RU2647062C1 - Method of a large diameter welded pipe expanding, manufactured by bending from a sheet and by longitudinal welding - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the metallurgical industry, namely to methods of welded pipes of large diameters manufacturing. Method provides for expansion by expansion of pipes by movement of rigid segments in radial directions. After their movement to a certain distance, they are diverted from the pipe and rotated by an angle equal to half the angle between the axes of adjacent segments, then moving the segments again in radial directions with the expansion of the pipe. Operations with the segments rotations are carried out after each loading cycle and subsequent unloading with their reciprocating rotational motion with rotations of the segments to angles equal to half the angle between the axes of adjacent segments.

EFFECT: it is also envisaged that the expansion operation with the radial movements of the segments, unloading, their subsequent rotations and repeated expansion of the pipe is carried out only at the end sections of the pipes.

3 cl, 8 dwg

Description

The invention relates to the metallurgical industry, and more particularly to methods for the production of welded pipes of large diameters.

A known method of manufacturing pipes with forming them from sheets by bending, see Japan patent 62-50018, 87.03.04 (application 2-20328). Individual sections of the sheet are bent in the first stage of the process in various directions. But the accuracy of the pipes is very low.

There is also a known method of manufacturing "longitudinally-welded pipes", see German patent 3841795, B21C 37/03, 1990. In a bending mill, a curvature equal to the curvature of the pipe is created, and the pipe edges are welded in the welding unit. But it is precisely after welding that the pipe shape deviates from the cylindrical one, and its accuracy is low. A known method of calibration and straightening of pipes according to US patent No. 4926667, MKI B21C 23/00, B21D 3/00 (NKI 72-256), from 1990, the Method involves the operation of installing a conical mandrel in the pipe and the implementation of its movement along the length of the pipe with her expansion (expansion). But the friction forces between the mandrel and the pipe wall will be very large, and for pipes of large diameters this method is not applicable. The known device according to the patent of Germany No. 2953046, MKI B21D 26/10, provides for the implementation of the method of electromagnetic distribution of pipes, but this method is very difficult to implement for steel pipes of large diameters. Also known is the method described in the monograph of V.N. Shinkin "Resistance of materials for metallurgists", M., Ed. MISiS House, 2013, 655 p. The method involves forming pipes from a sheet by bending, welding, for example, four-arc welding of the inner seam, and then the outer seam, and expansion, that is, expansion of the tube by moving a number of segments in radial directions, see the monograph, pages 575, 599-600.

This method is now the most common and often used, however, when expanding, it is possible to increase the accuracy of the pipe dimensions, but inevitably an undulation of the pipe with short wavelengths is created, and such waves are much more dangerous than the undulation with significant wavelengths.

Due to the destruction of oil pipelines, 10-15 million tons of oil flows annually in the Russian Federation, which leads to losses of up to $ 270 million per year (see the indicated monograph by VN Shinkin, p. 638).

The closest analogue of this invention is the method of expansion according to the copyright certificate of the USSR No. 822952 from 1981

This method includes introducing into the pipe an expander with segments placed on the axes, located relative to the pipe with a gap, moving all segments in radial directions and deformation by expanding segments of its walls.

This method provides improved accuracy along the length of the pipe, but fluctuations in the curvature along the perimeter of the sections remain significant, and the accuracy is low.

The proposed method aims to reduce fluctuations in the curvature and stresses in the pipes, to increase their reliability during operation.

This goal is achieved by the fact that in the expansion process, the expansion pipe is deformed by cycles, on each of which all segments are moved in radial directions and expanded by expansion of the pipe walls, and then they are removed from the pipe to form a gap relative to its wall and rotated by an angle equal to half the angle between the axes of adjacent segments, after which the segments are moved in radial directions and are deformed by expanding sections of the pipe wall with a minimum diameter obtained in the previous cycle.

In addition, an implementation of the method is provided in which the rotation of the segments by an angle equal to half the angle between the axes of adjacent segments is carried out by means of their back and forth motion. In addition, expansion deformation is carried out only by the end sections of the pipe with lengths equal to 1.5-2.0 of their diameter.

It is these distinctive features that provide the solution to the problem: reducing curvature fluctuations, as well as stress values around the perimeter of the pipes, and therefore, increasing their reliability during operation.

An example implementation of the method is illustrated by the drawings shown in FIG. 1, 2, 3, 4, 5, 6, 7, and 8.

In FIG. 1 shows a diagram of a process for expanding a pipe; FIG. 2 - power head of the expander, and in FIG. 3 - one of the segments connected to the hydraulic cylinder, moving it.

FIG. 4 shows the general arrangement of 12 hydraulic power cylinders, and FIG. 5 is a diagram for calculating fluctuations in the radius of a pipe that occur during expansion.

In FIG. Figure 6 shows comparative diagrams of an ideal round pipe and its real configuration after the expansion process is completed.

In FIG. 7 shows the position of the segments after the completion of the first cycle of pipe expansion, their removal from the pipe surface and rotation by an angle equal to half the angle between the axes of adjacent segments.

In FIG. 8 shows a diagram of pipe deformation during the implementation of the second expansion cycle.

In these drawings, the following notation.

The pipe 1 is subjected to pressure from the segments 2, 3, etc., making movements in the radial directions under the influence of hydraulic cylinders 4, 5 and 6, 7, while the shape of the pipe, distorted in the rolling and welding processes, approaches the configuration of a round cylinder .

Hydraulic cylinders are installed in the support cylinder 8, to which the hydraulic drive unit 9 is connected. The support cylinder is mounted on the shaft 10, and the pipe is supported on the drive roller table 11 with rollers having round gauges. There is a portable shaft support 12.

The head of the expander in the form of a support cylinder and a block of hydraulic drives is equipped with a drive for its rotation (rotation) in the form of gears 13, 14 and a hydraulic motor 15. It is possible, of course, to use an electric motor as a drive.

Here is the operational description of the method.

The first operation consists in placing the pipe 1 on a rolling table 11 with profiled rollers and feeding it to the left so that the expander assembly is inserted into the pipe. In this case, the segments 2, 3 and other cylinders 4, 5, 6 and 7, FIG. 1, allotted, so that the diameter of the expander is reduced and between the segments 2, 3 and the pipe 1 there is a gap.

The second operation consists in supplying the movable support 12 and its height adjustment before contact with the shaft 10 of circular cross section. On the rollers of the support 12 provides round gauges.

When implementing the third operation, the expansion of the pipe wall expansion is carried out by the movement of segments 2, 3 and others in radial directions by the action of hydraulic cylinders 4, 5 and 6, 7 mounted on a supporting cylinder 8 (to which the cylinder block 9 and shaft 10 are connected).

It is possible to use an autonomous hydraulic drive for moving segments, in which there is no external supply, of a working fluid (oil), see the article "Autonomous moving module with an electro-hydraulic drive". / Prikhodko B.A., Brovman M.Ya. // "Bulletin of mechanical engineering", 1996. No. 4. S. 44-45. The entire volume of the working fluid is in the cavities of the hydraulic cylinders and in block 9, therefore, when the pistons of the cylinders move, the working fluid moves from one cavity of the cylinder to another, as well as to block 9, and when the segments move in the opposite direction, they move in the opposite directions. Due to this, there is no need to supply a working fluid to the expander and use a hose system (only a wire is supplied to power the pump motors in block 9, but batteries can also be used for this purpose).

The fourth operation consists in the fact that after deformation of the expansion of the pipe section, all segments (2, 3, etc.) are retracted by cylinders 4, 5, 6, 7 so that a gap forms between the segments and the pipe surface. The position of the segments before the process of their removal from the surface of the pipe 1 is shown in FIG. 2.

In FIG. 3 shows separately segment 2 with a drive for moving it in the form of a hydraulic cylinder 4.

In FIG. 4 shows the location of all segments, now most often they use their number equal to 12, so the angle between the axes of the individual segments (4 cylinders) is

его поверхность соответствует линии А' В'.After completion of this operation, the pipe diameter is increased, but its shape does not correspond to a circular arc, as illustrated in FIG. 5. The surface of one expander corresponds to the line AB, and when the expander moves along the x axis (along Ox) and moves it by an amount

its surface corresponds to line A 'B'.

The adjacent segment moves at an angle α to the line Ox along the axis Ox '.

, показанной на фиг. 5 пунктиром, а линии А'В', при этом наибольшее отклонение профиля трубы от окружности постоянного радиуса

равно отрезку А'С, фиг. 5.The surface of the pipe with an initial radius R ₀ , FIG. 5, does not correspond to a circle of radius

shown in FIG. 5 by a dotted line, and lines A'B ', with the greatest deviation of the pipe profile from a circle of constant radius

equal to the segment A'C, FIG. 5.

In FIG. 6 shows the shape of the pipe using six segments (and the angle α = 60 °).

, которую желательно реализовать, показана пунктиром (на фиг. 6 также показано пунктиром начальное положение сегментов при радиусе трубы R₀). На фиг. 5 и фиг. 6 величины перемещений

сегментов показаны для наглядности в увеличенном масштабе.Here, as in FIG. 5, a circle shape of constant radius equal to

which it is desired to realize is shown with a dashed line (in Fig. 6, the initial position of the segments with the pipe radius R _{0 is} also shown with a dashed line). In FIG. 5 and FIG. 6 sizes of displacements

segments are shown for clarity on an enlarged scale.

), показанной пунктиром.From FIG. 6 that the real pipe shape (along AB and beyond), shown by a solid line at six segments, differs significantly from the circumference (radius

) shown by the dotted line.

The fifth operation, corresponding to the distinguishing feature of the present invention, is that after the segments are removed from the pipe walls, all segments are rotated relative to the expander axis by an angle equal to half the angle between adjacent segments, i.e. at an angle of 0.5α.

The rotation is carried out by the drive through gears 13, 14 from the hydraulic motor 15. In this case, the shaft 10 and the nodes 8, 9 are rotated with hydraulic cylinders and segments.

The position of the segments after turning part 8 with all cylinders and segments is shown in FIG. 7. Here, the arrow shows the direction of rotation. After the rotation, the sections of maximum distances from the center O to the maximum radius on the surface of the segments coincide in radial directions with the sections of the minimum pipe diameter obtained in the previous cycle of its expansion. The point of the maximum radius of segment 2 is located after turning on the same radius with the point of the surface of the pipe M ₂ having a minimum radius.

The sixth operation consists in the fact that all segments (2, 3 and others) are again moved with the help of hydraulic cylinders (4, 5, 6, 7 and others) in the radial directions and the pipe expansion operation is repeated 1. The position of the segments after the sixth operation is shown in FIG. 8.

The position of the pipe wall before the operation is shown here by a dotted line, and on segment 2 it corresponds to the line M ₁ M ₂ M ₃ . The pressure on the wall of the pipe 1 from the side of segment 2 will begin at the point of its minimum radius: M ₂ . The profile of the pipe after the implementation of this operation will no longer correspond to the line M ₁ M ₂ M ₃ , but the line M ₁ NM ₃ M ₄ , and the fluctuation of the radius value will be reduced by 4 times (compared with the value achieved after the first expansion of the pipe). At this stage of the process, expansion of the pipe sections having minimum diameters is carried out.

Further, these operations can be repeated, implementing the third, fourth, etc. deformation expansion cycles of a pipe by pressure of segments after their reverse and subsequent rotation before each new loading cycle by moving segments in radial directions.

But, as calculations show, as a rule, two cycles of pipe expansion (with a turn between their implementation) are enough.

The seventh operation is that after the segments are removed from the wall of the pipe 1, the pipe 1 is moved with a roller table 11 (to the left) to a distance equal to (0.85-0.90) the length of the segments (2, 3 and others), and deformation cycles are repeated pipe expansion with bends between deformation cycles.

These operations are repeated sequentially along the length of the pipe.

It is possible to realize not the rotation of the head 8 with hydraulic cylinders and segments in the same direction (between the expansion cycles of the pipe expansion), but the rotational movement of the segments between the cycles of the pipe deformation.

In this case, the direction of rotation of the head 8 is changed after the implementation of each cycle of deformation of the expansion of the pipe. In some cases, it is sufficient to carry out radial movements of the segments and their subsequent turns (after unloading) only at the end sections of the pipes with lengths equal to (1.5-2.0) of their diameters.

This will provide the opportunity for high-quality welding of pipes along the length of the pipe, and in other sections, deviations of the pipe radii will have a longer wavelength (oscillations of the radius around the perimeter), and such "long waves" (corresponding to ovality, ellipticity) will have a much smaller effect on the strength of the pipe than the vibrations of the profile of the pipe with small wavelengths.

If the length of the end sections subjected to expansion deformation (expansion) is less than 1.5 diameters, the closeness of the configuration of the end sections of adjacent pipes will not be ensured, which will complicate their welding. If the length of this section exceeds two diameters, the deformation zone will be unnecessarily increased. This confirms the optimality of the specified interval.

It is known that stresses arise in a pipe with a wall thickness h when exposed to the internal pressure of a gas or liquid p

where - K is the curvature, the reciprocal of the radius of curvature.

The peculiarity of these formulas is that stresses depend not only on the functions describing the shape of the part (pipe), but also on the curvature, i.e. from the first two derivatives of these functions. With a deviation of x values included in formula (1) by Δp, Δh and ΔK, the deviation of the voltage

Vibrations of curvature are least accurately determined and can cause random fluctuations in stresses, which forces an increase in the safety factor and wall thickness of the pipe, increasing the mass of the pipes (and their cost), most often the third term in (2) makes the largest contribution to the error.

If we assume that the pipe surface shape is described by the equation

- полярные координаты, е, n - постоянные, характеризующие отклонения радиуса трубы от постоянной (номинальной) величины радиуса R₀, то в результате расчетов можно определить кривизну в видеwhere r and

are polar coordinates, e, n are constants characterizing deviations of the pipe radius from a constant (nominal) value of radius R ₀ , then as a result of calculations it is possible to determine the curvature in the form

до

дают интервал возможных колебаний величины кривизныwhere ƒ ₁ , ƒ ₂ are functions e, n, which, when changing from

before

give the interval of possible fluctuations in the magnitude of the curvature

.An important conclusion follows from this: the relative fluctuations of the curvature, according to the formula (2) of the stresses, increase with increasing

.

и при

, то при n=12 (как чаще всего при использовании 12 сегментов)

и при e=10^-3

.If, for example,

and with

, then at n = 12 (as most often when using 12 segments)

and at e = 10 ^-3

.

Fluctuations in the curvature within ± 0.286 can be dangerous for the durability of the piping.

Known expansion methods for n = 12 create curvature fluctuations with short wavelengths, and this can be dangerous for pipes.

, то реализуется величинаIf the number of segments is “n”, and their movement in one loading cycle -

then the quantity

,

,

and at small values

,

,

where α is in radians.

The difference between the radii is S = eR ₀ .

After turning through an angle of 0.5α and the second loading cycle, these values are reduced by 4 times.

Here is an example implementation of the method.

,

,

может возникнуть величинаA pipe with a diameter of 1420 mm is made of steel sheet with strength classes K38 - K65 by bending, and after welding, the difference between the radii is 7-10 mm. After expansion according to formula (5) during the implementation of the first cycle of pipe expansion by segments and at

,

,

a value may occur

.

.

According to formula (5), such a value of "e" will lead to oscillations of curvature

(by the formula (4)).

уменьшатся в четыре раза – доBut after the segments are removed from the pipe, their rotation by 15 ° and the second loading cycle, the values of "e" and

decrease by four times - to

,

,

and such fluctuations within ± 10% can be considered permissible.

Thus, the use of expansion - expansion of the pipe by pressure of rigid segments with unloading, rotation of the segments and repeated operations of loading the pipe after the rotation of the segments - can significantly increase the accuracy of the curvature of the pipe surface and, therefore, reduce the range of possible fluctuations in the magnitude of the stresses, which will increase the reliability and durability of the pipes.

Claims (3)

1. A method of expanding a large-diameter welded pipe made by bending from a sheet and welding with a longitudinal seam, including introducing into the expander pipe with segments placed on its axis, positioned with a gap with respect to it, moving in the radial directions of all segments and deformation by expanding its wall with segments, characterized the fact that the expansion pipe deformation is carried out in cycles, on each of which all segments are moved in radial directions and the pipe wall expansion is deformed with the image sections with maximum and minimum diameters, and then they are diverted from the pipe with the formation of a gap relative to its wall and rotated by an angle equal to half the angle between the axes of adjacent segments, after which the segments are moved in radial directions and are deformed by expanding sections of the pipe wall with a minimum diameter obtained in the previous cycle. 2. The method according to p. 1, characterized in that the rotation of the segments by an angle equal to half the angle between the axes of adjacent segments is carried out by means of their reciprocating motion. 3. The method according to p. 1, characterized in that the expansion deformation is carried out only by the end sections of the pipe, the length of which is 1.5-2.0 of their diameter.

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