WO2018013899A1

WO2018013899A1 - Tube sheet inspection robot

Info

Publication number: WO2018013899A1
Application number: PCT/US2017/042079
Authority: WO
Inventors: Jeffrey Raymond GUEBLE; Thomas O. MATELICH; Tim Ellis
Original assignee: Zetec, Inc.
Priority date: 2016-07-14
Filing date: 2017-07-14
Publication date: 2018-01-18

Abstract

A robot for positioning inspection probes in steam generator tube sheet is described, the apparatus being capable of affixing itself to a sheet of tubing by locating a plurality of locking grippers into steam tubes while placing an inspection device other tubes one at a time. The grippers and the inspection device are manipulated by articulated robot arms having two radial joints. The robot comprises software enabling linear movement across the tube sheet such that gripper arms and the robot body may relocate while the inspection arm is fixed in a tube. In an embodiment, there are four such arms for the grippers and a fifth arm for placement of the probe. A gripping device for fastening a machine to a cylindrical opening is also described. The gripping device includes gripping shoes that wedge against the inside of the cylindrical opening, locking the gripping device into the opening.

Description

TUBE SHEET INSPECTION ROBOT

CROSS REFERENCE TO RELATED APPLICATIONS

This PCT application claims priority to U.S. Provisional Patent Application Serial Number 62/362,180 filed July 14, 2016 and titled Tube Sheet Inspection Robot. The entire disclosure of this application is included herein by reference.

BACKGROUND

Pressurized water nuclear powered electric generating systems use heat generated by a nuclear reaction to heat a primary coolant that circulates through the reactor core. The coolant is used to generate steam in a steam generator. The steam generator is typically an upright cylindrical pressure vessel with hemispherical end sections in which a plurality of U- shaped tubes are arranged. A traverse plate called a tube sheet, located at the lower end of the cylindrical section, divides the steam generator into a primary side, which is the lower hemispherical section below the tube sheet, and a secondary side above the tube sheet. The tube sheet is generally formed of a thick carbon steel plate with an array of thousands of holes into which the ends of the U-shaped tubes are inserted. As coolant is pumped through the reactor core it is heated up by the reactor. This hot, radioactive, coolant is introduced to the inlet side of the U-shaped tubes via the tube sheet and exchanges heat with water at the top of the steam generator, thus generating steam and allowing the coolant to cool. The cooled water travels down the outlet side of the U-shaped tubes and out of the vessel via the tube sheet.

In other embodiments, "once through" steam generators (OTSG) may be used, in which a plurality of straight tubes is used in lieu of the U-shaped tubes described above. In such an embodiment, coolant is introduced into one end of the tubes via a first tube sheet and exits the other end of the tubes via a second tube sheet.

The tubes in such a heat exchanger system are critical to the operation of nuclear powered electric generating systems because they form the primary barrier between the radioactive coolant and the non-radioactive steam. Because of the radiation hazard present in nuclear powered utility steam generators, heat exchanger tubes are generally inspected and serviced remotely to avoid exposing maintenance personnel to potentially harmful radiation. It should be noted that similar steam tube arrangements are used in other industrial heat exchange applications that to not involve nuclear power, but which still require remote inspection. The disclosed system and methods are not intended to be limited to the nuclear power industry. The devices and methods herein may be applied to any application where a plurality of tubes are to be internally inspected by non-destructive means.

Robotic systems have been developed for remotely performing repair and maintenance operations on these heat exchanger tubes via the tube sheet. Steam generation inspection robots currently fall into two configurations: arm style robots, mounted onto the entry port, and tube walking robots which grip tubes and walk on the tube sheet by anchoring attachment devices of the robot to the open tube ends via the tube sheet, while a separate tool arm on the robot places a tool or inspection probe, such as an eddy current inspection probe, into a tube to be inspected. The anchors are commonly termed "grippers" in the field of steam tube inspection and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing of the tube sheet side of a steam generator tube inspection robot having tube grippers;

FIG. 2 is a three-dimensional drawing of the distal side of the steam tube inspection robot of FIG. 1 ;

FIG. 3 is a transparent top view of the steam tube inspection robot of FIGS. 1 and 2; FIG. 4A is a transparent three-dimensional view of a two-link positioning arm of the exemplary tube inspection robot of FIGS. 1 and 2;

FIG. 4B is a transparent three dimensional view of a gripper head of the exemplary tube inspection robot of FIGS. 1 and 2;

FIG. 5 is an exemplary system block diagram;

FIG. 6 is and exemplary system controller of the system of FIG. 5;

FIG. 7 is a cross-section view of a portion of gripper head 125 and gripper 200 consistent with embodiments described herein;

FIG. 8 is a three-dimensional view of an exemplary tube gripper according to an aspect of the invention;

FIG. 9 is an exploded view of the exemplary inventive tube gripper of FIG. 8;

FIG. 10 is a cross sectional view of the tube gripper of FIGS. 8 and 9 in an actuated state;

FIG. 11 is a cross sectional view of the tube gripper of FIGS. 8 and 9 in a retracted state;

FIG. 12 is a three-dimensional view of internal components of the tube gripper of FIGS. 8 and 9;

FIG. 13 is a three dimensional view of an exemplary single shoe of FIGS. 8 and 9; FIG. 14 is a further three dimensional view of an exemplary single shoe of FIGS. 8 and 9; and

FIG. 15 is a flow diagram illustrating an exemplary process for conducting a tube sheet test using a tube sheet robot in accordance with embodiments described herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Those skilled in the art will recognize other detailed designs and methods that can be developed employing the teachings of the present invention. The examples provided here are illustrative and do not limit the scope of the invention, which is defined by the attached claims. The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements.

FIGS. 1-3 show an exemplary embodiment of a steam generation tube inspection and maintenance robot 100 that includes a central body 110 and a plurality of articulated gripper arms 115 that are moveable with respect to central body 110. FIG. 4A illustrates a transparent three-dimensional view of a two-link positioning arm of the exemplary tube inspection robot of FIGS. 1 and 2 and FIG. 4B is a transparent three dimensional view of a gripper head of the exemplary tube inspection robot of FIGS. 1 and 2.

As shown in FIGS 1 and 2, consistent with embodiments described herein, each gripper arm 115 may include a SCARA (Selective Compliance Assembly Robot Arm)-type device, which can be rotated with respect to the central body 110 about a first pivot point 110a ("shoulder joint") attached to a first gripper arm portion 117. Each gripper arm has a second portion 120 that can be rotated with respect to the first portion 117 about a second pivot point 116 ("elbow joint"). At the distal end of the second portion 120 of each gripper arm is a gripper head 125 that is actuated axially with respect to the gripper arm second portion 120 to insert and remove grippers 200 from a tube sheet. In one implementation, gripper head 125 may be pneumatically actuated, while in other implementations, gripper head 125 may be actuated electrically or hydraulically. Simultaneous actuation of the actuators on all four gripper arms can be used to move the central body 110 further or closer to the tube sheet. This operation can also be performed with only three gripper arms if only three grippers are fastened to tubes in a tube sheet. Consistent with embodiments described herein, gripper heads 125 may each include ball screw actuators comprising internal gear heads that extend and retract a gripper shoe actuation rod 210, as shown in Figs. 8-12 and described in additional detail below. Gripper heads 125 may also include integral strain gauges to provide pull force feedback for each gripper. Because gripper arms 115 of robot 100 are articulated, robot 100 can insert grippers 200 into any tube within the reach of the arm, regardless of tube pitch or position. Thus, robot 100 is not constrained by the grid pattern of the tube sheet, but can traverse the tube sheet in any direction, making it much more maneuverable than robots which are matched to a specific tube grid pattern or orientation. Thus, the robot can walk on any tube sheet without the need for any mechanical re-configuration, as the configuration is under software control, and is not set by hardware.

As shown in FIGS. 2 and 3, consistent with embodiment described herein, robot 100 is also fitted with a fifth articulated arm 118, which may accommodate a guide tube 119 at its distal end. Guide tube 119 is a tube into which a tube inspection probe, such as an eddy current probe, is inserted. As most clearly shown in FIG. 3, the fifth arm 118 includes first and second portions 118a and 118b joined by pivot point 118c. The dimensions of first and second portions 118a and 118b are such that arm 118 can reach tubes in a wide radius, past the reach of the gripper arms. This allows robot 100 to reach holes within a much larger work envelope than known tube-walking robots.

Consistent with embodiments described herein, each of the four arms 115 are provided with free rotation with respect to their associated grippers 200. This allows each gripper arm 115 to articulate at the shoulder 110a and elbow 116 j oints even after the gripper 200 is fixed in a tube. As described below, grippers 200 are mounted in the gripper head 125 via bearings, such that the gripper head 125 and the second gripper arm portion 120 are able to rotate about the gripper 200 while the gripper is fixed inside a steam tube. The gripper 200 is coupled with a free-floating joint about the mandrel 220 axis to allow the gripper head 125 to rotate with respect to the gripper 200. Detailed views of an exemplary design of the gripper head 125 showing an exemplary bearing design are shown in FIGS. 7-14 and described in additional detail below.

FIG. 5 is a block diagram illustrating an exemplary system consistent with embodiments described herein. As shown, system 500 includes a robot controller 510 which communicates with one or more probe arms 119, gripper arms 115, and one or more cameras 550. Consistent with embodiments described herein, controller 510 may also communicates with external devices 520.

Information exchange between system controller 510 and the probe arms 119 may include shoulder and elbow axis sensor data and axis drive servo data. Information exchange between the controller 510 and the gripper arms 115 may include shoulder and elbow axis sensor data and axis drive servo data, as well as information and data associated with the position and operational configuration of gripper heads 125, such as linear position and drive data, gripper shoe actuator position and drive data, and gripper head strain gauge-based force data.

Information exchanged between system controller 510 and the one or more cameras 550 includes, for example, camera still picture and/or video images, as well as camera control information (e.g., pan, zoom, tilt, aperture, etc.). Information exchanged between the system controller 510 and external devices may include tube sheet tube location data, test plan data, manual robot control data and camera video.

FIG. 6 is a diagram illustrating exemplary physical components of a device 600. Device 600 may correspond to various devices within the above-described system, such as the system controller 510. Device 600 may include a bus 610, a processor 620, a memory 630, an input component 640, an output component 650, and a communication interface 660.

Bus 610 may include a path that permits communication among the components of device 600. Processor 620 may include a processor, a microprocessor, or processing logic that may interpret and execute instructions. Memory 630 may include any type of dynamic storage device that may store information and instructions, for execution by processor 620, and/or any type of non-volatile storage device that may store information for use by processor 620.

Software 635 includes an application or a program that provides a function and/or a process. Software 635 is also intended to include firmware, middleware, microcode, hardware description language (HDL), and/or other form of instruction. By way of example, with respect to the network elements that include logic to provide proof of work

authentication, these network elements may be implemented to include software 635.

Additionally, for example, device 600 may include software 635 to perform tasks as described below with respect to FIG. 15.

Input component 640 may include a mechanism that permits a user to input information to device 600, such as a keyboard, a keypad, a button, a switch, etc. Output component 650 may include a mechanism that outputs information to the user, such as a display, a speaker, one or more light emitting diodes (LEDs), etc.

Communication interface 660 may include a transceiver that enables device 600 to communicate with other devices and/or systems via wireless communications, wired communications, or a combination of wireless and wired communications. For example, communication interface 660 may include mechanisms for communicating with another device or system via a network. Communication interface 660 may include an antenna assembly for transmission and/or reception of RF signals. In one implementation, for example, communication interface 660 may communicate with a network and/or devices connected to a network. Alternatively or additionally, communication interface 660 may be a logical component that includes input and output ports, input and output systems, and/or other input and output components that facilitate the transmission of data to other devices.

Device 600 may perform certain operations in response to processor 620 executing software instructions (e.g., software 635) contained in a computer-readable medium, such as memory 630. A computer-readable medium may be defined as a non-transitory memory device. A non-transitory memory device may include memory space within a single physical memory device or spread across multiple physical memory devices. The software instructions may be read into memory 630 from another computer-readable medium or from another device. The software instructions contained in memory 630 may cause processor 620 to perform processes described herein. Alternatively, hardwired circuitry may be used in place of or in combination with software instructions to implement processes described herein. Thus, implementations described herein are not limited to any specific combination of hardware circuitry and software.

Device 600 may include fewer components, additional components, different components, and/or differently arranged components than those illustrated in FIG. 6. As an example, in some implementations, a display may not be included in device 600. In these situations, device 600 may be a "headless" device that does not include input component 640. Additionally, or alternatively, one or more components of device 600 may perform one or more tasks described as being performed by one or more other components of device 600.

Although an exemplary steam generation tube inspection and maintenance robot 100 is described above, it should be understood that the embodiments described herein may have applicability in a variety of steam generation tube inspection devices.

FIG. 7 is three-dimensional cross section view showing the pivoting grip head details. As shown, the design uses two bearings, a lower bearing 710 and an upper bearing 720. Lower bearing 710 takes both thrust and moment of a gripper mandrel 220. Upper bearing 720 is also a thrust bearing and is mounted in housing 730. Movement of housing 730 is actuated by a ball screw (not shown), which moves the upper bearing 720 and the shoe actuation rod 210 axially up and down in the gripper head 125. The inner race 740 of the upper bearing 720 is connected to the gripper shoe actuation rod 210 by a nut (not shown) that can be accessed with a wrench to attach the shoe actuation rod 210 to the gripper head. Thus, the shoe actuation rod 210 can be actuated in and out of the gripper mandrel 220 while the gripper head 125 can rotate freely with respect to the gripper mandrel 220 and the shoe actuation rod 210.

Each of the four arms is an identical assembly to minimize spares requirements. The arms feature internal cabling and pneumatic routing to avoid the possibility of damage to either; integral controls; and high-accuracy 26 bit-per-revolution encoders on each of the shoulder 1 10a and elbow 1 16 joints

Consistent with the embodiment of FIGS. 1 , 2, and 3 tube sheet robot 100 is attached to a tube sheet by the four grippers 200, from which state the robot can manipulate the tool head arm 118 to insert a tool in any open steam tube within reach. The robot can move to a new position on the tube sheet by withdrawing a gripper 200 from one tube, repositioning the griper arm 1 15 and inserting the gripper 200 in another tube and repeating this procedure for all four grippers.

This process may be repeated until the robot 100 reaches any required location on the tube sheet. In operation, the robot 100 may be mounted to the underside of a steam generator tube sheet and can be suspended by at least three of the grippers 200 at a time.

The robot may also fitted with machine vision cameras. A first camera may be mounted on the main body 110 of the robot, and aimed at the tube sheet. During installation of the robot to the tube sheet, the camera actively locates holes on the tube sheet surface, and identifies the pitch of the tube sheet. This allows the robot to automatically move each arm to a location corresponding to a hole on the tube sheet, providing an automatic configuration strategy. The body-mounted camera also allows the robot to track individual holes on the tube sheet as the robot is moved, providing a secondary verification of the position of the body on the sheet.

A second camera may be mounted on the second link of the guide-tube arm 1 18. This camera provides two functions. The first function is to check the location of the tube sheet holes to ensure accuracy. Tube sheets are notoriously inaccurate, and this feature ensures that the position of the guide tube with respect to the tube to be inspected is accurate, regardless of the accuracy of the sheet. A further feature of the camera mounted to the guide tube arm 116 is that this camera may be used to field calibrate the robot, if necessary. If the robot is serviced to a level which requires disassembly of the gripper and/or guide tube arms, the guide tube arm-mounted camera can be used to assess and adjust the robot calibration to a calibration plate. Each arm can access a target from both the right and the left. If the arm calibration is good, either direction will correctly position the arm over the target. If the calibration is off, this will not be the case. Using the guide tube mounted camera, the robot can assess the accuracy of positioning over the hole in each movement, and then use the difference to adjust the angle and length offsets for the arm. Because the camera can be focused onto targets on each of the crawling arms, this method can also be used to assess the calibration of each arm after the guide tube arm is calibrated.

Consistent with implementations described herein, an improved tube gripper is disclosed. With reference to FIGS. 8 and 9, there is shown an exemplary tube gripper 200 consistent with embodiments described herein. FIGS. 10 and 11 are a cross-sectional views of grippers 200 in actuated and retracted states, respectively. Fig. 12 is a three-dimensional view of internal components of an exemplary tube gripper 200. FIGS. 13 and 14 are three dimensional views of exemplary single shoes consistent with embodiments described herein.

As shown in FIGS. 8 and 9, tube gripper 200 includes an upper mandrel 220, a gripper shoe shield 245, gripper shoes 230 and a shoe actuation rod 210. The upper gripper mandrel 220 includes a truncated conical lower portion 225 on which the upper portion of each of the gripper shoes 230 rides. The upper mandrel 230 also includes threads 222 for mounting into a gripper actuator, such as described above.

The gripper shoe shield 245 includes openings 247 to accommodate the gripper shoes 230, which in operation move in and out radially through the openings 247. Shoe actuation rod 210 includes threads 205 for assembly to a gripper shoe actuator such as described above. The shoe actuation rod also includes a key 212 for alignment and assembly. As shown in FIGS. 10 and 1 1, the shoe actuation rod also includes internal threads 21 1 for assembly to the lower shoe mandrel 260, which has threads 262 that screw into the shoe actuation rod 210. The lower mandrel 260 includes a truncated conical portion 265 similar to the truncated conical portion 225 of the upper mandrel 220. The lower portion of the shoes rides on the conical portion 265 of the lower shoe actuation rod 260. In an exemplary embodiment, the truncated conical portions of the upper and lower mandrel 225, 265 are based on cones whose surfaces form an angle of 15 degrees from the axis of the cones.

Shoe alignment springs 250 and 255 fit over the lower mandrel 260. The shoe alignment springs have a shoe alignment washer 252 sandwiched between them. Protective sealing washers 240 and 242 are arranged to be fitted over the upper mandrel and the lower mandrel 260. As will be described in more detail below, the sealing washers are arranged to prevent debris from entering the shoe shield 245 when the lower mandrel 265 is moved in and out with respect to the upper mandrel 240. Each of the shoes may include a plurality of alignment magnets 235. The alignment magnets help retract the shoes when the lower mandrel 265 is moved away from the upper mandrel 220 by attracting the shoes to the two mandrels. Without the magnets, the shoes will only retract slightly off the tube inner face when the mandrels are separated.

With reference to FIGS. 10 and 11, the operation of the tube grippers will now be described. FIGS. 10 and 11 are axial cross section views of the exemplary tube gripper 200 of FIGS. 9 and 10. FIG. 11 shows the tube gripper 200 with the shoes 230 retracted with their faces 232 substantially flush with shoe shield 245. In this position, shoe actuation rod 210 is located downward towards the distal end of the gripper assembly 200 with the shoe actuation rod threads 205 urged towards the mounting threads 222 on the upper mandrel 220. In this position, the truncated conical portions 225 and 265 of the upper mandrel 220 and the lower mandrel 260 are separated axially to the extent that the shoes 230 move radially inwards sufficiently that their faces are substantially flush with the shoe shield 245. In this position, the shoe alignment springs 250 and 255 are substantially relaxed with shoe positioning washer 252 located substantially between the bottom of the upper mandrel and the top of the conical portion 265 of the lower mandrel, 265. In some implementations, alignment magnets 235 are attracted to truncated conical surfaces 225/265 of the upper mandrel 220 and lower mandrel 260, respectively, if these components are made of a ferrous material, such as steel. In other embodiments, alignment magnets may be omitted, which will cause shoes 230 to not retract automatically, but will loosen their grip on the inside of a tube wall sufficiently for the gripper 200 to be retracted from the tube. Shoes 230 may include a chamfered lower face portion 233, such that even if shoes 230 are not fully retracted when the shoe actuation rod 210 is retracted from the upper mandrel 220, when the gripper is inserted into a new tube, the tube inner wall interfering with the chamfered surfaces 233 of the shoes 230 will urge them inward as the gripper is inserted into a tube.

FIG. 10 shows the gripper 200 with the shoes 230 in an extended position. In this position, the shoe actuation rod 210 is urged into the upper mandrel 220. In this position the truncated conical surfaces 225, 265 of the upper mandrel and the lower mandrel, respectively, acting against the corresponding concave surfaces 238, 239 on the shoes will urge the shoes 230 radially outward from the axis of the gripper assembly 200. With the gripper 200 inserted into a steam tube, substantially up to flange 221, the shoes 230 are urged outward against the steam tube inner wall when the shoe actuation rod 210 is retracted away from the upper mandrel 220. As long as retraction force is applied to the shoe actuation rod 210, the gripper 200 will remain fixed in the tube. Removal of this retraction force, combined with a withdrawal force on the entire gripper assembly 200 by a gripper actuator (e.g. as shown in item 125 in Fig. 1) will cause the gripper to retract from a tube, with the shoes either fully retracting in the case where they include alignment magnets 235 or simply releasing their grip on the tube inner wall in the case where the shoes do not include alignment magnets 235.

FIG. 12 is a detailed view of the position of the shoe alignment washer 253, shoe alignment springs 250, 255 and the shoe 220 as aligned between truncated conical surfaces 225 and 265.

Consistent with embodiments described herein, gripper 200 is configured to work with a high-force servo ball-screw mechanism capable of pulling on the gripper actuation rod 210 with a sustained force of at least 800 pounds. The combined mechanism (gripper 200 and ball screw actuator) is self-locking only in the sense that the force required to back drive the motor through the ball-screw and reduction gear head is too high for the device to effectively release during use.

Optimization of the engagement pressure of the wedge gripper 200 is performed through feedback control of the torque applied to the gripping motor during activation. A high-speed feedback loop monitors the average torque applied to the motor, allowing the gripper 200 to be deployed as a grip-to-torque device, preventing damage to the tubes through overpressure.

With reference to FIGS. 13 and 14, exemplary gripper shoes 230 will now be described in further detail. FIG. 13 shows an inside view of an exemplary gripper shoe 230. As discussed above, gripper shoes 230 may include concave surfaces 235, 239 shaped to substantially conform to the truncated conical surfaces 225, 265 of the upper mandrel 220 and the lower mandrel 265, respectively. The shoes 230 also include a slot 237 configured to matingly engage with the shoe alignment washer 252. The force of the washer 252, which is held between alignment springs 250 and 255, on the shoes keeps the shoes substantially aligned between the upper mandrel truncated conical surface 225 and the lower mandrel truncated conical surface 265. As the gripper shoe shield 245, moves axially with the shoes 230, the shoe alignment washer in conjunction with the forces exerted by the shoe alignment springs. 250, 255 also helps keep the gripper shoe shield aligned between the upper mandrel truncated conical surface 225 and the lower mandrel truncated conical surface 265.

FIG. 14 shows the outer face 232 side of an exemplary gripper shoe 230. The face 232 of each shoe pad is curved to roughly match the inner surface of the tube into which it will interface. The grippers are sized to fit a particular tube inner diameter and the face of the shoes is also shaped to fit that tube inner diameter. As discussed above, the shoes 230 include a chamfered lower portion 233 that aids in guiding the shoes into a tube and also helps retract the shoes when they are inserted into a tube. The shoes 230 also include rounded edges 231 on all edges of the shoe face to avoid the shoes damaging a tube inner wall with sharp edges. The shoes 230 also include flanges 238 that retain the shoes inside the shoe shield 245. The shoe faces may be made of Nitronic 60. The whole shoe may be made of Nitronic 60.

While the exemplary gripper described herein has three shoes, other configurations are possible, including grippers having two or more than three shoes.

In an aspect of the inventive robot system, the robot controller 410 may be programmed to move the test probe arm 118 simultaneously with and/or independently from the gripper arms 115. For example, consistent with embodiments described herein, robot central body 110 is able to be moved by the gripper arms 1 15 with a test probe inserted in a steam tube, because while the gripper arms 1 15 are moving robot central body 1 10 to a next position on the tube sheet, the test probe arm 118 is also moving (e.g., relative to central body 110) to keep the test probe head 125 centered over the steam tube under test. Thus, the tube testing and the manipulator movement happen simultaneously, thus removing wait time between tube tests. A simplified movement sequence is as follows: 1) the robot positions guide-tube/probe 1 19 to location of tubes to be tested; 2) tube test process begins; 3) the robot positions itself to best access subsequent test locations, while maintaining guide-tube/probe location; 4) test process concludes for this location; 5) steps 1 -4 are repeated until all desired steam tubes are inspected.

Maintaining the guide-tube/probe location while "walking" the robot across a tube sheet is achieved via synchronization of multiple SCARA robot arms (e.g., arms 1 15) performing linear moves. The walking arms shift the body to a new position while the guide- tube arm performs an opposite move to maintain position thus allowing uninterrupted and continuous testing. When using a dual guide tube tool head with an extra axis for positioning a second probe, the extra axis can also synchronously rotate to keep the second probe in place.

Because of the large number of steam tubes in a typical inspection environment, the wait time for repositioning a test probe should be between 150-350 ms, since only the probe arm needs to move (since the robot arms 1 15 have already been moved during the prior test period). This is dependent on the test duration being long enough to allow the robot move to complete and the proximity of the subsequent tube to be tested. To support this, the robot controller 510 takes into account its present location, current test being performed, and a look ahead list of additional tubes to be tested. With this information, the controller software can plan to perform all tests in the area of interest without the wait time induced with the manipulator repositioning. For tests where walking is required to reach the target, the guide- tube/probe can be positioned before the robot has finished moving all legs, saving some time as well.

An exemplary process for moving the robot during tube inspection is described in FIG. 15. The process may be controlled by the processor 620 of the device 600 of FIG. 6 at block 1510, a tube sheet inspection test plan is started. For example, processor 620 of robot controller 510 may execute software 635 that includes instructions for initiating and performing this process. At block 1515, a list of tubes and locations is retrieved from a test list database. The database may be stored for example in an onboard memory (e.g., memory 630) or retrieved from an extemal source. At blockl520, the process of moving the test probe arm 1 18 to a tube is begun as well as a "look ahead" procedure wherein the locations of subsequent tubes to be tested from the test list are reviewed. At decision point 1525, it is determined whether the current tube to be to be tested is within reach of the test probe arm 1 18, without moving central body 110. If the tube is in reach (block 1525 - Yes), test probe arm 1 19 is moved (block 1530) to locate the test probe over the tube to be inspected. If the tube to be tested is not in reach of the test probe arm (block 1525 - No), then at block 1527, a path plan to move the robot is created. At block 1528, arms 1 15 are moved per the path plan and, at step 1530, the probe arm is moved. While the tube is being inspected (block 1540), the look ahead process is conducted, comprising block 1542 wherein it is determined if a new robot central body position will better support subsequent tubes to be tested. If a new position is beneficial, at block 1544, a path plan is created for moving the robot body to the new position while keeping the test probe in the tube currently being tested, which then occurs at block 1546. After the current tube inspection is complete, program control loops back to step 1520 to move the test probe arm to the next tube location. The process is repeated until all tubes in the test list are inspected.

Although the invention has been described in detail above, it is expressly understood that it will be apparent to persons skilled in the relevant art that the invention may be modified without departing from the spirit of the invention. Various changes of form, design, or arrangement may be made to the invention without departing from the spirit and scope of the invention. Therefore, the above-mentioned description is to be considered exemplary, rather than limiting, and the true scope of the invention is that defined in the following claims.

No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article "a" is intended to include one or more items. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise.

Claims

WHAT IS CLAIMED IS;

1. A tube inspection robot configured for moving across a steam generation tube sheet, comprising:

a robot body,

a plurality of positioning arms having proximal ends connected to said robot body and distal ends connected to tube grippers and

an inspection arm having a proximal end connected to said robot body and a distal end comprising a tool interface.

2. The tube inspection robot of claim 1, comprising four of said positioning arms, wherein said positioning arms are selective compliance assembly robot arms (SCARA) comprising first and second arm portions with a first rotational joint on said robot body connected to said first arm portion, and a second rotational joint at the distal end of said first arm portion connected to said second arm portion.

3. The tube inspection robot of claim 2, wherein said inspection arm is a SCARA arm having first and second inspection arm portions with a first rotational joint on said robot body connected to said first inspection arm portion and a second rotational joint connecting said first and second rotational arm portions.

4. The tube inspection robot of claim 2, wherein each of said positioning arms comprises a gripper head connected to said distal end of said second arm portion, by a linear actuator configured to move said gripper head along an axis parallel to an axis of rotation of said first and second rotational joints.

5. The tube inspection robot of claim 4 wherein said each of said tube grippers is connected to said gripper head by a first thrust bearing configured such that when said tube gripper is locked into a steam tube, said gripper head can rotate about said tube gripper.

6. The tube inspection robot of claim 1, wherein said tube gripper is generally cylindrical about a tube gripper axis and comprises

cylindrical upper mandrel having proximal and distal ends, an axial bore and a truncated conical portion at said distal end, said truncated conical portion being wider towards said proximal end;

a cylindrical lower mandrel having a rod shaped proximal portion and a truncated conical distal portion, said truncated conical portion being wider towards the distal end of the lower mandrel;

a plurality of gripping shoes having curved faces configured to conform to the cylindrical opening, said shoes having upper and lower inner concave portions that are configured to conform to the upper mandrel truncated conical portion and the lower mandrel truncated conical portion, respectively, and

a substantially cylindrical gripping shoe housing configured to retain said gripping shoes about said upper and lower mandrels and to allow said shoes to move radially inward and outward through openings in said gripping shoe housing,

wherein said rod shaped proximal portion of said lower mandrel slides proximally and distally in said axial bore and wherein motion of said lower mandrel towards the proximal end of the apparatus causes said shoes to move radially outward through said gripping shoe housing openings.

7. The tube inspection robot of claim 6, wherein said upper mandrel truncated conical portion and said lower mandrel truncated conical portion have truncated conical surfaces at an angle of 15 degrees from the tube gripper axis.

8. The tube inspection robot of claim 6, wherein said lower mandrel is secured to an actuation rod at the lower mandrel proximal end and said actuation rod comprises threads at its proximal end, said threads being configured to mate with a gripper actuator in said gripper head.

9. The tube inspection robot of claim 6, wherein said faces of gripping shoes include inclined distal portions, said inclined distal portions having greater clearance within the cylindrical opening than the remaining portions of said shoe faces.

10. The tube inspection robot of claim 6, wherein said gripping shoes include magnets in said concave portions, and wherein said truncated conical portions of said upper and lower mandrels are attracted to said magnets.

11. The tube inspection robot of claim 6, wherein said gripping shoes include slots on the opposite side of the shoes from their faces, said slots being configured to fit loosely over an alignment washer having protrusions that matingly correspond to said slots, said alignment washer being held substantially mid-way between said upper mandrel truncated conical portion and said lower mandrel truncated conical portion by proximal and distal alignment springs.

12. The tube inspection robot of claim 6, wherein at least a tube interface portion of said shoes is made of Nitronic 60.

13. The tube inspection robot of claim 3, further comprising an arm control processor, said arm control processor being configured to synchronize moment of said position arms and said inspection arm such that said position arms move said robot body across the tube sheet while said inspection arm maintains said tool interface in a tube under inspection.

14. The tube inspection robot of claim 13, wherein said arm control processor is configured to access a tube test list and to create a robot movement path plan based on said tube test list.

15. The tube inspection robot of claim 14, wherein said arm control processor is further configured to move the robot while maintaining said tool interface in a tube under inspection based on a distance from the maximum reach of said inspection arm to a subsequent tube to be inspected.

16. A process for controlling a tube inspection robot comprising:

retrieving a list of tubes to be inspected, said list including tube location data, positioning a tool head on a robot inspection arm over a first tube to be inspected based on said list,

creating a path plan from said first tube to be inspected to a second tube to be inspected based on said list, and

controlling position arms on the robot to move the robot to a new position based on said path plan while controlling said inspection arm to maintain said tool head over said first tube.

17. The process of claim 16 wherein said robot comprises four position arms and said position arms and said inspection arm are SCARA devices.

18. The process of claim 16 wherein said step of controlling position arms on the robot to move the robot to a new position is based on location data of more than one subsequent tube to be inspected.

19. The process of claim 16 wherein moving the robot to a new position comprises removing a first tube gripper from a first steam tube, relocating a position arm on which the tube gripper is mounted and inserting the tube gripper in a second steam tube.

20. The process of claim 19, wherein only one tube gripper at a time is removed and inserted while the remaining tube grippers are locked into tubes.