Piping System Design

For any piping numbering and designation, you have to look for the general specification of that project to see the legend used. And that designation system can be differed from one firm to another.

See our system of pipeline designation Piping_Symbols-Dwg.

I think that "PP" stands for power piping which would be ASME B31.1 the other numbers could refer to:

The piping service design specification, drawing number and size of drawing, date, footage, pressure and/or temperature rating or for any number of parameters for the particular job installation. I am pretty sure this would be proprietary numbering system that is generated and used by the designing company for tracking the different piping systems on the job and providing a way to others to find information about the system.