Purav,

There is an interpretation from ASME which indicates that you do not have to consider the bolt stress ratio for the standard flanges, but only for the appendix 2 flanges.

Here is that interpretation,

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Interpretation: VIII-1-89-287
Subject: Section VIII, Division 1 (1986 Edition, 1988 Addenda), UG-99(b)
Date Issued: March 14, 1991
File: BC89-319

Question: Under the provisions of UG-99(b), may the ratio (S test temperatures design temperature) for the bolting material be used in calculating the required hydrostatic test pressure if it results in the lowest ratio for the material of which the vessel is constructed for:

(1) bolted flange connections designed per Appendix 2?
(2) bolted flange connection which comply with an ANSI product standard or a Manufacturer's standard as permitted in UG-11?

Reply:
(1) Yes.
(2) No; the limiting hydrostatic test pressure shall be established in accordance with the applicable standard

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So, the real question is what kind of flange do you have attached on the end of the flange. If it is a custom flange, then Ray's post above is appropriate. Other wise for standard flanges the above interpretation provides guidance to ignore the bolt stress ratio.