Non-Destructive Testing (NDT) – sometimes called Non-Destructive Inspection (NDI) or Non-Destructive Examination or Evaluation (NDE) – included a variety of techniques that are used to test the integrity of a material without damaging it. Since the original material is tested without damage, non-destructive testing is recognized by many industries as a highly valuable and cost-effective technique for ensuring the materials and parts they use are free of defects. In addition to evaluation and troubleshooting, many non-destructive testing techniques are used in research to improve materials and processes and increase overall operational efficiency.
Non-destructive testing methods have been used industrially for more than a century, beginning in the late 19th-century when a mixture known as “oil and whiting” was used in the railroad industry to identify small cracks in heavy metal locomotive parts. The oil and whiting technique is similar to modern liquid penetrant testing methods: parts were soaked in oil then painted with whiting powder. Oil that seeped from tiny cracks turned the white powder brown, making cracks easily visible.
Although non-destructive testing methods are used in many industries, including medicine (think of an x-ray or magnetic resonance imaging) and other scientific fields, the techniques are most widely used in industrial applications such as the petrochemical industry and other industries that rely on heavy machinery or components that must remain in place and functional before, during and after testing.
Types of non-destructive testing
Non-destructive testing comprises a variety of methods; the four most common are liquid penetrant testing, ultrasonic testing, radiography and magnetic particle testing. All of these methods can be used to evaluate nearly any component made of metal, making them very popular for industry use. The type of testing method used depends upon the material being tested, the training of the personnel performing the testing, available equipment and other factors. Since some methods involve more costly equipment, budget can also play a role. The location, size and position of the materials to be tested can also influence which methods can be used, since some rely on testing equipment that may be too large in specific environments.
Because the testing methods themselves do not destroy or otherwise impair the integrity of the part being tested, they are ideal for evaluating critical areas like welds and joints to identify stress fractures or tiny cracks that could cause equipment failure and even serious accidents in the future.
Oil and gas companies frequently use these methods to help ensure their pipelines are in good shape and not in danger of failure, especially after years of use involving heavy loads or high pressures. Because pipelines are difficult and expensive to replace when they become old, many are left in place for many years, increasing the risk that small defects may occur. Non-destructive methods can be used to identify tiny flaws like minute cracks that could cause a pipeline to fail, resulting in a leak or even an explosion, helping companies identify which components need to be replaced or reinforced.
Since they can be used to diagnose critical issues before those issues develop into serious problems, non-destructive testing methods provide an extremely cost-effective approach to safety testing and quality control, enabling companies in a variety of industries to take a more proactive approach in warding off dangerous problems that can impede operation, increase costs and cause property loss or even human injury.
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