RU2674826C1 - Method of welding repair construction to pipeline - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to the field of repair by welding of pipelines of underground and above-ground gaskets, and specifically to a method of arc welding of fillet weld seams of repair structures when installed on pipelines of controlled rolling pipes. Method includes cutting the edges of the ends of the repair structure for welding and installing the repair structure with a gap between the pipeline and the structure from 3.0 to 5.0 mm. Preheating of the ring edges at the ends of the repair structure for fillet welds is carried out in the temperature range from 130 to 150 °C. Then, welding of the longitudinal and annular welds of the repair structure is performed successively. Arc welding of the ends is carried out with the formation of an annular fillet weld around the entire perimeter of the pipeline. Fillet weld is formed by overlaying weld overlay and filling beads. Installation of welded surfacing rollers is carried out so that the extreme welded roller does not overlap the filling rollers. After applying the filling rollers along the contour of the fillet weld, an additional weld bead is applied. Maintain the temperature of the cooling between the overlaid weld rollers in the range from 130 to 170 °C, then the corner weld is cooled at a speed of no more than 40 °C/s by continuous concomitant heating up to 170 °C. Further cooling is performed by covering the insulating belts to a temperature of 50 °C.EFFECT: improving the reliability of the welded joint when performing welding work by obtaining a metal structure on the fusion line and in the heat-affected zone of the welded joint with a viscous component of at least 80 %, which leads to an increase in the bearing capacity of the pipeline.1 cl, 1 dwg, 3 tbl

Description

The invention relates to the field of construction, in particular, to methods of repair by welding pipelines of underground and elevated laying, and specifically, to a method of arc welding of fillet welds of repair structures when installed on pipelines from pipes with controlled rolling.

A known method of welding the coupling to the pipe with an annular fillet weld (Temporary instruction on the technology for repairing welded couplings of pipe defects and welded joints of gas pipelines, OAO Gazprom, 2005), in which first the filler rolls are applied to the pipe, and then subsequent rollers are applied to the other, each subsequent roller overlaps the previous roller by an amount equal to 1/3 of its width. The leg of the weld is equal to the thickness of the weld-in sleeve. The gap between the pipe and the coupling is 2-3 mm. The leg of the weld is equal to the thickness of the weld-in sleeve.

The disadvantage of the welding method is the high heat input into the pipeline metal. On pipelines made of steel with controlled rolling, softening of the metal occurs on the fusion line and in the heat-affected zone, which leads to a decrease in the carrying capacity of the pipeline in these zones, as well as to the formation of cracks. Using the welding method is acceptable only for pipelines of hardened and tempered, normalized steels, as well as hot rolled pipes.

The technical problem, the solution of which is provided by the implementation of the invention, is:

- reduction of heat input into the metal and due to this metal production on the fusion line and in the heat affected zone with high metallurgical quality and high viscoplastic properties;

- refusal to overlap the last contour roller with subsequent rollers and applying the final adjustment roller, which allows to increase the wall thickness in the zone of maximum stress concentration and shift it towards the pipe metal to the zone with lower stress concentrations and structures with high crack resistance.

The technical result consists in increasing the reliability of the welded joint when performing welding operations by obtaining the metal structure on the fusion line and in the heat affected zone of the welded joint with a viscous component of at least 80%, which leads to an increase in the carrying capacity of the pipeline.

The technical result is achieved due to the fact that in the method of welding the repair structure to the pipeline, characterized by cutting the edges of the ends of the repair structure for welding, pre-heating the annular edges at the ends of the repair structure, installing and applying welded surfacing and filling rollers forming an angular weld and the number of which at least two, the repair structure is preliminarily installed on the pipeline with a gap between the pipeline and the structure from 3.0 to 5.0 mm, then after the longitudinal and circumferential welds of the repair structure are thoroughly welded, while the annular edges are preheated at the ends of the repair structure for fillet welds in the temperature range from 130 to 150 ° C, and the arc welding of the ends of the repair structure is carried out with the formation of the circular fillet weld throughout the perimeter of the pipeline, while the installation of welded surfacing rollers is carried out so that the extreme weld bead is not blocked by filling rollers, and after applying the filling shaft An additional weld bead is applied along the contour of the fillet weld, and the cooling temperature between the weld beads is maintained in the range from 130 to 170 ° C, then the fillet weld is cooled at a speed of no more than 40 ° C / s by continuous concomitant heating to 170 ° C, and further cooling is carried out by covering with insulating belts to a temperature of 50 ° C.

The method of welding the repair structure to the pipeline is illustrated by the drawing, where in FIG. The scheme of the method for welding the repair structure to the pipeline is presented.

In the drawing, the following notation:

1 - pipeline;

2 - repair design;

3 - contour roller;

4 - final correction roller;

5 - surfacing rollers;

6 - filling rollers

δm - wall thickness of the repair structure;

δom - wall thickness of the pipeline;

t is the gap between the repair structure and the pipeline;

K1 - leg weld from the side of the pipeline;

K2 - weld leg from the side of the repair structure

The implementation of the welding method consists in performing assembly and welding operations in the following sequence:

- carry out the installation of the repair structure 2 on the pipeline 1 with a gap t between the pipeline and the structure from 3.0 to 5.0 mm using an external centralizer;

- perform a preliminary heating of the longitudinal and annular edges in the temperature range from 130 to 150 ° C;

- perform tacking of longitudinal joints;

- perform welding of longitudinal joints;

- perform welding of the ends with the formation of an annular fillet weld around the perimeter of the pipeline.

The imposition of ring rollers is performed in the following sequence:

a) put surfacing rollers 5, while each subsequent roller overlaps, in width, the previous one is not less than 50%;

b) apply a contour roller 3;

C) apply filling rollers 6, while the contour roller is not blocked by a filling roller;

g) apply the final (additional) roller along the contour of the fillet weld;

d) between the applied rollers maintain the cooling temperature in the range from 130 to 170 ° C;

f) after welding is completed, the fillet weld is cooled at a speed of not more than 40 ° C / s by continuous heating to 170 ° C;

j) cover the fillet weld with insulating belts and perform cooling to a temperature of 50 ° C;

- remove the insulating mats and perform further cooling of the joint in air.

It should be noted that the local (at a length of no more than 1/6 of the perimeter of the pipeline) gap interval between the pipeline and the repair structure from 3.0 to 5.0 mm was chosen experimentally as the most optimal and often encountered in practice, because assembly of the joint without a gap around the entire perimeter is impossible due to the ellipse of the pipeline in diameter.

The choice of preheating the annular edges at the ends of the repair structure for fillet welds in the temperature range from 130 ° to 150 ° C was made from the following conditions:

- when the edges are heated below 130 ° C, the heat input into the metal is insufficient and after welding, in the heat affected zone, a hardening structure of lower bainite is formed, which has low crack resistance due to the high contamination of grain boundaries with non-metallic inclusions;

- when the edges are heated above 150 ° C, the heat input into the metal is excessive, which leads to grain growth and a decrease in the mechanical properties in terms of ductility and viscosity.

In addition, at cooling temperatures between the applied weld beads in the range from 130 to 170 ° C, the mechanical properties of the welded joints in terms of viscosity characteristics at low temperatures and hardness are optimal.

The method of welding the repair structure to the pipeline is shown in the following examples.

Example.

A repair structure 2 is installed on a pipeline 1 with a nominal outer diameter of 219 mm with a wall thickness of 10 mm of strength class K48 2 in the form of a sealed sleeve 1000 mm long (strength class K48, wall thickness of 10 mm, inner diameter of the sleeve is 219 mm) with a gap of 3.0 up to 5.0 mm. Welding is performed with electrodes of type E50A GOST 9466-75, GOST 9467 -75) with preheating of 100 ° C, 150 ° C, 200 ° C. Joints are welded in the same modes.

The results of mechanical tests of welded metal for hardness (HV10) and toughness are as follows:

- preheating of longitudinal, circumferential seams and annular edges of 100 ° C: 24-44 J / cm2 (KCV -40); 220-250 (HV10);

- preheating of longitudinal, circumferential seams and circumferential edges 150 ° С: 52-68 J / cm2 (KCV -40); 205-220 (HV10);

- preheating of longitudinal, circumferential seams and circumferential edges 200 ° С: 29-45 J / cm2 (KCV -40); 190-210 (HV10).

Example 2

A repair structure 2 is installed on a pipeline 1 with a nominal outer diameter of 426 mm with a wall thickness of 10 mm of strength class K48 2 in the form of a sealed sleeve 1000 mm long (strength class K48, wall thickness of 10 mm, inner diameter of the sleeve is 426 mm) with a gap of 3.0 up to 5.0 mm. Welding is performed with electrodes of type E50A GOST 9466-75, GOST 9467 -75) with preheating of 130 ° C, 150 ° C, 200 ° C. Joints are welded in the same modes.

The results of mechanical tests of welded metal for hardness (HV10) and toughness are as follows:

- preheating of longitudinal, circumferential seams and circumferential edges 80 ° С: 24-44 J / cm2 (KCV -40); 225-260 (HV10);

- preheating of longitudinal, circumferential seams and circumferential edges 130 ° С: 52-59 J / cm2 (KCV -40); 200-210 (HV10);

- preheating of longitudinal, circumferential seams and circumferential edges 220 ° С: 25-42 J / cm2 (KCV -40); 180-190 (HV10);

- preheating of longitudinal, circumferential seams and circumferential edges 170 ° С: 54-64 J / cm2 (KCV -40); 180-190 (HV10).

Welding is performed by electrodes of type E50A, E60 according to GOST 9466-75, GOST 9467-75.

Welding of fillet welds is performed by sequentially applying rollers with a total weld leg equal to the thickness of the repair structure 2 without overlapping the contour roller 3 and applying an additional final correction roller 4.

In order to determine the operability of the structure and its optimal characteristics, full-scale experimental work was carried out in production conditions at ambient temperatures up to minus 10 ° C inclusive.

On pipeline 1 with a diameter of 219 mm (2 samples) and 426 mm (2 samples), repair structures of the split tee type were welded. Repair structures with spigots and a diameter of 57 mm were welded on the pipeline with a diameter of 219 mm, and repair structures with a diameter of 159 mm were welded on the pipeline with a diameter of 426 mm.

Non-destructive testing showed the absence of defects of welding origin, as well as mechanical damage and cracks.

As a result, the welding technology parameters specified in table 1 were set.

Welded field samples were tested on a specialized stand for static strength and cyclic durability. The test results of full-scale samples of pipelines with split tees for static strength are shown in table 2.

The test results of full-scale samples of pipelines with split tees for cyclic durability are shown in table 3.

Application of the proposed method provides a welded joint with high metallurgical quality and high visco-plastic properties, which increases its resistance to cracking and, accordingly, increases the carrying capacity of the pipeline.

The proposed technical solution can be used when performing repair work on pipelines.

Claims (1)

A method of welding a repair structure to a pipeline, characterized by cutting the edges of the ends of the repair structure for welding, pre-heating the annular edges at the ends of the repair structure, installing and applying weld surfacing and filling rollers forming an angular weld, the number of which is at least two, while the pipeline is preliminarily carry out the installation of the repair structure with a gap between the pipeline and the structure from 3.0 to 5.0 mm, then sequentially weld the longitudinal and rings welds of the repair structure, while the annular edges are preheated on the ends of the repair structure for fillet welds in the temperature range from 130 to 150 ° C, and the arc welding of the ends of the repair structure is carried out with the formation of a circular fillet weld along the entire perimeter of the pipeline, installation of welded surfacing rollers is carried out so that the extreme weld bead is not blocked by filling rollers, and after the filling rollers are superimposed along the contour of the fillet weld an additional weld bead, and withstand the temperature of cooling between the superimposed weld beads in the range from 130 to 170 ° C, then cool the fillet weld at a speed of not more than 40 ° C / s by continuous concomitant heating to 170 ° C, and further cooling is performed by covering with insulating belts to a temperature of 50 ° C.

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