AWS prequalified WPS for 3/4" stainless steel 1

[ltan]

I'm tying to prepare a prequalified WPS in groove weld flat position with complete penetration using GTAW. I've checked AWS 1.6 chapter 3 table 3.1 but I'm confused about what "Mean plus minus 25%" is. Is there an exact "Mean" value published somewhere? Any help will be most appreciated.

 

[GRoberts]

The "mean" value referred to in table 3.1 is a value the WPS writer needs to come up with, as long as it meets the other requirements for a prequalified WPS. All the table is trying to say is that you cannot write a WPS with excessive parameter ranges. Such as if you were writing a FCAW WPS for 1/16" wire, you might have an average, or "mean" amperage of 250A, so with one WPS, the amperage range could be 225-275A. If you need a lower amperage procedure for out of position welding, or thinner material, and want to use 180A, you would have to write a different prequalified WPS.