Visual Testing (VT) is one of the most common and most powerful means of non-destructive testing. Visual testing requires adequate illumination of the test surface and proper eye-sight of the tester. VT can be classified as Direct visual testing, Remote visual testing and Translucent visual testing. Often the equipment needed is simple for internal inspection, light lens systems such as bore scopes allow remote surfaces to be examined. More sophisticated devices of this nature using fibre optics permit the introduction of the device into very small access holes and channels. Most of these systems provide for the attachment of a camera to permit permanent recording. It is very simple method to use. Visual is lower cost but effective tool for welding inspection. Direct Visual inspection can be use in welding, casting, forging, Etc. for Surface discontinuities in different industries like piping systems, oil & Gas refinery, Pressure Vessels, Storage Tanks, Remote Visual Inspection can be used in small accessible area which cannot checked by direct Visual Inspection.
Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and thickness measurement. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. In the inspection, ultrasound is sent into the area of interest by straight beam or angular beams. This method is good for detecting internal discontinuities. Ultrasonic can be done on all type of materials and forms like casting, welding, forging, rolled products and composite. The advantages of Ultrasonic Testing is it provides instantaneous result, Testing can be highly portable or high automated, Nonhazardous, Highly accurate, minimum part preparation is required and low cost.
Magnetic Particle Inspection (MT) is a non-destructive test method for the detection of surface and sub-surface discontinuities in ferrous materials only. The test method involves application of magnetic field externally or applying electric current through the material which in turn produces magnetic flux in the material. Simultaneously, visible ferrous particles on sprinkled or sprayed on the test surface. The presence of a surface or near surface discontinuities in the material causes distortion in the magnetic flux which in turn causes leakage of the magnetic fields at the discontinuity and magnetic particles are attracted by the surface field in the area of the discontinuity. MT can be used on casting and forgings and Welding.
Liquid or dye penetrant testing (PT) is a non –destructive method for finding discontinuities that are open to the surface of solid and essentially non-porous materials. Indications of flaws can be found regardless of the size, configuration, internal structure, or chemical composition of work piece being tested and regardless of flaw orientation. Liquid penetrant can seep into (and be drawn into) various types of minute surface openings by capillary action. Because of this, the process is well suited for the detection of all types of surface cracks, laps, porosity, shrinkage areas, lamination and similar discontinuities in casting, forgings, welds and other product forms. Advantage of PT are that it can be check all type and shapes, Very low cost, it can be use on field and also for mass production. In PT we have all type of set up for Visible or fluorescent testing water washable, post-emulsifying and solvent technique.