The invention relates to a pipe system for use in a body of water, comprising at least one conveyor pipe and at least one floating body for supporting the conveyor pipe so that it floats on the body of water.

A pipe system of this type is generally known and is used, for example, for removal of the dredged material dredged up by a floating dredging installation. In the case of non-floating dredging installations as well, such as are disclosed in NL-A- 8104791, a conveyor pipe has to be used to remove dredged material. In the case of an installation of this type, a sinkable pipe is used, which runs over the bed of the body of water. A non-floating pipe of this type is installed by first constructing said pipe as a floating pipe and then sinking it at the place of intended use. However, when sinking a pipe all sorts of difficulties can arise which are related to the problem that the behaviour of the pipe during sinking is not easy to control. The consequence of this is that the pipe descends in an irregular fashion, as a result of which kinking can occur such that the inclusion of air takes place and ultimately the pipe becomes unusable.

The aim of the invention is to provide a pipe of the abovementioned type which displays better characteristics in this regard, which aim is achieved in that a jacket enclosing the pipe is provided, the interior space of which jacket is in connection with the outside, at least one floating body of variable volume also being located in said interior space of the jacket.

The location and the volume of the floating body can be chosen in such a way that the pipe can be controlled easily over its entire length during sinking and refloating. If the floating body is compartmente , it is even possible accurately to influence the behaviour- of the pipe over its length.

Preferably, each floating body comprises a flexible hose¬ like body which is provided with a connection for compressed air.

The jacket can be a plastic pipe. As a plastic pipe of this type can display creep, even, for example, under the influence of its own weight, pretensioning cables are provided inside the plastic pipe, which pretensioning cables are in contact with the two ends of the pipe. As a consequence of the compressive stress generated in the plastic pipe, deformation as a result of creep is restricted.

The jacket has interior water-permeable spacers distributed evenly over its length, which spacers are provided with cut- outs for the conveyor pipe and for each floating body. The pipe and floating bodies are held in place by the spacers; on the other side there are cut-outs for feeding through lines, for instance for power, control, signalling and the like (lifeline or "umbilical"). The water-permeable spacers also leave sufficient space free for the floating bodies to expand and thus to dispel the water from the jacket, as a result of which the pipe system can float up.

Furthermore, power and control lines can be accommodated in the jacket for a dredging installation which can be operated by remote control. A dredging installation of this type can be the installation disclosed in N -A-8104791, which in the operating condition is located on the bed of a body of water.

The invention will be explained in more detail below with reference to illustrative embodiments shown in the figures. Figure 1 shows a perspective, partially exposed, view of part of the pipe system according to the invention.

Figure 2 shows a cross-section of the pipe section according to Figure 1.

Figure 3 shows a side view of a dredging system with the pipe system as used in practice.

The pipe system shown in Figure 1 comprises a jacket 1, in which a conveyor pipe 2, hydraulic/pneumatic and/or power lines 3 and communication lines 4 are accommodated. Three floating bodies 5 are also accommodated in the jacket 1. The pipe 2 and lines 3 and 4 and the floating bodies 5 are all fixed by means of spacers 6, which are arranged evenly distributed over the length of the jacket. To this end, the spacers 6 have openings which are matched to the outside

diameter of the pipe 2 and lines 3 and 4. The floating bodies 5 are also accommodated in the holes, the size of which is matched to the maximum diameter of said floating bodies 5, that is to say a diameter in the inflated form. The spacers 6 are connected to one another by three cables 7. Said cables run through holes in the spacers 6 as close as possible to the periphery. On either side of a partition, each cable 7 is provided with clamps 8, in such a way that the spacers are held in a position transverse to the longitudinal axis of the jacket 1. Incidentally, the spacers are not fixed to said jacket at their circumference. This means that an assembly made up of spacers 6, cables 7, pipe 2, lines 3 and 4 and floating bodies 5 can be pulled into or out of the jacket pipe. As an alternative, the jacket, optionally in sections which can be coupled to one another, can be slid over said assembly.

The dredging system shown in Figure 3 comprises a dredging installation which is designated in its entirety by 11 and is connected via a pipe system 16 according to the invention, for example via a universal joint, to a sunken coupling pontoon 22. Furthermore, the coupling pontoon is connected to a so-called suspension pipe 17. Said suspension pipe 17 is connected via a hinge, for example ball hinge 21, to the "fixed" pipe section 18.

The flexible pipe system 16 according to the invention is suitable, together with the dredging installation 11, for repeated sinking and refloating. This is always effected in accordance with a sector arc, transverse to the pipe 16, when the dredging installation has to be moved over relatively small distances to a new extraction point, or needs to be checked. In connection with movement over relatively large distances, for example to a line 18 located further away, the coupling pontoon 22 must be floated up and sunk again.

Pipe section 18 is removed only when the dredging installation has to be moved to another extraction area. The flexible pipe system 16 according to the invention is now able outstandingly to follow the contour of the well which forms during operation of the dredging installation 11. During this operation said pipe system moves so that it is suspended

in a curve in the well. By virtue of the hauling cables located in the pipe system 16, the tensile force which then arises can be taken up well.

The suspension pipe 17 and the pipe section 18 can, however, have a more rigid jacket since these are subjected to virtually no bending.

In the illustrative embodiment in Figure 3 it can be seen that each jacket pipe 1 carries end partitions 9, 10 at its ends. The cables 7, in their turn, are again connected to said end partitions, as a result of which the correct position of the spacers 6 in the jacket pipe 1 is ensured.

At the location of end partition 9, the jacket pipe 1 is provided with opening, via which the water is able to penetrate inside the jacket pipe 1. Depending on the volume taken up by the floating bodies 5, the pipe system can consequently float up or sink. If, as shown in Figure 1, the floating bodies are pumped up completely, the pipe system will float up. However, as soon as the floating bodies are allowed to empty, end partition 9 being located higher than end partition 10 when the pipe system is in the sunken position, said floating bodies are compressed under the influence of the pressure of the water present in the jacket pipe 1. The pipe system will then slowly sink.

The spacers 6 are likewise provided with supplementary holes to ensure that the water can flow freely backwards and forwards through the jacket pipe 1.

In the use example shown in Figure 3, the pipe system according to the invention is used with a dredging installation 11 operating underwater. Said dredging installation has a housing 12, to which the pipe section according to the invention is fixed by a universal joint 13. A suction pipe 14, which has openings 15, protrudes from the bottom of the housing. By means of a pump located in the housing 12, the dredged material can be sucked up through the openings 15 and then be removed to the shore through the pressure line 2 present in the pipe system.

Onshore, said pipe system is connected to a receiving installation, where the dredged material can be further

processed and discharged.

In the operating condition, sections 16, 17 and 18 of the jacket 1 are all sunken. When the dredging installation 11 is moved, said sections have to be floated up, in which case section 16 of jacket 1 is likewise floated up, as is shown by broken lines.

When the dredging installation is removed from the treated location, sections 16 and 17 are floated up and the receiving installation is hoisted up. The hinges 19, 20 and 21 are provided in order to make these movements possible.