Nondestructive Electric Test

[Niobe Hennigan]

NDTstands for Non-Destructive Testing. It refers to an array of inspection methods that allow inspectors to evaluate and collect data about a material, system, or component without permanently altering it.

For instance, when inspectors in industrial settings review the outside of a pressure vessel with their naked eye, that would fall under the NDT designation, since they are collecting data on the status of the boiler without damaging it. On the other hand, using a sophisticated tool like an ultrasonic sensor to look for defects in a certain material or asset would also be called NDT.

Savings. The most obvious answer to this question is that NDT is more appealing than destructive testing because it allows the material or object being examined to survive the examination unharmed, thus saving money and resources.

Accuracy. NDT methods have been proven accurate and predictable, both qualities you want when it comes to maintenance procedures meant to ensure the safety of personnel and the longevity of equipment.

"NDT is the life blood of a well-run facility, and the high importance of NDT is known by any trained inspector. NDT techniques and repeatable results depend on highly trained technicians with experience and integrity. Not only does the technician need to be certified in a specific NDT method, but they also need to know how to operate the equipment being used to gather data. Understanding equipment capabilities and limitations is the difference between making an accept or reject determination."

Rope access. The use of rope access also requires inspectors to work at height in order to collect inspection data. Learn more about rope access and how it's used by inspectors in this guide.

Drones. Inspectors can use drones to collect inspection data remotely, allowing them to remain safely outside of confined spaces or safely below locations at height. Read the next section to learn more about how drones can be used for NDT.

NDT techniques can be used for all kinds of inspections. But some of the most important types of NDT inspections are of assets like boilers and pressure vessels, which could be incredibly dangerous if not properly maintained.

Because proper maintenance of these assets is so important for the safety of those working nearby (or even at a distance, when it comes to nuclear power plants), most countries have laws requiring companies to adhere to specific inspection codes and standards when conducting inspections.

These standards and codes typically require inspections to be conducted periodically following specific guidelines. For the most assets that present the greatest risk, these inspections must be both conducted by a certified inspector and approved by a certified witness working for a formal inspection body.

3 point bend testing. 3 point bend testing examines the soundness and flexibility (or ductility) of a material by taking a sample of it, called a coupon, and bending it in three points to a specified angle.

Definition: Visual Non-Destructive Testing is the act of collecting visual data on the status of a material. Visual Testing is the most basic way to examine a material or object without altering it in any way.

Visual Testing can be done with the naked eye, by inspectors visually reviewing a material or asset. For indoor Visual Testing, inspectors use flashlights to add depth to the object being examined. Visual Testing can also be done with an RVI (Remote Visual Inspection) tool, like an inspection camera. To get the camera in place, NDT inspectors may use a robot or drone, or may simply hang it from a rope.

One of the most common Ultrasonic Testing methods is the pulse echo. With this technique, inspectors introduce sounds into a material and measure the echos (or sound reflections) produced by imperfections on the surface of the material as they are returned to a receiver.

Radiography Testing directs radiation from a radioactive isotope or an X-ray generator through the material being tested and onto a film or some other kind of detector. The readings from the detector create a shadowgraph, which reveals the underlying aspects of the inspected material.

Definition: Eddy Current Non-Destructive Testing is a type of electromagnetic testing that uses measurements of the strength of electrical currents (also called eddy currents) in a magnetic field surrounding a material in order to make determinations about the material, which may include the locations of defects.

To conduct Eddy Current Testing, inspectors examine the flow of eddy currents in the magnetic field surrounding a conductive material to identify interruptions caused by defects or imperfections in the material.

Definition: Magnetic Particle Non-Destructive Testing is the act of identifying imperfections in a material by examining disruptions in the flow of the magnetic field within the material.

To use Magnetic Particle Inspection, inspectors first induce a magnetic field in a material that is highly susceptible to magnetization. After inducing the magnetic field, the surface of the material is then covered with iron particles, which reveal disruptions in the flow of the magnetic field. These disruptions create visual indicators for the locations of imperfections within the material.

Inspectors conducting Acoustic Emission Tests are examining materials for bursts of acoustic energy, also called acoustic emissions, which are caused by defects in the material. Intensity, location, and arrival time can be examined to reveal information about possible defects within the material.

Definition: Dye Penetrant Penetrant Non-Destructive Testing (also called Liquid Penetrant Testing) refers to the process of using a liquid to coat a material and then looking for breaks in the liquid to identify imperfections in the material.

After this, inspectors use a developer to draw the solution out of the defects, then use ultraviolet light to reveal imperfections (for fluorescent dyes). For regular dyes, the color shows in the contrast between the penetrant and the developer.

Welds are one of the most common parts of industrial assets that inspectors test. Using non-destructive weld testing equipment, inspectors can determine whether a weld is strong or has potential defects that could compromise its integrity.

A visual inspection can be used for weld NDT, to help inspectors make basic determinations about the strength of a weld, though its findings may be more limited than the above welding testing methods.

Macro etch weld testing. Removing a small sample from the weld, polishing the samples, then etching on the samples with an acid mixture in order to test the internal makeup of the weld.

Due to limitations in the technology, for some time drones could only provide supplementary visual data for inspectors, but could not take the place of inspectors physically collecting visual data themselves.

However, as drone technology has improved, inspectors have been able to use drones more and more as RVI tools, in some instances completely replacing the need for them to collect visual data manually.

For indoor inspections of assets like pressure vessels or boilers, using a drone like the Elios 3 to collect visual data means the inspector does not have to enter a confined space to do so, again helping significantly reduce the exposure to risk.

Using a professional indoor drone instead of sending an inspector in to collect visual data manually means that companies save on not having to build and take down scaffolding, and can reduce downtimes associated with those requirements, in some cases by as much as one to two days.

Because a drone inspection can be mounted quickly, inspections can be conducted more frequently, helping to identify issues earlier and increasing the longevity of the asset. These early discoveries can save companies hundreds of thousands of dollars with a single inspection.

Manually reviewing the mountains of data provided by inspection drones would overwhelm a human. As a result, software designed to help inspectors make sense of the information gathered has become a necessity rather than a luxury.

Aided by machine learning and AI, these advanced programs can process and review images of the asset and flag issues for human review. WinCan, for example, is a company that makes software just for sewer inspections. Using an AI-powered algorithm, its software can take raw visual data from a sewer inspection and identify all of the potential defects that might require further inspection or repair.

Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage.[1]The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology.[2]Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing.[3] NDT is commonly used in forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art.[1] Innovations in the field of nondestructive testing have had a profound impact on medical imaging, including on echocardiography, medical ultrasonography, and digital radiography.

Non-Destructive Testing (NDT/ NDT testing) Techniques or Methodologies allow the investigator to carry out examinations without invading the integrity of the engineering specimen under observation while providing an elaborate view of the surface and structural discontinuities and obstructions. The personnel carrying out these methodologies require specialized NDT Training as they involve handling delicate equipment and subjective interpretation of the NDT inspection/NDT testing results.

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