What Is a Ball Valve?- Parts, Types, And Working

Valves come in many forms and dimensions, each designed to manage the movement of liquids or gases. At its core, a valve serves a straightforward purpose: it allows us to start or stop the flow as needed. Consider, for instance, the kitchen faucet a familiar example most of us interact with daily. In the following discussion, I will focus specifically on one kind of valve: the ball valve.

What Is a Ball Valve?

A ball valve operates as a quarter-turn mechanism, utilizing a pivoting, perforated sphere to regulate the movement of fluids or gases. When the opening within the ball is aligned with the direction of flow, passage is unobstructed. Conversely, rotating the ball by 90 degrees effectively blocks the flow entirely.

The position of the handle offers a straightforward way to determine whether the valve is open or closed. If the handle is aligned with the valve body, it indicates an open state; if it sits perpendicular, the valve is closed.

One of the reasons ball valves are favored in many settings is their durability. They are particularly suited to situations where a straightforward on/off control is required, performing reliably even after numerous cycles. Their secure sealing also persists after extended periods of inactivity, which adds to their appeal in applications where reliability is non-negotiable.

While the primary function is shutoff, users can adjust the flow rate by partially rotating the valve, though precision is somewhat limited. Compared to gate or globe valves, ball valves offer distinct advantages in terms of robust shutoff and ease of use, but they do not provide the nuanced control necessary for applications that require fine throttling.

How Does Ball Valve Work?

A ball valve serves as a shut-off device in piping systems, controlling the movement of liquids and gases by means of a ball with a central bore. This ball, which is rotated precisely 90 degrees, sits securely between two seats within the valve. Its stem connects to an external operating mechanism—often a handle or actuator—that enables the rotation.

The function of the valve is quite straightforward. When the bore of the ball aligns at a right angle to the direction of flow, the passage is blocked and no fluid can move through. However, once the bore lines up with the flow, the pathway opens, allowing the liquid or gas to pass freely.

Ball valves fall into the category of quarter-turn valves, a group that also includes plug and butterfly valves. Their practicality has made them a common fixture in a wide range of piping applications. Operators can control these valves manually—using a lever or wrench—or rely on automated actuators for more remote or frequent operation.

During manual use, the lever arm requires a quarter turn—either clockwise or counterclockwise—to transition between open and closed positions. When the lever is parallel to the pipe, this indicates the valve is open. If the lever stands perpendicular to the pipe, the valve is closed.

It’s worth noting that ball valves are designed primarily for full shut-off or complete opening; they do not offer precise control over flow rates. For this reason, using a ball valve to throttle or finely regulate flow is generally discouraged, as they are not built for such adjustments.

Parts of a Ball Valve

Ball valves are constructed with several crucial components:

• Valve Body: The valve body serves as the foundation of the entire valve assembly, housing all the critical components required for regulating on/off flow.
• Rotary Ball: At the heart of the valve is a ball featuring a central bore—essentially a hole that allows media to pass through. By turning the stem, the orientation of the ball changes, controlling whether flow is permitted or blocked.
• Stem: The stem acts as the link between the rotary ball and the external control system. In the case of a manual valve, this usually means a handle or lever that the operator can turn.
• Seats: Positioned between the valve body and the ball, the seats function both as a seal to prevent leaks and as a support for the ball itself.
• Power Source: Movement of the stem—and therefore the ball—can be achieved either manually or automatically. Manual control typically involves a lever or handle, while automated options might use electric motors, pneumatic systems, or hydraulic actuation.
• Packing: To prevent the process media from leaking around the stem, a packing seal is installed. This ensures the valve maintains its integrity during operation.
• Bonnet: Finally, the bonnet is the section of the valve body that encloses both the stem and the packing, keeping these essential elements protected and contained.

Types of Ball Valve

There are four general body styles of ball valves: single body, split body, top entry, and welded. There are four general types of ball valves: full port, standard port, reduced port, and v port.

• Full port ball valves are designed with an oversized ball, such that the opening within the ball matches the diameter of the pipeline. This configuration minimizes friction loss and ensures that the flow remains unimpeded. However, it is important to note that this advantage comes at the cost of a larger overall valve size.
• Standard port ball valves, by contrast, typically feature a smaller ball and a reduced port size. While these valves are generally more cost-effective, they do introduce a slight restriction to flow, as the port is one pipe size smaller than the valve’s nominal size. In the case of reduced port ball valves, this restriction becomes more pronounced, with the flow being limited by the smaller passage relative to the pipe size.
• The v port ball valve, sometimes referred to as a Venturi port valve, is characterized by a ball or seat with a ‘v’ shape. This unique geometry enables a more controlled opening and closing of the orifice, providing a flow characteristic that is closer to linear. When the valve transitions from the closed position, the smaller end of the ‘v’ opens first, allowing for stable regulation of flow at low openings. Due to the increased fluid velocities encountered during operation, this type of valve generally necessitates a more robust construction to withstand potential wear that would compromise a standard valve.
• In the case of the trunnion ball valve, the ball is mechanically anchored at both the top and bottom. This design is particularly well-suited for applications involving larger valve sizes (typically four inches and above) and higher pressures (600 psi and above).
• Manually operated ball valves can be closed rapidly, which poses the risk of water hammer within the system. To mitigate this, some ball valves are fitted with actuators that may be operated pneumatically or electrically. These actuated valves are suitable for both on/off and modulating flow control. Furthermore, pneumatic flow control valves are often equipped with a positioner, which translates the control signal into the corresponding actuator position and valve opening, thereby enabling precise regulation.

Ball Valve Types Based on Valve Housing:

The ball valve divides into the following commonly used types.

1. Single Body or One-Piece Ball Valve:

Among the various types of ball valves, the single body, or one-piece valve, is quite well-known. This design features a solid cast body, which helps minimize the chance of leaks. Cost-wise, it tends to be the most affordable option.

However, one limitation is that single body ball valves cannot be taken apart for maintenance or cleaning. You’ll most often find these valves in applications where the demands aren’t particularly high.

They usually come with smaller openings, making them more economical, but they’re also generally intended to be disposable rather than serviced.

2. Two-Piece Ball Valve:

A two-piece valve is constructed from two distinct sections. The first section incorporates one end joint along with the main body, while the second section attaches directly to it, housing the trim in position and providing the second end joint. This design allows the valve to be disassembled as needed for tasks such as inspection, routine maintenance, or thorough cleaning.

It is important to note that, for the separation of these two sections, the valve must be fully removed from the pipeline. In most cases, the internal diameter of a two-piece ball valve is slightly reduced compared to the nominal size, and typically, these valves can be either utilized or repaired a single time before replacement is necessary.

3. Three Piece Body Valve:

Three-piece ball valves consist of a main body and two end caps, typically fastened together with bolts. This configuration is designed to allow the core components—such as the seat, stem, and ball—to be removed from the pipeline with minimal effort.

With this setup, it becomes much easier to clear out debris, replace worn seats and seals, or even smooth out minor scratches on the ball itself—all without having to detach the valve from the existing pipework.

This practical advantage means maintenance and repairs can often be carried out quickly and efficiently, minimizing downtime. However, it’s worth noting that this convenience comes at a higher cost compared to other ball valve designs.

4. Top Entry Valve:

This particular type of ball valve is designed so that the ball component can be assembled from the side or the top section of the valve body. One of the notable features of this design is that it enables maintenance of both the seat and the ball without requiring the entire valve to be taken apart.

For larger valve bodies, this style tends to be the preferred option. Importantly, the valve does not need to be removed from the pipeline during servicing.

Typically, these valves are manufactured using cast metal. Given that casting can introduce certain imperfections, it is standard practice to conduct additional non-destructive testing (NDT) to verify the integrity of the finished product.

One of the advantages of this design lies in its reduced reliance on threaded connections, which effectively limits potential leakage points.

5. Side Entry Ball Valves:

A side-entry ball valve is characterized by a ball that is installed from the side of the valve body. Typically, the body itself consists of two or three separate pieces, each joined together using screws or studs, much like connecting two flange sections.

These valves are usually fabricated from forged metal, which provides a certain reliability and durability in comparison to their cast counterparts.

After forging, each section of the body is assembled. This approach helps reduce the likelihood of defects that are more common in cast valves. The design not only streamlines the assembly process but also makes it easier to align internal components.

As a result, side-entry ball valves can generally be delivered more quickly, whereas cast valves often require more extensive testing before they are ready for use.

6. Welded Body Ball Valves:

A fully welded valve is designed without bolt connections, effectively eliminating potential leakage paths typically associated with bolts. Due to its construction, this type of valve is not suitable for on-site repair. Its primary use is in buried or underground environments where regular maintenance is neither practical nor preferred, such as in subsea operations or gas transportation systems.

When manufacturing these valves, all body welding processes must be compatible with the chosen construction materials. Each process is selected and executed according to established standards and criteria. Additionally, non-destructive testing (NDT) is required on all perimeter welds of the valve body to ensure the integrity of the joints.

Advantages of ball valves

• Efficiency: Ball valves stand out for their ability to create a bubble-tight seal without requiring any lubrication, all while operating with minimal torque.
• Affordability: In most cases, ball valves are available at a lower price point compared to alternative products designed for similar applications.
• Durability: These valves are known for their long service life. When used as intended, they consistently deliver reliable performance for years. Notably, ball valves are more resistant to damage than many other valve types, and plastic models, in particular, are immune to corrosion.
• Ease of Use: The installation process for ball valves is typically straightforward. Plastic ball valves, being lightweight, are especially easy to handle and fit.
• Versatility: Ball valves can be used in a broad range of industrial settings where managing the flow of liquids or gases is required.
• Strength: They are capable of withstanding and regulating high pressure, large volumes, and significant temperature variations.
• Simplicity of Repair: When maintenance is needed, the seats can be accessed without much hassle, making repairs a relatively uncomplicated process.

Disadvantages of ball valves

The main disadvantages of these valves are as follows:

• Throttling Limitations: When a valve operates in a throttling position, the seat is only partially exposed to the flow. This can lead to erosion over time, especially with high-velocity fluids moving across the exposed area. Because of this vulnerability, these valves are generally unsuitable for continuous throttling purposes.
• Susceptibility to Wear: Using ball valves with inappropriate fluids, such as slurries, often creates practical issues. Suspended particles can become trapped, causing the valve to stick or jam in place. Over time, this not only increases the likelihood of wear but also raises the risk of damage or complete malfunction.

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