The primary purpose of using codes and symbols is to enable the various instrument functions required in a process to be clearly and concisely represented on Process Flow Diagrams (PFD) and on Pipeline and Instrumentation Drawings (P&ID).
The measuring instrument and control device function codes and symbols indicate which process parameter is being measured, the relative locations of the measurement and control devices and the permissible limits applicable to certain variable process conditions.
In cases where supervisory computer systems are installed in a system, special symbols are used to indicate the computer and the instruments, which are connected to it.
For instance, letter codes and symbols permit the following instrument; functions to be graphically represented.
Process Monitoring Instrument Codes
- Flow rate (F)
- Level (L)
- Pressure §
- Quality (Q)
- Speed (S)
- Temperature (T)
These codes are integrated with various symbols to distinguish between indicators, recorders and in certain cases, their geographical locations.