The visual language of equipment symbols is essential for communicating the schematic elements of complicated systems when engineers and designers construct Process and Instrumentation Diagrams (P&ID). Standardized representations of different parts, such as pumps, valves, tanks, and heat exchangers, are provided by P&ID equipment symbols, making it simple for stakeholders to comprehend how materials and energy move through industrial systems. These symbols are essential to the precise design, construction, and operation of plants in process sectors like oil and gas, chemical, electricity, and food processing. Designing a system that is safe, effective, and compliant requires an understanding of P&ID symbols.

In this blog, we’ll explore the frequently used equipment P&ID symbols, while explaining their function, significance, and how they contribute to effective system design.

Equipment P&ID symbols are a set of standardized graphic representations used in engineering drawings to depict physical devices or components in a process system. These symbols are governed by various international standards such as ISA-5.1 (International Society of Automation) or ANSI/ISA-5.1-2009, which ensures uniformity and clarity across industries.

The primary purpose of these symbols is to simplify the communication of design concepts between engineers, operators, and construction teams, while also ensuring that systems are built and maintained according to prescribed specifications.

P&ID symbols can be broadly categorized into several groups based on the function or role of the equipment in the process. These include symbols for:

• Storage Equipment
• Heat Exchangers
• Pumps and Compressors
• Separators and Filters
• Mixers and Agitators
• Conveyors and Transport Equipment

Each group of symbols represents a particular set of operations, with their unique characteristics and purposes that drive the flow of materials, energy, and data within the system.

1. Storage Equipment Symbols:

Storage equipment is fundamental to every industrial process. These devices hold materials, liquids, gases, or chemicals at various stages of the production cycle. Some of the common storage equipment symbols include:

• Tank – General Basin: This symbol represents a general-purpose tank used for the storage of liquids. A tank basin is often used for holding raw materials, intermediate products, or waste streams.
• Tank – Floating Roof: Floating roof tanks are commonly used for storing volatile liquids such as petroleum or chemicals. The symbol depicts a tank with a roof that floats on the liquid, reducing evaporation and maintaining safety.
• Storage – Gas Cylinder: This symbol represents the storage of gases under high pressure, such as hydrogen, oxygen, or nitrogen. Gas cylinders are often used in industrial applications requiring pressurized gas supplies.

2. Heat Exchanger Symbols:

They are essential equipment used for transferring heat between two fluids without mixing them. Further, they play a crucial role in controlling temperatures within various industrial systems. The P&ID symbols for heat exchangers are diverse, as they represent different types based on design and heat transfer method.

• Heat Exchanger – Shell & Tube: It is one of the most used types. This symbol represents the equipment designed to transfer heat between two fluids through a series of tubes enclosed in a shell.
• Heat Exchanger – Plate Type: They feature multiple stacked plates to increase surface area and facilitate efficient heat exchange. The symbol for this equipment shows a series of plates arranged to maximize heat transfer.
• Heat Exchanger – Spiral: They are typically used for handling viscous fluids or fluids prone to fouling. Their design, featuring spirally wound tubes, is depicted by a unique P&ID symbol that differs from other heat exchanger types.

3. Pumps and Compressors:

They are considered as the vital components in fluid handling systems, designed to move or compress liquids and gases. Their symbols are among the most recognized in P&ID drawings.

• Pump: P&ID symbols for pumps represent equipment used to move liquids or slurries from one point to another. Pumps are classified by type—centrifugal, positive displacement, screw, diaphragm, and more—each serving a specific purpose depending on flow and pressure requirements.
• Compressor: They help increase the pressure of gases, making them essential for gas pipelines, HVAC systems, and process industries. The P&ID symbol for compressors typically resembles a mechanical unit with a symbol indicating flow direction.
• Blower: Like compressors but typically operate at lower pressures and higher volumes. They are often used for moving air or gas in industrial processes.

4. Separators and Filters:

Separators and filters are integral to maintaining the purity of liquids or gases within a system by removing unwanted particulates, oil, water, or solids.

• Separator: They help divide different phases into a mixture (e.g., liquid-liquid, liquid-gas, or gas-solid). They are represented by symbols indicating the type of separation (e.g., gravity, centrifugal) or the phase being separated.
• Filter – General: This symbol represents any general-purpose filtration device that removes particulates from liquids or gases. There are more specific filter symbols, including those for activated carbon filters, ion exchange filters, and rotary drum filters.
• Filter – Activated Carbon: Activated carbon filters are specifically used to remove contaminants from fluids, particularly gases. The P&ID symbol for this filter type typically includes a carbon bed or other filtration media to represent the carbon-based filtration process.

5. Mixers and Agitators:

Mixers and agitators are used to combine different materials, typically liquids or solids, in a process stream. The symbol for each piece of equipment can vary depending on the function it serves.

• Agitator: The agitator symbol represents a mechanical device that stirs or mixes materials within a container or vessel. Agitators are often used in reactors, tanks, and mixing vessels.
• Mixer: It represents equipment that combines substances, often using blades, paddles, or other moving parts, to achieve homogeneity in the process.

6. Conveyors and Transport Equipment:

In industrial systems, materials often need to be moved from one point to another. P&ID symbols for conveyors, transport vehicles, and elevators help illustrate how materials are moved through the system.

• Conveyor – Belt: The conveyor belt symbol represents a continuous loop of material used for transporting goods, raw materials, or products across a horizontal or inclined plane.
• Transport – Tank Car: It represents a rail car designed to transport liquids or gases in a tank container. It is widely used in industries such as chemicals, oil & gas, and food processing.
• Transport – Ship: This symbol is used to represent ships or vessels used for transporting bulk materials across water. It is especially relevant in industries where maritime transport plays a significant role, such as shipping and logistics.

Equipment P&ID symbols represent a wide range of industrial devices, each intended to carry out certain functions inside a process system. For instance – conveying system design and operating flows, these symbols are crucial for anything from pumps and compressors to tanks, heat exchangers, and filters. And, given that they stand for equipment that usually depict vital processes including material transportation, energy transmission, separation, and storage. Further, it is imperative to comprehend the meaning behind each symbol. Ensuring the safe and effective design, building, and operation of industrial systems depends critically on the proper use and interpretation of these symbols.

Let’s explore the detailed representation of equipment within P&IDs that we consider;

One of the most important aspects of P&ID equipment symbols is their standardization. The use of standardized symbols across industries and projects ensures that engineers and technicians worldwide can interpret P&ID diagrams correctly, regardless of location or company. This uniformity also helps prevent misinterpretations that could result in system failures or safety issues.

For example, a pump symbol looks the same on a P&ID diagram, whether the project is in the United States, Europe, or Asia. This universality is critical in industries with a global presence, such as oil & gas, where safety, efficiency, and compliance are paramount.

While P&ID diagrams provide a detailed and systematic representation of an industrial system, reading them efficiently requires some practice. Here are a few tips to help you interpret these symbols:

• Familiarize Yourself with the Legend: Each P&ID drawing should have a legend or key that explains the symbols and their meanings. Make sure you are familiar with the legend before diving into the diagram.
• Understand Flow Direction: Arrows on P&ID symbols typically indicate the flow of materials or energy. Pay attention to the direction of the arrows to understand how fluids or gases will move through the system.
• Look for Additional Information: Symbols on P&ID diagrams may include tags or numbers that identify the specific equipment and its function. This information can help you better understand the system’s design.
• Pay Attention to Line Types: Different types of lines (solid, dashed, or dotted) on a P&ID diagram represent various aspects of the system, such as piping, electrical connections, or instrument loops. Understanding these lines is crucial to interpreting the diagram.

To sum up, P&ID equipment symbols are essential for anybody involved in the planning, execution, and upkeep of industrial systems. These standardized symbols provide accuracy, safety, and compliance by assisting engineers in communicating intricate process information in an understandable manner. It is essential to comprehend P&ID symbols whether constructing a new plant, troubleshooting current systems, or examining technical documentation. Effective communication will become increasingly important in process design as industries continue to change. Gaining proficiency with P&ID equipment symbols will increase your ability to support the success of industrial systems in a variety of industries and reinforce the importance that equipment engineering services play in ensuring safe, effective, and compliant operations.

Our specialists can help you accurately design and implement the right symbols for your systems, ensuring compliance and clarity.