Graphics and control of the guide tube assembly reinforcement manipulators at Sizewll 'A'

A method was devised to reinforce the lower lug welds of the Guide Tube Assemblies (GTAs) at Sizewell ''A''. A six degree of freedom manipulator was designed to place a clamp around the lugs and tighten it. The manipulator was fitted with three fixed cameras but required another surveillance manipulator positioned in an adjacent standpipe to provide additional views. The need to prepare two standpipes limited the rate at which reinforcements could be made. Therefore an articulated two arm camera manipulator, which could be used on the existing manipulator mast was designed and built. The two manipulators were driven from separate desks and were controlled by the same supervisory computer linked to on-line graphics. The camera arm joints were driven on preplanned routes using a single joystick because of the complex moves and tight spaces involved. A large number of GTA sites have now been reinforced including a dropped GTA which had to be raised to carry out clamping. (UK)