Ball valves are essential in industrial applications for controlling the flow of gases, liquids, and slurries through pipelines. Their simple design features a spherical ball with a central bore that allows or blocks flow with a 90-degree rotation, ensuring quick operation, reliable sealing, and minimal pressure drop. Widely used in industries like oil and gas, chemical processing, water treatment, and manufacturing, ball valves are valued for their durability, efficiency, and ability to handle high pressures and temperatures with low maintenance. This article will explore two main types—floating vs trunnion ball valves—highlighting their structural differences, operational mechanisms, advantages, and limitations to help in selecting the right valve for specific applications.

 

What is a Floating Ball Valve?

A floating ball valve is a type of quarter-turn valve commonly used to control the flow of liquids and gases in various industrial applications. It features a ball that is not fixed but “floats” within the valve body, allowing it to create a tight seal by pressing against the valve seats. ​

Definition and Basic Design

In a floating ball valve, the ball is suspended between two elastomeric seats without any mechanical anchoring, such as a trunnion. This design allows the ball to move slightly downstream under fluid pressure, pressing against the downstream seat to achieve a tight seal. The simplicity of this design makes floating ball valves suitable for a wide range of applications. ​

Working Mechanism

Floating Ball Valve Diagram

The operation of a floating ball valve involves a stem connected to the top of the ball. When the stem is rotated 90 degrees, it turns the ball, aligning or misaligning the bore (hole) in the ball with the flow path. In the closed position, fluid pressure pushes the ball against the downstream seat, enhancing the seal. This pressure-assisted sealing ensures reliable shut-off in both directions. ​

Key Features

• Compact Structure: The straightforward design results in a smaller valve body, making it ideal for installations where space is limited.​

• Cost-Effectiveness: With fewer components and simpler construction, floating ball valves are generally more affordable compared to other valve types.​

• Bidirectional Sealing: The floating ball design allows for effective sealing in both flow directions, providing versatility in various applications.​

Advantages and Limitations

Advantages:

• Reliable Sealing: The pressure-assisted mechanism ensures a tight seal, reducing the risk of leakage.​

• Ease of Operation: The quarter-turn action allows for quick opening and closing, facilitating efficient flow control.​

• Low Maintenance: The simple design with fewer moving parts leads to reduced maintenance requirements.

Limitations:

• Pressure Constraints: Floating ball valves are typically suitable for low to medium-pressure applications; at higher pressures, the unanchored ball can cause excessive wear on the seats.​

• Operational Torque: Higher operating torque may be required, especially in larger sizes or higher pressure scenarios, potentially necessitating the use of actuators.

 

What is a Trunnion Ball Valve?

A trunnion ball valve is a quarter-turn valve designed to control the flow of media through a pipeline. Unlike floating ball valves, which have a free-moving ball, trunnion ball valves feature a ball that is anchored by a trunnion—a fixed shaft at the bottom and sometimes at the top. This design provides enhanced stability and is particularly suitable for high-pressure applications. ​

Definition and Basic Design

In trunnion ball valves, the ball is fixed in position by the trunnion, preventing it from moving laterally under pressure. The valve seats are spring-loaded and can move slightly, pressing against the stationary ball to form a seal. This configuration ensures consistent sealing performance, especially in high-pressure environments. ​

Working Mechanism

trunnion ball valve diagram

The operation of a trunnion ball valve involves rotating the ball 90 degrees to open or close the flow passage. When in the closed position, the ball’s bore is perpendicular to the flow path, blocking fluid movement. Upon rotating the handle or actuator, the ball aligns its bore with the pipeline, allowing fluid to pass through. The fixed ball design reduces friction between the ball and seats, resulting in lower operating torque and enhanced durability. ​

Key Features

• High-Pressure Handling: The anchored ball design allows trunnion ball valves to withstand high-pressure conditions without compromising sealing integrity. ​

• Scalability: Trunnion ball valves are suitable for both small and large pipeline diameters, making them versatile across various industrial applications. ​

• Lower Operating Torque: The fixed ball mechanism reduces the torque required to operate the valve, facilitating smoother operation and the use of smaller actuators. ​

Advantages and Limitations

Advantages:

• Enhanced Sealing Performance: The trunnion-mounted design ensures effective sealing on both upstream and downstream sides, minimizing the risk of leaks. ​

• Durability: Reduced friction and wear between the ball and seats contribute to a longer service life, even under demanding conditions. ​

• Versatility: Suitable for a wide range of pressures and applications, including high-pressure systems where floating ball valves may not be ideal. ​

Limitations:

• Complexity and Cost: The intricate design and additional components, such as the trunnion and spring-loaded seats, make trunnion ball valves more expensive and complex compared to floating ball valves. ​

• Size and Weight: The robust construction results in larger and heavier valves, which may pose challenges in installations with space or weight constraints.

 

Key Differences Between Floating vs Trunnion Ball Valve

Understanding the distinctions between floating and trunnion ball valves is essential for selecting the appropriate valve for specific industrial applications. Below are the key differences:

Structural Design Comparison

• Floating Ball Valves: In these valves, the ball is not fixed and is held in place by two elastomeric seats. The ball is free to move slightly along the flow axis, allowing it to press against the downstream seat under fluid pressure, creating a tight seal. This design is simpler and typically used for smaller valve sizes. ​

• Trunnion Ball Valves: These valves feature a ball anchored by a trunnion—a fixed shaft at the bottom and sometimes at the top. This anchoring restricts the ball’s movement, providing stability and reducing the load on the seats. Trunnion-mounted designs are more complex and suitable for larger valve sizes and higher pressure applications. ​

Pressure and Temperature Handling Capabilities

• Floating Ball Valves: Best suited for low to medium-pressure applications, as the unanchored ball design can cause excessive wear on the seats under high-pressure conditions. They are generally not recommended for high-temperature environments due to potential seat material limitations. ​

• Trunnion Ball Valves: Designed to handle high-pressure and high-temperature applications effectively. The anchored ball reduces seat wear, making them more durable and reliable under extreme conditions. ​

Application Suitability

• Floating Ball Valves: Ideal for low to medium-pressure systems where cost-effectiveness and compact design are priorities. Commonly used in chemical processing, water treatment, and general industrial applications. ​

• Trunnion Ball Valves: Suitable for high-pressure systems and larger pipeline diameters. They are commonly used in oil and gas industries, petrochemical plants, and other applications requiring robust performance. ​

Cost Differences

• Floating Ball Valves: Generally more affordable due to their simpler design and fewer components, resulting in lower initial investment. ​

• Trunnion Ball Valves: More expensive upfront because of their complex design and additional components. However, their durability and suitability for high-pressure applications can offer better long-term value. ​

Maintenance and Durability

• Floating Ball Valves: Simpler design allows for easier maintenance, but they may require more frequent attention due to potential seat wear under higher pressures. ​

• Trunnion Ball Valves: More durable with less seat wear, leading to longer intervals between maintenance. However, when maintenance is required, it can be more complex and time-consuming due to the intricate design.

 

Applications: When to Use Each Type

Selecting the appropriate ball valve—floating or trunnion-mounted—is crucial for ensuring optimal performance, safety, and cost-effectiveness in various industrial applications. Below is an overview of the industries and systems best suited for each type:

Industries and Systems Best Suited for Floating Ball Valves

Floating ball valves are characterized by their simple design, cost-effectiveness, and reliable sealing capabilities, making them ideal for low to medium-pressure applications. They are commonly utilized in the following industries:​

• Water Treatment: Floating ball valves are extensively used in water treatment facilities for controlling water flow due to their reliable sealing and ease of operation. ​

• HVAC Systems: In heating, ventilation, and air conditioning systems, these valves regulate the flow of water and other fluids, ensuring efficient temperature control.​

• General Industrial Applications: Their versatility and cost-effectiveness make them suitable for various industrial processes requiring fluid control. ​

Industries and Systems Best Suited for Trunnion Ball Valves

Trunnion-mounted ball valves are designed to handle high-pressure and high-temperature applications, offering enhanced stability and reduced operating torque. They are particularly suitable for the following industries:​

• Oil and Gas: Trunnion-mounted ball valves are widely used in oil and gas industries, including gas feed lines, field gas plants, industrial gas processing plants, oil refinery feedstock lines, and crude oil plants. ​

• Pipeline Industries: The ability of trunnion-mounted ball valves to handle various applications such as gases, slurries, and liquids makes them highly valuable in the pipeline industry. ​

• Petrochemical Plants: These valves are suitable for numerous applications such as turbines, skids, generators, and compressors, which are integral to the operation of power industries.

 

How to Choose Between Floating vs Trunnion Ball Valve

Selecting the appropriate ball valve for your application is crucial to ensure optimal performance, safety, and cost-effectiveness. Below are key factors to consider when deciding between floating and trunnion ball valves:

Operating Pressure and Temperature

• Floating Ball Valves: These valves are suitable for low to medium-pressure applications. Their design relies on fluid pressure to press the ball against the downstream seat, creating a seal. However, at higher pressures, the unanchored ball can cause excessive wear on the seats, making them less ideal for high-pressure scenarios. 

• Trunnion Ball Valves: Designed to handle high-pressure environments, trunnion ball valves feature a fixed ball supported by trunnions, reducing stress on the seats and allowing for stable operation under high-pressure conditions. They are also better suited for high-temperature applications due to their robust construction. ​

Fluid Type (Corrosive, Abrasive, Gas/Liquid)

• Floating Ball Valves: Ideal for clean liquids and gases at lower pressures, such as water, light oils, or gas. They are commonly used in water systems, HVAC applications, and light industrial processes. ​

• Trunnion Ball Valves: More adaptable to various fluid types, including corrosive chemicals and slurries, as they offer better durability and sealing capabilities in harsh conditions. ​

System Size and Valve Diameter

• Floating Ball Valves: Typically used in smaller pipe sizes (up to 2-4 inches) and lower pressure systems. Their compact design makes them ideal for installations where space is limited. ​

• Trunnion Ball Valves: Suitable for larger pipeline diameters and high-pressure systems. They are commonly used in oil and gas industries, petrochemical plants, and other applications requiring robust performance. ​

Budget and Lifecycle Costs

• Floating Ball Valves: Generally more affordable due to their simpler design and fewer components, resulting in lower initial investment. ​

• Trunnion Ball Valves: More expensive upfront because of their complex design and additional components. However, their durability and suitability for high-pressure applications can offer better long-term value.

 

FAQs

1. Can floating ball valves handle high-pressure applications?

Floating ball valves are generally suitable for low to medium-pressure applications. In high-pressure scenarios, the unanchored ball can exert excessive force on the downstream seat, leading to potential seat damage and increased operating torque. Therefore, they are not typically recommended for high-pressure environments. ​

2. Are trunnion ball valves more expensive?

Yes, trunnion ball valves are typically more expensive than floating ball valves. This higher cost is due to their more complex design, which includes additional components like the trunnion anchoring system. However, their ability to handle higher pressures and larger pipeline diameters can offer better long-term value in demanding applications. ​

3. Which valve type offers better sealing performance?

Both floating and trunnion ball valves provide effective sealing, but their performance varies based on application conditions. Floating ball valves rely on fluid pressure to press the ball against the downstream seat, ensuring a tight seal in low to medium-pressure systems. Trunnion ball valves, with their anchored ball design, maintain consistent sealing under high-pressure conditions and reduce seat wear, offering enhanced sealing performance in such environments. ​

4. How do maintenance requirements differ?

Floating ball valves have a simpler design with fewer components, making them easier to maintain and suitable for applications where ease of maintenance is a priority. However, they may require more frequent maintenance due to potential seat wear under higher pressures. Trunnion ball valves, while more complex and potentially requiring more involved maintenance procedures, generally experience less seat wear and can offer longer maintenance intervals, especially in high-pressure applications.

 

Conclusion

The main differences between floating ball valve vs trunnion ball valve lie in their internal design, sealing mechanisms, pressure handling capacity, and suitability for different applications. Floating ball valves are more suited for smaller sizes and medium to low-pressure systems, offering a simpler design with fewer components. On the other hand, trunnion ball valves excel in high-pressure, large-diameter systems, providing superior stability, long-lasting performance, and the ability to handle more demanding conditions. Each type has its unique advantages, making them suitable for specific operational needs and industries. Contact our experts today for personalized advice, or explore our extensive selection of ball valves to find the perfect solution for your application.