Butterfly valves are suitable for throttling under which conditions?

• A. High-flow, high-pressure
• B. Moderate-flow, moderate-pressure
• C. High-flow, low-pressure
• D. Low-flow, low-pressure

Answer: (D)

Butterfly valves regulate flow by rotating a disk inside the pipe, so their throttling behavior is most manageable when the differential pressure is low and the flow is modest. In low-flow, low-pressure service, it’s easier to position the disk to achieve a smooth, gradual change in flow with relatively little torque on the stem and minimal wear on the seat. The flow response at small openings is more predictable, yielding stable control without excessive noise or erosion.

When flow or pressure is high, the energy loss across the partially open valve becomes large, the torque required to hold or move the disk increases, and the flow characteristic becomes nonlinear and harder to control precisely. This can accelerate seat wear and reduce long-term throttling reliability. Because of these factors, butterfly valves are typically favored for throttling in low-flow, low-pressure conditions, while globe or other trim designs are preferred when fine, precise throttling is needed at higher flow or pressure.