Appendix 2 Flange Calculation cannot verifies a Stand ANSI flange

[wangzh2k]

Hi all,

When I use Appendix 2 to verify ANSI flange, why the calculated flange thickness is not equal to ANSI standard thickness?

In other words, if I design a non-standard flange, can I use appendix 2 to design it?


Thanks in advance.

 

[SnTMan]

wangzh2k, you most assuredly can design a non-standard flange with Appendix 2.

As for your ASME (no longer ANSI) standard flanges, while I am not sure of the exact reasons, it is well known these do not meet Appendix 2 design. I believe that at least part of the reason is they are typically much over-bolted compared to Appendix 2 design.

Try a site-search, this has been discussed before.

Regards,

Mike

 

[TGS4]

SnTMan is right, this topic has been gone over many times on this site. It's a well-know fact that ASME B16.5 flanges will fail the ASME Section VIII, Division 1, Appendix 2 calculations.

 

[wangzh2k]

Thanks for your posts.

I have a problem about a flange connection.

A gasket with 285mm OD x 250mm ID doesn't match raised face 285mm OD X 200mm ID of one flange (Type 11 PN63). The other is a 285mm OD X 250mm ID flange fitting. If the flange and the gasket can pass the stress verification per Appendix II, Could I say that connection has no problem?

 

[SnTMan]

wangzh2k, not sure what "Type 11 PN63" means, but it sounds if you are bolting up two flanges of different bore (pipe ID). ASME B16.5 flanges are rated independent of bore, so I'd say you are OK without proof required, if I understand your question.

Regards,

Mike

 

[PVinspector]

Read the Scope of Appendix 2 carefully. The gasket must be entirely inside the bolt circle, no full face gasket allowed. If the flange meets the scope of App. 2 as far as no metal to metal contact outside the bolt circle, and it passes the strenght calculations, and it complies with the attachment details, then you are OK. When using a full face gasket there are no rules provided in Section VIII Div. 1. Also, you do not have to verify an ANSI flange if it complies with one of the ANSI stanndards referenced in table U-3 of Section VIII.

 

[dig1]

This thread is talking about ANSI (ASME) flanges but the nomenclature PN63 Type 11 is typically used for EN 1092-1 (DN) flanges. EN 1092-1 flanges are not ASME B16.5 flanges so the flanges would have to met the requirements of Appendix 2 (provided it is not a full face gasket as has been described above). Basically, you end up with thicker flanges than in the EN 1092-1 spec, in part because of the rigidity requirements. I have ran into this problem before when EN flanges are specified on ASME vessels.

I hope I have not misinterpreted the question.

Patrick