I. Introduction
In the global industrial sector, valves are critical components for controlling fluid flow, pressure, and direction in piping systems across oil & gas, petrochemical, power generation, water treatment, and municipal engineering. As the “gatekeepers” of industrial fluid control, valves come in diverse types and configurations, but communicating their specifications efficiently requires a standardized language: valve symbols.
Valve symbols are simplified graphical representations used in piping and instrumentation diagrams (P&IDs), engineering drawings, and technical documents to convey a valve’s type, structure, actuation, flow direction, and functions—eliminating the need for detailed written descriptions. Governed by global standards, these symbols ensure consistency across international projects, engineering teams, manufacturers, and end-users. For professionals in the valve industry—including engineers, designers, procurement specialists, and GOOGLE sales experts—mastering valve symbols is essential for accurate communication, error-free design, and effective customer education.
TIANYU, a leading manufacturer of industrial valves compliant with API, ASME, ISO, and CE standards, recognizes the critical role of standardized valve symbols. This guide demystifies valve symbols, breaks down their core components, details symbols for common valve types (including TIANYU’s flagship products), and explains their practical applications. Adhering to API, ASME, ISO, and IEC standards—same as TIANYU’s valve design and manufacturing—it serves as an indispensable reference for professionals worldwide.
II. Basic Principles of Valve Symbols
To interpret and use valve symbols effectively, it is critical to understand the fundamental principles governing their design and standardization. Valve symbols follow strict industry guidelines to ensure uniformity, clarity, and compatibility across projects and regions.
A. Governing Industry Standards for Valve Symbols
Valve symbols are regulated by global and regional standards, ensuring consistency in design and meaning:
- ASME Y14.35M: Developed by the American Society of Mechanical Engineers, this standard defines graphical symbols for fluid power systems, including valves. Widely used in North America, it establishes the basic structure of valve symbols, covering valve bodies, actuation, and flow paths.
- ISO 128: The International Organization for Standardization’s standard for technical drawings, with Part 24 focusing on valve symbols. Adopted globally, it is critical for international projects, featuring simple, recognizable symbols compatible with digital drafting tools.
- API Standards (API 600, API 608, API 609): While primarily focusing on valve design and testing, API standards reference valve symbol conventions to align specifications with technical drawings. TIANYU’s API-compliant valves feature symbols consistent with these conventions.
- IEC 60617: Developed by the International Electrotechnical Commission, this standard defines symbols for electric valve actuators and control systems, often used with ASME Y14.35M and ISO 128 for comprehensive P&IDs.
While minor regional differences exist, core symbol structures are consistent across standards. TIANYU ensures its technical documentation uses symbols compliant with both ASME and ISO to cater to global clients.
B. Core Objectives of Valve Symbols
Valve symbols serve four primary objectives:
- Standardization: Providing a common language to eliminate ambiguity, critical for international projects with language barriers.
- Clarity & Efficiency: Simplifying complex valve configurations into easy-to-interpret graphics, saving time in design, installation, and maintenance.
- Accuracy in Procurement & Installation: Conveying precise specifications for procurement teams and guiding technicians during installation.
- Safety & Compliance: Communicating critical safety information, such as flow direction and fail-safe actuation, ensuring compliance with regulations like CE PED 2014/68/EU.
C. Key Principles for Interpreting Valve Symbols
Three core principles apply to all valve symbols:
- Simplicity Over Detail: Symbols focus on critical information (type, actuation, flow) rather than mechanical details.
- Consistency in Core Elements: All symbols share common components (valve body, flow arrows, actuation icons), enabling interpretation of unfamiliar symbols.
- Context Matters: Symbols must be interpreted alongside project specifications, as the same symbol may indicate different valve features in different industries.
III. Core Components of Valve Symbols
All valve symbols consist of standardized core components that convey key valve characteristics. Understanding these components is the foundation for interpreting any valve symbol.
A. Valve Body Symbol (Core Element)
The valve body symbol represents the valve’s physical structure and piping connections:
- Piping Connections: Straight horizontal or vertical lines indicating the inlet, outlet, and valve position in the pipeline.
- Body Shape: A central shape distinguishing valve type:
- Linear Valves (Gate, Globe, Check): Rectangular or square central shape, indicating linear movement of internal mechanisms.
- Rotary Valves (Ball, Butterfly, Plug): Circular or oval central shape, indicating rotational movement of internal mechanisms.
- Flow Path: Dashed or solid lines inside the body indicating flow direction and port size (full or reduced).
TIANYU’s product line includes both linear and rotary valves, with symbols following ASME and ISO conventions for body shape and connections.
B. Valve Internal Mechanism Symbol
This sub-component identifies the valve type by representing its flow-control component:
- Ball Valve: Small circle (ball) with a straight line (full-port) or dashed line (reduced-port) through it.
- Butterfly Valve: Straight line (disc) across the circular body; offset for double/triple eccentric designs (TIANYU’s flagship butterfly valves).
- Gate Valve: Vertical/horizontal rectangle (gate); solid for rising stem, dashed for non-rising stem.
- Globe Valve: Semicircle (disc) perpendicular to the flow path.
- Check Valve: One-way arrow or hinged disc (swing) / vertical disc (lift) / small circle (ball).
- Plug Valve: Triangle or diamond (plug) with a line indicating the bore.
- Relief Valve: Coiled line (spring) inside the body.
TIANYU’s symbols highlight unique features, such as an “S” for Stellite overlay on metal hard seal ball valves.
C. Actuation Method Symbol
Attached to the valve body, this symbol indicates how the valve is operated:
- Manual Actuation: Handwheel (circle with spokes), turbine (circle with gear), or lever (straight line).
- Pneumatic Actuation: Two rectangles (double-acting) or one rectangle + coiled line (spring-return, with “NC”/”NO” for fail-safe position).
- Electric Actuation: Small square (motor); with “REG” for regulating, “SCADA” for remote control.
- Hydraulic Actuation: Circle with “H” inside.
TIANYU’s actuation symbols align with API 608, API 609, and ISO 5211, ensuring easy identification for clients.
D. Flow Direction & Function Symbols
These symbols convey operational details:
- Flow Direction: One-way arrow (unidirectional, e.g., check valves) or two arrows (bidirectional, e.g., ball/butterfly valves).
- Normally Open (NO)/Normally Closed (NC): Labels indicating valve position when not actuated.
- Function Labels: “R” (relief), “REG” (regulating) for specialized valves.
E. Additional Feature Symbols
These represent optional features critical for specific applications:
- Soft Seal: “S” (PTFE/EPDM)
- Metal Hard Seal: “M” (Stellite overlay)
- Fire-Safe: Flame symbol (API 607 compliant)
- Anti-Blowout Stem: “ABS”
- Fugitive Emissions: “FE” (ISO 15848-1 compliant)
- Sour Service: “H₂S” (NACE MR0175 compliant)
TIANYU uses these symbols to highlight product advantages, such as corrosion resistance or safety features.
IV. Common Valve Type Symbols & Their Interpretations
Each valve type has a unique symbol combining the core components above. Below are detailed interpretations for the most common industrial valves, including TIANYU’s key products.
A. Ball Valve Symbols
Ball valves are rotary valves used for on-off and throttling applications. TIANYU’s line includes floating, trunnion-mounted, and three-piece (3PC) ball valves:
- Body Symbol: Circular/oval with piping connections on either side.
- Internal Mechanism: Small circle (ball) with a straight (full-port) or dashed (reduced-port) line.
- Variations:
- Floating Ball: Centered ball symbol (no supports), for small diameters.
- Trunnion-Mounted: Ball with top/bottom lines (trunnions), for high-pressure/large-diameter valves (TIANYU’s API 608-certified models).
- 3PC Ball: Body divided into three sections, indicating disassemblable design.
- Actuation: Handwheel, turbine, pneumatic, or electric symbols.
B. Butterfly Valve Symbols
Butterfly valves are compact rotary valves ideal for large diameters. TIANYU’s line includes concentric, double offset, and triple offset models:
- Body Symbol: Large circular shape with piping connections.
- Internal Mechanism: Straight line (disc); offset for double eccentric (TIANYU’s API 609-compliant flagship) or angled for triple eccentric.
- Seal Symbols: “S” (soft seal) or “M” (metal seal).
- Actuation: Handwheel, turbine, pneumatic (spring-return for hazardous environments), or electric.
C. Gate Valve Symbols
Gate valves are linear valves for on-off applications in high-pressure/temperature systems. TIANYU’s line includes rising and non-rising stem models:
- Body Symbol: Rectangular/square with piping connections.
- Internal Mechanism: Vertical/horizontal rectangle (gate); solid (rising stem) or dashed (non-rising stem).
- Stem Symbol: Straight line (rising) or coiled line (non-rising).
- Actuation: Handwheel, turbine, or hydraulic (large diameters).
D. Globe Valve Symbols
Globe valves are linear valves for throttling/regulation. TIANYU’s line includes standard and angle globe valves:
- Body Symbol: Rectangular with side (inlet) and top/bottom (outlet) connections.
- Internal Mechanism: Semicircle (disc) perpendicular to flow.
- Flow Direction: One-way arrow toward the disc.
- Actuation: Handwheel, electric (regulating), or pneumatic.
E. Check Valve Symbols
Check valves are automatic valves preventing backflow. TIANYU’s line includes swing, lift, and ball check valves:
- Body Symbol: Rectangular (linear) or circular (rotary).
- Internal Mechanism: Hinged disc (swing), vertical disc (lift), or small circle (ball).
- Flow Direction: One-way arrow (critical for installation).
- No Actuation Symbol: Automatic operation.
F. Plug Valve Symbols
Plug valves are rotary valves for corrosive/abrasive media. TIANYU’s line includes lubricated and non-lubricated models:
- Body Symbol: Circular/oval with piping connections.
- Internal Mechanism: Triangle/diamond (plug) with a line indicating the bore.
- Actuation: Handwheel, lever, or pneumatic.
- Seal Symbols: “L” (lubricated) or “NL” (non-lubricated).
G. Relief Valve Symbols
Relief valves are safety valves relieving excess pressure. TIANYU’s line includes pressure and safety relief valves:
- Body Symbol: Circular/rectangular with bottom (inlet) and top (outlet) connections.
- Internal Mechanism: Coiled line (spring).
- Flow Direction: One-way arrow upward.
- Pressure Set Point: Number (e.g., “PN25”) indicating opening pressure.
V. Valve Actuation Symbols in Detail
Actuation symbols are critical for understanding valve operation and fail-safe behavior. Below is a detailed breakdown of common actuation symbols, aligned with TIANYU’s products.
A. Manual Actuation Symbols
Manual actuation is cost-effective for infrequent operation:
- Handwheel: Circle with 4–6 spokes, for small-to-medium valves (TIANYU’s manual ball/butterfly valves, DN15–DN300).
- Lever: Straight line perpendicular to flow, for small valves (TIANYU’s DN15–DN50 ball/butterfly valves) requiring fast on-off cycles.
- Turbine Manual: Circle with gear inside, for large-diameter valves (TIANYU’s DN500+ trunnion-mounted ball/double offset butterfly valves) requiring torque reduction.
B. Pneumatic Actuation Symbols
Pneumatic actuation uses compressed air for automated systems:
- Double-Acting: Two rectangles (air cylinders), for systems without fail-safe requirements (TIANYU’s double-acting pneumatic valves).
- Spring-Return: One rectangle + coiled spring, with “NC” (fail-closed) or “NO” (fail-open) labels, for hazardous environments (TIANYU’s emergency shut-off valves).
C. Electric Actuation Symbols
Electric actuation uses a motor for remote control and precision:
- On-Off Electric: Small square (motor), for remote/hard-to-reach installations (TIANYU’s electric ball/butterfly valves).
- Regulating Electric: Square with “REG” inside, for precise flow/pressure control (TIANYU’s electric globe valves).
- SCADA-Compatible: Square with “SCADA” label, for integration into smart systems (TIANYU’s electric trunnion-mounted ball/double offset butterfly valves).
D. Hydraulic Actuation Symbols
Hydraulic actuation uses fluid for high-torque applications:
- Hydraulic: Circle with “H” inside, for large-diameter gate valves (TIANYU’s DN1000+ hydraulic gate valves) in mining/metallurgy.
VI. Application of Valve Symbols in Industrial Drawings
Valve symbols are most commonly used in Piping and Instrumentation Diagrams (P&IDs), with secondary applications in other industrial drawings.
A. Piping and Instrumentation Diagrams (P&IDs)
P&IDs are detailed drawings showing piping system layouts, with valve symbols playing a central role:
- They indicate valve location, type, actuation, flow direction, and connections to other components.
- TIANYU provides P&ID-compatible symbols for all products, ensuring easy integration into client drawings.
Best practices for P&IDs:
- Consistency: Use one standard (ASME Y14.35M for North America, ISO 128 for international projects) throughout.
- Labeling: Unique identifiers (e.g., “V-101”) for each valve.
- Clarity: Avoid overcrowding; use zoomed-in details for complex areas.
- Legend: Define all symbols used, especially for specialized valves (e.g., TIANYU’s double offset butterfly valves).
B. Other Industrial Drawings
- Piping Layout Drawings: Simplified valve symbols indicating position and pipeline connections.
- Valve Assembly Drawings: Basic symbols highlighting valve type and actuation, with detailed internal components.
- Maintenance Manuals: Symbols guiding technicians through disassembly/reassembly (TIANYU’s manuals use symbols to label key parts).
VII. Common Mistakes in Interpreting Valve Symbols & How to Avoid Them
Misinterpretation of valve symbols leads to procurement, installation, and operational errors. Below are common mistakes and solutions.
A. Mistake 1: Confusing Ball vs. Butterfly Valve Symbols
Mistake: Mixing up rotary valve symbols due to similar circular bodies.
Solution: Focus on internal mechanisms—ball valves have a small circle (ball), butterfly valves have a straight line (disc). TIANYU’s tip: Look for offsets (butterfly) or port lines (ball).
B. Mistake 2: Ignoring Pneumatic Actuation Variations
Mistake: Confusing double-acting and spring-return pneumatic symbols.
Solution: Double-acting has two rectangles; spring-return has one rectangle + spring, with “NC”/”NO” labels. TIANYU’s tip: Align with safety requirements (spring-return for hazardous environments).
C. Mistake 3: Misinterpreting Flow Direction
Mistake: Installing valves backwards (e.g., check valves).
Solution: Follow arrows—one-way for check valves, two-way for ball/butterfly valves. TIANYU’s tip: Valve bodies have flow arrows matching symbols.
D. Mistake 4: Overlooking Additional Feature Symbols
Mistake: Missing seal type or safety symbols, leading to incompatible valves.
Solution: Check for “S”/”M” (seal), flame (fire-safe), or “FE” (fugitive emissions) symbols. TIANYU’s tip: Cross-reference with datasheets.
E. Mistake 5: Using Outdated Symbols
Mistake: Using non-standard/outdated symbols, causing miscommunication.
Solution: Use current standards (ASME Y14.35M-2007, ISO 128-24:2021); update old drawings. TIANYU’s tip: Request updated symbols for TIANYU products.
VIII. TIANYU’s Advantage in Valve Symbol Standardization
Valve symbols are the universal language of industrial fluid control, enabling clear communication across teams while ensuring compliance with API, ASME, and ISO standards. This guide covers core symbols for all common valve types—including TIANYU’s ball valves, double offset butterfly valves, and gate valves—detailing their components, actuation, and applications. TIANYU’s valves feature symbols aligned with global standards, highlighting key features like metal hard seals, trunnion support, and SCADA compatibility. With standardized symbols and compliance-focused design, TIANYU ensures seamless integration into any industrial system, simplifying procurement, installation, and maintenance for clients worldwide.
