EP0467755A1 - Device for antivibrationally securing tubes of a heat exchanger - Google Patents

Abstract

The antivibrational bars are arranged as a plurality of sets of at least two bars (18a, 18b), in which the external ends of the bars are aligned according to an axis (22). The external end parts of the antivibrational bars (18a, 18b) comprise aligned through-openings (23, 24). The opening (24) is threaded. The ends of the bars (18a, 18b) are connected by a pin (20) having a threaded part (20a) at one of its ends and a screwing and unscrewing head (20b) at its other end. The pin (20) is introduced into the aligned openings (23, 24) and into the bore of a tubular distance piece (21) interposed between the antivibrational bars (18a, 18b). After screwing into the threaded opening (24), the pin (20) is rotationally locked by a locking means (25). <IMAGE>

Description

The invention relates to an anti-vibration wedging device for tubes of a heat exchanger, such as a steam generator.

The steam generators, in particular the steam generators of nuclear pressurized water reactors, comprise tubes bent in U having two branches crimped at their ends in a tubular plate. The tubes are arranged in adjacent flat layers. The curved parts of the bundle tubes which are juxtaposed at its upper part have radii of curvature different from each other and are placed adjacent to form a structure of substantially hemispherical shape called a bun.

During operation of the steam generator, high temperature pressurized water flows through the bundle tubes and potable water is brought into contact with the outer surface of these tubes, along which it moves in the direction vertical by heating and then vaporizing, to come out in the form of vapor at the top of the generator.

The circulation of the fluid in contact with the tubes can cause vibrations which are liable to cause damage to these tubes if they are not maintained effectively.

The right part of the tubes is engaged in spacers located at regular distances from each other according to the height of the beam. These straight parts are therefore effectively maintained by rigid elements. The curved parts of the tubes of the bundle constituting the bun must also be maintained and generally used for this are spacer bars which are interposed each between two plies of adjacent tubes of the bundle and arranged in substantially radial directions of the bun. These spacer bars are generally connected two by two in an articulated manner at one of their ends arranged towards the inside of the bun and placed in an angular manner to form V-shaped structures.

The outer ends of the antivibration bars opposite their articulated ends project from the tubes constituting the outer layer of the bun and are interconnected by connecting means ensuring the maintenance of the antivibration bars.

Various means of connecting the outer ends of the antivibration bars have been proposed using fastening elements placed on the upper surface of the bun.

For example, it has been proposed to weld the ends of the anti-vibration bars on curved elements arranged along meridian planes of the bun.

It has also been proposed to fix the ends of the anti-vibration bars, for example by welding, on substantially parallel rings resting on the upper surface of the bun. In all cases, the fixing of the anti-vibration bars requires complex operations, most often using welds which must be carried out in the vicinity of the tubes of the bundle, which thus risk being subjected to certain deteriorations. In addition, the materials constituting the anti-vibration bars must be chosen to allow their welding and possibly their treatment after welding, in good metallurgical conditions.

Mechanical connection devices have also been proposed making it possible to connect the outer ends of the anti-vibration bars to pieces of fasteners such as retaining rings resting on the outer surface of the bun.

These devices are relatively complex and require for their fixing the use of heavy and bulky complementary elements attached to the bun. In addition, these devices do not make it possible to ensure very good alignment of the anti-vibration bars and to precisely regulate the play existing between two successive anti-vibration bars between which a sheet of tubes is interposed.

The object of the invention is therefore to propose a device for anti-vibration wedging of tubes of a steam generator comprising a bundle of tubes bent in a U fixed at their ends in a tubular plate, arranged in adjacent layers and whose curved parts opposite the tubular plate and juxtaposed constitute a set of substantially hemispherical shape called a bun, the wedging device comprising a set of anti-vibration bars each interposed between the curved portions of two adjacent plies of bundle tubes and arranged in a substantially radial direction of the bun , so as to have one end outside the bun and a set of connecting means between the outer end parts of the anti-vibration bars, this wedging device having a small footprint, which can be placed very quickly and very easily, too good in the case of a new fa generator briquetted in the factory than in the case of a used steam generator during maintenance and repair and allowing to ensure a very good alignment and a precise adjustment of the spacing of the anti-vibration bars.

For this purpose, the outer ends of the anti-vibration bars arranged in a plurality of sets of at least two bars in which the bars are aligned have aligned through openings, one of which is threaded, a means of connecting the ends of the anti-vibration bars is associated with each of the sets of bars and each of the connecting means is constituted by a pin having a threaded portion at the one of its ends and one end opposite to the threaded part constituting a screwing and unscrewing head and at least one spacer of tubular shape whose length corresponds substantially to the diameter of the tubes of a sheet, the pin being inserted into the aligned openings of a set of anti-vibration bars and in the bore of at least one spacer interposed between two anti-vibration bars, screwed into the threaded opening and blocked by a rotation blocking means.

In order to clearly understand the invention, we will now describe, by way of nonlimiting example, with reference to the attached figures, an embodiment of a wedging device according to the invention used in the case of '' a steam generator of a pressurized water nuclear reactor.

Figure 1 is an elevational view in partial section of a steam generator of a pressurized water nuclear reactor comprising anti-vibration bars for holding the tubes of the bundle.

Figure 2 is a sectional view of a wedging device according to the invention, in its part located above the bun of the steam generator.

FIG. 3 is a view along 3 of FIG. 2.

Figure 4 and a view similar to the view of Figure 3 relating to a first alternative embodiment of a wedging device according to the invention.

Figure 5 is a view similar to the view of Figure 3 on a second alternative embodiment of a timing device according to the invention.

In Figure 1, we see a steam generator of a pressurized water nuclear reactor generally designated by the reference 1 and having an outer casing 2 connected, at its lower part, to a tubular plate 3 of great thickness.

The casing 2 contains the bundle of tubes of the steam generator constituted by tubes 5 bent in a U and comprising at their upper part, semi-circular hangers constituting the bun of the steam generator.

The straight parts 5a of the bundle tubes are crimped at their ends in the tube plate 3, so as to open into a water box 7 in two parts separated by a partition 8.

The pressurized water from the nuclear reactor enters one of the parts of the water box 7 through an inlet pipe 6a, flows through the tubes of the bundle then exits through an outlet pipe 6b.

The bundle of tubes 5 is surrounded by a bundle envelope 9 making it possible to channel the feed water entering the envelope of the steam generator by an inlet pipe 11. The feed water of the steam generator circulates first from top to bottom in the annular space located around the bundle envelope 9, then from bottom to top in contact with the tubes 5 of the bundle so as to heat up then to vaporize and to come out in the form steam through the upper tube 12 of the steam generator.

The upper part of the bundle of tubes called a bun is formed by the juxtaposition of semicircular hangers arranged in successive layers in which the radii of the hangers are decreasing from the outside to the inside of the beam.

In addition, the various successive layers of tubes of the bundle parallel to the central layer shown in FIG. 1 comprise external hangers of decreasing diameters, so that the upper part of the bundle or bun constitutes a substantially hemispherical assembly.

The straight part 5a of the tubes 5 is held by spacer plates 10 which prevent the tubes from vibrating when the steam generator is in operation, under the effect of the circulation of exchange fluids.

The curved parts of the tubes situated at the upper end of the bundle are held by anti-vibration bars 15 formed in the form of compasses articulated at their inner end 15a and introduced between the layers of successive tubes, at the level of the hangers.

The outer ends 15b of the branches of the anti-vibration bars project from the upper surface of the bun and allow the fixing of the anti-vibration bars.

Subsequently, any branch of an assembly 15 in the form of a compass will be designated by anti-vibration bars.

In Figure 2, there is shown a section of the curved part of two tubes 16a and 16b of the bundle of the steam generator arranged in two adjacent layers and placed at the outer part of these layers. The external tubes such as 16a and 16b of the successive layers of the bundle of the steam generator define the external surface of the hemispherical bun.

Also shown in Figure 2 and in Figure 3, an element 17 of a device anti-vibration wedging according to the invention disposed in the bun of the steam generator.

The element 17 of the wedging device comprises a first anti-vibration bar 18a interposed between the sheet of tubes in which the tube 16a is placed and an adjacent sheet of tubes, a second anti-vibration bar 18b interposed between the sheet of tubes in which the tube is placed tube 16a and the adjacent ply of tubes in which the tube 16b is placed, a connecting pin 20 and a spacer 21.

The anti-vibration bars 18a and 18b are placed in positions aligned along an axis 22 perpendicular to the axis of the tubes 16a and 16b.

According to the invention, the end portions of the antivibration bars 18a and 18b remaining projecting outside the bun, that is to say relative to the tubes 16a and 16b, after their positioning in the bun, are crossed by cylindrical openings 23 and 24 having for axis the alignment axis 22 of the two anti-vibration bars 18a and 18b.

The opening 23 is a smooth cylindrical opening while the opening 24 is tapped, so as to allow the screwing of a threaded part 20a of the spindle 20.

The end of the spindle 20 opposite its threaded end 20a constitutes a head 20b, the section of which can be, for example, of hexagonal shape. The head 20b allows the screwing and unscrewing of the spindle 20 to be carried out, using an appropriate tool.

The spacer 21 has a tubular shape, the bore of this spacer having a diameter substantially equal to the diameter of the openings 23 and 24.

A plate 25 cut from a steel sheet or strip is fixed by a peripheral weld line 26 to the outer surface of the spacer. 21. The welding of the plate 25 on the spacer 21 can be carried out by the TIG method.

The length in the axial direction of the spacer 21 is equal to the average diameter of the tubes constituting the sheet in which the tube 16a is placed.

To carry out the installation and assembly of the element 17 of the anti-vibration wedging device according to the invention, firstly, as in the prior art, the establishment of the anti-vibration bars 18a and 18b in the steam generator bun. The ends of the anti-vibration bars 18a and 18b having the openings 23 and 24 remain protruding outside the bun of the steam generator, after the establishment of the anti-vibration bars.

The anti-vibration bars 18a and 18b and in particular their projecting end parts are placed in alignment with one another, in the direction 22 perpendicular to the axis of the tubes 16a and 16b.

The openings 23 and 24 are then aligned, so that the axis 22 constitutes their common axis. The spacer 21 is interposed between the anti-vibration bars 18a and 18b, the bore of this tubular spacer being placed in alignment with the openings 23 and 24.

The stop plate 25, folded at 90 °, has a folded part 25a crossed by an opening 25b which is placed in alignment with the opening 23.

The pin 20 is introduced into the openings 25b and 23 and into the bore of the spacer 21 and then screwed inside the threaded opening 24 of the spacer 18b, using a clamping tool.

The pin 20 provides the connection between the end parts of the anti-vibration bars 18a and 18b and the tightening of these anti-vibration bars on the end surfaces of the spacer 21 whose length corresponds to the average diameter of the tubes of the sheet comprising the tube 16a. The spacing of the antivibration bars 18a and 18b is thus fixed at a value making it possible to optimize the conditions of the antivibration setting of the tubes of the sheet comprising the tube 16a.

After tightening the spindle 20, it can be secured against rotation by folding the end of the part 25a of the plate 25 above the head 20b of the spindle, as indicated by the arrow 27. In this way, the spindle 20 is not liable to loosen and the connecting elements of the anti-vibration bars 18a and 18b are not liable to come off, under the effect of vibrations, in the steam generator in service.

It is obvious that the ends of the various anti-vibration bars introduced into the bun of the steam generator can be connected two by two by devices such as the device 17 shown in FIGS. 2 and 3.

The whole anti-vibration wedging device of the bundle tubes arranged in the bun is thus perfectly held in place and ensures effective wedging of the various plies of tubes in their curved part.

In Figure 4, we see a set of anti-vibration bars 28a, 28b, 28c, 28d and 28e aligned in a direction 32 perpendicular to the axes of the tubes 29a, 29b, 29c and 29d constituting successive layers of tubes interposed between the anti-vibration bars.

The anti-vibration bars aligned 28a to 28e have a projecting part relative to the tubes 29a, 29b, ..., located furthest outside in the layers of successive tubes.

In these projecting parts, the anti-vibration bars 28a, ..., 28e are crossed by openings having the axis 32 as their common axis.

The aligned openings passing through the anti-vibration bars are formed by smooth holes, with the exception of the opening passing through the last anti-vibration bar in the row (the bar 28e in FIG. 4) which is constituted by a tapped hole.

After their installation in the bun of the steam generator, the anti-vibration bars 28a, ..., 28e are interconnected by their projecting end part, by means of a pin 30 inserted inside the aligned openings of the bars anti-vibration and inside the bores of the spacers 31a, 31b, 31c and 31d arranged between the successive anti-vibration bars 28a, ..., 28e.

The pin 30 has a threaded end which is screwed inside the tapped hole of the anti-vibration bar 28e, so as to ensure the connection between the anti-vibration bars and the tightening of these anti-vibration bars against the spacers. The spindle 30 has a head 30b making it possible to screw or even unscrew the spindle 30.

The spacers 31a, 31b, 31c and 31d have a length in the axial direction 32 equal to the average diameter of the tubes, respectively 29a, 29b, 29c, 29d constituting the plies of successive tubes maintained by the spacers 28a, ..., 28e.

In this way, a perfect alignment of a row of anti-vibration bars is carried out in a single operation and a positioning of these anti-vibration bars on either side of the plies of tubes, with a spacing ensuring optimized wedging of the tubes.

The blocking in rotation of the spindle 30 can be carried out in an identical manner to the blocking of the spindle 20 shown in FIG. 2. The spacer 31a located closest to the head 30b of the spindle 30 comprises a stop plate welded on its external surface, this plate being folded after tightening of the spindle on the head 30b.

In Figure 5, there is shown a second alternative embodiment of elements of a wedging device according to the invention.

The ends of the antivibration bars 33a, 33b and 33c projecting from the tubes 34a and 34b located outside of successive layers of tubes are in offset positions, due to the relative arrangement of the tubes 34a and 34b of the two successive layers.

The outer tube 34a of the first ply has a radius of curvature at its arch less than the radius of curvature of the curved part of the tube 34b, these differences in radius of curvature resulting from the geometry of the bun of the steam generator.

As a result, the projecting part of the anti-vibration bar 33a is set back relative to the projecting parts of the anti-vibration bars 33b and 33c.

In this case, the outer end parts of the antivibration bars 33a, 33b and 33c can be connected by connecting devices 35a and 35b similar to the devices 17 shown in FIGS. 2 and 3.

The anti-vibration bar 33a is traversed by a smooth opening and the bar 33b by a tapped opening, these openings having a common axis 36a. The device 35a comprising a pin 38 and a spacer 37 makes it possible to make the connection between the end parts of the bars 33a and 33b aligned in the direction of the axis 36a.

The bar 33b is also crossed by a smooth opening, in its part located towards the outside, relative to the tapped opening aligned along the axis 36a.

The bar 33c is pierced with a tapped opening having the axis 36b as a common axis with the smooth opening passing through the bar 33b. The device 35b comprising a pin and a spacer makes it possible to ensure the connection between the bars 33b and 33c.

The wedging device according to the invention has the advantage of making the connection between the antivibration bars inserted between the layers of tubes inside the bun of the steam generator, without requiring welding. Any suitable material can therefore be used to form the anti-vibration bars which are not affected by the welding operations.

It is possible to very precisely adjust the spacing between the anti-vibration bars placed on either side of a sheet of tubes, this spacing being fixed at a value corresponding to the average diameter of the tubes in the sheet considered. In fact, this mean diameter of the tubes in a layer of the bundle of a steam generator is liable to vary, so that the use of spacers of variable length makes it possible to optimize the spacing of the anti-vibration bars. In addition, the device according to the invention makes it possible to ensure very good alignment of the anti-vibration bars arranged in a row, thanks to the use of a connecting element constituted by a pin introduced into aligned openings of the anti-vibration bars.

The device according to the invention comprises connecting elements between the antivibration bars whose volume is relatively small.

Finally, the device according to the invention makes it possible to wedge the tubes with a spacing between the anti-vibration bars maintained at a fixed value.

The invention is not limited to the embodiments which have been described.

Thus, depending on the arrangement of the antivibration bars and their number, it is possible to envisage the use of very long pins ensuring the connection between the end portions of a large number of antivibration bars.

One can use a blocking and retaining means of the spindle different from a stop plate welded on the spacer located in the vicinity of the screwing and unscrewing head of this spindle.

Finally, the anti-vibration wedging device according to the invention can be used in the case of any heat exchanger comprising bent tubes arranged in sheets that are parallel to each other.

Claims (5)

1.- Anti-vibration wedging device for tubes of a heat exchanger comprising a bundle of tubes bent in a U, fixed at their ends in a tubular plate, arranged in parallel layers and whose curved parts opposite to the tube plate and juxtaposed constitute a substantially hemispherical assembly called a bun, the wedging device comprising a set of anti-vibration bars (18a, 18b, 28a, ..., 28e, 33a, 33b, 33c) each interposed between the curved portions of two adjacent plies of tubes (16a, 16b, 29a, ..., 29d, 34a, 34b) of the bundle and arranged in a substantially radial direction of the bun, so as to present an end outside the bun and a set of connecting means between the outer end parts of the anti-vibration bars, characterized in that the outer ends of the anti-vibration bars (18a, 18b, 29a, ..., 29d, 33a, 33b, 33c) have according to a plurality of sets of at least two bars in which the bars are aligned have aligned through openings (23, 24), one of which is threaded, that a means for connecting the ends of the anti-vibration bars is associated with each of the sets of bars and that each of the connecting means is constituted by a pin (20, 30) having a threaded part (20a) at one of its ends and an end opposite to the threaded part (20a) constituting a head screwing and unscrewing (20b) and at least one spacer (21, 31a, ..., 31d, 37) of tubular shape whose length substantially corresponds to the average diameter of the tubes (16a, 29a, ..., 29d, 34a) of a sheet of tubes, the spindle (20, 30, 38) being introduced into the aligned openings of a set of anti-vibration bars and into the bore of at least one spacer inserted between two anti-vibration bars, screwed into the threaded opening and blocked by an anti-rotation locking means (25). 2.- Device according to claim 1, characterized in that the anti-rotation locking means of the spindle (20) consists of a sheet metal plate (25) welded to the external surface of a spacer (21) located at neighborhood of the head (25b) for screwing and unscrewing the spindle (20) comprising a part (25a) through which an opening (25b) in which the spindle (20) is engaged, capable of being folded down on the head screwing and unscrewing (20b) of the spindle (20). 3.- Device according to any one of claims 1 and 2, characterized in that at least one of the connecting means comprises at least two spacers (31a, ..., 31d) each interposed between two successive anti-vibration bars (28a, ..., 28e), the spacers (31a, ..., 31d) having different lengths corresponding to the average diameter of the tubes in the plies of tubes (29a, ..., 29d) between which the anti-vibration bars (28a, ..., 28e). 4.- Device according to any one of claims 1 and 2, in the case where the anti-vibration bars (33a, 33b, 33c) have outer ends offset in the radial direction of the bun, characterized in that the connecting means (35a, 35b) are arranged on the corresponding anti-vibration bars (33a, 33b, 33c), in positions offset in the radial direction of the bun. 5.- Device according to claim 1, in the case where at least one of the sets of anti-vibration bars comprises a plurality of bars (28a, 28b, 28c, 28d, 28e) aligned in a direction (32) characterized by the fact that the anti-vibration bars (28a, ..., 28e) constituting the assembly are crossed by aligned smooth openings having the axis (32) as a common axis, with the exception of one of the anti-vibration bars (28e) disposed at the end of the set of aligned bars (28a, ..., 28e) which is crossed by a tapped opening.

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