Robot Rallies To Reactor Repair

Specialist robot manufacturer, Bristol based OC Robotics was recently commissioned by Swedish nuclear plant operator, Ringhals to construct special robots capable of entering the containment vessel of its Ringhals 1 Boiling Water Reactor (BWR), to repair some damaged pipework. The robots were required to negotiate very tortuous paths to access the area in question and then carry out the remedial work in a very confined space.OC decided to base the two robots - one to enter the reactor from below, the other from above - on its established snake-arm design (see DPA XXXX page XX). Among the critical components of the Ringhals snake arm robots, which enable them to achieve their precise targeting, are THK's BNS integrated ball screw and ball splines. Providing reliable and accurate linear, spiral and rotational motion with no backlash, these consist of a single shaft with two nuts, one of which moves along a ball spline groove, the other along a ball screw groove. Some modification was required, including matching the BNS components to meet the size constraints of the motors, all of which was carried out by THK on behalf of its customer.Most robots offer six degrees of freedom. However, the overhead operating Snake-Arm has 13, while its underside counterpart has no fewer than 23 for this demanding application. Some of the tasks performed by these robots included placing fixtures to immobilise the free end of the post cut pipe; securing the pipe section during cutting; removing the cut section; locating tools and using them to reshape the cut surfaces; introducing the new pipe section; tack welding it in place; locating a gas shield for the final internal weld and, finally, to remove all fixtures and leave the reactor without colliding with any pipework on the way.

Contact Details and Archive...

• THK UK

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