NDE Inspection

What is NDE Inspection?

NDE Inspection stands for Non-Destructive Examination. It is a process used to detect any defects or irregularities in materials and components without damaging the inspected item.

The process uses physical, non-destructive techniques such as DPT, Visual, ultrasound, radiography, magnetic particle testing and eddy current testing to evaluate the integrity of a material or component. NDE Inspection can be used on a variety of materials including metals, rubber and plastics.

The main purpose of NDE Inspection is to identify any flaws that could cause serious safety issues or performance failures if left undetected.

It helps organizations maintain quality assurance standards by ensuring products meet certain specifications throughout their manufacturing processes and supply chains.

Additionally, NDE inspection can help extend product lifetime by verifying structural integrity before fatigue failure sets in due to tiny cracks or deformations that may be present in the material but not visible to the naked eye.

Non-destructive Examination (NDE) Methods

Non-destructive testing welding inspection utilizes basic inspection such as Visual Inspection as well as advanced techniques such as radiography imaging, ultrasound, magnetic particle, and eddy current testing, etc. to detect flaws without damaging material components.

Nondestructive Testing Welding Inspection methods use non-invasive techniques such as visual examination, ultrasonic testing, and radiographic imaging to assess weld quality without damaging the component.

Read more: Types of Welding Defects.

Nondestructive testing is faster, less expensive and more accurate than DT methods because it can detect very small flaws that may not be visible with the naked eye.

The following are the main NDE Methods used for Inspection:

  1. Visual Inspection
  2. Dye Penetrant Inspection
  3. Magnetic Particle Testing
  4. Ultrasonic Inspection
  5. Radiographic Inspection
  6. Eddy Current Inspection
  7. Magnetic Flux Leakage (MFL) Inspection
  8. Leak Testing
  9. Thermal/Infrared Inspection
1. Visual Inspection

The purpose of visual inspections is to detect potential problems with the joint prior to its use or installation.

visual testing

This can help identify any misalignment, porosity, cracks, undercuts or other problems before they become significant issues that may cause costly repairs or replacements later on down the line.

Visual inspections should be performed by trained professionals who can accurately assess welds and determine if any corrective action needs to be taken.

The inspector should record all observations and measurements so that this information can be used in future assessments as well as serving as documentation supporting product quality control standards.

2. Dye Penetrant Inspection

Dye Penetrant Inspection is a highly effective non-destructive testing (NDT) method used to identify surface defects in materials.

dye-penetrant-inspection indication

This procedure is commonly employed to detect open to surface flaws such as cracks, porosity, laps, lack of fusion and other similar issues. It can be used on a wide variety of materials including metals, ceramics, plastics and composites.

The DP process involves first cleaning the surface of the material under inspection to remove any dirt or oil that may interfere with the inspection.

Second, a penetrant liquid is applied which will seep into any existing cracks or flaws and cause them to be visible.

Finally, after allowing enough time for the penetrant to penetrate completely into the material’s surface defects, an activator liquid known as Developer is applied which will enhance visibility and make the defects apparent.

3. Magnetic Particle Testing

Magnetic Particle Testing (MPT) is a form of non-destructive testing used to detect surface and sub-surface discontinuities in ferromagnetic materials. This type of material includes iron, cobalt, nickel, and some alloys such as steel and stainless steel.

MPT works by inducing a magnetic field into the test object which then causes small particles composed of either ferrite or iron oxide to become magnetised and gather around any defects present along the material’s surface.

MT proecedure

The application of MPT can be used for detecting cracks, laps, seams, lack of fusion, porosity leaks in pressure vessels or welds. It is also effective for finding grinding cracks on components such as crankshafts and gears.

The technique provides accurate results with little required preparation time prior to testing making it cost effective when compared with other non-destructive methods.

4. Ultrasonic Inspection

Ultrasonic Inspection, or UT, is a non-destructive testing method used to detect internal flaws in materials. It utilizes sound waves of ultrasonic frequency that are sent into the material being inspected and the reflected signal is analyzed for flaws.

This type of inspection can be used on various materials such as metals, plastics and composites which makes it a very useful tool for many industries.

UT_principle explained

UT inspection uses probes known as transducers which send out sound waves that reflect off any flaws inside the material being inspected. This data is then interpreted by trained UT technicians using sophisticated computer systems to accurately assess the condition of the material being tested.

By analyzing these readings, it’s possible to accurately identify the size and location of any defects present within the object being tested.

5. Radiographic Inspection

Radiographic Inspection, also known as RT or Radiographic testing, is a process used to view the interior structure of an object.

This form of non-destructive testing allows engineers and technicians to examine materials for any hidden defects that may otherwise go unnoticed.

It uses X-rays or gamma rays to penetrate the material and produce an image of its internal structure. This image can then be evaluated for any imperfections that may not be visible with the naked eye.

RT Principle Inspection of Welding

Radiography uses X-rays or gamma radiation to take images from different angles and depths within the material being examined.

X-ray film is then used to develop images which are analyzed by trained personnel for any irregularities or inconsistencies. Radiography not only allows for a detailed look into an object’s internal structure but also determines how well it was constructed.

6. Eddy Current Inspection

Eddy current inspection, also known as Eddy Current Testing (ECT), is an important non-destructive testing technique used to detect surface and sub-surface flaws in a material or component.

This method uses electromagnetic induction to identify the presence of surface and near-surface flaws, such as cracks, pits, laps and seams. The eddy current method is commonly used for inspecting heat exchanger tubes, aircraft components and welds.

Eddy Current Non Destructive Testing

The process involves inducing a high frequency alternating magnetic field on the sample using a coil transmitter. An eddy current probe is then introduced into the sample which will detect any discontinuities or irregularities in its surface.

Flaws are identified by changes in impedance of the eddy currents that travel through the material during its inspection; these changes can be detected by analyzing variations in signal magnitude and phase angle when compared against baseline readings from acceptable samples.

ECT has become increasingly popular due its ability to provide quick results without causing any damage to the tested material. This method is particularly useful for detecting cracks and other surface issues such as corrosion that may not be visible to the naked eye.

7. Magnetic Flux Leakage (MFL) Inspection

Magnetic Flux Leakage (MFL) Inspection is an advanced non-destructive testing method to ensure the integrity of pipelines, tanks and other structures.

It uses magnetic fields to detect leaks and anomalies that may occur in these structures. The core technique behind MFL Inspection is based on the magnetic flux leakage principle: when a permanent magnet is set close to a steel surface, it produces an alternating magnetic field which induces eddy currents in any imperfections present in the steel.

MFL testing Magnetic flux leakge inspection 1 Inspection of Welding
Reference: Codesteel

These eddy currents then create their own field, which can be detected from outside the structure with special sensors called probes.

The advantage of MFL inspection over other methods such as visual or ultrasonic inspection is that it provides rapid coverage over large areas without having to disassemble components or break through walls. This makes it well suited for safety critical applications where timely detection of faults are essential.

8. Leak NDE Inspection

Leak testing is an essential method for ensuring the integrity of components and systems. It is used in a variety of industries, from automotive to aerospace, as a non-destructive testing (NDT) technique to detect cracks and other defects that could lead to failure or malfunction.

Leak tests involve applying pressurized air or liquid into the system while measuring the escape rate at different points. If any pressure change is detected, it can be concluded that there are leaks present in the system that must be repaired before the product can be safely put into service.

The leak test inspection process involves carefully monitoring each point of connection and inspecting all parts for visible signs of leaks such as wet spots or bubbles. This allows technicians to identify any potential issues before they become serious problems.

9. Thermal/Infrared NDE Examination

Thermal infrared testing is a Non-Destructive Testing (NDT) method used to detect problems in materials, components and systems before they become hazardous.

This powerful inspection method offers an effective means of locating faults in electrical and mechanical components without causing any structural damage or disruption. It can detect variations in temperature on the surface of objects and reveals changes that may indicate impending failure.

Thermal Imaging Cameras Inspection of Welding

In thermal infrared testing, heat energy waves are emitted from the part being inspected and captured by a thermal imaging camera.

The temperatures are measured at various points across the surface providing an overview of how much energy is emitted from each area. Defects can be quickly identified due to the contrast between areas with abnormal temperatures and those with normal readings. This technique enables engineers to make informed decisions about which parts require immediate action for repair or replacement before safety risks arise.

Jiten Karmakar is an NDT Specialist, holding ASNT NDT Level III and ISO 9712 NDT Level III Qualifications. He is having vast hands-on practical and theoretical experience with all major NDT Methods and technique.