Gasket load at operating condition ASME VIII-1 Appendix 2 2

[aaloui]

Hi,
I would like to know your opinion about the expression of the gasket load at operating condition termed HG in the appendix 2 of ASME BPVC VIII-1.
There, it is defined as Wm1-H=H+Hp-H=Hp, means the required gasket load at operating condition, only the required.

The problem is that W can be much higher than Wm1 and I have such a case. The initial bolt load is equal to W which balances the initial gasket load. As the pressure is applied, and assuming that bold load remain unchaged (stiffness gasket>>stiffness bolt), then the actual (operating) gasket load would be W-H > Wm1-H=Hp.

It means the actual operating gasket reaction load is higher than given by the formula of HG in the code, resuting in higher moment and nonconservative result when using HG expression of the code exactly as it is defined.

The problem lies in the definition of HG through Wm1, the minimum required bold load at operation. I would suggest HG=W-H.


I appreciate if you can share your opinion.
Regards
Ali

 

[david339933]

HG does = W-H for the operating condition, as W = wm1 for the operating condition.
There are two different values for W, operating and gasket seating.

 

[aaloui]

Hi David,

thank you for your answer.
Actually Wm1 is only the minimum required bolt load at operating condition, in many cases you have to preload the bolt more than required by wm1, for example if wm2>wm1 and/or the available bolt area is larger than required by wm1 and/or by wm2. In those cases you will get W higher than wm1 and consequently a "remaining" gasket load higher than Hp. Im talking exactly about those cases.

Ali

 

[marty007]

Are you familiar with Nonmandatory Appendix S? If not, it is worth a read.

 

[BJI]

If you are discussing actual preloads and actual gasket reactions, then you are outside the scope of Appendix 2 calculations. For determining target bolt loads see ASME PCC-1 Appendix O. Otherwise, you are only calculating flange design bolt loads, nothing else, so your flange moment is defined by the seating condition.

 

[aaloui]

Thank you marty007 and BJI for the answers. I got the point.
Ali

 

[aaloui]

I have another question more or less in the same field (gasket and bolted flanges etc..). Since I found your answers convincing, I want to post it again here:

Hi,

does any one have an explication for the expression of HG in 24-3 of Appendix 24, ASME VIII Div. 1?
Actually I don't understand why the term Hp is being subtracted there, I expect only H to be subtracted as the gasket get unloaded
by the force H as the pressure is applied (in analogy to the expression HG in Appendix 2 from the same code).
Does any one know any reference as paper or technical report behind this appendix?

Thank you
Ali

I appreciate your support