A ball valve is one of the most common valves used for commercial as well as residential plumbing applications.
The basic function of a ball valve is to on-off the flow using a handle. Ball valves are known for their long service life, performance and are often a preferred choice over Gate and globe valves.
To explore more about detailed comparison you may want to read our Gate valve vs ball valve post.
A ball valve symbol is denoted as follows:
A Ball Valve should not be confused with a “Ball Check Valve”, basically a type of Check Valve with a solid ball that is used to prevent undesired backward flow in the line.
Ball valves are also called a Quarter turn (1/4) shut-off valve as they require a quarter turn to close the valve enabling operation time shorter.
Ball valves structure comprised of five key components:
Ball
Stem
Seat
Gasket
Body
There are different types of balls used in the Ball valve as per the applications. For all three types of ball, the outer surface needs to be crystal smooth for the ball valve operation. These three types are Solid, Hollow & Cored. Let’s dive into detail to know each of them.
Solid balls are constructed from 100% compact casting or bar stock material with a solid hole having the same diameter throughout.
Due to their construction solid ball usually weigh more than hollow balls & cost more.
Solid ball is mostly used for smaller sizes of the ball valves.
Hollow ball as the name depicts is hollow from inside that has more room space for the fluid to fill.
Basically, it has a cavity that goes from the open hole from the bottom of the ball to the top where the stem of the valve is inserted.
Due to its hollowness, the flowing media changes its velocity and turbulence occurs.
This turbulence can create noise and prove to be inefficient. However, the hollow balls may have appreciable advantages in large-size valves.
Cored Ball is created by having a wall thickness consistency around the whole ball.
In this type of arrangement, the balls get cooled more evenly thus decreasing the amount of grinding once it has fully cooled.
Due to this feature, these balls are becoming more popular and are more cost-effective when compared to solid balls.
The ball valve open-close direction is determined by its stem which connects to the ball (solid ball / hollow ball / cored ball). The stem further connects to the ball disc to the lever, handle, or actuator. The stem controls the on-off ball function which rotates the ball disc in a typical ball valve construction.
Seat in ball valves is also known as the seal rings typically where the ball disc rests. It is around a donut-shaped disc that acts as sealing between the ball & body. The seat ring often comes in various materials like PTFE, Peek, Nylon with PTFE being majorly used.
The gasket provides excellent sealing to the stem & bonnet part. Most of the time the issue arises in this area that is why each component of the ball valve must be assembled carefully. If the components are assembled too loose, leakage will start, and if it is too tight the movement of the stem is restricted.
The body is the entire framework of the ball valve through which fluid flows. It fits the piping via bolted, threaded, or welded joints which holds the components together. The body acts as a barrier to the pressure load from the flowing media so that there is no transfer of pressure to the pipes.