Non-Destructive Testing
Meaning ~ Inspection techniques that evaluate the internal structure of manufactured materials without causing damage represent a formal verification category.
Visual Testing
Meaning
Primary benchmarks for surface quality assessment rely on the optical observation of a component to verify compliance with physical specifications. The method of visual testing is usually the first step in any quality control program. It involves looking for surface cracks, weld defects, dimensional errors, and corrosion.
While it seems simple, it requires a systematic approach to ensure that no part of the component is overlooked.
Observational Baseline
Lighting levels and the angle of view are the most important environmental factors. During visual testing the inspector needs at least 100 foot-candles of light to see small details. Using a flashlight or a mirror helps to see into hidden corners and internal bores.
The human eye remains the most versatile tool for detecting subtle changes in color or texture.
Inspection Aid
Tools like magnifiers, boroscopes, and gauges extend the capability of the inspector. In visual testing a weld gauge is used to measure the height and width of a bead. Digital cameras allow for the remote inspection of hazardous areas or high structures.
These devices provide a way to document the findings for later review by the client.
Evaluative Limit
Subjectivity in the interpretation of a surface condition can lead to disputes between the supplier and the buyer. Visual testing cannot find flaws that are hidden beneath the surface of the metal. Fatigue or poor eyesight of the inspector significantly reduces the reliability of the results.
Detailed checklists and acceptance criteria are used to minimize the variation between different observers.