text: what's the diff...working pressure and rated pressure? this in relation to pressurized pipe. many people use working pressure and operating pressure interchangeably. however, i don't believe the ansi piping codes use the word rated pressure for piping systems. i believe it uses the term design pressure to define the maximum safe pressure at which a system can be operated.   the only place i can recall the code using the term rated or rating is with regards piping classes or flange ratings. it has been over ten years since i have had reason to look at the ansi code but i believe i am correct.   the main point i would like to make is you need to be very careful what terms you use so that they are consistent with the codes you are using.