What Are Butterfly Valves?

A butterfly valve is a quarter-turn rotational motion valve that is used to stop, regulate, and start fluid flow. It consists of a circular disc or vane that rotates 90 degrees within the pipe to allow or restrict flow. The disc is positioned in the center of the pipe, passing through the disc to a mechanism on the outside of the valve.

Primary Function

Butterfly valves provide efficient flow control in large diameter pipes where space and weight considerations are important. They offer quick operation, minimal pressure drop, and reliable sealing capabilities for various industrial applications.

Working Principle

The operation of a butterfly valve is simple:

• The disc rotates 90 degrees around the stem axis
• When parallel to flow: valve is fully open
• When perpendicular to flow: valve is fully closed
• Intermediate positions provide flow regulation
• Operation can be manual (lever, gear) or automated (actuator)

Key Components

• Body: Main housing that connects to the pipeline
• Disc: Flow control element that rotates
• Stem: Connects the disc to the actuator
• Seat: Provides sealing between disc and body
• Actuator: Mechanism to operate the valve (lever, gear, electric, pneumatic)

Types of Butterfly Valves

• Wafer Type: Most common, fits between pipe flanges
• Lug Type: Has threaded inserts for bolt connections
• Double Flange Type: Has integrated flanges at both ends
• Zero Offset: Disc rotates around its own axis
• Double Offset: Stem offset from disc center and seat axis
• Triple Offset: Three offsets for metal-to-metal sealing

Industries & Applications

• Water Treatment: Flow control in water distribution systems
• Chemical Processing: Handling corrosive and abrasive fluids
• HVAC Systems: Heating, ventilation, and air conditioning
• Oil & Gas: Pipeline isolation and control
• Marine Applications: Seawater handling and ballast systems
• Pharmaceuticals: Sanitary process lines
• Food & Beverage: Hygienic processing applications

Construction Materials

• Body Materials: Cast iron, ductile iron, carbon steel, stainless steel, PVC, CPVC
• Disc Materials: Stainless steel, aluminum bronze, ductile iron with coatings
• Seat Materials: EPDM, Viton, Buna-N, PTFE, metal seats
• Stem Materials: Stainless steel (304, 316, 416), galvanized steel

Advantages

• Compact and lightweight design
• Quick operation (quarter-turn)
• Lower cost compared to other valve types
• Minimal pressure drop when fully open
• Good flow regulation capabilities
• Suitable for large diameter pipes

Limitations

• Not ideal for throttling at low flow rates
• Potential for cavitation at high pressure drops
• Disc may obstruct flow even when fully open
• Limited high-temperature capabilities depending on seat material

Selection Considerations

• Pressure and temperature requirements
• Fluid compatibility with materials
• Flow characteristics needed
• Actuation method (manual vs. automated)
• Sealing requirements (bubble-tight vs. some leakage)
• Installation space constraints