Application Note

Ultrasonic NDT Corrosion MappingFrom Phased Array to FMC-TFM

• Oil and gas• Power generation

• Pipeworks• Tanks• Pressure vessels

• Phased array• L-scan (linear scan)• FMC (full matrix capture)• TFM (total focusing method)• Automated or manual

Features and Benefits• High resolution (down to 0.1 mm2)• Large TFM images

(up to 1024 x 1024 pixels)• Complete inspection recording

traceability (FMC)• Apertures of up to 64 elements• Easy-to-use sizing tools• Large memory capacity (120 GB SSD)• Exportation in the CSV format

Recommended Tool Package• Veo+ 16:64 PR (FMC/TFM option)• UTStudio+ software

and• WheelProbe 2 corrosion package

or• D5A-5M64E-0.8x12 probe• D5-CABLE-S-QX2 cable• D5AW-0L12.7-IHC wedge• X-Clamp, ODI, or C-Clamp encoder• JX-CMA013 couplant pump• 4-mm ID irrigation kit

Typical Parts

Inspection Techniques

Industries and Markets DescriptionCorrosion inspections are used to evaluate the remaining wall thickness or the presence of mid-wall anomalies in pipeworks, pressure vessels, and other metallic structures. These inspections have always been at the heart of many problematic situations for production, maintenance, and integrity considerations because of the safety and costs issues. Such material degradation can cause many problems to the industrial and civil infrastructures.Mapping the corrosion affecting those infrastructures consists in creating a grid of data collected over an area affected by the problem. Sonatest, with 60 years of experience in ultrasonic NDT, is able to provide different ultrasonic solutions to perform an effective corrosion map.While a conventional UT beam can report one thickness at a time, phased array scans can produce a very accurate and high-resolution collection of thicknesses. Phased array, nowadays, is considered the fastest and most affordable advanced ultrasonic NDT inspection technique that is code compliant. To complement this solution, Sonatest also offers new technologies such as the FMC-TFM imaging that improves even further the resolution of the inspection readings.With the Veo+ instrument, Sonatest provides one of the best portable multiscan phased array solutions in the world. Now, with the new FMC-TFM software option, it offers a wide range of corrosion mapping solutions, making the Veo+ a smart and long-lasting asset for the NDT professionals.

Figure 1 Recommended tools

Veo+

WheelProbe 2

Encoder

Phased array probe

Phased Array Corrosion MappingWith 64 elements (WheelProbe 2 and DAAH D5A probes), these large probes are designed to cover wide areas. They have been engineered to use focal laws of 8 elements. Consequently, the linear scan (L-scan) offers a very high density coverage. The WheelProbe 2 can inspect metal sheets as thing as 1 mm because of its exceptional near surface resolution (10 MHz for instance). The delay line for the 2 solutions provides excellent results on steel parts of up to 3 inches thick.On the instrument side, the Veo+ offers a versatile user interface that allows the user to get the right information to properly detect and evaluate a defect. A typical layout should have:• One scrolling C-scan view to continuously show the last 100 mm (4 in,) scan in a

scrolling window.• One L-scan and one A-scan view to setup the triggering gate (IFT) and monitor

the back wall echo (G1).• Two merged C-scan views to show the amplitude and depth readings for a good

image of the inspection.

The combination of the Veo+ and phased array probes provides a resolution of 0.8 mm, which makes it a high-resolution corrosion mapping application. Other advantages of the Sonatest solution are:• Fast recording (up to 300 mm/s or 12 in./s)• Light and traceable ultrasonic inspection data (<1 GB)• Fast and easy rejection and approval evaluations• PA certified technicians are available, making the solution affordable

FMC-TFM Corrosion MappingWhy? When?Phased array alone is efficient for most of the corrosion mapping applications (95% of the time). For critical applications, which represent the remaining 5%, the combination of the FMC and TFM imaging is ideal for record-keeping compliance and provides a resolution of up to 0.1 mm2 regardless of the probe pitch and zone size (up to 1024 pixel2). Because the beams are focused at all points, the precision of a TFM image enhances the defect profile no matter what the geometry.Figure 2 shows the results for a 6-mm round bottom hole that has been found twice and has the same dimensions for both phased array and TFM techniques. It is clear that the TFM shows more information about the contour and round shape of it, which highlights the high-resolution and profiling advantages of the TFM imaging technique.

Veo+ Multiscan Phased Arrayand FMC-TFM SolutionWith the FMC scan activated, the Veo+ handles up to 2 scans at the same time. One advantage is that the technician can record the FMC and the L-scan at the same time to generate a dual technique inspection of the region of interest. To do so, the Veo+ includes multiple layouts to help the user configure the FMC andL-scan setup. Similar multiscan layouts are also available once FMC scans havebeen converted into TFM scans for analysis.

Figure 2 Phased array (left) vs. TFM (right)

Figure 3 Example of L-scan and FMC layout