ULTRASONIC INSPECTION OF ADHESIVE-BONDED COUPLER JOINTS IN GRP PIPINGSYSTEMS

Ultrasonic measurements have been performed with two typical GRP pipe materials, and it was found that the attenuation increased approximate ly linearly with frequency, thus implying that low frequency transduce rs should be used for inspection. By combining measurements from two t ransducers located at opposite sides of flooded pipes, quantitative me asurements of propagation times through the GRP pipe wall were obtaine d without prior knowledge of wall thickness, internal pipe-diameter, a nd sound velocity of the liquid in the pipe. C-scan imaging of GRP pip es was performed by measuring the ultrasonic attenuation through the p ipe wall by a pulse-echo method from the outside, with the opposite in ner pipe-wall acting as reflector for the signal. The quality of the r esulting images was comparable to the quality of images obtained by th e conventional through transmission technique.