SU1712729A1 - Method for repair of sagging and exposed sections of underwater pipeline - Google Patents

Abstract

The invention relates to the construction and can be used in the repair of existing subsea pipelines on their sagging and blurred section. The purpose of the invention is to increase the reliability of the pipeline having opposite curvature sections by reducing the stresses in it by changing the boundary conditions of the bent section being repaired. Repair of the fuzzy section 2 of the pipeline ^^ 1 is carried out using the "replanting" method, for which the trench is opened at section 2 and the adjacent sections 4, 5, of the opened section of the pipeline and a trench of the calculated depth is developed at sections 3, 4, 5. After that, the raised pipeline is placed on new marks and trench is filled in these sections. 3 or.

Description

The invention relates to the construction and can be used in the repair of existing subsea pipelines on their sagging and blurred areas, i

The purpose of the invention is to increase the reliability of the pipeline having areas of opposite curvature by reducing the stresses in it by changing the boundary conditions of the repaired curved section.

FIG. 1 shows an underwater pipeline with a blurred section and two adjacent areas with curvature of opposite sign; in fig. 2 the position of the opened area with the developed trench; in fig. 3 - underwater pipeline after the depth of the repaired area.

The decision to repair the subsea pipeline is made as a result of a survey that determines the exposure of its sections. After detecting the bare sections of the pipelines, surveys are made that predict the erosion of the bottom of the reservoir and, in relation to the new forecast, the pipeline must be laid in accordance with SNiP 2.02.06-85.

In order to deepen the curvilinear section of the underwater pipeline 1 at the pasMbiTOM section 2, it and the adjacent sections of pipeline 1 of opposite curvature are lifted and all opened sections of pipeline 1 are lifted, after which they are developed with a trench 3 of sufficient depth to meet the required requirements for pipeline strength. Simultaneously with the development of trench 3, trenches 4 and 5 are developed to the right and left of the fuzzy section 2 (Fig. 2) of the necessary extent, having the curvature of the opposite sign relative to the fuzzy section 2.

During the opening of the trenches, the pipelines 1 are lifted in order to eliminate the friction forces of the pipeline against the ground, facilitate the longitudinal movement of the pipeline towards the adjacent from the eroded section 2 to the trenches 4 and 5 and deepen the pipeline along the profile of the newly prepared trenches. The elevation of the subsea pipeline section is carried out at a certain angle a. while maintaining the distance f between the suspension points to ensure the pipeline sags on the diffuse section 2.

The magnitude of the angle a and the length t are assigned in accordance with the calculation by the methods of reinforced metal and should ensure

convexity of section 2; in this case, the stresses in pipe 1 should not exceed the elastic limit. The optimal values. and the angle a allows creating a horizontal component, which helps to reduce the convexity of the curvilinear section 2. After the trenches 3-5 of the calculated depth are cut, the pipeline 1 is placed on new marks and the trenches 3-5 are filled in.

This method allows the subsea pipeline to be repaired by the replanting method, and if the boundary of the repaired area 2 extends beyond the pond, the replenishment of the section of the pipeline 1 located on land follows the same recommendations as for the underwater part of pipeline 1, It is possible to repair the pipeline by landing on straight sections or straight sections adjacent to the curved section of the pipeline being repaired.

Example. Project solution for

repair of the underwater crossing of the Ust-N main oil pipeline. Vartovsk across the Ob River.

The pipeline section e 1020 mm, having a convex shape, was eroded.

The main idea of the invention is to compensate for the extra space between the lower generatrix of the pipeline 1 and the new position of the pipeline 1 with its redistribution to the adjacent areas 4

and 5, for which the area of the lower generatrix of the pipeline 1 and the curve representing the new position of the buried pipeline is calculated. For the position shown in FIG. 1, she made up

493.0 m.

Depthing options are selected from one adjacent side, two or more adjacent pipeline sections. It was decided to carry out burial in

two adjacent sides.

The depths of the repaired 2 and adjacent 4 and 5 sections are underlined with the definition of the areas of these sections. At the same time, the amount of specialized areas

adjacent sections 4 and 5 should be no less than the profiled area of the blurred area 2, equal to 493 m. The profile area of section 4 is chosen, equal to 303 m, and the area 5-204 m. Depth is calculated

replanting depending on the stress state of each section, but not less than 1 m from the maximum possible predicted erosion. The smallest bending radii of the pipeline are calculated on

plots 2.4 and 5, the stress in the pipeline at these sites and the vertical coordinates of the pipeline. In section 4, the radius of curvature was 2000 m, and the stress was 0, 55 MPa; in the area of m and 1.5 MPa, respectively. At the same time, the voltage on the convex section 2 decreased to 1.36 MPa. In the process of laying new marks, it is necessary to measure the position of the pipework 1. If the pipeline does not occupy the required position due to its friction on the ground or other reasons, it should be raised The angle a must be at least 10 °, which greatly simplifies the depth of the subsea pipeline. Excludes work on the displacement of the pumped product (oil or petroleum product) with water from the underwater pipeline, the creation of a temporary barn ground for storing the displaced oil or petroleum product, cutting the pipeline section 2 and welding the coil. By eliminating the emptying of the subsea pipeline and the temporary storage of oil or petroleum products in the earth barn, they are prevented from entering the environment and contaminated. The absence of the need to insert a coil eliminates fitting, alignment of the pipeline and welding work, which reduces the laboriousness of repair work and improves environmental protection. F o rmu l and zo brie nt A method for repairing sagging and eroded sections of a subsea pipeline, which consists in opening the repaired section of the pipeline, deepening the trench beneath it, then laying it on new marks of laying and filling it with soil other than that. that, in order to increase the reliability of the pipeline with areas of opposite curvature by reducing the stresses in it by changing the boundary conditions of the repaired curved section, they open areas of opposite curvature adjacent to it and lift all exposed sections of the pipeline, while deepening the trench and laying the pipeline before filling it The new estimates are made for the entire raised section of the pipeline.

Ф (/ г.З

Claims (1)

Claim The method of repairing sagging and washed out sections of the underwater pipeline, which consists in opening the repaired section of the pipeline, deepening the trench under it, then laying it at new markings and backfilling, characterized in that. that, in order to increase the reliability of the pipeline having sections of opposite curvature by reducing stresses in it by changing the boundary conditions of the bent section being repaired, open adjacent sections of the opposite curvature and raise all exposed sections of the pipeline, while deepening the trench and laying the pipeline before filling it with new ones design marks are carried out for the entire elevated section of the pipeline. FIG. 2 I Fig.Z