Valve Symbol Guide

Identifying valve types in industrial piping and instrumentation diagrams (P&IDs) is essential for engineers, technicians, and maintenance personnel. This guide will help you quickly recognize common valve types using standard symbols.

Common Valve Symbols and How to Identify Them

1. Gate Valve

• Identification: Rectangle with a horizontal line or wedge inside

• Key Features:

  • Used for on/off control (not for throttling)

  • Provides minimal flow restriction when fully open

2. Globe Valve

• Identification: Circle with a horizontal line through the center

• Key Features:

  • Designed for flow regulation (throttling)

  • Creates higher pressure drop than gate valves

3. Ball Valve

• Identification: Circle with a perpendicular line or smaller circle inside

• Key Features:

  • Provides quick shut-off capability

  • Quarter-turn operation (90° rotation)

4. Butterfly Valve

• Identification: Circle with a diagonal line through it

• Key Features:

  • Used in large-diameter pipes

  • Compact design with quick operation

5. Check Valve

• Identification: Arrow indicating flow direction with perpendicular line

• Key Features:

  • Allows flow in one direction only

  • Prevents backflow automatically

Valve States and Actuators

Understanding valve states and actuators helps interpret their operation:

• Normally Open (NO): Valve is open when not actuated

• Normally Closed (NC): Valve is closed when not actuated

• Bistable: Maintains position during power loss

Common actuator symbols:

Valve States

Actuator Symbols

Advanced Identification Tips

1. Check the legend: Always refer to the diagram's legend for symbol clarification

2. Follow the flow: Arrow indicators show flow direction

3. Note actuator type: This determines how the valve is operated

4. Look for position indicators: Letters "NO" or "NC" indicate normal state

Summary

Mastering valve symbol recognition in industrial diagrams involves:

1. Learning the basic shapes for common valve types

2. Understanding valve states (NO, NC, bistable)

3. Recognizing actuator symbols

4. Consulting the diagram legend when unsure

This knowledge enables engineers to quickly interpret piping systems, enhancing safety, operational efficiency, and maintenance procedures. Standardized symbols enable consistent communication in the global engineering community.