LATITUDE: A First-of-A-Kind NDE Innovation from SI

The first PDI qualified manually-encoded DM weld procedure

In News and Views Issue 43, we introduced LATITUDE™, a revolutionary non-mechanized position and orientation encoding technology that is designed for use with nondestructive evaluation (NDE) equipment. The Latitude system, when coupled with an NDE data acquisition system, allows an operator to acquire high-quality encoded data using a manual examination process. Fast-forward a mere five months and Structural Integrity (SI) is pleased to announce that it has qualified the first ever manually encoded phased array UT procedure for the examination of dissimilar metal welds (DMWs) in nuclear power plants. The procedure qualification was administered by the Electric Power Research Institute (EPRI) in accordance with Performance Demonstration Initiative (PDI) requirements.

This procedure, along with the use of LATITUDE, allows SI to provide several advantages to its clients. They are as follows:

The use of SI-UT-217 and LATITUDE provides a faster-encoded examination than currently available qualified procedures. This technique significantly improves the production rate for acquiring encoded data by employing a novel manual scanning technique and by eliminating the need for cumbersome and complicated automated inspection equipment. Time for in-processing, scanning, transportation between welds, and out-processing are all reduced;

The number of personnel required to deploy this procedure is minimized. LATITUDE has fewer parts and set-up is simpler when compared to automated inspection equipment. The LATITUDE system is compact, arriving on site in a few transportable ruggedized cases and operates entirely on battery power;

The total amount of equipment needed to deploy SI-UT-217 in containment is drastically minimized. The total system (see Figure 1) is comprised of a Topaz phased-array UT instrument, and a LATITUDE system, probe, and collar. This reduced equipment size lowers the overall risk and cost associated with decontamination. Compared with an automated setup, the amount of equipment brought to the site to deploy SI-UT-217 is drastically reduced;

The overall cost and potential dose impact to the plant are reduced. Additionally, experimental data collected on DMW practice samples showed that manual scanning (i.e., scanning by hand) often yielded higher-quality data than automated scanning. This is illustrated in Figure 2, which shows a comparison of manually-acquired data using the LATITUDE system with automated data acquired on the same sample. The comparison shows an appreciable improvement in the signal-to-noise ratio for the manually-acquired data, which is especially important for this sample because it contains one of the most difficult flaws in the practice sample population. In Figure 3, a similar comparison is shown for axial flaws in another practice sample.

This improved fidelity is believed to be a result of superior probe coupling that is inherent to manual data acquisition. Although automated data acquisition systems have provisions for maintaining probe coupling, they cannot replicate the tactile adjustments of the probe that the human hand can make in response to hoop shrinkage and other imperfections in the surface conditions. Per the 2017 EPRI Technical Report entitled Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds, Revision 2, operational experience noted surface condition as a key determinant of data quality and cited poor surface conditions and inadequate probe coupling/contact as causes for missed detections when performing ultrasonic examinations on dissimilar metal welds. Another cited cause of missed detections was the absence of encoded data (i.e., when a manual, non-encoded examination was performed) that resulted in missed detections of five significant flaws; two of which were identified by leakage after a machining operation. The LATITUDE system can mitigate both issues by facilitating improved probe coupling via manual data acquisition, while still providing the same permanent data record given by automated data acquisition.

The procedure, SI-UT-217, is a raster technique and is qualified for diameters 11.8” and greater, component thicknesses ranging from 0.86” to 2.94”, and has been qualified by demonstration in accordance with the requirements of the ASME Boiler & Pressure Vessel Code, Section XI, Appendix VIII, as modified by the PDI program description. This procedure additionally meets the requirements of 10 CFR Part 50.55a, Codes and Standards. It is important to note that the procedure is qualified for the detection and length sizing of circumferentially and axially oriented flaws in the qualified DMW configurations, where single or dual side access is available.

SI-UT-217 brings to the market an innovative approach to examining piping welds in a nuclear power plant. The ability to quickly deploy and acquire encoded results in an expedited manner will help plants stay competitive in an ever-changing market. Future development efforts for SI-UT-217 and LATITUDE will involve qualifying and adding small bore DMWs and complex geometries to the procedure as needed. Other non-PDI focus areas will include ASME Code UT examinations, FAC examinations, and other internal corrosion mapping applications for feedwater heaters, service water piping, tanks, and other BOP-related assets.

 

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