[easy-e]

Pick up this resource:
http://www.pipefitter.com/NAVCO.html

It is the NAVCO Piping Datalog. Mine is pretty old but the info on pp. 17-21 should be the same. I think you are looking for wall thickness calculations and working pressures for pipe. You will find out the formulas for both the ANSI piping code (B31.1) and the ASME Boilder code, section 1. I hope this helps