From document ADOE-QWI-16 I can see that the unit number is a part of the Equipment tag no and Pipe number. Since the ERU has one common unit no ( 15000 )according to the Basic Engineering Design Data, we need to know the up-stream equipment numbers in order to avoid having identical type of equipment with the same tag no - unless the SNOX plant will obtain a specific unit no.
Regarding equipment numbering in which way do we number parallel equipment in the three lines? E.g. according to the numbering system the Flue gas blower will be numbered K-15001 A/B ( A/B in case of spare blower).- But how do we indicate which of the three lines the blower belongs to