What is Ball Valve?
In order to control liquid flow, a ball valve uses a hollow, perforated, and pivoting ball. The valve is open when the hole in the ball is parallel to the flow inlet; when it is rotated 90 degrees by the handle, it shuts off the flow. It is aligned flat with the flow when it is open and perpendicular to it when it is closed, making it easy to confirm the valve’s status visually. Closed position 1/4 turn can be either clockwise or counterclockwise.
Easy operation, ease of maintenance, and versatility of the ball valve make it ideal for numerous industrial applications. It can support pressures of 1,000 bar (15,000 psi) and temperatures of 752 °F (400 °C), depending on materials and design. Sizes are typically between 0.2 and 48 inches (5.1 and 1,219.2 mm). Metal, plastic, or metal with ceramic valve bodies are common; floating balls are usually chrome-plated for durability.
Ball valves have a high rate of durability, displaying good performance after many cycles, and are reliable, closing securely even after extended periods of disuse. Due to these characteristics, they are frequently chosen over gates and globe valves for shutoff and control applications but are not sufficiently precise for throttling applications.
Working Principle of a Ball Valve
In order to understand how a ball valve works, it is beneficial to understand the five main parts.
Components of a Ball Valve
The ball valve is made up of a valve body that is mounted on a large ball with a center hole diameter equal to the pipe inside diameter. The following figure shows the five main components of a ball valve.
The valve stem and ball are connected and can be either operated manually or automatically (electrically or pneumatically). By the ball valve seat and the O-rings around the valve stem, the ball valve is supported and sealed. The valves are all located within the valve housing. Through the ball is a bore. When the stem of the valve is turned a quarter-turn, the bore becomes open, thereby allowing the fluid to flow through or closed, thereby preventing it from going through. The ball valve’s operation is influenced by the circuit function, the housing assembly, the ball design, and the operation type.
Function of a Ball Valve
Using a ball valve, a liquid or gas flow is controlled by a rotating ball that features a bore. A quarter-turn (90 degrees) around the axis allows the medium to flow through or can block it. The valves have a long service life and provide reliable sealing throughout their lifespan, even if it is not used for a long time.
Therefore, they are preferred over the gate valve, for example, as a shutoff valve. Also, they offer superior resistance against contaminated media than most other valve types. A ball valve can also be used as a control valve in some modifications. Because of the limited accuracy of the flow rate control compared to other control valve types, this application is less common. However, there are some benefits to using the valve. It still provides a reliable seal, even if the media is dirty.
Usage of Ball Valves
An oil or gas engineer knows the importance of ball valves in piping systems. They serve various purposes in the oil and gas industry. For example, oil flow is controlled by them in upstream applications. By controlling gas and oil flow, they protect the equipment used in the midstream. Their downstream use is in refining crude oil.
Common Applications of Ball Valves
You can choose from a wide variety of ball valve types and configurations to suit your needs.
- Various fluid services can be managed using ball valves, including on/off stop-valves and bubble-tight shut-off.
- In onshore and offshore upstream oil and gas production facilities, ball valves are the most used fluid shutoff valves.
- Besides hydrocarbon systems, ball valves are equally suited to gaseous, vapor, and air systems.
- Through instrument tubing, ball valves are useful for connecting instruments.
- On fire-truck water delivery parts of the pump, foam systems, and fire-extinguishing systems, as well as in situations where quick action is necessary to open the flow, ball valves are typically found. A ball valve can also be used when two or three valves need to be opened and closed simultaneously.
- Applications with high-temperature and high-pressure conditions can benefit from metal-seated ball valves.
- It’s possible to open and close ball valves quickly, with bubble-tight seals even under high pressure.
Material of Ball Valves
- Stainless steel
The seats and seals used in ball valves also come in many types. Chemical compatibility, pressures, and temperatures determine which applications each are good for. These are some of the materials:
- TMF (valve seat)
- Reinforced Teflon (RTFE)
- Kel F (PCTFE)
- Virgin Teflon (TFE)
- UHMW Polyethylene (UHMWPE)
Advantages of Ball Valves
Benefits of ball valves include:
- Using ball valves is easy and cost-effective.
- Ball valves ensure leak-proof service.
- A ball valve opens and closes quickly.
- Ball valves are much smaller than gate valves.
- Ball valves are lighter than gate valves.
- The flow resistance of a ball valve is very low in the fully open position, as compared to that of a gate valve.
- Gate or globe valves do not offer the multi-design flexibility of ball valves, so they require fewer valves.
- Variations in the size and shape of ball valves provide a wide range of options.
- Ball valves of high quality provide safe service in high temperature and high-pressure applications.
- Ball valves require less force to operate than other valves.
- Ball valves do not require lubrication.
Disadvantages of Ball Valves
Ball valves also have some drawbacks, including:
- The ball valve handle position is rotated.
- Throttling cannot be accomplished with ball valves.
- An upright installation is recommended for ball valves with drive mechanisms.
- In closed positions, ball valves trap water in the center cavity when they regulate water flow. When temperatures fall below freezing point, the sides are susceptible to cracking due to ice formation.
- Ball valves are prone to water hammer or surge pressure since they open and close so quickly.
- As the ball moves across the seats with a wiping motion, abrasive solids suspended in the fluid flow may corrode the seats.
It is usually possible to prevent damage in this situation by using insulation and heat tape. Freeze-tolerant ball valves are another alternative in cold climates. It features a freeze plug in the side, which ruptures if the valve freezes up, serving as a ‘sacrificial’ fail point, leading to an easier repair. A new freeze plug can be installed instead of replacing the valve entirely.
FAQ about Ball Valve
- What is ball valve used for?
Using a ball valve, the flow of fluid is controlled by a metal ball that is sandwiched between two seats and contains a hole drilled through its center. Gas and vapors can be controlled by ball valves in hydrocarbon processes and are especially useful in low-flow situations.
- What are advantages of ball valves?
The benefits of ball valves include durability, low cost, shut-off capability, and optimal performance under high accuracy and control demands.
- How long does a ball valve last?
In general, ball valves last 8 to 10 years. This device has enormous value to the gas and water industries despite its simplicity.