Hello Rajendra,

Unmodified ANSI Standard flanges do not need to be evaluated per Appendix 2 of Division 1, but they should of course be able to withstand the worst case external load conditions due to the piping weight, forces and moments.

This usually involves de-rating the flange MAWP based on an industry standard method. In the past, the conservative Kellogg equation has been used successfully.

There is also a paper (PVP2013-97814) that outlines acceptability of standard flanges with known loadings. This method and others are available in PV Elite 2018.

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Sincerely,
Scott Mayeux
Hexagon PPM