.

[0014] The sensor is designed as a confocal sensor, specifically a confocal chromatic sensor. These sensors are small. By combining them with another optical element, this sensor can be designed in a straight configuration, for example, making the arrangement compact and allowing measurement of internal threads with a small inner diameter.

[0015] The sensor can, for example, be designed as a confocal displacement sensor. In a confocal chromatic measurement system, white light is split into its component wavelengths by a lens system, so that each wavelength is focused at a different, defined distance. Blue wave trains are focused close to the sensor, while red ones are focused further away. The reflected light is collected and analyzed interferometrically. The color of highest intensity corresponds to the respective focus and thus the distance of the sensor from the measurement point. By recording a large number of points or distances, a thread profile of the thread to be measured can be easily generated. Such a thread profile can be recorded and displayed two-dimensionally or three-dimensionally.

[0016] In the arrangement according to the invention, it is provided that the optical element comprises a mirror adjustable about at least one axis.

[0017] In the arrangement according to the invention, the optical element can comprise at least one, preferably two actuators, with which the mirror can be pivoted about one or the other axis. The mirror can, for example, be suspended on a double gimbal, with the gimbal frames each being adjustable by means of magnetic actuators.

[0018] In the arrangement according to the invention, the optical element is designed as a so-called galvo scanner, whose mirror 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.

[0019] The sensor expediently comprises a lens system and a control device that interferometrically evaluates the signals from the lens system. The sensor can be connected to the control device, for example, via suitable cabling, such as a fiber optic cable.

[0020] Advantageously, the optical bench and / or the frame is adjustable by means of at least one linear drive.

[0021] The arrangement may further comprise contactless means for centering the optical bench within the metal tube. Signal acquisition and processing can be performed using either single-channel or multi-channel means.

[0022] If the arrangement comprises at least one sensor angled by 90°, this sensor can be used to achieve internal centering of the arrangement within the metal tube.

[0023] The method for optically measuring a thread at one end of a metal pipe, in particular the method for measuring an internal thread at a socket end of a metal pipe or at a socket, comprises the following steps: A) Providing an optical system with at least one optical sensor and at least one further optical element, which are arranged along an optical axis at a specific distance from one another, B) Adjusting the optical system along the longitudinal axis of the metal tube or parallel to the longitudinal axis of the metal tube, preferably within the metal tube, or adjusting the metal tube relative to the stationary system along the longitudinal axis or parallel to the longitudinal axis of the metal tube, and C) Scanning the internal thread during a linear adjustment of the optical system and / or during a rotation of the optical element at an angle to the optical axis, and D) Capturing and / or storing and / or processing the measured values ​​captured by the sensor. With the method according to the invention, two internal threads of a metal tube or the two opposite internal threads of a sleeve can be measured in a single measuring run.

[0024] The thread can be scanned by the sensor over its length and / or over at least a partial circumference, wherein the sensor preferably detects distance values ​​which are converted into a two- or three-dimensional measurement image and which are correspondingly displayed in two or three dimensions.

[0025] The optical sensor preferably comprises an optically passive sensor comprising a lens system and a control device. The measurement signals received by the sensor are preferably fed to the control device, which performs an interferometric evaluation of the measurement signals. The data from the control device can be forwarded via an interface to a processing unit, for example, a computer (PC).

[0026] The method according to the invention provides that the optical sensor and the additional optical element, for example in the form of a mirror, form an optical axis. For example, during a linear adjustment of the optical sensor, the optical element can be adjustable about at least one, preferably two, preferably perpendicular axes, so that the entire thread can be scanned during a measuring run of the optical system. For this purpose, the optical sensor and the additional optical element are preferably arranged so as to be adjustable relative to one another along the optical axis.

[0027] The optical system comprises at least one galvo scanner scanner which scans at least a partial circumference of the internal thread during a linear adjustment of the optical system.

[0028] The contour of the threads is preferably recorded and / or displayed two-dimensionally and / or three-dimensionally.

[0029] In a particularly useful variant of the method, self-centering of the optical axis of the optical system is provided within the metal pipe or within the sleeve. During a measurement run, it can be provided that either the optical system is stationary and the sleeve or the sleeve end is moved over the system, or that the metal pipe or sleeve is stationary and the measuring sensor or optical system is adjusted relative to the longitudinal axis of the stationary metal pipe or the stationary sleeve.

[0030] In an advantageous and practical variant of the method according to the invention, a dark calibration of the sensor is provided. The dark calibration can be performed automatically, for example, by moving the sensor into a darkened housing.

[0031] Furthermore, sensor calibration can be provided using a reference component with known dimensions and a known thread profile. Furthermore, contamination of the optical system can be detected by comparing it with stored reference values ​​of the light signal intensity.

[0032] In a particularly advantageous variant of the method according to the invention, the measurement data acquired by the sensor are used to derive control commands for the control and / or regulation of a machine tool, for example, a CNC machine, which is designed to produce an internal thread on at least one end of a metal pipe or in a sleeve by machining. The arrangement can, for example, be arranged in a production line with a thread-cutting machine and be coupled to the control and regulation device of the thread-cutting machine.

[0033] Optical control commands can be, for example, the following: Tool wear detection and derived call for tool change Adjustment of the tool position in case of, for example, incorrect setting parameters or to compensate for tool wear Correction of the tools due to geometric arrangement of the cutting plates (e.g. if a step is visible after the tool change) Correction of the tools due to wear (e.g. if the cutting plates start to smear) Correction of the tools due to external influences (e.g. if the ambient temperature changes) Correction of the tools due to different blanks (e.g. if the material of the pipe changes or the wall thickness becomes larger or smaller) Tool wear detection in order to optimize the service life (e.g.when you coordinate cutting speed, cutting geometry, feeds and measurement results) Wear detection of the tools to predict tool breakage Wear detection of the tools to optimize tool inventory Wear detection of the tools to increase productivity (e.g. by replacing tools early and producing less scrap) Increase in productivity through cycle time optimization (e.g. you can see whether different functions bring the desired added value) Increase in productivity through improvement of the material flow (e.g. you can identify bottlenecks at other locations earlier and then change tools or carry out cleaning work) Increase in quality through early problem detection (e.g.If you measure certain vibrations in the thread cutting machine and then prevent them during the process, close the Lynette, or repeat the final cut, you can increase quality by comparing the measurement results with the torque on the sleeve wrench. You can increase quality by comparing the measurement results with the measurement results from other machines (NDT (non-destructive testing): in this case, magnetic particle testing).

[0034] The collected data can also be used for quality evaluation and documentation, as well as for downstream processes, and can be correlated with the data from these machines using, for example, appropriate control algorithms or AI. These downstream processes and correlations can include: Detection of sleeve contamination and differentiation from defects. Correlation of the measurement data with previously collected data, for example, to detect the origin of stresses in the sleeve that lead to ovality after threading. This may lead to an improvement in the quenching strategy. Increased quality by comparing the measurement results with the torque on the sleeve wrench. Increased quality by comparing the measurement results with the measurement results from other machines (NDT: in this case, magnetic particle testing).

[0035] Furthermore, the measuring device can have mechanical and / or optical collision protection.

[0036] To detect special thread contour zones (e.g. undercut contour), the sensor can be positioned at specific points within the internal thread and a partial area can be scanned with the galvo scanner.

[0037] According to the invention, multiple scans through the thread are performed with different angles of the light through the galvo mirror (e.g., 90° angle, then 100°, then 110°, or even 70° or 80°), and the curves of the measurement signals are superimposed. The goal is to measure each thread contour zone with a sufficiently strong light signal.

[0038] Although the invention according to claim 1 is based on the measurement of internal threads, it is apparent to the person skilled in the art that the measurement of external threads can also be provided.

[0039] The invention is explained below with reference to the accompanying drawings using an embodiment.

[0040] They show: Figure 1 shows a schematic representation of the arrangement according to the invention, Figure 2 shows the further optical element of the arrangement according to the invention as a so-called galvo scanner, Figure 3 shows a representation illustrating the arrangement of the optical element and the sensor relative to one another, Figure 4 shows a two-dimensional thread profile created on the basis of the measurement data of the arrangement, and Figure 5 shows a schematic representation of the arrangement in relation to a socket end of a metal pipe.

[0041] The Figure 1The arrangement 1 shown represents a test setup and comprises a frame 2 with an optical bench 3, which is linearly adjustable on a rail 4. A chromatic confocal sensor 5 and an optical element in the form of a galvo scanner 6 are arranged on an optical axis 7 on the optical bench 3. The galvo scanner 6 is designed as a mirror 9, which is doubly gimbal-mounted and can be adjusted in gimbal elements 10 about two axes aligned perpendicular to one another by means of actuators. The galvo scanner 6 and the optical sensor 5 are each adjustably arranged on holders 8 on the optical bench 3. The adjustability of the galvo scanner 6 and the optical sensor 5 serves the purpose of adjustment. During a measurement run, the distance between the optical sensor 5 and the galvo scanner 6 on the optical axis 7 can be fixed and constant.Conveniently, both the holder 8 for the galvo scanner 6 and the holder 8 for the optical sensor are adjustable in height in the sense of adjustability perpendicular to the optical axis 7.

[0042] The Galvo scanner 6 is shown schematically in Figure 2 , from which it can be seen that it has a circular mirror 9 with a relatively small diameter, which is pivotally mounted in two cardan elements 10.

[0043] Figure 3 shows the relative arrangement of the optical sensor 5 and the galvo scanner 6 in the optical axis 7 of the system.

[0044] Figure 4 shows a two-dimensional measurement record of a recording resulting from a measurement run along the longitudinal axis of a metal pipe 11 (see Figure 5 ) was obtained.

[0045] How this Figure 5As can be seen, for example, the metal tube 11 with an internal thread 12 can be arranged in a stationary manner in a measuring stand (not shown), while the optical bench 3 is moved on the guide rail 4 into the interior of the metal tube 11 and records measurement data of the internal thread 12 during a linear movement of the optical bench 3. The mirror 9 of the galvo scanner can be aligned at a specific angle to the optical axis 7. Alternatively or additionally, it can be provided to adjust the mirror 9 relative to the longitudinal axis of the metal tube 11 during a measuring run in order to scan a partial circumference of the internal thread 12.

[0046] Although the example described above refers to a metal pipe 11 with a socket end, the invention is to be understood in such a way that the method can also be carried out on a socket with two oppositely arranged internal threads.

[0047] It is also readily apparent to the person skilled in the art that the process can also be carried out on an external thread.

[0048] As the combination of Figures 4 and 5 As can be seen, the internal thread 12 is designed as a conical internal thread with undercut thread flanks.

[0049] The measurement data acquired by the arrangement 1 or by the optical sensor 5 are fed to the control device designated 13, which performs an interferometric evaluation of the optical signals. The control device 13 forwards the evaluated distance data to software running on a computer 14 for the purpose of displaying a two- or three-dimensional profile. A digital twin of the metal pipe 11 to be measured can be displayed on the computer 14. List of reference symbols

[0050] 1Arrangement 2Frame 3Optical bench 4Track 5Optical sensor 6Galvo scanner 7Optical axis 8Holder 9Mirror 10Cardan elements 11Metal tubes 12Internal thread 13Control device 14Computer

Claims

1. Method for optical measurement of an internal thread (12) at a sleeve or a sleeve end of a metal tube (11), wherein the method comprises the following steps: A) providing an optical system with at least one optical sensor (5) and at least one further optical element, which are arranged on an optical axis (7) at a defined mutual spacing, B) adjusting the optical system in the longitudinal axis of the metal tube (11) or the sleeve or parallelly to the longitudinal axis of the metal tube (11) or the sleeve, preferably within the metal tube (11), or adjusting the metal tube (11) relative to the system, which is arranged in a fixed location, in the longitudinal axis or parallelly to the longitudinal axis of the metal tube (11) or the sleeve, C) scanning the internal thread (12) during a linear adjustment of the optical system and / or during a rotation of the optical element at an angle to the optical axis (7) and D) detecting and / or storing and / or processing the measurement values detected by the sensor, characterised in that the optical system comprises at least one galvo-scanner (6), which during a linear adjustment of the optical system scans at least a part circumference of the internal thread (12), and multiple scanning of the internal thread by the galvo-scanner with different anglings of the light is provided and the signals of a plurality of scans are superimposed.

2. Method according to claim 1, characterised in that the contour of the thread flights is detected and / or illustrated.

3. Method according to one of claims 1 and 2, characterised in that self-centring of the optical axis (7) within the metal tube (11) or within the sleeve is provided.

4. Method according to any one of claims 1 to 3, further comprising darkness calibration of the sensor.

5. Method according to any one of claims 1 to 4, characterised by sensor calibration with a reference component.

6. Method according to any one of claims 1 to 5, characterised by a contamination check by comparison of the light intensity signals detected by the optical sensor.

7. Method according to any one of claims 1 to 6, characterised in that the measurement data detected by the sensor are used for derivation of control commands for control and / or regulation of a machine tool which is constructed for producing an internal thread (12) at at least one end of at least one metal tube (11) or in a sleeve by material-removal processing.

8. Method according to any one of claims 1 to 7, characterised by use of an arrangement (1) for optical measurement of a thread, particularly for measurement of an internal thread (12) at a sleeve or a sleeve end of a metal tube (11), comprising at least one optical sensor (5), at least one further optical element, which is adjustable relative to the optical sensor (5) and which is arranged at a defined spacing from the sensor on an optical axis (7) on an optical bank (3) and constructed for optical scanning of the internal thread (12), as well as comprising means for detecting and / or storing and / or evaluating the measurement data, which are recorded by the sensor, of the arrangement (1), further comprising at least one frame (2) which receives the optical bank (3), wherein the optical bank (3) and / or the frame (2) is or are adjustable at least linearly in the longitudinal axis or parallelly to a longitudinal axis of the metal tube (11), the sensor is constructed as a confocal sensor, the optical element comprises at least one mirror (9) adjustable about at least one axis, preferably about two axes, and the optical element is constructed as a galvo-scanner.