For horizontal joints, what is the initial spot radiograph requirement?

• A. First 5 feet of horizontal welds
• B. First 15 feet of horizontal butt joints
• C. First 10 feet of completed horizontal butt joints
• D. First 20 feet of horizontal welds

Answer: (C)

The initial spot radiograph requirement for horizontal joints focuses on ensuring that the quality of welds is thoroughly assessed. The requirement specifies that the first 10 feet of completed horizontal butt joints must be radiographed. This means the radiograph is specifically performed to verify the integrity, alignment, and overall quality of the weld in this critical section, helping to identify potential defects that could lead to failures during service.

By establishing a requirement for the first 10 feet, this standard ensures a balance between thorough inspection and economic feasibility, as this portion is typically representative of the weld's quality. Radiographing this segment allows inspectors to ensure that any issues with the welding process are caught early, which is particularly important in horizontal welds that can experience different stresses than vertical ones. This methodology reflects the importance placed on verifying critical welds where potential failures could have significant operational consequences in oil storage applications.