P & ID Diagram: Work out the Drawing for Process Excellence

II JAY SHRI KRISHNA II

Hello friends, as promised, I'm excited to dive into the world of P&ID diagrams. These seemingly complex schematics are the backbone of process industries, providing a visual roadmap for understanding, designing, and optimizing operations.

In this blog post, we'll explore the intricacies of P&ID diagrams, from their basic components to their critical role in ensuring safety, efficiency, and compliance. Let's demystify these diagrams and uncover their invaluable contributions to the industrial landscape.

P & ID Diagram: Work out the Drawing for Process Excellence

P&ID diagrams, or Process and Instrumentation Diagrams, serve as the cornerstone of Process engineering, providing a visual representation of the intricate interplay between equipment, piping, instrumentation, and control systems within a process plant.

Process and Instrumentation Diagram (P & ID)

These diagrams offer a comprehensive overview of the physical layout, functional relationships, and operational logic of a process, enabling engineers, operators, and maintenance personnel to understand, analyze, and optimize the system's performance.

P & Id Diagram is well-defined as follows:

• P & Id diagram is a Process & Instrumentation Diagram giving schematic illustration of functional relationship as envisioned by Process Engineer of Piping, instrumentation and system equipment.

• P & Id Confirm the correct use of symbols for valves, equipment, instrumentation, and control interlocks.

• The P & Id are used to understand the process function and control the process system.

• The primary schematic drawing used for laying out of process control installation.

• A P&ID is a detailed schematic drawing that illustrates the flow of materials, the sequence of equipment, and the instrumentation required to control and monitor a process.

It includes a wide range of components, including pumps, valves, vessels, heat exchangers, piping systems, sensors, controllers, and safety devices. By visually connecting these elements, P&IDs provide a clear and concise representation of the process's functionality, simplifying effective design, operation, and maintenance.

The Piping Engineer's Role in P&ID Development:

• Piping engineers should have a fundamental understanding of the process, but detailed knowledge of reaction schematics, controlled valve, or safety valve sizing is not required. Their primary role is to translate process concepts into reality through detailed engineering.

• To comprehend P&IDs, Piping engineers need to understand flow concepts and instrumentation loops. They can cross-check simple details like safety valve vents, flare heights, and siphon loop heights to ensure that the P&ID aligns with practical considerations and standards.

• Utility equipment placement is crucial, and Piping engineers create utility flow distribution charts based on electrical layout and P&IDs. Therefore, understanding the location of utilities related to the main plant is very important.

• In Process Flow Diagrams, the process department provides line sizes and fluid media/materials. Piping engineers then complete the P&ID line list. A thorough process study helps select appropriate ratings and reduce project costs.

P&ID Components and Their Functions:

For processing services, it is a pictorial representation of Basic start-up and operational information.

• Major equipment details: Represents various processing units like tanks, pumps, and heat exchangers.

• Key piping and instrument details: Signifies the flow path of materials. Shows devices for gauging & controlling process variables (e.g., temperature, pressure, and flow).

• Control and shutdown systems: Illustrates the logic & interconnections between instruments & equipment.

• Safety Devices: Things to see safety features such as alarms, emergency shutdown systems, and fire protection. Safety and regulatory requirements, necessary slopes, vent and drain details etc.

Importance of Standardization:

• Industry-Wide Adoption: P&ID diagrams follow to standardized symbols & conventions, ensuring universal understanding.

• Improved Communication: Regular use of symbols simplifies effective communication among engineers, operators, and maintenance personnel.

Digital Tools and Integration:

• Computer-Aided Design (CAD): Modern P&ID software make simpler creation, modification, and sharing of diagrams.

• Integration with Other Systems: P&IDs can serve as a bridge between process simulation software, control systems, and data management systems, simplifying efficient information flow & decision-making.

Equipment Identification in P&IDs:

Item Number and Identification:

• Assign a unique item number to each piece of equipment.

• Place the item number, within or adjacent to the equipment symbol.

• Additionally, it may be repeated above the equipment for enhanced visibility.

• Use concise and descriptive names that accurately represent the equipment's function.

• Include relevant design information as needed.

For Example, R – 301

Where,

R – Reactor (Represent the Type of Equipment)

Similarly, D – Drum, P – Pump, C – Column etc.

3 – Equipment Located in P & ID No. 3

01 – The Unique Number in P & ID No. 3

Piping Identification in P&IDs:

Line Representation:

• Pipes are represented by lines.

• Use thick lines for main process flow piping and thin lines for other components.

• Pipes are not drawn to scale.

Line Description:

• Use conventional notation to provide a complete description of each line.

• Include line size, identification number, fluid content, material of construction, line class, and insulation/heat tracing requirements (when applicable). For example, 80-HW-101-B1A-IH-65. We will understand about the line description with more details in our upcoming blog.

List of P&ID Items:

1. Instrumentation and Designation:

• Instrument identification and designation

• Instrument types and functions

2. Mechanical Equipment:

• Equipment names, numbers, and overall dimensions

• Values and Identification:

• Valve types, sizes, and identification

• Valve functions and control mechanisms

3. Process Piping:

• Pipe sizes, materials, and identification

• Space symbols for layout and clearance

4. Miscellaneous Items:

• Vents, drains, and special fittings

• Sampling lines, reducers, and special parts

• Permanent start-up and flush lines

5. Flow Direction:

• Indication of flow direction arrows

• Interconnection References:

• References to other systems or diagrams

6. Control Inputs and Outputs:

• Control signals, inputs, and outputs

7. Class Changes:

• Interfaces for changes in material or fluid properties

8. Computer Control System:

• Inputs and outputs - Communication protocols and interfaces to the computer control system

9. Component and Subsystem Identification:

• Identification of components and subsystems provided by external suppliers.

Format of P&IDs:

• Central Section: Equipment, instrumentation, and process piping are displayed in the center.

• Edge Streams: Streams entering or leaving the diagram are shown at the edges with references to other drawings.

• Utility Streams: Utility streams originate from utility headers at the top or bottom or directly at the equipment. References to utility flow diagrams are provided.

• Line Tabulations: Include the last line number and valve number used.

• Special Notes: Provide any special notes or clarifications.

• Revision Details: Changes or modifications made to the P&ID, includes the date of the revision, the person making the change, and a brief description of the modification.

Preparation of P&IDs:

1. Equipment Layout:

• Limit the number of main processing equipment to avoid overcrowding.

• Show relative elevations if relevant.

• Space main equipment evenly across the sheet.

• Add related piping and instrumentation.

2. Symbols:

• Use standard equipment symbols that convey shape and configuration.

3. Scaling:

• Draw to scale to provide a rough idea of size, but avoid strict scaling by others.

4. Orientation and Nozzle Locations:

• Maintain accurate orientations and nozzle locations, reflecting the actual equipment arrangement.

Piping and Instrumentation Symbols Diagrams (P&ID legend):

Symbols are key components of P&IDs. Using international standards ensures universal understanding. The first sheet of a P&ID set is often includes a symbol legend. It serves as a crucial reference for understanding the various components & their working within the diagram.

P & ID Symbol Legend Diagram

Standard Symbol Set:

• A collection of standardized symbols arrangement used for preparing P&IDs.

• Typically, included or placed as the first sheet of the P&ID set.

Symbol Key:

• Provides a reference for the various symbols and acronyms used in the P&ID.

• Includes keys for line identification symbols, pipe line legends, piping system designations, abbreviations, instrumentation and control symbols, valve types, and special piping applications.

Importance of the P&ID legend:

• Ensure consistent understanding: A legend provides a common language, preventing misunderstandings among different stakeholders.

• Improve efficiency: By quickly referencing the legend, engineers, technicians, and operators can save time and avoid errors.

• Facilitate maintenance and troubleshooting: A clear legend aids in identifying components, diagnosing problems, and performing necessary repairs.

• Support regulatory compliance: Legends help ensure that the system adheres to industry standards and regulations.

Signification of P&ID:

P & Id’s contribute a significant role in the maintenance & alteration of the process that is describes. It is critical to determine the physical sequence of equipment and the system as well as how these systems connect during the design stage.

The diagram also makes available basics for the development of system controlled schemes which, permitting for further safety and operational investigation, such as the hazards and operability (HAZOP Study).

Here are some additional benefits of P & Id:

• Maintenance Planning: P&IDs make available a clear visual representation of the process, helping in identifying critical components, possible failure points, and maintenance schedules.

• Troubleshooting: When equipment failures or process issues arise, P&IDs can help to find the root cause by tracing the flow of materials & pinpointing affected components.

• Upgrades and Expansions: P&IDs serve as a foundation for planning and applying process modifications, make sure that new equipment or changes align with the existing system.

The Importance of P & Id’s for Safety Analysis:

• HAZOP Studies: P&IDs are important input for HAZOP (Hazard and Operability) studies, which detect potential hazards and develop mitigation measures.

• Safety Instrumented Systems (SIS): P&IDs help define the logic and interconnections of SIS components, confirming that safety functions are executed correctly.

• Emergency Shutdown Systems (ESD): P&IDs illustrate the flow paths and control elements involved in ESD systems, allowing effective design and testing.

Conclusion:

Understanding the entire P&ID is crucial. While the process wing issues P&IDs, they serve as the foundation for detailed engineering.

P&IDs are essential drawings for easy understanding and designing industrial processes. They provide a visual representation of the flow of fluids, instrumentation, and equipment. By successfully preparing & using P&IDs, engineers can ensure efficient, safe, and compliant operations.

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