Hi Moorthy,
First of all, have your firm get a decision in writing from the owner regarding the Code you are to use.
The B31.4 and B31.8 Codes are intended for cross-country transportation of fluids and typically this implies buried piping. The B31.11 Code is intended for slurry piping and this is not what you have. If the majority of the piping at issue will not be buried, and if it is not refrigeration piping (B31.5) and it is not power piping (B31.1)and it is not building piping (B31.9)then all you are left with is B31.3 Process Piping. That is a Code that has a broad applicability and includes rules that are easily adapted to the systems that you want to evaluate. Have a look at the Scope paragraphs of these Codes to get a better feel for what each is intended to be applied to.
Regards, John.
_________________________
John Breen