Nondestructive Testing (NDT) Equipment Information

Non-Destructive Testing (NDT) Equipment Information

Non-destructive testing (NDT) equipment is used to detect, inspect, and measure flaws, bond integrity, and other material conditions without permanently altering or destroying the examined part or product. NDT equipment includes a wide variety of instruments and systems. Examples include thickness gauges, flaw detectors, material condition testers, and eddy current instruments, as well as devices that measure conductivity, resistivity and corrosion. Some non-destructive testing (NDT) equipment can be mounted on a rack, in a cabinet, or on a printed circuit board (PCB). Other devices are designed to be held by hand or operated from a benchtop. Common technologies for non-destructive testing (NDT) equipment include radiography or X-ray analysis, laser holography or gaging, penetrant testing, and magnetic particle testing.

Acoustic Emission Instruments and Noise Detectors

Acoustic emission instruments and noise detectors are non-destructive testing (NDT) equipment for monitoring conditions and detecting changes in mechanical, electrical and process systems. Acoustic emission instruments are used to detect shorting or arcing in electrical power distribution systems. In mechanical systems, flaws also provide specific acoustic or vibrational responses. For example, if a break, deformation or other failure occurs, acoustic emission sensors can detect the burst of high frequency caused by the event. Noise detectors are used to detect leaks or changes in process components such as steam traps, pipes, valves, and pressure vessels. Ultrasonic (UT) noise detectors can identify changes in bearings, gearboxes, and rotating machinery due to changes in wear or load.  Other ultrasonic inspection methods such as the pulse-echo technique detect flaws and estimate sizes by comparing the amplitude of a reflected echo from an interface with that of a reference interface of known size.

Eddy Current Instruments

Eddy current instruments are nondestructive testing (NDT) equipment used to induce detectable eddy currents in conductive materials. They detect flaws, determine thickness, inspect welds, measure conductivity, and sort alloys. Eddy current instruments include a straight or angled magnetic probe and an analog or digital meter with a zero reference point. Moving the magnetic probe over the surface of a conductive material such as a metal tube induces circulating currents (eddies) of electrons that oppose the externally applied magnetic field from the probe. Surface irregularities such as cracks and corrosion interrupt the surface flow of eddy currents and are detected.


Infrared (IR) and radiographic nondestructive testing (NDT) equipment is used to determine the thickness or basis weight of webs, sheet materials, or coatings. With nonmetallic materials such as plastic films or webs, radiation is reflected back or transmitted in order to determine absorption levels. Increases in mass, density, or thickness result in increased absorption. Gauges are often calibrated with samples of a known thickness, density, or mass. Equipment that uses penetrating X-rays or gamma rays is commonly available. Densitometers are used to quantity the density variants in X-ray images. Penetrameters or other X-ray opaque gage references are positioned with the part during imaging for sizing internal cracks, pores, defects and other features.


Penetrant testing systems are non-destructive testing (NDT) equipment that detects discontinuities in the surface of components. Parts are sprayed with aerosols, immersed in liquids, or dusted with powders. Capillary action pulls the penetrant into surface flaws. Next, a cleaner is used to remove the residual surface penetrant from the part that the only penetrant that remains is in the flaws or cracks. Many non-destructive testing (NDT) penetrant systems are available. Red dye penetrants are visible under normal light. Fluorescent penetrants may require ultraviolet (UV) light or backlight illumination.