WO2015185951A1

WO2015185951A1 - System for the maintenance of an arbitrary distance of a buoyancy element in the process of laying pipelines

Info

Publication number: WO2015185951A1
Application number: PCT/HR2014/000020
Authority: WO
Inventors: Ivan KABLAR
Original assignee: Kablar Ivan
Priority date: 2014-06-06
Filing date: 2014-06-06
Publication date: 2015-12-10

Abstract

This invention refers to a system for maintaining an arbitrary distance of a buoyancy element (15) from a pipelay vessel in the process of underwater installation of classic pipeline, flexible pipeline or cables. The system consists of a main structure (1), which supports a receiving framework (7), a central rotational portion (2)(3)(4) that consists of two pulleys (2)(4) and a gear (3) on an axle (5), and a brake rod (14) and a brake plate (6) that are connected to a rack (13) linked to a gear (3). The moment acting through the link of the buoyancy element (15) via the link (10) on the pulley (4) and the connection with the brake rod (14), brake plate (6) and rack (13) creates a restrained state of the system on the pipeline. Forward movement of the pipelay vessel in the length of a newly welded section of pipeline (and/or shortening the link (9)) the link with the pipelay vessel (9) begins to tighten so that it creates moment that acts in the opposite direction in respect to moment that is created by the buoyancy element (15). With a further increase in tension force, and hence in moment, raising of the rack (13) and brake plate (6) occurs and finally, the assembly begins to move together with the pipelay vessel. At the moment when the pipelay vessel stops, the force in the link with the pipelay vessel (9) begins to yield and the moment obtained from the buoyancy element (15) prevails the moment obtained from the link with the pipelay vessel (9), and therewith friction at the connection brake plate (6)-pipe (18) increases, and the system once again enters a restrained state.

Description

SYSTEM FOR THE MAINTENANCE OF AN ARBITRARY DISTANCE OF A BUOYANCY ELEMENT IN THE PROCESS OF LAYING PIPELINES

The field pertaining to the invention

This invention refers to a device for underwater pipe line installation that enables a buoyancy element to maintain a constant distance from the pipelay vessel in the process of laying rigid and/or flexible pipes, cables, etc. in sea, river or lake bed areas. The subject of the invention is classified under laying or reclaiming pipes on or under water, between the surface and the bottom, and is specifically designated as class F16L 1/14.

Technical problem

Pipelines are usually constructed in the manner that sections of pipe of specific lengths are connected together on a pipelay vessel and inserted into a sea/lake/river. During the entire process of connecting new sections of pipe, the pipeline is held by a tensioner, which prevents the pipeline's "escape" into the sea/lake/river. After the completion of a connection cycle, the tensioner releases the pipeline in the amount of the length of a newly installed section of pipe, and the pipelay vessel moves in the direction of installation and begins a new connection cycle. During the installation of pipe, whether from a barge or a ship, and for the purpose of assuring the structural integrity of the pipe, in some cases a buoyancy element must be applied in order to decrease the specific weight of the immersed pipe. This invention enables the use of a system that maintains an arbitrary distance of the buoyancy element in respect to the pipelay vessel in the process of underwater pipeline installation. The use of the subject invention decreases the need for a larger number of buoyancy elements and/or eliminates the need to use a descending ramp (i.e. a "stinger"), whose installation onto or removal from the pipelay vessel results in a loss of a significant number of working hours.

Current state of the art

According to the current state of the art, the use of buoyancy elements is executed at the very end of the pipe connection process on a ship/barge immediately before the pipe is immersed into a sea/lake/river using the strapping binding method (or similar) on the pipeline that is being installed. As the installation of the pipeline progresses, the buoyancy element that is bound to the pipeline eventually reaches the bottom together with the pipeline, fulfilling its purpose. When the buoyancy element and the portion of the pipeline on which it is located touch the bottom, that assembly has to be returned to the pipelay vessel to be reused. For this purpose, divers, underwater robots or any system for detaching the buoyancy element from the pipeline is used. When the buoyancy element floats to the surface, it has to be returned to the pipelay vessel using appropriate means of transport, which is why it is necessary to use the assistance of an additional ship that retrieves such discarded buoyancy elements and returns them to the pipelay vessel. With the use of the system for maintaining an arbitrary distance of the buoyancy element according to this invention, the need for a larger number of buoyancy elements is no longer present, as a significantly smaller number of buoyancy elements can be used with the use of this system. The position of the buoyancy elements along the immersed portion of the pipeline can be adjusted as necessary, which is described below.

Disclosure of the invention

The objective of the invention is to decrease the total number of buoyancy elements (number of elements = on the pipeline + on the bottom before return + standing by on the pipelay vessel), to decrease the number of working hours directly or indirectly relating to the buoyancy elements, and to decrease the cost of the project. Other than decreasing the number of buoyancy elements on the pipelay vessel, this system can replace the so-called "stinger" (descending ramp) (figure 3), which is utilized for the purpose of assuring the structural integrity of the pipe. If the project is brief or the need for a stinger is short-term, the transport and installation time of a stinger may significantly increase costs.

Other objectives and advantages of the invention will partially be set forth in the following description.

Brief description of the figures

The enclosed figures, which are included in the description and are a part of the description of the invention, show the best manner of implementing the invention, and assist in explaining the basic principles of the invention. Figure 1 shows the appearance of the main structure of the system for the application of the buoyancy tanks on the underwater pipeline.

Figure 2 shows the manner of installation of the invention and the buoyancy tank on the pipeline before departing to the pipelay vessel.

Figure 3 shows the system of the assembly-buoyancy element in an operative position. Figure 4 shows the longitudinal cross-section of the assembly and the brake mechanism. Figure 5 shows the activity of the brake plate and the assembly with wheels in the event of an increase of the exterior diameter of the pipeline.

The invention consists of a main structure (1), which supports a receiving framework (7), a central rotational portion (2)(3)(4) that consists of two pulleys (2)(4) and a gear (3) on an axle (5), and a brake rod (14) and a brake plate (6) that are connected to a rack (13) linked to a gear (3). The connection between the brake rod (14), brake plate (6) and rack (13) is a hinge joint and allows rotation of all stated elements on the transverse axis of the assembly. On the central rotational portion (2)(3)(4), all elements are mutually attached and rotate together on the axle (5). On the receiving framework (7), there is an assembly with wheels (8) that enables progression along the pipeline. The receiving framework (7) can rotate in respect to the main structure (1), whereby the system can be removed from the pipeline, and while in an operative position, they are restrained with a pin (20) or in another manner. One pulley (4) serves as a connection with the buoyancy element via the link with the buoyancy element (10), while the other (2) serves as a connection with the pipelay vessel (9), by which the desired distance from the pipelay vessel will be maintained. The gear (3) serves as the actuator of the rack (13), which creates pressure on the brake plate (6) and prevents the movement of the system along the pipeline by using friction.

Description of operation and installation

The system is installed on the pipeline in a workstation that is located at the very end of the pipelay vessel. Figure 2 shows one manner of installation. The assembly is placed on the pipe (18) with the framework (7) raised, which is restrained in that position with the pin (20) or with other means for achieving a connection using force. This is then linked with one or more straps (19) onto the pipe that is being installed. A cable is placed on the pulley (2) that will be connected with the pipelay vessel or with the assembly in front (if serially connected as in figure 3), and on the other pulley (4) a link with the buoyancy element (10) is mounted, which will later be connected with the buoyancy element (15). As the installation of pipe progresses, the assembly begins to move towards the ship's exit and then both links, the link with the buoyancy element (10) and the link with the pipelay vessel (9) using straps (19) prevents the pipe from becoming entangled with the ship's equipment. As the assembly moves towards the pipelay vessel's exit, the mounting of the buoyancy element (15) on the pipe (18) using straps (19) of an appropriate size is executed. Since the buoyancy element is connected to the pipe, the link with the buoyancy element (10) is installed in the loop of the buoyancy element and thus the connection between the assembly and the buoyancy element is achieved.

As pipe installation progresses, the assembly together with the buoyancy element (15) approaches the appropriate depth for initiating the operation of the assembly, where the cable (9) that is linked with the ship is fixated in one location that serves for further maintenance of the distance of the assembly from the pipelay vessel. One possible manner of activating the system is by using divers. The diver removes the pin (20) from the framework (7), where the same is unlocked. After that, the diver places the framework in the appropriate position and once again locks it using the pin (20). When the assembly is secured, the diver releases the buoyancy element (15), where it is brought to its operative position powered exclusively by the force of buoyancy (figure 3). After that, the diver removes the straps (19) from the assembly and thus, the system is in operative mode.

Once the buoyancy element (15) is activated i.e. when it is linked only to the assembly, the assembly free of straps (19) and of a restrained framework (7), the entire system is activated in the restrained mode of operation. Buoyancy acts on the pulley (4) via the link with the buoyancy element (10), whereby the pulley has the tendency to rotate counterclockwise. The pulley (4) thusly transfers moment via the gear (3) and creates a force on the rack (13). That force creates pressure via the link rack (13)-brake plate (6) onto the pipe (18). Friction between the brake plate (6) and the pipe (18) prevents movement of the system.

Upon the completion of welding new sections of pipe to the pipeline, the pipelay vessel must move forward in the length of that section. During that movement, the cable (9) (figure 3), which is linked to the pipelay vessel, begins to tighten. That cable is linked to the pulley (2), which is firmly attached to the gear (3) and the pulley (4). The cable (9) is placed on the pulley (2) so that is creates moment in the opposite direction in respect to the moment created by the buoyancy element (15) for the purpose of raising the rack (13) (figure 4 - dashed position), thus enabling the entire system to advance in the direction of the pipelay vessel. When the moment coming from the cable (9) approaches or becomes greater than (which depends on the angle of the pipe on which the assembly is located) the moment obtained from the link (10) with the buoyancy element (15), the assembly begins moving together with the pipelay vessel. At the moment when the pipelay vessel stops, the cable (9) begins to slack and the moment obtained from the buoyancy element (15) prevails the moment obtained from the link with the pipelay vessel (9) and the system enters a restrained state and the entire process begins again.

If the need for a larger number of buoyancy elements (15) arises during the pipeline installation process, then the same can, in the manner described above, be connected serially or in a combination with more assemblies and more links with the ship (9), as shown in figure 3. The only difference with the serial connection is that the link with the pipelay vessel (9) for maintaining the distance is connected to the successive assembly in the designated location (1 1) (figure 4).

In order for the link with the pipelay vessel (9) to always be gently tense (small positive buoyancy), smaller buoyancy elements (16) can be mounted on the link as necessary and thus, this decreases the possibility of something getting caught in the link with the pipelay vessel (9).

In the event of severance of the link with the pipelay vessel (9), the system remains restrained to the pipeline and no danger of loss of buoyancy elements (15) exists.

Any positively buoyant element can be used as a buoyancy element (15). The brake plate (6) and the assembly with wheels (8) are constructed so that their edges of entry are shaped like skis and have the possibility of passing pipeline in the event of changes in the exterior diameter of the pipeline (as shown in figure 5).

The link with the pipelay vessel (9), i.e. the link with the buoyancy element (10) can be executed in the form of a cable, chain or similar. In the shown figures of the system, protection from slippage of the cable or chain has not been shown; however, this protection can be provided at the necessary points, and earlier known solutions from the state of the art can be used as protection. Other than the link with the ship (9) or with the buoyancy element (15), the assembly operates without the need for any power or energy supply.

Experts in this field will find it obvious that numerous modifications and changes can be made to the described system for maintaining an arbitrary distance of the buoyancy element in the process of underwater installation of pipeline according to this invention, without abandoning the scope or essence of the invention.

List of reference designations

1 main structure

2 pulley

3 gear

4 pulley

5 axle

6 brake plate

7 restrained framework

8 assembly with wheels

9 link with pipelay vessel

10 link with buoyancy element

1 1 designated location

12 brake rod support

13 rack

14 brake rod

15 buoyancy element (tank)

16 smaller buoyancy element (tank)

17 rollers

18 pipe

19 strap

20 pin

Claims

Patent claims

1. The system for maintenance of an arbitrary distance of a buoyancy element in the process of laying pipelines, which consists of a main structure (1), which supports a receiving framework (7), a central rotational portion (2)(3)(4) that consists of two pulleys (2)(4) and a gear (3) on an axle (5), and a brake rod (14) and a brake plate (6) that are connected to a rack (13) linked to a gear (3) is characterized by the restrained state of the system on the pipeline being created by the action of the buoyancy element (15) via the link with the pulley (4) connected to the gear (3), which acts on the connection with the rack (13), brake rod (14) and brake plate (6), and whereby the unrestrained state of the system is obtained by moving the pipelay vessel forward in the length of a newly welded section of pipeline (and/or shortening the link with the pipelay vessel (9)) and the link with the pipelay vessel (9) begins to tighten so that it creates moment that acts in the opposite direction in respect to moment that is created by the buoyancy element (15), and with a further increase in tension force, and hence in moment, raising of the rack (13) and brake plate (6) occurs, and the assembly begins to move together with the pipelay vessel.

2. The system according to patent claim 1 is characterized by when the pipelay vessel stops, the force in the link with the pipelay vessel (9) begins to yield and the moment obtained from the buoyancy element (15) prevails the moment obtained from the link with the pipelay vessel (9), which results in an increase of friction at the connection of the brake plate (6) with the pipeline (18), and thus the system once again enters a restrained state.

3. The system according to patent claim 1 is characterized by the assembly with wheels (8) being located on the receiving framework (7), which enables progression along the pipeline.

4. The system according to patent claim 1 is characterized by one pulley (4) serving for the connection with the buoyancy element via the link (10), and the other (2) for the connection via the link with the pipelay vessel (9), by which the desired distance from the pipelay vessel is maintained.

5. The system according to patent claim 1 is characterized by the gear (3) serving as the actuator of the rack (13), which creates pressure on the brake plate (6) and prevents the movement of the system along the pipeline by using friction.

6. The system according to patent claim 1 is characterized by the receiving framework (7) being able to rotate in respect to the main structure ( 1 ) so that the system can be separated from the pipeline, and while in operative mode, the receiving framework (7) is restrained with a pin (20) or other manner.

7. The system according to patent claim 1 is characterized by all elements being mutually connected on the central rotational portion (2)(3)(4) and able to rotate together on the joint axle (5).

8. The system according to patent claim 1 is characterized by the connection of the brake rod (14), brake plate (6) and rack (13) being a hinge joint and allowing rotation of all stated elements on the transverse axis of the assembly.

9. The system according to patent claim 1 is characterized by the link element with the pipelay vessel (9), i.e. the link with the buoyancy element (10) can be a cable or chain.

10. The system according to patent claim 1 is characterized by the buoyancy element (15) that can be any positively buoyant element.

1 1. The system according to any previous claim is characterized by its use in the process of laying underwater pipelines and underwater cables.