When does a PQR/WPS essential variable for FCAW require requalification?

A Procedure Qualification Record (PQR) and Welding Procedure Specification (WPS) establish the parameters and guidelines for qualifying welding procedures in compliance with the AWS D1.1 standard for structural welding. An essential variable is a change in welding conditions that necessitates the requalification of the procedure due to potential impact on the weld properties.

In this case, the position of welding is classified as an essential variable. Different positions (flat, horizontal, vertical, overhead) can drastically affect the weld quality due to gravity's influence on molten weld metal, shielding gas coverage, and heat distribution. Since these factors can change the mechanical properties of the weld, any alteration in the position requires requalification to ensure that the weld meets the necessary standards.

Changes in filler material, welding process, or joint type are also considered essential variables that can necessitate requalification. However, in the context of the question, the crucial factor identified is the change in welding position, which is particularly important because it directly alters how the welding is performed and the resulting integrity of the weld.