The symbols used in piping and Instrumentation diagrams or drawings are many and varied. I have dealt with some of these symbols before but here I have given a comprehensive list of the common P&ID symbols of process equipment such as valves, flowmeters, piping line connections, and much more. Go through them and familiarize yourself with them. However they are by no means exhaustive. Getting to know these common P&ID symbols used in developing instrumentation diagrams will ensure that each time you see a P&ID, no matter how complicated you should be able to identify a symbol or two.
Also know that most piping and instrumentation diagrams will come with their own library of symbols that may be different from the ones listed and pictured here. The first thing you should do with any P&ID is to check the legend section where details of every symbol used on the piping and instrumentation diagram is listed to ensure that you are interpreting the right equipment.
Line Type & Control Signals Symbols Used in P&IDs
Piping Connection Symbols Used in P&IDs
Valve Actuator Types Used in P&IDs:
Valve Failure Modes Symbols Used in P&IDs:
Flow Sensors Symbols Used in P&IDs:
Note that FE is the general symbol for flow sensors in P&IDs. However when we are being specific, then any of the specific symbol for the particular flow sensor/meter can be used
Process Equipment Symbols Used in P&IDs & PFDs (Process Flow Diagrams)
Like I mentioned before every P&ID is unique in its own way. Most of the symbols pictured here, you will see on most P&IDs. However, there could be variations. You must always endeavor to check the legend section of a particular P&ID for any process unit of a plant to get an idea of the library of symbols used to represent various process equipment. This way, there will be no conflict between what you already know and what is being presented
Introduction to AutoCAD Plant 3D 2015
Piping Design Handbook
Piping Systems Manual
The Piping & Instrumentation Diagrams (P&ID) Handbook
Piping Engineering Leadership for Process Plant Projects