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Conventional NDT Methods
Visual Inspection is the oldest Inspection technique often regarded as a front line inspection technique before performing additional Inspection methodologies. Visual Inspection relies on a combination of human senses and optical aids to inspect the surface of the item under examination. This Inspection method is applied to almost every product as a quality tool. Visual scanning, inspection or testing can successfully detect surface discontinuities without applying expensive test methods.
Magnetic Particle Inspection
Magnetic Particle Inspection is a surface Inspection method for locating surface or near sub surface discontinuities in ferromagnetic materials (materials that can be magnetised). Magnetic particle Inspection uses an induced magnetic field and small magnetic particles to detect any discontinuities present. This examination can be performed under normal light conditions or if more sensitivity is required Black light conditions (Fluorescent Inspection).
Liquid Penetrant Examination
Liquid Penetrant Examination is a surface inspection method, although considered the least complex of the surface methods it has a wide range of applications. However it does require good surface preparation. The penetrant solution is added to the surface and left to dwell this allows the penetrant time to be drawn in surface breaking discontinuities (Capillary action), the excess penetrant is removed and a Developer is applied to the surface which in turn acts like blotting paper which draws out the penetrant trapped in the discontinuity which produces a visible indication. This examination can be performed under normal light conditions or if more sensitivity is required Black light conditions (Fluorescent Inspection).
Eddy Current Testing ( Welds )
Eddy current testing measures the change in resistivity in the conductive material which makes it useful in wide range of applications including weld testing and coating thickness. This method can detect cracks in surface or near surface as well as coating thicknesses with a minimum of surface preparation.
Hardness measurements are used to quantify the resistance of a material to plastic deformation. The rebound method technique is the processes used to determine material hardness. The hardness correlates linearly with tensile strength this important relation permits economic testing with lightweight, portable equipment.
Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. Ultrasonic testing is a very sensitive test method for detection of volumetric linear discontinuities. Conventional Ultrasonic testing has the capacity of being highly portable therefore cost effective compared to radiography because of the strict radiation safety laws.
Conventional Radiographic Testing
Radiography Inspection is the most commonly known NDT method. This technique is used to obtain permanent images utilizing gamma ray technology (Iridium 192, selenium 75). There are many advantages to radiography including: inspection of a wide variety of material types with varying density, sensitivity to changes in thickness corrosion, voids, cracks the ability to detect both surface and subsurface defects and the ability to provide a permanent record of the inspection.