Promag

NDT
Techniques

Overview

NDT Techniques

Non-Destructive Testing (NDT) techniques are inspection methods used to evaluate the properties of a material, component, or system without causing damage. These techniques are widely used in industries such as aerospace, oil & gas, power generation, construction, and manufacturing to detect defects, ensure safety, and maintain product quality. NDT methods can generally be classified into two categories: Conventional and Advanced.

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Conventional NDT Techniques 12 Methods

AETIRLTPTETMPTRTUTVAVI

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Advanced NDT Techniques 4 Method Groups

ETLMRTUT

Conventional NDT Techniques

Conventional methods are techniques that have matured over the course of decades and in this time, have become well-documented in codes, standards, and best practices. The setup and procedure of a conventional technique is typically simpler in comparison to advanced methods.

Acoustic Emission Testing (AET)
Infrared Testing (IR)
Leak Testing (LT)
Liquid Penetrant Testing (PT)
Electromagnetic Testing (ET)
Magnetic Particle Testing (MPT)
Radiographic Testing (RT)
Film Radiography (FR)
Ultrasonic Testing (UT)
Straight Beam
Vibration Analysis (VA)
Visual Inspection (VI)

Advanced NDT Techniques

Advanced methods are typically less well understood, as they represent emerging technologies. Their advantages and limitations may not yet be fully established, technician qualification criteria may be lacking, and codification within industry standards is often minimal. In general, the setup, procedures, and data interpretation for advanced methods are more complex and require specialized knowledge and experience from properly trained technicians.Additionally, some methods can be classified into both conventional and advanced categories. For example, within ultrasonic testing (UT), straight-beam ultrasonic testing is considered a conventional technique used for simple applications, whereas phased array ultrasonic testing (PAUT) is an advanced UT method. As advanced techniques evolve and mature, newer and more sophisticated versions continue to emerge, creating an ongoing cycle of technical development and training requirements.

Electromagnetic Testing (ET)

Electromagnetic testing is a group of non-destructive testing methods that use electromagnetic fields to identify surface and subsurface discontinuities in conductive materials.

ACFM: Alternating Current Field Measurement. Uses an alternating current magnetic field conditioned to be homogeneous in undamaged areas.
Eddy Current (ECT): Uses one or more coils in various configurations to generate and detect eddy currents.
EMAT: Electromagnetic Acoustic Transducer. Utilizes electromagnetic induction to generate and receive ultrasonic waves in conductive materials.
Remote Field (RFT): Uses a probe placed inside a tube to generate a magnetic field that travels through the material.
Pulsed Eddy (PECT): Uses a pulsed DC magnetic field to generate eddy currents.

Laser Testing Methods (LM)

Laser testing methods use coherent light sources (lasers) for high-precision inspection and measurement. These methods are highly sensitive to surface and subsurface discontinuities, deformation, and structural integrity.

Holographic Testing: Uses laser holography to detect surface and subsurface defects by measuring changes in the interference pattern caused by stress, vibration, or heat.
Laser Profilometry: Employs laser scanning to create precise 3D surface profiles, allowing accurate measurement of surface geometry, roughness, and wear.
Laser Shearography: A non-contact optical method that uses laser interference patterns to detect subsurface defects and strain anomalies under stress loading conditions.

Radiographic Testing (RT)

Radiographic Testing is a non-destructive method that uses X-rays or gamma rays to examine the internal structure of materials, components, or assemblies. It is highly effective in detecting internal discontinuities such as cracks, porosity, inclusions, and voids that are not visible on the surface.

Computed (CR): Utilizes phosphor imaging plates that capture X-ray exposure and are later scanned digitally to produce high-resolution images.
Tomography (CT): Provides 3D visualization by reconstructing multiple radiographic images taken at different angles, allowing precise analysis of internal features.
Digital (DR): Employs flat panel detectors or CCD-based systems for real-time image acquisition, delivering faster inspection results and reduced radiation exposure compared to traditional film radiography.

Ultrasonic Testing (UT)

Ultrasonic Testing is a non-destructive method that employs high-frequency sound waves to detect surface and subsurface flaws, measure thickness, and characterize material properties. UT is widely used across industries due to its ability to provide precise, reliable, and quantitative results without causing damage to the component.

Angle Beam: Uses angled ultrasonic waves to detect flaws in welds and other critical areas where straight-beam testing is limited.
AUBT: Automated Ultrasonic Backscatter Technique. Detects intergranular stress corrosion cracking (IGSCC) and other fine cracks in complex materials.
EMAT: Electromagnetic Acoustic Transducer. Generates ultrasonic waves without direct contact or couplants, ideal for inspecting hot, rough, or coated surfaces.
Immersion Testing: The test object and transducer are submerged in a liquid (usually water), providing excellent coupling for high-resolution inspection.
IRIS: Internal Rotary Inspection System. Specializes in the inspection of tubes and pipes, particularly in heat exchangers and boilers.
Long Range (LRUT): Inspects large sections of pipelines from a single location, effective for detecting corrosion and wall thinning.
Phased Array (PAUT): Uses multiple elements and electronic beam steering to produce cross-sectional images of the component, enabling detailed flaw characterization.
Time-of-Flight (TOFD): Measures the time it takes for diffracted ultrasonic waves to travel around a flaw, providing accurate flaw sizing and depth measurement.