Under what circumstances tube to tubesheet joint may become non-pressure retaining weld? (please see the text withing the prenthesis of QW-202.6(c) ).
I assume tube-to-tube sheet joint shall be non-press retaining weld when fillet weld (between tube and tube sheet) acts as a seal weld like when tubes are joined by expansion and fillet weld just acts as a seal weld. Is it correct?

In this case tube-to-tubesheet joint may be qualified simply as a fillet weld.

Secondly, in which paragraph Section VIII Division 1 invokes the requirements of QW-193?

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Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

Nasir,

I would agree to your first idea: when the tube is expanded, the fillet weld may be considered non-pressure retaining. As a consequence, the weld may be qualified by fillet weld only.

Section VIII Div. 1 does not reference QW-193. So this qualification is not required. Under U-2(g) we use it sometimes, when reaonable.

DK