METHOD AND MACHINE FOR THE LAYING DOWN OF UNDERWATER PIPES AND CABLES

Abstract: A method for the laying out of a cable (11) under water is executed in one single cycle of operations: (a) digging of a trench, for example by means of a bucket-type digger (2), (b) laying down of the cable (11) by means of pressing-down elements with rollers (9, 10), and (c) the filling of the trench by means of a conveyor (25) and a discharge shaft (13) which lead the excavated bed material back into the trench on top the cable (11). A machine for the execution of the method has a main chassis (3) and a carriage (29) displaceably mounted hereon, which supports the excavation, the laying-down and the filling-in elements. Both the main chassis (3) and the carriage (29) have upwardly and downwardly movable legs (5 and 4 respectively), and by suitable control of the upwards and downwards movement of the legs and the mutual displacement of the chassis (3) and the carriage (29), the whole machine can be made to "walk" along the sea bed (1). In one form of embodiment (not shown) the machine is arranged to deposit a concrete pipe on the bottom of the trench by means of a sliding extrusion mould. The machine can operate submerged as shown and is controlled via a remote-control cable or, in the embodiment not shown, can be provided with a cabin with control arrangements and possibly a drive engine and other equipment. In the event of an interruption in the moulding operation, a tapered end is produced which locks the "old" length of pipe together with the length which is moulded later.

Description: METHOD AND MACHINE FOR THE LAYING DOWN OF UNDERWATER PIPES AND CABLES. ,This invention relates to a method of laying long pipes or cables under a sea, lake or river bed, said method being of the kind as defined in the preamble of claim 1 Hitherto used methods of this kind comprise the three stages as defined in the preamble of claim 1, namely the digging-up stage, the laying stage and the filling-in stage, and these three stages have been executed as three separate working operations, often with appreciable periods of time between each stage. This has given rise to considerable disadvan¬ tages. After the digging-up stage, there has thus been a great risk of the sanding up of the excavated trench whiα_ι, in certain cases, could even occur very quickly. When laying down waste water pipes, out of regard for handling there have been used re¬ latively light pipes, which under unfavourable con¬ ditions could be influenced by water currents or, in the event of them being filled with air with a view to blowing out, could simply float up to the surface whether or not they were more or less covered by bed material, for example sand. A further disadvantage could arise in that the excavated bed material could be carried away by the water currents before the pipe is layed in the trench, and this material would thus not be immediately available for the closing of the trench at the filling-in stage. It is the object of the present invention to provide a method of the kind defined in claim 1, whereby the above-mentioned disadvantages can be avoided, and OMPI /_ > WIPO - this object is achieved by a method which in accor¬ dance with the invention is distinctive in that one proceeds in the manner as defined and characterized by claim 1. With this use of a common supporting means for those elements with which the above-men¬ tioned stages are carried out, it is possible to ex¬ ecute the three stages in immediate connection with one! another, hereby avoiding the sanding up of the trench between the first and the second stage, in that the only time which elapses between the execu¬ tion of these two stages is that required to move the supporting means forward from that position at which the excavating element is situated at the rel¬ evant point, to that position at which the laying down elements are situated at the same point, which in practice involves only a few minutes or fractions of a minute. Moreover, the excavated material will be placed*back in the trench before the water cur¬ rents have time to wash it away. An expedient embodiment for the method in accordance with the invention for the laying of one or more li¬ quid-conveying pipes is defined in claim 2. By form¬ ing one or more pipes, for example of concrete, on the bottom of the trench, by consecutive on-site moulding, it is possible - without giving rise to handling problems, since the material introduced is in mass form and not piece form - to mould pipes which are sufficiently heavy to prevent that they are carried away by the current or, when filled with air, floating to the surface. Where waste water pipes are involved, the moulded pipe can either be used as it is or, af-cer having been moulded, an "in- nertube" or lining can be drawn through the pipe by means of a wire which, with the help of the moulding "gTB.E_ ) OMPI elements, is gradually drawn through the pipe as the pipe is formed. The invention also relates to a machine for the ex- ecution of the method, and this machine is charact¬ erized by the construction and arrangement as defin¬ ed in claim 4. With the construction as defined in claim 5, it is possible for the machine to "walk" along the bottom, in that during the actual working operation it is possible to convey the common support means in a sliding manner on the main chassis, which by means of its lowered legs stands on the bottom., whi_be dur- ing a transport operation, during which the legs of the main chassis are drawn up and the chassis is * supported by the common supporting means, it is pos¬ sible t& move the main chassis forward in relation to the now stationary common supporting means. The embodiment of the machine as defined in claim 6 is particularly well-suited to the moulding of one or more pipes on the bottom of the trench. With the embodiment of the machine as defined in claim 7, it is possible - in the event of a possible interruption of the moulding process, which other¬ wise it is assumed will be carried out continuously - to produce a non-radial surface on the end of the already moulded pipe section, hereby providing a better mutual locking of this pipe section with that which is moulded later, than what would be achieved by, for example, a plane radial end surface. By neans of the arrangements as defined in claim 10 and possibly claim 11, the machine can be held at O PI the correct level, at the correct angle (or horizon¬ tal position) and in the correct direction of trav¬ el. The invention will be described in closer detail in the following and with reference to examples of em¬ bodiments of a machine in accordance with the inven¬ tion and parts thereof as shown in the accompanying drawings, where fig. 1 shows an example of an embodiment of a machine which operates submerged in the laying of an electric cable, ' fig. 2 shows an example of an embodiment of a machine which operates at less depth, and which therefore extends up out of the * water, and which is arranged for the moulding of a pipe, and fig. 3 is a section through a part of the mach¬ ine shown in fig. 2. The machine shown in fig. 1 consists of two main components, namely a main chassis 3 and a carriage 29. In the example of the embodiment shown, the mach¬ ine is arranged for the laying of an electric cable 11 under a sea bed 1. During the process of laying the electric cable 11, the main chassis 3 stands stationary on the sea bed 1, while the carriage 29 moves along a carriage track 6 which is mounted on or forms part of the main chassis 3. The main chas¬ sis 3 is supported on the sea bed 1 by means of hy- draulically upwardly/downwardly adjustable legs 5 which, in the position shown, are extended to make contact against the sea bed and thus support the weight of the main chassis 3 and the carriage 29 ' borne by said main chassis 3. The carriage 29 also has hydraulically upwardly/downwardly adjustable legs 4 which, in this working position, are drawn up and do not touch the sea bed 1. On the carriage 29 is mounted a downwardly extending trench digger which, in the example shown, consists of a digger 2 of the bucket-chain type, but which., can also take other forms. • The digger 2 digs up the material from the sea bed 1, thereby forming a trench in which the electric cable 11 is layed down by means of holding-down and/or pressing-down arran- gements 9 and 10, which as indicated can be provided with rollers to reduce the frictional resistance in relation to the the electric cable 11. The electric cable 11 "is*introduced in a known manner from a sup¬ ply spole which can be mounted in a vessel in front of the machine, i. e., in fig. 1 to the left of the machine. The excavated bed material is carried from the upper end of the digger 2, by means of a horiz¬ ontal conveyor 25, astern to a discharge shaft 13, through which as. indicated the bed material falls back into the trench formed by the digger 2, thus covering the electric cable which has been laid in said trench. It will be obvious that the trench is open only for the time it takes for the carriage 29 to travel a distance corresponding to that between the digger 2 and the outlet of the discharge shaft 13, during which time the risk of the trench being "drifted up" as a result of bed sand being carried along by strong water currents is very small. This risk can be reduced further by providing the car- riage 29 with lengthwise baffle plates (not shown) , OMPI . WP the lower edges of which lie close above the the bed or cut down into it slightly, in that the baffle plates are supported by supporting elements capable of moving upwards and downwards, for example hydrau- lie cylinders. The feeding of the carriage 29 along the carriage track 6 is effected by means of traver¬ se mechanisms (not shown) , for example hydraulic cylinders. When the carriage 29 has reached right along to the forward end of the main chassis 3, i.e., to the end lying to the left in fig. 1, the legs 4 of the car¬ riage are lowered until they abut the sea bed 1 and support the weight of the carriage 29 and - support- ed by the carriage through the carriage track 6 - also the main chassis 3, the legs 5 of which are then lifted free of the sea bed 1. The traversing elements ^Eor the carriage 29 are now activated in the opposite direction, whereby the oppositely dir- ected relative movement between the carriage 29 and the main chassis 3 results in the latter being moved forwards, i.e., towards the lef in f g. 1, until the aft end of the carriage track 6 has reached for¬ ward to the aft end of the carriage 29. The legs 5 cf the main chassis are now lowered again, and the legs 4 of the carriage are lifted, after which the carriage 29 can again be fed forwards during the ex¬ cavation of a new stretch of trench, the laying down of a further length of cable and the filling in of the trench by means of the elements 2, 9 and 10 and 25 and 13 respectively, and as already described in the foregoing. Where their vertical movements are concerned, the legs 4 and 5 on the carriage 29 and main chassis 3 "gU EA OMPI respectively can be controlled by elevation and lev¬ el control arrangements (not shown) , so that the trench acquires the desired depth and slope (or lack of same) . Moreover, between the carriage 29 and its legs 4 and/or between the main chassis 3 and its legs 5, mechanisms such as hydraulic cylinders can be inserted to effect turning and sideways move¬ ments, whereby possible deviations from course can be corrected for or the course changed. This is eas- iest to carry out while the relevant set of legs 4 respectively 5 are drawn up from the sea bed, in that the load on the supporting elements which must transfer the weight of the carriage 29 respectively the chassis 3 to the relevant legs 4 respectively 5 is, in such an event, at its minimum. The control of the level, slope and .course regulation achieved by means of the arrangements already mentioned can be effected automatically by means of depth sensors, gradient sensors and navigational equipment of the kind suitable for the purpose, in that especially the course regulation can be carried out most expe¬ diently by means of a laser beam from a permanently mounted beam arrangement, for example positioned ashore. As is known, the laying of electric cables on the sea bed if often carried out at great depths, which is why in this case it is most expedient to allow the machine to be remote controlled, for example from the same vessel from which the electric cable 11 is supplied, through a remote control cable 8. In such a case the position of the machine can be supervised by means of a marker bouy 26 secured to the machine. The holding-down and/or the pressing -down arrangements 9 and 10 can be influenced in the upwards and downwards direction by means of the hydraulic cylinders 27 and 28 respectively. Although it is not immediately apparent from the drawings, the machine shown in figs. 1 and 2 has a not inconsiderable extent in the "thwar ships" dir- extion, this being necessary with regard to the sta¬ bility. The legs 4 and 5 thus represent pairs of legs rather than single legs and - precisely with regard to the stability - it is most appropriate to position the legs at the greatest possible distance from the "fore-and-aft" centre line of the machine. The machine can be equipped with underwater televi- sion cameras, possibly remote controlled, for the supervision of the work field, i.e., the area around and between the digger 2 and the discharge shaf 13, but in certain cases also to keep a watch on the places where the legs 4 and 5 are lowered down on to the sea bed 1, partly to ensure that the legs get a good foundation, and partly to ensure that they are not lowered, for example, on top of earlier laid ca¬ bles, wreckage or the like.. Fig. 2 shows an example of an embodiment of a mach¬ ine arranged for the laying of a waste water pipe under the sea bed 1 by the progressive moulding of a concrete pipe 20 in the excavated trench. The ex¬ trusion mould arranged in connection herewith is shown in more detail in fig. 3. In this machine the parts indicated with the reference numbers 2-6, 13, 25 and 29 have the same function and possibly the same form as the parts indicated with the same ref¬ erence numbers in the machine shown in fig. 1. Since the functions of these parts have already been des- O PI cribed, these parts need not be described anew. Where the digging up of the bed material and the filling of the excavated trench are concerned, the machine shown in fig. 2 functions in the same manner as that shown in fig. 1, and the same applies for the already described stepwise progression of the machine by means of relative movement between the main chassis 3 and the carriage 29 and the raising and the lowering of legs 5 and 4 respectively. The progressive moulding of the " concrete pipe 20 is effected by means of an extrusion mould 18 which is secured to the supporting legs 16 and 17, the upper ends of which are secured to the hydraulic cylinders 27 and 28, thus allowing the mould 18 to be raised and lowered and possibly be given some degree of slope. While the carriage 29 is moving forwards, a cement mass is pumped through a cement-tube 19 into the forward end of the mould 18, the forward end of the mould 18 being closed and the aft end open ar¬ ound a mould core 21, so that through the ring-form¬ ed opening between the mould 18 and the core 21, a concrete length in the form of pipe 20 is pressed out. To prevent newly-moulded pipe 20 from collaps¬ ing as a result of the external pressures, the open end, i.e., the end at which the moulding commences and which it is assumed will lie to the right in fig. 2, is constantly held filled with liquid, for example water, under suitable pressure, for instance by connecting said commencing end to a well in which the water level is held so much higher than the level at which the pipe is lying that the pres¬ sure is sufficient to prevent the pipe collapsing as a result of the pressure from the surroundings, i.e. the water pressure and the pressure from the bed material discharged back into the trench. In some cases the inside of the newly— oulded pipe 20 can be kept under supervision by securing sensors or a tel¬ evision camera to the mould core 21, with the view among other things of avoiding the collapse of the pipe. The water level in the above-mentioned well can be controlled in a known manner by means of lev¬ el sensors, pumps and valves. As will be seen from fig. 3, the forward end of the ring-formed space between the mould 18 and the core 21 is closed by an end cone 22. In the event of it being necessary to interrupt the moulding process - which is otherwise assumed to be carried out on a round the clock basis - for so long that the con¬ crete has time to stiffen or harden - the object of the end coiϊe 22 is to form a tapered end on the pipe 20. The tapered end thus formed enables the length of pipe 20 which is moulded at the next opportunity to be connected to the already stiffened or hardened pipe end with a conical coupling, whereby mutual al¬ ignment is achieved beween the old and the new pipe. This alignment control could not be achieved with, for example, ends which are cut off straight. From fig. 3 it will also be seen that a movable up¬ per part of the mould 18 can be displaced - as indi¬ cated by the stippled lines - by means of a hydrau- lie cylinder 23, with the view of providing the pos¬ sibility for the blowing out and then flushing the whole length of the pumping-in system, for example in the event of the suspension of operations. Fig. 3 also shows an eye 24 secured to the mould core 21. The eye 24 is provided for the anchoring of a wire OMPI or line which, during the moulding of the pipe 20, is drawn through the full length of the pipe and used, after completion of the moulding, to pull a lining or innertube through the pipe, whereby the the inside of the pipe is lined. In the event of the pipe 20 having to be moulded with bends or elbows, i.e., a change in direction, this can be carried out by mounting or inserting a muff on the end of the pipe, for example in the conical ending formed by the end cone 22, said muff having the necessary an¬ gular deviation, after which the moulding is contin¬ ued out from the muff. To reduce the friction under the progressive move- ment of the extrusion mould, the mould surfaces, i.e. , the inner surface of the mould 18 and the out¬ er surface of the core 21, can be coated with a low -friction material such as polytetra luorethylene. For the same purpose, the outer surface of the mould 18 can be clad with a perforated plate through which water is pumped out under pressure, thus "lubricat¬ ing" the surfaces on which the mould slides along the bed material. The machine shown in fig. 2 is provided with a cabin 15 above the surface of the water, said cabin being mounted on suitably arranged supports 7 and 14 on the main chassis 3. The cabin 15 can contain a wheel house with control equipment for the machine's var- ious working parts and moving elements, which in this case are thus not remote-controlled as in the example shown in fig. 1. The energy for the activation of the working parts and the moving elements as well as for the supervi- oREΛ ( - O°MPHI \Λ, WIPO sion- and position-controlling equipment can be pro¬ vided in a suitable known manner. If the working parts and moving elements are arranged to be activa¬ ted hydraulically, as described in the foregoing, the energy for the example shown in fig. 1 can be supplied through delivery hoses from the remote-con¬ trolling vessel, and in the example shown in fig. 2 from a combustion engine, preferably a diesel eng¬ ine, mounted in the cabin 15 and driving a hydraulic pump unit suitable for the purpose. It is expedient that the control of the upwards and downwards movement of the legs 4 and 5 can be effec¬ ted jointly for each set of legs, so that the rais- ing and the lowering of the v legs is synchronized, and also individually with the view to adjustment for unevenness in the sea bed or " changes of the slope in relation to the sea bed. When work is first to be commenced, one can either dig out a hollow into which the digger 2 can be low¬ ered, or alternatively the digger 2 can be mounted on the carriage 29 in a vertically adjustable man¬ ner, so that it can dig itself down from a start position over the sea bed. The control of the level, the slope and/or the course of the machine can be effected in an exped¬ ient manner by means of automatically operating con- trol elements which work in conjunction and accord¬ ance with suitably arranged sensors for the relevant parameters. The method can also be used for the burying down of pipelines already laid on the sea bed, for example OMPI gas pipes consisting of steel tubes casted in con¬ crete. This can be carried out by providing the ma¬ chine with a guide, between which the laid-out pipe is placed so that a digging unit, for example a dig- ger of the double bucket-chain type, can dig down on both sides of the pipeline. The necessary water and air jets are mounted on the internal side towards the pipe, so that the material under the pipe can be loosened and then dug out and/or sucked away. In this manner it is possible to secure and safeguard already laid-down pipelines with the machine and the method according to the invention. -^T E ^ OMPI

Claims: C L I M S 1. Method for the laying of lengthy pipelines or anchoring elements such as, for example, liquid-con¬ veying pipelines (20) or electrical power or signal cables (11) under the bed (1) of a sea, lake or riv- er, said method being of the kind including the fol¬ lowing steps: a) the bed material is progressively dug up to form a trench, b) that or the lengthy elements (20, 11) are pro- gressively laid in the bottom of the trench, and, c) the bed material excavated during step _ is placed back in the trench around and/or on top of that or the lengthy elements (20, 11) laid • in said trench during step b_, c h a r a ct e r i z e d by d) the use of elements (2, 9 and 10 or 18, respec¬ tively 25 and 13) in the carrying out of said steps <_, b and £, said elements being secured to a common supporting element (29) which is moved forwards in that direction in which said progressive operations are carried out. 2. Method according to claim 1 and for the laying of one or more liquid-conveying pipelines (20) , c h a r a c t e r i z e d in that for the execution of the second step (h in claim 1) , elements (18 etc.) are used which are arranged for the progressive moulding of one or more pipes (20) in the bottom of the trench (figs. 2 and 3) 3. Method according to claim 1 and for the laying of one or more electric cables (11) , c h a r a c t ¬ e r i z e d in that for the execution of the second step (b_ in claim 1) , elements are used for the lay¬ ing out and the pressing down of the cable or cables (11) on the bottom of the trench (fig. 1) . . Machine for the execution of the method accord¬ ing to claims 1-3, c h a r a c t e r i z e d in that it includes a) elements (2) for the progressive excavation of the bed material in the..forming of a trench, b) elements (9 and 10 or 18) for the laying of the lengthy elements (20, 11) on the bottom of the trench, c) elements (25, 13) for returning the bed mater¬ ial excavated by the excavating elements back to the trench, around and/or on top of the lengthy elements (20, 11) laicl therein, and d) a common supporting element (29) which supports the above-mentioned working elements and is arranged to be conveyed in the machine's forwardly progressive working direction. 5. Machine according to claim 4, c h a r a c t - e r i z e d by, a) that it includes a main chassis (3) which can be supported on the sea bed (1) by means of legs (5) which can be moved upwards and downwards, b) that the common supporting element (29) is arran- ged to be displaced in relation to the main chassis (3) by means of track elements (6) , through which the main chassis can both support and be supported by the common supporting element (29) , and c) that the common supporting element (29) also in- eludes supporting legs (4) with which it can be sup- ported on the sea bed (1) , and which similarly can be moved upwards and downwards. 6. Machine in accordance with claims 4 or 5 and chiefly for the execution of the method in accord¬ ance with claim 2, c h a r a c t e r i z e d in that the pipe-laying elements (claim 4, section b) comprise at least one sliding extrusion mould (18) with corresponding supply arrangements (19) for the moulding material. 7. Machine in accordance with claim 6, c h a r ¬ a c t e r i z e d in that the forward end of the sliding extrusion mould (18) includes a closing el- ement (22), the-, surface of which facing the inside of the mould is essentially non-radial in relation to the longitudinal axis of the extrusion mould (18) , said surface being preferably conical (fig. 3) . 8. Machine in accordance with claims 4 or 5 and chiefly for the execution of the method according to claim 3, c h a r a c t e r i z e d in that the lay¬ ing elements (claim 4, section b) include at least one set of holding-down and/or pressing-down arrang- ements (9, 10), preferably equipped with rollers, for the holding down and/or the pressing down of one or more electric cables (11) in or on the bottom of the trench (fig. 1) . 9. Method for the execution of the procedure in accordance with claim 2 with the use of a machine according to claim 6, c h a r a c t e r i z e d in that a fluid pressure is maintained. nside the new¬ ly-moulded pipe (20) , said pressure not being less than the fluid pressure at or in the vicinity of the bottom of the trench, possibly with the addition of the pressure from the thrown-back bed material, e.g. by the first moulded end of the pipe being held in connection with a well, wherein a liquid surface level corresponding to the desired pressure is main¬ tained. 10. Machine in accordance with claims 4-8, c h a r¬ a c t e r i z e d by elements for the mutual side- ways displacement and/or turning of the common sup¬ porting element (29) and the main chassis (3) . 11. Machine in accordance with claims 4-8 or 10, c h a r a c t e r i z e d by elements for the auto- matic control of the machine's level, slope and/or direction of forward movement, dependent on level-, slope- and/or course-sensors suitably arranged for the purpose, said control elements being arranged to influence the elements for the raising and the low- ering of the supporting legs (4,5) and the elements according to claim 10. OMH WIPO

Inventors: SKROEDER CARL PETER, SKROEDER, CARL, PETER
Applicants: SKROEDER CARL PETER, SKROEDER, CARL, PETER
Application year: 1982
Main classification: F16L1
IPC codes: E02F5, E02F9