Dominique GUEUGNAUT, Florent ANGELINI, Romuald BOUAFFRE, Manuel TESSIER
Papers # 2016 Berlin
A test campaign has been carried out by ENGIE Lab-CRIGEN in order to evaluate the acuity of the Phased Array Ultrasonic Technique (PAUT) for detecting and sizing calibrated defects implanted at the inner surface of a PE pipe.These calibrated defectshad four different geometries, called “V-shaped”, “half-V shaped “, “semi-elliptical”and “rectangular”, respectively. They were machined at ten increasing depths on the internal wall of four half-shells from a 110 mm PE100 pipe. The heights of the defects, as evaluated by PAUT, were compared to those measured on replicas using the diagnostic impressioncasting kit developped by CRIGEN. The 40 calibrated defects implanted in the pipe halfshells have been detected by the PAUT examination, including those with the smallest heights corresponding to 2% of the pipe thickness, which brings the POD to 100%.
The last ten year literature shows that the phased array ultrasonic technique (PAUT) is one of the most promising technique for detecting and – under certain conditions – for sizing the faults in both the electrofused joints and the butt fused joints.
More recently some attempts have been done to evaluate the acuity of such a technique for detecting the faults in plain pipes. In this area, ENGIE Lab-CRIGEN presented some preliminary results during the Plastic Pipes XVI. These results showed the efficiency of the PAUT for detecting both a localized or a widespread damage in pipesartificially notched or pressurized under hydrostatic pressure test conditions. Given these encouraging trends, it was decided to launch a systematic program in order to validate the results in other test configurations with the final objective of an accurate sizing of the faults. For that purpose four different faultgeometries have been chosen and machined at theinner surface of a 110 mm PE pipe. The faults were a “V-notch”, a “half V-notch”, a rectangular notch and a semi-elliptical notch. This latter fault was chosen in order to simulate an increasing longitudinal crack in the pipe wall thickness during slow crack growth. Each fault was implemented by indentation with specific shaped tools at ten different depths in the pipe. The fault profiles were controlled by means of a diagnosticimpression-casting technique designed by CRIGEN. PAUT evaluation was made from the outer pipe surface. The profiles obtained by both the imprint technique and the PAUT evaluation are then compared on a quantitative level in terms of both probability of detection (POD) and dimensions.
