What is a P&ID ?

P&ID or Piping and Instrumentation Diagram is a crucial knowledge in the Oil and Gas industry! Here is why…

P&ID in short, is a schematic illustration of a functional relationship between piping, instrumentation and system components in other words, the P&ID shows the piping and related components of a physical process flow. It’s most commonly used in the engineering field. When it comes to the Oil and Gas industry you will see P&ID’s in refineries, chemical plants, production facilities offshore and much more.

Take a sneak peek at our Introduction to P&ID course with this free lessons on P&ID Symbols. If interested in learning all about P&ID’s, enroll in the training course here: Introduction to P&ID’s Online Course.

Learn the Basics of P&IDs: what is a P&ID, purpose of P&ID’s, types of P&ID’s, prints, symbols, Instructions to download material, The key, Pipe designations, Piping lines and signals, Instruments, Valves, Flowpath.

Limited time promotion for this course. Use coupon PID15 during checkout to take 15% OFF already discounted price! (Limited time and Limited quantity available).

This is a P&ID or Piping and Instrumentation Diagram 

what is P&ID

If you are searching about what P&ID’s are, it is a detailed schematic diagram that illustrates the interconnection of process equipment and the instrumentation used to control the process. P&IDs are commonly used in the process industry, such as in chemical plants, petrochemical plants, and power plants, to show how the different pieces of equipment and instrumentation work together to produce a product or perform a process.

P&IDs typically include symbols for process equipment, such as pumps, valves, and vessels, as well as symbols for the instruments used to measure and control process variables such as flow, pressure, temperature, and level. The diagram also includes information on process and utility piping, as well as the types of fittings and connections used to join them.

P&IDs are critical in safety, designing, constructing, and operating process plants as they provide a clear understanding of the process and help engineers and operators to identify potential problems and safety hazards.

  1. Safety: P&IDs are critical for identifying potential safety hazards in process plants. By understanding the symbols and information on a P&ID, engineers and operators can identify potential issues that could lead to accidents or other safety incidents.

  2. Design and Construction: P&IDs are essential for designing and constructing process plants. They help engineers and designers to understand how different pieces of equipment and instrumentation should be interconnected, and they provide critical information on piping and fittings.

  3. Operation and Maintenance: P&IDs are also important for operating and maintaining process plants. They provide a detailed understanding of the process, which helps operators to optimize plant performance and troubleshoot issues that arise during operation.

  4. Communication: P&IDs are a universal language in the process industry. By understanding P&IDs, engineers, operators, and other stakeholders can effectively communicate about the process and equipment, regardless of their native language or background.


The piping and instrumentation diagram has a close relation to the process flow diagram (PFD) that explains a rather typical flow of plant processes concerning major equipment of a plant facility.

P&ID’s are used in order to maintain or modify a process effectively. It also aids in the design of schemes for control and shutdown, requirements for safety and regulation, operational details and understanding, sequences for start-up.

P&ID’s are usually created by the engineers in charge of designing the facilities that require complex chemical or mechanical processes that are mapped out with P&ID’s. Then other engineers such as field techs, engineers and operators use them to better understand the process, maintain the facility and to ensure that the instrumentation is what is it’s supposed to be by design when it comes to the management of change for example. The P&ID’s are also a great tool for training and onboarding of new team members. 

In order to be able to understand P&ID’s, engineers must learn the many P&ID’s symbols that make up the diagram. A great start to learn about P&ID’s and P&ID symbols is this video course available right here on Petrolessons: INTRODUCTION TO P&IDs.

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