GB2069094A

GB2069094A - Burying pipelines in the sea bed

Info

Publication number: GB2069094A
Application number: GB8104044A
Authority: GB
Original assignee: Coflexip SA
Current assignee: Technip France SAS
Priority date: 1980-02-11
Filing date: 1981-02-10
Publication date: 1981-08-19
Also published as: NL188052C; IT8119633A0; NL8100628A; FR2475681B1; NO158588C; ES499991A0; NO158588B; FR2475681A1; NO810455L; ES8201712A1; GB2069094B; NL188052B; IT1169044B

Abstract

An apparatus for burying cables or flexible tubular pipelines 9 in the sea bed, comprises on a trolley or carriage 1 movable on the sea bed and connected to the surface vessel from which the said trolley or carriage 1 is controlled and from which the pipe 9 to be laid is submerged, a front part incorporating a rotary cutting disk 4 able to rotate about a horizontal shaft, whilst being driven by motor means 5 and which is peripherally provided with cutting members 7, and a rear part in the form of a chute 8 which receives from the top the pipe 9 to be laid and guides it to the bottom of the trench dug out by the front part during the controlled forward travel of the carriage 1, the rotary cutting disk 4 and the chute 8 for receiving and guiding the pipe 9 to be laid being integral with a chassis 13 which is vertically movable with respect to the carriage 1, wherein the receiving and guidance chute 8 is removed so as to pivot with respect to the chassis 13 moving around a horizontal shaft under the action of a jack 18 mounted between the movable chassis 13 and the chute 8 and wherein the chute 8 has an access door 11, particularly a hydraulically controlled access door, articulated to the top of the chute 8. <IMAGE>

Description

SPECIFICATION Method for burying cables or flexible tubular pipelines in the sea bed The present invention relates to an apparatus for burying flexible or tubular piplines in the soil forming the bottom of a volume of water and in particular the sea bed. Although the invention can also apply to other volumes of water, such as rivers or lakes, for the clarity of description reference will be made hereinafter to the sea bed.

In the same way, the production to be buried will be given the generic name pipe, without this term being in any way limitative.

Numerous apparatuses are known for submerging the tubular pipe, particularly a flexible pipe from the surface and burying it in the sea bed, i.e. placing it in a trench dug out for this purpose from the sea bed.

A first apparatus category, called jetting apparatus is known where a trench is made by means of a carriage or trolley moving along the sea bed and connected to the surface vessel from which said trolley is controlled and from which the pipe to be laid is submerged. The trolley is equipped with arms having nozzles for the injection of pressurized fluid, particularly water, making it possible to dig out the soil and remove the spoil to the sides of the carriage.

Such apparatuses are not satisfactory, particularly when the sea bed is hard and is made, for example, of rock. Moreover, it is not possible or at least very difficult with such apparatuses to check the trench depth and ensure that it is covered after laying the pipe.

A second apparatus category, called cutting apparatus is known comprising on a carriage or trolley which moves along the sea bed a front part shaped so as to form a mechanical cutting member and a rear part in the form of a chute for receiving from the top the pipe to be laid. In addition, said rear part has in general means for internally guiding the pipe to be laid when the latter is flexible until it is pressed against the bottom of the trench dug out by the front part during the controlled forward travel of the trolley.

Furthermore, apparatuses of this type are known in which the mechanical cutting member is constituted by the share part of a raisable, articulated plough. Further apparatuses of this type are known in which the mechanical cutting member is in the form of a cutter disk able to rotate about a shaft, whilst being driven by appropriate motor means and whilst peripherally provided with cutting members.

However, such apparatuses are not always satisfactory for certain types of submarine soils, particularly hard soils. In addition, they do not permit a precise control of the depth of the trench to be dug out, as a function of the nature of the soil and as a function of the laying requirements.

The present invention proposes an improved apparatus of the type in which the mechanical cutting member is a rotary cutting disk which is able to bury with relatively low energy costs, flexible tubular pipes and similar products, no matter what the nature of the submarine soil and in water depths of several dozen and even several hundred metres.

The apparatus according to the invention also makes it possible to simultaneously lay and bury a plurality of pipes from the same laying ship, saidpipes being layable on the sea bed at randomly regulatable depths, which can reach 1.5 metres.

The present invention relates to an apparatus for burying cables or flexible tubular piplines in the sea bed, comprising on a trolley or carriage movable on the sea bed and connected to the surface vessel from which the said trolley or carriage is controlled and from which the pipe to be laid is submerged, a front part incorporating a rotary cutting disk able to rotate about a horizontal shaft, whilst being driven by motor means and which is peripherally provided with cutting members, and a rear part in the form of a chute which receives from the top the pipe to be laid and guides it to the bottom of the trench dug out by the front part during the controlled forward travel of the carriage, the rotary cutting disk and the chute for receiving and guiding the pipe to be laid being integral with a chassis which is vertically movable with respect to the carriage, wherein the receiving and guidance chute is mounted so as to pivot with respect to the chassis moving around a horizontal shaft under the action of a jack mounted between the movable chassis and the chute and wherein the chute has an access door, particularly a hydraulically controlled access door, articulated to the top of the chute.

According to a preferred embodiment, the movable chassis is connected to the trolley by arms forming an articulated parallelogram structure the movable chasis being operated by jacks, particularly substantially vertical jacks integral with the trolley.

According to the invention, the receiving and guidance chute can be raised with respect to the movable chassis by pivoting about a horizontal shaft, particularly the assembly shaft of the chute on the movable chassis, or particularly under the action of the jack positioned obliquely between the movable chassis and the chute. After raising the movable chassis making it possible to completely clear the trench, particularly for passing over an obstacle, the pivoting of the chute facilitates the introduction of a pipe to be laid into said receiving and guidance chute.

According to the invention, the chute for introducing, guiding and laying the pipe carries a preferably hydraulically controlled access door articulated to the top of the said chute and which gives access to the pipe when the need arises.

This access operation takes place after raising by pivoting the chute in the manner described hereinfore.

The rotary cutting disk can be rotated by any appropriate motor means, particularly by one or preferably more variable speed electrical or hydraulic motors. On the disk periphery, there are dismantlable segments to which are fixed cutting tools. During the rotation of the disk, these tools makes it possible to break up hard rocks, the spoil being preferably discharged laterally with respect to the trolley by means of tubes fitted laterally to either side of the trolley level with the disk and in which there is a pressurized fluid and in particular water flow.

The apparatus according to the invention naturally also comprises means in the form of sensors and indicators making it possible to control the direction of the trolley, its forward movement and the cutting depth. This information is transmitted to the surface vessel by an umbilical connecting cord, which also supplies from the surface to the trolley the fluids necessary for driving the trolley, the cutting disk and the jacks.

To this end, the surface vessel advantageously has a hydraulic or electric power plant.

The apparatus according to the invention has proved particularly suitable for laying cables or flexible tubular pipelines such as, for example, flexible hydrocarbon-conveying pipelines, particularly those marketed in considerable lengths by the Applicant Company, control lines, power transmission cables and telecommunications cables.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and with reference to the attached drawings, wherein show: Fig. 1 in longitudinal elevation the apparatus according to the invention, the guidance chute and the rotary cutting member being diagrammatically shown in different operating positions.

Fig. 2 an end elevation of the apparatus according to the invention.

Fig. 3 a plan view.

The apparatus according to the invention essentially comprises a carriage or trolley 1 constituted by a rigid support frame 2 supporting two caterpillars 3, preferably operated by variable speed electric or hydraulic motors, whilst being of the type usable on all types of ground.

The trolley 1 is linked with the not shown surface vessel by means of at least one umbilical cord, such as for example the hydroelectric type produced in large quantities by the Applicant Company, able to supply from the surface all the hydraulic and/or electric control fluids required for operating the device and also conveying from the apparatus to the surface the data relating to the operation control.

Instead of having caterpillars, the trolley 1 can also be towed from the surface vessel, comprising for example a metal frame supported on two shaped, hollow, lateral blocks, more particularly having a circular cross-section and which can be wholly or partiy filled beforehand with ballasting water.

The apparatus according to the invention comprises a rotary cutting disk 4, which can best be seen in Fig. 1. This rotary disk is mounted on a reduction plate and rotated by preferably hydraulic or electric motors 5. In the represented embodiment, there are two such motors, although this number is not limitative, and said motors correspond to an installed power of approximately 400 hp. The rotary disk has an external diameter of 3400 mm, a width of 600 mm for a disk rotation speed between approximately 10 and approximately 30 r.p.m.

As can best be seen in Fig. 1, rotary disk 4 has dismantlable segments 6 on its periphery, to which are fixed cutting tools 7.

The rear part 1 of the apparatus is constituted by a mechanically welded chute 8 receiving from above the product to be laid, which is unwound from the surface vessel and said chute guides it to the bottom of trench 10 dug out by the apparatus.

Fig. 1 illustrates the arrangement within the chute 8 of the product, particularly the flexible tubular pipe 9 to be buried.

In the rear part of chute 8 there is a door 11 which is laterally articulated above the chute in order to give access to pipe 9 in the chute. Door 11 is manipulated by means of hydraulic control means, particularly jacks 1 2.

In the apparatus according to the invention, the rotary cutting tool 4 and the receiving and guidance chute 8 for the product to be laid are integrally mounted on a chassis 13, which is able to move vertically with respect to the trolley frame 2.

The movable chassis 13 is connected to the trolley frame 2 by arms 14 forming an articulated parallelogram structure. The movable chassis 1 3 is vertically displaced with respect to the trolley by jacks 15, whose lower part is articulated to frame 2 at 16 and whose upper part is articulated to movable chassis 13 at 1 7.

The broken lines in Fig. 1 show the position of the rotary cutting disk 4 and the guidance chute 8 after vertical displacement in order to obtain a greater trench depth.

In an embodiment of the invention with the disk dimensions referred to hereinbefore, it is possible to regulate at random the depth of the trench to values which can reach 1 500 nm.

Fig. 1 also diagrammatically shows the cutting disk and guidance chute in the raised position.

This position is obtained after vertically raising the movable chassis 1 3 by rocking the guidance chute around its horizontal assembly shaft on the movable chassis by means of a hydraulic jack 1 8 connected to the chute at 19. This raised position makes it possible to completely clear the trench for overcoming obstacles or for laying a pipe, in which case the lateral door 11 is opened beforehand.

The spoil produced during the forward movement of the apparatus by the rotation of cutting disk 4 is advantageously removed by means of lateral tubes 20. These tubes are supplied by not shown pumps making it possible to bring about an upward movement of pressurized fluid, particularly water, which carries away the spoil produced being discharged to the sides of the dug trench.

The apparatus according to the invention also comprises control and checking means in the form of sensors, indicators and/or a television circuit making it possible to control the direction, the advance of the trolley and the cutting depth.

Although the invention has been described hereinbefore with respect to particular embodiments, it is obviously not limited thereto and numerous variants are possible without passing beyond the scope of the invention.

Claims

1. An apparatus for burying cables or flexible tubular pipelines in the sea bed, comprising on a trolley or carriage movable on the sea bed and connected to the surface vessel from which the said trolley or carriage is controlled and from which the pipe to be laid is submerged, a front part incorporating a rotary cutting disk able to rotate about a horizontal shaft, whilst being driven by motor means and which is peripherally provided with cutting members, and a rear part in the form of a chute which receives from the top the pipe to be laid and guides it to the bottom of the trench dug out by the front part during the controlled forward travel of the carriage, the rotary cutting disk and the chute for receiving and guiding the pipe to be laid being integral with a chassis which is vertically movable with respect to the carriage, wherein the receiving and guidance chute is removed so as to pivot with respect to the chassis moving around a horizontal shaft under the action of a jack mounted between the movable chassis and the chute and wherein the chute has an access door, particularly a hydraulically controlled access door, articulated to the top of the chute.

2. An apparatus according to claim 1, wherein the movable chassis is connected to the trolley by arms forming an articulated parallelogram structure, the manipulation of the movable chassis with respect to the trolley being effected by jacks fitted between the carriage and the movable trolley.

3. An apparatus according to either of the previous claims, wherein it comprises lateral tubes in which there is a pressurized fluid, particularly water flow for removing spoil.

4. An apparatus for burying cables or flexible tubular pipelines in the sea bed, substantially as described hereinbefore with reference to the accompanying drawings.