What is Non-Destructive Testing (NDT) – Process, Types and Applications 

Non-Destructive Testing (NDT) – Process, Types and Applications 

Testing is crucial in every stage of production, ensuring the final product meets design specifications. There are various testing methods, including destructive and nondestructive testing. Non-destructive testing, also known as non-destructive inspection, analysis, and assessment, does not alter the product’s structure or characteristics. It is suitable for both new and in-service equipment.

Non-destructive testing is more efficient in terms of time, waste, safety, and result reliability. It doesn’t ruin the sample and can identify problems in running gear before failure, saving on breakdown costs. It doesn’t necessarily require taking items out of service, which can be a time saver. Destructive testing can ruin a product beyond repair, but NDT can achieve the same or better objectives.

Safety is another key benefit of NDT. It helps identify worn components or products and reduces the frequency of safety incidents. Results reliability is similar between destructive and non-destructive tests, as only a small number of samples can be tested with destructive testing. Non-destructive testing makes it easier to find discontinuities and faults in a part.

Visual inspection is a widely used non-destructive technique for identifying flaws in materials, such as corrosion, cracks, and welding faults. It is portable, effective, and inexpensive, with minimal preparation required. However, it is only effective for superficial flaws and may not be sensitive enough to detect minute flaws without specialized optical equipment. Ultrasonic testing, which uses a high-frequency sound wave to detect irregularities in material density, is also widely used. It is clean, reliable, portable, secure, and simple to employ. However, it requires specialized training, requires a flat, even surface, and can be problematic for thin materials.

Penetrant testing with a liquid is another non-destructive technique for finding surface flaws. It uses a low viscosity liquid to seep into surface flaws, allowing for a wide variety of materials and detecting minute flaws. It is adaptable to intricate geometry requirements, has value for money, and is portable. However, it cannot determine the depth of faults, is dangerous, and requires working with potentially dangerous substances.

In conclusion, visual inspection, ultrasonic testing, and liquid penetrant testing are all methods used to evaluate product quality.

Radiology and magnetic particle testing are two methods used to examine components for hidden flaws. Radiology uses X-rays to detect flaws in thin materials, while gamma rays help detect flaws in thicker materials. Radiographic testing allows for detailed examination of intricate structures, minimal surface preparation, and documentation of visible and invisible flaws. However, it is more expensive and requires skilled workers for proper implementation.

Magnetic particle testing is a nondestructive method that uses magnetic fields to detect flaws in components. The specimen is sandwiched between two magnets, with a stronger field yielding better results. Magnetic particles can detect flaws as narrow as 0.001 mm and as deep as 0.01 mm, detecting cracks, pores, laps, inclusions, seams, laminations, shrinks, flakes, welding flaws, machining tears, and service-related or fatigue cracks.

Magnetic particle testing is simple to implement, mobile, extremely sensitive, and has low costs. It can penetrate light coatings and complexly shaped components and visually see the flaw’s shape and magnitude. However, it can only examine localized regions, is not applicable to non-magnetically charged materials, and requires demagnetization of test specimens.

Eddy current testing is a form of electromagnetic testing that uses the electromagnetic induction concept to create an opposing electric current in a test specimen. This current, known as eddy current, is proportional to the variation in the magnetic field caused by the rising and falling of the alternating current in the primary coil. The strength of the eddy current varies with the magnetic permeability and electrical conductivity of the test specimen, which are affected by the presence of defects.

Remote field testing is another option for finding flaws in steel pipes and tubes. Eddy current testing has several benefits, including quick, portable, rapid effects, minimal pre-work, hands-free operation, and the ability to detect flaws as small as 0.5 mm. However, it has a high penetration depth and is only applicable to materials that carry electricity.

Nondestructive testing (NDT) is used for various purposes, including quality assurance and condition monitoring. NDT can be used for a variety of structures, civil engineering, and welding processes. Examples of NDT uses include ultrasonic testing, radiographic testing, visual testing, acoustic emission testing, terrestrial laser scanning, photogrammetry, tacheometry, and infrared thermography.

In medicine, NDT technologies like ultrasound imaging, radiography testing, and echocardiography are used to diagnose and treat defects in medical implants. In conclusion, NDT is rapidly replacing destructive testing as the standard for quality assurance across all industries.

Video 01: Introduction to Non Destructive Testing of Concrete – Advanced Concrete Technology