RU2425273C2 - Procedure for repair of pipeline - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: when pipeline is lifted for cleaning from old insulation and for application of new insulation, height of lifting, selection of quantity and arrangement of pipe layers are determined considering limited deformation of pipeline metal in places with minimal value of radius of curvature causing change of critical temperature of metal brittleness to values of temperature of environment.

EFFECT: prevented destruction of pipeline at insulation-laying operations due to transition of deformed pipeline into brittle condition at reduced temperature of environment; raised safety of repair operations.

1 dwg

Description

The invention relates to the repair of pipelines, in particular to the repair of the pipeline with the rise in the trench and laying.

A known method of repairing a pipeline, which consists in repairing the body of the pipe, insulation, laying of the pipeline with its subsequent filling with soil [1].

The disadvantage of this method of repairing a pipeline is that when determining the height of the lift, the number and placement of pipe layers do not take into account the ambient temperature.

The prototype is a method of repairing a pipeline, which consists in stopping operation, opening, lifting a gas pipeline by pipe layers, cleaning it from insulation, laying it in a trench, diagnosing, repairing the pipe body, finishing cleaning, insulation with lifting, laying on a bed, backfilling, testing and putting it in operation [2].

The disadvantage of the prototype is that when determining the height of the lift, the number and placement of pipe layers do not take into account the ambient temperature.

The aim of the invention is to reduce the likelihood of pipeline destruction during insulation and laying operations due to the transition of the deformed pipeline to a brittle state with a decrease in ambient temperature, therefore, improving the safety of repair work.

The goal is achieved by the fact that during insulation and laying works, the lifting height, the choice of the number and the arrangement of the pipe layers are carried out proceeding from the condition of limiting the deformation of the gas pipeline in places with a minimum radius of curvature to a value causing the critical temperature of brittleness of the metal to reach ambient temperature.

The essence of the invention is illustrated in the drawing, which adopted the following notation: 1 - pipeline; 2 - pipe layer; 3 - trench; 4 - cleaning machine; 5 - lying; 6 - insulating machine.

Repair of the pipeline by the proposed method is carried out in the following sequence. Stop operation and open the repaired section of the pipeline (1). The pipeline (1) is lifted by the pipe-laying machine (2) into the trench (3), cleaned with insulation using a cleaning machine (4) and laid on the laying (5) in the trench (3). The pipe body is diagnosed and repaired, after which it is lifted with the help of pipe layers (2), after finishing cleaning, corrosion protection is applied using an insulating machine (6). The pipeline (1) is laid on the bed and covered with soil from the blade. A strength test is carried out, for example, through passage pressure. After testing for strength and density, the pipeline is put into operation.

In the project of works, the determination of the height of the pipeline and the choice of the number of pipe layers is based on the condition of limiting the deformation of the metal of the pipeline in places with a minimum radius of curvature to a value that causes the critical temperature of brittleness (CTX) [3] of the metal of the pipe to reach ambient temperature.

It is known that the relative deformation of the pipe metal ε in the cross section z can be determined by the dependence:

where D _n is the outer diameter of the pipe;

M _Z - bending moment;

EI - bending stiffness of the pipe.

By limiting the relative deformation of the pipe wall ε to the value of the relative deformation of the temperature of brittleness of the metal (at ambient temperature), the allowable value of the bending moment can be determined by the dependence:

For example, for a carbon steel pipeline, the relative deformations of the pipe body, causing an increase in the critical temperature of the brittleness of the pipe metal to a temperature of 8 ° C, is 0.05, and to a temperature of minus 5 ° C - 0.02. Therefore, the value of the permissible bending moment for a carbon steel pipe at a temperature of minus 5 ° C is 2.5 times less than at a temperature of 8 ° C.

The invention allows you to choose a lifting scheme (the height of the pipeline, the number and placement of pipe layers), limiting the value of the permissible bending moment taking into account the ambient temperature, to prevent the transition of the deformed pipeline to a brittle state when the ambient temperature decreases, its destruction during insulation and laying operations, therefore to increase the safety of repair work.

Literature

1. Rules for the performance of work during the overhaul of gas pipelines. BCH 51-1-97. - M .: 1997.

2. Rules for the overhaul of oil pipelines. RD 39-00147105-015-98. - Ufa: 1988, 104 p. (prototype).

3. Hall, W.D., Kihara X., Zut V., Wells A.A. Fragile fracture of welded structures. - M.: Mechanical Engineering, 1974.

Claims (1)

A method of repairing a pipeline, which consists in stopping operation, opening, lifting a gas pipeline by pipe layers, cleaning it from insulation, diagnosing, repairing the pipe body, insulation with lifting and backfilling, characterized in that the choice of quantity, placement of pipe layers and lifting is carried out based on the condition for limiting metal deformation pipeline, in places with a minimum radius of curvature, a value that causes the critical temperature of brittleness of the metal to reach ambient temperatures.

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