QW-401.3 Supplementary Essential Variable

[TheYoungOne]

Good Evening All,

A customer of ours requested we supply WPQR/WPS for a project we ere getting ready to start. Pressure vessels are 316L welded with 316L Filler. Our WPQR was qualified on 304L with 304L Filler.

We have a 316L WPS showing the different classification of the filler metal and grade of base metal but support this WPS with existing WPQR qualified on 304L.

Per our interpretation this is allowable as base metals share the same P-No/Gr No., F-No. and A-No. Only thing that is changing is the classification which per QW -404.12 is a supplementary essential.

Per QW401.3 A supplementary essential is defined as being a change in a welding condition which will affect the notch-toughness properties of a weldment (for example, change in welding process, uphill or down vertical welding, heat input, preheat or PWHT, etc.) None of this is changing.

However, neither material has undergone notch toughness testing as impact testing is exempt on these materials. My question is this, if both materials haven't been tested how do we support the fact that a change in the notch-toughness properties hasn't actually occurred?

 

[TheYoungOne]

**QW 256 Table for Gas Tungsten-Arc Welding shows this as an Supplementary Essential Variable. QW-404.12 gives further definition.**

 

[TheYoungOne]

I may have answered this question my self upon further review but would ask that someone second my interpretation before using it for our justification.

If you refer to QW-251.2 Essential variables for Welding Procedure Specifications it reads: "Essential Variables. Essential variables are those in which a change, as described in the specific variables, is considered to affect the mechanical properties of the weldment, and shall require requalification of the WPS. Supplementary essential variables are required for metals for which other sections specify notch-toughness tests and are in addition to the essential variables for each welding process."

Metals are exempt from impact testing per UHA51 therefore notch-toughness testing is not required. Supplementary essential does not apply.