Non-Destructive Testing (NDT) | Overview of NDT/NDE Methods

What is Non-Destructive Testing (NDT)?

Non-Destructive Testing (NDT) is the process of inspecting, testing, or evaluating materials, components, or assemblies for discontinuities or flaws without destroying the serviceability of the part or system.

TUV Austria's Non-Destructive Testing (NDT)

Today, modern non-destructive tests are used in manufacturing, fabrication, and in-service inspections to ensure product integrity and reliability, control manufacturing processes, lower production costs, and maintain a consistent quality level.

For Example, NDT provides the quality of materials and joining processes during construction’s fabrication and erection phases. In addition, in-service NDT inspections are used to ensure that the products in use continue to have the integrity necessary to ensure their usefulness and public safety.

Overview of NDT/NDE Methods

1). Conventional NDT

2). Advanced NDT

1). Conventional NDT

Conventional methods are techniques that have matured over decades and, in this time, have become well-documented in codes, standards, and best practices.

The setup and the procedure of a conventional technique are typically more straightforward in comparison to advanced methods:

Ultrasonic testing (UT)
Magnetic Particle Testing (MT)
Liquid Penetrant Testing (PT)
Radiographic Testing (RT)
Visual Testing (VT)
Electromagnetic Testing (ET)
Infrared Testing (IR)
Vibration Analysis (VA)
In-Situ Metallography
Positive Material Identification

1.1) Radiography Testing

RT involves penetrating X or gamma radiation as sources to examine parts and products for imperfections.

Radiation is directed through a part and onto film.
When the film is developed, a shadowgraph is obtained that shows the internal soundness of a function.
Possible imperfections appear as density changes in the film, much like a medical radiograph.

1.2) Magnetic Particle Testing

MT is done by inducing a magnetic field in ferromagnetic material and dusting the surface with iron particles.

Surface and near-surface imperfections will distort the magnetic field and concentrate the iron particles near such discontinuities, thus indicating their presence.

1.3) Ultrasonic Testing

UT uses the transmission of high-frequency sound waves into a material to detect imperfections within the material or changes in material properties. The most commonly used ultrasonic testing technique is pulse-echo testing.

Wherein sound is introduced into the test object, reflections (echoes) are returned to a receiver from the part’s internal imperfections or geometrical surfaces.

1.4) Liquid Penetrant Testing

PT is probably the most widely used NDT method. First, the test object or material is coated with a visible or fluorescent dye solution. Next, the excess dye is removed from the surface, and a developer is applied. The developer acts like a blotter and draws penetrants out of imperfections that are open to the surface.

The vivid color contrast between the penetrant and the developer makes the “blued out” easy to see with visible dyes.
An ultraviolet lamp uses fluorescent dyes to make the “blued out” fluoresce brightly, thus allowing imperfections to be seen readily.

1.5) Visual Testing

VT is probably the oldest and most common method of NDT, having numerous industrial and commercial applications. Examiners follow simple and complex procedures, some of which involve comparing artistry samples with production parts. Visual techniques are used with all other NDT methods.

2). Advanced NDT

Advanced Methods tend to be less understood as they progress as emerging technologies, e.g., uncertain advantages or limitations, lack of technician qualification criteria, or little to no industry codification.

Generally, the setup, procedure, and data interpretation of advanced methods are more complicated and require specialized understanding and experience from a properly trained technician.

Eddy Current Testing (ECT)
Leak Testing (LT)
Remote Field Eddy Current Testing (RFET)
Magnetic Flux Leakage (MFL)
Internal Rotary Inspection System (IRIS)
Phased Array Ultrasonic Testing (PAUT)
Time-of-Flight-Diffraction (TOFD)
Long Range Ultrasonic Testing (LRUT)

2.1) Weld Inspection

The most commonly occurring defects in welded joints are porosity, slag inclusions, lack of side-wall fusion, lack of inter-run fusion, lack of penetration, undercutting, and longitudinal or transverse cracks.

Except for single gas pores, all the defects listed are usually well detectable by ultrasonic. Most applications are on low-alloy construction quality steel. However, welds in aluminum can also be tested.

Ultrasonic Flaw detection has long been the preferred method for non-destructive testing in welding applications. This safe, accurate, and simple technique has pushed ultrasonic to the forefront of inspection technology.

2.2) Remote Field Testing

Remote field testing, or RFT, is an electromagnetic testing method to detect discontinuities in small diameter ferromagnetic (Carbon Steel) tubes and pipes.

RFT – Remote Field Testing is a transmission test method wherein the receiver coil detects an electromagnetic field traversed through the tube wall.

2.3) Eddy Current Tube Inspection

Eddy Current Testing is a well-established non-destructive testing method used to examine nonferrous/nonmagnetic materials such as condenser and heat exchanger tubes in power generation plants. Eddy Current Testing reveals discontinuities in tubing, provides plant engineers with an accurate assessment of a unit’s condition, and is a tool for predicting the remaining useful life of the tubes.

Along with condenser and heat exchanger tube, cleaning, and leak detection applications, many power generation plants with aging units include eddying current testing in plant maintenance programs in an overall effort to maximize the efficient life of their teams.

2.4) Advanced PAUT Inspection

PAUT is an advanced inspection method to detect discontinuities components such as cracks and flaws. This method is considered very powerful and flexible in detecting defects as it can control a few parameters such as beam angle and focal length. Phased Array UT – PAUT Inspection can also be used for various applications like measuring wall thickness and corrosion testing.

Phased Array UT- PAUT is used in a wide range of applications

Weld Inspection
Corrosion Mapping
Thickness Measurements

2.5) Internal Rotary Inspection System (IRIS)

Internal Rotary Inspection System (IRIS) can detect corrosion, pitting, and wall loss and is most commonly used for tube inspection in boilers, heat exchangers, air coolers, and feedwater heaters.

It is exceptionally versatile as it is suitable for ferrous and non-ferrous materials, and IRIS can be used on a wide range of tube diameters and wall thicknesses.

2.6) Advanced TOFD Inspection

The Time-of-Flight-Diffraction (TOFD) ultrasonic testing method is sensitive and accurate for the nondestructive testing of welds for defects. Time-of-Flight-Diffraction (TOFD) method can be regarded more and more as a standard NDT technique in many countries.

Nevertheless, there is stall a considerable amount of development work going on. Nonetheless, it is among the most modern testing methods for detecting imperfections and defects in materials. the application of this method is fast and highly accurate. This has resulted in increasing popularity over the last few years.

What are Advanced NDT Methods?

Many plant operators in the oil, gas, and power generation industries face the challenges of maximizing the integrity of the plant.
Our highly skilled teams constantly endeavor to develop innovative and superior solutions for all its customers.
The efficiency and life expectancy of their assets without sacrificing safety and reliability.
Therefore, ensuring accurate inspection of vital components such as pipes and tubes is crucial.

What is the Common Application of NDT?

1). Inspection of Raw Products

Forgings
Castings
Extrusions

2). Inspection Following Secondary Processing

Machining
Welding
Grinding
Heat Treating
Plating

3). In-Service Damage Inspection

Cracking
Corrosion
Erosion/Wear
Heat Damage

What are the Advantages of NDT/NDE?

The equipment is easy to handle.
Methods are quick and accurate.
The defect can be detected without damaging the components.
The defective parts can be sorted in the preliminary production stages, saving further production costs and time.

What are the Disadvantages of NDT/NDE?

A skilled operator is required for testing.
The process should be standardized.
In some test instruments cost is too high.
In some techniques, flame, and smoke affect the result.
Components need to be claimed before and after inspection.

Why Choose Non-Destructive Testing from TUV Austria Bureau of Inspection & Certification?

TUV Austria Bureau of Inspection & Certification offers you the most effective NDT methods to investigate the integrity of your equipment and assets. Our comprehensive range of NDT methods can help you:

Save time and money through fast and practical testing of your assets and equipment at every stage of their lifespan – from manufacturing to on-site operation.
Monitor the integrity of your assets using intrusive or non-intrusive methods.
Ensure safe and reliable operation of your facilities.
Detect defects and irregularities before they result in severe damage or non-compliance.

In addition, to Non-Destructive Testing, we also offer a range of complimentary services:

FAQ’s

What are the Different Names of NDT?

NDT: Non-Destructive Testing.
NDI: Non-Destructive Inspection.
NDE: Non-Destructive Evaluation.
NDE: Non-Destructive Evaluation.

What are the Objectives of NDT?

NDT Increases Serviceability.
To Increase productivity.
It Increases the Profit.
NDT Increases Safety.

What are the methods of NDT?

Visual Inspection
Radiography
Ultrasonic
Eddy Current
Magnetic Particle
Liquid Penetrant
Tap Testing
Microwave
Acoustic Emission
Thermography
Acoustic Microscopy
Flux Leakage
Magnetic Measurements
Replication
Laser Interferometry

In Which Fields Are NDT Methods Used?

It is widely used in fields like

Mechanical Engineering.
Electrical Engineering.
Civil Engineering.
Medical.
Aerospace Engineering.
Forensics.

Where are NDT methods Used?

It is used in all stages, like in a component’s production or life cycle.
To assist in product development.
To Screen or Sort Incoming Materials.
To monitor, improve or control manufacturing processes.
To verify proper processing such as heat treating.
To verify proper assembly.
To inspect for in-service damage.

What are some uses of NDT Methods?

Flaw detection and Evaluation.
Leak Detection.
Location Determination.
Dimensional Measurements.
Structure and Microstructure Characterization.
Estimation of Mechanical and Physical Properties.
Stress and Dynamic Response Measurements.
Material Sorting and chemical composition Determination.

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