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Non-destructive testing (NDT): application, advantages and types

September 22, 2025
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Non-destructive testing     (       NDT     ) encompasses a range of techniques for evaluating materials, components, and structures without causing irreversible damage. These techniques are     used in industries such as oil and gas, aerospace, automotive, construction, and energy to detect defects, cracks, corrosion, and other integrity issues.

This article  explains      the various non-destructive testing techniques, their advantages and disadvantages, and their areas of application     . This information is useful for engineers, technical inspectors, and students of materials science and mechanical engineering.

1. The importance of non-destructive testing (NDT)

Non-destructive testing is crucial in industry for the following reasons:

  • Reduce costs:      Avoid damaging valuable components during inspection.

  • Increased safety:      Detect hidden defects before accidents occur.

  • Quality control:      Ensuring that products meet industry standards.

  • Structural health monitoring:      checking the condition of pipes, bridges and pressure equipment.

2. Types of non-destructive testing methods

2-1. Magnetic particle testing (MPI)

  • Basics:      Use of magnetic fields to detect surface and subsurface cracks in ferromagnetic materials such as steel.

  • Application:      Testing of welds  ,  shafts and gears.

  • Features:      High speed, low cost, high accuracy in detecting small defects.

  • Disadvantages:      Only suitable for magnetic materials.

2-2.     Penetration Tests (PT)

  • Basics:      Use colored or fluorescent liquids to detect surface cracks.

  • Application:      Testing of aluminum parts, turbines and pressure vessels.

  • Features:      Simple, suitable for non-magnetic materials.

  • Disadvantages:      Allows detection of only surface defects.

2-3. Ultrasound examination (ultrasound)

  • Basics:      Emission of ultrasonic waves and analysis of their reflections to detect internal defects.

  • Application:      Testing of welds, bars and composite materials.

  • Features:      Ability to determine fracture depth with high accuracy.

  • Disadvantages:      Requires a qualified operator, application is limited to materials with irregular structure.

2-4. X-ray and gamma (RT) studies – Radiological studies

  • Basics:      Using X-rays or gamma rays to create an image of the internal structure of a part.

  • Application:      Testing of welds in storage tanks and oil and gas pipelines.

  • Features:      Accurate representation of internal defects.

  • Disadvantages:      radiation risk and high costs.

2-5. Eddy current testing (ECT)

  • Operating principle:      Generation of eddy currents in conductive materials and measurement of changes in the electromagnetic field.

  • Application:      Inspection of turbine tubes and blades and detection of small cracks.

  • Features:      Fast, no direct connection required.

  • Disadvantages:      Only applicable to conductive materials.

2-6. Acoustic emission test (AE)

  • Key concepts:  Detection of  sound waves emitted by materials under pressure.    

  • Application:      Monitoring of high-pressure vessels and large structures.

  • Features:      Ability to detect defects during operation of the part.

  • Disadvantages:      Requires sophisticated equipment and complex data analysis.

3. Comparison of non-destructive testing methods

Test method Detection depth Materials for review It’s worth it accuracy
Magnetic particles (MP) above and below ground Ferromagnets A little higher
Permeability (PT) Only the surface All materials A little half
Ultrasound examination (ultrasound) local Metal   and plastic half very large
X-ray (RT) local Most materials higher higher
Eddy current (EC) above and below ground electrical conductors half higher
Structure-borne sound (AE) local supporting structure higher half

4. Application of industrial non-destructive testing

  • Oil and gas industry:    Inspection    of pipes, tanks and welds.  

  • Aerospace:     Inspection of turbine blades,   aircraft structures   and engines.

  • Automotive industry:      quality control in casting and welding.

  • Buildings:      Condition assessment of concrete and steel structures.

  • Nuclear energy:      Equipment for testing and ensuring reactor safety.

5. The future of non-destructive testing

With technological advances,  new methods such as intelligent non-destructive testing (using artificial intelligence and robotics)   and infrared thermal imaging     are being developed  to improve the accuracy and speed of inspections.

6. Conclusion

Non-destructive testing (NDT) is an important tool     for ensuring safety, reducing maintenance costs, and improving product quality     . The choice of the appropriate method depends     on the type of material, the nature of the defect, and the environmental conditions  . Combining multiple NDT methods can yield more accurate results.

Source:

  • American Society for Nondestructive Testing (ASNT)

  • ISO standards for non-destructive testing

  • Articles on mechanical engineering and materials science

If you need advice on selecting the right method, please contact a non-destructive testing specialist.