Nondestructive Testing Methods

Magnetic Particle

Liquid Penetrant

Eddy Current

Radiography

Ultrasonic

Acoustic Emission

Magnetic Particle Testing

Magnetic Particle Testing

Magnetic Particle TestingMagnetic Particle Testing

Magnetic Particle Testing

Magnetic particle inspection is a method that can be used to find surface and near surface flaws in ferromagnetic materials such as steel and iron.

Magnetic Particle Testing

The technique uses the principle that magnetic lines of force (flux) will be distorted by the presence of a flaw in a manner that will reveal it's presence.

S N S NN S

IRON POWDER

CRACK

Magnetic Particle Testing

N S

IRON POWDER

CRACK

COIL (COMPLETELY

CLOSED MAGNET)

Magnetic Particle TestingThe flaw (for example, a crack) is located from the "flux leakage", following the application of fine iron particles, to the area under examination. There are variations in the way the magnetic field is applied.

N S

IRON POWDER

S NN S

IRON POWDER

CRACK

CRACK

Magnetic Particle Testing

The iron particles can be applied dry or wet; suspended in a liquid, colored or fluorescent. While magnetic particle inspection is primarily used to find surface breaking flaws, it can also be used to locate sub-surface flaws. But it's effectiveness quickly diminishes depending on the flaw depth and type.

Magnetic Particle Testing

Surface irregularities and scratches can give misleading indications. Therefore it is necessary to ensure careful preparation of the surface before magnetic particle testing is undertaken.

Liquid Penetrant Testing

Liquid Penetrant Testing

Liquid penetrant inspection is a method that is used to reveal surface breaking flaws by bleedout of a colored or fluorescent dye from the flaw.

Liquid Penetrant TestingLiquid Penetrant Testing

The technique is based on the ability of a liquid to be drawn into a "clean" surface breaking flaw by capillary action.

Liquid Penetrant TestingLiquid Penetrant Testing

Fluorescent penetrant on surface seeps into the crack.

PenetrantPenetrationPenetration

Emulsifies is applied to the penetrant. Emulsifier mixes with penetrant on the surface, but penetrant in the crack is not emulsified. Emulsifier makes the mixture washable .

Liquid Penetrant TestingLiquid Penetrant Testing

Penetrant only

Emulsifier and penetrant

EmulsificationEmulsification

Water spray removes the emulsified penetrant. Water removes the surface film as well.

Liquid Penetrant TestingLiquid Penetrant Testing

Penetrant only

waterRinseRinse

Developer draws the penetrant out of the crack.

Liquid Penetrant TestingLiquid Penetrant Testing

Penetrant

DevelopmentDevelopment

developer

Black light causes the penetrant to glow in dark.

Liquid Penetrant TestingLiquid Penetrant Testing

Penetrant

InspectionInspection

Developer

Black Light

Ultrasonic Testing

Ultrasonic Testing

Ultrasonic inspection uses sound waves of short wavelength and high frequency to detect flaws or measure material thickness. It is used on aircraft, the power stations generating plant, or welds in pressure vessels at an oil refinery or paper mill.

Ultrasonic Testing

Usually pulsed beams of high frequency ultrasound are used via a hand-held transducer which is placed on the specimen.

Ultrasonic Testing

Any sound from that pulse that returns to the transducer like an echo is shown on a screen which gives the amplitude of the pulse and the time taken to return to the transducer.

Ultrasonic Testing

Defects anywhere through the specimen thickness reflect the sound, back to the transducer. Flaw size, distance and reflectivity can be interpreted. Because of its complexity considerable technician training and skill is required.

Eddie Current Testing

Eddie Current Testing

Eddie Current TestingEddie Current Testing

Eddy current testing is an electromagnetic technique and can only be used on conductive materials. It's applications range from crack detection, to the rapid sorting of small components for either flaws, size variations, or material variation. Commonly it is used in the aerospace, automotive, marine and manufacturinq industries.

Eddie Current TestingEddie Current Testing

When an energized coil is brought near to the surface of a metal component, eddy currents are induced into the specimen. These currents set-up magnetic field that tend to oppose the original magnetic field. The impedance of coil in close proximity to the specimen is effected by the presence of the induced eddy currents in the specimen.

Eddie Current TestingEddie Current Testing

When the eddy currents in the specimen are distorted by the presence of the flaws or material variations, the impedance in the coil is altered. This change is measured and displayed in a manner that indicates the type of flaw or material condition.

Acoustic Emission Testing

Acoustic Emission Testing

Acoustic Emission TestingAcoustic Emission Testing

Acoustic emission monitoring (AE) involves listening to the sounds (which are usually inaudible to the human ear) made by a material, structure or machine in use or under load and drawing conclusions about it's "state of health" from what is heard, just as a Doctor would listen to your heart and lungs.

Acoustic Emission TestingAcoustic Emission Testing

The technique involves attaching one or more ultrasonic microphones to the object and analyzing the sounds using computer based instruments.

The noises may arise from friction (including bearing wear), crack growth, turbulence (including leakage) and material changes such as corrosion.

Acoustic Emission TestingAcoustic Emission Testing

The advantages of AE are that a whole structure can be monitored from a few locations, the structure can be tested in use (without taking it out of service) and continuous monitoring with alarms is possible. Microscopic changes can be detected if sufficient energy is released and source location is also possible using multiple sensors.

Acoustic Emission TestingAcoustic Emission Testing

Applications include testing pipelines and storage tanks (above and below the ground), fibreglass structures, rotating machinery, weld monitoring and biological and chemical changes.

Radiography(X-Ray

Inspection)

Radiography(X-Ray

Inspection)

Radiography(X-Ray Inspection)Radiography(X-Ray Inspection)

X-rays are produced by high voltage x ray machines whereas gamma rays are produced from radioactive isotopes such as Iridium 192 .The x-ray or gamma rays are placed close to the material to be inspected and they pass through the material and are then captured on film. This film is then processed and the image is obtained as a series of gray shades between black and white.

Radiography(X-Ray Inspection)Radiography(X-Ray Inspection)

The choice of which type of radiation is used (x ray or gamma ) depends on the thickness of the material to be tested. Gamma sources have the advantage of portability which makes them ideal for use in construction site working.

Radiography(X-Ray Inspection)Radiography(X-Ray Inspection)

X-rays and gamma rays are very hazardous. Special precautions must be taken when performing radiography. Therefore the operator will use these inside a protective enclosure or with appropriate barriers and warning signals to ensure there are no hazards to personnel.

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