Help with ISO 15614 welding document 1

[ME231]

With reference to section 8.3.2.2 of the welding procedure approval document ISO 15614-1, what does the following statement mean:
"For branch connections and fillet welds, the range of qualification shall be applied to both parent materials independently"?
I have a filet weld between two material thicknesses; while we have WPS's for both material thicknesses independently, which WPS would be appropriate for the fillet weld (i.e. WPS for the thinner weld or that for the thicker weld?)
Any advice from the forum is greatly appreciated!
Thanks a lot.

 

[GenB]

the range of qualification..
you wps shall be able to support both thicknesses,
no need of 2 wps's but write one to cover both t's
according to suppporting pqr's
genblr