Guided wave testing method for pipes certified

TÜV SÜD evaluated and successfully certified the guided wave testing method for basic pipes used by UK Guided Ultrasonics Ltd.

(September 2010)

Pipes in chemical and petrochemical plants and power stations must be inspected for defects at periodic intervals. Qualified testing procedures play a significant role in this context. UK company Guided Ultrasonics Ltd. (GUL), London, commissioned TÜV SÜD Industrie Service to carry out certification of its ultrasound testing procedure. Following the assessment of the non-destructive testing procedure, the guided wave testing method for basic pipes was successfully certified in accordance with the relevant EU standard CEN/TR 14748:2004. 

"Exact knowledge of the possibilities and limits of every test method is of special importance. Without this knowledge, effective and targeted detection of potential defects would be impossible", explains Dr Robert Kauer, Head of Plant Optimisation at TÜV SÜD Industrie Service. The guided-wave procedure allows long lengths of pipework to be screened quickly and accurately from a single location while pipeline operation is in progress. 

Qualified accuracy

GUL's guided wave testing method is based on low-frequency ultrasonic waves which are guided into a pipe where they propagate along the pipe axis in the pipe wall. The guided waves are reflected by certain characteristics in the pipes, including welds or changes in cross-section. The echo plot may uncover defects and enable targeted measures to be initiated, including follow-up measurements for exact quantification of the defect. The measurements require a large volume of data to be evaluated in a qualified manner. To do so, inspectors need professional education and training, must proceed methodologically and have extensive experience. Advantage in practice: the guided waves method is a tool that permits long pipe sections to be screened with qualified accuracy.

Successful certification of the guided wave testing method for basic pipes is the basis for its reliable application in the future. "As the qualification of the test method is now documented in a transparent and traceable manner, aspects such as the sizes and types of defects that can be reliably detected by the system are now clear."