I am working on the stress analysis of a hull piping system for a SPAR in the GOM. The elevation difference of the topside piping and riser porch is 630 ft. We have to consider internal hydrostatic pressure in the pipe. Does CAESAR II automatically include calculating the internal hydrostic pressure if I specify the design pressure at a reference elevation in spreadsheets?

In addition, Does CAESAR II automatically exclude buoyancy effect when performing modal analysis for a submerged piping system?

1) No, the pressure you specify (and see shown on the spreadsheet) is the internal pressure - no adjustments are made.

2) Buoyancy is not considered in the modal analysis.

Thank you, Richard.

1). I should use internal pressure at design water level (DWL) to be conservative because the density of product is lower than that of seawater.

2). Only added mass shall be included to adjust mass in the modal analysis.

Am I right? Richard.

Best regards,

1) Ok. As stated above CAESAR II does not adjust the internal pressure. If you're running one of the offshore Dodes, CAESAR II does take the difference between internal and external pressure for the hoop stress computation (as specified in the Codes).

2) No - a modal analysis is the free undamped vibration of the system. The CAESAR II modal analysis isn't aware that you may submerge the pipe at a later time.