Processing techniques for the inspection of offshore structures

This paper is concerned with the techniques required for the acquisition and processing of signals arising in ultrasonic non-destructive testing of steel structures in the underwater environment. The primary aim is to minimize diver participation in the inspection and interpretation of results. The resulting systems, which involve significant use of microprocessor hardware were designed to operate with equal facility with either single or multiple ultrasonic channels, the latter being important with the ancillary requirements of beam steering and beam shaping. The paper describes two approaches to the detection and location of faults, one concerned with the use of large ultrasonic crystals has led to the development of the Strathclyde SHOE, the other employs ultrasonic arrays for area scanning via beam steering. An analysis is included for signal returns on the arrays for estimating the location of a reflection point which leads to enhanced range resolution.