GWUTGuided Wave Ultrasonic Testing (non-destructive testing)
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* Finding a PHMSA "no objection" path for cased pipe still represents a concern since both DA and ILl sometimes present interpretation difficulties and GWUT even with the 18 points does not always receive a "no objection" from PHMSA.
Two emerging technologies were initially evaluated as being suitable for the objectives defined by the company, EMFL and GWUT. It was also understood that GWUT is a screening tool that provides a general condition assessment.
Accordingly, the reduction of access costs is an important lector in favor of the GWUT technique.
The GWUT system employs low frequency (typically under 200 kHz) guided waves, operating just above audible frequencies, propagated from a ring of transducers fixed around the pipe.
The GWUT system is able to detect and to distinguish between symmetrical and flexural waves and both types are displayed.
On the other trend, the GWUT inspection revealed cases of external (soil) corrosion at the buried underground pipes and also at those bare sections that slipped off their supports and stayed in contact with the soil.
While there is no one technology that can cover all inspection situations, GWUT coupled with CIS and other emerging technologies, will be important tools in maintaining any pipeline integrity program.