Butterfly Valve Symbol in P&ID – Meaning, Standards & Representation (2025 Guide)

In every process facility—oil & gas, petrochemicals, power generation, water treatment, HVAC—the Piping & Instrumentation Diagram (P&ID) is the single source of truth for how a system is designed, controlled, and maintained. The butterfly valve symbol appears throughout these drawings for isolation and flow regulation points. Getting this symbol right avoids procurement errors, installation mistakes, and safety incidents. This guide explains the symbol’s meaning, how it’s drawn under ISO/ISA conventions, how actuators change its appearance, and how it differs from gate, globe, ball, and check valve symbols—so engineers and technicians can read drawings with confidence.

What is a Butterfly Valve Symbol in P&ID?

The butterfly valve symbol is the graphical shorthand used in P&IDs to communicate that a quarter‑turn rotary disc valve is installed at a point in the line. The base symbol is a circle intersected by a straight line, representing the disc inside the pipeline. By itself this typically denotes a manual wafer‑type valve; additions above or near the symbol denote actuators and other attributes.

Symbol Representation (Manual & Actuated)

2.1 Base / Manual Butterfly Valve

The simplest symbol is a circle cut by a straight line. The line represents the disc; its orientation is not a real‑time indicator of open/closed state in a static P&ID. If a handwheel or gear operator must be emphasized, a small wheel/gear glyph may be placed above the circle, or a note added in the tag list.

2.2 Actuated Butterfly Valves

Actuation adds a small icon above/adjacent to the base circle‑with‑line symbol:

• Electric actuator – rectangular box (often with an electrical connection mark) placed above the valve symbol.
• Pneumatic actuator – a small circle or diaphragm glyph indicating air operation.
• Hydraulic actuator – box/oval with a short line showing hydraulic line connection.
• Gear operator – handwheel symbol; sometimes the note “GEAR OP.” in the callout.
• Limit switches – small switch glyphs or the note “LS” in the instrument callout/IO list.

Tip: Always confirm against the project’s symbol legend. Companies follow ISA/ISO patterns but may have small house‑style tweaks.

International Standards (ISA / ISO / DIN)

While P&ID symbology is broadly consistent worldwide, drawings are governed by one or more standards. The most common for valves and instrumentation are:

• ISA 5.1 – Instrumentation Symbols and Identification (widely used in North America).
• ISO 14617 – Graphical symbols for diagrams (global framework for process industries).
• DIN conventions – German/European practices sometimes used in EU projects.
• ASME/ANSI – Complementary piping standards that influence notation and callouts.

In multi‑national projects, the legend page resolves any differences. If your site already has a Butterfly Valve Buyer’s Guide, link to it for quick reference on symbol snippets, HSN, and high‑level selection cues.

Butterfly vs Other Valve Symbols

For deeper design differences, you can cross‑link to: Types of Butterfly Valves – Working, Parts & Diagram and Lug vs Flanged Butterfly Valve.

Variants & Connection Indications

Why the Symbol Matters

• Design clarity: Prevents installing the wrong valve or actuator type.
• Cost control: Correct symbol → correct MTO → fewer change orders.
• Safety: Mis‑specified valves in firewater/critical services carry risk.
• Automation: Actuator and limit switch cues tie to IO lists and interlocks.
• Maintenance: Teams can anticipate manual vs motorised access and spares.

Practical Example: Water Treatment Plant

In a municipal WTP, P&IDs often place flanged butterfly valves on raw water pump discharges, actuated valves on filter backwash headers, and wafer manual valves on dosing skids. Symbols rapidly communicate which stations are automated, which can be isolated, and where tags tie to the PLC. For actuator pricing/selection, link users to Motorised Butterfly Valve Price List (2025).

How to Read Butterfly Valve Symbols

1. Locate a circle intersected by a line in the pipeline.
2. Check for actuator glyphs (electric/pneumatic/hydraulic/gear).
3. Look for connection clues (LUG, flanged ends) or notes.
4. Match the tag number (e.g., BV‑101) against the valve schedule.
5. Confirm details (size, class, material) in the specs list, not the symbol.

Typical Uses the Symbol Implies

• Water & wastewater: Large‑diameter isolation and throttling.
• Firewater rings: Double‑flanged, gear‑operated valves on hydrant mains.
• HVAC: Balancing and zone isolation—with electric actuators for BMS.
• Chemical/Marine: Stainless steel butterfly valves for corrosion resistance.
• Power/Oil & Gas: High‑performance offset designs with tight shut‑off.

Tags, Callouts & Notes You’ll See Beside the Symbol

• Valve Tag: BV‑### (e.g., BV‑203) cross‑references the schedule/IO list.
• Service: RW, BW, CW, FO, etc., indicating the line medium.
• Actuation: “ELEC”, “PNEU”, “HYD”, “GEAR”, “LS (limit switch)”.
• Connection: “LUG”, “FLG”, “DF” (double‑flanged) where relevant.
• Notes: Fail position (FO/FC), interlocks, or hazardous area classification.

Common Mistakes to Avoid

• Confusing symbols: Ball valve’s solid dot vs butterfly’s straight line.
• Assuming size from symbol: Size is not encoded; check the schedule.
• Ignoring actuators: Missing the small actuator glyph leads to wrong purchase.
• Missing legend: Always reconcile with the project’s legend and notes.
• Skipping interlocks: P&IDs often show LS/position feedback—don’t overlook it.

FAQs

Q1. What is the standard butterfly valve symbol in P&ID?

A circle intersected by a straight line representing the disc; actuator glyphs modify the base symbol.

Q2. How do actuated butterfly valves look on drawings?

Electric uses a small box; pneumatic a diaphragm/circle; hydraulic an oval/box with a line. Limit switches may be indicated as “LS”.

Q3. How do I tell butterfly from ball valve?

Ball valve = circle with a solid dot. Butterfly valve = circle with a straight line.

Q4. Does the symbol show size, class, or material?

No—those live in the valve schedule (e.g., BV‑203: 200 NB, Class 150, CI/SS, seat type, actuator).

Q5. Are symbols the same worldwide?

Close, but standards vary slightly. Your drawing’s legend is the final authority.

Get Help Selecting & Sizing Your Butterfly Valves

Udhhyog supplies CI, SS, and high‑performance butterfly valves—manual and motorised—with verified materials and documentation. For brand price lists, see Sant Butterfly Valve Price List (2025).

Related Guides

• Butterfly Valve Buyer’s Guide – Symbol, HSN Code, Sizes
• Types of Butterfly Valves – Working, Parts & Diagram Explained
• Lug vs Flanged Butterfly Valve – Full Comparison
• Triple Offset Butterfly Valve – 3‑Offset Design, Specs & Uses
• Stainless Steel Butterfly Valve – Buy SS Butterfly Valves Online
• Motorised Butterfly Valve Price List – Electric Actuator Rates (2025)