Drilling rig for processing pipes in radioactive environments

Abstract

Drilling device (10) for machining tubes (66) on tube sheets (64) of heat exchangers in a radioactive environment, comprising a transport device (12) having clamping elements (18, 24), characterized in that a drilling device (16) having clamping fingers (30) is held by the transport device (12), that the clamping elements (18, 24) and the clamping fingers (30) are arranged on a common first side of the drilling device (16) and the transport device (12), that the transport device (12) and the drilling device (16) are connected to a support device (14), that the support device (14) has a support plate (50) on which a support plate (28) of the drilling device (16) rests, that the support plate (50) is connected to the support plate (28) by at least one movable connecting element (62), that the support plate (28) is connected to the support plate (50) in a first position of the connecting element (62) is connected without play,that the support plate (28) has a predeterminable play relative to the carrier plate (59) in a second position of the connecting element (62).

Description

The invention relates to a drilling apparatus for the processing of pipes on tube sheets of heat exchangers in a radioactive environment.In nuclear power plants, maintenance work and possibly repairs are carried out at regular intervals. There are areas in the nuclear power plant that are exposed to radioactive radiation and after a certain time themselves emit radioactive radiation. In this radioactive environment, too, the maintenance work and repairs have to be carried out, for example on steam generator or heat exchanger tubes. The radioactive environment is unsuitable for persons and at most is briefly accessible. Moreover, legal requirements require that a radiation load on personnel and material is as low as possible and must not exceed a specific upper limit. In this respect, the use of the smallest possible amount of material is also desirable. Remotely controllable machine tools or test devices are also used in these areas.For the repair of pipes held in tube sheets, there is a drilling machine mounted on a robot arm of a robot and positioned with the robot arm at the location to be machined in the radioactive environment. A disadvantage of this system is that the drilling machine can only be used in the working area of the robot arm. If a plurality of locations on a tube sheet are to be machined, the robot must first be moved to another location, so that the location to be machined can be reached again by the robot arm. This is comparatively complicated. In addition, the mass of the robot by the robot arm is correspondingly high. Alternatively, the robot arm can be designed to be so large that the working range corresponds to the extension of the tube sheet. The mass of the repair robot is then even greater and the mounting or dismantling of the robot is particularly complicated.One possibility of moving over a larger region of the tube sheet of a steam generator or heat exchanger in a nuclear power plant is offered by an inspection robot which has become known. The latter moves a measuring probe in a type of placement cycle to the desired location on the tube sheet to be tested in that groups of holding devices are alternately anchored in the tubes of the tube sheet or become detached and thereby retract into new tubes and anchor themselves there again. The inspection robot does not have a component comparable to the robot arm and is correspondingly lighter. However, the disadvantage of the inspection robot is that its mechanical system due to the movable parts has a comparatively high degree of imprecision in the positioning of the measuring probe, which is sufficient for a measurement, but is unsuitable for a processing of pipes of a different type using a drilling machine, which cannot be corrected manually. Any correction possibilities for positioning the inspection robot are namely provided neither in the plane of the tube sheet nor perpendicular to this plane.Proceeding from this prior art, it is an object of the invention to specify a drilling device which as simply as possible reaches a multiplicity of working positions on a tube plate and has sufficient accuracy for machining tubes.The object is achieved by a drilling apparatus for processing pipes on tube plates of heat exchangers in a radioactive environment, having a transport device having clamping elements and having a drilling device having clamping fingers, which are each arranged on a common first side, wherein the transport device and the drilling device are connected to a support device, wherein the support device has a support plate on which a support plate of the drilling device rests, wherein the support plate is connected to the support plate by at least one movable connecting element, wherein the support plate is connected to the support plate without play in a first position of the connecting element, wherein the support plate has a predeterminable play with respect to the support plate in a second position of the connecting element.The invention thus comprises a transport device with clamping elements for movement. With the transport device it is possible to move the drilling device principally to each pipe or to each working position on a pipe base. The drilling device is rigidly connected to the transport device during the transport process, in that the connecting element remains in the first position during the transport. After reaching the second position, the connecting element is moved, so that the transport device, which is clamped firmly to the tube plate, is connected with a clearance to the drilling device, an axial and / or radial clearance with respect to the connecting element. With this play, the drilling device is made possible to insert the clamping fingers into tubes of the tube sheet and to fasten them there, in particular to clamp them. The clearance is dimensioned such that the jamming of the drilling device in the pipes takes place on the pipe base without forces being transmitted to the transport device as a result. Possible inaccuracies in the positioning of the drilling device by the transport device are compensated for by the play. The movable parts of the transport device can cause inaccuracies of the typical order of magnitude up to 2.5 mm or 3 mm. The rigid frame structure of the drilling device is adapted for the machining position of a tool in the drilling device to have the required accuracy when the clamping fingers are properly clamped in the pipes.A further development of the drilling apparatus according to the invention provides that the transport device has at least four holding elements on the first side, which are divided into two groups, that each group can be controlled separately, that a first group of holding elements can be pivoted with respect to a second group of holding elements, and that a group of holding elements can be displaced with a linear movement. In this way, two movements in the transport device are possible. On the one hand, pivoting of the two groups of holding elements relative to one another is made possible. The transport device is thus enabled to change direction. On the other hand, a group of holding elements is allowed a linear movement. In this way, a step-by-step displacement of the transport device along a straight line is made possible. The two movement options are sufficient to enable the transport device to reach any desired location on the pipe base in a particularly simple manner with the drilling device.An advantageous embodiment of the drilling apparatus is if the drilling device has at least two holding fingers, and if the holding elements and the at least two holding fingers are movable in the direction perpendicular to the first side. In this way, it is achieved in a particularly advantageous manner that those holding elements or holding fingers can be moved into or out of the tubes as required. If the holding elements or holding fingers are moved out completely, for example, no structural elements which could become hooked into the tube sheet protrude on the first side.A further embodiment of the drilling device provides that the support plate or the support plate has at least one limiting element which is arranged in a recess, and that the shape of the recess allows play in the second position of the connecting element. With such a constructional measure, it is advantageously achieved that the maximum play between the support plate and the support plate is limited. The play can thus also be adapted in a particularly simple manner if necessary.A further development of the drilling apparatus is characterized in that the connecting element has a drive device, in particular a pneumatic or hydraulic drive device, by means of which the connecting element can be optionally brought into the first or second position.A further development of the drilling device is achieved if a cylindrical component is arranged on the support plate, that a force can be exerted on the support plate by the cylindrical component, that the support plate can be moved by a predeterminable distance in the direction of the second position. In this way, it is ensured that the support plate is spaced apart from the support plate and that the play for compensating the position inaccuracies is thus also present. It can namely occur that the connecting element is indeed brought into the second position, but the support plate remains lying on the support plate. In such a case, there would also be no play, since the centering pins then do not permit any play.It is particularly advantageous if the force is introduced into the support plate in a region of an imaginary line which is perpendicular to the first side and passes through the center of gravity of the drilling device. In this way, it is ensured that the drilling device is applied uniformly to the tube sheet, i.e. that, for example, available spacer elements are applied to the tube sheet almost simultaneously. An undesired oblique position of the drilling device is avoided.Further advantageous embodiment possibilities can be gathered from the further dependent claims.The embodiments illustrated in the drawings are intended to describe the invention, further embodiments and further advantages in more detail.They show FIG. 1 shows an exemplary embodiment of a drilling device in plan view, FIG. 2 is a view of a transport device with a carrier element of the drilling device, FIG. 3 shows a view of a region around the carrier element, and FIG. 4 shows a side view of a partial region of the drilling device on a tube sheet.FIG. 1 shows a top view of an exemplary embodiment of a drilling device 10 according to the invention, in which a transport device 12 is connected to a drilling device 16 by a carrier element 14. The top view here points to the side which faces a tube sheet in the case of machining. The transport device 12 has two first holding elements 18 which are connected by struts 20 and are spaced apart from one another. A housing 22 of the transport device 12 has two second holding elements 24. The struts 20 can be moved back and forth by a strut drive 46, so that the distance between the first holding elements 18 and the strut drive 46 changes as required. In addition, the first holding elements 18 can be rotated or pivoted by a motor 26 through a predeterminable angle relative to the second holding elements 24. The pivoting can also be effected in the opposite direction, namely that the second holding elements 24 pivot by the motor 26 through a predeterminable angle relative to the first holding elements 18. An axis of rotation of the rotational movement is perpendicular to the illustration in this plan view.The drilling device 16 has a holding plate 28 which has recesses through which two holding fingers 30 pass. The spacing of the two holding fingers 30 is dimensioned such that they are adapted to the spacings of the tubes in the tube sheet. Tube plates are to be understood here as meaning all tube plates which occur in heat exchangers or steam generators of nuclear power plants. Typical tube diameters for such tube sheets are 12 mm to 22 mm. In some cases, tube diameters differing therefrom also occur. The diameters of the part of the holding fingers 30 which is clamped in the tubes are adapted to the different tube diameters. The spacing of the recesses of the holding plate 28 is also adapted to the spacings of the tubes in the respective tube plate. A tool holder 32 in this figure laterally projects beyond the holding plate 28.FIG. 2 shows a view of the transport device 12 with the carrier element 14 of the drilling device 10. The first holding elements 18 are namely pivotable about an axis of rotation via the second holding elements 24 and can also be moved back and forth along a respective axis of symmetry 42. The transport device 12 is then moved as follows. In a starting position, the second holding elements 24 are to be clamped in a tube sheet. In this case, both second holding elements 24 and the spacer knobs 40 bear against the tube sheet. The first holding elements 18 are inserted into a holding element housing 44 to such an extent that the tube sheet is not touched when the transport device 12 of the first holding elements 18 is moved. The holding fingers 30 also have a functionality comparable to the holding elements 18, 24 and are retracted in the transport phase of the drilling device. However, the drilling device 16 is not shown in this figure. Now, a movement of the first holding elements 18 along the struts 20 is effected by a strut drive 46 by an amount predefined by a controller. The control optimizes the movement in such a way that the transport destination of the drilling device 10 is reached with as few transport steps as possible. For a change of direction, the first holding elements 18 are pivotable relative to the second holding elements 24. After the first holding elements 18 have reached their position, they are moved out of the holding element housing 44 and into a tube on the tube sheet and clamped there. If the first holding elements 18 are properly clamped in the pipes, the transport device 12 and thus the drilling device 10 are secured in position with the first holding elements 18 so that the second holding elements 24 are released and inserted into the holding element housings 44. In the next following method step, the strut drive 46 moves with it the transport device 12 along the struts 20 to a new location on the tube sheet. There, the second holding elements 24 are extended again and clamped in tubes. The first holding elements 18 are released and inserted again into the holding element housings. Subsequently, the strut drive 46 moves the first holding elements 18 to a new position. In this way, the initial situation of the movement method is restored, but the drilling device 10 is displaced by a certain distance from the original position. This procedure is repeated until the desired target position of the drilling device 12 is reached. By pivoting or rotating the transport device 12 about the axis of rotation, the drilling device 16 can be positioned at a desired location.FIG. 2 shows the carrier element 14 which is connected to the transport device 12. The carrier element 14 has a plate carrier 48, on which a carrier plate 50 is arranged and is connected to the plate carrier 48 by a plurality of screws 52. The support plate 50 is arranged on the side of the drilling device 10 facing the tube sheet and parallel to the tube sheet. The plate carrier 48 also has two side arms 54, on each of which a centering cone 56 and a limiting pin 58 are arranged. In addition, a first drive is mounted on the plate carrier 48, by means of which a cylinder pin 60 can be moved, if necessary, through a recess in the support plate 48 in the direction of the tube sheet. In addition, a connecting element 62 is shown on the support plate 50, the function of which is explained in more detail in FIG. 4.FIG. 3 shows a view of a region around the support element 14 on a tube sheet 64 with tubes 66. The holding plate 28 has spacers 68 which have a comparable function for the drilling device 16 as the spacer knobs 40 for the transport device 12. In addition, one of the two holding fingers 30 can be seen in this figure, wherein the latter has a chamfer 70 on its side pointing toward the tube sheet 64. The chamfer 70 is dimensioned such that the insertion into a tube 66 is facilitated, even in the case where the tube central axis and the central axis of the holding finger 30 are offset with respect to one another in the region of imprecision in the positioning by the transport device 12. Even in the case of deviations from the parallelism of the central axis within the imprecision, the insertion of the holding finger 30 into a tube 66 is made possible in this way. By inserting the holding finger 30, the position is changed from its central axis to parallelism with the tube central axis.FIG. 4 shows a side view of a region of the drilling apparatus 10 and the tube sheet, wherein a partial region of the figure is shown as a section through the drilling device 16 and the tube sheet 64. The drilling tool 10 is held by the second holding elements 24 which are clamped in pipes 66 of the tube sheet 64, while the first holding elements 18 are only partially arranged in pipes 66 and are accordingly not clamped. On the holding plate 28 are arranged a number of spacers 68, which in this figure have a first distance 72 of 2 mm from the tube sheet 64. Accordingly, the drilling device 16 does not yet bear against the tube sheet 64 which can be indicated by a limit switch 74 which is likewise arranged on the retaining plate 28.The connecting element 62 is movable by a pneumatic drive 76 which has a pneumatic cylinder 78, with which the movement force can be applied to the connecting element 62. The pneumatic cylinder 78 works against a spring force of a spring 80, wherein the figure shows the pneumatic cylinder 78 in a non-pressurized second position, in which the connecting element 62 of the support plate 50 is moved away from the spring, so that the support plate 28 can be moved with a clearance with respect to the support plate 50. The second distance between the support plate 50 and the support plate 28 shown in this figure is, however, 0 mm, so that the possible play has not yet been used.The operation of the drilling apparatus 10 will be explained in more detail below. In this case, the drilling device 16 should have been moved to a working position by the transport device 12. The spacers 68 are then still approximately 2 mm from the tube sheet. The holding fingers 30 and the cylinder pin 60 are retracted and the pneumatic cylinder 78 is acted upon by compressed air. When the pneumatic cylinder 78 is supplied with compressed air, the connecting element 62 is in a first position, in which the retaining plate 28 is held on the supporting plate 50 without play. The centering cones 56 are positioned in the corresponding centering recesses in the holding plate 28 in the first position and thus ensure that the holding plate 28 is in the structurally predefined position relative to the supporting plate 50. The first position is also suitable for manual handling with the drilling device 10 or for mounting the mounting unit comprising the drilling device 16 and the carrier element 14 on the transport device 12, since the components of the mounting unit are firmly connected to one another as if it were a component. In a next following working step, the pneumatic cylinder 78 is depressurized, so that the spring 80 moves the connecting element 62 into the second position. This allows the drilling device 16 to disengage from the support plate 50 and tilt to one side. This tilting is limited, however, by the spacers 68 in that one or more of the spacers 68 are placed against the tube sheet 64, depending on the direction of the tilting. In a next working step, the holding fingers 30 are each moved into tubes 66 by a holding finger drive 84. The spreading elements 86 of the holding finger 30 are held by an elastic ring 88 to a smallest possible diameter of the holding finger 30, so that there is a greatest possible radial play between the holding fingers 30 and the tubes 66. This situation is shown in Fig. 4. In a further working step, the cylinder pin 60 is extended with a corresponding cylinder pin drive, so that the retaining plate 28 is raised and is released from the support plate 50. The cylinder pin drive is advantageously set such that the lifting force is only slightly higher than the weight force of the drilling device 16. The advantage of this force application point is that the spacers 68 then bear against the tube sheet 64 in a particularly advantageous manner. In a next following working step, the holding fingers 30 are tensioned in the tubes 66 by the holding finger drive 84 moving a cone mandrel in the direction of the spreading elements 86 and pressing these against the circumferential surfaces of the tubes 66 counter to the force effect of the elastic ring 88. In this way, the retaining fingers 30 are clamped in the tubes 66. A further advantage of this procedure during clamping is that the holding fingers 30 are centered in the tubes 66 and with respect to the tubes 66, since the holding fingers 30 of the holding plate 28 and thus are connected to the drilling device 16, the drilling device 16 itself is also aligned and, in addition, the holding plate 28 is aligned parallel to the tube sheet 64. The alignment is made possible in that, by releasing the holding plate 28 from the supporting plate 50, the centring cones 56 allow a relative movement of the two plates with respect to one another, wherein the relative movement is limited by the limiting pins 58 and the dimensioning of the recesses in which the limiting pins are accommodated. Due to the construction of the drilling device 16, the tool, for example a drill or milling cutter, is now positioned on the drilling device 16 exactly centrally with respect to the pipe 66 to be machined. In a further working step, the holding fingers 30 are switched back into the retraction operating mode by their holding finger drive 84. However, the spacers 68 prevent retraction and, in addition, the retaining fingers 30 are firmly clamped in the tubes 66. Therefore, the drilling device 16 is pulled to the tube sheet 64 with the pulling force of the retraction, in the presented exemplary embodiment of the subject matter of the invention at 10 kN. This tensile force ensures that the forces occurring during the machining of a pipe 66 are reliably absorbed by the drilling device 16. Thus, the feed force for the tool in the exemplary embodiment is 2 kN. In addition, the machining position of the tool is laterally outside the holding plate 28, so that an additional moment is introduced into the drilling device by the machining. In addition, during the machining, vibrations and further forces occur which are reliably absorbed by the drilling device 16 and conducted into the tube sheet 64. The pneumatic cylinder 78 is pressureless, so that the connecting element 62 is in the second position. Thus, no forces occurring during the processing are transmitted to the transport device 12. After the machining is finished, the above-described working steps are reversed, so that the holding plate 28 is again firmly connected to the supporting plate 50 by the connecting element 62.List of reference characters10 Drilling tool 12 Transport tool 14 Carrier element 16 Drilling device 18 First holding elements 20 Struts 22 Housing 24 Second holding elements 26 Motor 28 Holding plate 30 Holding finger 32 Tool holder 34 Machining axis 40 Spacer nub 42 Axis of symmetry 44 Holding element housing 46 Strut drive 48 Plate carrier 50 Carrier plate 52 Screws 54 Side arms 56 Centering cone 58 Limiting pin 60 Cylinder pin 62 Connecting element 64 Tube base 66 Tubes 68 Spacers 70 Chamfer 72 First distance 74 Limit switch 76 Pneumatic drive 78 Pneumatic cylinder 80 Spring 84 Holding finger drive 86 Spreading elements 88 Ring

Claims

Drilling apparatus (10) for processing pipes (66) on tube sheets (64) of heat exchangers in a radioactive environment, having a transport device (12) which has clamping elements (18, 24), characterized in that a drilling device (16) which has clamping fingers (30) is held by the transport device (12), in that the clamping elements (18, 24) and the clamping fingers (30) are arranged on a common first side of the drilling device (16) and of the transport device (12), in that the transport device (12) and the drilling device (16) are connected to a supporting device (14), in that the supporting device (14) has a supporting plate (50) on which a support plate (28) of the drilling device (16) rests, in that the supporting plate (50) is connected to the support plate (28) by at least one movable connecting element (62), the support plate (28) is connected without play to the support plate (50) in a first position of the connecting element (62), and the support plate (28) has a predeterminable play relative to the support plate (59) in a second position of the connecting element (62).Drilling apparatus (10) according to claim 1, characterized in that the transport device (12) comprises on the first side at least four holding elements (18, 24) which are divided into two groups, that each group is separately controllable, that a first group of holding elements (18) is pivotable with respect to a second group of holding elements (24), and that a group of holding elements (18) is displaceable with a linear movement.Drilling apparatus (12) according to claim 1 or 2, characterised in that the drilling device (16) has at least two holding fingers (39), and in that the holding elements (18, 24) and the at least two holding fingers (30) are movable in the direction perpendicular to the first side.Drilling device (12) according to one of the preceding claims, characterized in that the support plate (50) or the support plate (28) has at least one limiting element (58) which is arranged in a recess, and in that the shape of the recess allows play in the second position of the connecting element (62).Drilling device (12) according to one of the preceding claims, characterized in that the support plate (59) or the support plate (28) has at least one approximately conical or frustoconical centring element (56), and in that the support plate (50) and the support plate (28) are arranged in a predefined position with respect to one another by the at least one centring element (56), provided that the connecting element is positioned in the first position.Drilling apparatus (12) according to one of the preceding claims, characterized in that the connecting element (62) has a drive device (76), in particular a pneumatic or hydraulic drive device, by means of which the connecting element (62) can be optionally brought into the first or second position.Drilling tool (12) according to claim 6, characterised in that the drive device (76) has a spring (80), and in that the support plate (28) with the support plate (50) is held in the second position by the spring (80) when the drive device (76) is switched off.Drilling apparatus (12) according to claim 6 or 7, characterised in that the drive device (76) has a drive such that the drive works against the spring forces of the spring (80) such that the connecting element (62) can be moved into the first position by a predeterminable distance perpendicular to the first side.Drilling device (12) according to one of claims 6 to 8, characterised in that a cylindrical component (60), in particular a pin or bolt, is arranged on the supporting plate (50), in that a force can be exerted on the support plate (28) by the cylindrical component (60), in that the support plate (28) can be moved by a predeterminable distance in the direction of the second position.Drilling tool (12) according to claim 9, characterized in that the force is applied in a region of an imaginary line in the support plate (28), which is perpendicular to the first side and passes through the centre of gravity of the drilling device (16).A drilling tool (12) according to claim 9 or 10, characterized in that the force is no more than 10 percent higher than is necessary to balance the weight force of the drilling device (16).Drilling apparatus (12) according to one of the preceding claims, characterized in that the functions of the transport device (12) and / or of the drilling device (16) and / or of the carrier element (14) can be controlled by a control device.

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