How does a butterfly valve operate?

A butterfly valve operates by utilizing a circular disc or plate that is mounted on a rotating shaft. The primary function of this mechanism is to regulate the flow of fluid through a pipe. When the valve is in an open position, the disc is rotated 90 degrees from its closed position, allowing fluid to flow freely. When the valve is closed, the disc is turned back to the closed position, effectively blocking the flow of fluid.

The choice indicating that the gate rotates 90 degrees in a water way accurately reflects the operational principle of a butterfly valve, which is design-driven for efficient flow control. The ability to rotate 90 degrees allows for quick and easy operation, making it ideal for applications where rapid stop-start functions are necessary.

In contrast, the other options do not accurately describe the valve's operation. The gates in those scenarios suggest different types of valve mechanisms that do not apply to the butterfly valve's design and functionality. The unique characteristic of the butterfly valve, with its 90-degree rotation, differentiates it from other types of valves, such as gate valves or lift valves, which operate using entirely different mechanisms.