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Eddy Current Reduces Inspection Time

June 4, 2009
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Increase inspection productivity with eddy current array technology.

Eddy current array equipment can be used for different inspection needs. Source: GE Sensing & Inspection Technologies


Advances in technology are helping the nondestructive testing industry become more efficient and accurate. New technologies have resulted in equipment that is easier to use and improves inspection time without sacrificing accuracy. Eddy current array is a prime example of how eddy current technology has evolved and, as a result, improved inspection techniques beneficial for inspectors in aerospace and automotive industries, power generation, and oil and gas.

Eddy current array and conventional eddy current technology share the same basic principle, but the differentiator with eddy current array is multiple coils, or sensors, and multiplexing. Where conventional eddy current drives coils in a series of single points in a straight line, eddy current array technology electronically drives multiple coils in the same probe assembly, and data is generated by multiplexing the eddy current coils in a specific pattern. The array is critical to improving inspection time and achieving better results because the array method increases the area being inspected at one time while keeping the high resolution of a conventional eddy current probe.

Eddy current array multiplexers can be used with an array of coils to scan larger surfaces with extreme sensitivity. The data from each coil can be saved individually so all the information is accessible. The array also can be shaped to follow the profile of the part. Each coil in the probe can be used in a variety of inspection modes: absolute for high-resolution inspections, differential to account for rough surfaces, or transmit-receiver for complex shapes. It is possible to use eddy current array technology practically anywhere conventional eddy current probes are used to improve the inspection speed.


The probes used during eddy current array testing are important to achieving accurate results. Source: GE Sensing & Inspection Technologies

Benefits

One of the key benefits of the eddy current array method is the reduction of inspection time. Where traditional eddy current testing is linear, the array allows a much wider span for inspection. The images gathered are displayed using a ‘top view’ or C-Scan image, making interpretation easier and quicker than the single point images generated by the conventional eddy current method. The C-Scan imaging also allows for more accurate flaw detection by providing a clearer view of the actual size and location of the flaw. As with traditional eddy current technology, the surface preparation is minimal and inspection can be done without direct contact, or any liquid coupling or penetrant.

Single pass coverage also is a benefit with eddy current array. Flaws can be detected in a single pass, increasing inspection speed and extending the life of the probe being used. Also, with eddy current array, a manual scan often is enough to check for flaws. This reduces the need for robotics to move the probes, which saves both time and money.


The benefits of traditional eddy current inspection have grown with eddy current array, where larger areas can be tested in less time with greater accuracy. Source: GE Sensing & Inspection Technologies

Eddy Current Array Probes

The probes used during eddy current array testing are critical to achieving accurate results. High-quality arrays are necessary to achieve high-quality results; without them the data gathered may not be as reliable and the integrity of the inspection results can be put in jeopardy.

Several factors must be considered when specifying the key parameters of the array probe. The starting point is having a clear definition of the application.

Key application parameters must be defined:

  • The type of material to be inspected has a strong influence on array inspection frequency.
  • The size of the minimum defect to be detected will dictate the coil diameter and inter-coil spacing.
  • The location of the defect. Whether the defect is in the base material or on an edge will impact the coil diameter and necessary algorithms to process the inspection data and display the results.
  • Access to the inspection area will help determine the type of fixturing necessary to ensure consistent presentation of the eddy current array to the area of interest.
  • Surface finish of the part to be inspected will determine the type of high performance materials and adhesives for excellent abrasion resistance and long life.

    After the application is clearly defined, other key parameters must be taken into account including:
  • Desired productivity level or inspection speed.
  • Types of data output, display or image required to quickly and easily interpret the array inspection data.
  • Eddy current qualification level of the inspector.


  • Equipment and Probe Selection

    Quality eddy current array equipment can be used in multiplexed or simultaneous injection modes as well as context switching modes. With that flexibility organizations are able to use the equipment for different inspection needs.

    It also is important to examine the vendor as carefully as the equipment. Ask key questions: Do they offer a complete solution that would be beneficial? What type of support and service do they offer? A strong sales and service staff can help incorporate eddy current array into current inspection processes and help grow the system based on changing inspection needs. Choosing the correct equipment from the correct vendor is essential to successful inspection.

    Eddy current array technology is a great solution where speed and accuracy are needed. The benefits of traditional eddy current inspection have grown with eddy current array, where larger areas can be tested in less time with greater accuracy. From reduced inspection time to more accurate flaw detection, the benefits of eddy current array technology are powerful and can help increase the overall inspection productivity within a company. NDT


    Tech Tips

  • One of the key benefits of the eddy current array method is the reduction of inspection time.

  • The surface preparation is minimal and inspection can be done without direct contact.

  • Another benefit of eddy current array technology is more accurate flaw detection.


  • Dave Jankowski is business leader for eddy current at GE Sensing & Inspection Technologies (Billerica, MA). For more information, call (978) 437-1000, e-mail sensing@ge.com or visit www.gesensinginspection.com, http://twitter.com/GE_SensInsp, www.flickr.com/photos/36760597@N08/, www.youtube.com/GESensingInspection or connect with GE Sensing & Inspection Technologies on Facebook.

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