RU2418222C2 - Method to lay manifold pipeline in construction of deep-water passage - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: long hinges are assembled on land. To provide neutral floatage of a joint, plastic couplings are fixed on the pipe, or polymer materials are wound onto the pipe with positive floatage. One end of the joint is pushed into water with the help of trusses serially fixed on the bottom in the form of frames with rollers of soft materials and is filled with water. On land a new joint is connected to the other end and is submerged into water, forming the pipeline run. The free end arranged in water is towed with a vessel. The pipeline run is located at the depth that does not interfere with navigation in suspended condition. After the run achieves the specified trajectory, the pipeline is submerged and retained in suspended condition with the help of anchors fixed on it with the help of flexible cords.

EFFECT: invention provides for continuous process of pipeline laying, which does not interfere with navigation, accelerated process of installation, application for wide range of depths and dimension types of pipes.

6 cl, 6 dwg

Description

The invention relates to the construction and can be used in the construction of deep-sea trunk pipelines when crossing over wide water spaces such as seas and oceans.

Recently, the volume of construction of submarine pipelines has increased significantly, including the need for the construction of crossings through deep-sea spaces. The invention addresses the issue of building a deepwater trunk pipeline.

Conventional methods for laying a water passage, such as the method using an inclined stinger, the J-method, are implemented by continuous assembly (welding) of pipes, inspection, pipe preparation, ballasting (usually concrete coating), etc. directly on a ship afloat. The welded pipes are immersed in water by pushing them over the ramp using a stinger or by lowering them at a high angle from the tower on a ship (J-method). The methods have limitations on the speed of work due to weather conditions and the need to transport pipes by sea. Also significant disadvantages are the stresses arising during operation due to the tension of the pipeline to hold it above the surface of the water on the vessel and bending the pipes when lowering to the bottom. The combination of these stresses can lead to loss of pipe stability and its destruction. There are serious restrictions on the depth of laying the pipeline (B.V. Samoilov et al. Construction of submarine pipelines. M: Nedra, 1995). A fundamental feature of the methods described above is their cyclical nature due to interruptions in the process chain. As an alternative to these methods, a method of laying using drums is used, the essence of which is that a long whip of a pipeline prepared and welded from several pipes in a dock is wound on a drum mounted on a vessel. Laying the pipeline is carried out by winding the drum into the sea. After that, a plug is welded to the pipe, marked with a buoy and lowered to the bottom. Upon arrival of a new “charged” drum, the pipe is lifted, the plug removed, welded to the free end on the drum and the stacking process resumes. Unlike the methods with the stinger and the J-method, the pipeline is not concreted, but pipes with a larger wall thickness are used to achieve negative buoyancy. The disadvantages of this installation method include restrictions on the diameter of the pipe due to the need to wind it on the drum and due to this the occurrence of residual ovality and helicity (B.V. Samoilov et al. Construction of underwater pipelines. M .: Nedra, 1995).

The performance and cost of all the above methods are influenced by the stringent requirements for the bottom topography, since the pipeline lies directly on the bottom. These requirements lead to the need to lay the pipeline not on the shortest path, but in accordance with environmental conditions, which also leads to a rise in the cost of the project. In addition, the prevention of the emergence of the pipeline, which is achieved by ballasting, becomes one of the essential elements of the pipeline. According to statistics, the main causes of accidents are caused by the movement of the pipeline along the bottom, impacts of pipelines about rock formation, insufficient ballasting, sagging of pipelines due to soil erosion (Levin S.P. Accident prevention and repair of underwater pipelines, 1963; Kamyshev M.A. et al. Construction offshore pipelines). To combat the error in ballasting and mechanical hardening of the pipeline, the thickness of its walls is increased (Kamyshev MA and other new equipment and technology for the construction of underwater crossings of trunk pipelines, 1987).

A known method of laying a pipeline during the construction of a deep sea passage, however, the laying of lashes is carried out on the surface of the water without them (lashes) immersing and filling with water during the laying of the pipeline. The lashes are filled with water only if it is necessary to open the passage for the vessel (there are holes in the pipeline for this), however, after the passage of the vessel, the lashes are freed from water and their assembly into the pipeline continues on the surface of the water (Borodavkin P.P., Berezin V .L., Shadrin OB “Underwater pipelines”, M .: Nedra, 1979).

The above technical solutions are selected as a prototype, since they are the closest in their technical essence to the claimed invention and represent developments that have found application in the practice of laying underwater pipelines.

The proposed method of laying eliminates a number of disadvantages associated with the general method of laying and piping.

The technical result of the claimed invention consists in providing continuous laying of the main pipeline throughout the entire technological process, which does not impede navigation, and with further flooding of the entire pipeline taking into account the topography, accelerating the laying process, reducing costly earthworks and expanding the scope for wide ranges of depths and sizes of pipelines due to the absence of pipe deformation, which can lead to their destruction, in the process laying on the bottom due to their filling with water, since in this case no pressure differences inside and outside the tube during the technological process napkin.

The technical result is achieved in the method of laying the main pipeline during the construction of the deep sea passage, which consists in the sequential assembly of the pipe lashes on land, then the assembled lash is immersed in water, the next lash is attached to one end to form the pipe thread, and the pipe thread is filled water in the process of laying and placed using a compensator for buoyancy in suspension at a depth that does not interfere with navigation, and after The pipeline assembly stage is flooded and suspended in water near the bottom, taking into account its relief.

The implementation of the deep-sea passage consists in placing in the water column at a depth near the bottom of the suspended pipeline, which is filled with water at the laying stage, which eliminates the destruction of pipes by external pressure at this stage. An arbitrary ascent is prevented by anchors fixed at the bottom, connected by a cable to the pipeline. Initially, the pipes are prepared for assembly (they carry out all stages of control, anti-corrosion treatment, etc.) on land at the point of transition. Long lashes are made by welding pipes or in another possible way. The lashes are assembled using additional structural elements that provide variable buoyancy, as well as structural elements for anchoring the anchors to the pipeline. In addition, using devices that regulate the buoyancy of the anchor itself. The assembled lash is laid on trolleys or rollers and immersed in water, a new lash is attached to the free end and so form the thread of the pipeline. Thus, the pipeline thread, immersed in water, is placed in suspension at a depth that does not impede navigation in the area of work. In water, the free end of the pipeline is towed by a vessel with a device that provides towing at a constant depth and dampens vibrations as much as possible due to the influence of waves. After reaching the pipeline thread a predetermined path along the entire length of the transition, it is flooded to the bottom. Since the anchors themselves in their free state have negative buoyancy, their weight is used to flood the pipeline. After anchoring the anchors at the bottom and assuming the thread of the pipeline to its final position in the suspended state in the water, the sections located on the shelf are covered with soil to give the structure additional stability and protect the pipeline from mechanical stress. Water is replaced with a working fluid by means of piston separators.

The drawings illustrate the method of laying the pipeline and the sequence of actions.

Figure 1 shows one of the options for the pipeline section in assembled form.

Figure 2 shows the process of placing the pipe thread at a given depth.

Figure 3 shows a device that is used to guarantee the prevention of the emergence of the pipeline to the surface.

Figure 4 shows the placement of the pipeline in the water column at a constant depth in places of currents.

Figure 5 presents the option of flooding the pipeline thread after the final location along the entire length of the transition, starting on the one hand, when securing the pipeline on one bank and continuing assembly on the other.

Figure 6 presents the option of flooding the pipeline thread after the final location along the entire length of the transition, starting from the middle, with continued assembly from both banks.

When assembling the pipeline onto the pipe 1, crimp couplings of the roller bearing type 5 are installed, designed to fix the cables 8 and anchors to them to hold the pipeline at the bottom. The bearing rings consist of two parts and are fastened together by a threaded connection. The anchor cable 8 is fixed on the outer ring of the bearing in any reliable way. The ring is made with a groove. The cable 8 is wound on a ring of the required design length for fixing the pipeline at a depth in a suspended state, taking into account the topography of the bottom. Near the bearing 5 establish a separation disk 6, also consisting of two halves and playing the role of protection. The disk is fixed to the pipe 1 by crimping it or attached to the inner ring of the bearing 5. After the disk 6, a casing 3 is installed. The casing 3 is a prefabricated structure and consists of an internal hollow cylinder (the inner diameter of the cylinder is larger than the outer diameter of the pipe) and attached to it through stiffener ribs in the form of a truncated cone. The lower part of the truncated cone has a "pocket" 4. In general, the casing 3 consists, like the bearing rings 5, of two halves, which are mounted on additional small-diameter roller bearings 7 located on the pipe 1 and connected using threaded connections. This design and installation of the casing 3 on the pipe 1 is due to the need for the location of the "pocket" 4 necessarily under the pipe.

When assembling the whip of the pipeline, neutral buoyancy is calculated (taking into account the average density of water along the entire route) and is achieved by fixing plastic couplings 2 on the pipe 1 or winding polymer materials with positive buoyancy on the pipe, the layers of which are glued together and give the pipe additional strength. The winding of the polymer material can be performed along the entire length of the pipe and serve as anti-corrosion protection. Neutral buoyancy is achieved, including the location under the upper part of the casing 3 elastic sealed shells filled with air. Calculation of neutral buoyancy is carried out taking into account the fact that the pipeline during the installation process will be filled with water. The arrow indicates the direction of movement of the pipeline in the water.

The number of bearings 5 (respectively, anchors) depends on the topography of the bottom, the structure of the bottom surface, the presence and strength of bottom currents and other factors affecting the stability of the pipeline thread.

According to the neutral buoyancy condition, the total weight of all the constituent parts of the pipeline section is equal to the water pushing force acting on the calculated section. The weight of the pipeline section should be distributed as evenly as possible along its length. Moreover, the calculation does not take into account the weight of the anchors.

At the final assembly, an anchor is attached to the cable 8 wound on the bearing 5. Neutral buoyancy of the anchor is provided by a separate variable buoyancy system - a buoyancy compensator (hereinafter KP) - with a power and control unit similar to the scuba diver system and consisting of:

- cylinder with compressed air,

- buoyancy compensator - an expandable elastic chamber that can be inflated or deflated, with inlet and outlet solenoid valves,

- a device for controlling the operation of valves with a pressure sensor (depth), an air pressure sensor in the cylinder and the ability to control by radio signal,

- power supply unit of the control device.

The gearbox is rigidly connected to the anchor, filled with air to maintain the entire neutral buoyancy device at an estimated depth h that does not impede navigation, and put into the “pocket” of the casing 4. The anchor together with the gearbox are fixed inside the “pocket” 4 in any reliable way that ensures that this is released device and its loss from the "pocket" with the full deflating of the elastic shell. Due to the large mass of the obtained device (gearbox together with the anchor), it is possible to fasten it to a cable and place it in a "pocket" 4 in water at a depth of 1-2 m using scuba divers, which will make it possible to lighten the casing 3 as much as possible.

The control device adjusts the volume of the elastic chamber by reading the depth sensor, inflating and deflating it, thus supporting the gearbox together with the anchor at a constant depth h. As an additional function, the CP performs the task of regulating the neutral buoyancy of the entire pipeline section as a whole. To do this, the device (KP together with the anchor) is rigidly connected to the pipeline, for example, using a rope with a tensile force less than the total weight in the water of the KP and anchors without air in the shell, or in another way. In addition, since the density of water in the sea differs from place to place due to changes in salinity, it is quite significant, as a result of which the force of water ejection applied to the section of the pipeline is different, KP will also regulate the position of the pipeline in the water.

The weight of the anchor is calculated on the condition that the entire section of the pipeline is not flooded with unauthorized release of one or more anchors from the "pocket". In this case, the rest of the control should maintain neutral buoyancy of the site, and the control device should signal the presence of an emergency to eliminate it.

When placing a small number of anchors on the pipeline in a long section of the pipeline, they are additionally placed in such sections of the pipeline separately without anchors in protective casings with adjustment for calculations of neutral buoyancy. In this situation, they will additionally contribute to finding the pipeline at a given depth h and stabilize its horizontal position.

A whip of the pipe 9 is placed on the railway carts or rollers 11 and led into the designed target by pushing it with a certain device 12, for example, a locomotive. The scourge is immersed in water using a system of sequentially installed in the place of descent and securely fixed to the bottom of the truss in the form of frames 10 with rollers 14 made of soft materials. The last frame provides the location of the pipeline at a given depth h, equal to 40-50 meters, where there is practically no influence of waves (up to storms with a force of 5 points), and which does not impede navigation in this area. Moreover, this depth allows you to carry out certain work with the pipeline 9, using scuba divers, for example, replacing an empty cylinder with air or the like. The frame system 10 also serves as a stabilizing element of the entire structure and prevents the strong influence of the surf on the pipeline section 9 located on land. The free end on land is rigidly fixed, a new lash is attached to it, the quality of the joint is checked and pushed back into water, etc.

When the pipeline moves, the pushing device 12 overcomes the frictional force that occurs when the bogies or rollers move, and the water resistance force, therefore, all pipeline elements are designed in the most streamlined form, while the couplings, casings and bearings have the smallest possible diameter. To stabilize the free end of the thread of the pipeline 9 located in the water, it is supported by the vessel 13 with a device lowered into the water to a predetermined depth h, which allows towing without changing the depth and is able to dampen vibrations as much as possible due to the influence of waves. The vessel 13 is capable of towing at a certain wave height to avoid deformation of the pipeline during vibrations. The movement of the pushing device 12 and the vessel 13 is synchronized as much as possible. If the wave height exceeds the critical level for towing, the device is disconnected from the pipe, the end of the pipe is marked with a buoy, the assembly of the pipeline is stopped.

On top of the pipeline 9 to ensure that it does not emerge at a certain distance from each other, brackets 15 of material with positive buoyancy can be installed. They have a height of 4-5 pipeline diameters and a radius equal to 3-4 pipeline radii. The brackets 15 are installed with a gap in relation to the pipeline 9 and are fixed in several places to the bottom using anchors or weights 16. To reduce the friction force between the bracket 15 and the pipeline 9 during movement, if they come into contact, the brackets are made of several prefabricated parts - arcs - with integrated freely rotating rollers 17.

In places of currents over the pipeline 9 install the same brackets 15, preventing its displacement relative to a given path. In this case, the brackets should have such buoyancy in order to remain together with the pipeline 9 at a given constant depth h and prevent its immersion, which is achieved by placing additional floats 18 on the brackets 15.

When the thread of the pipeline 9 reaches the land exit point, the free end is connected to the lashes prepared on land in a similar way. On one of the banks (marked with a cross), the pipeline 9 is rigidly fixed, on the other shore it remains free to lie on railway carts or rollers. Consistently release air from the CP, starting from the side of the rigidly fixed end, the anchors are released from the "pockets" and the pipeline 8 begins to sink. From the side of the free end, they continue to assemble the lashes and immerse the pipes in water (marked with an arrow). In this case, the pipeline 9 is filled with water using pumps to avoid pressure damage at a depth. At this stage, the dive is controlled by a number of floating means 22 located along the pipeline route. During the immersion of the pipeline, part of the anchors 19 are already at the bottom and fixed on it, part of the anchors 20 hang freely on the unwound cables in the water, air has not yet been released from the part of the CP 21.

Flooding of the pipeline 9 can also be carried out starting from the middle. In this case, assembly continues from both banks (marked by arrows).

After the pipeline has reached its final position in the suspended state and anchored, the sections in the water on the shelf are covered with soil to prevent damage and give the structure greater rigidity and stability. The brackets installed on top of the pipeline, if possible, are removed from the water. The replacement of water with a working fluid at the beginning of operation occurs by displacement with the help of piston separators.

It is also possible to lay the pipeline while working from both banks. In this case, the connection of two opposite sections is carried out in the sea on pontoons using threaded couplings, originally placed on the pipes, or by welding.

Since the density of the working fluid (oil, oil products) or gas is less than the density of water, the pipeline during their transportation through it will weigh less than at the stage of laying. Therefore, its sinking to the bottom is excluded. The system of anchors, their mass, size, etc. calculated from the conditions of a guaranteed obstacle to the ascent of the entire device. Thus, the pipeline thread will be suspended in water.

In the claimed invention, using the sequence of the above actions, as well as using a number of devices, the location of the pipeline thread is achieved according to the shortest route between the two transition points. In this case, there is no problem of ballasting the pipeline and carrying out a large amount of underwater excavation due to its location in water in suspension. These activities are carried out only on the shelf. In the process of laying the thread of the pipeline, less significant forces act on it than those arising under tension in the prototypes under consideration, as well as the pressure inside the pipeline and outside at all depths during the laying process is balanced. The influence of stresses arising during bending during the flooding of the pipeline will not have significant significance on the stability of the pipe. In view of this, it is possible to use a wide range of laying depths and pipe sizes. Since the pipeline thread is assembled from long lashes on land, this will significantly increase the laying speed compared to the common methods considered as prototypes.

At the stage of laying pipes may be empty - without water. In this case, technologically, the process looks similar to the considered method. Corresponding corrections are made in the calculations of the buoyancy of the pipeline at the stage of laying and the location of the pipeline thread in the working position in the suspended state at the bottom. Also take into account the water pressure at the working depth, which will certainly lead to an increase in the thickness of the pipe wall and a decrease in its diameter.

Claims (6)

1. The method of laying the main pipeline during the construction of the deep sea passage, which consists in the fact that the lashes of the pipeline are sequentially assembled on land, then the assembled lash is immersed in water, the next lash is attached to one end of it to form the pipeline thread, while the pipeline thread is filled with water in laying process and positioned using a buoyancy compensator in suspension at a depth that does not impede shipping, after the final assembly of the pipeline If it is flooded and suspended in water near the bottom, taking into account its topography, characterized in that the whip is immersed in water using frames that are sequentially installed in the place of descent and securely fixed on the bottom of the bottom, when assembling the whip, its neutral buoyancy is calculated with taking into account the average density of water throughout the route and reach it by fixing plastic couplings on the pipe or winding polymer materials with positive buoyancy on the pipe, we installed the anchor cable on the pipe for attaching the anchor cable ayut crimp sleeve type bearings and housings to contain the buoyancy control system, and an anchor block. 2. The method of laying the main pipeline according to claim 1, characterized in that the framework structurally contain rollers of soft materials. 3. The method of laying the main pipeline according to claim 1, characterized in that the layers of polymeric materials are wound along the entire length of the pipes and glued together. 4. The method of laying the main pipeline according to claim 1, characterized in that the bearing rings consist of two parts and are fastened together by a threaded connection for positioning on the pipe, the outer ring is made with a groove where the cable is wound for anchor fastening. 5. The method of laying the main pipeline according to claim 1, characterized in that the buoyancy compensator is an expandable elastic chamber with air. 6. The method of laying the main pipeline according to claim 1, characterized in that the buoyancy compensator system is a compressed air cylinder, an expandable elastic chamber with inlet and outlet solenoid valves, a valve operation control device and a control unit power supply.

Images