Performance characteristics of ultrasonic NDT probes at high hydrostatic pressure for inspection of offshore installations

In the present work an attempt has been made to study the performance characteristics of commercially available contact-type NDT probes, at pressures up to 2.8 x 10(6) Pa (equivalent to 280 m depth). The parameters studied are pulse-echo sensitivity, its frequency response and the electrical impedance of a normal beam probe. Pulse-echo sensitivity is observed to decrease at high pressures to about 60% of its value at the normal pressure. The observed results have been explained in terms of the effect of the pressure on the backing material of the probe and hence the effect on the probe performance. From the frequency response of the pulse-echo sensitivity it is observed that the probe bandwidth decreases at high hydrostatic pressures.