JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV Year NON-DESTRUCTIVE TESTING Previous Question Paper (July/August - 2022 - R18)

Visual inspection is the most fundamental NDT method, relying on the human eye, often enhanced by various optical aids to improve detection sensitivity and reach. The primary visual aids include:

• Magnifying Glasses: Used for surface inspection to detect fine cracks, porosity, or surface discontinuities that are otherwise invisible to the naked eye. They typically provide magnification ranging from 2x to 10x.
• Borescopes and Endoscopes: These are rigid or flexible optical instruments used to inspect internal surfaces of hollow components, pipes, or narrow cavities. Modern versions use fiber optics or video cameras (videoscopes) to transmit images to a monitor.
• Mirrors: Simple inspection mirrors, often mounted on telescopic handles, allow the inspector to view hidden or obstructed surfaces, such as the back side of a weld or internal corners.
• Light Sources: High-intensity flashlights, ultraviolet (UV) lamps, and specialized fiber-optic illuminators are essential for providing adequate illumination, especially in deep or dark areas.
• Optical Comparators and Gauges: These are used to measure the dimensions of surface features, such as weld bead height, undercut depth, or pit size, ensuring they fall within acceptable limits.
• Digital Imaging Systems: High-resolution cameras and software are used to capture, store, and analyze images, allowing for objective assessment and digital documentation of surface conditions.

Visual inspection is widely employed due to its simplicity and low cost, but it is restricted to surface-level observations.

Applications:

• Checking the alignment and fit-up of parts before welding.
• Detecting surface-breaking defects like cracks, porosity, and undercut in welds.
• Identifying corrosion, erosion, or mechanical damage on structural components.
• Monitoring the quality of surface finishes, coatings, and plating.
• Routine maintenance checks in pressure vessels, piping, and aircraft structures.

Limitations:

• Surface Restriction: It cannot detect internal defects such as subsurface voids, inclusions, or deep-seated cracks.
• Subjectivity: Results are highly dependent on the inspector's skill, experience, and visual acuity, leading to potential inconsistencies.
• Access Constraints: Requires direct line-of-sight to the area of interest; obstructed or inaccessible regions may be impossible to inspect without disassembly.
• Fatigue: Prolonged inspection can lead to operator fatigue, reducing the probability of detection.
• Documentation Difficulty: Unless digital imaging is used, maintaining a permanent, objective record of the inspection can be challenging.