(Frequently Asked Questions)
Certainly! Here are some frequently asked questions (FAQ) related to Non-destructive testing (NDT) and inspections:

What is Non-Destructive Testing (NDT)?

NDT is a technique used to evaluate the properties of a material, component, or system without causing damage. It helps in detecting flaws or irregularities in a non-destructive manner.

What are the common methods of NDT?

Common NDT methods include ultrasonic testing (UT), radiographic testing (RT), magnetic particle testing (MPT), liquid penetrant testing (LPT), eddy current testing (ECT), and visual inspection.

What are conventional Non-Destructive Testing Techniques?

Conventional Non-Destructive Testing (NDT) techniques refer to the traditional methods used for inspecting materials and structures without causing damage. These techniques have been widely employed for many years and remain fundamental in various industries.

Here are some common conventional NDT techniques:

Visual Inspection (VI)

Visual inspection is the most basic form of NDT. It involves a thorough visual examination of the surface of a material or structure to detect any visible defects, such as cracks, corrosion, or weld discontinuities. Visual inspection is often the first step in an NDT process.

Liquid Penetrant Testing (LPT or PT):

Liquid Penetrant Testing involves applying a liquid penetrant to the surface of a material. The penetrant seeps into surface-breaking defects, and after excess penetrant is removed, a developer is applied to make the defects visible. LPT is particularly effective for detecting small cracks, porosity, and other surface discontinuities.

Magnetic Particle Testing (MPT or MT):

Magnetic Particle Testing is used for detecting surface and near-surface defects in ferromagnetic materials. A magnetic field is applied to the material, and magnetic particles are applied to the surface. The particles accumulate at areas of magnetic field distortion, highlighting defects such as cracks..

Radiographic Testing (RT):

Radiographic Testing involves the use of X-rays or gamma rays to inspect the internal structure of a material. It is effective for detecting internal defects such as voids, inclusions, and cracks. RT is commonly used in industries like aerospace and welding.

Ultrasonic Testing (UT):

Ultrasonic Testing utilizes high-frequency sound waves to inspect the internal structure of a material. Ultrasonic waves are sent into the material, and reflections are analysed to identify flaws. UT is versatile and can be used for thickness measurements, flaw detection, and characterization of defects.

Eddy Current Testing (ECT):

Eddy Current Testing uses electromagnetic induction to detect and characterize surface and near-surface defects. It is commonly applied to conductive materials and is used in the aerospace industry, among others, for inspecting components like aircraft engine parts.

Leak Testing:

Leak Testing involves detecting the presence of leaks or fluid ingress in a sealed or pressurized system. Various methods, such as pressure decay testing and bubble testing, can be used to identify leaks.
These conventional NDT techniques are chosen based on the specific characteristics of the material, the type of defect expected, and the requirements of the inspection. While newer and more advanced techniques like Phased Array Ultrasonic Testing (PAUT) and Alternating Current Field Measurement (ACFM) have emerged, conventional methods remain essential and are often employed in combination for a comprehensive inspection.

What are advanced Non-Destructive Testing Techniques?

Advanced Non-Destructive Testing (NDT) techniques leverage cutting-edge technologies and methodologies to provide more detailed, accurate, and efficient inspections of materials and structures.

Here are some advanced NDT techniques:

Phased Array Ultrasonic Testing (PAUT):

PAUT uses an array of ultrasonic transducers to create and manipulate ultrasonic beams. This allows for enhanced control over the direction and focus of the beams, providing detailed imaging of internal structures and the ability to inspect complex geometries.

Time-of-Flight Diffraction (TOFD):

TOFD is an ultrasonic testing technique that measures diffracted waves to accurately size and locate defects. It is particularly effective for detecting and characterizing cracks, weld defects, and other discontinuities.

Computed Tomography (CT):

Similar to medical CT scans, industrial CT is used for 3D imaging of the internal structures of components. It provides detailed information about internal features, voids, and defects without the need for disassembly.

Digital Radiography (DR):

Digital Radiography involves the use of digital detectors to capture X-ray images. It provides real-time imaging and eliminates the need for film processing. DR is often used for inspecting welds and detecting internal defects.

Guided Wave Ultrasonics (GWUT):

GWUT utilizes low-frequency ultrasonic waves that travel along the length of a structure. It is particularly useful for inspecting long pipelines and other structures, providing coverage over large areas.

Eddy Current Array (ECA):

ECA involves using an array of eddy current sensors to inspect conductive materials. This array configuration allows for simultaneous detection of multiple flaws and provides detailed information about their size, shape, and orientation.

Terahertz Imaging:

Terahertz waves lie between microwave and infrared radiation and can penetrate materials like clothing, paper, and ceramics. Terahertz imaging is emerging as a non-destructive technique for inspecting composite materials and layered structures.

Advanced Digital Signal Processing (DSP):

Advanced DSP techniques are used to enhance the signal-to-noise ratio and extract valuable information from the signals obtained during inspections. This includes advanced filtering, signal analysis, and imaging algorithms.


Shearography is an optical NDT method that measures surface deformation caused by internal defects or stresses. It is used for detecting defects in composites, adhesive bonds, and other materials

Infrared Thermography:

Infrared thermography measures the infrared radiation emitted by an object's surface to detect variations in temperature. It is valuable for identifying defects such as delamination’s, voids, or water ingress in composite materials.
These advanced NDT techniques offer improved sensitivity, faster inspection times, and greater accuracy compared to conventional methods. They are often chosen based on the specific requirements of the inspection, the type of material being tested, and the desired level of detail in defect detection and characterization.

When is NDT typically used?

NDT is used in various industries, including aerospace, automotive, construction, manufacturing, and oil and gas, to ensure the integrity and reliability of materials and structures.

What are the advantages of NDT?

NDT allows for the inspection of materials and structures without causing damage, reducing the need for costly repairs or replacements. It helps in ensuring the safety, reliability, and performance of components.

How does Ultrasonic Testing (UT) work?

UT uses high-frequency sound waves to detect internal flaws or defects in a material. The sound waves travel through the material, and reflections are analysed to identify irregularities.

What is Radiographic Testing (RT)?

RT involves the use of X-rays or gamma rays to inspect the internal structure of a material. It is often used to detect flaws such as cracks, voids, or inclusions.

What is Magnetic Particle Inspection (MPI)?

Magnetic Particle Inspection (MPI), also known as Magnetic Testing (MT) or Magnaflux testing, is a non-destructive testing (NDT) method used to detect surface and near-surface discontinuities in ferromagnetic materials. Ferromagnetic materials are those that can be magnetized, such as iron, nickel, and cobalt. MPI is commonly employed to inspect welds and other critical components for cracks, porosity, and other defects.

How does Magnetic Particle Testing (MPT) work?

MPT involves applying a magnetic field to a material and then applying magnetic particles to the surface. Discontinuities in the material cause the particles to accumulate, indicating the presence of a flaw.

What are Key advantages of Magnetic Particle Inspection?

Sensitivity to Surface Discontinuities:

MPI is highly sensitive to surface and near-surface defects, making it effective for detecting cracks and other discontinuities that may affect the integrity of a component.

Quick and Cost-Effective:

The inspection process is relatively quick, and the equipment is often portable, making it a cost-effective method for routine inspections.

Suitability for Field Inspections:

MPI can be performed in the field, making it suitable for inspecting structures and components in their operational environment. However, it's important to note that MPI has limitations. It is primarily effective for ferromagnetic materials and is limited to detecting discontinuities near the surface. Additionally, it may not be suitable for components with complex geometries or irregular shapes.
These advanced NDT techniques offer improved sensitivity, faster inspection times, and greater accuracy compared to conventional methods. They are often chosen based on the specific requirements of the inspection, the type of material being tested, and the desired level of detail in defect detection and characterization.

What is Liquid Penetrant Testing (LPT)?

LPT involves applying a liquid penetrant to the surface of a material. The penetrant seeps into surface-breaking defects, and excess penetrant is then removed. A developer is applied to make the defects visible

What is Eddy Current Testing (ECT)?

ECT uses electromagnetic induction to detect flaws in conductive materials. It is often used for detecting surface and near-surface defects and is particularly useful for inspecting non-ferrous materials.

How often should NDT be performed?

The frequency of NDT depends on factors such as the type of material, its intended use, and industry regulations. NDT is often performed during initial manufacturing, regular maintenance, and in-service inspections.

Is NDT applicable to all materials?

While NDT methods can be applied to a wide range of materials, the effectiveness may vary. Different methods are suitable for different materials, and the choice depends on the material's properties and the type of defects to be detected. What are the safety considerations during NDT?
Safety is paramount in NDT. Depending on the method used, precautions such as radiation protection, proper ventilation, and personal protective equipment (PPE) should be employed to ensure the safety of the personnel involved.

what is phased array ultrasonics Testing (PAUT)?

Phased Array Ultrasonic Testing (PAUT) is an advanced ultrasonic testing technique that uses multiple ultrasonic elements to produce beams of sound waves that can be electronically focused and steered. This technology offers significant advantages over traditional ultrasonic testing methods by providing more flexibility and precision in inspecting materials for flaws or defects.

What is Positive Material Identification (PMI)?

PMI stands for Positive Material Identification. It is a non-destructive testing (NDT) method used to determine the composition of materials, particularly in metal alloys. The goal of PMI is to verify that the material used in a component or structure matches the specified or required composition. This is crucial in industries where the use of specific materials with certain alloy compositions is critical for the performance and integrity of the product

What are the key aspects of Positive Material Identification (PMI)?


PMI methods involve the use of various techniques to analyze the elemental composition of a material. Common methods include X-ray fluorescence (XRF), optical emission spectrometry (OES), and laser-induced breakdown spectroscopy (LIBS).

X-ray Fluorescence (XRF):

XRF is a widely used PMI technique. It involves irradiating a sample with X-rays, which cause the atoms in the material to emit characteristic X-ray fluorescence. By measuring the energy and intensity of these emitted X-rays, the elemental composition of the material can be determined.

Optical Emission Spectrometry (OES):

OES involves applying electrical energy to the material, causing it to emit light. The emitted light is then analysed to determine the elemental composition. OES is particularly effective for analysing metals and alloys.

Laser-Induced Breakdown Spectroscopy (LIBS):

LIBS uses a laser to ablate a small amount of material from the surface of the sample. The resulting plasma emits light, and the analysis of this light provides information about the elemental composition of the material.


PMI is commonly used in industries such as petrochemical, aerospace, construction, and manufacturing, where the correct alloy composition is crucial for safety, quality, and compliance with industry standards.

Quality Control and Assurance:

PMI is an essential tool for quality control and assurance. It helps ensure that the materials used in construction, fabrication, or manufacturing meet the specified requirements and standards. On-Site and Laboratory Testing:

On-Site and Laboratory Testing:

PMI can be performed on-site using portable handheld devices or in a laboratory setting with more sophisticated equipment. On-site testing is often preferred for its convenience, especially in situations where components are large or immobile.

Verification of Welds:

PMI is frequently used to verify the composition of welds, ensuring that the welding material matches the base material and that the weld meets the required specifications. Positive Material Identification plays a crucial role in preventing material mix-ups, ensuring the integrity of components, and maintaining the quality and safety standards of various industries. It is especially important in applications where the use of specific alloys is critical for the performance and longevity of the materials.

What is Alternating Current Field Measurement (ACFM)?

ACFM stands for Alternating Current Field Measurement. It is a non-destructive testing (NDT) technique that is primarily used for the inspection of ferrous materials, such as steel, to detect and size surface-breaking cracks and other defects.

What are the key features and aspects of Alternating Current Field Measurement (ACFM)?


ACFM relies on the principle of electromagnetic induction. An alternating current is passed through a probe or sensor, generating an alternating magnetic field in the material being inspected.

Eddy Currents:

When the alternating magnetic field encounters a surface-breaking crack or defect, eddy currents are induced in the material. The presence of the crack disrupts the flow of eddy currents, creating a measurable change in the magnetic field.

Quantitative Analysis:

One of the advantages of ACFM is its ability to provide quantitative data about the size of surface cracks. This quantitative analysis makes it a valuable tool for assessing the severity of defects and determining whether they meet acceptable standards.

Surface Inspection:

ACFM is particularly useful for inspecting surfaces that may be coated or covered with paint, rust, or other materials. It can effectively detect and size defects even when they are not visible to the naked eye.


ACFM has several advantages, including the ability to inspect surfaces with coatings, the provision of quantitative data on defect size, and the capacity to detect defects in various orientations.


ACFM is commonly used in industries such as oil and gas, maritime, and aerospace for inspecting structures, pipelines, and other components where the detection and sizing of surface cracks are critical for safety and integrity.

Portable Systems:

ACFM systems are often portable, allowing for on-site inspections. This portability is valuable for inspecting components in their operational environment without the need for extensive disassembly.

Complement to Other NDT Techniques:

ACFM is often used in conjunction with other NDT techniques, such as ultrasonic testing or magnetic particle inspection, to provide a more comprehensive assessment of the material's condition.
In summary, ACFM is a valuable NDT technique for the detection and sizing of surface-breaking cracks and defects in ferrous materials. Its ability to provide quantitative data and its suitability for inspecting coated surfaces make it a versatile tool in various industries.