TECHNICAL FIELD

The present invention relates to a device for burying a conduit in the bed of a body of water.

The buried conduit serves to at least partly house a continuous elongated member, such as a pipeline, cable, umbilical, or bundle of pipelines and/or cables, at a landing dock or in relatively shallow water.

BACKGROUND ART

Continuous elongated members of the above sort are normally laid on the bed of a body of water to form underwater gas or power lines, which must be protected close to landing docks or in shallow water. In shallow water, it is therefore common practice to bury such members in the bed of the body of water.

For protection in shallow water, continuous elongated members are normally buried directly in a trench dug into the bed of the body of water . Known techniques of doing this are known as pre-trenching and post-trenching . Pre- trenching consists in digging a trench; laying the continuous elongated member inside the trench; and backfilling the trench to bury the continuous elongated member. Post -trenching consists in laying the continuous elongated member on the bed of the body of water; digging a trench in the bed of the body of water underneath the continuous elongated member, so the latter sinks into the trench; and backfilling the trench to bury the continuous elongated member. Since the trench tends to eventually fill up on its own (natural backfilling) , the backfilling and burying steps may be omitted.

Drawbacks common to both the above techniques of burying continuous elongated members are the enormous amount of energy required to excavate large masses of the bed of the body of water, and slow trench digging speed.

Pre-trenching has the drawback of requiring a widely flared trench, to prevent it from backfilling naturally, by the lateral faces of the trench caving in, before the continuous elongated member is laid. In fact, the time lapse between digging the trench and laying the continuous elongated member may be considerable.

Post-trenching poses a similar problem, though to a lesser degree, by having less flared trench walls, and by having to prevent the trench from backfilling before the member reaches the required depth. The length of the open trench may extend to hundreds of metres .

Moreover, both the above techniques call for two separates passes along the burial route : one pass to lay the member, and one to dig the trench. The above drawbacks encountered in burying continuous elongated members also apply to burying conduits .

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a device for burying a conduit in the bed of a body of water, designed to eliminate the drawbacks of the known art .

According to the present invention, there is provided a device for burying a conduit in the bed of a body of water, the device comprising a digging module for digging a trench in the bed of the body of water; a manipulating module for feeding conduit sections into the trench; and a push module for joining the conduit sections inside the trench and simultaneously moving the device in a travelling direction.

In the present invention, the trench is dug and the conduit formed in one pass along the set route in the bed of the body of water. Moreover, the movement used to assemble the conduit sections also provides thrust to move the whole device forward.

Preferably, the digging module, the push module and the manipulating module are arranged successively in the opposite direction to the travelling direction.

In a preferred embodiment of the present invention, the digging module is designed to break up and remove a mass of the bed of the body of water having a given cross section substantially the same size as the cross section of the entrenched part of the push module and manipulating module.

This ^" way, the cross section of the trench can be minimized.

In a preferred embodiment of the present invention, the manipulating module comprises a manipulator designed to grip a conduit section and align the conduit section with a given reference.

This enables the conduit sections to be joined to one another .

In a preferred embodiment of the present invention, the manipulating module comprises a first frame, in turn comprising two first lateral walls for supporting the side faces of the trench.

This makes it possible to dig a trench with substantially vertical side faces, and define a space in which to feed and assemble the conduit sections.

Preferably, the lateral walls of the manipulating module serve to support the manipulator.

In a preferred embodiment of the present invention, the push module comprises a second frame; and a pusher, which is fitted to the second frame and designed to engage a conduit section and push the conduit section, in the opposite direction to the travelling direction, against a member outside the device, so as to fit the conduit section tightly to the outside member and move the device in the travelling direction.

This way, the conduit section can be fitted tightly and the device moved using only one pusher.

Preferably, the longitudinal tilt of the pusher is selectively adjustable, preferably by a first actuator connected to the second frame and the pusher.

This enables the pusher to engage the conduit section when the two are misaligned.

Preferably, the second frame comprises two second lateral walls for supporting the side faces of the trench .

Preferably, the manipulating module and push module are connected rigidly to each other.

In a preferred embodiment of the present invention, the digging module and push module are articulated about a steering axis.

This enables the device to be steered horizontally.

Preferably, the device comprises at least one second actuator for controlling the position of the digging module, with respect to the push module, about the steering axis.

This enables control of the steering angle.

In a preferred embodiment of the present invention, the digging module is connected to the push module in selectively adjustable manner in a substantially vertical direction and by means of at least one third actuator .

This enables adjustment of the depth and longitudinal tilt of the device.

In a preferred embodiment of the present invention, the device comprises movable lateral walls located on opposite sides and which can be operated selectively to adjust the pressure of each against the side face of the trench.

This enables adjustment of the lateral tilt of the device .

In another preferred embodiment of the present invention, the device comprises a stabilizer designed to rest adjustably on the bed of the body of water; the stabilizer preferably comprising a frame connected rigidly to the push module or manipulating module, and two supports located on opposite sides of the push module and connected to the frame in selectively movable manner independently of each other.

The stabilizer provides for both supporting the push module and manipulating module, and controlling the lateral tilt of the device.

In a preferred embodiment of the present invention, the device comprises a backfill module preferably comprising a shovel, which extends on opposite sides of T/IB2014/059139

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the trench and comprises two blades sloping with respect to the travelling direction. In a variation of the present invention, the backfill module comprises screws or high-density fluid pumps for performing the backfill step right after the digging step.

This way, the device provides for backfilling the trench faster over the conduit.

Another object of the present invention is to provide a method of burying a conduit in the bed of a body of water.

According to the present invention, there is provided a method of burying a conduit in the bed of a body of water, the method comprising the steps of digging a trench in the bed of the body of water by means of a device; feeding conduit sections into the trench; joining the conduit sections inside the trench and the device; and moving the device in a travelling direction.

This way, the trench is dug and the conduit assembled and laid in one pass.

Preferably, the method provides for pushing and joining the conduit section by means of a pusher, and using the pusher to move the device.

The thrust exerted by the pusher exerts pressure on the conduit section to fit the conduit sections tightly one inside the other and move the device. This configuration, in fact, has a synergic effect.

Preferably, each conduit section comprises a first and second end designed to form a preferably tight spigot and socket joint.

This design simplifies assembly of the conduit.

In a preferred embodiment of the present invention, the device is articulated about a steering axis; the method comprising the step of acquiring a signal related to the steering angle.

This way, steering and the path of the device can be monitored.

In a preferred embodiment of the present invention, the device is articulated so that one portion of the device is located at a different depth from another portion of the device; the method comprising acquiring a signal related to the variation in the depth of the two portions of the device.

This makes it possible to control variations in entrenchment of the device .

Preferably, the method comprises acquiring a signal related to the depth of the device, so as to precisely indicate entrenchment of the device and trench depth.

Preferably, the method comprises acquiring a signal related to the longitudinal tilt of the device.

This makes it possible to monitor travel of the device along a given route . Preferably, the method comprises acquiring a signal related to the lateral tilt of the device.

This signal indicates any lateral tilting of the device, so appropriate corrective action can be taken.

Preferably, the method comprises acquiring a signal related to the longitudinal tilt of the pusher.

This way, the pusher can be adjusted for easy connection to the conduit section.

Preferably, the method comprises acquiring a signal related to the position of the conduit section with respect to a reference point.

This signal simplifies connection between the conduit section and the previously laid conduit portion, on one side, and between the pusher and the conduit section, on the other.

The invention may be used to advantage as an alternative to microtunneling for laying guide pipes, and directional drilling. The invention also permits laying of pipelines of infinite length, by virtue of the pipe sections being added to the leading end, as opposed to the trailing end, of the laid pipeline.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of non- limiting embodiments of the present invention will be described by way of example with reference to the attached drawings, in which :

Figures 1 to 6 show schematic, partly sectioned side views, with parts removed for clarity, of a device for burying a conduit in the bed of a body of water, and at various stages in assembling a conduit section;

Figure 7 shows a partly sectioned view in perspective, with parts removed for clarity, of a detail of the conduit;

Figure 8 shows a partly sectioned elevation, with parts removed for clarity, of the digging module of the device according to the present invention;

Figure 9 shows a section, with parts removed for clarity, of the digging module along line IX- IX in Figure 8 ;

Figure 10 shows a partly sectioned side view, with parts removed for clarity, of the Figure 8 digging module ;

Figure 11 shows a partly sectioned side view, with parts removed for clarity, of a variation of the device according to the present invention;

Figure 12 shows a partly sectioned plan view, with parts removed for clarity, of the push module of the device according to the present invention;

Figure 13 shows a partly sectioned side view, with parts removed for clarity, of the Figure 12 push module;

Figure 14 shows a partly sectioned elevation, with parts removed for clarity, of the manipulating module of the device according to the present invention; Figure 15 shows an elevation, with parts removed for clarity, of the stabilizing system of the device according to the present invention;

Figure 16 shows a side view, with parts removed for clarity, of the Figure 15 stabilizing system;

Figure 17 shows a plan view, with parts removed for clarity, of a trench backfill module;

Figure 18 shows a partly sectioned plan view, with parts removed for clarity, of a variation of the device according to the present invention;

Figure 19 shows a schematic, with parts removed for clarity, of the control system of the device according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 1 indicates as a whole a device for burying a conduit 2 in the bed 3 of a body of water 4.

As shown more clearly in Figure 7, conduit 2 comprises a plurality of joined sections 5, which may be made of concrete or metal, and each of which has two opposite ends 6 and 7 designed to form tight spigot and socket joints with the other sections 5.

As shown in Figure 1, device 1 comprises a digging module ^' 8 for digging a trench 9 in bed 3 of body of water 4; a manipulating module 10 for feeding conduit sections 5 (Figure 2) into trench 9; and a push module 11 for joining conduit sections 5 to one another inside trench 9 and simultaneously moving device 1 in a travelling direction Dl .

Digging module 8, push module 11 and manipulating module 10 of device 1 are arranged successively in the opposite direction to travelling direction Dl . Digging module 8 is designed to break up and remove a mass of bed 3 of body of water 4 having a given cross section substantially the same size as the cross section of the entrenched part of push module 11 and manipulating module 10.

As shown in Figure 2, manipulating module 10 comprises a manipulator 12 for gripping a conduit section 5 and aligning it with a given reference point.

As shown in Figure 3, conduit section 5 is aligned with the part of conduit 2 already laid inside trench 9.

Push module 11 comprises a pusher 13, which is adjustable to substantially align with the conduit section 5 supported by manipulator 12.

In Figure 4, pusher 13 is extended, engages end 6 of conduit section 5, and pushes conduit section 5 to fit end 7 of conduit section 5 to end 6 of the laid portion of conduit 2.

Further extension of pusher 13 moves the whole of device 1 in travelling direction Dl, as shown in Figure 5. On reaching its maximum extension, pusher 13 is withdrawn, and manipulator 12 is raised, as shown in Figure 6. At this point, device 1 is ready to receive another conduit section 5, and the cycle of assembling conduit 2 and moving device 1 forward is repeated.

As device 1 moves forward, digging module 8 breaks up, excavates and removes a mass of bed 3 and deposits it on opposite sides of trench 9.

With reference to Figure 9, digging module 8 is hinged to push module 11. More specifically, digging module 8 (Figure 10) is hinged to push module 11 about a substantially vertical axis Al . The position of digging module 8 relative to push module 11 is preferably controlled by an actuator 14, to direct device 1 horizontally.

In the Figure 11 variation, digging module 8 is connected to push module 11 in selectively adjustable manner in a substantially vertical direction and by means of at least one further actuator 15.

With reference to Figures 8 to 10, digging module 8 comprises a frame 16; and a powered-screw assembly 17 for breaking up, excavating and removing the mass of bed 3 of body of water 4. As shown in Figure 8 , trench 9 has a substantially rectangular cross section, i.e. has two opposite, parallel, substantially vertical side faces 18.

With reference to Figures 12 and 13, push module 11 comprises a frame 19 for supporting pusher 13 and the side faces 18 of trench 9. In the example shown, frame 19 is parallelepiped-shaped, and is open at the bottom and at least partly at the rear to allow pusher 13 to extend outwards of frame 19. More specifically, frame 19 has two opposite, parallel lateral walls 20 for supporting side faces 18 of trench 9.

With reference to Figure 13, pusher 13 is substantially defined by a linear actuator, and is adjustable selectively with respect to frame 19. More specifically, pusher 13 is hinged at one end to frame 19, and is also connected to frame 19 by a further actuator 21 for adjusting the longitudinal tilt of pusher 13. This way of assembling pusher 13 allows correction of any misalignment between pusher 13 and the sections 5 supported by manipulator 12 (Figure 3) .

With reference to Figure 14, manipulating module 10 comprises a frame 22, in turn substantially comprising two lateral walls 23, the outer faces of which support side faces 18 (Figure 8) of trench 9, and the inner faces of which support manipulator 12. In a preferred embodiment, push module 11 and manipulating module 10 are integral with each other. So, each lateral wall 23 is integral with a respective lateral wall 20. Walls 20 and 23 are preferably defined by a single panel.

Unlike frame 19, frame 22 is also open at the top to allow insertion of conduit sections 5 between lateral walls 23. Manipulating module 10, in fact, may be connected to a storage module (not shown) containing a given number of, e.g. three, sections 5.

Manipulator 12 preferably comprises two holders 24 designed to house a conduit section 5, and to move between a lowered position and a raised position. Each holder 24 is fitted slidably to a respective wall 23, and is connected to a respective actuator 25.

With reference to Figures 15 and 16, device 1 comprises a stabilizer 26 designed to rest on bed 3 of body of water 4, preferably on adjustable supports 27.

More specifically, stabilizer 26 comprises a frame 28 connected to the top of manipulating module 10 and push module 11; and two supports 27 located on opposite sides of push module 11 and manipulating module 10, and hinged to frame 28 by an articulated parallelogram system. The distance between each support 27 and frame 28 is adjustable independently of the other. In the example shown, each support 27 is operated by a pair of actuators 29.

In a variation not shown, each support 27 is operated by one actuator located directly between support 27 and frame 28.

With reference to Figure 17, device 1 comprises a further module - in the example shown, a backfill module 30 downstream from manipulating module 10 (Figure 1) .

Backfill module 30 is towed by the rest of device - 1, and comprises a shovel 31 designed to rest on bed 3 of body of water 4 and intercept the mass of bed 3 removed by digging module 8; and tow bars 32.

Digging module 8 (Figure 8) forms two continuous, elongated piles 33 of excavated bed 3 on opposite sides of trench 9.

Shovel 31 is designed to intercept both piles 33 and to guide the mass in piles 33 into trench 9 as device 1 moves forward.

Shovel 31 preferably has two walls 34 sloping with respect to each other and each designed to intercept a respective pile 33.

As shown in Figure 18, in a variation of the present invention, lateral walls 23 comprise movable walls 35 located on opposite sides, and which can be operated selectively to adjust the pressure of each against side face 18 of trench 9 and control the lateral tilt of device 1. Each movable wall 35 is operated by a respective actuator 36.

With reference to Figure 19, device 1 comprises a power unit 37; a control unit 38; and a control console 39 for manually operating device 1.

Power unit 37 powers actuators 14, 15, 21, 25, 29 and 36, pusher 13, and screw assembly 17, all of which are preferably designed to generate and transmit respective operating-state signals to control unit 38, which in turn controls power unit 37. The device is thus closed-cycle-controlled. Power unit 37 is preferably hydraulic, but may be ^' electric or hydraulic and electric combined.

Device 1 can be controlled manually from console 39, or automatically on the basis of assigned and detected parameters, or semi-automatically .

In the example shown, device 1 comprises a steering sensor 40, a depth-change sensor 41, a depth sensor 42, a device longitudinal tilt sensor 43, a device lateral tilt sensor 44, a pusher longitudinal tilt sensor 45, and a conduit section position sensor 46.

In actual ^' use, as shown in Figures 1 to 6, device 1 digs a trench 9, partly engages trench 9, joins conduit sections 5 inside trench 9 and itself, and moves in travelling direction Dl .

As it extends, pusher 13 fits conduit section 5 to the section 5 already fitted to conduit 2, and generates thrust to move device 1 in direction Dl .

Conduit sections 5 are fed through an opening in the top of device 1 to manipulator 12 located inside device 1 and designed to grip and align each conduit section 5 with a given reference point. More specifically, conduit section 5 is aligned with the previously laid portion of conduit 2.

As it moves forward, device 1 supports side faces 18 of trench 9, and defines a space in which to manipulate and join conduit sections 5.

Once conduit section 5 is aligned by manipulator 12 with a given reference point, pusher 13 is activated to engage conduit section 5; to push conduit section 5, in the opposite direction to travelling direction Dl, against a member outside device 1, so as to fit conduit section 5 tightly to the outside member; and to move device 1 once the conduit section is fitted.

As regards control of device 1, the greater the number of operating parameters of device 1 that are monitored, the faster and more accurately the digging work and assembly of conduit 2 can be carried out.

Control unit 38 of device 1 is configured to acquire at least one, and preferably all, of the following signals :

- a signal related to the steering angle of the device, or rather between two articulated portions of the device;

- a signal related to the variation in the depth of the two articulated portions of the device;

- a signal related to the depth of the device;

- a signal related to the longitudinal tilt of the 4059139

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device;

- a signal related to the lateral tilt of the device ;

- a signal related to the longitudinal tilt of pusher 13; and

a signal related to the position of conduit section 5 with respect to a reference point.

Clearly, changes may be made to the embodiment described of the present invention without, however, departing from the protective scope claimed.