A ball valve is a shut off valve that controls the flow of a liquid or gas by means of a rotary ball having a bore. By rotating the ball a quarter turn (90 degrees) around its axis, the medium can flow through or is blocked. They are characterized by a long service life and provide a reliable sealing over the life span, even when the valve is not in use for a long time. As a result, they are more popular as a shut off valve then for example the gate valve. For a complete comparison, read our gate valve vs ball valve article. Ball valves are more resistant against contaminated media than most other types of valves.
In special versions, ball valves are also used as a control valve. This application is less common due to the relatively limited accuracy of controlling the flow rate in comparison with other types of control valves. However, the valve also offers some advantages here. For example, it still ensures a reliable sealing, even in the case of dirty media.
Ball Valve Function Basics
A ball valve functions as a quarter-turn valve, which controls flow through a hollow, perforated, and pivoting sphere, hence the name. It is in the same valve family as butterfly valves and plug valves, which are also quarter-turn valves. The sphere has a port, or a bore, in its center, which is critical to its function. When the bore in the ball valve function is lined up with the associated pipeline, the valve is open, so fluid can move through the bore. Turned 90 degrees, it is situated perpendicular to the flow of the fluid, so the valve is closed and the fluid can’t come through. That being said, ball valve function is not well suited to applications in which you need to throttle the flow of a fluid.
The way a ball valve functions makes it easy to see if the valve is open or shut. The handle that operators use to adjust where the sphere is aligned with the flow when the valve is open, and it is perpendicular when the valve is closed. And the ball valve can be devided into many different types for different functions, such as floating ball valve, trunnion mounted ball valve, top entry ball valve, dbb ball valve, subsea ball valve, etc.