Qualification of Advanced Ultrasonic Testing According to Various Guidelines

This story starts in the early nineties when the NDT world was changing considerably due to the results of the PISC Programme (Program for the Inspection of Steel Components) and other studies worldwide. It was in the same period that the Performance Demonstration Initiative (PDI) was formed by US Utilities to implement the performance demonstration requirements of the ASME Code, Section XI, Appendix VIII . Meanwhile in Europe, ENIQ was brought to life as the importance of the issue of qualification of NDE inspection systems (procedures, equipment and personnel) used in ISI programmes for nuclear power plants was identified.

It is with these programmes in place that NDT companies had to qualify their procedures and personnel according to the applicable codes. Each qualification, the one more challenging than the other, was an adventure on its own, not for the authors only, but for the whole team.

THE NINETIES

Although not a qualification, the results of the PISC III, Round Robin Testing on Austenitic Steel Testing of the R&D division of Vinçotte are to be mentioned as they had their influence on future qualifications. Stainless steel components of PWR primary circuit sections were inspected by mechanised examination using focussed TRL probes (Transmitter/Receiver Longitudinal wave). These procedures provided an excellent detection and low false call rate. In the mid nineties a RRT was organised by the Swedish utilities (Ringhals) for the examination of PWR pump casing welds, pipe to elbow welds and nozzle to primary pipe welds. 

The results of this RRT brought Vinçotte to a qualification at the utilities location, supervised by SQC (Swedish Qualification Centre). The procedures and personnel were to qualify on representative flawed samples, a full-scale pump mock-up with 2 pump casing welds and a pipe to elbow weld. A 7-axis robot carried the probes, fully submerged for accessing the welds from the inside. Hard work from all parties resulted in May 1997 to qualified procedures and qualified personnel. This qualification resulted in various examinations in the period of ’97 to ’99

ENTERING THE MILLENIUM

Entering the millennium came together with phased array systems. As the demand to replace radiography by ultrasonic examination increased, Vinçotte developed procedures in accordance with the ASME BP&V Code, Case 2235 for the examination of vessel welds during their fabrication stage. The simultaneous generation of TOFD and shear wave angle beams using phased array probes was extensively used in these procedures. These procedures were qualified and witnessed by Lloyds representatives in various European countries. Over the years to follow, these procedures were updated each time the Code Case 2235 was revised. 

Similar ultrasonic techniques were used to elaborate a procedure for the ISI of steam generator vessel welds. This was qualified for the Belgian utilities using an ENIQ approach. A few flawed samples were used to demonstrate the performance of the procedure and a technical justification was written to cover the full range of the procedure.

THE LAST FEW YEARS

The growing interest of natural gas as source of energy increased the demand for transportation and storage systems. LNG is stored in cryogenic tanks made of 9% Ni alloy, welded with high Ni contents (60-70%). To replace radiography by ultrasonic examination, Vinçotte developed a procedure using phased array probes. This procedure is in accordance with API620 appendix U. On different occasions this procedure was demonstrated and qualified on blind blocks to the satisfaction of the authorities. Since then, this procedure has been widely applied during construction of several gas terminal LNG tanks in Belgiu m, Canada and The Netherlands.

CONCLUSIONS

As the demands on the NDT examinations varies by type or complexity, it is important for the NDT company to be flexible and able to develop procedures that satisfies the demands. It will take to long to list all qualification and validation activities that Vinçotte was involved in, but over viewing the previous paragraphs somecommon points were always present.

• Each qualification was performed with a dedicated team with a well-defined hierarchy, from project manager to mechanical scanner operator, all having the same goal in mind: a successful qualification.
• The selection of reliable dedicated equipment.
• Being sure that backup equipment and trained personnel were available at all stages of the qualifications.
• The development of detailed procedures for the acquisition and analysis of ultrasonic data.
• Dedicate training of personnel with a “failure is not an option” commitment.

 
 source : http://www.vincotte-ndt.com/data/engels/2010_Qualification_of_advanced_ultrasonic_testing_according_to_various_guidelines.pdf