Question:

How are the hydrotest rules of UG-99 applied to ANSI/ASME flanges?

Answer:

The UG-99 ratio does not apply to ASME B16.5/16.47 rated flanges. "Standard" ASME/ANSI flanges are accepted as standard pressure components per Section VIII Division 1 Paragraph UG-44. The hydrotest rules for ASME B16.5/16.47 rated flanges from the ASME B16.5/16.47 standard rather than the ASME Section VIII code.

ASME B16.5/16.47 does not use the pressure factor approach. Instead, a specified method to calculate the flange MAP permitted. In COMPRESS, this MAP is listed with a "dummy" pressure factor of 1.0.

ASME/ANSI flanges are excluded from UG-99 for the same reason that they are excluded from Appendix 2 calculations. Once the ASME/ANSI rating standard has been invoked those provisions may be used in lieu of the ASME Section VIII Code.

The pressure vessel code does not make any provision for limiting the test pressure (UG-99 and UG-100) based on standard flanges and their test pressure. COMPRESS alerts the designer when the standard flanges may be overstressed at the Section VIII test pressures.

(See http://www.codeware.com/support/faq/1056.html for discussion of testing for flanges designed per Appendix 2)