thanks, i've found the answer in ASME Interpretations, maybe someone else is interested:
http://cstools.asme.org/InterpretationsPDF/BPVC-IX%20Interp_Stnd-55_2004.pdf"Question: A combination weld process PQR was qualified using the GTAW for the root pass, SMAW,
and SAW. May this PQR support aWPS for welding with only one or two of the processes shown on the PQR?
Reply: Yes, provided the following are met:
(a) The remaining essential, nonessential, and supplementary essential variables, when applicable, are
applied.
(b) The base metal and deposited weld metal thickness limits of QW-451 are applied"
Vitt