GUEUGNAUT Dominique, ANGELINI Florent, BOUJLAL Adil, BOUAFFRE Romuald, SEVRE Bertrand, LOUET Patrick
Papers # 2014 Chicago
Polyethylene (PE) is a widespread material for the manufacturing of gas and water distribution pipelines and a large number of PE electrofusion pipe joints can be found over the thousands of kilometres of PE pipeplines all over the world, thus generating an increasing interest in checking the quality of these joints. No current operational Non Destructive Examination (NDE) technique to date has been adapted to inspect the small diameter electrofusion joints (i.e. 20mm-to-63mm) which are frequently encountered in particular on the French gas distribution networks.This paper aims at evaluating the acuity of the ultrasonic phased array technique (PA UT) for detecting the faults in 63mm electrofused joints prepared in laboratory. For that purpose some calibrated defects – consisting in thin adhesive strips – were integrated voluntarily at the interface between a 63mm pipe and a tapping saddle. Both the quantity and the distribution of these faults were modulated in order to meet or to violate the acceptance requirements of the ISO 13956 standard. Once the electrofusion welding made, the overall assemblies were scanned by means of PA UT. First, the number of detected strips with regard to the actual number of integrated sheets was compared. Second, a blind reverse dimensioning of the strips was obtained from the basis of the PA UT signals. Afterwards the welded assemblies were mechanically tested up to decohesion in accordance with the peel test condition as described in ISO 13956. Then the results of the PA UT evaluation and those of the destructive tests were confronted in order to evaluate the degree of correlation between both techniques. For the quantitative analysis of the results the notions of Power Of Detection (POD) and False Call Rate (FCR) were successfully used. POD values in the range of 85% to 100% associated to zero-FCR values confirm the very high level of reliability of PA UT for the selected test configurations.