ASME IX QW-402.10 variable


QW-402.10 A change in the specified root spacing.

Note: The change in the root spacing is frequently addressed by manufactures on separate sheet or by addressing it on fabrication drawing just like joint designs. Root spacing and root gap are used as interchangeable. Do not be confused with these two terms.

A root gap from “0 to 50mm (2”)” can be covered by ASME IX, however, a request may be made to have the WPS requalification for the “big” gap if the WPS was not carefully written according to ability of welding technology or welding process to make a sound weld with full penetration as product requires.

Be sure to include the Root spacing range in WPS, because it could make problems to users if it not addressed properly or not addressed. A change in the specified root gap in WPS will require Revise WPS.


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 know well on welding and are familiar with welding metallurgy.

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