Patent Publication Number: US-2022228849-A1

Title: Rotatable inspection device for defect detection

Description:
FIELD OF THE INVENTION 
     The present invention relates to an inspection device for defect detection during inspection of threads of axisymmetric portions of parts such as tubes, pipes, bolts, bolt holes or threaded joints. In an application of particular interest, the invention relates to an inspection device for inspecting the integrity of a conical threaded portion of a cylindrical part, notably a drilling pipe of a drill string. The inspection device may also be used to inspect non-threaded portions of drilling pipes, such as stress relief grooves and welds. The present invention also relates to a defect inspection device comprising a remote monitoring unit configured to be in wireless communication with the rotatable inspection device. 
     DESCRIPTION OF RELATED ART 
     Drill pipes are subject to significant stresses that lead to fatigue cracks in the threads. Poor handling and use can also result in other types of defects such as galling of the threads or other area such as seals, and alteration to the tread geometry (pulled threads, over-torqued threads). Defects of threaded portions are also worsened by washout, which also causes specific alterations of the tread. 
     Breakage of the drill pipe inside the wells generates large financial losses, not to mention the environmental consequences caused by a change in drilling location. To avoid this problem, non-destructive testing (NDT) methods such as visual inspection, magnetoscopy or die penetrant inspection are used to ensure that faulty pipes are removed from service before the defects exceed a specified threshold size. 
     The drill pipes are screwed together by a conical thread. In the majority of cases, the rupture is in one of the two threaded portions. Other critical regions are stress relief zones, grooves and welds. 
     Magnetoscopy inspection involves creating an intense magnetic flux inside a ferromagnetic material. When a defect is present in its path, the magnetic flux is deflected and creates a leak which, by attracting colored or fluorescent magnetic particles, provides a particular signature of the defect. 
     Die penetrant inspection uses the capillary properties of materials to reveal defects of non-porous materials. 
     These inspection methods have the disadvantage of requiring thorough cleaning of the tubes as well as rigorous preparation of the surfaces inside the threads. The preparation and inspection time of the tubes are therefore relatively long and thus represent a significant cost. 
     An aim of the present invention is therefore to provide a rotatable inspection device for rapid inspection of axisymmetric portions of parts in general and in particular for the inspection of threaded portions of drill pipes. 
     Another aim of the present invention is to provide a rotatable inspection device which accurately detects defects in threaded portions of tubes in general and in particular in treaded portions of drill pipes. 
     Another aim of the present invention is to provide a rotatable inspection device for handheld inspection, that can be used both at a pipe storage location and on the rig. 
     Another aim of the present invention is to provide a rotatable inspection device which may adapt to different sizes and types of threaded portion of tubes. 
     Another aim of the present invention is to provide a rotatable inspection device connected to a hand-held drive unit for rapid and repeatable inspection. 
     A further aim of the present invention is to provide a defect inspection device comprising a remote monitoring unit in wireless communication with an electronic device of the rotatable inspection device. 
     BRIEF SUMMARY OF THE INVENTION 
     These aims are achieved, according to an aspect of the invention, by a rotatable inspection device for inspection of the integrity of an axisymmetric portion of parts, for example a threaded tube. The inspection device includes a measuring unit configured to be rotated about the symmetry axis of the axisymmetric portion. The measuring unit comprises:
         a radially movable measuring structure comprising a defect detection sensor, said measuring structure being configured to urge the defect detection sensor against said portion to be inspected,   an electronic device for processing and transmitting the signal measured by the defect detection sensor along said portion, and   a measuring unit support supporting the radially movable measuring structure.       

     The electronic device is configured to wirelessly transmit the processed signal to a remote monitoring unit. 
     In an embodiment, the radially movable structure comprises at least one biased arm. The defect detection sensor is mounted at a distal end of the at least one biased arm. 
     In an embodiment, the axisymmetric portion is a threaded or non-threaded portion of a tube. The at least one biased arm is configured to urge the defect detection sensor against the threaded portion or non-threaded portion to be inspected. 
     In an embodiment, the electronic device comprises a battery, a transmitter and a signal processing unit including an A/D converter for converting the analog signal measured by the defect detection sensor into a digital signal to be sent to the remote monitoring unit. 
     In an embodiment, the radially movable measuring structure comprises a first, a second and a third biased arm. The defect detection sensor is mounted at a distal end of the first biased arm while a first and a second guiding elements are mounted at a distal end of the second and third biased arms respectively. 
     In an embodiment, the first, second and third biased arms are arranged at 120 degrees from each other with respect to the rotation axis of the measuring unit support. 
     In an embodiment, a proximal end of each of the first, second and third biased arms is pivotally mounted on a supporting base which is connected or forms an integral part with the measuring unit support. 
     In an embodiment, each of the first, second and third biased arms is biased by an elastic member, preferably in the form of a flexion spring. 
     In an embodiment, the rotatable inspection device is configured to inspect the integrity of a helical thread of a threaded portion located on an inner surface of a threaded tube. The elastic member is arranged to urge the distal ends of the first, second and third biased arms outwardly against the threaded portion. 
     In an embodiment, the rotatable inspection device is configured to inspect the integrity of a helical thread of a threaded portion located on an outer surface of a threaded tube. The elastic member is arranged to urge the distal ends of the first, second and third biased arms inwardly against the threaded portion. 
     In an embodiment, each of the first, second and third biased arms is kinematically linked to a manually operable part. The manually operable part is slidably mounted on a manually operable sliding portion of the measuring unit support. 
     In an embodiment, the first, second and third biased arms are pivotally actuated by the sliding movement of the manually operable part along said sliding portion to move together their respective distal end inwardly in a direction towards the rotation axis of the measuring unit support or outwardly in a direction opposite the direction towards said rotation axis. 
     In an embodiment, the sensor(s) and guiding element(s) are offset from each other with respect to the rotation axis of the measuring unit support by P/N, where P is the pitch of a helical thread of a threaded portion to be inspected and N the total number of guiding elements and sensing elements. 
     In an embodiment, the rotatable inspection device further comprises a measuring unit driving shaft to rotate the measuring unit about the axis of rotation of the rotatable inspection device. The measuring unit support comprises an axial passage receiving a linear-motion bearing through which the measuring unit driving shaft passes. 
     In an embodiment, the rotatable inspection device further comprises a drive unit connected to the measuring unit driving shaft. 
     In an embodiment, the rotatable inspection device further comprises an anchoring unit configured to secure the measuring unit to the threaded or non-threaded part to ensure rotation of the measuring unit coaxially with the axis of the thread or with the axis of the axisymmetric portion during an inspection of said portion. 
     In an embodiment, the anchoring unit comprises an anchoring actuator and an anchoring device configured to be fitted into a receiving section of the threaded or non-threaded part. The anchoring device comprises at least one an extendable member configured to secure a static part of the anchoring device to the receiving section, and a rotatable part comprising an axial passage along which a distal portion of the measuring unit driving shaft is fixedly fitted. 
     In an embodiment, the anchoring actuator comprises a rod extending through an axial passage of the measuring unit driving shaft and a rod displacement actuator configured to move the rod into a first and a second axial position. The at least one extendable member is in a non-extended configuration in which the anchoring device may be fitted into the receiving section of the threaded or non-threaded part when said rod is in the first axial position, and wherein the at least one extendable member is brought into an extended configuration in which the anchoring device is bound to the receiving section through the at least one extendable member when said rod is moved from the first to the second axial position. 
     In an embodiment, the measuring unit comprises an angular sensor configured to measure the angle between the measuring unit and the drive unit. 
     In an embodiment, the measuring unit comprises a linear position or displacement sensor configured to measure the position between the linear-motion bearing and the measuring unit driving shaft. 
     In an embodiment, the measuring unit comprises an angular sensor configured to measure the angle between the measuring unit and the axisymmetric portion. 
     In an embodiment, the measuring unit comprises an angular sensor configured to measure the angle between the measuring unit and the direction of gravity. 
     Another aspect of the invention relates to a defect inspection device comprising the rotatable inspection device as described above and a remote monitoring unit configured to be in wireless communication with the electronic device of the rotatable inspection device. The remote monitoring unit comprises a display unit for displaying information relative to the integrity of the thread and/or of the axisymmetric portion of the part. 
     In an embodiment, said information is displayed on the remote monitoring unit in real-time when the rotatable inspection device is inspecting said axisymmetric portion. 
     In an embodiment, the remote monitoring unit is a portable device such as an electronic tablet or a Smartphone. 
     Another aspect of the invention relates to a method for inspection of the integrity of a helical thread located on an inner surface of a threaded tube. The method comprises the following steps: 
     a) inserting, at least partly, the radially movable measuring structure of the rotatable inspection device as described above into a threaded portion of the threaded tube such the defect detection sensor is fitted into the helical thread, 
     b) rotating a measuring unit driving shaft passing through an axial passage of the measuring unit support to move the defect detection sensor along the helical thread, and 
     c) wirelessly transmitting an inspection signal to a remote monitoring unit while the defect detection sensor is moving along the helical thread. 
     In an embodiment, the radially movable measuring structure comprises three pivotable arms comprising each biasing means to urge their respective distal end outwardly. The defect detection sensor is mounted at the distal end of one pivotable arm while a first and a second guiding elements are mounted at a distal end of the other two pivotable arms respectively. Step a) of the method consists of:
         pivoting the pivotable arms together to move their distal end inwardly in direction of the central axis of the threaded tube in order to fit the distal ends into the threaded portion, and   releasing the pivotable arms to move their respective distal end outwardly under the action of their respective biasing means in order to press the defect detection sensor and the first and second guiding elements against the helical thread.       

     In an embodiment, an anchoring device is fitted into a receiving section of the cylindrical part before step b). 
     In an embodiment, the angular and/or linear positions of the measuring unit are measured by an angular and/or a linear position sensor(s) during an inspection of the integrity of the helical thread. The angular and/or linear positions of the measuring unit is/are correlated to the data measured by the defect sensor data in these positions in order to create a map of the defects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood with the aid of the description of several embodiments given by way of examples and illustrated by the figures, in which: 
         FIG. 1 a    shows a front-perspective view of a rotatable inspection device according to an embodiment of the invention; 
         FIG. 1 b    shows a back-perspective view of  FIG. 1   a;    
         FIG. 2  shows a side view of  FIG. 1   a;    
         FIG. 3  shows a side view of the rotatable inspection device of  FIG. 1 a    about to be inserted into a box portion of a drill pipe; 
         FIG. 4  shows a detailed view of the radially movable measuring structure of the rotatable inspection device; 
         FIG. 5  shows an axial cross-sectional view of the rotatable inspection device of  FIG. 1 a    during an inspection of a conical inner thread; 
         FIG. 6  shows a back-perspective view of  FIG. 5 ; 
         FIG. 7  shows a top view of the measuring unit support of the rotatable inspection device of  FIG. 1   a;    
         FIG. 7 a    shows a cross-sectional view of  FIG. 7  along the line A-A; 
         FIG. 8  shows a side view of the drive shaft and the tube anchoring unit of the rotatable inspection device of  FIG. 1 a   , when the tube anchoring unit is in a non-anchoring configuration; 
         FIG. 8 a    shows a partial cross-sectional view of  FIG. 8  along the line A-A; 
         FIG. 9  shows a similar view of  FIG. 8 , when the tube anchoring unit is in a non-anchoring configuration; 
         FIG. 9 a    shows a partial cross-sectional view of  FIG. 9  along the line A-A; 
         FIG. 9  shows a cross-sectional view of  FIG. 8 a    along the line B-B when the tube anchoring unit is in an anchoring configuration; 
         FIG. 10  shows a perspective view of the rotatable inspection device comprising a drive unit; 
         FIG. 11  shows a perspective view of the radially movable measuring structure of the rotatable inspection device according to another embodiment; 
         FIG. 12 a    shows a perspective view of the radially movable measuring structure of the rotatable inspection device according to a further embodiment; 
         FIG. 12 b    shows an elevation view of  FIG. 12 a   , and 
         FIG. 13  shows a block diagram of the electronic device receiving a signal from the defect detection sensor of the rotatable inspection device and a remote monitoring unit in communication with the electronic device. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION 
     In an exemplary embodiment, the rotatable inspection device, as illustrated particularly in  FIGS. 1 a  and 1 b   , is configured for inspecting the integrity of an axisymmetric portion in the form of a conical inner thread of a threaded portion  210  of a tube  200  as shown in  FIG. 3 . The axisymmetric portion within the context of the invention must therefore be interpreted as including helically symmetric portions. 
     The rotatable inspection device  10  may however be adapted to inspect the integrity of a helical thread of a threaded portion of a tube where the helical thread is disposed in an inner cylindrical portion (not illustrated). The tube  200  may be, in particular, a drill pipe configured to be part of a drill string. According to another exemplary embodiment of the invention, as illustrated in  FIG. 9 , the rotatable inspection device may be adapted to inspect the integrity of an outer thread such as the treaded portion of a bolt  250  or the pin tool joint of a drilling pipe, as described subsequently. Non-threaded portions of drilling pipes, such as stress relief grooves and welds may also be inspected by the rotatable inspection device according to the invention. 
     The rotatable inspection device  10  comprises a measuring unit  20  and a tube anchoring unit, as described in detail subsequently, configured to secure the measuring unit  20  to the tube  200  ( FIG. 3 ) in order to stabilize the rotation of the measuring unit  20  about the center axis of the tube  200  during an inspection of the helical thread. 
     As particularly shown in  FIG. 1 a   , the measuring unit  20  comprises an electronic device  43  and a radially movable measuring structure  22  which advantageously may be adjusted to different types of tubes having different diameters and different helical thread profiles. The radially movable measuring structure  22  is optimized to inspect a very broad range of diameters, enabling the inspection of threads with very small diameters and threads with large diameters with the same rotatable inspection device  10 . 
     In this respect, the radially movable measuring structure  22  comprises several pivotable arms, preferably three pivotable arms  22   a ,  22   b ,  22   c  which are pivotally mounted at their respective proximal end on a supporting base  34 . The supporting base  34  is fixedly mounted around a supporting base receiving portion  52  of a measuring unit support  50  as shown in  FIGS. 5 and 7   a . The supporting base may however form an integral part with the measuring unit support  50  according to a variant. The pivotable arms  22   a ,  22   b ,  22   c  are pivotably mounted at 120 degrees from each other with respect to the rotation axis of the measuring unit support  50  (see  FIGS. 1 a    and  5 ). 
     A defect detection sensor  30  is mounted on a sensor support  32  which is connected to the distal end of one pivotable arm  22   a . The defect detection sensor  30  may be for example a Hall-effect sensor, an Eddy current sensor, an ultrasonic sensor, or a Magnetic Flux Leakage sensor (MFL sensor). A guiding element  26   a ,  26   b  is mounted on a guiding element support  28  connected to the distal end of each of the two other pivotable arms  22   b ,  22   c.    
     The defect detection sensor  30  is connected to the electronic device  43  through an electrical wire  33  ( FIG. 2 ). The electronic device  43  comprises a signal processing unit  44  and a battery  47  which are both mounted on an electronic device holder  48  fixed at one end of the measuring unit support  50 . The signal processing unit  44  and the battery  47  are diametrically opposed with respect to the rotation axis of the measuring unit support  50 . The electronic device may however be mounted on the radially movable measuring structure  22  according to a variant. 
     Referring to  FIG. 13 , the signal processing unit  44  of the electronic device  43  comprises an A/D converter  45  to convert the analog signal, transmitted by the defect detection sensor  30  through the electrical wire  33 , into a digital signal in order to notably remove the noise generally introduced by analog signal transmissions. The electronic device  43  further comprises a transmitter  46  configured to transmit the digital signal to a remote monitoring device  300  through a wireless transmission, for example through a Bluetooth or WIFI protocol. 
     The remote monitoring unit  300  comprises a receiver  310  for receiving the digital signal and a display unit  320  for displaying information relative to the integrity of a threaded or non-threaded portion which is inspected. Such information may be displayed for example in real-time on the remote monitoring unit  300  when the rotatable inspection device  10  is inspecting the integrity of the helical thread. 
     Advantageously, the remote monitoring unit  300  may be a portable device such as an electronic tablet or a Smartphone. A dedicated software application may be downloaded on the tablet or Smartphone for displaying the integrity data of the inspected helical thread measured by the defect detection sensor  30  in a readable format. The integrity data may be stored locally or transmitted to a cloud-hosted remote database. 
     The pivotable arms  22   a ,  22   b ,  22   c  are biased to push their respective distal end outwardly to respective resting positions when the rotatable inspection device  10  is not in an operating mode. An elastic member, preferably in the form of a tension spring  24  ( FIGS. 1 a    and  5 ), is connected to the supporting base  34  and to each pivotable arm  22   a ,  22   b ,  22   c  in order to achieve the biasing function to ensure that the defect detection sensor  30  and the guiding elements  26   a ,  26   b  are fitted and pressed against the helical thread  210  when the radially movable measuring structure  22  is placed into the tube  200  to be inspected and the pivotable arms  22   a ,  22   b ,  22   c  are released for an inspection of the helical thread. 
     The configuration of the elastic members  24  has been determined to ensure that the defect detection sensor  30  applied a sufficient radial force against the surface of the threaded portion, preferably in the order between 1 N to 5 N, in order to ensure low lift-off of the defect detection sensor  30  when the latter moves along the thread during an inspection to probe any defect of the threaded portion of the tube  200 , even in the presence of grease residues, drilling fluid or other non-metallic contaminants. 
     Each pivotable arm  22   a ,  22   b ,  22   c  has an articulated parallelogram configuration whose axes of rotation have been offset to ensure that the defect detection sensor  30  and the guiding elements  26   a ,  26   b  are oriented according to the radial axis of the tube  200  irrespective of the diameter of the tube and the positions of the defect detection sensor  30  and the guiding elements  26   a ,  26   b  along the helical path of the conical threaded portion. 
     As particularly shown in  FIGS. 7 and 7   a , the measuring unit support  50  comprises an axial passage  58  along which is arranged two linear bearings  56  and a bearing spacer  57  therebetween. A single linear bearing may be used if such bearing is stiff enough. Referring to  FIG. 5 , the rotatable inspection device  10  comprises a measuring unit driving shaft  60  fitted inside the linear bearings  56  and configured to slide along said bearing  56  when the inspection device is in an operating mode. 
     Accordingly, the measuring unit support  50  may be freely displaced along the measuring unit driving shaft  60  while being driven in rotation by the driving shaft  60  via the linear bearing  56 . This specific driving arrangement of the measuring unit support  50  has the advantage to make the rotatable inspection device  10  adaptable to monitor different configurations of threaded portion  210  since it is the helical thread profile which imparts both the linear movements to the radially movable measuring structure  22  and the pivoting movements to the pivotable arms  22   a ,  22   b ,  22   c.    
     The radially movable measuring structure  22  comprises a radially movable measuring structure actuator configured to bring this structure into a compact configuration. To that effect, each pivotable arm  22   a ,  22   b ,  22   c  is kinematically connected to a manually operable part  40  slidably mounted on an operable part sliding portion  54  of the measuring unit support  50 . The kinematic connection is achieved through three cables  44 . As shown in  FIG. 1 a   , these cables  44  are connected to respective pivotable arm  22   a ,  22   b ,  22   c  and run through three apertures of a cable guiding ring  38  and corresponding through-holes  35  of the supporting base  34  to be anchored to the manually operable part  40 . 
     The cable guiding ring  38  is fixedly mounted around the supporting base receiving portion  52  of the measuring unit support  50  against a portion of the supporting base  34 . The three apertures of the cable guiding ring  38  and the corresponding through-holes  35  of the supporting base  34  are located at 120 degrees from each other. The cable guiding ring  38  is oriented around the supporting base receiving portion  52  to align each aperture with the corresponding through hole  35  of the supporting base  34  as particularly shown in  FIG. 5 . 
     According to the above configuration, when the operable part  40  is manually actuated in a direction opposite the supporting base  34  along the operable part sliding portion  54  of the measuring unit support  50 , the cables  44  pull the three pivotable arms  22   a ,  22   b ,  22   c  such that their respective distal end are urged together inwardly in the direction of the rotation axis of the measuring unit support  50 . This brings the radially movable measuring structure  22  into a compact configuration well-suited to be fitted inside a conical threaded portion  210  of a tube  200  to be inspected, as shown in  FIGS. 5 and 6 . 
     Once the radially movable measuring structure  22 , in its compact configuration, is fitted, at least partly, into the conical threaded portion  210 , the manually operable part  40  may be released which causes the pivotable arms  22   a ,  22   b ,  22   c  to move their respective distal end outwardly under the action of their respective elastic member  24  in order to press the defect detection sensor  30  and the first and second guiding elements  26   a ,  26   b  against the helical thread  210  to be inspected. 
     With reference to  FIG. 4 , the first and second guiding elements  26   a ,  26   b  and the defect detection sensor  30  are offset from each other with respect to the rotation axis of the measuring unit support  50  by a third of a pitch of the helical thread  210  in order to compensate the 120 degrees between the pivot of each pivotable arms  22   a ,  22   b ,  22   c  with respect to the rotation axis of the measuring unit support  50 . This offset ensures that the guiding elements  26   a ,  26   b  and the defect detection sensor  30  are precisely fitted together into respective portion of the helical thread  210 . 
     As illustrated in  FIG. 8 , the tube anchoring unit comprises an anchoring actuator  70  and an anchoring device  90  configured to be fitted into an anchoring device receiving section  220  of the threaded tube  200  ( FIGS. 3 and 5 ). Referring to  FIGS. 8 a  and 8 b   , the anchoring device  90  comprises an axial passage  98  along which a distal portion of the measuring unit driving shaft  60  is positioned. 
     A tube (not shown), achieving the function of a spacer, is mounted between two radially extendable members  108   a ,  108   b  ( FIGS. 8 a  and 8 b   ). The respective end portion of the spacer is mounted against one side of respective extendable member  108   a ,  108   b , while an opposite side of each extendable member  108   a ,  108   b  is mounted against a thrust bearing  102   a ,  102   b . A flange  103  is fixedly connected to the measuring unit driving shaft  60  against one of the thrust bearing  102  located near a proximal end of the anchoring device  90 . 
     The radially extendable members  108   a ,  108   b  may be for example in the form of polyurethane rings. The polyurethane rings  108   a ,  108   b  may expend under thrust of the spacer and respective thrust bearing  102   a ,  102   b  against two opposite sides of each polyurethane ring  108   a ,  108   b  in order to secure the anchoring device  90  against the inner cylindrical wall of the anchoring device receiving section  220  of the tube  200  as shown in  FIG. 3 . An elastic member  104 , preferably in the form of a compressions spring is arranged concentrically to the axial passage  98  of the anchoring device  90  in order to be mounted against one side of one polyurethane ring  108   a.    
     The anchoring actuator  70  of the anchoring unit comprises a rod  76  extending through an axial passage  62  of the measuring unit driving shaft  60  and a rod displacement actuator  82  configured to move the rod  76  into a first and a second axial position. The rod displacement actuator  82  comprises an actuatable member  79  mounted at a distal end of the rod  76  (for example screwed on a threaded portion  78  of the rod  76 ) and against a distal thrust bearing support  96  of the anchoring device  90 . A central compression spring  105  is arranged inside the compression spring  104  and around a portion of the rod  76  to cooperate with a spring stop  80  preferably in the form of a ring fixed around the rod  76 . 
     The rod displacement actuator  82  further comprises a lever  84  pivotally mounted about a lever pivot  86  arranged through an end portion of the rod  76  along an axis perpendicular to the longitudinal axis of the rod  76 . A drive unit connectable part  88  is mounted at one end of the measuring unit driving shaft  60 . The lever  84  comprises a cam portion  85  configured to cooperate with the drive unit connectable part  88  in order to displace the rod  76  along a direction away from the actuatable member  79  of the rod displacement actuator  82  from the first to the second axial position. 
     The displacement of the rod  76  from the first to the second axial position causes, on the one hand, the compression of the central compression spring  105  under the action of the spring stop  80  and, on the other hand, the compression of both polyurethane rings  108  simultaneously through the action of the actuatable member  79  against the distal thrust bearing support  96  which presses against one thrust bearing  102   a  and through the counteraction of the flange  103 , the other thrust bearing  102   b  and the spacer  92 . In this configuration, the anchoring device  90  is securely fitted inside the anchoring receiving section  210  of the tube  200  to be inspected. 
     When the lever  84  is returned to its initial position, the rod  76  is displaced in the opposite direction from the second axial position to the first axial position under the action of the central spring  105  on the spring stop  80  connected to the rod  76 . The anchoring device  90  is no longer under load and both polyurethane rings  108   a ,  108   b  return simultaneously to their non-extended configuration under the action of the compression spring  104  acting on one polyurethane ring  108   a . In this configuration, the anchoring device  90  is no longer securely fitted inside the anchoring receiving section  210  of the tube  200  and the threaded tube inspection device  10  may be removed. 
     As illustrated in  FIG. 10 , the rotatable inspection device  10  comprises a drive unit  150 . The drive unit  150  is connected to the drive unit connectable part  88  of the measuring unit driving shaft  60  as shown in  FIG. 8 . The torque applied by the drive unit  150  to the drive unit connectable part  88  is transmitted to the measuring unit support  50  through the linear-motion bearing  56 , bringing the rotatable inspection device  10  in rotation. The drive unit connectable part  88  may have for example a hexagonal shape, allowing the torque of the drive unit to be transmitted using standard hexagon socket wrench. 
     One of the advantages of the rotatable inspection device as described above lies on its ease of use for detecting possible defects during an inspection of a threaded portion  210  of a tube  200 . During the inspection, the operator executes the following operations:
         pulling the manually operable part  40  backwards along the sliding portion  54  of the measuring unit support  50  to bring the radially movable measuring structure  22  in a compact configuration,   positioning the anchoring device into the receiving section of the tube and fitting, at least partly, the radially movable measuring structure into the threaded portion of the tube to be inspected,   pulling the lever  84  to secure the anchoring device  90  into the receiving section  220  of the tube  200 ,   releasing the manually operable part  40  to move the respective distal end of the pivotable arms  22   a ,  22   b ,  22   c  outwardly under the action of their respective flexion spring  24  in order to press the defect detection sensor  30  and the guiding elements  26   a ,  26   b  against respective portion of helical thread  210 ,   rotating the measuring unit driving shaft  60  by means of the drive unit  150  in order to move the defect detection sensor  30  and the guiding elements  26   a ,  26   b  along the helical thread, and   reading the information displayed on the display unit  320  of the handheld remote monitoring unit  300 .       

     In the event, the rotatable inspection device  10  is used for inspection of the integrity of non-threaded axisymmetric portions, the translation of the rotatable inspection device may be manually imparted by the operator or achieved by other means such as a lead screw mechanism. In an embodiment, the lead screw rotates with the measuring unit driving shaft  60  and the lead screw nut is secured a non-rotating part, such as the drive unit  150  or the radially extendable members  108  of the anchoring device in order to generate an axial motion from the rotation of the measuring unit driving shaft  60 . 
       FIG. 11  shows another exemplary embodiment of a radially movable measuring structure of the rotatable inspection device suitable for inspection of the integrity of the helical thread  210  of a bolt  250 . In that respect, the radially movable measuring structure  22  comprises three pivotable arms  22   a ,  22   b ,  22   c  pivotally mounted on a supporting base  34  at 120 degrees from each other with respect to the rotation axis of the radially movable measuring structure  22 . 
     Each pivotable arm  22   a ,  22   b ,  22   c  is spring-loaded to push the distal ends of the three pivotable arms inwardly against respective regions of the helical thread  210  of the bolt  250 . As for the exemplary embodiment described above, a defect detection sensor (hidden by the threaded portion of the bolt) is mounted at the distal end of one pivotable arm, while a first and a second guiding element  26   a ,  26   b  are mounted at the distal end of the respective arm of the two other pivotable arms  22   b ,  22   c.    
     According to this embodiment, the three pivotable arms  22   a ,  22   b ,  22   c , may be pivotally actuated by a manually operable part similar to the one previously described in order to move together the respective distal end of the pivotable arms outwardly in a direction opposite the direction towards the rotation axis of the radially movable measuring structure  22 . 
       FIGS. 12 a , 12 b    illustrate another embodiment of the radially movable measuring structure  22  which is particularly adapted to inspect internal thread of tubes of large diameters, in particular to those having conical threaded portion opening. 
     The radially movable measuring structure  22  comprises a measuring unit support  50 ′ which is configured to rotate about the central axis of a threaded cylindrical part. Three linearly extendable arms  22   a ,  22   b ,  22   c  are mounted at 120° from each other and extend from the measuring unit support  50 ′ along an axis perpendicular to the axis of rotation of the measuring unit support  50 ′. Each extendable arm  22   a ,  22   b ,  22   c  comprises a guide  28  which comprises on two opposite sides a linear slit  28   a . A defect detection sensor  30  is mounted at a distal end of one extendable arm  22   a , while a first and a second guiding element  26   a ,  26   a , for example in the form of rotatable discs, are each mounted at a distal end of one of the two other extendable arms  22   b ,  22   c.    
     The defect detection sensor  30  is connected or forms an integral part with a rectangular portion comprising on two opposite sides a projection  27  fitted into the corresponding linear slit  28   a  of the guide  28  such that the sensor  30  may slide along the guide  28  of the extendable arm  22   a . Each rotatable disc  26   a ,  26   b  is mounted to rotate about a shaft  27  whose both extremities protrude into respective linear slit  28   a  of the guide  28  of respective extendable arm  22   b ,  22   c  such that each rotatable disc  26   a ,  26   b  may slide along their respective guide  28  of their respective extendable arm  22   b ,  22   c . A compression spring  24  is mounted inside the guide  28  of each extendable arm  22   a ,  22   b ,  22   c  and cooperate with a stop spring  29  to urge the rotatable discs  26   a ,  26   b  and the defect detection sensor  30  outwardly along a radial direction. 
     The first and second rotatable discs  26   a ,  26   b  and the defect detection sensor  30  are offset from each other with respect to an axis perpendicular to the rotation axis of the measuring unit support  50 ′ by a third of a pitch of the helical thread. This offset compensates the 120 degrees between each extendable arm to ensure that the rotatable discs  26   a ,  26   b  and the defect detection sensor  30  are precisely fitted together into different portions of the helical thread  210 . 
     During an inspection operation of the integrity of a conical threaded portion, the compression spring  24  of each guide  28  urges the defect detection sensor  30  and the rotatable discs  26   a ,  26   b  against the helical thread. The sensor  30  and the discs  26   a ,  26   b  are configured to slide radially inwardly, under the action of the surface of the threaded portion, as they move along the helical thread of the conical threaded portion. The radially movable measuring structure  20  according to this embodiment may be secured to the tube to be inspected by an anchoring device as the one described above. 
     The rotatable inspection device according to the invention may further comprise additional sensors, in particular an angular position sensor and a linear position sensor in order to localize a defect on a threaded or non-threaded portion of a tube according to the angular and axial positions of the measuring unit driving shat  60  of the measuring unit  20 . 
     In order to ensure full traceability of the inspection data, it is desirable to record the position of the defect detection sensor  30  relative to the part being inspected alongside with the defect detection sensor data. For thread inspection, as the defect detection sensor  30  follows a helical path, a single position measurement is necessary to determine its position on the part. Provided the sensor has been correctly positioned at the start of the thread, a measurement of its angular position is sufficient to reconstitute a defect map of the thread. Alternatively, a linear position measurement of measuring unit support  50  on the measuring unit driving shaft  60  can be used to achieve the same function. 
     In its simplest embodiment, the angular sensor is a Hall sensor or optical gate giving one electrical impulse per rotation of the measuring unit support  50 , e.g. with a magnet or light source on a fixed portion of the rotatable inspection device  10  and a Hall device or light detector of a rotating portion. In an advantageous embodiment, the angular position is determined with respect to gravity (as the part is stationary during inspection) by using a 2D or 3D accelerometer placed on a rotating part of the rotatable inspection device  10 . An optional gyroscope placed on a rotating part of the rotatable inspection device  10  may be used to enhance the precision of the angle measurement during inspection, using data fusion algorithms known from the art. 
     Although the radially moveable measuring structure  22  of any of the above described embodiments relies on three arms  22   a ,  22   b ,  22   c , the function of these arms may be achieved through other means. For example, the radially movable measuring structure  22  could be shaped such as to allow only one or more radial extensions in regions to which the defect detection sensor  30  and/or guiding elements  26  are fixed. The radially moveable measuring structure  22  may be in the form of a single part which may combine the functions of the base receiving portion  52 , the arms  22 , elastic members  24  and potentially guiding element supports  28 . 
     In addition, the radially movable measuring structure  22 , the electronic device  43  and the measuring unit support  50  may form an integral part to obtain a single part measuring unit  20  which may be produced for example through an additive manufacturing process. Such a single part measuring unit  20  may achieve the functions of the radially movable structure  22 , the functions of the flexion/compression springs  24 , the functions of sensor support  32 , the function of supporting base  34 , as well as all the functions of the measuring unit support  50 . This single flexible part may achieve all the sub-functions of the measuring unit support, namely the functions of the supporting base receiving portion  52 , the function of operable part sliding portion  54  and linear bearings  56 . 
     Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. For example, the guiding elements may be replaced by additional defect detection sensors, each sensor inspecting different portions of the helical thread. 
     REFERENCE LIST 
     
         
         Rotatable Inspection device  10   
         Measuring unit  20   
         Radially movable measuring structure  22   
         Biased arms  22   a ,  22   b ,  22   c    
         Pivotable arms (one embodiment) 
         Extendable arms (one embodiment) 
         Biasing means 
         Elastic members 
         Flexion springs  24  (one embodiment) 
         Compression spring  24  (one embodiment) 
         Guiding element  26   a ,  26   b    
         Guiding element supports  28   
         Defect detection sensor  30   
         Electromagnetic sensor 
         Hall-effect sensor 
         Ultrasound sensor 
         Sensor support  32   
         Electrical wire  33   
         supporting base  34   
         Through-holes  35   
         Radially movable measuring structure actuator 
         Cable guiding ring  38   
         Manually operable part  40   
         Cables  42   
         Electronic device  43   
         Signal processing unit  44   
         A/D converter  45   
         Transmitter  46   
         Battery  47   
         Electronic device holder  48   
         Measuring unit support  50   
         Supporting base receiving portion  52   
         Operable part sliding portion  54   
         Linear bearings  56   
         Bearing spacer  57   
         Axial passage  58   
         Measuring unit driving shaft  60   
         Square cross-section 
         Axial passage  62   
         Anchoring unit 
         Anchoring actuator  70   
         Rod  76   
         Threaded portion  78   
         Actuator member  79   
         Spring stop  80   
         Rod displacement actuator  82   
         Lever  84   
         Cam portion  85   
         Lever pivot  86   
         Drive unit connectable part  88   
         Anchoring device  90   
         housing  92   
         Cylindrical spacer 
         Proximal thrust bearing support  94   
         Second end portion  96   
         Axial passage  98   
         Bearing members  100   
         Thrust bearings  102   a ,  102   b    
         Ball-bearings 
         Flange  103   
         Elastic members  104   
         Compression springs 
         Central compression spring  105   
         Radially extendable members  108   
         Drive unit  150   
         Threaded and non-threaded part  200   
         Tube 
         Threaded portion  210   
         Conical threaded portion 
         Anchoring device receiving section  220   
         Bolt  250   
         Remote monitoring unit  300   
         Receiver  310   
         Display unit  320