Let me clarify, I agree with the sentiment expressed by the staff engineer in that the rerate should occur to the standard of the construction day.
I agree that if you are to rerate to the current standard, then the whole suite of concurrent standards and practices need to apply.
metengr said:
There is a current interpretation by the NBIC on this very issue - original does NOT mean original edition and addenda.
Metengr, perhaps you should link to the interpretation and dispell any doubts.
One way to get around the rerating complexities for smaller diameter systems, is to design, flexi and construct your piping systems to the DP and DT, however conduct a cold and new hydro to the limit imposed by flange ratings (- be sure to do stress check calcs for high flange ratings). The flange rating, afterall, sets the ultimate envelope for a piping system. If you test your system to the maximum possible envelope - then any future rerates end up being a paper shuffling exercise (providing the line condition today is comparable to the hydro then) since original hydro is above or equal to the hydro required by the new DP.
Anyone like to proffer a comment regarding the hypothetical original hydro vs new pneumatic. I frankly don't have a definitive answer.
- - - - - - - - - - - - - - -
"Life! No one get's out of it alive."
"The trick is to grow up without growing old..."