Dear members

as well known, rigidity calculation is now officially mandatory for ASME VIII- DIV. 1 and this force designers to often increase thickness of flanges in order to ensure proper tightness.
There is an option in flange dialog of PVELITE 2008 ed. to disable rigidity check, so questions are:

1) in case vessel is not required to have a code stamp, is designer allowed to waive ASME appendix 2-14 in calculation of flanges ?

2) code case 2547 was supposed to work until April of 2008. Is still this code case valid, in order to get chance of restricting flanges fabrication costs ?
Did ASME approve again a code case that allows users to waive par. 2-14 for 18 months and to verify elseway flange flexibility ?

Thank you.

S. Bravi

(Rome - Italy)

Bongiorno Stefano,

As you have noticed, the PV Elite lets you decide to disable or not the rigidity check, because of the large variety of applications for these flanges. For example, you wouldn't disable the rigidity calculation for an exchanger girth flange design, because you know, it will never seal if the flange is too thin, bolt spacing close to the uper limit. You would rather increase the thickness by 8-10% over the calculated thickness, sometimes even more. However, a non-standard flange for a piping connection, relative small diameter, you would rather disable the rigidity check to save a buck (again, only for non stamped vessels). Also, note that the flat face flanges are not governed by the Appx 2, hence you don't need the rigidity check.
As far as I know, the 2547 is still valid and you can use other means of ensuring the required flange rigidity.

Could anybody post the text of CodeCase 2547 ?
I can't find it anywhere.

Dear Friend,

Whether your vessel is Code stamped or non code stamped, if your design Code is ASME Section VIII, Div-1, then said paragraph of Appd-2 is mandatory to follow except for following.

Flange rigidity calculations can be disregarded per followings for specific cases:

As per Appendix 2-14 of Addenda-2008, “Successful service experience may be used as an alternative to the flange rigidity rules for fluid services that are non lethal and non flammable and designed within the temperature range of -20 ˚F (-29 ˚C) to 366 ˚F (186 ˚C) without exceeding design pressures of 150 psi (1035 KPa)"

Also note that "It is the opinion of the Committee that alternatives may be used for design of flange rigidity in lieu
of the rules in Appendix 2-14. Acceptable alternatives
include successful service experience with a specific
design, or any method that satisfies the requirements of
U-2(g). This Case number (~2547) shall be recorded on the Manufacturer’s
Data Report."

Regards,

Mukesh

Thank you Mukesh!