Introduction to P&ID

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The flow sheet or flow diagram are often used in context of engineering and design application. Although this terminology is not most accurate to describe P&IDs, it’s sufficient to describe the overall family of a process based diagram to which P&IDs belong.

We can divide the process diagram in three type or step:

BFD : The Block Flow Diagram
PFD : The Process Flow Diagram
P&ID : The Process and Instrumentation Diagram

BLOCK FLOW DIAGRAM

The beauty of a BFD is its ability to outline the complete process on little more than a single sheet. The diagram usually resemble an organized chart, containing mainly text enclosed by boxes, interconnecting lines, the process commodities they transport and flow arrows to indicate flow directions.

INFORMATION PROVIDED BY A BFD

A good BFD typically contains the following:

• Individual pieces of equipment or equipment package that are denoted by a single symbol, typically a rectangle.
• Clear label illustrating function
• Lines linking equipment or process to show flow direction.
• The order of process flow arranged and if possible with a gravity bias.
• Whenever more than one line leaves a process then the processed commodity in each line should be clearly marked

TYPICAL BFD

PROCESS FLOW DIAGRAM

Process flow diagram carry more information than the block flow diagram. They show more detail about major equipment & sub system and the flow. PFD include information of the pressure and temperature of the feed and product line to and from all major equipment. Also indicate the main header and points of all control. It’s consider as the precursor of P&IDs

Information provided by a PFD

A typical PFD shows the following items:

• Process piping
• Process flow direction
• Major bypass and recirculation lines.
• Major equipment represented by simplified symbols.
• Control and process critical valves
• System ratings and operational values.
• Composition of fluids
• Connection between systems.

TYPICAL PFD

PROCESS AND INSTRUMENTATION DIAGRAM

The Piping and Instrumentation Diagram (P&ID), based on the Process Flow Diagram (PFD), represents the technical realization of a process by means of graphical symbols for equipment and piping together with graphical symbols for process measurement and control functions.

A P&ID carries a wealth of information that span engineering disciplines to define a process. The representation and designation of all the equipment, instrumentation and piping should comply with the requirements of Standard. Auxiliary systems may be represented by rectangular boxes with reference to the separate diagrams

For processing facilities, it is a pictorial representation of:

Ø Key piping and instrument details

Ø Control and shutdown schemes

Ø Safety and regulatory requirements and

Ø Basic start up and operational information

INFORMATION PROVIDED BY P&ID:

• Permanent start-up and flush lines.
• Flow directions and Interconnections references.
• Control inputs and outputs, interlocks and Computer control system input.
• Interfaces for class changes.
• Identification of components and subsystems delivered by others.
• 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.

TYPICAL P&ID

More about PFD
More about P&ID 

PIPING DAIGRAM SYMBOL

Symbol is the basic notation to describe or represent a P&ID. To read and interpret piping and instrument drawing , the reader must learn the meaning of the symbol. We will discuss about the common symbols that are used to depict fluid process plant.

In general all the symbols used in P&ID are as per ISA or ANSI standard. But any organization may have their own standard which is derived from international standard.

LINE SYMBOL

COMPRESSOR SYMBOL

FUNCTION SYMBOLS

FUNCTION SYMBOLS

PUMP SYMBOLS

STORAGE SYMBOL

FITTINGS SYMBOL

EXCHANGER SYMBOL

Piping Symbols used in P&ID

What Are P&ID Symbols?

P&ID (Piping and Instrumentation Diagram) symbols are standardized graphical representations used to identify process equipment, valves, instruments, pipelines and control systems in industrial process plants.

Engineers, operators, maintenance personnel and project teams rely on these symbols to understand plant operation, troubleshoot process issues and communicate engineering information consistently.

This reference guide explains the most commonly used P&ID valve symbols, instrument symbols, line symbols and valve position indicators found in industrial process plants.

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Common Valve Symbols Used in P&ID

Valves are among the most frequently used components in process plants. Different valve symbols are used to represent manual valves, control valves, isolation valves and specialty valves.

The chart below shows common valve symbols used in P&ID drawings.

Why Valve Symbols Are Important

Valve symbols help engineers quickly identify how process flow is controlled within a plant. Correct interpretation of valve symbols is critical during commissioning, operation, maintenance and troubleshooting activities.

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Valve Position Symbols and Notations

P&ID drawings often indicate whether a valve should normally remain open, normally closed or partially open during plant operation.

These symbols help operators understand the intended operating condition of the process.

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Typical Valve Position Indicators

• Normally Open (NO)
• Normally Closed (NC)
• Locked Open (LO)
• Locked Closed (LC)
• Fail Open (FO)
• Fail Closed (FC)
• Fail in Position (FL)

Valve position notations provide valuable operating information and help ensure that startup, shutdown and emergency procedures are followed correctly.

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Instrument Symbols and Identification Letters

Instrument symbols use standardized identification letters to indicate both the measured variable and the instrument function.

Examples include:

• FIC = Flow Indicating Controller
• PIC = Pressure Indicating Controller
• TIC = Temperature Indicating Controller
• LIC = Level Indicating Controller

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Instrument Tag Structure

Most instrument tags consist of letters representing the measured variable, letters representing the instrument function and a unique tag number.

Examples:

• FT-101 = Flow Transmitter
• PT-201 = Pressure Transmitter
• TIC-301 = Temperature Indicating Controller
• LIC-401 = Level Indicating Controller

Understanding instrument tags allows engineers and operators to identify instrumentation quickly during process monitoring and troubleshooting.

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Line Continuity and Direction Symbols

Line continuity symbols indicate how pipelines continue between drawings or connect to other systems. Direction symbols show process flow and improve drawing readability.

These symbols are commonly used to indicatei>Flow direction

Tie-in points

Battery limit connections

They ensure engineers can track process flow across multiple drawings and understand plant interconnections.

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Difference Between PFD and P&ID Symbols

A Process Flow Diagram (PFD) provides a high-level overview of process flow and major equipment.

A P&ID provides significantly more detail, including valves, instruments, control loops, line numbers, alarms and safety systems.

Because of this additional detail, P&ID symbols are generally more extensive than those found on Process Flow Diagrams.

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Practical Benefits of Understanding P&ID Symbols

• Improves troubleshooting efficiency
• Supports plant commissioning activities
• Enhances process safety understanding
• Simplifies maintenance planning
• Improves communication between engineering disciplines
• Helps interpret operating documentation correctly

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Frequently Asked Questions

What is a P&ID symbol?

A P&ID symbol is a graphical representation of equipment, valves, pipelines, instruments or control functions used in engineering drawings.

Why are standardized P&ID symbols used?

Standardized symbols ensure engineers, operators and maintenance personnel interpret drawings consistently across projects and facilities.

What is a control valve symbol?

A control valve symbol identifies a valve that automatically regulates process variables such as pressure, flow, temperature or level.

What does FIC stand for?

FIC stands for Flow Indicating Controller.

What does PIC stand for?

PIC stands for Pressure Indicating Controller.

What does LIC stand for?

LIC stands for Level Indicating Controller.

What is the purpose of valve position indicators?

Valve position indicators show the intended operating condition of valves, such as normally open, normally closed or fail-safe positions.

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Related Articles

• YOUR_PID_ABBREVIATION_POST_URLP&ID Abbreviations and Instrument Identification
• YOUR_INTRODUCTION_PID_POST_URLIntroduction to P&ID
• YOUR_CONTROL_LOOP_POST_URLUnderstanding Control Loops in P&ID
• YOUR_LINE_NUMBER_POST_URLLine Numbering in P&ID
• YOUR_UTILITY_FLOW_POST_URLUtility Flow Diagram and P&ID

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Conclusion

Understanding P&ID symbols is essential for engineers, operators and maintenance personnel involved in process industries. Valve symbols, instrument symbols and line continuity symbols provide the information required to interpret industrial process systems accurately.

This guide can be used as a quick reference when reviewing engineering drawings, process documentation and plant operating procedures.

P&ID Abbreviations and Instrument Identification: Complete Reference Guide

What Are P&ID Abbreviations?

P&ID (Piping and Instrumentation Diagram) abbreviations are standardized short codes used to identify equipment, pipelines, instruments, utilities and control functions in industrial process plants.

Engineers, operators and maintenance personnel use these abbreviations to quickly understand process flow, equipment function and instrumentation details without lengthy descriptions on engineering drawings.

This guide explains common P&ID abbreviations used for equipment identification, utility services, line designation and instrument tagging with practical examples.

How Are Abbreviations Used in P&ID Drawings?

Equipment Identification

Equipment tags use abbreviations followed by numbers to uniquely identify equipment within a process plant.

• AP-1002 = Pump
• AV-1012 = Vacuum Pump
• ST-2001 = Storage Tank
• AB-3001 = Vessel

Pipeline Identification

Pipeline abbreviations specify the service flowing through the pipeline.

• CWS = Cooling Water Supply
• CWR = Cooling Water Return
• HOS = Hot Oil Supply
• HOR = Hot Oil Return

Instrument Identification

Instrument tags define what variable is measured and what action is performed.

• FIC = Flow Indicating Controller
• PIC = Pressure Indicating Controller
• TIC = Temperature Indicating Controller
• LIC = Level Indicating Controller

Bellow is list of some abbreviation generally used in a standard P&ID:

Drain and Sewer Abbreviations

Miscellaneous P&ID Abbreviations

Utility Service Abbreviations

Utility Service Abbreviations

Instrument Abbreviations and Tag Letters

The abbreviations shown above are commonly used in industrial process plants for equipment identification, utility services and line designation. Individual companies may modify naming conventions based on their internal engineering standards.

Frequently Asked Questions

What does P&ID stand for?

P&ID stands for Piping and Instrumentation Diagram.

What are P&ID abbreviations?

P&ID abbreviations are short codes used to identify equipment, pipelines, utilities and instruments in engineering drawings.

Why are abbreviations used in P&ID?

Abbreviations improve drawing readability and reduce drawing space requirements while maintaining standardization.

What does FIC mean in P&ID?

FIC means Flow Indicating Controller.

Are P&ID abbreviations standardized?

Many organizations follow ISA conventions, although practices differ between companies and projects.

Conclusion

Understanding P&ID abbreviations is essential for interpreting engineering drawings, process systems and industrial plant documentation. Equipment tags, utility abbreviations and instrument identification codes provide a common language that helps engineers and operators understand plant operation quickly and accurately.

Keep this reference as a quick guide whenever reviewing P&ID drawings and related engineering documents.

Understanding P&ID Drawing Sheets: Title Block, Grid System, Revision Block and Legend

More about P&ID

A P&ID sheet can be divided in following parts:

• Title Block (1st block, 2nd block, 3rd block & other information as scale, soft copy reference etc.)
  
  
• Grid System
  
  
• Revision Block
  
  
• Notes and Legend
  
  
• Equipment Specification
  
  
• Drawing (Graphic Portion)
  
  

TITLE BLOCK:

Generally title block consist 3 Area: 1st area contains drawing title, number, location or area, site and vendor. 2nd area contains signature, information of drafting, verification, approval and control. 3rd area is reference area which contains reference block and drawing information.

DIFFERENT AREA OF A TITLE BLOCK SHOWN BELLOW:



BELLOW IS AN EXAMPLE OF A TYPICAL TITLE BLOCK:



GRID SYSTEM:


Because of drawing tend to be large & complex it quite difficult to find a specific point in a sheet. This is especially true when a wire or pipe is continued on a second drawing. To locate the point in reference print most drawing has 2D coordinate grid system. The grid consist letter, number or both that run horizontally and vertically around the drawing.

TYPICAL GRID USED IN P&ID:



REVISION BLOCK:

If any change is done in a system or equipment or specification in drawings the drawing must be redrafted and reissued with a new version of the original drawing.The revision details must be mentioned in Revision Block. The original drawing must be of version 0.



NOTES AND LEGEND:

Because of the importance of understanding all the symbol & convention used in a drawing the notes and legend section must be review before reading a drawing.The legend and note section of a drawing list & explain any special symbol & convention used on the drawing. Any notes required for understanding a drawing can be mentioned here.




EQUIPMENT SPECIFICATION:

In this section the specification of essential equipment can be mentioned.

• A vessel/ tank can be specified with capacity, MOC, Empty weight, jacketing detail, tubing detail etc.
  
  
• A pump can specified with it’s disch. capacity, head, RPM, drive type etc.
  
  
• A motor can be specified with it’s RPM, rating current, voltage, frequency etc.
  
  

DRAWING:

Drawing area is the graphics section where the pictorial view of system/project/equipment is described graphically using standard symbol & procedure.

EXAMPLE OF A STANDARD DRAWING SHEET:




Generally any organization customizes and makes their own standard focusing on ISA standard.