NDT Level |/|| Course

Liquid penetrant testing is used to detect flaws that are open to the surface in materials such as metals, glass and other non-porous materials. The process works by capillary action which pulls the penetrant into the open flaw. Penetrants may be visible or fluorescent, water washable, solvent removable or post-emulsifiable in four sensitivity levels.It is more sensitive and easy NDT method having very low examination cost. It requires cleaner/remover, penetrant, developer.

This NDT method is accomplished by inducing a magnetic field in a ferromagnetic material and then dusting the surface with iron particles (either dry or suspended in liquid). Surface and near-surface flaws produce magnetic poles or distort the magnetic field in such a way that the iron particles are attracted and concentrated. This produces a visible indication of defect on the surface of the material.

X-rays & Gamma rays passed from Material, expose the film & forms shadow type image.This technique able to detect surface, sub-surface & internal flaws (defects). It generates permanent record on the radiographic film.This method is being used worldwide for weld inspection.

High frequency ultrasonic waves are introduced into a material and they are reflected back from surfaces or flaws.Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features that reflect sound.UT having many advantages like, sensitive to both surface and subsurface discontinuities, depth of penetration for flaw detection or measurement is superior to other methods.UT is relies on operator skill of interpretation.

For weld inspection, Time of Flight Diffraction (TOFD) was quickly recognized that the method was equally effective for the detection of flaws, irrespective of type or orientation.TOFD does not rely on the reflectivity of the flaw but uses the diffracted sound initiating form the flaw tips. TOFD is more popular because it is vey fast recordable UT and having no radiation so very useful for replacing Radiographic Testing also.

Phased array is widely used in several industrial sectors. This method is an advanced NDT method that is used to detect component failures i.e. cracks or flaws and thereby determine component quality. Due to the possibility to control parameters such as beam angle and focal distance, this method is very efficient regarding the defect detection and speed of testing.phased array can also be used for wall thickness measurements in conjunction with corrosion testing.