What’s the difference between NDT, NDE and NDI?
Absolutely nothing! NDT stands for Non-Destructive Testing, NDE stands for Non-Destructive Evaluation or Examination and NDI Non-destructive Inspection. There's a preference from one industry to the next over which one to use, but they all refer to the same category of test procedures that examines the integrity of materials, components or systems where no damage is caused. Read on to discover more about other NDT technologies, especially those confusing abbreviations.
Absolutely nothing! NDT stands for Non-Destructive Testing, NDE stands for Non-Destructive Evaluation or Examination and NDI Non-destructive Inspection. There's a preference from one industry to the next over which one to use, but they all refer to the same category of test procedures that examines the integrity of materials, components or systems where no damage is caused. Read on to discover more about other NDT technologies, especially those confusing abbreviations.
Automated Ultrasonic Testing (AUT)
Ultrasonic testing that uses automated systems and equipment in order to calculate results – normally equipment will have in-built software that will calculate flaw dimensions, and the results can be more reliable than manually generated tests. Phased array and ToFD are the two most popular types of automated ultrasonic testing methods available.
Alternating Current Field Measurement (ACFM)
ACFM is an electromagnetic NDT technique for detecting and sizing of surface breaking cracks in metallic components and welds. The probe introduces an electric current into the specimen and measures the associated electromagnetic fields close to the surface. The presence of a defect disturbs the associated fields and the current flows around the ends and down the faces of the crack. This technique can be performed through paint and other coatings.
Digital Radiography Testing
Digital radiography is an advanced technology based on digital detector systems in which the x-ray image is displayed directly on a computer screen without the need for developing chemicals or intermediate scanning. The incident x-ray radiation is converted into an equivalent electric charge and then to a digital image through a detector sensor
Eddy Current Testing (ET)
Conventional eddy current testing uses electromagnetic induction to detect discontinuities in conductive materials. A specially designed coil energised with alternating current is placed in proximity to the test surface generating changing magnetic-field which interacts with the test-part producing eddy current in the vicinity. Variations in the changing phases and magnitude of these eddy currents is then monitored through the use of receiver-coils, or by measuring changes to the alternate current flowing in the primary excitation-coil. The electrical conductivity variations or magnetic permeability of the test-part, or the presence of any discontinuities, will cause a change in eddy current and a corresponding change in phases and amplitude of the measured current.
Guided Wave Testing
Guided was testing is also known as long-range ultrasonic testing (LRUT). This technology uses mechanical stress waves that propagate along an elongated structure and are at the same time guided by its boundaries. Guided wave technology is used to inspect many engineering structures, but most often used for the inspection of metallic pipelines due to its ability to travel a long distance with little loss in energy.
Magnetic Particle Testing (MT)
Magnetic particle inspection (MPI) is used to detect surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen and if the material is flawless, most of the magnetic flux is concentrated below the material's surface. However, if a flaw is present, it will interact with the magnetic field and the flux will be distorted locally, escaping from the surface of the specimen where the flaw occurs. Fine magnetic particles applied to the surface of the specimen are attracted to the escaping flux, creating a visible indication of the flaw.
Dye Penetrant Testing (DPT) or Liquid Penetrant Testing (LPT)
Dye Penetrant Testing is used to locate surface-breaking defects in non-porous materials such as metals, plastics, or ceramics. To be detected, the flaw must reach the surface to be tested. The liquid penetrant is drawn into the surface-breaking crack and excess penetrant is then removed. A developer is then applied to the surface to draw out the penetrant in the crack and produce a surface indication.
Ultrasonic testing that uses automated systems and equipment in order to calculate results – normally equipment will have in-built software that will calculate flaw dimensions, and the results can be more reliable than manually generated tests. Phased array and ToFD are the two most popular types of automated ultrasonic testing methods available.
Alternating Current Field Measurement (ACFM)
ACFM is an electromagnetic NDT technique for detecting and sizing of surface breaking cracks in metallic components and welds. The probe introduces an electric current into the specimen and measures the associated electromagnetic fields close to the surface. The presence of a defect disturbs the associated fields and the current flows around the ends and down the faces of the crack. This technique can be performed through paint and other coatings.
Digital Radiography Testing
Digital radiography is an advanced technology based on digital detector systems in which the x-ray image is displayed directly on a computer screen without the need for developing chemicals or intermediate scanning. The incident x-ray radiation is converted into an equivalent electric charge and then to a digital image through a detector sensor
Eddy Current Testing (ET)
Conventional eddy current testing uses electromagnetic induction to detect discontinuities in conductive materials. A specially designed coil energised with alternating current is placed in proximity to the test surface generating changing magnetic-field which interacts with the test-part producing eddy current in the vicinity. Variations in the changing phases and magnitude of these eddy currents is then monitored through the use of receiver-coils, or by measuring changes to the alternate current flowing in the primary excitation-coil. The electrical conductivity variations or magnetic permeability of the test-part, or the presence of any discontinuities, will cause a change in eddy current and a corresponding change in phases and amplitude of the measured current.
Guided Wave Testing
Guided was testing is also known as long-range ultrasonic testing (LRUT). This technology uses mechanical stress waves that propagate along an elongated structure and are at the same time guided by its boundaries. Guided wave technology is used to inspect many engineering structures, but most often used for the inspection of metallic pipelines due to its ability to travel a long distance with little loss in energy.
Magnetic Particle Testing (MT)
Magnetic particle inspection (MPI) is used to detect surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen and if the material is flawless, most of the magnetic flux is concentrated below the material's surface. However, if a flaw is present, it will interact with the magnetic field and the flux will be distorted locally, escaping from the surface of the specimen where the flaw occurs. Fine magnetic particles applied to the surface of the specimen are attracted to the escaping flux, creating a visible indication of the flaw.
Dye Penetrant Testing (DPT) or Liquid Penetrant Testing (LPT)
Dye Penetrant Testing is used to locate surface-breaking defects in non-porous materials such as metals, plastics, or ceramics. To be detected, the flaw must reach the surface to be tested. The liquid penetrant is drawn into the surface-breaking crack and excess penetrant is then removed. A developer is then applied to the surface to draw out the penetrant in the crack and produce a surface indication.
Phased Array Ultrasonic Testing (PAUT) is an advanced ultrasonic NDT method, most often used to detect flaws in welds, and based on the principles of wave physics. 'Phased' refers to the timing, and the 'array' refers to the multiple elements. Single-element (non-phased array) probes emit a beam in a fixed direction. To test a material, a conventional probe and its beam must be moved through the problem area. However, the beam from a phased array probe can be moved electronically, without moving the probe, and can be moved through a wide volume of material at high speed. The beam is controllable because a phased array probe is made up of multiple small elements, each of which can be pulsed individually at a computer-calculated timing.
Radiographic Interpretation
Radiographic Testing is used to detect flaws by using the ability of short wavelength electromagnetic radiation to penetrate various materials. In industrial radiography there are several imaging methods available including. Film Radiography, Real Time Radiography (RTR), Computed Tomography (CT), Digital Radiography (DR), and Computed Radiography (CR).
Thermographic Inspection
Thermography is a non-contact technology where accurate temperature distributions across a surface are used to monitor machine or component condition and in some cases to predict failure. This technique uses a camera containing large numbers of infrared sensors which can detect and measure small temperature differences.
Time of Flight Diffraction (ToFD)
ToFD is an advanced method of ultrasonic inspection that uses two angled compression wave probes mounted either side of the specimen a fixed distance apart; one a transmitter, the other a receiver. In a flaw-free specimen two sound waves will be detected by the receiver – one that travels along the surface of the weld, called the lateral wave, and one reflected from the back wall. When a flaw is present the pulse emitted by the transmitter is diffracted or scattered from the tip of the flaw and this signal is picked up by the receiver. The time of flight of the signal is measured and compared with that of the lateral wave. The probes scan the specimen in a predetermined, automated pattern to enable the other end of the flaw to be detected and the flaw size established. Software is used to calculate flaw dimensions and the flaws displayed as a black and white image.
Ultrasonic Examination, Inspection or Testing (UT)
A sound wave is emitted from a transmitter which bounces off any objects in its path and is reflected back to a receiver. Knowing the speed of sound in the material enables the distance of an object to be determined by measuring the time that elapses between the transmission of the sound pulse and detection of what is known as the echo. In welded components the examination is generally performed by moving a small probe containing both a transmitter and receiver over the item and displaying the echo on an oscilloscope screen.
Visual Testing (VT)
Visual Testing is the most straight forward NDT technique, where examiners can simply look at a part to see if surface imperfections are visible, or use use computer controlled camera systems to automatically recognise and measure features of a specimen.
Radiographic Testing is used to detect flaws by using the ability of short wavelength electromagnetic radiation to penetrate various materials. In industrial radiography there are several imaging methods available including. Film Radiography, Real Time Radiography (RTR), Computed Tomography (CT), Digital Radiography (DR), and Computed Radiography (CR).
Thermographic Inspection
Thermography is a non-contact technology where accurate temperature distributions across a surface are used to monitor machine or component condition and in some cases to predict failure. This technique uses a camera containing large numbers of infrared sensors which can detect and measure small temperature differences.
Time of Flight Diffraction (ToFD)
ToFD is an advanced method of ultrasonic inspection that uses two angled compression wave probes mounted either side of the specimen a fixed distance apart; one a transmitter, the other a receiver. In a flaw-free specimen two sound waves will be detected by the receiver – one that travels along the surface of the weld, called the lateral wave, and one reflected from the back wall. When a flaw is present the pulse emitted by the transmitter is diffracted or scattered from the tip of the flaw and this signal is picked up by the receiver. The time of flight of the signal is measured and compared with that of the lateral wave. The probes scan the specimen in a predetermined, automated pattern to enable the other end of the flaw to be detected and the flaw size established. Software is used to calculate flaw dimensions and the flaws displayed as a black and white image.
Ultrasonic Examination, Inspection or Testing (UT)
A sound wave is emitted from a transmitter which bounces off any objects in its path and is reflected back to a receiver. Knowing the speed of sound in the material enables the distance of an object to be determined by measuring the time that elapses between the transmission of the sound pulse and detection of what is known as the echo. In welded components the examination is generally performed by moving a small probe containing both a transmitter and receiver over the item and displaying the echo on an oscilloscope screen.
Visual Testing (VT)
Visual Testing is the most straight forward NDT technique, where examiners can simply look at a part to see if surface imperfections are visible, or use use computer controlled camera systems to automatically recognise and measure features of a specimen.
