Ultrasonic Inspection of Adhesive Bonded Coupler Joints in GRP Piping Systems

Ultrasonic measurements have been performed with two typical GRP pipe materials, and it was found that the attenuation increased approximately linearly with frequency, thus implying that low frequency transducers should be used for inspection. By combining measurements from two transducers located at opposite sides of flooded pipes, quantitative measurements of propagation times through the GRP pipe wall were obtained without prior knowledge of wall thickness, internal pipe-diameter, and sound velocity of the liquid in the pipe. C-scan imaging of GRP pipes was performed by measuring the ultrasonic attenuation through the pipe wall by a pulse-echo method from the outside, with the opposite inner pipe-wall acting as reflector for the signal. The quality of the resulting images was comparable to the quality of images obtained by the conventional through transmission technique.