Final answer:
Butterfly valves typically require a one-quarter turn to change from fully open to fully closed, making operation quick and efficient for applications that demand fast action.
Step-by-step explanation:
Butterfly valves are a type of valve used for regulating or isolating fluid flow. The operation of a butterfly valve involves the rotation of a disc to allow, restrict, or stop the flow of fluid. When it comes to how many turns it takes for a butterfly valve to change from fully open to fully closed, the answer varies depending on the design of the specific valve.
In practice, most standard butterfly valves are designed to go from a fully open to fully closed position with a quarter-turn motion, which equates to a 90-degree turn of the valve handle or actuator. This quick operation is beneficial for applications that require fast and frequent operation of the valve. Therefore, the correct answer to the question "How many turns does it take for a butterfly valve to move from fully open to fully closed?" would be (a) One-quarter turn.