The invention relates to an underwater opera- _c ting ^" system comprising an underwater platform, equipment on the platform mounted as replaceable units, a rail track on the platform and an interven¬ tion or handling unit which can move along the rail track for removing the replaceable units and repla¬ cing them, said handling unit having a manipulator by 0 means of which an equipment unit may be isolated, grasped and placed in the handling unit, and by means of which a new equipment unit may be fetched from a storage in the handling unit and put in place on the platform. 5

Such a system is known from NO-PS 139 323, describing underwater production equipment for remote connection to underwater wells and for fluid produc¬ tion from wells under water. The underwater produc¬ 0 tion equipment is built so that the components easily may be connected and disconnected and removed and/or • replaced. Thus, the various sections of the platform and its equipment, including manifold equipment, valves, power plant and other equipment units and the 5 rail track on which the handling unit works, are removable by remote control and may be brought to the surface for repair and/or replacement of the under¬ water production equipment. If the maintenance work is to be performed on the underwater production n equipment, e.g. a manifold valve, a buoy is released by means of remote control. The buoy rises from the

- platform and brings along a line to the surface. The handling unit is launched from a vessel and is attached to the line. The handling unit sinks and 5 pulls itself down ^" to the underwater production equip¬ ment—along the line attached to the buoy. After having landed -on the rail track, the handling unit is secured to the rail track. By means of power supply from the surface through an electrical cable, the

handling unit is supplied with elctrical power for a motor which moves the handling unit along the rail track. A handling arm on the handling unit may be activated by power supply through said electrical cable. After having performed the necessary opera¬ tions, the handling unit moves back to the landing point, the attachment is released and the handling unit returns to the surface along the line. If the maintenance work cannot be handled by remote control, a man may be lowered in a bell attached to the hand¬ ling uni't. The handling unit is provided with its own power supply system, making it able to move along the rail track if the power supply through the electrical cable to the surface should fail. The man in any bell used may, if necessary, release the handling unit or release the bell from the handling unit in order for the bell to float to the surface. This known system has the disadvantage that one is dependent on connection to the surface. An object of the present invention is to provide an ^" underwater operating system which is remotely con¬ trolled during normal operation and where mainte¬ nance, replacement of units etc. may be performed within the framework of a total underwater system, i.e. one works without the necessity of surface con¬ tact, so that in fact one has an underwater system which is independent of the conditions on the sur¬ face. According to the invention, it is therefore suggested, in an underwater operating system as men¬ tioned above, initially to place the equipment units as such and/or their control means to a maximum degree in typical axes and in typical planes. Furthermore, it is suggested that the handling unit is designed as a load carrying, manned autonomous underwater vessel having docking feet for cooperation with the rail track, and with one or more external •manipulators which are movably mounted on the vessel

and adpated to the typical axes when the vessel is docked on the rail track.

The invention is primarily developed for use with so-called production installations, but the expression underwater operating system is also meant to include other installations under water having need for maintenance, replacement of units etc.

The load carrying manned autonomous underwater vessel is a central factor. Since it is load carry¬ ing, it can bring along equipment units and compo¬ nents from a base, which may be located in a suitable place, for instance on land. Since the vessel is manned, one obtains the advantage that- all handling and manipulation can take place "manually", i.e. during direct surveillance (through suitable windows in the vessel). Also automatic or automatically and remotely controlled components may be surveyed. Since the underwater vessel is autonomous, i.e. self- sufficient, one obtains the advantage that the manning - a larger crew is possible, for instance 5 - 10 persons - may stay several weeks on board, and- the vessel is completely independent of external energy supply when the vessel is at work on the underwater .platform, even though one may of course advantageously provide a power transfer connection between the vessel and the platform when the ^" vessel is docked on the rail track, so that the vessel may obtain power supply from the platform, provided that the underwater platform has cable or line connection with a suitable energy source placed at a remotely located offshore platform or on land.

The arrangement of the equipment units and their control means (couplings, control spindels, attachment bolts, signalling means etc.) in typical axes and 'in typical planes simplify the manipulating operations, and the positionable mounting of the manipulators, on the vessel, adapted to said typical axes when the vessel is docked on the rail track,

further adds to simplifying the manipulations to be performed.

Here, the meaning of axes and planes is that the components to be handled by the manipulator or manipulators on the underwater vessel, are fitted into a coordinate system which, in addition to said simplification of the ^* manipulating operations, pro¬ vides the possibility of mutual adaptation of co - ponents, tools and manipulators and also permits defined operations, particularly the use of a CAD system (the drawing of the equipment fed into a CAD system in the control so that the control system may "see" the equipment and any obstructions). By "feeling" reference points on the equipment (e.g. a production tree) the manipulator/tool will obtain reference data in its data assisted control. Addres¬ sing may take place based on known positioning of the tool with respect to the equipment. The positioning in typical axes and planes will also facilitate the use of television camera or "acoustic camera" for sending close-up pictures to the operator on board the underwater vessel. At larger depths one must expect poorer visibility and light conditions and therefore cannot entirely rely on pure manual (visual) control.

Use of a load carrying, manned autonomous underwater vessel provides for the possibility of positioning underwater operating systems also at larger depths, i.e. depths outside the usual reach of divers, and a particular advantage is that the new system will be very well suited for use in arctic waters (below the ice) .

Today, strict requirements are imposed on underwater operating systems for reasons of safety. Thus, it is ^" required that equipment units and compo¬ nents shall have very long life and be particularly reliable, just because it is a question of installa¬ tions which have difficult access and where failure

or faults may have catastrophic consequences. The new underwater operating system ^' provides for shor¬ tening the "warranty period" of equipment units and components, i.e. one may leave the long term consept required today because by using the underwater vessel one may quickly and relatively simply replace and repair/maintain units and components. Seen as a whole, one thus obtains a system where in a wet en- vironment one comes close to the working and opera¬ ting conditions prevailing in a dry environment.

The use of the underwater vessel, which will be relatively large, will make it possible to "spread" the equipment more. For instance, a manifold area may be designed larger, i.e. be placed over a larger area covered by manipulators of ^" the underwater ves¬ sel, and single components may be dimensioned and located in more accessible places. A so-called "pig launcher" may for instance be transported along with the underwater vessel and placed in the pipeline system as needed, this being possible without the connection to a vessel on the surface, as necessary today.

Some components may be simplified since they only have to be made for direct handling. This is for instance true for valves for closing off sections where work/manipulations/replacements are to be per¬ formed.

In an underwater operating system where the . equipment comprises productions trees and correspon¬ ding manifold equipment, the production trees may . advantageously be placed in line, with the manifold equipment placed along this line, the rail track ex¬ tending above the manifold. When the vessel is docked on the rail track, the manipulators may be used on both the production trees and the underlying manifold equipment.

Preferably, the rail track is placed parallel with said line. The underwater vessel may then be

docked so that its longitudinal axis is perpendicular to the rail track and said line, and the underwater vessel may be moved transversally along the rail track. The production trees may be handled by mani¬ pulators in the front part of the vessel, while one or more manipulators under the vessel may service the manifold equipment, the vessel being docked on the rail track with the axis of the vessel parallel to the typical axes in the manifold.

Advantageously the rail track may comprise a portion outside the equipment area of the platform, so that the vessel may dock without fear of collision with the equipment units on the platform. This pro- vides additional safety.

According to a further aspect of the invention, the equipment units are to the greatest possible extent designed as modules in a containerized system, where each "container" module includes a frame struc- ture ^' with identical attachment and fixation points from one module to the other. The cargo room of the underwater vessel ^' is provided with corresponding points for attachment or supension of the modules during transit. Preferably, each frame structure comprises at least one top frame, having attachment points for a lifting yoke and attachment/suspension points for cooperation with corresponding points in the cargo room.

Advantageously, the rail track and the under- water vessel comprise mutually form closing drive means, for instance a rack and pinion. This may be advantageous, often also necessary, since slime de¬ posits may prevent the necessary friction between rail track and supporting wheels. The underwater vessel will also be close to a buoyant condition, with corresponding low surface pressure against the rail.

The underwater vessel may preferably comprise locking means, e.g. claws, for locking to the rail.

In the following, the invention will be more closely described with reference to the drawings, where Fig. 1 shows a plan view of an underwater plat¬ form, with a docked underwater ^' vessel,

Fig. 2 shows the platform in Fig. 1 seen from the left side,

Fig. 3 shows the underwater platform seen from the lower end in Fig. 1, on a larger scale.

Fig. 4 shows a section through the underwater vessel shown in part in Fig. 3,

Fig. 5 shows a more schematical portion of an underwater platform as in Fig. 1, where the rail track is extended to outside the equipment area of the platform,

Fig. 6 shows a schematic side view of the front part of an underwater vessel with manipulators, to¬ gether with a production tree, Figs. 7 and 8 show an end view and a plan view respectively, of the underwater vessel and the production tree in Fig. 6,

Fig. 9 shows an equipment unit hanging in a lifting yoke, and Fig. 10 and 11 show examples of locking of equipment units in the cargo room.

The underwater platform shown in Figs. 1 - 3 is a production platform which is placed on the sea floor 1. The production platform 2 is in a conven- tional manner built from strong pipe elements 3 and beams 4, which are welded together so as to form a framework. The production platform shown includes four production trees 5, 6, 7 and 8. Each produc¬ tion tree is in the usual manner connected to a well. The number of production trees is here chosen quite incidentally, and an underwater platform may of course comprise a larger or smaller number of produc¬ tion trees.

The production trees 5 - 8 are, as is apparent

from Figs. 1 - 3, arranged on a line Y-Y. Each production tree has a vertical axis Z-Z, represen¬ ting a so-called typical, axis. From Figs. 2 and 3 it appears that each production tree, see produc¬ tion tree 5 in Fig. 2 and production tree 7 in Fig. 3, has its control means 9, 10 and 11, respec¬ tively, arranged in the typical axis and in typical planes A, B, C, D, E (Fig. 3). In Fig. 2 one may also regard the drawing plane as a typical plane where the control means 9 and 10 lie.

Another typical axis is X-X, see Fig. 1. The manifold equipment and other equipment units are arranged along such axes X-X in the plan view in Fig. 1. In Fig. 3 the- axis X-X lies in the paper plane, and the paper plane also represents a typical plane for locating equipment units.

Along the line Y-Y, along which the production _. trees 5 - 8 are aligned, the underwater platform 2 is provided with a manifold equipment area 12. The equipment, like the production trees, is known per se, and should need no further explanation.

Above the manifold equipment area 12 a rail track in the form of two rails 13 and 14 extends. The rail track 13, 14 extends parallel to the line of production trees 5 - 8. An underwater vessel 15 is shown docked on the rail track 13, 14 in a position adjacent the production tree 7. This under¬ water vessel 15 is a load carrying manned autonomous underwater vessel dimensioned and fitted to provide room for a larger crew, for instance 5 - 10 persons, and for longer stays in submerged condition (up to several weeks) .

The underwater vessel 15 is designed with a pressure hull 16 (see Figs. 3 and 4). Under the pressure hull 16 the underwater vessel has a cargo room 17, which outwardly is limited by side walls 18, 19 pivotable towards the outside. In the front part, in front of the forward end of the pressure

hull 16, a room 20 is present, closed by bow ports 21.

Along the belly of the pressure hull 16, two rails 22, 23 extend, the rails forming a rail track for a trolley carriage 24. This trolley carriage 24 carries a belly manipulator 25. Furthermore, two rails 26, 27 are arranged under the belly for one or more travelling crabs 28 supporting a lifting yoke ²⁹ -

In Figs. 3 and 4 the manipulator 25 is shown inside the cargo room in a retracted rest/transit position. A working position is shown in broken lines in Fig. 4. The travelling crab 28 and the lifting yoke 29 serve for handling equipment units suspended in the cargo room 17. The manipulator 25 is used for performing necessary work on the plat¬ form.

In the room 20 two bow manipulators 30, 31 (see Figs. 6 - 8) are arranged. These manipulators may travel on vertical, rails 32, 33. The rails 32, 33 may be moved horizontally in suitable guides 34, 35, as indicated with the double arrows in Fig. 6. Up front in the pressure hull 16 a large acrylic window 36 is arranged, providing a good view for the opera¬ tor 37 controlling the manipulators from inside the acco odation of the pressure hull. Corresponding large windows (not shown) are- arranged in the belly of the pressure hull in order for the operators to have visual control of the belly manipulator 25 and the lifting yoke 29.

In the cargo room 17 in Fig. 3, dash-dot lines indicate equipment units designed like modules in a containerized system, i.e. each module lies inside a parallelepipedic "frame". Each such "container" module 38 may advantageously comprise a frame struc¬ ture (not shown) having at le'ast one top frame With the attachment point for the lifting yoke 29 and with attachment-suspension points for cooperation with

o

corresponding points in the cargo room 17. Conven¬ tional locking and fixing techniques for conventional containers may advantageously be used. . Thus, the frame structure may be provided with extending locking ears intended for locking cooperation with suitable hook attachments in the cargo room where the modules may be suspended during transit.

In Fig. 9 an example is shown of a frame struc- ture with corresponding equipment unit. The frame structure is designated 41 and the equipment unit 42. The frame 41 and the integrated equipment unit 42 hang from the lifting yoke 29, which in turn is sus¬ pended for raising and lowering in the travelling crab 28 by means of lines 43. The manipulator 25 is used for controlling and orienting the equipment unit 42.

Fig. 10 and 11 show schematically how a containerized unit 38 may be suspended and locked in transit position in suitable hooks in the cargo room, the unit 38 being provided with extending locking ears 45, designed as shown in Figs. 10 and 11. The locking ear 45 has a hole 46 for engagement of a locking pin 47. The locking pin 47 is driven by a ^" small working cylinder 48. Corresponding hooks, possibly without a lock, may be used at a lower level for "parking" the equipment units.

Fig. 5 shows a variant of the platform in Fig. 1. The difference is that in Fig. 5 the rail track 13, 14 in Fig. 1 is extended by the rail sections

13', 14', so that the underwater vessel 15 may dock outside the equipment area of the platform, i.e. the area where the productions trees and manifold equip¬ ment etc. are located. The vessel 15 may thus dock without danger of collision with equipment units on the platform and may thereafter run inwards along the " ^• rail track. '

The underwater vessel is provided with four telescopic legs 39, which at their respective ends

t have running wheels 40 for engagement with the rails 13, 14. After docking, the position of the under¬ water vessel may be adjusted by means of the two telescoping legs 39, and by means of drive means (not shown) acting on the wheel sets 40 the underwater vessel may move along the rails 13, 14. In desired position adjacent a production tree 7, the under¬ water vessel may be locked to the rail track utili¬ zing means not shown, which will be well known to the skilled person.

In the above, an underwater platform resting on the sea floor is described. The invention is of course not limited to such an underwater platform. The underwater platform may thus be the upper com¬ pletion of a tower-like structure resting on the sea floor, by means of which one may reduce the working depth of the platform and the underwater vessel.

Furthermore, one may envision a curved rail track for the underwater vessel. It would also be possible to dock the vessel on a rail track like a turn-table located centrally in an underwater plat¬ form.