To qualify for the S classification, is a stop and restart required in the root of the groove?

• A. Yes
• B. No
• C. Only for some joint types
• D. Not specified

Answer: (A)

When qualifying for this classification, the root of the groove is treated as a test of control during an interruption. Stopping and restarting right in the root shows you can re-ignite the arc cleanly and achieve proper fusion with both the root and the previously deposited bead. The root is the most critical part for weld integrity, so demonstrating a controlled restart there ensures the weld will fuse correctly even after a pause, without creating defects such as lack of fusion or porosity. That’s why the requirement is to stop and restart in the root. Other scenarios, like stopping elsewhere or welding continuously, don’t fulfill this specific condition.