NDT - Non-Destructive Testing Visual Testing Fundamentals Questions and Answers — Questions and Answers
Question 1: An inspector is performing a direct visual examination of a weld on a pressure vessel. According to common NDT standards, what are the typical requirements for viewing distance and angle?
- Within 48 inches and at an angle not less than 45 degrees.
- Within 24 inches and at an angle not less than 30 degrees. (Correct answer)
- Within 36 inches and at an angle between 30 and 60 degrees.
- There are no specific requirements for distance or angle.
Correct answer: Within 24 inches and at an angle not less than 30 degrees.
Most NDT standards for direct visual testing, such as ASME Section V, Article 9, specify that the eye should be within 24 inches (600 mm) of the surface being examined and the viewing angle shall not be less than 30 degrees to the surface.
Question 2: Which of the following is a primary advantage of using a videoscope over a traditional fiberscope for remote visual inspection?
- Videoscopes do not require a light source.
- Videoscopes are typically more flexible and have a smaller diameter.
- Videoscopes produce a higher resolution digital image that can be easily recorded and stored. (Correct answer)
- Fiberscopes are more durable and less prone to damage.
Correct answer: Videoscopes produce a higher resolution digital image that can be easily recorded and stored.
A key advantage of a videoscope is that it uses a miniature camera at the tip to capture a direct digital image, resulting in higher resolution and clarity. This digital format allows for easy recording, storage, and sharing of the inspection data. Fiberscopes transmit images through a bundle of optical fibers, which can result in lower resolution and are prone to damage (appearing as black dots).
Question 3: A visual inspector is examining a large, highly polished stainless steel surface and is having difficulty with severe glare, which is obscuring potential fine cracks. Which of the following actions would be MOST effective in mitigating the glare?
- Increasing the intensity of the light source directly perpendicular to the surface.
- Using a magnifying glass with a built-in light.
- Changing the angle of the light source and/or the viewing angle. (Correct answer)
- Cleaning the surface again with a solvent.
Correct answer: Changing the angle of the light source and/or the viewing angle.
Glare, or specular reflection, occurs when light reflects directly off a smooth surface into the inspector's eyes. The most effective way to reduce this is to change the geometry of the lighting and viewing setup. By adjusting the angle of the light source or the angle from which the surface is viewed, the direct reflection can be directed away from the eyes, allowing for a clearer view of the surface. Increasing direct light would worsen the glare.
Question 4: Which of the following human factors is most likely to negatively impact the reliability of a visual inspection by causing an inspector to misinterpret or fail to recognize a relevant indication?
- Color blindness, when inspecting a monochrome surface.
- Having above-average near-vision acuity.
- Mental fatigue from long hours of inspection. (Correct answer)
- Familiarity with the inspection procedure.
Correct answer: Mental fatigue from long hours of inspection.
Mental fatigue has a significant negative impact on tasks requiring vigilance, like visual inspection. It can reduce an inspector's ability to process information accurately, leading them to miss indications or even see things that are not there. While other factors can play a role, fatigue is a critical human element affecting performance and reliability.
Question 5: An inspector is tasked with performing a visual inspection on the internal bore of a long, narrow pipe that is inaccessible by direct line of sight. Which of the following would be considered an indirect visual testing technique suitable for this task?
- Using a flashlight and a mirror to view the inside from the pipe opening.
- Using a set of calipers and a depth gauge to measure internal features.
- Employing a borescope to navigate and view the internal surface. (Correct answer)
- Conducting a liquid penetrant test on the exterior of the pipe.
Correct answer: Employing a borescope to navigate and view the internal surface.
Indirect visual testing is used when direct line of sight is not possible. It involves using tools like borescopes, fiberscopes, or videoscopes to view the area of interest remotely. Using a mirror at the opening is a form of direct VT (aided), while calipers are for measurement, and penetrant testing is a different NDT method.
Question 6: During the visual inspection of a completed weld, which of the following is NOT typically considered a primary objective of the examination?
- Identifying the internal grain structure of the weld material. (Correct answer)
- Detecting surface-breaking discontinuities such as cracks or porosity.
- Verifying the weld's dimensions and profile against specifications.
- Assessing the overall conformity and surface finish of the weld.
Correct answer: Identifying the internal grain structure of the weld material.
Visual testing is a surface examination method. Its primary objectives include detecting surface flaws (cracks, porosity, undercut), checking weld geometry (size, profile), and assessing overall finish. Determining the internal grain structure is a metallurgical characteristic that requires other methods, such as destructive testing (sectioning and etching) or advanced ultrasonic techniques, and cannot be determined by visual inspection.
NDT - Non-Destructive Testing Visual Testing Fundamentals Questions and Answers
An inspector is performing a direct visual examination of a weld on a pressure vessel.
According to common NDT standards, what are the typical requirements for viewing distance and angle?