Industrial plants need to understand the condition of equipment without cutting it apart simply to inspect it.
Non-Destructive Testing, or NDT, provides techniques for examining materials and components while keeping them usable.
Different techniques reveal different types of defects.
Visual inspection may identify:
It is simple but extremely valuable.
Many integrity problems are first recognised visually before more specialised examination is used.
Ultrasonic testing uses sound waves to examine materials.
It is commonly used for wall-thickness measurement and can also detect certain internal defects.
Its usefulness depends on the geometry, material and type of damage being investigated.
Radiographic examination can reveal internal features using penetrating radiation.
It may be used for weld examination or other applications where internal discontinuities need to be identified.
Because radiation is involved, specialised controls and procedures are required.
Magnetic particle testing can be used on suitable ferromagnetic materials.
It is particularly useful for detecting certain surface and near-surface cracks.
The technique is not applicable to every material.
Liquid penetrant testing can reveal cracks or defects that reach the surface.
The penetrant enters the discontinuity and becomes visible during the inspection process.
It is widely used because of its relative simplicity.
There is no single NDT method that can detect every defect.
The correct choice depends on:
The inspection engineer needs to know what they are looking for.
Inspection data still requires interpretation.
A detected indication may need further assessment to determine whether it affects safe operation.
NDT therefore provides information for integrity decisions rather than replacing engineering judgement.