All pipes are represented in Piping and Instrumentation Diagrams (P&IDs) by lines, with an alphanumeric coding that allows identifying them for subsequent design (routing, thermal stress analysis, supporting, etc.) and purchase.
There are no rules to stablish universal coding; they depend on each project. Although they include basically the same information, the way they are represented differs. As an example, it is shown a typical line numbering with its characteristic information:
- AA: nominal diameter, in inches(“) if ANSI rules apply or millimetres if we talk about EN-ISO. This diameter is not necessarily coincident with the pipe external or internal diameter, which will depend on the schedule, material type and rating (e.g.: 4 inches)
- BB: fluid code, to distinguish the service for which the pipe is used for (e.g.: fuel gas)
- CC: Unit number, since several Plants may exist in the same industrial complex (e.g.: Unit number 03).
- DDDD: line number. They are assigned sequentially (e.g.: 0035).
- EEEE: pipe class. It collects characteristics such as material type, rating, flange type and corrosion allowance (e.g.: carbon steel, 150#, FF flanges, C.A. 1.6 mm).
- FF: insulation code, due to different requirements such as heat or cold conservation, tracing, jacketing, personal protection, etc. (e.g.: heat conservation).
If you want to know more: