Ball Valve

What is a ball valve and how does it work ?

A ball valve is a form of quarter-turn valve which uses a hollow ball to control the flow through it, the ball turns according to an external handle that is attached. It is open when the ball's hole is in-line with the flow and closed when it is turn 90° degrees by using the valve handle. When the flow is open the handle lies flat in alignment with the flow, and it is perpendicular to the flow when closed. This is a nice characteristic making for easy visual identification of whether the valve is open or closed. The shut position could be in either counter-clock-wise or clock-wise direction depending on installation.

One issue faced with a ball valve (not to be confused with a ball check valve) is that they trap the traveling liquid in the center cavity of the ball when the valve is closed. When that liquid freezes, the sides of the valve can crack due to the expansion of ice forming. Although there are solutions to this it is important to know.
In situations where the media is expected to freeze or otherwise expand inside of the ball, there is a vent drilled into the upstream side of the valve. This is called a vented ball. Safety is the number one concern when engineers specify a vented ball.

A ball valve should not be confused with a "ball-check valve", a type of check valve that uses a solid ball to prevent undesired backflow.

Why use a ball valve ?

Ball valves are durable, they are known for performing well after many cycles of being opened and closed. They are also reliable, closing securely even after long periods of use. These properties make them an excellent choice for stopping the flow and control applications. In these applications they are often preferred to gate valves and globe valves. Although by using ball valves instead you would be sacrificing the precision in throttling applications.