text: 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. \n\nThe 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. \n\nThe 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.