What is a P&ID – Beginner's Guide

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What is P&ID?

Abbreviated as P&ID, a piping and instrumentation diagram is an articulate drawing of a processing plan that entails the piping and process equipment with its instrumentation and control machinery. It displays the piping and associated parts of a physical process flow. Such diagrams are famous in the engineering field.

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.

what is pid

Image Source: gstatic.com

 

Why do we use P&ID?

To maintain and modify a process effectively, you need a P&ID graphical representation. It provides the foundation for the development of system control blueprints, such as Hazard and Operability Study (HAZOS), during the design stage.

Furthermore, P&ID is crucial in facilitating the designing of:

  • Schemes for control and shutdown
  • Requirements for safety and regulation
  • Sequences for start-up
  • Operational details and understanding

 

When to use the piping and instrumentation diagram?

Piping and instrumentation diagrams are a systematic demonstration of the vital connection of piping, instrumentation, and system equipment parts utilized in the instrumentation and control/automation section in engineering. They are handy in developing a manufacturing process for a physical plant.

P&ID maps out complex mechanical and chemical steps required by such facilities. Thus, it creates a plant besides maintaining plant safety as a reference for Process Safety Information (PSI) in Process Safety Management (PSM). In the case of a mishap, the first place to be reviewed is the P&ID.

This kind of paperwork is very precious, whether it is being used to modernize an existing process, change a piece of machinery, or direct the modeling and execution of a new project. Such records enhance safe and effective planning of adjustments using the Management of Change (MOC).

Field technicians, engineers, and operators use these diagrams to get a clear picture of plant processes and how the instrumentation gets interjoined. P&IDs are also suitable for training newbies and contractors.

Although P&IDs play an essential part in engineering processes by showing interconnectivity between instrumentation, they don’t provide specifications. Instead, specifications are in different documentation. However, P&IDs are amazingly handy in a myriad of ways, including:

  • Analyzing construction processes
  • A platform for control programming
  • Developing principles and regulations for facility operations
  • Providing a paper trail of how should the process run
  • Creating a common ground for discussing plant operations
  • Promoting and facilitating terms for safety and management
  • Drawing up a budget for the equipment and pipe design

 

P&ID VS. Process Flow Diagram (PFD)

The details in piping and instrumentation diagrams are directly proportional to how intricate the design is. A PFD is a simple display of the model, basically a skeleton of the process.

pid vs pfd

Similarities

  • They are chemical/process drawings used in the engineering field;
  • They provide sufficient details required during the various chemical/process stages;
  • Arrows indicate the flow of material, and symbols represent equipment in both.

 

What is a P&ID included?

There is no ideal standard concerning the structure of P&IDs per se. A group of process industry owners and engineering construction contractors in the industry laid out many must-haves in a piping and instrumentation diagram in PIC001: Piping and Instrumentation Diagram Documentation Criteria. Below is what a P&ID should entail:

  • Mechanical machinery named and listed numerically
  • All valves and their identifications
  • Process piping, sizes and identification
  • Vents, drain, special fittings, sampling lines, reducers, increasers and swagger under miscellaneous items
  • Permanent start-up, flush edges and flow directions
  • Interconnections reference, control inputs, and output interlock
  • Seismic category and annunciation inputs
  • Computer control system input
  • Vendor and contractor interfaces
  • Identifications for outsourced components and subsystems
  • The estimated physical sequence of the equipment and its rating or capability.

Basic Symbols of P&ID

Like all other professional diagrams, P&IDs has standard shapes and symbols. Based on the industry and manufacturer, there is a wide variety of symbols. Let us look at some of the most famous symbols suitable for smooth functioning across the industry.

A. Equipment Symbols

Equipment in P&ID entails different units that don’t fit into other groups. These include hardware such as compressors, conveyors, motors, turbines, vacuums, and related mechanical tools.

Equipment symbols

Image Source: lucidchart.com

B. Piping Symbols

A pipe is a tubular vessel for transporting liquid or gaseous substances made from plastic or metal. In this section, there are one-to-many pipes, multi-line pipes, separators, etc.

Piping symbols

Image Source: lucidchart.com

C. Vessel Symbols

A vessel is a storage container for fluids. Vessels are known to change the characteristics of the fluid contained in them. These are tankers, columns, cylinders, bags, etc.

Vessel symbols

Image Source: lucidchart.com

D. Heat Exchanger Symbols

A tool modeled to sufficiently transfer heat from different regions or mediums is known as a heat exchanger. Such devices are boilers, condensers, etc.

Heat exchanger symbols

Image Source: lucidchart.com

E. Pump Symbols

To move fluids in and out of other objects, you need a pump. It uses suction or pressure to raise, compress, or move the fluid. This section consists of pumps and fans.

Pump symbols

Image Source: lucidchart.com

F. Instrument Symbols

An instrument is a tool for measuring or controlling quantities like temperature, flow, angle, pressure, etc. In a P&ID, they include indicators, transmitters, recorders, controllers as well as elements.

Instrument symbols

Image Source: lucidchart.com

G. Valve Symbols

Like the valves in our hearts, they are designed to regulate, direct, or control the flow of a fluid through closing, opening, or slightly blocking passageways in piping set up. In this category, there are rotameters, orifices, and other kinds of valves.

Valve symbols

Image Source: lucidchart.com

Those are the most basic and vital symbols and shapes in P&IDs. For more image and SVG files, you can import them and create a personalized P&ID library.

 

Piping and Instrumentation Diagram Examples

P&ID Flow System Illustration

In the diagram below, a fluid flow system, demonstrated is the mechanical and model entities put in one place. It shows the relationship between the processes. The start is the Feed process and the arrows represent the subsequent step/stage of the chemical process. The end is the arrow marked 38gpm to Process. It is a simple diagram, as shown below.

P&ID flow system illustration

Image Source: lucidchart.com

P&ID Separator Vessel Illustration

Below is a drawing of separator vessels in three phases. The components are commonly used to separate various fluids that flow from oil wells in the oil and gas industry. From the diagram, you can see the 3-phase inlet that branches to vapor outlet, water outlet, and oil outlet. In between are the separation processes to get the water, vapor, and oil extracted.

P&ID separator vessel illustration

Image Source: lucidchart.com

 

How to create a P&ID Effortlessly with Edraw?

Now that you know what a piping and instrumentation diagram is, how and when to use, its fundamental symbols, shapes to consider and illustrations, it is time we showed you how to make one using Edraw.

But first, you have to prepare.

Here is how:

Templates

  1. Find the Process and Instrumentation Template in Edraw and double click on the template from Engineering Category;
  2. You will see the drawing page where you find symbols and user-friendly tools for piping and instrumentation diagrams. It is advisable to get started with that very template.
  3. Limitations of P&ID - Throughout the article, you learned how efficient and handy a P&ID is. However, it has some shortcomings, as below:
  • You cannot depend on the diagrams to get the real picture of the output as they are not drawn to scale or geometry accuracy.
  • There is a lack of uniformity in the diagrams since there are no generally agreed-on universal standards for the symbols and shapes used to draw them.
  • Poor color schemes. In P&IDs, colors are not used effectively to explain a process. Thus trying to decipher the meaning of the color used in the layout can be confusing and misleading.
  • Vaguely defined since the documentation is a different entity and separate from the diagram. The nitty-gritty details of the process are in the vendor specifications or datasheets.
  • They require a lot of time and concentration to create.
available templates

 

Symbols

Familiarize with the huge collection of symbols and tools in the software library. They are neatly organized into categories as listed above. There are over 500 vector P&ID symbols created from various international standards.

 

Steps of drawing a P&ID with Edraw Max online:

You can go to P&ID symbol page to have a clear insight into the symbols.

Step 1:  Once you sign up, go to the File menu. Then, tap on New, Engineering, and double-click on Process and Instrumentation template. This will open a fresh drawing page.

step 1

 

Step 2:  Now, go to the Library tab on the left side of the interface. From Equipment, drag equipment shape onto the drawing page.

step 2

 

Step 3:  Next, use the pipelines to join the equipment. To create a connection point, use the Connection Point Tool under the Home tab, to set the pipeline style, go to the Home tab, and tap on the Line button.

step 3

Step 4:  You can add valves and instruments in a similar manner.

Step 5:  To rotate a shape, use the rotation icon when selected.

Step 6:  Change the position of a shape, by dragging it to the required position.

Step 7:  Lastly, add data to a component, double-click on it.

When it's done, you can:

Print the diagram from the Print options in the File menu or export the diagram in several formats from the Export and Send for Export options on the File menu.

 

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