Final answer:
The question is about welding procedures, specifically when a Welding Procedure Specification (WPS) needs to be requalified, which is when essential variables change. Changes in welder identity do not require requalification, but changes in welding process, consumables, and welding position do.
Step-by-step explanation:
The question pertains to the field of welding and when welding procedures must be requalified. In the context of welding, a welding procedure specification (WPS) provides guidelines for producing a particular weld, and requalification is necessary whenever there is a change in the essential variables that could affect the characteristics of the weld. According to the student's question, there are changes that require requalification of the WPS; however, changing the welder's identity is not one of them. Essential variables typically include factors such as welding process, consumables (e.g., electrode type and size), joint design, base materials, and welding position. If any of these factors are changed significantly enough to possibly affect the weld's properties, a new WPS must be developed and qualified to ensure that the weld will still meet the necessary standards and performance requirements.