Non Destructive Testing Methods| Sigma Test

Non destructive testing


Non Destructive Testing

Non Destructive Testing also referred to as NDT is an array of inspection approaches that permit inspectors to access and accumulate data about a system, material, or any component without eternally altering it.  

  • NDT is also known as:
  • NDE (Non-Destructive Examination or Evaluation)
  • NDI (Non-Destructive Inspection)

For Commercial Applications

The primary focus of this article, and our work at XYZ- is the goal of NDT is to make sure that critical infrastructure is appropriately maintained in order to avoid shattering accidents.

Non Destructive Testing methods are typically associated with industrial use cases, like reviewing weak points in a boiler used at an oil refinery, uses in medicine are essentially some of the most common. For example, an expecting mother going through an ultrasound check on the health of the baby would be considered an NDT use case, same goes with an X-ray or MRI to acknowledge more about an injury.

However, it is significant to note that NDT does not significantly need the use of special tools, or any tools at all.  

For example, when inspectors in industrial settings review the outside of a pressure vessel with their naked eye, that would fall under the non-destructive testing designation, subsequently, they are accumulating data on the position of the boiler without damaging it. On the other hand, using an advanced tool like an ultrasonic sensor to look for flaws in a certain material or asset would also be called NDT.      

Regardless of the particular use case, the fundamental unity among all these instances is the gathering of data in a non-intrusive manner.

Non-Destructive Testing CODES AND STANDARDS:

NDT techniques can be used for all sorts of inspections. But some of the most significant sorts of Non- Destructive Testing examinations are of assets like pressure vessels, and boilers, that could be incredibly dangerous if not properly upheld.  

Because appropriate maintenance of these assets is so significant for the safety of those working adjacent (or even at a distance, when it comes to nuclear power plants), most countries have laws requiring organizations to adhere examination codes and standards when conducting examinations.  

These values and codes typically need inspections to be led periodically following particular guidelines. For the most assets that present the greatest risk, these inspections must be both conducted by an expert examiner and approved by a certified witness employed for a formal check-up body.   

Below-mentioned is the most commonly followed organizations in the world for generating NDT standards and codes:

  • API (American Petroleum Institute)
  • ASME (American Society for Mechanical Engineers)
  • ASTM (American Society for Testing and Materials)
  • ASNT (American Society for Nondestructive Testing)
  • COFREND (French Committee for Nondestructive Testing Studies)
  • CSA Group (Canadian Standards Association)
  • CGSB (Canadian General Standards Board)

Why Use Non-Destructive Testing?

Here are the top reasons non-destructive testing is used by numerous companies throughout the world:


The most certain answer to this question is that non-destructive testing is more tempting than destructive testing because it permits the material or object being inspected to survive the examination unharmed, hence saving money and resources.   


NDT is also appealing because almost Non-Destructive Techniques (except radiographic testing) are bland to people.


NDT procedure permits for a thorough and relatively instantaneous evaluation of assets, which can be essential for ensuring continued safety and performance on a job site


NDT methods have been proven precise and expectable, both qualities you want when it comes to conservation procedures meant to make sure the safety of personnel and the durability of the equipment.  

NDT is the essential of a well-run facility. NDT techniques and repeatable results depend on highly trained technicians with experience and integrity. Industrial non-destructive methods and clarification of results are performed by the proficient professionals. Not only is the technician required to be certified in a particular NDT method, but they also require to know how to operate the equipment being used to gather data. Understanding equipment capabilities and limitations are the alterations amidst making an accept or reject determination.  

Eight Most Common NDT Methods

There are several techniques used in non-destructive testing for the collection of several types of data, each requiring its own sort of tools, preparation, and training.

Some of these techniques might permit for a comprehensive volumetric examination of an object, while others only allow a surface examination. In the same way, some non-destructive testing procedure will have varying degrees of success depending on the sort of material they are used on, and some techniques -such as Magnetic Particle NDT, for example- will only work on specific materials (i.e., those that can be magnetized).  

In a similar way, some NDT methods will have varying degrees of success depending on the type of material they’re used on, and some techniques—such as Magnetic Particle NDT, for example—will only work on specific materials (i.e., those that can be magnetized).

Here are the eight most commonly used NDT techniques:


Visual Non-Destructive Testing is the performance of gathering graphic data on the grade of a factual. Visual Testing is a vital way to examine a physical or object without changing it in any way.

Visual Testing can be done with the naked eye, by an examiner graphically reviewing material or asset. For indoor Visual Testing, expert inspectors use flashlights to add depth to the object being inspected. Visual Testing can also be done with a Remote Visual Inspection tool, like a camera. To get a camera in place, non-destructive inspectors may use a drone or robot, or may simply hang it from a rope.  


Ultrasonic Non- Destructive Testing is the process of transmitting high- frequency sound waves into a physical in order to identify changes in the component’s or material’s possessions.

Generally, Ultrasonic Testing uses sound waves to detect flaws or deficiencies on the surface of the material created.   

One of the most shared Ultrasonic Testing methods in the pulse-echo. With this technique, examiners introduce sounds into the material and measure the echoes (or sound reflections) produced by limitations on the surface of the material as they are returned to a receiver.

Here are some other types of Ultrasonic Testing:

  • Phased Array Ultrasonic Testing (PAUT)
  • Automated Ultrasonic Testing (AUT)
  • Time-Of-Flight Diffraction (TOFD)


Radiography NDT is the procedure of using gamma- or X-radiation on materials to recognise flaws.

RT directs radiation from a radioactive isotope or an X-ray generator through the component being tested and onto a film or some other kind of sensor. The readings from the detector create a shadowgraph, which discloses the fundamental features of the examined material.

RT can discover features of a physical that can be hard to sense with the naked eye, such as changes to its density.


Eddy Current Non-Destructive Testing is a sort of electromagnetic testing that uses measurements of the power of electrical currents (also called eddy currents) in a magnetic field near a physical in order to make purposes about the material, which may include the locations of flaws.

To bear Eddy Current Testing, examiners inspect the movement of eddy currents in the magnetic field adjacent to a conductive material to recognise pauses caused by flaws or failures in the component.


Magnetic Particle NDT is the procedure of classifying deficiencies in a component or material by inspecting disturbances in the movement of the magnetic field surrounded by the material.

In order to use MT, examiners first persuade a magnetic field in a material that is highly susceptible to magnetization. After prompting the attractive field, the surface of the material is then enclosed with iron particles, which reveal commotions in the movement of the magnetic field. These disturbances create visual needles for the locations of flaws within the component or material.


Acoustic Emission NDT is the procedure of using acoustic releases to classify possible defects and failures in a material.

Examiners conducting AE are probing materials for eruptions of audio energy, also called acoustic emissions, which are produced by flaws in the material. Intensity, location, and arrival time can be inspected to disclose data about possible flaws within the component or material.


Liquid Penetrant NDT refers to the course of using a liquid to cover a substance and then looking for disruptions in the liquid to classify deficiencies in the component or material.


Leak NDT mentions the procedure of learning escapes in a vessel or construction in order to recognise imperfections in it.

Examiners can identify leakages within a vessel using dimensions taken with a pressure gauge, soap-bubble tests, or electronic listening devices, among others.

Where Is Non-Destructive Testing Used?

Depending on how broadly you define non-destructive testing you could say that it’s used in almost every manufacturing unit in the world, subsequently, visual inspections (whether formalized or casual) take place in almost every workshop in some form or other.

That being said, there are particular organisations that require non-destructive testing and have dignified processes for its use, as organised by those companies we listed above like API and ASME.

The primary industries include:

  • Oil & Gas
  • Power Generation
  • Chemicals
  • Mining
  • Aerospace
  • Automotive
  • Maritime
  • Mining 

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Some of the Non-Destructive Testing Methods are as follows:

Rebound Hammer Test

Conducting a rebound hammer test as per IS 13311(Part-2), ASTM C 805. The rebound hammer test shall be conducted at all those points were the UPV test has been performed. One point consisting of six readings spread over an area of 1 sq. shall be considered as 1 test.

Ultra-Sonic Pulse Velocity Test

Conducting Ultra-Sonic Pulse velocity (UPV) test at selected locations on the RCC members of the Structures covered under the study by making 300 mm x300mm c/c grids to know about the homogeneity and quality of concrete. The test is performed as per the IS 13311 (Part-1) / ASTM C 597.

Core Extraction and Testing

Extracting the concrete core samples of minimum 65 mm diameter and 100-150 mm length (approx.) from a selected location forms RCC members of the structures covered under the study and evaluation of the properties in the laboratory from the core sample selected. IS 456:2000; IS 516:1959; IS 1199:2002; ASTM C-42.

Cut AND Pull Out (CAPO) Test

As per ASTM C-900

Half – Cell / Surface Potential Test

Measuring the half-cell /surface potential at the selected location on RCC members of the structures covered under the study will help in understanding the extent of reinforcement corrosion as per ASTM C 876.

Ferro Scanning Test

At a selected location on the RCC members of the structures covered under the study see the adequacy of concrete cover to rebars and effect of carbonation.

Carbonation Test

Measurement of carbonation depth by phenolphthalein spray test at the selected location on RCC members of the structures covered under the study is used to see the depth of carbonation.

Moisture Test by Moisture Meter

Moisture profile of concrete with respect to depth.

Chemical Analysis

Chemical analysis of chlorides, Sulfates, pH, alkali-silica, etc on concrete powder collected from the structures, covered under the study, by drilling to understand the chemical deterioration/degradation of concrete and its effect on reinforcement corrosion.

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What are the types of non-destructive testing?

Here are the eight most-used NDT techniques:

Visual Testing (VT) …

Ultrasonic Testing (UT) …

Radiography Testing (RT) …

Eddy Current (Electromagnetic) Testing (ET) …

Magnetic Particle Testing (MT) …

Acoustic Emission Testing (AE) …

Liquid Penetrant Testing (PT) …

Leak Testing (LT)

What is a non-destructive testing technician?

NDT Technicians, also known as non-destructive testing technicians, perform tests and provide information about the condition of components and materials without destroying them.

What is the difference between destructive and non-destructive testing?

Destructive testing destroys or alters the part so that even if it passes the test, it is no longer fit for service, whereas Non-destructive testing doesn’t eliminate or adjusts the part is still fit for use if it clears all the test.

What is the most frequently used non-destructive test?

Ultrasonic Testing (UT),

Radiographic Testing (RT),

Electromagnetic Testing (ET),

Magnetic Particle Testing (MT),

Liquid Penetrant Testing (PT),

Visual Testing (VT), are the six most frequently used non-destructive test.

How do you get into non-destructive testing?

Potential inspectors require a high school diploma or GED certification at the lever where the job will place them, and a background in engineering or related procedures will get into non-destructive testing.

Is NDT dangerous?

Though NDT testing does not possess hazardous to testing personnel, however, it does involve potentially harmful exposures to ultraviolet radiation, ionizing radiation, or X-rays.

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