Westinghouse Electric Corporation

Warren E Lester

William K Cullen

Daniel E Klinvex

Robert J Maurer

An improved robotic arm which is capable of accurately manipulating a testing device beneath the tube sheet of the steam generator and accurately and consistently return to a selected tube location is provided. The robotic arm includes a base which is adapted to be fixedly secured to a support beam which initially positions the robotic arm within the steam generator, a first extension arm which is rotatably mounted on the base forming a primary rotation joint and which extends essentially parallel to the tube sheet. A second extension arm is rotatably mounted at the end of the first extension arm forming a secondary rotation joint and further extends therefrom. The testing device such as an eddy current inspection tool is positioned at a distal end of the second extension arm. The improvement includes a direct drive high-torque DC motor and a harmonic drive coupling being provided at each of the joints for providing a significant reduction ratio between the output of the high-torque DC motor and the rotational joint. Further, these components are of a light weight construction so as to limit the load carried by the robotic arm. A control device is provided for simultaneously independently controlling the high-torque DC motors such that the testing device can be both accurately and reliably positioned relative to the tube sheet. The robotic arm is also capable of being readily adjusted to be used in servicing various models of steam generators.

Robotic arm for servicing nuclear steam generators

An improved robotic arm for effecting a tube plugging operation is disclosed herein. The improvement generally comprises the provision of a compliance coupling between the plugging tool and the guidance mechanism of the robotic arm that is compliant in three dimensions, thereby allowing the plugging tool to smoothly insert tube plugs into the mouths of heat exchanger tubes despite inaccuracies in alignment caused by sag and other factors. The improvement further comprises a length adjustment assembly for allowing the length of the base arm of the robotic arm to be easily and conveniently changed so that the robotic arm can service more than one particular type of nuclear steam generator, as well as an emergency release mechanism for remotely detaching the tool from the arm in the event of a jam. Finally, a rotary-type tube plug magazine is provided which includes a spring loaded drum having a plurality of spring clips mounted around its periphery for detachably retaining a large inventory of tube plugs and unloading these plugs without scratching. A stop mechanism with rollers prevents the tube plugs retained by the spring clips from rotating past an unloading position where the plugging tool can engage and smoothly remove the plug. Once a plug is removed at the unloading station, the torsional spring rotates the drum to advance another tube plug to the unloading position, where it may likewise be unloaded into the plugging tool.

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Pittsburgh, PA, United States of America

Warren E Lester