EP0186536B1 - Apparatus for removing sludge for a cleaning installation of a steam generator tube sheet, and steam generator having such an apparatus - Google Patents

Description

The present invention relates to sludge removal devices for installation for cleaning the steam generator tubular plate comprising, in a cylindrical enclosure closed by the plate, a bundle of parallel tubes connected to the plate, traversed by a primary fluid to high temperature, devices of the type comprising at least one insertable liquid supply and sludge suction assembly.

The invention relates more particularly to the removal devices making it possible to organize, on the plate, a circulation of cleaning liquid by injection of a cleaning liquid, generally water, at the periphery of the plate and under almost incidence grazing and by suction of the water which collects at the periphery of the plate.

The installation generally comprises, in addition to the device, at least one lance which can be moved radially between two adjacent plies of tubes, parallel to and near the tubular plate, the lance having a terminal part provided with nozzles directing oblique jets towards the tube plate.

Numerous devices of the type defined above are already known. The document FR-A-2,352,269 describes for example a device which comprises two assemblies which are inserted into the enclosure through a closable hole in the latter. Each assembly consists of two symmetrically and tangentially directed inlet nozzles and two outlet nozzles. Two circumferential flows are thus produced in a semicircle at the periphery of the tube plate. However, this device has significant drawbacks. In particular, the nozzles are introduced through the envelope through the same hole as a lance or lances for attacking deposits on the plate. The assembly therefore represents a space requirement such that it can only be inserted through a hole of large diameter. However, such access holes are only found on certain steam generators and, moreover, these holes are generally placed very above the tube plate, which considerably complicates the production and installation of the device. The document FR-A-2,514,108 describes for its part an installation in which the sludge removal device and the lances are not introduced into the envelope by different holes, which considerably simplifies the construction. However, the removal device according to this document also comprises elements for injecting cleaning liquid and suction elements which constitute separate assemblies which have to be inserted separately, which increases the duration and the complexity of the setting-up operations. place and removal.

The present invention aims in particular to provide a device for eliminating sludge for installations for cleaning tubular plates which respond better than those previously known to the requirements of practice, in particular in that it is of simple structure and easy to put in place, and guarantees a good sweeping of the sludges suspended by attack lances of the layer of mud which has gradually formed and hardened during the operation of the generator.

To this end, the invention provides a device of the type defined above, in accordance with the characterizing part of claim 1.

In practice, the pipe can be maintained in the pipe, in its current part, by perforated centralizers distributed along the pipe.

The pipe is advantageously provided with a tight fixing flange on the access hole provided in the envelope. On certain steam generators, comprising a small hole, called an "eye hole", placed in the immediate vicinity of the plate, it will be possible to use a pipe having a rigid end portion and whose permanent curvature is sufficiently high so that this end portion can be engaged through an eye hole until it comes in close proximity to the tube plate, without it abutting against the exchange tubes placed at the periphery of the bundle. In other cases, the thickness of the envelope, the free distance between the beam and the envelope and / or the dimension of the access hole will be such that it will be necessary to constitute the terminal section of the pipe by a flexible. This can have the high radius of curvature required for the introduction, then flex so as to ensure good contact between the outlet of the pipe and the plate at the end of insertion of the pipe. In practice, this flexible section may consist of a bellows.

The invention is applicable whatever the mesh of the distribution network of the exchange tube in the bundle. In particular, the device is adaptable to an exchanger whose tubes are distributed in a square network and it can then in particular cooperate with slurry attack lances of the kind described in the document FR-A-2,514,108 already mentioned. The device can also be used in a heat exchanger where the tubes are distributed in a triangular network. In this case, it will advantageously be associated with a lance or spears for attacking the sludge in the three directions of the mesh of the network.

• - la figure 1 est une vue en coupe verticale de la partie basse d'un générateur de vapeur, montrant les constituants principaux que l'on retrouve dans la majorité des générateurs de vapeur,
• - la figure 2 montre l'un des ensembles de circulation et d'aspiration destinés à constituer un dispositif d'enlèvement des boues utilisables dans un générateur de vapeur du genre montré en figure 1,
• - la figure 3 est une vue de détail, en coupe suivant la ligne III-III de la figure 2,
• - la figure 4 est une vue schématique en perspective montrant l'ensemble de la figure 2 isolée,
• - la figure 5, similaire à la figure 2, montre une variante de réalisation,
• - la figure 6, similaire à la figure 2, montre un ensemble d'aspiration utilisable dans un dispositif d'élimination des boues constituant une autre variante encore,
• - les figures 7 et 8 sont des vues schématiques, respectivement depuis le dessus et en coupe suivant un plan vertical, montrant la disposition relative d'un ensemble suivant la figure 5 et de lances d'injection,
• - la figure 9 est un schéma montrant les diverses zones de la plaque tubulaire à attaquer à la lance dans le cas d'un réseau de tubes d'échange à maille triangulaire,
• - la figure 10 est une vue schématique, en demi-coupe de la tête d'injection d'une lance d'attaque des boues, permettant d'obtenir les trois directions d'attaque indiquées sur la figure 9,
• - les figures 10A, 10B, 10C et 10D sont des schémas en coupe suivant les plans A, B, C et D de la figure 10,
• - la figure 11, similaire à la figure 8, montre la mise en oeuvre de la lance de la figure 10,
• - la figure 12, similaire à la figure 7, montre une réalisation possible du dispositif dans le cas d'un réseau à maille triangulaire.
• - Avant de décrire l'invention, il peut être utile de rappeler brièvement la constitution des parties concernées par l'invention d'un générateur de vapeur pour réacteur refroidi et modéré à l'eau légère.

The invention will be better understood on reading the following description of particular embodiments, given by way of nonlimiting examples. the description refers to the accompanying drawings, in which:

• FIG. 1 is a vertical sectional view of the lower part of a steam generator, showing the main components found in the majority of steam generators,
• FIG. 2 shows one of the circulation and suction assemblies intended to constitute a sludge removal device usable in a steam generator of the kind shown in FIG. 1,
• FIG. 3 is a detail view, in section along the line III-III in FIG. 2,
• FIG. 4 is a schematic perspective view showing the assembly of FIG. 2 isolated,
• FIG. 5, similar to FIG. 2, shows an alternative embodiment,
• FIG. 6, similar to FIG. 2, shows a suction assembly usable in a sludge removal device constituting yet another variant,
• FIGS. 7 and 8 are schematic views, respectively from above and in section along a vertical plane, showing the relative arrangement of an assembly according to FIG. 5 and of injection lances,
• FIG. 9 is a diagram showing the various zones of the tube plate to be attacked with the lance in the case of a network of exchange tubes with triangular mesh,
• FIG. 10 is a diagrammatic view, in half-section of the injection head of a sludge attack lance, making it possible to obtain the three directions of attack indicated in FIG. 9,
• FIGS. 10A, 10B, 10C and 10D are diagrams in section along the planes A, B, C and D of FIG. 10,
• FIG. 11, similar to FIG. 8, shows the implementation of the lance of FIG. 10,
• - Figure 12, similar to Figure 7, shows a possible embodiment of the device in the case of a triangular mesh network.
• - Before describing the invention, it may be useful to recall briefly the constitution of the parts concerned by the invention of a steam generator for a reactor cooled and moderated with light water.

The steam generator shown in FIG. 1 comprises a pressure enclosure of cylindrical shape 1 closed at its lower part by a tubular plate 2 in which are terminated and welded the end parts of U-shaped heat exchange tubes, such as tube 7 The enclosure is extended, under the plate 2, by a dome delimiting a water box 3, separated by a vertical partition 4 into a compartment where the hot primary water coming from the reactor arrives by a pipe and an outlet compartment d '' where the primary water escapes to the reactor through a tube 6. Between the two compartments the primary water circulates in the U-shaped tubes.

Between the bundle of U-shaped tubes 7 and the enclosure 1 is placed a secondary envelope 8. The secondary envelope 8 ends above the tubular plate, leaving a space allowing the secondary water and the water. of recirculation which descend through the annular space between the enclosure and the envelope to supply the area occupied by the beam, immediately above the tube plate. A distribution plate 11 comprising a central opening 12 is disposed above the tubular plate 2. The hot and cold branches of the tubes 7 are separated by a free diametrical zone 13, called “water street where spacers 14 are placed and a continuous purge ramp 15.

The insertion of the plate cleaning tools can only be done through holes in the enclosure. The enclosure 1 shown has two relatively large diameter holes 17 called “fist holes” located opposite the “water street” and at the level of the distribution plate 11. Two smaller holes, usually called “ eye ", are aligned in a direction perpendicular to that of the" fist holes "at a short distance from the tube plate 2. Often, two" eye holes "1 ₆ are also provided below the" fist holes ". The holes 17 and 16, closed in normal operation by taps, correspond to openings made in the casing 8. In general the enclosure 1 is surrounded by a casemate (not shown) whose role is in particular to stop the parts and projected debris in the event of an incident.

Not all steam generators have both "fist holes" and "eye holes". But there are always at least one or the other of these types of holes.

To remove the sludge which accumulates on the tube plate 2, an installation is generally used having on the one hand means for attacking the layer of mud, comprising at least one lance insertable into the enclosure, and on the other share a removal device. The latter comprises several organs insertable into the enclosure through the "eye holes" or the "fist holes".

The insertable assembly shown in Figures 2 to 4 is intended to be introduced into the enclosure 1 through an "eye hole" 16 located 90 ° from the water street. This assembly 18 consists of a suction pipe 20 provided with a flange 22 intended to be applied in a sealed manner on the enclosure, around the "eye hole", in replacement of the shutter tape. The rear part of this pipe is provided with a. suction connection 24 intended to be connected via a hose 26 to a suction pump (not shown). The end portion 28 of the pipe 20 insertable into the enclosure has a shape such that at the same time it can be introduced without jamming against the bore of the "eye hole" or coming into abutment against the exchange tubes and, when it is in place, it bears against the tubular plate 2. The end of the pipe 20 is advantageously swollen and provided with terminal fingers 30 such that the outlet of the pipe is slightly immersed in the layer of water which will cover the peripheral part of the plate during operation.

The assembly 18 also comprises means for circulating the water on the plate, comprising a rigid pipe 32 held coaxially with the pipe by perforated centralizers not shown. The rear part piping 32 protrudes from the pipe and is provided with a nozzle 34 for connection to a hose for supplying water under high pressure (300 bars for example). The downstream end of the piping 32 opens into a nozzle or water spray head 36 which may have the constitution shown in FIG. 3. This nozzle is provided with a nozzle 38 for forming a jet directed approximately perpendicularly to the nozzle, in the circumferential direction of the enclosure. The jet emitted must be under grazing incidence. In practice an angle of about 80 ^* on the vertical will generally be appropriate.

As a general rule, two sets of the type shown in FIGS. 2 to 4 will be inserted by “opposite eye holes in the enclosure, the nozzles being oriented so as to cooperate in order to organize a circumferential circulation in the same direction over the entire periphery of the plaque. Figures 7 and 8 show an installation comprising a device for removing sludge with two assemblies 18 connected to a hydraulic system which can be carried by a vehicle so as to be transportable as a block from one steam generator to another.

This system can also carry the water supply system under pressure of lances 40. FIG. 7 shows the use of two lances introduced by “eye holes” 16 placed in the water street. Each of these lances is movable along its axis by a servo motor assembly 42 fixed on a “hole in the eye” flange. Each of these servo motors is controlled, from the system, in synchronism with the water supply to the lances, so that there is a sequence of sending jets in each of the ligaments (intertubular spaces) of the tube bundle 7. The lances can have one of the constitutions described in the patent applications already mentioned. They can be composed of a head and tubular sections connectable to each other, quick assembly and disassembly. Several succession heads can be used, comprising jets for sending water jets with increasingly small impact angles, way to sweep the entire tubular plate. FIG. 8 shows, for example, the case where shots are fired at angles ranging from 25 'to 85 "in succession.

If the enclosure also has "fist holes", the installation can be completed by additional suction pipes introduced through these holes. It is not necessary to describe here the operation of the installation which is carried out according to a cycle similar to that of which a description is given in the document FR-A-2,514,108 already mentioned.

The assembly shown in Figure 5 (where the elements corresponding to those of Figure 2 are designated by the same reference number) differs from the previous essentially by the shape given to the pipe 28. The curved part of the latter has a radius significantly higher than that of 1 pipe in Figure 2. It will be used in the case where the "fist hole is close to plate 2 or when the space available between the enclosure and the tube bundle is large enough.

FIG. 6 shows an assembly constituting yet another embodiment, usable when the curvature which it is necessary to give to the nozzle 28 to avoid interfering with the bundle of tubes is incompatible with the coming of the outlet bearing on the tubular plate . In the embodiment of Figure 6, the end portion of the pipe 28 is no longer constituted by a rigid tube, but by a deformable bellows 44. This bellows is connected by welding to a nozzle 46 screwed into the terminal bulge of the pipe, bulge which is crossed by the nozzle 36. When the bellows has the outline indicated in solid lines in FIG. 6, it makes it possible to introduce the pipe into the enclosure 1. This bellows can take the form indicated in dashes to come to be supported by fingers 30 of an end crown on the plate 2. The use of a compressible bellows has the additional advantage of making it possible to use the same assembly for steam generators having variable distances between “hole "and" tube plate ".

The installation shown in Figures 7 and 8 is intended to be implemented in a steam generator where the tubes are distributed in a square or at least rectangular network. However, the invention is also applicable to the case of a generator where the tubes are distributed along a triangular mesh. Figure 9 shows very schematically the relative arrangement of some tubes 7 in this case. The lance introduced by the water street 13 must then direct jets in the three directions indicated by arrows. For this it suffices to have a lance comprising nozzles directed in the appropriate directions. One can also move successively in the "water street" several lances, some of which provide oblique jets and not perpendicular to the lance, as described for example in the document US-A-2.112.896.

• - une zone centrale de la plaque, de forme triangulaire, délimitée par la rue d'eau 13 et par le point 44 d'intersection de deux lignes 43 partant approximativement des extrémités de ia rue d'eau et orientées suivant les directions du réseau obliques à la rue d'eau, reçoive des jets dans les trois directions,
• - une zone externe, délimitée par le point 44, les deux lignes 43 provenant des extrémités de la rue d'eau et l'enceinte 1, reçoive uniquement des jets perpendiculaires à la rue d'eau, et
• - les deux zones latérales restantes reçoivent des jets suivant une seule direction perpendiculaire à la rue d'eau et une direction oblique.

However, it appeared that the sludge torn off by the jets under high pressure risked, in the case of a triangular mesh network, being redeposited, whatever the kind of peripheral circulation produced. According to one aspect of the invention, this drawback is eliminated by providing the lances with nozzles oriented in the three directions of the network having inclinations on the horizontal such that the different zones of the tube plate do not all receive all of the jets. during the movement of the spears. More specifically, it has been found that particularly advantageous results are obtained when the nozzles are oriented so that:

• a central zone of the plate, of triangular shape, delimited by the water street 13 and by the point 44 of intersection of two lines 43 starting approximately from the ends of the water street and oriented in the directions of the oblique network at the water street, receives jets in three directions,
• - an external area, delimited by point 44, the two lines 43 coming from the ends of the water street and the enclosure 1, receives only jets perpendicular to the water street, and
• - the two remaining lateral zones receive jets in a single direction perpendicular to the water street and an oblique direction.

Figures 10, 10A-10D and 11 show how this type of sludge attack can be achieved by an appropriate arrangement of the nozzles 46-52, only the axes of which are shown in Figures 10A to 10D. FIG. 11 also shows an assembly 18 introduced by an “eye hole” 16. Four assemblies of this kind can be introduced through the enclosure 1. It is also possible to provide only two complete assemblies 18 comprising a projection nozzle d water, the other two assemblies ensuring only suction. We can even provide only the suction by counting on the jets projected by the lances 40 to ensure the sweeping.

Figure 12 shows a sludge removal device for a triangular mesh beam generator, of a type having a preheater which divides the base of the abutment into two half-beams (top and bottom of the figure ) separated by a central partition 56 and a skirt 54.

The device comprises two lances 40 of the type shown in FIG. 11, introduced by two opposite fist holes 17. Two removal assemblies 18, which ensure the suction of the sludge in suspension and the injection of sweeping and circulating water , are introduced through diametrically opposite eye holes at a small angular distance from one of the lances. Each of these assemblies 18 (only one of which is shown) is associated with an assembly 58 which ensures only the suction of water loaded with mud. Two double nozzles 60 introduced through eye holes, 90 'from the lances, open into the space between the enclosure 1 and the skirt 2 and make it possible to inject water under high pressure for cleaning this space. . The water thus introduced is taken up by the assemblies 18 and 58.

The general constitution of the spears may be one of those described above. As a general rule, a hole allowing high-pressure water to escape upwards will be provided to balance the forces exerted on the lance.

Claims (11)

1. A sludge removal device for an installation for cleaning the tubular plate (2) of a steam generator comprising, in the cylindrical enclosure (1) closed by the plate, a bundle of parallel tubes (7) connected to the plate and through which a primary fluid flows, the device comprising at least one insertable assembly (18) for liquid delivery and suction of the sludge, characterized in that said assembly comprises a suction pipe (20) having a curved part and a conduit (32) located within the pipe, suitable for connection to a cleaning liquid supply, ending in a nozzle (36) for projecting liquid along a direction transverse to the curved part of the pipe, along a path at a low angle with respect to an horizontal direction, and in that the nozzle terminates as a delivery head passing through the lateral wall of the pipe.

2. Device according to claim 1, characterized in that the conduit is held in position in its current portion by apertured centering devices spaced along the conduit.

3. Device according to claim 1 or 2, characterized in that the pipe has terminal c quatre lignes sautees » abutting fingers.

4. Device according to any one of the preceding claims, characterized in that the pipe has terminal abutting fingers.

5. Steam generator provided with a removable device according to any one of claims 1-4, characterized in that the enclosure of the generator is formed with a hole (16, 17) located in the vicinity of the tubular plate, in that said curved part has such a shape that it is insertable into the enclosure through the hole, opens downwardly and ends in the immediate vicinity of the plate, between the enclosure and the bundle of tubes, and in that the nozzle is angularly located for projecting the liquid in the circumferential direction of the enclosure.

6. Steam generator according to claim 5, characterized in that it further comprises cleaning liquid delivery tubes insertable into the enclosure through holes orthogonal to the hole for sais insertable assembly (18), the tubes being provided with fixed orientation nozzles for directing oblique jets towards the tubular plate and means for moving them radially with respect to the enclosure while interrupting the water supply thereto when the delivery tubes are aligned with tubes of the stack.

7. Steam generator according to claim 6, characterized in that, the steam generator being of the type comprising U-tubes circulated by the primary fluid and defining a water lane (13) along a diameter of the enclosure, tubes are provided for insertion through eyeholes aligned with the water lane whereas two assemblies are provided for insertion each through an eyehole at 90' with respect to the water lane.

8. Steam generator according to claim 7, characterized in that, the tubes being distributed in a regular triangular array, each delivery tube is provided for directing jets in three directions one of which is perpendicular to the water lane and the others at 60' from the first one.

9. Steam generator according to claim 8, characterized in that each delivery tube comprises, for each of the three directions, a plurality of nozzles (46-52) having an orientation with respect to the horizontal such that a central part of the plate receives jets in all three directions, a part of the plate distant from the water lane receives jets solely in a direction perpendicular to the water lane and the remaining parts receive jets perpendicular to the water lane and in a direction at 60' therefrom.

10. Steam generator according to any one of claims 6-9, characterized in that it comprises insertable assemblies devoid of water delivery tubes.

11. Steam generator according to any one of claims 6-10, comprising, at the lower part, a transversal partition and a skirt (54) defining an annular space with the enclosure (1), characterized in that it is provided with two suction and delivery assemblies (18) penetrating inside the skirt, diametrically opposite and in the vicinity of the partition (56) ; two suction assemblies (58) placed substantially opposite said suction and injection assemblies, in the immediate vicinity of the partition ; and two cleaning liquid supply nozzles (60) each placed on one side of the partition and opening into said annular space substantially in the middle of the ga between a suction and injection assembly (18) and the suction assembly (58) placed on the same side of the partition.

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