Tube servicing robot

Abstract

A robot is disclosed for servicing a tube. The robot (10) has a chassis for supporting a servicing implement. The chassis has a longitudinal axis and front and rear support assemblies (14, 16) connected to the chassis at locations that are spaced from each other along the longitudinal axis. Each support assembly (14,16), has at least three traction devices (24, 24b, 26a, 26b) urged into contact with an inner wall of the tube. In the invention, at least two of the traction devices are motor driven and configured to enable the robot both to advance along the tube in the direction of the longitudinal axis of the chassis and to rotate about the longitudinal axis.

Description

[0001] Tube servicing robot

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a robot for travelling down the bore of a tube and capable of supporting implements that may be used to inspect, clean, service or repair the tube. The term “tube” as used herein is intended to include pipes and other conduits that are nominally circular in cross section.

[0004] BACKGROUND

[0005] Chemical plants employ tubes in a variety of applications to transport fluids of different types. For example, the tubes may be tubes of a heat exchanger, or they may be part of a bank heated in a furnace. The fluid flowing through the tubes may, depending on the application, be a liquid, a gas or a flowable solid.

[0006] To maintain the efficiency of the chemical plant, such tubes may require attention periodically. For example, in some application the tubes may be prone to fouling and require cleaning. In other application, the tubes may be prone to erosion or corrosion. Welds between tube sections may also on occasion require attention.

[0007] It is not economically viable to shut down a chemical plant for the purpose of servicing tubes. Instead, it is known to carry out operations on them while they remain in situ but are taken out of service, such as by being bypassed. There have previously been proposed robots that can travel inside a tube to carry out inspections or servicing operations. Examples of tube robots are available from, inter alia, Uomrobotics and Jettyrobot, see for example, htps: / / uomrobotics.com / robots / furo.html and htips. / Zwww.j eltyrobot. com . The traction devices used by known robots are designed to advance them only along the length of the tube. As the robots usually perform tasks around the entire circumference of the tube, their orientation is not of any importance.

[0008] SUMMARY OF THE INVENTION

[0009] According to the present invention, there is provided a robot for servicing a tube, the robot having a chassis for supporting a servicing implement, the chassis having a longitudinal axis, and front and rear support assemblies connected to the chassis at locations that are spaced from each other along the longitudinal axis, each support assembly having at least three traction devices to be urged into rolling contact with an inner wall of the tube, wherein at least two of the traction devices are motor driven and configured to enable the robot both to advance along the tube in the direction of the longitudinal axis of the chassis and to rotate about the longitudinal axis.

[0010] In some embodiments, the robot may include an attitude sensor to determine the orientation of the chassis relative to the horizontal. In such embodiments, a control system may be provided to cause the robot to rotate about the longitudinal axis, to maintain a desired orientation of the chassis relative to the horizontal.

[0011] When such a robot is used for inspection, as well as determining the position of a defect along the length of the tube, the robot can also determine the position of the defect in the plane normal to the longitudinal axis. These coordinates can be stored and used to enable the robot to return to the exact position of the defect, to enable an implement to conduct a repair.

[0012] In some embodiments, it is important for the chassis to be accurately centered in the tube. To achieve this aim, in some embodiments, the traction devices are mounted on the ends of independently adjustable arms. Distance measuring devices, such as lasers, may be used in such embodiments to determine the distance of points on the chassis from inner walls of the tubes and to control the individually adjustable arms to centre the robot within the tube. Independently adjustable arms also enable the robot to be used in tubes of different diameter and even to transition between sections of differing diameter. Indeed, such adjustable arms may also permit the robot to negotiate bends in a tube.

[0013] It would be possible for the traction devices to comprise only omniwheels. An omniwheel has rollers distributed about its periphery, each rotatable about an axis that is tangential to the wheel and lies within the plane normal to the axis of rotation of the wheel. In this way, an omniwheel can provide traction if rotated about the wheel axis, while offering little resistance to movement if the wheel is pushed in a direction parallel to the wheel axis. Thus, one omniwheels may advance the chassis longitudinally while another may cause the chassis to rotate about its longitudinal axis.

[0014] In an alternative embodiment, the traction devices may comprise mecanum wheels, each of the front and rear support assemblies having two powered mecanum wheels urged into contact with the inner wall of the tube. As is well known, depending on the direction of rotation of such wheels, the robot can be made to move parallel to the longitudinal axis of the chassis or to rotate about the latter axis. In such an embodiment, the other traction devices on the support assemblies may be freewheeling omniwheels that allow the chassis both to move longitudinally and to rotate about its own axis while encountering little resistance.

[0015] The robot of the invention is capable of use with most servicing and inspection implements but lends itself particularly to the use of arc spraying apparatus. It is known for erosion to cause thinning of the wall of a tube, but this tends only to occur near the vertically lowermost point. It is possible to strengthen the tube by thickening only selected areas around its circumference using the technique of arc spraying. In this technique, as its name implies, an arc is struck, usually between two wires, and the resulting molten metal is sprayed by means of a jet air onto a surface to be coated with the molten metal. Because the robot of embodiments of the invention can detect and control both its position and its orientation within the tube, it may be used to transport arc spraying apparatus, to repair areas of the tube where the walls have been thinned by erosion or corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

[0017] Figure l is a perspective view of a robot of an embodiment of the invention, and Figure 2 is a plan view of the robot in Figure 1.

[0018] DETAILED DESCRIPTION OF THE DRAWINGS

[0019] The drawings show a general configuration of a robot 10 for travelling along the bore of a tube so that the tube may be surveyed, serviced, or repaired. The robot 10 comprises a chassis 12, a front support assembly 14 and a rear support assembly 16 connected to the chassis 12, and a service assembly 18 mounted to the front support assembly 14.

[0020] The chassis 12 comprises four tubular members extending between the front and rear support assemblies 14, 16, on which is mounted equipment 15 that includes, sensors and a control system to be described below. The chassis 12 is dimensioned to fit within the tube with clearance, so that the equipment 15 mounted thereon is protected from contacting any deposits or debris on the bore of the tube. For further protection, the chassis may be covered by a casing (not shown for clarity). It will be understood that although the chassis of Figure 1 is shown as having four tubular members, it may comprise any number of members, whether tubular or not. Alternatively, the chassis may take a different form, such as a monocoque.

[0021] The front and rear support assemblies 14, 16 are like one another and will therefore be described together. Each support assembly 14, 16 comprises a frame 20, 22 attached to the chassis 12, the attachment being, for example, via mechanical fixings such as screws and bolts, adhesive, or welding.

[0022] Each support assembly comprises three wheels serving as traction devices, which are individually labelled 24a, 24b, 24c and 26a, 26b, 26c in the drawings but will be referred to below more simple as wheels 24 and 26. Each wheel 24, 26 is connected to the chassis by a respective adjustable arm 28, 30. The arms 28, 30 are pivotable relative to the frame 20, 22 using any means known in the art, such as mechanically (e.g. springs), pneumatically, hydraulically, or, as shown, electrically via motors 32. The pivoting arms 28, 30 serve to urge the wheels 24, 26 into contact with the inner wall of a tube and thereby provide traction. The pivotable arms 28, 30 allow the robot 10 to be deployed also in tubes of different diameters and can allow the robot to travel along a tube of which the diameter varies along its length.

[0023] To allow the chassis to be correctly centred, even if the tube does not have a perfectly circular circumference, the arms 28, 30 are preferably controlled individually. In this way, any sensors on the robot 10 can accurately record the position of any defects in the tube. The equipment 15 includes distance measuring devices, such as lasers, to determine the distance of points on the chassis from inner walls of the tubes and a control system to position the adjustable arms individually, to centre the robot within the tube.

[0024] It will of course be appreciated that the drawings only show one embodiment of the invention. The arms, instead of being rotationally moveable, may be linearly movable. Linear movement may be accomplished using arms that are slidable or telescopic in a radial direction with respect to the longitudinal axis of the robot 10.

[0025] The wheels 24, 26 positioned on the end of the arms 28, 30 serve to support the weight of the robot 10, and at least some of them are driven by motors 34 to propel the robot 10 along the tube.

[0026] It is important in the present invention for the robot and its chassis to be capable of rotating about the direction of travel, to position the robot accurately in a vertical plane. While this can be achieved using only omniwheels, which provide traction in one direction while offering little resistance to movement in a transverse direction, it is preferred for two of the wheels 24a, 24b; 26a and 26b of each support assembly to comprise individually powered mecanum wheels, which, depending on their relative directions of rotation, can both drive the robot longitudinally along the tube and cause the robot 10 to or rotate about its longitudinal axis. The remaining wheels 24c, 26c are preferably not driven but are omniwheels capable of supporting the robot while permitting it to move freely both along the length of the tube and while permitting it to rotate about its longitudinal axis. Thus, it will be seen in the drawings that the rollers of the wheels 24c and 26 having axes lying in the plane normal to the wheel axis and are therefore omni wheels, whereas the wheels 24a, 24b and 26a, 26b are mecanum wheels with rollers having inclined axes.

[0027] The equipment 15 mounted on the robot 10 may also comprise a gravity sensor to supply a signal to the control system indicative of the attitude of the robot 10. The control system may then control the motors 34 driving the wheels 24, 26, to rotate the chassis 12 about the longitudinal axis and maintain the robot in an upright orientation or any other fixed attitude, thereby allowing more accurate positioning data to be collected. The gravity sensor may be a mercury switch, acting in a manner analogous to a spirit level, or it may preferably comprise a MEMS sensor.

[0028] The service assembly 18 projects from the front of the front support assembly 14 via an adjustable arm 36 which may be adjusted using motors 38. A variety of service attachments may be mounted on the distal end of the arm 36, either individually or at the same time. Such attachments may include surveillance and recording devices to survey the topography of the bore of the tube to identify any areas of the tube wall that has become thinner due to wear; cameras to enable a visual inspection of the tube bore; welding, printing, or other systems to repair the tube wall.

[0029] It is a particular advantage of the robot of the invention that it may be used to transport arc spraying apparatus used to spray molten metal onto only a pre-selected part of the circumference of the tube.

[0030] When the robot is introduced into a tube, it will have various trailing supply pipes and cables, to carry electrical power, control signals, compressed air etc. The assembly 14 is termed the front assembly because it lies at the opposite end from the supply pipes and cables. It is not, however, essential for the front assembly be at the front while an operation is being performed. For example, while carrying out arc spraying, the robot may effectively be travelling in reverse so that the traction should not contact newly applied hot metal.

Claims

CLAIMS1. A robot ( 10) for servicing a tube, the robot having a chassis ( 12) for supporting a servicing implement, the chassis (12) having a longitudinal axis, and front and rear support assemblies (14,16) connected to the chassis (12) at locations that are spaced from each other along the longitudinal axis, each support assembly (14,16) having at least three traction devices (24,26) to be urged into rolling contact with an inner wall of the tube, characterised in that at least two of the traction devices (24a, 24b; 26a, 26b) are motor (34) driven and configured to enable the robot both to advance along the tube in the direction of the longitudinal axis of the chassis (12) and to rotate about the longitudinal axis.

2. A robot as claimed in Claim 1, wherein the robot includes an attitude sensor to determine the orientation of the chassis relative to the horizontal.

3. A robot as claimed in claim 2, wherein the attitude sensor is a MEMS sensor.

4. A robot as claimed in Claim 2 or 3, further comprising a control system to cause the robot to rotate about the longitudinal axis, to maintain a desired orientation of the chassis relative to the horizontal.

5. A robot as claimed in any preceding claim, wherein the traction devices (24,26) are mounted on the ends of independently adjustable arms (28,30).

6. A robot as claimed in claim 5, wherein distance measuring devices are provided to determine the distance of points on the chassis from inner walls of the tubeand to control the individually adjustable arms (28,30) to centre the robot within the tube.

7. A robot as claimed in any preceding claim, wherein each support assembly (14,16) comprises two individually powered mecanum wheels (24a, 24b; 26a, 26b) and one omniwheel (24c).

8. In combination, a robot as claimed in any preceding claim and an arc spraying apparatus mounted on the robot (10).

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