The acronym “P&ID” is widely understood within the process industries as the name for the
principal document used to define a process – the equipment, piping and all monitoring andcontrol components. The Automation, Systems and Instrumentation Dictionary, 4th edition’s
definition for a Piping and Instrumentation Drawing (P&ID) tells what they do. P&IDs “show
the interconnection ofprocess equipment and the instrumentation used to control the process”.1
Sets of symbols are used to depict mechanical equipment, piping, piping components, valves,
equipment drivers andinstrumentation and controls. These symbols are assembled on the
drawing in a manner that clearly defines the process. The instrumentation and control (I&C)
symbols used in P&IDs are generally based onISA-5.1-1984-(R1992), Instrumentation Symbols
This book will aid in solving the long existing and continuing problem of confusing information
on P&IDs. The fact that there isconfusion can be understood because there really is no universal
standard that specifies what information should be included on a P&ID or even, for that matter,
the meaning of the letters P&ID. You may knowexactly what “P” means, or what “D” means or
what a P&ID contains, but the person in the facility down the road probably doesn’t agree. For
instance, the “P” in P&ID may stand for Piping orProcess. The “I” refers to Instrument or Instrumentation.
The “D” is for Drawing or Diagram. P&IDs may even be called “Flow Diagrams”,
which are not to be confused with Process Flow Diagrams discussed inthe previous chapter.
P&IDs are sometimes called “Flow Sheets”, a term often preceded by the department that initiated
or developed them, like “Engineering”, or “Controls”, or other descriptors. Inthis book, for
simplicity, we will refer to the document by the acronym, P&ID.
There is no universal, national or international, multi-discipline standard that covers the development