What Is A Ball Valve?

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.

These ball vales can be 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 a gate valve.

For a complete comparison, read our 4 COMMON TYPES OF BALL VALVES article.

Ball valves are more resistant against contaminated media than most other types of valves. In some 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. For example, it still ensures a reliable sealing, even in the case of dirty media.

3 common ball valve types:

Standard

Standard ball valves consist of the housing, seats, ball and lever for ball rotation. They include valves with two, three and four ports which can be female or male threaded or a combination of those. Threaded ball valves contain internal and external threads to facilitate inlet and outlet connections

Flanged

Flanged ball valves are 1-piece or 2-piece ball valves that provides effective control of oil and gas operations. Its defining trait is the flanged ends that bolt to oil and gas pipelines. You can easily install or remove this valve from a pipeline or piping system.

Standard

A vented ball valve has a small hole drilled into it's upstream side, which is different from a standard ball valve. Venting the pressure through the "vent" on the ball eliminates the unwanted pressure inside of the valve. Generally speaking, the purpose of a specifically vented ball in a ball valve remains the creation of a flow path that will allow the trapped service medium a means of egress from the isolated cavity created inside the valve when the ball rotates into the closed position.

How Does A Ball Valve Work?

To understand the working principle of a ball valve, it is important to know these 4 main ball valve parts and 2 different operation types. The 5 main components can be seen in the ball valve diagram in the above image diagram. The valve stem (1) is connected to the ball (4) and is either manually operated or automatically operated (electrically or pneumatically). The ball is supported and sealed by the ball valve seat (5) and their are o-rings (2) around the valve stem. All are inside the valve housing (3).

The ball has a bore through it. When the valve stem is turned a quarter-turn the bore is either open to the flow allowing media to flow through or closed to prevent media flow. The valves circuit function, housing assembly, ball design, and operation types all impact the ball valves operation are discussed below.

Ball Valve Circuit function

The ball valve may have two, three or even four ports (2-way, 3-way or 4-way). The vast majority of ball valves are 2-way and manually operated with a lever. The lever is in line with pipe when the valve is opened. In closed position, the handle is perpendicular to the pipe.

The ball valve flow direction is simply from the input to the output for a 2-way valve. Manually operated ball valves can be quickly closed and therefore there is a risk of water hammer with fast-flowing media.

Some ball valves are fitted with a transmission. The 3-way valves have an L-shaped or T-shaped bore, which affect the circuit function (flow direction). As a result, various circuit functions can be achieved such as distributing or mixing flows.

Ball Valve Housing Assembly

The assembly of the valve housing can be divided in three commonly used designs: 1-piece, 2-piece and 3-piece housings. The difference is how the valve is assembled and this affects the possibilities for maintenance or repair. The operation of the valves is the same in each embodiment.

1-piece: This is the cheapest variant. The two parts which enclose the ball are pressed or welded. The valves cannot be opened for cleaning or maintenance. This type is generally used for low-demanding applications.

2-piece: Two-piece valves can be disassembled for cleaning, servicing and inspection. Often, the parts are connected via a threaded connection. The valve must be completely removed from the pipe in order to separate the two parts.

3-piece: More expensive valves have often three pieces. The parts are generally clamped together by bolt connections. The advantage of this embodiment is that the valve can be serviced without removing the entire valve from the pipeline.

If you'd like to find out more and are looking for experienced professionals in the design and manufacturing industry, you may contact Fujikin Singapore at enquiry@fujikin.com.sg or at +65 6848 5760.