Under U-1 Scope, piping and piping components are excluded from definition of pressure vessel. I am trying to find precedent for how to define small polishing filters (3-4' high) used in a manufacturing process. There are arguments on both sides that they are covered pressure vessels or are excluded piping component.

Of course these items are not in the scope when the diameter is less than 6 inch, however, filters aren´t piping. Nevertheless the filters can be stamped when they satisfy all of the VIII-1 requirements.
Michael