JP2018514387A - Method for induction bending deformation of pressure-resistant pipe having thick wall thickness and large diameter, and induction type pipe bending apparatus - Google Patents

Abstract

When the pressure-resistant tube (1) having a thick wall thickness and a large diameter is subjected to induction bending deformation, the tube (1) is inserted in the vertical direction in the press unit (50) before being inserted into a ring-shaped inductor for heating. And presses the tube (1) in the press unit (50) to force an oblong cross section. Furthermore, at least during a portion of the tube bending process, the inductor is displaced laterally relative to the tube (1) to adjust the temperature distribution outside the bent portion to a relatively low temperature, The temperature distribution inside the bend is adjusted to a relatively high temperature.

Description

  The present invention provides a method of inductively bending and deforming a pressure-resistant tube having a thick wall thickness and a large diameter, in particular a power plant tube and a pipeline tube, having the features described in the superordinate concept of claim 1, and The present invention relates to an induction tube bending apparatus suitable for implementation, having the features described in the superordinate concept.

  In order to pass liquid or gaseous media under pressure, a steel tube with a thick wall thickness that can withstand the load is required. Such a requirement is, for example, to compensate for the transport of hot steam at power plants where pipe bending is required to adapt the pipe line to the structural situation, or to compensate for length changes due to heat. This applies to the transport of crude oil or natural gas in long-distance pipelines where double joints are used at regular intervals. In order to enable a large throughput, a large opening cross-sectional area and thus a large pipe outer diameter is required. The tube to which the method relates has a nominal diameter generally exceeding 300 mm, and the ratio of diameter to wall thickness is 10: 1 to 100: 1, typically 20: 1 to 70: 1. .

  Such a method for inductive bending deformation has long been known, for example, from DE 2513561 A (DE2513561 A1), which is a dimensionally very stable tube despite its large dimensions. Improvements are continuously made so that the bent part can be manufactured. Predetermined bending angles are precisely observed for tube bending, while two disadvantageous shape deviations remain in the region of the tube bend. This is partly the ellipticity, i.e. the deviation of the tube cross section from the desired circular ideal shape, and on the other hand the thinning of the wall thickness at the outer bend.

  Round tubes having the above dimensional ratios are manufactured and shipped with an ellipticity of about 1%. According to the European and North American standards, the allowable roundness of the pipe bend after the induction bending process is 4%. A relatively large deviation becomes a problem because different internal tensile stresses are generated in the tube wall due to the internal pressure of the medium flowing through the tube bending portion. Especially in the case of high-pressure applications where tubes with such a thick wall thickness are intended, such additional loads arising from roundness are relevant. That is, the wall thickness often has to be selected to be greater than the wall thickness that can be calculated based on the fluid pressure alone due to this geometrical deviation.

  Another disadvantageous effect on the tube in induced bending deformation is that the wall thickness distribution differs between the outer and inner bends. During bending, centered on a neutral zone located on the longitudinal axis of the tube, the tube wall is subjected to tensile stress in the region of the outer bend to be formed. Since the outer bend is longer than the undeformed tube portion, there will necessarily be a reduction in wall thickness. On the other hand, in the inner bent portion, there is a compressive stress at the time of bending, and the wall thickness increases due to the need to shorten the length of the bent portion. However, due to these unavoidable effects, strength calculations for high pressure applications must always be set at the thinnest wall, the outer bend wall. For this reason as well, the wall thickness of the entire tube must be selected to be much thicker than the wall thickness of the straight portion in order to obtain sufficient strength at the tube bending portion.

  An object of the present invention is to reduce a geometric change such as an ellipticity that weakens the strength of a bending portion during deformation and a reduction in wall thickness.

  The solution according to the invention comprises a method for induction bending deformation having the features of claim 1 and an induction bending apparatus for performing the method having the features of claim 8. Provided.

  The method according to the invention is firstly based on forcing an artificial ellipticity on the tube before the start of the deformation process, more particularly on the so-called oblong elliptical shape. “Landscape” means that the major axis of the ellipse corresponding to the shape of the tube cross section is located on the bending plane. Based on the large mass of the tube and the need to position the bending arm in a fixed position, in practice, it is only possible to perform induced bending deformation on a horizontal plane, so that the major axis is simultaneously horizontal To be directed.

  In order to achieve a lateral ellipticity, according to the invention, the tube is operated by the press ram and the opposed support in the pressing device or opposite to each other before heating and thus before entering the deformation zone. It is compressed vertically by two press rams and guided laterally horizontally.

  The compression is preferably carried out with the same degree of roundness as would occur if the pipe was bent at a predetermined bending angle in the same type of pipe in the induced bending deformation method. Particularly preferably, a continuous adaptation of the degree of ellipticity is carried out during the implementation of the pipe bending method, whereby it is initially operated with a relatively small preliminary ellipticity, which preliminary ellipticity is It increases toward the center of. This is because without the pretreatment method according to the present invention, the maximum ellipticity can be generated at the center of the bent portion of the tube.

  Prior to being inserted into the inductor, the cross-sectional shape of the tube is forced as a horizontally long ellipse, so that all ellipticities are removed at the start, center and end of the tube bending process. Note that the start portion is defined as an end portion on the near side when viewed in the feed direction. This results in a tube with a circular cross-section in bending, which has a much smaller tolerance than conventional deformations. According to the present invention, although the ellipticity is artificially formed in advance before the pipe bending process is started, a circular cross section is also obtained at the start part of the pipe bending process. The paradox is in the internal distribution of compressive stress and tensile stress in the tube bending part. These tensions cause ellipticity without the countermeasures according to the present invention, but under the action of the pretreatment according to the present invention, all the actions are compensated for each other by these tensions.

  The second countermeasure means according to the present invention for optimizing the tube geometry in induced bending deformation is an approach that at least shifts the different wall thickness distributions unavoidable in the inner and outer bends. Based on. By shifting the neutral zone to the outside, the wall thickness at the inner bend is increased more strongly by the constant volume law based on the law of nature. However, this does not adversely affect the strength of the tube bend and subsequent workability. What is important is that this measure can reduce the decrease in wall thickness on the outside, i.e., according to the present invention, it is thicker than previously possible when using the same type of tube. The wall thickness can be obtained.

  In the case of a 90 ° tube bend produced by a conventional induction bending method, more particularly, if the usual ratio of bend radius to tube diameter is, for example, 1.5: 1, the wall thickness is reduced. Is at most 25%. According to the invention, this reduction in wall thickness can be substantially reduced, and in particular can be halved. This means that in the case of the method according to the invention, the wall thickness at the outer bend is 12.5% greater than in the prior art. This further means that higher operating loads are possible when the wall thickness of the insertion tube is the same, or even a lower initial wall thickness can be selected when the operating conditions are the same. It means that. This again results in weight and cost savings.

  In accordance with the invention, the neutral zone shift during induced bending deformation of the tube is achieved by heating the tube cross-section differently between the outside of the bend and the inside of the bend. In this case, the outside of the bent portion is not heated more strongly than the inside of the bent portion. The resistance to deformation in the inner bend is less than the resistance to deformation in the outer bend due to the higher temperature, which causes the neutral zone to the outer bend during bending. An intentional shift occurs. That is, the present invention utilizes the deformation temperature interval of the material as desired.

  According to the invention, the deformation process with the changed temperature distribution is performed in a partial region of the bending angle. A transition program is implemented from the starting tangent to the partial region, in which the shift is gradually shifted outward from an initial position that is symmetrical with respect to the center of the tube. A transition program is also applied from the partial area to the end tangent, in which the temperature distribution is again oriented more symmetrically.

  The partial region described above extends over about 80% to 90% of the intended bending angle. In this case, the partial region starts at a bending angle of about 1 ° to 2 ° from the start tangent and ends at about 1 ° to 2 ° before the transition to the end tangent.

The shift of the temperature distribution carried out according to the invention preferably takes place in the ring-shaped inductor located on the bending plane, especially towards the outside, preferably in connection with the adaptation of the power in the induction device, i.e. heating. Based on displacement in relation to changes in output. By displacing the inductor towards the outside, the inductor is placed in the inner tube bend closer to the tube wall than on the outside, whereby here more intense heating is performed. The displacement range is very small, about 5 to 50 mm compared to the diameter of the tube used exceeding 600 mm. In order to heat a thick wall thickness by induction, the distance between the air gap, i.e. the ring-shaped inductor as a conducting current and the peripheral wall of the tube must not be too large. On the other hand, metal contact with the outside of the tube must be avoided under any circumstances. The diameter of the inductor is preferably defined as 1.05D _Rohr plus 25 mm. That is, for a tube with D _Rohr = 1000 mm, the theoretical displacement distance is 75 mm, but in practice only about 50 mm of this is used to achieve a lateral shift of the temperature distribution. I can't.

  Instead of or in addition to locally different heating, it is also possible to implement the desired energy dissipation by local cooling.

  The temperature is measured in a non-contact manner as the surface temperature at the inner and outer bends, and these values are fed to the controller. The temperature distribution can be changed by the controller by increasing the cooling power at the outer bend and / or by increasing the heating power at the inner bend and / or by changing the position of the inductor laterally. Can be updated by.

  In a preferred variant of the method according to the invention, a method is implemented in which the output is controlled simultaneously with the distance control.

  This can affect both the inside of the bend and the outside of the bend as desired. The operator can pre-select which side of the bend should be distance controlled first, and which side of the bend should be output controlled, and the desired surface temperature including the tolerance range. Set. The controller then automatically changes the position of the inductor so that the desired relative distribution is achieved between the inside and outside in the tube bend, and even the absolute deformation temperature is achieved. Adapt the power so that.

  Hereinafter, details of the present invention will be described in more detail with reference to the drawings.

It is the schematic of an induction type pipe bending apparatus. It is a top view of a pipe bending part. FIG. 3 is a cross-sectional view according to the prior art in a transverse plane marked in FIG. 2. FIG. 3 is a sectional view according to the invention in a transverse plane marked in FIG. 2. It is a cross-sectional view which shows different wall thickness distribution in the center of a pipe bending part. It is a longitudinal cross-sectional view which shows different wall thickness distribution in the center of a pipe bending part. It is a figure which shows the press apparatus for preliminary | backup ovalization.

  FIG. 1 shows an induction tube bending apparatus 100. The induction-type pipe bending apparatus 100 includes a machine base 10 that is fixed in position, and a holding device 11 for the pipe 1 is disposed on the machine base 10. The holding device 11 grips the rear end portion of the tube 1 and securely fastens it. Further, the holding device 11 can be displaced in the direction opposite to the machine base 10 in the direction of the tube center axis 2 that also represents the feeding direction. The feeding is performed via the hydraulic unit 12.

  A bending arm 30 is pivotally supported on a vertical bending axis 32. In order to set a desired bend radius, the spacing of the bend axes 32 can be adjusted in a direction perpendicular to the tube center axis 2. A bending clamp 31 is disposed on the bending arm 30, and the bending clamp 31 can grip and clamp the tube 1.

  A cooling device (not shown here) is disposed in the vicinity of the inductor 20 and the thermal action zone. As soon as the corresponding longitudinal part emerges from the deformation zone, the cooling device causes a cooling of the surface temperature, for example with water.

  The induction device includes a ring-shaped inductor 20, and the center of the inductor 20 is positioned in the region of the tube center axis 2.

  The above-described features are also components of a known induction tube bending apparatus, but according to the present invention, in part, the inductor 20 can be moved laterally with respect to the longitudinal axis 2 of the insertion tube 1. In order to do this, a lateral adjustment device 21 is provided.

  On the other hand, a press unit 50 is provided, and in FIG. 7, a preferred embodiment of the press unit 50 is shown in a front view when viewed from the machine base 10 in the feed direction. In the frame 51, at least one hydraulic ram 52, 53 is arranged on the upper and lower sides. Each of the hydraulic rams 52 and 53 is provided with one pressure roller 54 and 55, respectively, and these pressure rollers 54 and 55 have a double cone shape, a rotational hyperboloid shape, or It is the shape of another concave rotationally symmetric body. These shapes achieve a load distribution on two well-spaced lines on the outer circumference of the tube 1 on either side of the tube 1 using only one roller each. This avoids traces of travel on the peripheral wall of the tube due to excessive surface pressure. The hydraulic rams 52 and 53 are adjusted only once to the center located on the tube center axis 2 and are then operated with the same stroke, whereby the pressure rollers 54 and 55 are respectively simultaneously applied to the peripheral wall of the tube. Contact and then cause deformation by the same force. In this way, the tube remains centered on a vertical plane during the entire implementation of the bending process.

  Two other hydraulic rams 56, 57 are attached to the left and right sides of the frame 51, and at least one guide roller 58, 59 is provided at the end of these hydraulic rams 56, 57, respectively. Yes. As a result, the tube 1 is also centered in the horizontal direction so that it is accurately compressed on the central axis 2 by the upper and lower rams 52, 53 having the pressure rollers 54, 55 and so that no eccentricity occurs. The The hydraulic rams 56, 57 on the side only position and hold the guide rollers 58, 59, but no deformation force is applied to the tube by these guide rollers 58, 59. Preferably, the side guide rollers 58, 59 are preferably convex spherical or cylindrical in order to avoid the tube 1 in contact with the guide roller being fixed in the vertical direction due to its shape.

  The above arrangement on the horizontal axis and on the vertical axis is applied to pipe bending performed on a horizontal plane.

  As shown in FIG. 7, the compression is carried out exclusively in the vertical direction so that the cross section of the tube 1 has an elliptical shape, ie the long axis extends in the horizontal direction. The ellipticity is exaggerated for illustration in FIG. 7 and FIG. 3 described below. In practice, the forced roundness is initially only about 1% of the tube diameter in the middle of the tube bend and finally from 1.5% up to 4%, so the roundness is Invisible to the naked eye.

  The frame 51 of the press unit 50 is formed in a ring shape, and more specifically, is formed endless in the sense that the frame 51 itself is closed. The external shape is preferably a rhombus in the plan view, and one of the rams 52, 53, 55, 56 is arranged at each vertex.

  FIG. 2 shows a tube bend 3 having a starting tangent 2 and a tangent 4. In FIG. 2, three different cutting planes AA, BB, and CC are marked, and the cutting plane BB is located at the center of the tube bending portion 3. This is because the deviation between the wall thickness at the inner bending portion and the wall thickness at the outer bending portion is the largest at the center of the tube bending portion 3.

  A cross-section that would occur when using a prior art induction bending method at each location marked in FIG. 2 is shown in FIG. According to this, the cross-section is still circular only in the region AA, ie only in the end tangent 4 in the unmodified insertion tube 1. Due to the deformation process, a so-called vertical ellipticity is formed as a cross-section B-B at the center of the bending part 3, and this vertical ellipticity is laterally long in the region CC, ie in the transition to the starting tangent 2. Result in the formation of an ellipticity of

  On the other hand, by using the induction bending method according to the present invention, a circular shape is formed for all three cross sections AA, BB, and CC as shown in FIG. The

FIG. 5 shows different wall thickness distributions in the tube bending portion 3 in another cross-sectional view taken along the section BB. The wall thickness at the inner tube bending section 3.2 is much thicker than the wall thickness at the outer tube bending section 3.1. The vertical axis 3.3 representing the neutral zone is not located at the center of the cross section of the tube and is shifted in the direction of the outer tube bend 3.1 according to the invention. This is achieved, for example, in the deformation zone by the following temperature profile, which is asymmetrical in the present invention:
Outside the bend 3.1 850 ° C
Inside the bent part 3.2 1000 ° C

  The displacement distance of the inductor at this position is only about 10 mm off the center. In order to realize the effect of the present invention, this small displacement distance is already sufficient compared to other geometric dimensions.

  FIG. 6 shows the wall thickness distribution in the vertical cross-sectional view of the tube bending portion 3 in the horizontal direction. The middle two-dot chain line represents the tube center axis 2. Parallel to this, the neutral zone 3.3 extends. The dashed lines in the region of the inner tube bending section 3.2 and the outer tube bending section 3.1 represent the wall thickness in the undeformed tube 1. The solid line indicates the wall thickness that occurs after the bending deformation is performed. Also in this figure, the deviation is exaggerated.

The following is an example of wall thickness distribution in an insertion tube with a nominal wall thickness of 10 mm:
a) Induction bending deformation according to the prior art:
Outside bend 3.1 7.5mm (-25%)
Inside the bent part 3.2 15.0mm (+ 50%)
Change in inner diameter of tube (necking): -1.25 mm
b) Inductive bending deformation according to the invention:
With a suitably adapted temperature, it is possible to shift the neutral zone 3.3 inward or outward. Basically, in the method according to the invention, an outward shift is sought to halve the attenuation.
Outside of bent part 3.1 8.75mm (-12.5%)
Inside the bent part 3.2 17.50mm (+ 75%)
Change in inner diameter of tube (necking): about -3.125 mm

  In this way, the thinning of the outer side 3.1 of the bent part is halved. At the same time, the increase in wall thickness at the inside 3.2 of the bend will slightly reduce the inner diameter, but the resulting decrease in internal cross section of about 2 mm will result in a larger diameter of the tube used. In view of this, it is negligible.

Another disadvantageous effect on the tube in induced bending deformation is that the wall thickness distribution differs between the outer and inner bends. During bending, centered on a neutral zone located on the longitudinal axis of the tube, the tube wall is subjected to tensile stress in the region of the outer bend to be formed. Since the outer bend is longer than the undeformed tube portion, there will necessarily be a reduction in wall thickness. On the other hand, in the inner bent portion, there is a compressive stress at the time of bending, and the wall thickness increases due to the need to shorten the length of the bent portion. However, due to these unavoidable effects, strength calculations for high pressure applications must always be set at the thinnest wall, the outer bend wall. For this reason as well, the wall thickness of the entire tube must be selected to be much thicker than the wall thickness of the straight portion in order to obtain sufficient strength at the tube bending portion.
EP 2471609 (EP 2471 609 A1) also discloses a method and apparatus for bending a tube having a thick wall thickness. However, the method disclosed therein is not specifically directed to a tube having a circular cross-section and the problems associated with reduced ellipticity and wall thickness that occur in this case.

Claims (11)

In particular, a method of inductively bending and deforming a pressure-resistant pipe (1) having a thick wall thickness and a large diameter in a power plant pipe and a pipeline pipe,
Supporting the untreated tube (1) in a horizontal direction;
Sending the tube (1) until the front tube section passes through the ring inductor (20) of the electrical induction device;
In a bending clamp (31) supported on a bending arm (30) pivotable about a vertical axis of rotation (32) arranged laterally of the tube (1), the front tube A step of sandwiching the part;
Applying a current to the induction device to heat the tube section;
Displacing the bending arm (30) by feeding the tube (1) longitudinally until the tube bending section (3) is completed;
In a method having at least
The tube (1) is compressed in the vertical direction in the press unit (50) before being inserted into the inductor (20), and the press unit (50) has an oblong shape that is horizontally long with respect to the tube (1). Force the cross section,
Compare the temperature distribution on the outside (3.2) of the bend by displacing the inductor (20) relative to the tube (1) at least during part of the tube bending process. And adjusting the temperature distribution inside the bend (3.1) to a relatively high temperature.   The method according to claim 1, wherein the tube (1) is continuously compressed while being sent in the longitudinal direction. Compressing the tube (1) continuously while feeding in the longitudinal direction;
The degree of compression is further increased from the start tangent (2) of the tube bend (3) towards the center and reduced again from the center towards the end tangent (4). Method.   The method according to claim 1, wherein the temperature distribution is adjusted by locally increasing the energy supply on one side (3.1, 3.2) of the bend. While reducing the interval between the inductor (20) and the inside of the bent portion (3.2), simultaneously increasing the interval between the inductor (20) and the outside of the bent portion (3.1),
Method according to claim 4, wherein the absolute temperature level is controlled by adaptation of the current flowing in the inductor (20).   The method according to claim 1, wherein the temperature distribution is adjusted by locally increasing the energy dissipation on one side (3.1, 3.2) of the bend. The temperature inside the bent part (3.2) is lowered by a cooling device,
The method of claim 6, wherein the absolute temperature level is controlled by adaptation of the current flowing through the inductor (20). Pressure-resistant pipe (1) having a thick wall thickness and a large diameter, in particular an induction pipe bending apparatus (100) for power plant pipes and pipeline pipes,
A machine base (10) for supporting the untreated pipe (1) in a horizontal direction;
A feed unit (11) acting in the longitudinal direction of the tube axis;
An electrical induction device having a ring-shaped inductor (20) for heating the tube section;
A bending arm (30) pivotable about a vertical rotation axis (32), a bending clamp (31) for sandwiching the tube (1), the rotation axis (32) and the bending A bending arm (30) having an adjusting device for adjusting the distance between the clamp (31), and
In an induction tube bending apparatus (100), including at least
A press unit (50) is arranged in front of the inductor (20) when viewed in the feed direction, and the press unit (50) has at least one ram acting in a direction perpendicular to the tube (1). (52) and at least one opposing support portion (53),
The inductor (20) is supported so as to be displaceable in a direction transverse to the feeding direction, and the power of the induction device can be controlled by a control unit based on a lateral displacement of the inductor (20). An inductive pipe bending apparatus (100), characterized in that it is vice versa or vice versa.   The induction tube bending apparatus according to claim 8, wherein the pressing unit (50) has at least two hydraulically driven rams (52, 53) acting in opposite directions on the tube.   The ram and the opposing support, or the rams (52, 53) acting in opposite directions, each have at least one pressure roller (54, 55) having the shape of a double cone or a rotating hyperboloid. The induction type pipe bending apparatus according to 8 or 9. The ram and the opposing support portion, or the two rams (52, 53) are arranged above and below a closed frame (51),
The induction type pipe bending apparatus according to any one of claims 8 to 10, wherein at least one lateral guide roller (58, 59) is arranged on each side of the frame (51).

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