QW-402.11 The addition or deletion of nonmetallic retainers or non-fusing metal retainers. See: Backing vs Retainer in Welding
This variable is used so little that makes people have forgotten what it means. It primarily used with the Electroslag welding process. In the case of SMAW process, however, it has the same meaning with backing.
Retainers refer to those applications where some non-metallic means is used to keep weld puddle from flowing out of the groove, and in general that it will be in high heat input welding procedure.
Remember that the WPS needs not be one piece of paper. During fabrication, a WPS may content fully nonessential variables, because of the fabrication drawing may show the “specific” type of butt-joint and it may become a part of WPS. Keep in mind that a manufacturer can place other restrictions on WPS even it is nonessential variable to make their product achieving the state of art on the top highest-quality company.
Review Table QW-253 in general welding processes, on the Nonessential Variables. The nonessential variables are items that must be considered and addressed on WPS, however, they need not be considered nor addressed on the PQR. Note that a PQR can be in compliance with ASME IX even if nonessential variables are not addressed or are incorrectly addressed on PQR.
Come back the definition of Nonessential: ASME IX has already given the Minimum Variables that must be considered. Nonessential variables normally will not affect the mechanical properties of a weldment.
There’s no guarantee, however, the nonessential variables will not affect the mechanical properties of a weld. Because ASME IX assumes that manufacturers have access to welding engineers as well as a metallurgist. ASME IX is not a “How to Weld” book, but be intended to be used by those who knows well on welding and are familiar with welding metallurgy.