Working Principle of Ball Valve

Ball valves are evolved from plug valves, it control the open and close by rotate the sphere disc. The sphere disc are also called ball. The stem drive the ball rotate, and there is a hole pass its axis. When the ball hole aligns with the axis of the channel, ball valve is open, while trun the ball 90 degrees back, the ball hole is perpendicular to the axis of the channel, the fluid is blocked.