Apparatus for inspecting and repairing tubes of a nuclear power plant

Abstract: By providing a yoke (36) to the shoulder (15) of a robot for in­ specting and repairing the tubes of a nuclear boiler, which yoke can receive an expandable anchoring piece (35) of an auxiliary tool (23) connected to the wrist (18) of the robot, said auxiliary tool (23) being provided with additional span fingers (37, 38), it is no longer a time-consuming and therefore expensive procedure to also inspect the tubes that lead to the tube sheet passages (9) into which the usual span fingers (8) of the robot were originally fixed.

Description: The invention relates to an apparatus as described in the preamble of claim 1. Such an apparatus is known from EP-A-0138583. During inspection one cannot omit the tubes that lead to the passages in which the span fingers of the apparatus are situated. On account of radio-activity, it is a time-consuming and therefore expensive task to displace the span fingers to the passages of tubes that have already been inspected. According to the invention an apparatus as described in claim 1 is provided to improve the above-described situation. The measures of the invention enable the apparatus suspension positions to be changed in a simple manner in order that the original suspension tubes can also be cleaned. EP-A-0008386 reveals an apparatus for inspecting and repairing the tubes of a boiler of a nuclear power plant which adresses the same problem as that of the application, but the solution proposed involves the use of a large support plate with a multiplicity of holes which must match those of the tube sheet thus making the apparatus cumbersome and inflexible. The preferred embodiments are the subject of dependent claims 2 to 4. The invention will be further elucidated hereinafter on the basis of the drawing, representing, by means of an example, an embodiment of an apparatus according to the invention. In the drawing: fig. 1 shows, in perspective, an apparatus for inspecting and repairing without auxiliary tool, and figures 2-4 show a rear view, a plan view and a side view of an auxiliary tool according to the invention. The apparatus represented in figure 1 comprises an upper plate 1 and a lower plate 2 which are connected by two guide bars 3 and 4. A carriage 5 can be moved along the guide bars 3 and 4. Said motion is effected in that the carriage comprises a screw sleeve (not shown) that is mounted on a spindle 6 extending through the carriage 5, which spindle can be rotatably driven by a drive means 7. The top plate 1 comprises two span fingers 8 that can be fixed in passages 9 of a tube sheet 10 of the boiler. The term span fingers is understood to refer to fixing means that can be inserted when they are of smaller diameter and that can expand after insertion, so that a firm fixture between the two parts can be obtained. The bottom plate 2 comprises two vertically adjustable support legs 11 and 12, with the aid of which the apparatus can be elongated in order to insert the span fingers 8 into the passages 9. The carriage 5 comprises a receiving dovetail portion 13 devised in the known manner for receiving an inserting dovetail portion 14 of a shoulder 15 of an arm assembly 16 which furthermore also comprises an upper arm 15', an elbow 17 and a lower arm 17', and a wrist 18. Due to a drive means 19 the upper arm 15' is able to rotate about a vertical shaft with respect to the shoulder 15, and the same is applicable to the rotation options between the lower arm 17' and the upper arm 15', and the wrist 18 and the lower arm 17', respectively. In this manner, together with a carriage 5 all points in a three-dimensional space can be accurately reached. After the parts 1-13 have been hoisted through a manhole into the boiler and have been fixed therein, the parts 14-19 are mounted thereon with the aid of the dovetail joint 13/14. In order to be able to release this joint again upon removing the apparatus, a known release lever 20 has been mounted. At its end, the wrist 18 comprises a receiving dovetail portion 21, arranged in the known manner, from which tools for inspecting or repairing can be suspended. With the aid of cables 22 and cameras and monitors (not shown) the entire apparatus, which can be regarded as a robot, can be remote-controlled. According to the invention, the receiving dovetail portion 21 of the wrist 18 can also be used for positioning an inserting dovetail portion 24 of an auxiliary tool 23 represented in figures 2-4. The auxiliary tool 23 comprises two guide bars 27 connected by end partitions 25 and 26. A screw spindle 29 is positioned between the guide bars, which spindle can be driven by a drive means 30, so that with the aid of a screw sleeve fixedly mounted into the table 31, the table can be displaced back and forth along the guide bars. The conduits necessary for driving the carriage are connected to a code transmitter 32 and extend through a cable gutter 33 to the drive means 30. The inserting dovetail portion 24 of the auxiliary tool 23 is mounted on the outside of a vertical portion of a corner piece 34. The horizontal portion of the corner piece 34 is mounted under the table 31 and below this horizontal portion there is an anchoring piece 35 that can end up of its own accord in a yoke 36 mounted on the shoulder 15, indicated by a dotted line in figure 4, that is if the robot is correctly remote-controlled. Once the anchoring piece 35 is placed in the yoke 36, then the anchoring piece can expand so that a firm connection to the yoke is established. Additional span fingers 37 and 38 are mounted onto the end partitions 25 and 26 of the auxiliary tool 23, so that the robot can be temporarily suspended, as it were, from the additional span fingers 37 and 38, after which the span fingers 8 of the upper plate 1 can be programmed to be transferred to another set of passages 9 of the tube sheet 10. With the invented auxiliary tool the robot can thus be transferred rapidly to another position with respect to the tube sheet, so that the tubes in which the span fingers 8 of the upper plate were located can also be inspected or repaired. Perhaps needless to say that during these operations numerous precautions have to be observed in order to prevent radio-active contamination of environment and personnel. One of the precautions is that sensors 39 can be mounted on top of the end partitions 25 and 25, which sensors assess whether the auxiliary tool 23 has accurately arrived at its destination. The end partitions 25 and 26 are exchangeable so as to have the additional span fingers 37 and 38 at the correct pitch and diameter with respect to the passages 9 of the pipe plate 10.

Claims: Apparatus for inspecting and repairing the tubes of a boiler of a nuclear power plant, which apparatus can be hoisted through a manhole of the boiler to a tube sheet (10) and which apparatus comprises upper and lower plates (1; 2) connected by guide bars (3, 4) along which a carriage (5) can be moved up and down, to which carriage an arm assembly (16) is connected, consisting of a shoulder (15) with pivotably connected upper arm (15'), an elbow (17) with pivotably connected lower arm (17') and a wrist (18) which is pivotably connected to the lower arm, which arm assembly can be connected to inspection and or repair tools at the wrist, which faces away from the carriage, wherein said carriage and said arm assembly comprise drive means (7) for remote-controlling the inspection or repair tools, and wherein the upper plate can be fixed by means of span fingers (8) in two passages (9) of the tube sheet, characterized in that a yoke (36) has been mounted on the shoulder (15), said yoke receiving an anchoring piece (35) of an auxiliary tool (23), said tool being connected to the wrist (18), said tool comprising two additional span fingers (37, 38) that can be fixed in passages (9) of the tube sheet (10) thereby taking the weight of the apparatus so as to permit the transfer of the span fingers (8) of the upper plate (1) to another set of passages of the tube sheet. Apparatus according to claim 1, characterized in that the auxiliary tool (23) consists of two guide bars (27, 28) connected by means of end partitions (25, 26) along which bars a table (31) connected to the anchoring piece (35) can be moved back and forth, the additional span fingers (37, 38) being mounted on the end partitions (25, 26). Apparatus according to claim 1, characterized in that the end partitions (25, 26) of the auxiliary tool (23) are exchangeable in order to adapt the pitch distance of the additional span fingers (37, 38) to the tube pitch of the tube sheet (10). Apparatus according to one of the claims 2 and 3, characterized in that approach sensors (39) are mounted on top of the end partitions (25, 26).

Inventors: VERMAAT HUIBRECHT PIETER, VERMAAT, HUIBRECHT PIETER
Applicants: VERMAAT TECHNICS BV, VERMAAT TECHNICS B.V.
Application year: 1989
Main classification: F22B37
IPC codes: F22B37