Thanks Farhad for that quick reply,
Definitely your method is simple and cost effective way of doing things. But for large projects with large number of stress critical lines, converting the weightless rigids, and giving input of pressure/temperature/fluid densitiy etc... and making the model useful is time consuming. Due to some mistakes debugging the errors is also time consuming. All this may finally results in the same effort as modelling from the scratch.
The use of PSI eliminates all these problems, and further we have seamless data transfer from PDMS to C-II and back. Hence the output data of C-II gets fed into PDMS thereby, helping the designer for support design and to check for clashes during expansion /occasional and other cases.
Finally everything runs around the cost. For small projects the method suggested by you may be appropriate and for large projects we may require a special interface.
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Piping Stress Analyst