1) The valve disc is in the shape of a ball, and it is constructed with a soft seat, making it similar in design to a cock.
2) The ball is usually rotated through the use of a lever handle. The ball allows straight-through flow when it remains in the open position and it prevents flow-through when the handle is rotated a quarter turn (90°). Because larger valves require more force to operate, they are equipped with a gear handle in place of a lever handle.
3) Although the mechanical and physical properties of the soft seat material provide a very tight shutoff, there are limitations for applications involving high temperatures. Ball valves are suitable for use with full-on, full-off flow control in general service. Due to their material and construction, ball valves are not appropriate for use in applications that require partial opening of the valve.