A Butterfly Valve is a quarter-turn shutoff valve with a flat disc that rotates 90 degrees to modulate flow through a circular opening. Butterfly valves provide excellent flow control with minimal pressure drop, making them ideal for large HVAC applications.
Design and Performance
Butterfly valves feature a thin rotating disc centered in the valve body that moves parallel to flow direction. They require only 90-degree rotation to transition from fully closed to fully open, enabling fast operation. Pressure drop ranges from 1-3 psi at rated flow depending on disc position, significantly lower than globe valves. Sizes range from 2-inch to 24-inch diameters in commercial HVAC systems, with Cv values between 30 and 800. The streamlined design reduces friction losses and supports energy-efficient system operation.
System Applications
Butterfly valves serve as isolation and balancing valves in chilled water, condenser water, and hot water distribution loops. Their low pressure-drop characteristic suits low-head pump systems and applications prioritizing energy efficiency. They handle larger flow rates than globe valves with lower actuator torque requirements. Butterfly valves are less suitable for precise proportional control due to their non-linear flow characteristics.