Ball valve

The ball valve is a widely used fitting in industrial and technical process control that controls the flow of liquids, gases, or steam by means of a rotating ball. This type of valve offers a simple but extremely effective way to quickly and reliably open, close, or regulate the flow. Due to their compact design, tightness, and durability, ball valves are the first choice in many applications, especially when rapid shut-off or release of the medium is required.

Structure of a ball valve

The central element of a ball valve is the spherical closing unit (ball) located inside the valve body. The ball has a through-hole through which the medium can flow. Depending on the position of the ball inside the body, the flow is either released or shut off. The main components of a ball valve include:

• Housing: The housing encloses the ball and is usually made of materials such as stainless steel, brass, or other high-strength materials that must withstand the requirements of the respective application (e.g., corrosion, high temperatures, pressure).
• Ball: The ball itself is the central element and is usually made of stainless steel or other high-strength alloys. It has a bore (through-hole) that allows or blocks the medium from passing through the valve.
• Seals (seats): These are located on both sides of the ball and provide a tight seal to prevent leakage. They are usually made of plastics such as PTFE (Teflon) to seal the ball when it moves and at the same time ensure low friction.
• Spindle/drive: The spindle connects the ball to the actuating mechanism (e.g., hand lever or servomotor). A 90° rotation of the spindle moves the ball and opens or closes the flow.
• Actuator: Ball valves can be operated manually using a lever or automatically using pneumatic, electric, or hydraulic actuators. Manual levers provide quick visual control over the valve status (open/closed).

How a ball valve works

The ball valve operates by rotating the ball inside the valve body. When closed, the impervious side of the ball blocks the flow of the medium. When the ball is rotated 90°, the bore of the ball aligns with the pipe cross-section and opens the path for the medium.

An important feature of the ball valve is its rotary shut-off function. Since the ball rotates inside the valve, it is not an opening and closing movement, but a purely rotating mechanism. This results in less mechanical wear and better tightness compared to linear movements, such as those found in gate or diaphragm valves.

Ball valves can be designed for both full and partial flow. There are two basic types:

Full bore: The bore in the ball corresponds to the full pipe diameter. This design minimizes flow resistance, as the medium can flow unhindered through the valve, which reduces pressure loss in the system.
Reduced bore: Here, the bore is smaller than the pipe diameter, which creates a certain amount of flow resistance. This design is used in applications where full flow is not required.

Advantages and disadvantages of ball valves

Advantages:

1. Fast switching time: Ball valves can be opened or closed quickly by turning the actuator 90°.
2. Excellent tightness: The rotating movement of the ball ensures a tight seal, even at high pressures. Ball valves offer a virtually leak-free solution, especially for gases or volatile liquids.
3. Low pressure loss: Full-bore ball valves cause hardly any pressure loss, as the medium can flow through the valve almost unhindered.
4. Durability: Due to their simple design and low mechanical stress, ball valves are extremely durable and require little maintenance.
5. Robustness: Ball valves are resistant to corrosion, high temperatures, and aggressive media, making them suitable for a wide range of applications.

Disadvantages:

Limited controllability: Although ball valves are ideal for quick shut-offs, they are less suitable for finely tuned flow control because the control is not as precise as with other valve types such as the rotary cone valve or control valve.
Increased space requirements: Ball valves require more space than some other valve types because they require greater leverage to enable the 90° rotation.

Areas of application for ball valves

Ball valves are used in a wide range of industries and applications due to their robust design and their ability to effectively control both liquids and gases. Typical areas of application are:

• Water and wastewater treatment: Ball valves regulate the flow of water in supply and disposal systems.
• Oil and gas industry: They are used to control the transport of oil, gas, and other petrochemical products, as they provide a reliable seal even under extreme pressure and temperature conditions.
• Chemical industry: Ball valves are ideal for handling corrosive liquids and gases, which are often found in chemical processes.
• Food and beverage industry: They are often used here because they are easy to clean and can maintain sterile conditions.
• Pharmaceutical industry: Ball valves are used in sterile process environments because they are easy to clean and maintain.

Maintenance and service life

Ball valves are generally low-maintenance and have a long service life. The low mechanical wear caused by the rotating movement of the ball minimizes the wear and tear on seals and other components. Nevertheless, they should be checked regularly, especially in highly corrosive or abrasive environments, in order to detect leaks or malfunctions at an early stage. In the event of problems, the spindle or seal unit can be replaced relatively easily.

Summary

The ball valve is a reliable, robust, and versatile fitting that is used in numerous industries. Its ease of use, excellent tightness, and durability make it the preferred choice for applications where fast and safe shut-off or opening of the medium is essential. Whether in the oil and gas industry, water transport, or chemical processes, the ball valve meets the highest standards in terms of safety, efficiency, and ease of maintenance.