The category of permanent joints between the items of pressure equipment of an assembly shall be determined individually, taking into account the effect of the joining on the integrity of each of the items to be joined.
For example, the connection of a pipe to a vessel through a nozzle (already connected to the vessel) will, in general, be made according to the category of the pipe, provided that it does not affect the integrity of the vessel.
Note 1:
For assemblies, the directive defines a global conformity assessment procedure and determines the category to be followed for essential safety requirements related to design (as stated in Article 14 paragraph 6 (b), and for the assessment of the protection (as stated in Article 14 paragraph 6 (c). For the other essential safety requirements applicable to the assembly (see PED Guideline C-12), in the absence of specific information in the directive for the category, it should be based on the categories of the items concerned.
Note 2:
This is consistent with PED Guideline B-15, which makes a distinction between the category used for the assessment of the design, and the determination of the category regarding essential safety requirements.
See also PED Guideline C-16 for the category of the global conformity assessment procedure.