P&ID Symbols
19
CHAPTER TWO
P&IDs and Symbols
Overview
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 and control 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 of process 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 and instrumentation 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 on ISA-5.1-1984-(R1992), Instrumentation Symbols and Identification.2
This book will aid in solving the long existing and continuing problem of confusing information on P&IDs. The fact that there is confusion 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 know exactly 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 or Process. 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 in the 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. In this 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
CHAPTER TWO
P&IDs and Symbols
Overview
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 and control 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 of process 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 and instrumentation 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 on ISA-5.1-1984-(R1992), Instrumentation Symbols and Identification.2
This book will aid in solving the long existing and continuing problem of confusing information on P&IDs. The fact that there is confusion 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 know exactly 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 or Process. 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 in the 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. In this 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