Can anyone suggest me how the piping material specification is prepared

Hi.
Please be more precise with your question. Can't figure out what you want to know. You should give more details...

Understand that you never "start from scratch" in preparing piping specs. You're typically dealing with existing company standard specs or client specs. Yes, there are normally enough differences between your current project and the standard specs you have on hand, but often only minor modifications, additions, and deletions are required. Still, I'm not sure I've properly addressed your question since you state "piping material spec". Reiterating what Murphy has said, please provide additional information for a better directed comment.
Doug