What is the purpose of the 75% requirement given in ASME Code Section I, PG-68.2? What is the potential risk if this ratio is not met? We have a number of steam generation systems associated with our ethylene cracking furnaces. They were designed in 1998-1999, and include both Sect. I and Sect. VIII components. The licensor claims that the PG-68.2 requirement does not apply to them. Can anyone shed any light on this situation for us? A sketch is attached.