ASME VIII DIV 1 Section Y: Flange Thickness Formulae

[gvalves0164]

ASME Section VIII DIV 1 Appendix Y states that the rules apply to flat Face, Identical and Non-Identical Flange Pairs where uniform metal to metal contact occurs outside bolt circle. In addition, it states that rules apply for negligible gasket loads (ie. Pressure Energized O-ring Body Seal) HG=0. My question is if spiral wound gaskets are utilized for Body Sealing, do rules apply for using HG*hg in the formula for Flange Thickness Calculations?

 

[saplanti]

This section, Appx Y does not provide a calculation method for the use of spiral wound gaskets between flanges. Check Appx 2 instead.

 

[gvalves0164]

Appx 2 rules do not apply for metal to metal contact outside bolt circle and do not take into account the added stiffness contribution between body/end plate flanges; ultimately resulting in thinner flange thickness values. Re-reading Section VII DIV 1; Appx Y-1(b)".....It assumes that the seal generates a neglible axial load under operating conditions. If this is not the case, allowance shall be made for a gasket load HG dependent on the size and cnfiguration fo the seal and design pressure...". I interpret this to cover non-pressure energized sealing methods (ie. spiral wound gaskets vs o-rings).

 

[saplanti]

If you read Appx 2 carefully the largest tightening forces are from the gasket seating in case the gasket is spiral wound. In case of o-ring gasket the force is almost zero. Same for the Appx Y as well.

Additionally, the sprial wound gasket is going to engage a gap between flange faces, and and gasket seating force is to give the leak tighness. Therefore you will loose the contact on the metal surfaces outside the bolt PCD. So your flange is going to act similar to the flanges which is calculated in accordance with Appx 2. Therefore Appx 2 still applies.

If you embed the gasket in a cavity in accordance with Appx Y you can not be sure the leak tightness is provided. I have not seen a supporting paper for this kind of application. I would like to see if there is one.

Please remember that the flange types and their applications have very large number of tests and papers behind. It was not decided in a day. Thereore the applications are limited. In case you can provide a reasonable calculation and this can be proven in certain number of application for some time, it may go into code. You never guess without trying. But your approach should be logical and considers all the requirements.

 

[saplanti]

The third paragraph in my last comment is for spiral wound gasket only.

Regards,