What must happen to essential variables if they are modified?

When essential variables are modified, requalification is necessary to ensure that the welder can still produce welds that meet the specified standards and requirements. Essential variables are critical factors in the welding process that can significantly affect the quality and integrity of the welded joint. Changes in these variables can alter the characteristics of the weld, such as its mechanical properties, the risk of defects, and overall performance.

Requalification involves reassessing the welder's ability to perform under the new conditions to confirm that the quality of work complies with relevant codes or standards, thereby ensuring safety and reliability in the welding process. This process is vital in maintaining the integrity of welded structures or components, as failing to requalify after essential variable modifications could lead to substandard work or potential failures in service.