Design of Nozzle flange under external piping load

When we check the standard flanges for external pipe load, 150# flange will always fail in gasket seating condition if Gasket is SPWD.

Since interpretation no. BPV VIII-1-16-85 does not says that we have to check flange for Gasket seating condition; can we consider m=0 & y=0 value just to prove that flange is safe for external pipe loading.

Regards,
Rajendra

Hello Rajendra

If y and m are set to zero, that means there is no 'squeeze' on the gasket. It is only pressure or squeeze on the gasket that prevents the fluid inside the flange from escaping. I am not familiar with BPV VIII-1-16-85, but it stands to reason that m and y cannot be zero when designing the flange to ASME Section VIII, Division 1, Appendix 2.

Now, UG-23 states that all loadings have to be considered in vessel analysis. So, technically they should be taken into account. However, if standard B16.5 or B16.47 flanges are used, ASME states that no calculation need be performed provided the flanges are within the rated pressures according to B16.5 or B16.47.

It is instructing to read the first couple of paragraph of Appendix S.

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.

-------------------------------------------------------------------------
Sincerely,
Scott Mayeux
Hexagon PPM