Guided Ultrasonic Techniques

Ultrasound inspection as a quality tool has become quite popular and effective in thickness measurement, flaw detection, and material characterisation. Most systems utilise transducers which generate longitudinal or shear waves. These systems are very effective at detecting anomalies along the sound path. However, the sound path traverses only a small portion of the volume. This is time consuming and, if done improperly, can miss areas. However, in those situations involving inspection of sheet or tubular materials, an alternate inspection method utilising Guided Waves may be more suitable. Guided Waves are waves whose propagation characteristics depend on structural boundaries such as those in plates, tubes, rods, and embedded layers. These waves are usually generated by impinging the plate obliquely with a tone-burst from a relatively large transducer.

The resulting refraction and reflection at the interfaces produces many new signal packets. If the angle of incidence, or the frequency of sound is adjusted properly, the reflected and refracted energy within the plate will constructively interfere, thereby launching the plate wave. Because these waves penetrate the entire thickness of the plate and propagate parallel to the surface, a large portion of the material can be interrogated from a single transducer location. Alternatively, Guided Waves may be generated and detected by applying the Joule and/or Villari effect.

Typical Application - Pipe Inspection Under Insulation

Piping systems are often inspected ultrasonically to ensure safety. This can be accomplished by a series of point tests but from the outside of the pipe. If insulation covers the pipe, as is often the case, access to the outside surface requires removal of the insulation to perform the test, and then re-installation when testing is complete. Using Guided Waves, a probe can be applied to the pipe at a single location and several meters of the pipe can be inspected. The insulation is only removed where the sensor is applied. Tuning the element spacing and the excitation frequency permits selection of the appropriate Guided Wave Mode for inspection of the particular pipe geometry.

Application - Long Range Ultrasonics Test/Training Skid

CAN are currently technically assessing the three systems that are available, the decision of which system is purchased and offered to the market place will be taken by the end of April 2002. As part of this evaluation process CAN have fabricated a Long Range Ultrasonics Test/Training Skid.

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Semi-Automated Ultrasonic Inspection
of Critical End Area of Drill Pipe

Ultrasonic Inspection of Processing Piping

The CAN Group offices at: Aberdeen, Falkirk, Chesterfield, London UK; Stavanger, Norway; Abu Dhabi, U.A.E; New Orleans, New Jersey, Houston, USA; Ontario, Canada; Baku, Azerbaijan; Luanda, Angola.

CAN (Offshore) Limited is the main operating company within the CAN Group and is registered in England with company number 2015401. Registered office: Access House, Coneygarth Lane, Tunstall, Lancashire, LA6 2QP