Basic Knowledge about Piping and Instrumentation Diagram
The piping and instrumentation diagram (P&ID) is mostly used in the engineering field. It also plays a crucial role in the design, maintenance, and change of the manufacturing process that it represents. The P&IDs are usually made by engineers who need to design, plan and construct a physical process for a plant.
Differences Between PFD and P&ID
Instrumentation details vary with the degrees of design complexity. For example, simplified or conceptual designs, often called process flow diagrams (PFDs), which provide fewer details than fully-developed piping and instrumentation diagrams (P&IDs). Therefore, a PFD is used only to understand how the process works.
Knowledge About P&ID Symbols
To better understand the process and instrumentation diagram, you need to get familiar with the P&ID symbols used in the piping and instrumentation diagram.
The combinations of letter and number appear inside each graphical element and letter combinations are defined by the ISA standard. Numbers are assigned by users so that the schemes vary in different situations. Some companies use sequential numbering, some will tie the instrument numbers to the process line numbers, and others adopt unique and sometimes unusual numbering systems.
The first letter defines the measured or initiating variables such as Analysis (A), Flow (F), Temperature (T), etc. with succeeding letters defining readout, passive, or output functions such as Indicator (I), Recorder (R), Transmitter (T), etc.
Below are some piping and instrumentation symbols with letters. All the standard P&ID symbols can be found in Edraw Max, which is a powerful and easy-to-use P&ID maker for professionals and beginners.
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What Should a P&ID Include and NOT Include?
The P&ID is a very common term used in the world of process industries. A process engineer in a manufacturing plant needs to create new and/or modify the already existing P&ID to the as-is plant modifications. All the chemical engineering and related engineering students have also learned about it or at least heard. A P&ID is a detailed graphical representation of a process including the hardware and software (e.g., piping, equipment, instrumentation) necessary to design, construct, and operate the facility. As defined in the PIC001: Piping and Instrumentation Diagram Documentation Criteria by Process Industry Practice (PIP) - a consortium of process industry owners and engineering construction contractors who serve the industry.
A P&ID Should Include:
- Instrumentation and designations;
- Mechanical equipment with names and numbers;
- All valves and their identifications;
- Process piping, sizes and identification;
- Miscellaneous - vents, drains, special fittings, sampling lines, reducers, increasers and swagers;
- Permanent start-up and flush lines;
- Flow directions;
- Interconnections references;
- Control inputs and outputs, interlocks;
- Seismic category;
- Interfaces for class changes;
- Quality level;
- Annunciation inputs;
- Computer control system input;
- Vendor and contractor interfaces;
- Identification of components and subsystems delivered by others;
- Intended physical sequence of the equipment;
- Equipment rating or capacity.
A P&ID Should NOT Include:
- Instrument root valves;
- Control relays;
- Manual switches;
- Primary instrument tubing and valves;
- Pressure temperature and flow data;
- Elbow, tees and similar standard fittings;
- Extensive explanatory notes.
Learn how to create a piping and instrumentation diagram here. Besides, you can look at the video below and know how to make a P&ID with professional software in minutes!
Here is a P&ID template for showing the water boiling process and you can customize and remodel it in Edraw Max.
If you want to build a process control system, this template may give you some ideas and get you inspired.