If a welder is qualified to multiple qualification on 12.750 250 pipe under api 1104 can he roll out weld a 20 500 weld?

No, a welder qualified under API 1104 for 12.750 250 pipe cannot automatically roll out weld a 20 500 weld. Each welding procedure qualification (WPQ) is specific to certain variables, including pipe diameter and wall thickness. The welder would need to demonstrate qualification for the new pipe specifications to ensure compliance with safety and quality standards.