Non-destructive testing/ NDT:

It can be performed on any test object without causing any damage to the test object. Whatever object is tested that will not damage during NDT testing. That object will remain the same. It will neither alter nor change. It is done to check the usefulness or serviceability of the test object. Whether the test object is useful or fit for that particular job or not. NDT is done to check these characteristics. Basically, with the help of  NDT, we check the absence of any discontinuity in the material. This is the basic aim of NDT.  Along with checking discontinuity, some other characteristics of the material can also be checked such as the size and dimension of the object, configuration of the object, hardness of the object, alloy content, and can check the grain size also with the help of NDT.

It is also known as Non- destructive examination, Non-destructive evaluation, and Non-destructive Inspection.NDT testing is one of the fastest-growing technology or fields and it has grown a lot in the last 25 years and is still growing in industries. With the help of NDT we can check the usefulness and soundness of metal at any stage like before fabrication, during the manufacturing, finished goods after fabrication, and during service. It is used to check the object in all stages.


  1. Visual testing(VT)
  2. Magnetic particle testing
  3. Radioactive testing
  4. Ultrasonic testing
  5. Eddy current testing
  6. Thermal infrared testing
  7. Acoustic emission testing
  8. Liquid penetrant testing

Visual testing is done by a normal human eye. A person is trained to do this test. This person can use something like a torch, magnifying glass or some other gauges. It is the most commonly used testing method  in industries. There is a possibility of flaws in this method. There are some discontinuities which can be detected using this method like corrosion, cracks and misalignments of parts.It is a time saving method.  Magnetic particle testing is used to detect the breaking or crack in ferromagnetic materials using magnetic fields. It is only used to check the surface and close surface of  ferromagnetic materials. With the help of this test, you can check the surface and sub-service of the material. It is relatively a low cost test. It can be used to evaluate irregular shapes easily. It may require de-magnetization in certain situations.

The basic principle of Liquid penetrant test or penetrant testing is capillary action. It is only limited to the surface. It has a wide applicability like it can be applied on any material. It can be used on any geometric shapes. It is only applicable to non-porous surface material. Due to its multi-process, it is a time consuming method. There is no recoverable data in this method.  In Ultrasonic tests a high frequency sound energy is used. The frequency of sound energy with more than 20000 hz is used. It is reliable and can detect the critical defect. It can also penetrate the internal structure. It is not good on rough, small or thin materials. It is necessary to clean or prepare the surface before doing this test.

Acoustic emission testing has been used in the engineering field for a long time. It detects the ultrasonic wave when the material is fabricated under the stress. It is a non-invasive method. It is slower than many other NDT techniques. Some of the tools and material are used in NDT like thickness gauges, flaw detectors, material condition testers, eddy current instruments, dye penetrants, other devices that measure the conductivity, resistivity and corrosion in materials. It also depends on the NDT method you are using. It is the most effective way to save our time and money. It is used in many industries like construction, engineering, air, space, rail, and other power and energy companies.

It helps to enhance the onsite safety. It also helps to determine the structural assets of your goods without causing any damage to it. It is usually a cost-effective method. The plant inspection industry uses the NDT method which helps to save time, money,and is also helpful in research and troubleshooting. It will enhance the plant and equipment safety. It will also enhance to prevent the loss of productivity in unplanned downtime.

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Christophe Rude

Christophe Rude

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