What is the requirement for interpreting RT Requirements for vertical joints on the tank shell with a plate thickness of ≤ 3/8 in?

• A. Initial spot radiograph for every 50 feet
• B. Initial spot radiograph for the first 10 feet
• C. No radiographs required
• D. Complete weld inspection every 25 feet

Answer: (B)

The requirement for interpreting radiographic testing (RT) for vertical joints on tank shells with a plate thickness of 3/8 inches or less is the necessity of an initial spot radiograph for the first 10 feet of weld. This approach reflects industry practices where the initial segment of the weld is inspected thoroughly to ensure that it meets the required standards. Conducting this initial spot radiograph allows for the identification of any potential defects early in the construction process, ensuring that the quality is maintained from the outset.

This requirement helps to establish a baseline for the weld quality and provides confidence in the integrity of the tank shell. By focusing the radiographic inspection on the first 10 feet rather than the entire length, it allows for a practical balance between quality assurance and efficiency, while still adhering to the standards outlined in API 650.