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Engineering-style overview of Butterfly Valves, including types, specifications, technical details, and typical price ranges, along with reference diagrams/images to help understanding.

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🦋 Butterfly Valve – Overview

A butterfly valve is a quarter-turn rotary valve used to start, stop, or regulate fluid flow. It uses a circular disc mounted on a shaft that rotates 90°:

• 🔓 Disc parallel to flow → Fully open

• 🔒 Disc perpendicular → Fully closed

It is widely used in:

• Water supply systems

• HVAC systems

• Chemical industries

• Oil & gas pipelines

• Fire protection systems (Wikipedia)

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📊 Main Types of Butterfly Valves

1. Concentric (Zero Offset) Butterfly Valve

🔧 Technical Details

• Disc and shaft are aligned at center

• Uses soft elastomer seat (EPDM/NBR)

• Bi-directional sealing

• Cheapest and most common type

📌 Specifications

• Pressure: PN6–PN16 (up to ~16 bar)

• Temperature: up to 120–200°C (depends on seat)

• Sizes: DN50–DN1200+

• Body: Cast Iron / Ductile Iron / Stainless Steel

⚙️ Applications

• Water pipelines

• HVAC systems

• Firefighting systems

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2. Double Offset (High Performance) Butterfly Valve

🔧 Technical Details

• Shaft offset from center (2 offsets)

• Reduces friction between disc & seat

• Better sealing than concentric type

• Suitable for higher pressure & temperature

📌 Specifications

• Pressure: up to PN25–PN40 (higher in some designs)

• Temperature: up to ~300°C

• Seat: PTFE / metal / laminated sealing

⚙️ Applications

• Oil & gas

• Steam lines

• Chemical processing

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3. Triple Offset Butterfly Valve (TOBV)

🔧 Technical Details

• 3 offsets eliminate rubbing completely

• Metal-to-metal sealing

• Zero leakage capability (bubble-tight)

• Designed for extreme conditions

📌 Specifications

• Pressure: ANSI 150–2500

• Temperature: -196°C to +600°C+

• Seat: Metal (stainless steel / Inconel)

⚙️ Applications

• LNG / cryogenic systems

• Power plants

• High-pressure steam & gas lines

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4. Wafer Type Butterfly Valve

🔧 Technical Details

• Sandwiched between two flanges

• No threaded lugs

• Lightweight and compact

📌 Specifications

• Pressure: PN6–PN16

• Size: DN40–DN600+

• Material: CI / DI / SS

⚙️ Applications

• Water treatment plants

• HVAC ducts

• General piping systems

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5. Lug Type Butterfly Valve

🔧 Technical Details

• Has threaded inserts (lugs)

• Can isolate one side of pipeline

• Easier maintenance than wafer type

📌 Specifications

• Pressure: PN10–PN25

• Material: Cast Iron / Stainless Steel

• End connection: Bolted flange

⚙️ Applications

• Chemical plants

• Industrial pipelines requiring isolation

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📐 Common Technical Specifications (All Types)

Parameter	Typical Range
Size (DN)	DN25 – DN2000+
Pressure Rating	PN6 – PN40 (up to Class 150–2500 for TOBVs)
Temperature	-40°C to 600°C (based on seat type)
Body Materials	CI, DI, WCB, SS304, SS316
Disc Materials	SS304 / SS316 / Duplex steel
Seat Materials	EPDM, NBR, PTFE, Metal
Operation	Manual / Gear / Electric / Pneumatic
Flow Control	On/Off + Throttling

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⚙️ Working Principle (Technical)

• Rotates 0°–90°

• Disc controls flow obstruction

• Flow resistance increases as valve closes

• Always creates some pressure drop (even fully open) (Wikipedia)

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💰 Butterfly Valve Price Range (India Market)

Type	Price Range (INR)
Concentric (Wafer)	₹800 – ₹5,000
Lug Type	₹2,000 – ₹15,000
Double Offset	₹8,000 – ₹50,000
Triple Offset	₹25,000 – ₹2,00,000+

👉 Price depends on:

• Size (DN)

• Material (CI vs SS316)

• Pressure class

• Actuation (manual vs automated)

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📌 Key Advantages

• Compact & lightweight

• Low cost compared to gate/globe valves

• Quick operation (quarter turn)

• Easy automation

• Suitable for large diameter pipes (Industrial Information)

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⚠️ Limitations

• Disc always remains in flow → pressure drop

• Not ideal for slurry-heavy fluids

• Lower sealing performance in basic types

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