EP0547685A1

EP0547685A1 - Remotely operated apparatus for inspection or other work on structures

Info

Publication number: EP0547685A1
Application number: EP92203851A
Authority: EP
Inventors: Kjartan Vartdal; Per Sundal; Steinar Lovaas; Morten Rasmussen; Ingvar Vik; Hakon Haugland
Original assignee: Norsk Hydro Technology BV; Norsk Hydro ASA; Norsk Hydro Elektrisk Kvaelstof AS
Current assignee: Norsk Hydro ASA
Priority date: 1991-12-16
Filing date: 1992-12-10
Publication date: 1993-06-23
Also published as: NO914950D0; NO173924C; NO173924B; CA2085091A1; NO914950L

Abstract

A remotely operated apparatus for inspection of and/or other work on a structure, for example a welded joint on an offshore platform, consisting of a support frame (2) designed to be attached to and to move on the structure. An arm (4) is mounted so as to rotate on the frame (2) in both main directions in relation to the said frame. Furthermore, a steering carriage (5) is mounted so as to rotate at the front end of the arm (4). One or more tools (6) may be mounted on the carriage for the purpose of carrying out the required working operations.

Description

The present invention concerns a remotely operated apparatus for inspection of and/or other work on a structure, building or the like. The invention is particularly intended for use in connection with welded joints on underwater parts of an offshore platform, but is also intended for use in connection with welded joints and other structural details of a ship, a building or for example a space vessel.
Remotely operated vehicles are used for work on and around underwater parts of an offshore platform or rig. Such vehicles may be equipped with a manipulator arm which is operated from a remote control device.
In the course of the work, the vehicles must constantly be moved to new working positions. For this purpose the vehicles are equipped with wheels, caterpillar belts etc. and are held in position with magnets, vacuum, mechanical devices or the like.
British Patent Application No. 2.182.898 shows a remotely operated vehicle mounted on arms which extend around the circumference of a pipe. The mobility of the vehicle is very restricted, since it can only move along pipes or other longitudinally-oriented, pipe-like structures.
British Patent Application No. 2.161.040 further describes a vehicle which moves by means of rollers and which is kept in place by propeller devices; and PCT Patent Application No. WO 84/04733 shows a vehicle which moves and is kept in place by movable electromagnets.
The last two vehicles cited represent a more "common type" of remotely operated device which is relatively large and heavy, and for that reason cannot be used with structures where there is little space or a low working height. Another disadvantage of this type of vehicle is that, because of the design of the elements allowing propulsion (wheels, rollers etc.), they cannot be used on curved surfaces, which further limits their range of applications.
US Patent Application No. 4.720.213 shows an apparatus for the inspection and cleaning of welds on underwater structures which include pipe-shaped structural parts. The apparatus consists of a U-shaped bearing structure designed to be attached to and removed from the pipe-shaped structural parts. A rotating carriage is mounted on the U-shaped structure and is equipped with two manipulator arms designed to carry the required inspection or cleaning equipment.
The apparatus described in the above-mentioned US Patent Application appears to provide relatively good access to areas where there is little space and which are difficult to access - for example nodal points where several pipe-shaped structural parts are welded together. However, its range of applications is still limited, since the U-shaped bearing structure of the apparatus can only be used on pipe-shaped structures and cannot be used on other curved or flat surfaces.
Furthermore, the manipulator arms are inaccurate, since they consist of several components and many elements with an imprecise control system, and cannot be used for inspection equipment which requires great accuracy of placing and replicability of the action involved (i.e. the ability to carry out identical inspections at a later juncture). No practical application has therefore been found for the equipment described in the above-cited US Patent Application. Today, therefore, in all essentials, manual manpower - for example, divers in the case of underwater structures - is used for inspections requiring a high degree of accuracy.
There has long been a desire for equipment which can carry out eddy-current probes along welds on underwater structures. Such a probe makes considerably greater demands on accuracy than other typical operations carried out with remotely operated vehicles. Eddy-current probes must follow a particular path with great accuracy, and it is important that the probe is always correctly oriented in relation to the weld and its surface. It has been found that to carry out an eddy-current probe one must either use a manipulator arm with a more sophisticated control system than has been used hitherto, or special equipment must be developed to guide the eddy-current probe more reliably and accurately. The present invention relates to the latter alternative.
It has thus been the intention with the present invention to obtain a remotely operated apparatus which can eliminate much of the work of inspection and/or other work which is done manually by divers.
A further object has been to design such an apparatus so that it can carry out the operations in question, especially inspection and testing with a considerably higher degree of accuracy and thus a more reliable degree of detection than can be obtained with existing remotely operated vehicles and equipment.
The invention is characterized by having a support frame which is designed to be attached to, and to move on, the surface of a structure on which a working operation is to be carried out; an arm which is arranged to rotate on the frame in both main directions relative to the frame; a steering carriage mounted so it can rotate on the forward end of the arm; a means of pressing the carriage down on to the surface; means of moving and controlling the movement of the carriage on the surface; and a tool mounted on the carriage for carrying out the required working operation on the structure, as defined in the appended Claim 1.
Advantageous features of the invention are defined in the subordinated Claims 2-11.
Further features of the apparatus in accordance with the invention will be evident from the following description of a non-binding embodiment of the invention, where:

Fig. 1: shows, in perspective, a desirable embodiment of the invention while in use on a pipe node in an offshore structure; and
Fig. 2: shows, on a larger scale and in more detail, the invention viewed from above and from the side.

Figures 1 and 2 thus show an example of the invention in the form of an item of equipment or apparatus 1 consisting of a support frame 2 designed to move on and to be removed from a surface; an extended arm 4 which in this case extends through the support frame 2; and a steering carriage 5 connected with the arm 4 such that it is able to rotate (for example by means of a pivot) and designed to accommodate and bear at least one operative device 6. The support frame 2 consists of a device 18 - for example, a suction cup attachment or magnets - designed to hold the support frame 2 in a required position on a surface in relation to an area - for example a weld - which is to be inspected. The steering carriage 5 is equipped with a controllable steering wheel 7 on the front part and two wheels 8, 9 on the back part allowing the carriage to manoeuvre. In the embodiment shown here the carriage is pressed against the surface by the arm 4 which is in turn spring-loaded (not shown). But the carriage 5 may also alternatively be pressed against the surface by magnets, by a propeller device or the like, mounted on the carriage.
The arm 4 may for example be straight and designed in one piece, telescopic or in several parts (articulated). In the embodiment shown in the figures, the arm 4 is formed in one piece and movably mounted in the support frame 2. The arm 4 is mounted so it can rotate in both main directions as indicated by the arrows 19 and 20 in Figure 2. An electrically or hydraulically operated motor 13 is mounted in or on the support frame 2 and is designed to extend or retract the arm 4 in relation to the frame 2. The motor 13 may be furnished with a friction wheel or toothed wheel 15 which engages with a frictional surface or toothed bar (not shown) respectively on the arm 4.
The controllable steering wheel 7 is turned by a joystick (not shown in the drawings) by means of an electrical or hydraulic actuator or motor 12. The same joystick controls the operation of the motor 13 which extends and retracts the arm 4. The movement of the arm 4 and thus the speed of the steering carriage 5 are proportional to the displacement forward or back of the joystick, while the turning of the steering wheel 7 is proportional to the transverse displacement of the joystick. It would further be appropriate for the arm 4 to be equipped with limit switches (not shown in the drawings) which are able to stop the further operation of the motor 13 to prevent full extension of the arm.
It would be appropriate for the wheels 7, 8 and 9 to be furnished with sharp peripheral edges to achieve sufficient contact with the surface 3. It should however be remarked that the wheels of the steering carriage 5 may be furnished with other means of contact - for example rubber rings or the like.
In the embodiment shown in Figures 1 and 2, the steering carriage is equipped with a tool in the form of an eddy-current probe 6 for the inspection of a weld. (Figure 2 shows two probes 6, one on each side of the carriage).
The probe is mounted in a probe holder 10, mounted in turn on the steering carriage 5. The probe holder is designed to ensure an even contact pressure between the actual probe 6 and the weld surface, regardless of the position of the probe 6. The probe holder 10 must provide the probe 6 with the steadiest possible motion by preventing the probe from "catching" or moving in a rut because of irregularities in the surface. The probe holder 10 is also designed such that the probes are replaceable. To achieve the best possible access with the probes to confined spaces - for example between stays which cross each other at acute angles (down to 30°) - it is important that the probe holder 10 has a low construction height in the transverse direction.
The steering carriage 5 is in the embodiment illustrated designed to guide the probe 6 and the holder 10 at a constant speed along the weld. The length of a scan with the probe 6 once the steering carriage has been positioned could appropriately be about 50 cm. The steering carriage 5 must ensure that the probe 6 always remains in contact with the surface and maintains the required orientation in relation to the weld surface. To achieve this, the probe must at all times be oriented satisfactorily in relation to all its 6 degrees of freedom.
The degrees of freedom of the probe 6 can be controlled actively during a scan, passively or by pre-setting them at a fixed level. Figure 2 shows that the probe is suspended in a spring device 21 in the holder 10 and can be turned by means of an electric or hydraulic actuator or motor 14. No further details of the control of the degrees of freedom of the probe are shown.
The movement of the carriage is monitored by means of a video display unit (not shown) which is connected to a camera mounted either on the steering carriage 5 or on the frame 2. The main axis of the camera should be almost parallel with the weld or the area which is to be inspected or on which work is to be done, and the camera must be able to "see" the probe and the weld or the working area throughout the working operation.
The steering carriage 5 is connected with the arm 4 so as to rotate by means of a link 11. The link 11 must be able to maintain the steering carriage 5 in the required position and with the required orientation. Its must provide a satisfactorily firm, rigid attachment such that the control carriage 5 and the probe 6 operate as required during the desired job or scan.
As mentioned above, the steering carriage 5 is furnished with three wheels: a guide wheel 7 in front and support wheels 8, 9 at the back. This ensures that the carriage rolls and stands steady on the surface even when the surface is uneven or has a convex or double-convex shape.
To obtain the same effect, the frame 2 is similarly furnished with three supporting legs 16.
The apparatus as described in the present application is used and functions as follows.
The apparatus with its frame 2, arm 4 and steering carriage 5 are positioned on a structure - for example, a jacket frame for an offshore platform - by means of a remotely operated undersea vessel or the like. It is here assumed that the carriage 5 is equipped with an eddy-current probe 6 and that it is to test a weld zone between crossed pipe stays 3, 17 on the jacket frame. The frame 2 is therefore positioned on the pipe stay 3, close to the stay 17. An operator on board a ship or platform, in a control room or the like, can, by means of a video display unit, see the carriage 5 and steer it, first up to the weld and then along it, with a joystick as described above. The movement of the carriage 5 is produced by the arm 4, axially driven in relation to the frame 2, and the carriage is steered by means of the front guide wheel 7. The length of the weld area which can be inspected will be limited by the possible extension of the arm 4, or the radius of curvature of the stay 17, inasmuch as the arm 4 can touch the stay and prevent the further movement of the carriage before the arm has reached full extension if the stay has a small radius of curvature.
When the weld area has been inspected, the frame may be moved to a new position and a new area may subsequently be inspected. In this way successive inspections may be made of welds over long distances.
It should be noted that the invention is not restricted to the embodiment shown above. For example, the frame, instead of being equipped with supporting legs 16, may be equipped with powered wheels and may itself be remotely operated. Furthermore, the steering carriage, instead of being powered by the arm 4, may be self-powered.
In the case of the arm 4, this may as mentioned above be in the form of a rigid, straight bar as shown in the figures, or it may be articulated or telescopically designed. If it is telescopically designed, it would be most appropriate to use pneumatic or hydraulic power of a kind similar to that used for a piston/cylinder device.
Furthermore, as regards the underwater use of the apparatus described in relation to the invention, it will be most appropriate, because of pressure conditions and the risk of water penetration, to use hydraulic or pneumatic power to control all the functions of the apparatus. The energy necessary to power the apparatus will preferably be transmitted to the apparatus from a remotely operated vessel or the like through hoses or cables.

Claims

Remotely operated apparatus for inspection, for example, of a welded joint on an offshore platform, and/or for other work on a structure,
characterized by
a support frame (2), which is designed to be attached to and to move on the structure; an arm (4) which is mounted so as to rotate on the frame (2) in both main directions in relation to the frame; a steering carriage (5), mounted so as to rotate at the forward end of the arm (4); means of pressing the carriage down against the structure; means of moving and steering the carriage on the structure; and one or more tools (6) mounted on the carriage for the purpose of performing the required working operation on the structure.
An apparatus in accordance with Claim 1,
characterized in that
the arm (4) consists of a rigid bar which is movable axially.
An apparatus in accordance with Claims 1 and 2
characterized in that
the carriage (5) is powered through the arm, which is in turn powered by a motor (13) on the frame.
An apparatus in accordance with Claim 1,
characterized in that
the arm (4) is telescopic.
An apparatus in accordance with Claims 1 and 4,
characterized in that
the carriage (5) is powered through the arm (4), inasmuch as the extension and retraction of the arm is powered pneumatically, hydraulically or electrically.
An apparatus in accordance with Claim 1
characterized in that
the arm (4) is articulated.
An apparatus in accordance with Claims 1, 2, 4 and 6,
characterized in that
the carriage (5) is self-powered.
An apparatus in accordance with Claims 1 through 4,
characterized in that
the carriage (7) is pressed against the surface by means of magnets, a propeller device or the like, mounted on the carriage (5).
An apparatus in accordance with Claims 1 through 5 and 7,
characterized in that
the carriage (5) is pressed against the surface by the arm (4), inasmuch as the ring (4) is in turn spring-loaded.
An apparatus in accordance with Claims 1 through 9,
characterized in that
the frame (2) rests on three legs (16) and is held against the surface by magnets, a suction device (8), a propeller device or the like.
An apparatus in accordance with Claims 1 through 9,
characterized in that
the frame (2) is equipped with wheels, preferable three wheels, at least one of which is powered, and that the frame is pressed against the surface by magnets, suction cups, a propeller device or the like.