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What is a Piping and Instrumentation Diagram (P&ID)?

By December 20, 2023No Comments3 min read

There are a number of different types of engineering drawings, a P&ID being one of them. A P&ID, or piping and instrumentation diagram, is a schematic illustration of piping and related components showing how they are interconnected and indicating the flow of materials and the control of the process. This is the principal drawing used for laying out a process control system’s installation. P&IDs are most commonly used in the engineering field. Engineers use P&IDs to plan and design the process system, ensuring that it meets specifications and safety standards.

Key Components Typically Found within a P&ID: 

There are two standards typically used that highlight the way they should be drawn, ANSI/ISA S5.1-2022 “Instrumentation Symbols and Identification” and PIP PIC001 “Piping and Instrumentation Diagram Documentation Criteria” The following are typically found in a P&ID:

  • All Process and utility piping with their sizes, material specifications, and identification
  • All major and minor equipment with their names and tag numbers
  • All valves (Manual, Automatic, Safety Relief, etc.) and corresponding identifications
  • Instrumentation (Pressure, Temperature, Flow, etc.)
  • Control Loops and Interlocks

What is a P&ID used for? 

These illustrations are most often created by engineers who are designing a process for a physical plant. P&IDs are utilized by field techs, engineers, and operators to understand the process and how the instrumentation is interconnected.

Common uses include:

  • Planning and designing the entire process system, while ensuring that it meets specifications and safety standards
  • Communication among different engineering disciplines, as well as between design teams, operators, and other stakeholders involved in the project
  • Guiding the installation of equipment and piping systems during construction
  • Training new employees to understand the layout and functioning of the process system
  • Safety Reviews such as OSHA 1910.119 Process Hazard Analysis (PHA)
  • Operation and maintenance

P&ID Symbols 

P&ID drawings have a set of standard symbols that are used to represent the different components in the diagrams. These instrumentation symbols can be found withing the two main P&ID codes and are key to being able to understand P&IDS. The basic symbols include piping, instruments, valves and equipment such as vessels, heat exchangers, pumps. Depending on the line shown in the diagram it could represent the flow of fluids through pipes or electrical signals.