ASME Code Case 181

(e) High Purity Fluid Service: a fluid service that requires alternative methods
of fabrication, inspection, examination, and testing not covered elsewhere in
the Code, with the intent to produce a controlled level of cleanness. The term
thus applies to piping systems defined for other purposes as high purity, ultra
high purity, hygienic, or aseptic.
(f) Normal Fluid Service: a fluid service pertaining to most piping covered by
this Code, i.e., not subject to the rules for Category D, Category M, Elevated
Temperature, High Pressure, or High Purity Fluid Service.
Charlie Chong