RU2493468C2 - Method of pipeline repair - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: repair consists in shutdown, removal of product from the pipeline, opening, cleaning from insulation, evaluation of defectiveness, calculation of remaining life time, rejection and repair of pipes, welding to a line again, insulation, laying and backfilling. Straight pipes are turned about longitudinal axis so that maximum corrosion defects can be located in zenith. Places of ends of taps on horizontal turns are exchanged. Places of taps on bent and convex vertical bends are exchanged. Zones subject to corrosion weakening are treated using a cleaning machine equipped with cutters for metal products or grinding heads. Two versions are considered during calculation of remaining life time: first version - maximum defect on lower half of the pipe to its turn, which develops at growth rate of maximum defect on upper half of the pipe, and second version - maximum defect on upper half of the pipe to its turn, which develops at growth rate of maximum defect on lower half of the pipe. That version is chosen out of the above two versions, which has minimum value.

EFFECT: reduction of consumption of pipes and hand work owing to considering the dependence of corrosion intensity on clock coordinates of the pipe cross section; improvement of mechanisation of processing of corroded sections.

4 cl, 1 dwg

Description

The invention relates to the repair of pipelines, in particular, to continuous re-insulation with the rise to the berm.

A known method of repairing a pipeline, in which the repair is carried out with a stop pumping trenchless method RD 153-39.4-075-01 [1].

Overhauls of crossings by a trenchless method are carried out by replacing a defective section of the pipeline transition inside the operated protective case with a new one, i.e. remove the defective pipeline, - drag a new, defect-free pipeline.

The disadvantages of this method are the high consumption of new pipes, a significant amount of excavation and construction works.

The prototype is a repair method for the STO Gazprom 2-2.3-231-2008 pipelines [2], which consists in opening the pipeline after stopping operation, inspecting this section after removing the insulation coating, assessing the degree of danger of the detected pipe defects and repairing them if necessary replace, back welded into a thread, isolate, put in a trench and fall asleep.

The disadvantages of the prototype is the unjustifiably high consumption of pipes and a significant amount of manual labor during the repair of the pipeline.

The purpose of the invention is to reduce the consumption of pipes and manual labor during the repair of the pipeline by taking into account the actual working conditions, in particular the dependence of the intensity of corrosion on the hourly coordinates of the cross section of the pipe, to increase the mechanization of processing correlated sections.

The proposed method is implemented as follows: stop the operation of the pipeline, free from the product, open it, clean it from insulation, evaluate the defectiveness of the lower and upper halves of the pipes, correlated zones, in particular, zones subject to stress corrosion cracking, are treated using a cleaning machine equipped with cutters metal or grinding heads, defective (having corrosion defects) pipes are rotated around the longitudinal axis so that the greatest metal loss defects ( the greatest corrosion defects) are located at the zenith, at the bends on horizontal bends, swap ends, bends on concave and convex vertical bends swap; when calculating the residual life, two options are considered: the first is the maximum defect in the lower half of the pipe before it turns, developing with the growth rate of the maximum defect in the upper half of the pipe, and the second is the maximum defect in the upper half of the pipe before it turns, developing with the growth rate of the maximum defect on the lower half of the pipe, of the two calculated resources, take the one that has the minimum value; perform the rejection and repair of pipes, weld back into the thread, isolate, lay and fall asleep.

Schematic diagram of the repair of the pipeline is shown in figure 1, in which the following notation: 1 - bulldozer; 2 - overburden excavator; 3 - pipeline; 4 - pipe layer; 5 - power station; 6 - pre-cleaning machine; 7 - post for defective pipes assessment; 8 - a cleaning machine equipped with metal cutters or grinding heads; 9 - pipe cutting post; 10 - grinding point; 11 - pipe rejection post: 12 - welding post; 13 - laboratory for quality control of welded joints; 14 - inventory support; 15 - finishing machine; 16 - equipment for heating the pipeline; 17 - a priming machine; 18 - insulating machine; 19 - laboratory for quality control of insulation coating; 20 - backfill excavator.

After stopping the operation and emptying the product using a bulldozer 1 and an overburden excavator 2, open the pipeline 3, using a pipe layer 4, open it from the bed using a power station 5 and a preliminary cleaning machine 6, remove the insulation, at the defect assessment station 7 assess the risk of defects. Correlated zones, in particular, susceptible to stress corrosion cracking (SCC), are treated using a cleaning machine 8 mounted eccentrically relative to the pipe section being repaired and equipped with metal cutters or grinding heads. The KRC zones remaining after machining with a cleaning machine can be manually sanded. At the post 9, pipe cutting is separated from each other by a batch of pipes of various defects. Defective straight pipes using pipe layers 4 are rotated around the longitudinal axis so that the largest metal loss defects (corrosion defects) are located at the zenith. At bends on horizontal bends, the ends are interchanged. Branches on concave and convex vertical bends are interchanged. When calculating the residual life, two options are considered: the first maximum defect in the lower half of the pipe before it turns, developing with the growth rate of the maximum defect in the upper half of the pipe (practice shows that the corrosion rate can vary by an order of magnitude or more depending on the hourly coordinates of the cross section) and the second is the maximum defect in the upper half of the pipe before it turns, developing with the growth rate of the maximum defect in the lower half of the pipe, from which one that has min The maximum value. Pipes are repaired and rejected at the grinding station 10 and at the rejection station 11 and welded back to the thread in the welding station 12. In the laboratory for quality control of welded joints 13, the quality of the ring joints of the pipeline laid on the inventory supports 14 is checked. After cleaning with a finishing machine 15, using pipeline heating equipment 16, a primer 17 and an insulation machine 18, checking the quality of the quality control laboratory of the insulation coating 19, apply insulation, lay in a trench and fill it with a backfill excavator 20.

Consider an example of calculating the residual life of a pipe that has been in operation for 28 years. On a pipe with a diameter of 1420 mm, a wall thickness of 16.5 mm from X70 steel, a defect A of 1520 mm length and a crack depth of 1.2 mm, and 1.1-2.2, was detected at 6.7-7.4 hours of the pipe cross section a cross-sectional watch revealed defect B with a length of 880 mm and a depth of 0.3 mm. At a working pressure of 7.4 MPa, if defect A is left in the same position, then the remaining pipe life will be only 3 years. If we turn the pipe around the longitudinal axis by about 150 degrees, then the resource of the pipe in the zone of defect A developing with the corrosion rate of defect B will be more than 15 years, the resource in the zone of defect B developing with the corrosion rate of defect A will be 18 years. The minimum residual life of a defective pipe after installing defect A at the zenith will be more than 15 years. Therefore, the considered pipe with defects A and B according to the norms of continuous re-isolation [3] can be left in operation.

The use of the invention allows to reduce the consumption of pipes during the overhaul of the pipeline by taking into account the actual working conditions, in particular, the dependence of the intensity of corrosion on the hourly coordinates of the cross section of the pipe, increasing the mechanization of processing correlated sections, in particular, the processing of zones subject to stress corrosion cracking using cleaning machines equipped with metal cutters or grinding heads. These measures can significantly reduce manual labor and increase the number of pipes left in further operation.

Information sources

1. RD 153-39.4-075-01. Rules for the overhaul of oil trunk pipelines at crossings through water barriers, railways and motorways of categories I-IV (p. 32).

2. STO Gazprom 2-2.3-231-2008. Rules for the performance of work during the overhaul of the linear part of the main gas pipelines (prototype) (p. 15-18).

3. Instructions for the assessment of defects in pipes and fittings in the repair and diagnosis of gas pipelines. - M .: OAO Gazprom, 2008.

Claims (4)

1. The method of repairing the pipeline, which consists in stopping the operation, releasing the pipeline from the product, opening it, cleaning it from insulation, evaluating the defectiveness, calculating the remaining life, rejecting and repairing the pipes, welding it back into the thread, insulation, laying and backfilling, characterized in that the pipes having corrosion defects, rotate around the longitudinal axis so that the greatest corrosion defects are located at the zenith; when calculating the residual life, two options are considered: the first is the maximum defect in the lower half of the pipe before it turns, developing with the growth rate of the maximum defect in the upper half of the pipe, and the second is the maximum defect in the upper half of the pipe before it turns, developing with the growth rate of the maximum defect on the lower half of the pipe, from which one is taken that has a minimum value. 2. The method of repairing the pipeline according to claim 1, characterized in that the ends at the bends on horizontal bends. 3. The method of repairing a pipeline according to claim 1, characterized in that the bends on concave and convex vertical bends are interchanged. 4. The method of repairing a pipeline according to claim 1, characterized in that the correlated zones, in particular, subject to stress corrosion cracking, are processed using a cleaning machine equipped with metal cutters or grinding heads.