How frequently are additional spot radiographs required for horizontal joints?

• A. Every 100 feet
• B. Every 200 feet
• C. Every 300 feet
• D. Every 50 feet

Answer: (B)

The classification of "every 200 feet" as the frequency for additional spot radiographs for horizontal joints aligns with the recommendations set forth in API 650 standards. This guideline is aimed at ensuring the integrity and quality of welds in storage tanks, particularly those under pressure or in critical service.

In the context of horizontal joints, the rationale behind this frequency is to maintain a balance between adequate inspection and practical oversight, allowing for thorough weld evaluation while minimizing excessive inspection costs and time delays. The required radiographs help identify and address any defects in the welds that could compromise the tank’s safety and performance.

Set intervals facilitate a systematic approach to quality assurance without overwhelming the inspection process with redundant testing. Understanding this standard practice is essential for compliance with industry safety regulations and for ensuring the structural integrity of welded tanks.