POSITIONING DEVICE FOR TOOL

摘要

A sludge lance nozzle for removing sludge from between the tubes of a nuclear steam generator includes positioning apparatus mounted on top of the nozzle. The tubes are arranged in rows and columns with the axes of the tubes in each column lying in a common column plane. The nozzle is moved perpendicular to the column planes close to one of the rows of tubes. In one embodiment, the positioning apparatus comprises two transmitter/receivers for transmitting signals and receiving reflected signals along axes parallel to the column planes, the axes being spaced apart by odd multiples of one-half tube pitch. The received signals are subtracted to produce a position indicating signal. In another embodiment the positioning apparatus includes a transmitter and a receiver spaced apart in the direction of movement of the nozzle, the transmitter transmitting a signal in a first predetermined direction, and the receiver being responsive only to reflected signals received from a second predetermined direction.