A ball valve is a valve that opens by the turn of a handle, gearbox or other actuation method attached to a ball, the part of the valve which controls the flow through it. The ball has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle or lever will be inline with the port position letting you "see" the valve's position. Position indicators will be applied to a gearbox or actuator as required. The ball valves, along with the butterfly valve and plug valve, are part of the family calledquarter turn valves.

Ball valves are durable and usually work to achieve perfect shutoff even after years of disuse. They are therefore an excellent choice for shutoff applications. There are two type of ball valves based on the ball type, floating ball valves and trunnion mounted ball valves. Depending on the bore size of the ball itself, ball valves are designated as full port ball valves and reduced port ball valves. A full port or more commonly known full bore ball valve has an over-sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted but the valve is larger and more expensive so this is only used where free flow is required, for example in pipelines which require pigging.

In reduced port or more commonly known reduced bore ball valves, flow through the valve is one pipe size smaller than the valve's outlet size resulting in flow area being smaller than pipe. As the flow discharge remains constant and is equal to area of flow (A) times velocity (V), A₁V₁ = A₂V₂ the velocity increases with reduced area of flow.

FBV ball valves designs include two piece split body, three piece split and welded ball valves.