Pipeline Girth Welds Inspection Using Automated Ultrasonic Testing (AUT) with Zonal Discrimination – Simulation of POD Curves Using CIVA Software

摘要

The inspection of pipeline girth welds can be performed by automated ultrasonic testing systems composed of several channels (different transducers or multi-element probes with a set of different focal laws). These systems allow, with a single scan along the circumference of the pipe, a complete examination of the weld using the zonal discrimination approach. However, the use of these systems is subjected to the demonstration of their performances confronted to realistic degradations of their environment. This demonstration is synthesized in a qualification dossier and is supported by experimental sensitivity analysis to several influencing factors (pipe temperature, error in the positioning of the sensors…) and POD curves determination. This requires a large amount of experiments. In order to reduce the cost and time required today to determine a POD curve for a given inspection method simulation can be used. Simulations of typical girth welds inspection configurations using CIVA software are performed. Many influencing factors can be taken into account in CIVA such as the material and geometry of the specimen, the location, orientation and geometry of the flaw, the orientation and the position of the probe compared to the weld and the pipe temperature. Uncertainty propagation is performed using a Monte Carlo sampling strategy to get POD curves. In accordance to the DNV recommended practices a cumulative lognormal distribution is used to approximate POD curves based on Hit/Miss data. Purely numerical POD curves can therefore be obtained for a single channel and for the global inspection system. The whole computation scheme to get the numerical POD curves using CIVA software and its dedicated POD module is presented.