Pressure Equivalent: Peq & compressive axial force?

[tr6]

When evaluating a flange, using the Kellogg Peq method for piping loads, there is no mention on how to handle an axial force that is compressive.

Caesar takes the axial piping load as an absolute value, and uses it in the evaluation formula. This seems to add an additional layer of conservatism to the whole Peq evaluation process.

I have seen pipe stress specs that will not let you take credit for a "compressive" stress. In those cases of a compressive force, the force is not included in the Peq evaluation.

So, if the axial force is compressive:
1.Is the sign of the force to be taken into account and result in being subtracted from the bending force?
2. Taken as the absolute value and added to the bending force?
3. Not taken into account at all resulting in the Peq analysis being based on the bending forces only?

I suppose these questions also apply if a flange is evaluated per ASME VIII, Appendix 2 for piping loads. ???

 

[ione]

It should be taken into account with its sign, thus increasing the gasket load for compressive force.
Note that ASME VIII, Appendix 2 makes reference only to external tensile axial force thus neglecting any compressive effect.

 

[StevenHPerry]

I don't disagree that axial tension has some effect, but bending will have a much greater impact than axial forces in most cases.

Sec 8 Div 1 Appendix 2 doesn't account for external forces and moments unless it's changed in recent years. Scanning the 2010 version, it looks the same to me.

Sec 8 Div 2 does, though!

- Steve Perry

http://www.linkedin.com/in/stevenhperry

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