CRI Radiographic Film Interpretation 1 — Questions and Answers
Question 1: What is the primary purpose of radiographic film interpretation in welding?
- To visually inspect weld surface only.
- To detect internal weld defects nondestructively. (Correct answer)
- To test weld tensile strength.
- To measure weld temperature.
Correct answer: To detect internal weld defects nondestructively.
The primary purpose of radiographic film interpretation in welding is to detect internal weld defects non-destructively. Unlike visual inspection, radiography can reveal hidden flaws such as porosity, cracks, lack of fusion, and inclusions within the weld metal, without damaging the component. This ensures the structural integrity and quality of the weld.
Question 2: Which defect appears as a dark area on radiographic film?
- Porosity. (Correct answer)
- Cracks.
- Lack of fusion.
- Undercut.
Correct answer: Porosity.
Porosity, which consists of gas pockets or voids within the weld, appears as dark areas on radiographic film. These voids are less dense than the surrounding solid metal, allowing more X-rays or gamma rays to pass through and expose the film more heavily in those regions. This increased exposure results in a darker image on the film.
Question 3: What is the effect of weld overlap on radiographic film?
- Shows as a uniform weld bead.
- Appears as excess weld metal beyond fusion line. (Correct answer)
- Causes dark shadows everywhere.
- No effect on film.
Correct answer: Appears as excess weld metal beyond fusion line.
Weld overlap is characterized by excess weld metal that extends beyond the fusion line without properly fusing with the base material. On radiographic film, this appears as an area of increased density (lighter) because the extra material absorbs more radiation. The answer correctly describes the visual characteristic of the defect itself as seen on the film.
Question 4: Which interpretation technique uses density variations to identify weld defects?
- Magnetic particle inspection.
- Visual inspection only.
- Radiographic interpretation. (Correct answer)
- Ultrasonic testing.
Correct answer: Radiographic interpretation.
Radiographic interpretation is a technique that specifically uses density variations to identify weld defects. X-rays or gamma rays pass through the weld, and variations in material thickness or density (e.g., due to voids or inclusions) cause differential absorption of radiation. These differences are recorded on film as varying shades of gray, allowing defects to be identified.
Question 5: How does lack of fusion appear on radiographic film?
- Continuous bright line.
- Dark line or gap indicating poor fusion. (Correct answer)
- Uniform density.
- No visible defect.
Correct answer: Dark line or gap indicating poor fusion.
Lack of fusion on radiographic film appears as a dark line or gap, indicating an area where the weld metal has not properly melted and bonded with the base metal or previous weld passes. Since there is no material or poor bonding in this region, more radiation passes through, resulting in a darker indication on the film.
Question 6: What is the recommended viewing distance for interpreting radiographic film?
- Close to the film surface.
- Approximately arm’s length. (Correct answer)
- Far from the film.
- Any distance is fine.
Correct answer: Approximately arm’s length.
The recommended viewing distance for interpreting radiographic film is approximately arm’s length (typically 12-18 inches or 30-45 cm). This distance allows the interpreter to view the entire image while maintaining sufficient detail perception and minimizing eye strain. It helps in identifying subtle density changes and defect indications.
Question 7: Which equipment is essential for radiographic film interpretation?
- Welding machine.
- Light box. (Correct answer)
- Magnetic probe.
- Ultrasonic scanner.
Correct answer: Light box.
A light box, also known as an illuminator or view box, is essential equipment for radiographic film interpretation. It provides uniform, high-intensity backlighting, which is crucial for clearly viewing the varying densities and subtle indications on the radiographic film. Without proper illumination, defects can be easily missed.
Question 8: What is a common cause of film fogging in radiography?
- Proper shielding.
- Exposure to light before processing. (Correct answer)
- Correct storage.
- Using fresh film.
Correct answer: Exposure to light before processing.
A common cause of film fogging in radiography is exposure to light before processing. Radiographic film is highly sensitive to light, and even brief exposure to ambient light can chemically alter the emulsion. This leads to a uniform darkening or 'fogging' of the film, which reduces contrast and obscures the details of the radiographic image.
Question 9: Why is experience important in radiographic film interpretation?
- To speed up welding.
- To accurately identify defects and avoid errors. (Correct answer)
- To avoid using safety equipment.
- To ignore minor defects.
Correct answer: To accurately identify defects and avoid errors.
Experience is paramount in radiographic film interpretation because it enables the interpreter to accurately identify and classify defects, and to differentiate between actual flaws and film artifacts or acceptable indications. An experienced interpreter can make informed judgments about the severity of defects, ensuring reliable quality control and preventing costly errors.
CRI Radiographic Film Interpretation 1
What is the primary purpose of radiographic film interpretation in welding?