Experimental study on ultrasonic guided waves in fluid-filled pipes surrounded by water

Corrosion in water pipeline is a major problem in the offshore oil industry. However, some underwater or half-underwater pipes of the offshore platform, especially those vertical pipes suffering from storm, tide, ice or other sea floaters, are difficult to be examined by conventional inspection method. In this paper, conventional methods used to examine underwater pipeline are briefly discussed, then a new method, ultrasonic guided wave techniques are introduced for underwater pipeline inspection. Guided ultrasonic waves can propagate long distance along the pipe wall without significant attenuation. However, since vertical pipes of the offshore platform are usually fluid-filled and underwater, leakage of energy into the fluid is possible. In this paper, pipeline inspections were conducted using longitudinal cylindrical guided waves. Experiment was set up to examine guided ultrasonic waves propagating in fluid-filled pipes when 4/5 of the pipe is immerged in water. This investigation shows that ultrasonic guided wave technique can be used for health monitoring of underwater pipes.