Technical Guide
Valve Selection · 10 min read

Types of Butterfly Valves: A Complete Guide to Every Configuration

“Butterfly valve” covers a surprisingly broad family of valve configurations — from simple lever-operated wafer valves for small water lines to triple-offset metal-seated valves for high-temperature steam service. This guide maps every major type, explains where each is used, and helps you identify the right configuration for your application.

The butterfly valve family is more diverse than most engineers initially realise. What they share is the quarter-turn disc-in-bore operating principle — but beyond that, connection type, disc geometry, seat material, actuator type, and special certifications create a wide matrix of configurations suited to very different applications and industries.

This guide organises the full butterfly valve family along four axes: body/connection type, disc geometry (offset), actuator type, and seat material. Within each axis, we explain the design rationale, performance trade-offs, and typical application. A complete comparison table and a fire protection-specific section follow.

1. Classification by Body / Connection Type

The body type determines how the valve connects to the pipe system. This is often the first selection criterion because it is dictated by the existing or designed pipe system — you cannot install a wafer valve into a grooved pipe system without adapters.

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Wafer Butterfly Valve
Most common type
Designed to sit between two pipe flanges, held in place by long through-bolts that pass through both flanges and the valve body. No integral flanges on the valve itself — the pipe flanges do all the clamping. The EPDM seat acts as a gasket, eliminating the need for separate gasket material. Extremely compact face-to-face dimension (EN 558 Series 20 / API 609 Table 1). Suitable for most general isolation duty. Not suitable for dead-end or end-of-line service — requires a flange on both sides.

CA-FIRE Wafer Models →

⚙️
Lug Butterfly Valve
End-of-line capable
Similar to wafer style but with threaded lugs cast into the body that align with the flange bolt pattern. Each flange bolts independently to the valve body — the two flanges are not bolted to each other. This means one side of the pipe can be disconnected (e.g. for maintenance) while the valve remains bolted to the other side and retains pressure on that side. Required for dead-end or end-of-line service.
🔗
Grooved Butterfly Valve
Victaulic-compatible
Connects to grooved pipe using Victaulic-style couplings — no flanges required. The grooved ends on the valve body accept standard roll-groove couplings. Fastest installation of all connection types: each coupling requires only two bolts. Widely used in fire protection, HVAC, and commercial building services where grooved piping systems are standard. Provides some pipe flexibility (angular and linear movement absorbed by coupling). CA-FIRE ZSDF8 / ZSXDF8 series.

CA-FIRE Grooved Models →

Double-flanged butterfly valve

A fourth connection type — the double-flanged butterfly valve — has integral flanges cast into both ends of the body, with full bolt holes. This gives the highest structural rigidity and is typically specified for large-diameter valves (DN400 and above) in water mains, sluice gates, and pump station applications where the valve must support significant pipe loads. Face-to-face dimensions are longer than wafer style. Less common in building fire protection due to size and cost, but occasionally specified on large fire water storage and pumping systems.

2. Classification by Disc Geometry (Offset)

The geometry of the disc relative to the valve stem and seat is one of the most significant design variables in butterfly valve engineering. It determines seating tightness, pressure rating, wear characteristics, and suitability for high-temperature or high-pressure service.

Concentric (Zero-Offset)
Resilient seated · Standard duty
The disc stem axis is concentric with the pipe bore and the seat. The disc rotates through the seat as it opens and closes, creating continuous contact between the disc edge and the elastomeric seat. This wiping action provides excellent sealing but causes seat wear over time. Suited to water, HVAC, and fire protection service at pressures up to 1.6 MPa. This is the design used in all CA-FIRE fire protection butterfly valves.
Single Offset
Reduced wear · Moderate pressure
The stem is offset from the disc centreline, so the disc pulls slightly away from the seat as it begins to open. This reduces the wiping travel and extends seat life compared to concentric designs. Less common than concentric or double-offset; used in some water treatment and industrial applications.
Double Offset (High Performance)
Metal seated option · Up to 4.0 MPa
Two offsets: the stem is offset from both the disc centreline and the pipe centreline. The double offset creates a cam action that lifts the disc clear of the seat within the first few degrees of opening — eliminating the sliding contact that wears concentric seats. Suitable for higher pressure (up to 4.0 MPa), bi-directional shutoff, and metal seat configurations. Common in oil & gas, chemical, and power generation.
Triple Offset (TOV)
Metal seated · High temp / pressure
A third offset creates a conical seating geometry — the disc and seat make zero rubbing contact until the final moment of closure, when they seat in a pure compression motion. This eliminates seat wear entirely and allows metal-to-metal seating for high-temperature (up to 600°C), high-pressure (up to 10+ MPa), and cryogenic service. Used in LNG, power, and refinery applications. Significantly higher cost than concentric.
Fire protection note: Fire suppression systems operating at standard working pressures (up to 1.6 MPa, ambient temperature, clean water) use concentric resilient-seated butterfly valves — the concentric design provides the bubble-tight EPDM seal required and is the most cost-effective configuration for this service. Double-offset and triple-offset valves are unnecessary and not typically specified for standard fire protection duty.

3. Classification by Actuator Type

The actuator is what you use to operate the valve — to rotate the disc from open to closed. The four main actuator types each suit different scenarios.

🔧 Lever Handle
Direct quarter-turn manual handle. Fastest to operate — open or closed in under 2 seconds. Lever is lockable in intermediate positions on most designs. Practical for DN50–DN100 at standard pressures; impractical above DN125 at 1.6 MPa due to torque requirements. CA-FIRE: ZSDF7-S / ZSXDF7-S (wafer), ZSDF8-S / ZSXDF8-S (grooved).
⚙️ Worm Gear (Handwheel)
Mechanical reduction gear converts handwheel rotation into disc rotation, providing high mechanical advantage. Standard for DN100–DN300 and above at working pressure. Requires 10–15 handwheel turns to complete operation. Self-locking: the disc stays in position when handwheel is released. CA-FIRE: ZSDF7 / ZSXDF7 (wafer), ZSDF8 / ZSXDF8 (grooved).
⚡ Electric Actuator
Motor-driven actuator that opens/closes the valve on a control signal (on/off or modulating). Used for remote operation, automation, and frequent cycling applications. Requires power supply and control wiring. Available in explosion-proof versions for hazardous areas. Standard for automated fire suppression systems, building management integration, and large DN valves where manual operation is impractical.
💨 Pneumatic Actuator
Air-powered actuator (spring-return or double-acting). Very fast operation — typically 1–5 seconds for full stroke. Suitable for hazardous areas (inherently safe with no electrical spark risk). Requires compressed air supply. Common in chemical, petrochemical, and process plants where plant air is available. Spring-return designs provide fail-safe open or fail-safe closed position on air loss.

4. Classification by Seat Material

The seat material determines chemical compatibility, temperature range, and sealing performance. It is selected primarily by fluid type and operating temperature.

Seat Material Temp Range Chemical Compatibility Typical Applications Notes
EPDM −30°C to +120°C Excellent — water, steam, dilute acids/alkalis, AFFF foam Fire protection, potable water, HVAC, wastewater Standard for fire protection. Not compatible with oils, hydrocarbons, or solvents.
NBR (Nitrile) −20°C to +80°C Water, oils, fuels, compressed air Compressed air, fuel lines, oil systems, some chemical service Good oil/fuel resistance. Less suitable than EPDM for water service at elevated temperature.
PTFE / TFM −40°C to +180°C Excellent — most acids, alkalis, solvents, aggressive chemicals Chemical processing, pharmaceutical, food service, high-purity water Lowest friction of all seats. Hard seat — higher torque than EPDM. Not suitable for high-velocity slurry.
Silicone −60°C to +200°C Water, steam, food contact fluids Food & beverage, pharmaceutical, high-temperature steam FDA/EC 1935/2004 food contact compliant. High temperature range.
Metal (SS316, Stellite) −200°C to +600°C+ All fluids including cryogenic and high-temp gases LNG, steam, refinery, power generation Zero wear seat. Requires double or triple offset disc geometry. High cost.

5. Special-Purpose Butterfly Valve Types

Signal / Supervisory Butterfly Valve (信号蝶阀)

A standard butterfly valve body fitted with an integrated DC24V tamper switch (supervisory switch) in the actuator housing. When the valve moves from the fully open position, the switch sends a supervisory signal to the fire alarm control panel. This type is mandatory for electrically supervised fire protection systems under NFPA 13 §6.1 and GB 50084. The “signal” in the Chinese name (信号蝶阀) refers to this supervisory electrical signal. CA-FIRE ZSXDF7 and ZSXDF8 are signal butterfly valves.

Explosion-Proof Butterfly Valve (防爆蝶阀)

A butterfly valve whose actuator (gear housing, tamper switch, and all electrical components) is certified to explosion-proof standards — ATEX, IECEx, or NEPSI (China). The Ex certification allows the valve to be installed in Zone 1/2 (gas hazards) or Zone 21/22 (dust hazards) classified areas without risk of igniting the hazardous atmosphere. Required for fire water systems in petrochemical facilities, offshore platforms, paint shops, and fuel storage areas. CA-FIRE’s explosion-proof series carries NEPSI certification to Ex db IIC T6 Gb + Ex tb IIIC T80°C Db, IP66.

High-Performance Butterfly Valve (HPBV)

Industry shorthand for double-offset butterfly valves — the “high performance” refers to higher pressure rating (Class 150–600, up to ~10 MPa), metal seat option, and bi-directional shutoff capability versus standard concentric resilient-seated designs. Common in oil & gas, chemical, and power generation. Not typically specified for fire protection at standard pressures.

Knife Gate Valve (related type)

Technically not a butterfly valve, but often confused with one. A knife gate valve uses a flat gate that slides perpendicular to the pipe bore (like a standard gate valve) but with a sharpened blade edge designed to cut through slurry, fibrous media, or thick fluids. Used in mining, pulp & paper, and wastewater sludge lines. Not suitable for fire protection or clean water isolation duty.

6. Full Comparison Table

Type Max Pressure Connection Seat Best For Avoid When
Wafer, concentric, EPDM, lever 1.6 MPa Flanged (both sides) EPDM Fire protection, HVAC, water — DN50–DN100 Dead-end service; DN125+
Wafer, concentric, EPDM, gear 1.6 MPa Flanged (both sides) EPDM Fire protection, HVAC, water — DN50–DN300 Dead-end service
Lug, concentric, EPDM, gear 1.6 MPa Flanged (dead-end OK) EPDM End-of-line, isolation valves Grooved pipe systems
Grooved, concentric, EPDM, gear 1.6 MPa Grooved couplings EPDM Fire protection, HVAC — grooved pipe Flanged-only systems
Double-offset, metal seat 4.0 MPa+ Flanged Metal/PTFE Oil & gas, chemical, high-pressure Standard fire protection — over-specified and costly
Triple-offset (TOV) 10+ MPa Flanged Metal LNG, steam, refinery Any ambient-temperature water service
Signal / supervisory 1.6 MPa Wafer or grooved EPDM Monitored fire protection — NFPA 13 compliance General industrial isolation (tamper switch not needed)
Explosion-proof 1.6 MPa Wafer or grooved EPDM Hazardous area fire systems — Zone 1/2 Non-hazardous locations — unnecessarily costly

7. Which Types Are Used in Fire Protection?

For the vast majority of fire sprinkler, wet riser, foam suppression, and fire main applications, two butterfly valve configurations cover essentially all requirements:

Standard Fire System
Concentric · Resilient EPDM · Wafer or Grooved · Gear or Lever
The standard configuration for virtually all fire protection applications. Body: GGG40 ductile iron or SS316. Seat: EPDM. Connection: wafer flanged or grooved. Actuator: lever (DN50–DN100) or worm gear (DN50–DN300). With or without DC24V tamper switch depending on supervisory requirement.
Hazardous Area Fire System
Concentric · EPDM · Wafer or Grooved · Ex-Rated Gear
Required for fire water systems in petrochemical facilities, offshore platforms, paint shops, fuel storage areas, and any Zone 1/2 classified installation. All electrical components (gear housing, tamper switch) carry NEPSI/ATEX/IECEx explosion-proof certification.
CA-FIRE product range: CA-FIRE manufactures all four standard fire protection butterfly valve configurations — gear operated wafer, gear operated grooved, lever wafer, and explosion-proof — all certified to GB 5135.13, DN50–DN300, 1.6 MPa working pressure. Visit the full butterfly valve family page or contact sales@ca-fire.com for project quotations.

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CA-FIRE Protection · 川安消防实业有限公司

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