Nondestructive Testing Methods (NDT)

Definition - What does Nondestructive Testing Methods (NDT) mean?

Nondestructive Testing Methods (NDT) are a broad group of analytical methods used in industries and science in order to assess properties of metals, systems or components without causing damage. This form of testing does not change the item under inspection. This makes NDT one of the most valuable techniques in saving time and money in terms of troubleshooting, product evaluation and research.

Nondestructive testing is also known as nondestructive examination (NDE) and nondestructive evaluation (also NDE) as well as nondestructive inspection (NDI).

Petropedia explains Nondestructive Testing Methods (NDT)

The methods involved in NDT may depend on sound, electromagnetic radiation as well as other inherent properties of the sample under investigation. This may include some types of microscopy in order to study external surfaces very closely. The interior surfaces of certain samples can be put under investigation with the use of penetrating electromagnetic radiation techniques like 3D X-rays or standard X-rays intended for volumetric inspection. Sound waves are also used in instances of ultrasonic testing. The contrast that exists between the bulk and defect of a certain sample can be improved for visual test with the aid of liquids that seep into fatigue cracks, such as in the use of dyes on materials like metals.

In cases of weld verifications, the following process may be involved:

  1. A portion of the material with a crack on the surface that is not visible to the naked eye is chosen for inspection.
  2. The penetrant is dispersed into the surface. 3. Excess penetrant is eliminated. 4. Developer is then applied, making the crack visible to the naked eye.

Other than weld verification, NDT is also used in applications such as in the examination of materials, objects and other systems without damaging its future usefulness. Apart from the processes mentioned above, the following are the most common techniques:

  • Leak testing - used to locate or detect leaks existing in pressure vessels, containment parts and other structures.
  • Infrared testing - utilizes infrared imaging and thermography as well as a measuring camera to measure and see the infrared energy being released from a subject.
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