PLC control systems for the remote control of cranes and manipulators

The currently under construction and nearing completion nuclear reprocessing plants, the Thermal Oxide Reprocessing Plant (THORP) at Sellafield in Cumbria, is divided into two main plant areas, the head end and chemical separation facility. Within the head end and chemical separation facility are two virtually identical areas known as the north and south filter caves. All contaminated air from within the THORP ventilation system is routed to these filter caves. The control system described is responsible for filter change and all other `in-cave´ activities. Within the filter cave is an electrically driven overhead travelling crane (EOTC) a carriage, a 2 tonne auxiliary hoist, a 500 kg telescopic mast, a powered grab and a 70 kg articulated power manipulator arm. Two independent PLC´s are used, the first controlling and monitoring the EOTC, hoist, telegrab and manipulator and the second to control and monitor shield doors, gamma gate, bogie and delidder