Liquid Penetrant Inspection

 Liquid Penetrant Inspection

•  It’s defined that is a non-destructive test to just defect open surface in parts made of any nonporous material, is using with equal success on such metals like magnesium, aluminum, copper, brass, cast iron, stainless steel, also used on plastics, ceramics, molded rubber.
•  This type of test detects defects like surface cracks or porosity because this may cause fatigue, shrinkage cracks, cold shuts, heat treat cracks, forging laps are also indicated a lack of bond between joined metals, and have a disadvantage is the defect must be open to the surface in order to let the penetrant get inside the defect.
•  The test uses penetrating liquid is enter in surface opening and remains there and make this clear and visible for the inspector also called visual examination to just increase the visibility of defect to detect and the visibility of penetrating is increase by addition types of dye for visible or fluorescent.
• When we talk about fluorescent penetrant the kit contains a black light assembly and like spray cans of penetrant, developer and cleaner and the visible penetrant of dye remover emulsifier and developer and this light assembly is consist of power transform, handing held lamp and flexible power cable and this lamp use in any location.
• Some steps for penetrant inspection is started by cleaning the metal surface and applying penetrant and then start with remove the penetrant with remover emulsifier and drying the part then apply some developers and finally inspect and give interpret results.

Interpretation of Results :

•  For successful operation of a penetrant inspection depends upon on some basic principle is applying during the penetrant inspection that is the penetrant important to enter in order to form an indication, and allowing sufficient time to the penetrant can fill the defect, and this defect is clean and free from any contamination so the penetrant is free for entering inside.
•  Some indication can’t be formed if all penetrant is washed out of defect when their rinsing operation is prior to development, and possible to remove penetrant form defect like from the surface.
•  The clear or clean cracks are easy to detect by the inspector and some surface opening that is uncontaminated and is regardless of how well are difficult to detect, if the defect is small then the penetrating is take a long time, like fine crack aperture requires a longer penetrant time and defects like pores, is inspected made of material susceptible to magnetism and must be inspected by a magnetic particle inspection method.
•  During the inspection, if there no surface defects so the red indications are visible and if their an indication of red appear mean there is surface defect, penetrant is applying on the surface dries and white coating something, but if we use fluorescent is appear brilliant yellow-green and blue, if there is a big crack has more penetrant is a boarder and more brilliant in this crack.