What should the minimum length be for each diagnostic spot radiograph?

• A. 4 inches
• B. 6 inches
• C. 8 inches
• D. 10 inches

Answer: (B)

The minimum length for each diagnostic spot radiograph should be 6 inches. This requirement is based on the need for adequate coverage of the weld area being evaluated. A spot radiograph provides a focused examination of specific sections of a weld, and a length of 6 inches is typically sufficient to capture the key characteristics and any potential defects present in the weld.

Using a radiograph that is too short could potentially miss crucial areas of concern or fail to adequately demonstrate the quality of the weld joint. The established guideline ensures a balance between obtaining necessary detail and maintaining practical radiographic practices during inspections. In most standards, including those governing weld quality in tank construction, specifications such as this are vital for ensuring safety and integrity in operations involving welded tanks for oil storage.

This standard reinforces the principle that accurate and thorough inspections are critical for the longevity and reliability of storage tanks, which are subject to significant service conditions.