Ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball (called a "oating ball") to control ow through it. It is open when the ball's hole is in line with the ow and closed when it is pivoted 90- degrees by the valve handle. The handle lies
at in alignment with the ow when open, and is perpendicular to it when closed, making for easy visual conrmation of the valve's status.Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications,
where they are often preferred to gates and globe valves, but they lack their ne control in throttling applications.