IE48918B1

IE48918B1 - Supports for pipes laid on undulating sea beds

Info

Publication number: IE48918B1
Application number: IE2316/79A
Authority: IE
Original assignee: Saipem Spa
Priority date: 1978-12-04
Filing date: 1979-12-03
Publication date: 1985-06-12
Also published as: GB2036917B; FR2443632A1; BE880366A; NZ192063A; DK471379A; IT1160284B; PT70534A; DK147952B; IT7830488A0; NL7908761A; IE792316L; NL178186B; NL178186C; JPS6352275B2; JPS5576279A; AR224382A1; DE2948779C2; DK147952C; AU528408B2; BR7907913A

Abstract

To form a support for a pipe (6), suspended over an undulating sea bed (2), there is used an apparatus having an inflatable cushion (28) releasably connected by a coupling (26) to a service module (9) which is lowered to the sea bed from a mother ship (7). The service module (9) has a container (11) filled with liquid cement. In use, the cushion (28) is positioned under the pipe (6), and is then inflated by liquid cement from the service module (9). The service module (9) is then released from the cushion (28), and the liquid cement in the cushion (28) sets so as to form a support for the pipe (6).

Description

This invention relates to an apparatus which enables a support for a pipe laid on an undulated sea bed, including a sea bed at a great depth, to be installed. The apparatus is particularly suitable for application in slight undulations in the sea bed, i.e. when the distance between the pipe to be supported and the sea bed is small.

The sea bed has not only crevasses, slopes and upward projections due to the presence of underwater rocks, but also slight undulations which give rise to depressions over which a pipe laid on the sea bed is suspended. In order to avoid the risk of undesirable bending of the pipe, it must be supported by suitable supports in these slight depressions.

In the present state of the art, there are various types of effective pipe supports, but because of their large overall size, none of these known types can be used when the distance between the suspended pipe and the sea bed in the depressions is very small, for example of the order of a few tens of centimetres. In this respect, the present state of the art offers methods which are only of little value and effectiveness, such as the stacking of sandbags under the pipe to be supported. Such a support, besides becoming weak as time passes because of the possible tears which can easily occur in the sandbags, cannot be used at great depths but only at a depth suitable for a diver, as a diver is required to stack the sandbags under the pipe to be supported.

It is desirable to obviate the aforesaid drawback and provide an apparatus which enables an effective lasting support for a pipe laid on an undulated sea bed to be formed simply and rapidly, even at great depths. This is attained according to the present invention by using as the support a suitable envelope which is disposed empty under the pipe at the point at which the pipe is to be supported, and is then distended by injecting liquid content into it.

According to the present invention, there is provided an apparatus for forming a support for a pipe laid on an undulating sea bed, the apparatus comprising a distensible cushion releasably connected to a service module adapted to be lowered to the sea bed from a mother ship, the service module comprising a container for containing liquid cement and means for injecting liquid cement from the container into the cushion to distend it, whereby the service module and cushion can be lowered to the sea bed and the cushion, while undistended, can be positioned below the pipe to be supported, whereby liquid cement can be injected into the cushion to distend the cushion so that the distend cushion, when the cement therein has set, supports the pipe, and whereby the service module can be released from the cushion and can be recovered by the toother ship.

More specifically, the apparatus for supporting a pipe laid on an undulated sea bed, according to the present invention, preferably comprises a support module or cushion constituted by a high strength synthetic fibre fabric envelope having a rectangular base and a saddle25 shaped top, the base being provided at one end with a lug for its hooking to the articulated arm of a submarine for conveying the still 8918 empty support module under the pipe at the point at which the pipe is to be supported, and at the other end with a hose provided with a non-return valve and a connector for connecting to an instant connection and release coupling by means of a projecting control lever, this coupling being fitted to the free end of the flexible outlet pipe of a container full of liquid cement which is supported in a recoverable service module consisting of a casing connected to the mother ship by a support cable, means being provided for pressure-injecting into the support module the liquid cement contained in the container of the recoverable service module.

The simplicity and economy of installation and the effectiveness of such a support is immediately apparent. In this respect, the support module is inserted empty and therefore in a limp state under the pipe to be supported, and can therefore be fitted however small the distance between the pipe and the sea bed. On injecting liquid cement, the module can be distended not only until it supports the pipe from below, but also to provide an upward force on the pipe so as to change its geometrical configuration at will. As the pipe is supported in the saddle in the top of the support module, it is ensured that the pipe can never accidentally escape from the support because of stresses due to the sea currents or internal tensile stress in the pipe. Moreover, the support is stable with time as the injected liquid cement hardens after a short time, and therefore any tearing of the fabric envelope forming the support module does not damage the support. The installation is economic due to the fact that the most costly unit, i.e. the service module, can be recovered once released from the support module, to be reused in subsequent operations. Finally, no depth limit is imposed on the apparatus as the few controls to be operated may consist of projecting levers which are easily accessible by a submarine, or may be operated remotely by a hydraulic control system mounted on the mother ship and connected to the service module by a hose fixed to the support cable.

According to an embodiment of the present invention, the means for pressure-injecting into the support module the liquid cement contained in the container of the recoverable service module consist of a rotating pump-hydraulic motor system operable by means of a projecting control lever, this system being mounted on the base of the container and connected to the flexible outletpipe from the container.

According to another embodiment of the invention, the pressureinjecting means consists of a bank of compressed air cylinders which are supported by the service module and are connected to the top of the container by a conduit provided with a pressure reducer and a shut-off valve with a projecting control lever.

According to a further embodiment of the invention, the pressureinjecting means consists of a compressed air system mounted on the mother ship and connected to the top of the container by a hose fixed to the support cable and passing through a shut-off valve with a projecting control lever. With this latter method, because of the inexhaustible quantity of compressed air available in practice, it is possible to fill a number of support modules simultaneously using the same service module.

Finally, according to a preferred embodiment of the invention, all of the aforesaid means for pressure-injecting into the support module the liquid cement contained in the container of the recoverable service module are simultaneously present on the service module of the apparatus.

The invention will now be described, by way of example, with reference to the accompanying drawing the single Figure of which is a perspective view of an apparatus according to the invention after the support module has been filled.

The Figure shows the sea surface 1 and the sea bed 2, the latter having undulations 3 and 4 between which is a depression 5 over which a laid pipe 6 is suspended. A mother ship 7 supports a recoverable service module 9 of the apparatus according to the invention, by means of a support cable 8. The module 9 consists of a casing 10 in which is supported a metal container 11 full of liquid cement. A bank of compressed air cylinders 12 supported by the casing 10 is connected to the top 13 of the container 11 by a conduit 14, provided with a shut-off valve 15 operable by a projecting control lever 16, and a pressure reducer* 17 on which are fitted a high pressure gauge 18 and a low pressure gauge 19. A hose 22 for compressed air from the mother ship 7 is also connected to the top 13 of the container 11 by a shut-off valve 20 operable by a projecting control lever 21, this hose being fixed to the support cable 8.

At the base of the container 11, there is mounted a rotating pump 23 operated by a hydraulic motor controlled by a projecting lever 24, this pump 23 being connected to a flexible outlet pipe 25 of optimum length for facilitating the operations of the submarine (as described below), and terminating in a coupling 26 which can be instantly connected and released by means of a projecting control lever 27.

The purpose of the coupling 26 is to releasably connect the recoverable service module 9 to a support module 28. The support module 28 is a cushion made of a high strength synthetic fibre fabric envelope having a rectangular base 29 and a saddle-shaped top 30, and provided at one end with a lug 31 for hooking it to the articulated arm of a submarine, and at the other end with a hose 32 fitted with a non-return valve 33 and a connector for connecting to the coupling 26.

The operation of the apparatus is as follows.

The service module 9, with the support module 28 coupled to it is lowered from the mother ship 7 by the support cable 8 onto the sea bed 2 in proximity to the pipe 6 to be supported. A submarine hooks its articulated arm to the lug 31 and positions the still empty and therefore limp support module 28 (represented by the dashed line 34) underneath the pipe at the precise point in which the pipe is to be supported. By using the articulated arm of the submarine, one of the levers 24, 16 or 21 is operated to operate one of the three systems provided for injecting the support module 28 with the liquid cement contained in the container 11. The support module 28 is filled with liquid cement until it accommodates the pipe 6 in its saddle top 30. The articulated arm of the submarine then operates the lever 27 so that the service module becomes separated from the support module and can be recovered by the mother ship.

Instead of being operated manually by the articulated arm of a submarine, the levers 24, 16 and 21 controlling the systems for injecting liquid cement into the support module and the lever 27 for releasing the service module from the support module can be operated automatically by remote control from the mother ship by using electro-hydraulic control elements of known type supplied from the ship by means of a further electric cable also fixed to the support cable.

Claims

1. An apparatus for forming a support for a pipe laid on an undulating sea bed, the apparatus comprising a distensible cushion releasably connected to a service module adapted to be lowered to the sea bed from a mother ship, the service module comprising a container for containing liquid cement and means for injecting liquid cement from the container into the cushion to distend it, whereby the service module and cushion can be lowered to the sea bed and the cushion, while undistended, can be positioned below the pipe to be supported, whereby liquid cement can be injected into the cushion to distend the cushion so that the distended cushion, when the cement therein has set, supports the pipe, and whereby the service module can be released from the cushion and can be recovered by the mother ship.

2. An apparatus as claimed in claim 1, wherein the means for injecting liquid cement from the container into the cushion comprises a pump and a motor for driving the pump.

3. An apparatus as claimed in claim 2, wherein the motor is operable by a control lever which in turn is operable by an articulated arm on a submarine.

4. An apparatus as claimed in claim 1, wherein the means for injecting liquid cement from the container into the cushion comprises one or more cylinders for compressed air, connected to the container via a pressure reducer and a valve.

5. An apparatus as claimed in claim 4, wherein the valve is operable by a control lever which in turn is operable by an articulated arm on a submarine.

6. An apparatus as claimed in claim 1, wherein the means for injecting liquid from the container into the cushion comprises a pressure hose connected to the container via a valve, the pressure hose being connected in use to a compressed air system onboard the mother ship.

7. An apparatus as claimed in claim 6, wherein the valve is operable by a control lever which in turn is operable by an articulated arm on a submarine.

8. An apparatus as claimed in claim 2 or 3 and as claimed in claim 4 or 5 and as claimed in claim 6 or 7, having each of said three means for injecting liquid cement from the container into the cushion.

9. An apparatus as claimed in any of claims 1 to 8, wherein the cushion is connected to the service module via a non-return valve and a releasable connector.

10. An apparatus as claimed in claim 9 wherein the connector is operable by a control lever which in turn is operable by an articulated arm on a submarine.

11. An apparatus as claimed in any of claims 1 to 10, wherein the cushion is made of synthetic fibric.

12. An apparatus as claimed in any of claims 1 to 11, wherein the cushion, when distended, has a saddle-shaped upper surface.

13. An apparatus as claimed in any of claims 1 to 12, wherein the cushion has a lug whereby it can be positioned below the pipe by an articulated arm on a submarine.

14. An apparatus as claimed in claim 1, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.