Ultrasonic Inspection Techniques for a Range of Materials and Industries

Non-destructive testing (NDT) instrumentation was developed in the early 1900s. Since then, NDT technology has formed the basis for modern flaw detection across many industries. Rapid advances in technology have allowed NDT methods to be tailored to fit specific industrial inspection requirements. For ultrasonic testing (UT), this advancement has come in recent years as a powerful data acquisition and imaging technology.

A traditional ultrasonic inspection method utilizes high-frequency ultrasonic waves to transmit through a single transducer onto the material for the purpose of flaw detection. The process is extremely effective when it comes to the identification of corrosion, cracks, pitting, and other types of flaws. Additionally, the ability of UT to be utilized with a wide range of materials makes it the foremost NDT choice for a wide range of industries. Different methods of UT can have a major impact on safety, productivity, and quality control in a wide range of industrial applications as discussed further.

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Advanced Ultrasonic Inspection Techniques

In industries like aerospace, automotive, manufacturing, and petroleum, ultrasonic inspection has been trusted for its reliability in flaw identification. The advanced UT probes and instruments are suitable for inspecting complex geometries such as bends and curves, providing volumetric coverage and consistent results with ease. The ability to scan both metallic and non-metallic structures also makes ultrasonic inspection techniques one of the most flexible options compared to other NDT methods. The flexibility, excellent data processing capabilities, and greater inspection speed of UT equipment facilitate industries to leverage greater value for the initial investment.

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To further increase the value of the UT inspection method by ensuring greater precision, coverage, and productivity, many ultrasonic inspection techniques have been explored.

Phased array ultrasonic testing (PAUT) uses a series of several transducers on a single assembly that can be pulsed independently at different times to transmit and receive ultrasonic signals. The transducers can be pulsed at different times and the same mechanism can be utilized to optimize the focus and angle of the beam. This allows for the inspection of the material at different angles and focal points for flaw detection. This ability is beneficial in the inspection of complex geometries and varying material thickness for the identification of corrosion or erosion in a wide range of industrial applications. The use of multiple transducers also enables faster inspection, saving time and increasing productivity in the inspection.

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Time-of-flight diffraction (TOFD) is a highly reliable ultrasonic inspection technique that is predominantly used in weld inspections. As the name suggests, the technique uses diffraction for inspection purposes. The transmitter and receiver are placed on either side of the weld. As the ultrasonic beam is emitted from the transmitter, the irregularities present in the material or weld diffract the beam. The receiver on the other end collects the signal and analyses the response time of the beam to travel from the transmitter to the receiver. This technique has been successful in locating flaws and determining their size. Most technicians use this technique alongside PAUT for accurate flaw identification, mostly to get a detailed picture in applications like the inspection of pipeline welds.

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PAUT inspection is further enhanced by its advanced data acquisition methods such as full matrix capture (FMC). The multiple transducers used in PAUT can sometimes lead to raw signals being neglected in the analysis. FMC captures the A-scan—raw time-domain signals—from every possible transmitter-receiver combination, and analyzes them in real-time, or stores them for processing later. These signals, organized as a matrix grid, act as pixels in the image. For manufacturing, petroleum, or other industries, this data capture technique facilitates the characterization of flaws including corrosion, cracks, inclusion, and porosity.

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As discussed above, FMC captures the time domain signals and organizes them in the form of a matrix grid. This is made possible by using an advanced focusing algorithm, namely, the total focusing method (TFM). TFM computes the signals for every possible depth, angle, and focus, and arranges them in an array to generate a 2D or 3D image for in-depth detailing of the flaw present in the material for real-time or offline interpretation. Technicians can easily interpret the flaw and take informed precautionary measures to ensure the safety and productivity of the operation.

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Leveraging UT Testing for Various Industries and Applications

UT inspection has been an integral part of many critical infrastructural projects. In the petroleum sector, the effectiveness of UT can be seen during inspection of pipes, storage tanks, especially, welds and bolts for their strengths and effectiveness. The pre- and post-installation inspection ability of UT allows technicians to maintain safety and ensure component integrity through fast scanning and analysis for simple and complex geometries.

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In addition to the inspection of metallic pipes and components, PAUT with TOFD is equally capable of advanced flaw identification in high-density polyethylene (HDPE) piping. HDPE is used for its strength, corrosion resistivity, and service life. HDPE pipes can be prone to flaws such as lack of fusion, porosity, and inclusions, just like their carbon steel parts. The benefits of PAUT with TOFD can be leveraged to easily identify irregularities and detail the extent and positioning of flaws.

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In the aerospace and automotive industry, UT inspection can be a part of effectively testing composite materials that these industries are increasingly adopting. Ultrasonic testing techniques such as PAUT can effectively examine components such as rods, tubes, or plates made of composite materials with excellent accuracy and without any resistance.

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Advanced UT Inspection Solutions

The innovation and advancement in ultrasonic inspection techniques have made it a primary choice for NDT inspection in many industries. With advanced UT solutions, it is now much easier for industries to meet a wide range of inspection needs to ensure safe operation through flexible scanning, high-resolution imaging, and precision in testing.

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Zetec has been a leading provider of ultrasonic testing equipment and solutions for decades. To learn more about using ultrasonic technology in your industry, contact Zetec today.