Now a days Metallic pipes are being replaced by the plastic pipes due to corrosion resistance .......... Is there not any advantage of metallic pipe over plastic pipes ........ will eventually all piping will be converted to plastic piping............?

Simple material density will suggest this will never happen.
If in doubt, build it stout.

Its a good job Sch40 pipe is stout TBH...

Plastic pipes have limited temperature ratings. Plastic will melt. Typically metals are much stronger than plastics.

ASME hosted a four day get-together earlier this month - Use of HDPE for Power Plant Piping Systems Workshop. It was co-sponsored (?) by Electric Power Research Institute and the Plastic Pipe Institute.

misplay

I want to know how can I launch the batch run (for static analysis) from an external interface like VBA/Batch? and How i can i convert a neutral file cii in caesar file .CAESAR II?

cdoffshore - this should be in a different "thread", this one is discussing plastic vs metallic pipe.

CAESAR II was not setup to run in batch mode. However, if you have a number of jobs that:
a) have passed error checking and
b) have load cases defined (or you're ok with the default cases)

you can use the "Batch Stream Processor" (under the \tools) menu to analyze a list of job files.

To convert a CII file into an input file, use "\tools\external interfaces\CAESAR II Neutral File".