T.O. 33B-1-12-52.1.9 AdvantagesandCapabilitiesofLiquidPenetrantInspection.a. Liquid penetrant inspection is capable of examining all of the exterior surfaces of objects. Complexshapes can be immersed or sprayed with penetrant to provide complete surface coverage. Othernondestructive methods cover a specific area or location and must then be repeated to cover other areasor locations.b. Liquid penetrant inspection is capable of detecting very small, surface discontinuities. It is one of themore sensitive nondestructive inspection methods for detecting surface flaws.c. Liquid penetrant inspection can be used on a wide variety of materials: ferrous and nonferrous metalsand alloys, fired ceramics, powdered-metal products, glass, and some types of organic materials.Restrictions of the penetrant application are listed in paragraph 2.1.11.d. Liquid penetrant inspection can be accomplished with relatively inexpensive, non-sophisticatedequipment. If the area to be inspected is small, the inspection can be accomplished with portableequipment.e. Liquid penetrant inspection magnifies the apparent size of discontinuities making the indications morevisible. In addition, the discontinuity location, orientation, and approximate length are indicated on thepart, making interpretation and evaluation possible.f. Liquid penetrant inspection is readily adapted to volume processing permitting 100 percent surfaceinspection. Small parts may be placed in baskets for batch processing. Specialized systems may besemi- or fully automated to process as many parts per hour as required.g. The sensitivity of a penetrant inspection process may be adjusted through selection of materials andtechnique. This allows suppression of indications from small, inconsequential discontinuities whileindicating larger discontinuities of more concern. Figure 2-3 shows indications from two penetrantinspection processes of different sensitivity levels.Figure 2-3. Cracked, Brittle Iron-Plated Coupon Showing the Inspection Results from Two FluorescentPenetrant Inspection Processes of Different Sensitivities.2.1.10 DisadvantagesandLimitationsofLiquidPenetrantInspection.WARNINGPenetrants, emulsifiers, and some types of developers have very good wetting anddetergent properties. They can act as solvents for fats and oils. If they are allowedto remain in contact with body surfaces for extended periods, they may cause skinirritation.
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