INSTRUMENTATION
DRAWINGS & SYMBOLS
This module focuses on understanding the purpose of codes and symbols in engineering, including emergency or safety instrument codes, their structure, tag numbers, abbreviations, function identification codes, and signal modifiers. It covers various drawing and document types, such as process block diagrams, process flow diagrams, piping and instrumentation drawings, electrical loop drawings, DCS I/O loop drawings, and pneumatic loop drawings. The module also covers cause and effect charts, functional logic diagrams, and instrument installation hook-up diagrams. The goal is to equip the learner with a comprehensive understanding of these concepts. The module is designed to help students in their engineering careers.
understanding of the various codes and symbols used to illustrate instrumentation in facilities designed for oil, gas, and hydrocarbon products production. Instrument codes and symbols are graphically represented in technical diagrams such as Process Flow Schemes (PFD) and Pipeline and Instrumentation Drawings (P&ID), which are of particular importance to operation and maintenance technicians who are required to understand the process control systems associated with an installation.
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 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 connected to it. Letter codes and symbols permit the following instrument functions to be graphically represented:
Process Monitoring Instrument Codes: Flow rate (F), Level (L), Pressure (P), Quality (Q), Speed (S), and Temperature (T). These codes are integrated with various symbols to distinguish between indicators, recorders, and in some cases, their geographical locations.
Emergency or Safety Instrument Codes: High level (H), Extreme high level (HH), Low level (L), Extreme low level (LL), Low flow (L), High-pressure (H), High temperature (HH), and High pressure (HH).
In general, every conventional measuring or controlling instrument installed in a process unit is identified by three separate codes: location number code, function letter code, and serial number code. The combination of these codes is known as the Instrument tag number, which has the basic format of "xx a - yyy".
When the instrument code or tag number is written on a drawing or document, a dash is inserted between the 'a' and the 'yyy' sections of the format. For example, a pressure indicating controller installed in a process unit coded 10 and identified by serial number 101 is described in written form as 10 - PIC - 101.