20.07.2026 10:37
What Is a Butterfly Valve?
A butterfly valve is a quarter-turn valve used to start, stop or regulate the flow of liquids, gases and other media in a pipeline. Its compact construction, low weight, rapid operation and simple installation make it suitable for water systems, industrial plants, HVAC installations and many other applications.
A circular disc is positioned inside the valve body. This disc rotates around the valve stem and moves between the fully open and fully closed positions through a 90-degree movement.
Operating Principle
A butterfly valve operates with a quarter-turn mechanism. The valve stem transfers the movement generated by a lever, gearbox or actuator to the disc.
When the disc is parallel to the flow direction, the valve is fully open.
When the disc is perpendicular to the flow direction, the valve is closed.
When the disc is positioned at an intermediate angle, the flow can be partially regulated.
Because the disc requires only a 90-degree rotation, the valve can open and close rapidly.
Fully Open Position
When the operating lever is parallel to the pipeline, the disc is also positioned parallel to the flow. The medium passes around the disc and continues through the pipeline.
Since the disc remains inside the flow path, a certain pressure drop may occur. With correct valve sizing and suitable operating conditions, this pressure loss can be kept at an acceptable level.
Closed Position
When the stem is rotated by 90 degrees, the disc becomes perpendicular to the flow. The outer edge of the disc presses against the resilient seat or sealing element inside the valve body.
This contact closes the flow path and prevents the medium from passing through the valve. Sealing performance depends on seat material, disc surface, pressure, temperature and the chemical properties of the medium.
Flow Regulation
Butterfly valves may also be used for flow regulation in suitable systems. When the disc is kept at an intermediate angle, the available flow area becomes smaller and the flow rate decreases.
For precise control applications, valve size, velocity, differential pressure and cavitation risk should be carefully evaluated. Continuous operation at a very small opening may cause excessive wear on the disc and seat.
Main Components
Body: The main structural component of the valve. It may be manufactured in wafer, lug or flanged designs.
Disc: The rotating component that starts, stops or restricts the flow.
Stem: Transfers the operating movement from the lever, gearbox or actuator to the disc.
Seat: Provides sealing between the disc and the valve body. Common materials include EPDM, NBR and PTFE.
Lever or gearbox: Allows manual opening and closing.
Actuator: Enables automatic or remote operation through electric, pneumatic or hydraulic power.
Operating Options
Small-diameter butterfly valves are commonly operated with a hand lever. Gear operators are preferred for larger sizes to reduce the torque required for opening and closing.
Butterfly valves can also be equipped with:
Electric actuators
Pneumatic actuators
Hydraulic actuators
Position indicators
Limit switches
Control units
These systems allow the valve to be opened, closed or positioned remotely according to process requirements.
Advantages
Rapid quarter-turn operation
Compact and lightweight design
Low installation space requirement
Economical solution for large diameters
Suitable for manual and automated operation
Easy maintenance
Different body, disc and seat material options
Efficient shut-off performance
Application Areas
Butterfly valves are widely used in:
Drinking and utility water systems
Wastewater plants
Fire protection systems
Heating and cooling installations
HVAC systems
Irrigation networks
Industrial process lines
Seawater applications
Food and chemical facilities
Pumping and treatment stations
The body, disc and seat materials must be selected according to the medium, working pressure and operating temperature.
VANEX VALVE Butterfly Valve Solutions
VANEX VALVE butterfly valves are designed to provide reliable flow control, durable construction, easy operation and long service life. Lever-operated, gearbox-operated and actuated options are available for different diameter, pressure and automation requirements.
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