What are Trunnion Ball Valves

Ball valves are essential components in industrial fluid control systems, renowned for their durability and reliability. They utilize a hollow, perforated, and pivoting ball to regulate fluid flow, offering quick and precise control. These valves are widely used across various industries, including chemical processing, oil and gas, power generation, and water treatment, due to their robust performance and ease of operation.

Definition and Basic Structure

A trunnion ball valve is a quarter-turn valve designed to control fluid flow within pipelines. Unlike traditional floating ball valves, the ball in a trunnion ball valve is fixed at both the top and bottom by trunnions, which are shafts that anchor the ball securely. This design ensures the ball remains stationary, allowing the seats to move slightly to form a seal, thereby reducing the operating torque required to open and close the valve.

◇ Design

Tanggong ball valves are engineered and manufactured for exceptional service life and reliability under demanding thermal and mechanical conditions. All ball valves are of full bore design and fully comply with the technical requirements of API 608, API 6D, and BS 5351 standards. Additionally, they are designed in accordance with ASME B16.34. The valve assembly consists of a precision-machined body, bonnet, and internal trim components.

◇ Range of Materials

The standard body and bonnet materials include nine grades of carbon steel, low alloy steel, and stainless steel. For specialized applications, valves can also be supplied in alternative grades of alloy and stainless steels. A comprehensive selection of trim materials is available to accommodate diverse service conditions. Optional packing and gasket materials are also offered to ensure compatibility with a wide range of media and operating environments.

◇ Available Modifications for Trademark Cast Steel Valves

• Trim modifications

• End connection customization

• Packing and gasket changes

• Operator mounting options

• Handwheel extensions

• Pressure equalization systems

• Anti-static design (AS) or Fire-safe (FD) configurations

• Customer-specific coatings

• Welded end bore alterations

• Oxygen and chlorine cleaning & specialized packaging

Detailed Features

1. Operating
Extended lever design allows easier manual operation. Optional actuators include gear, electric, pneumatic, and hydraulic types for demanding environments.

2. Body & Bonnet
For sizes below 12″, split or 3-piece body and bonnet structures are adopted to facilitate disassembly, inspection, and replacement of internal parts.

3. Bore
Available in Full Bore and Reduced Bore types. Full bore ensures minimal flow resistance and high flow capacity.

4. End Connections
Options include flanged (RF, RTJ), butt weld, and other types to support installation flexibility and piping system integration.

5. Packing
Standard packing uses multi-V PTFE design with live-loading for reliable sealing under frequent cycling and harsh conditions. Graphite packing is available for high-temperature services.

6. AS – Anti-Static Design
A metallic contact is always maintained between the ball, stem, and body to discharge static electricity during operation, preventing buildup.

7. DDB – Double Block and Bleed
Provides cavity isolation when the valve is in fully open or closed position. Trapped media can be safely bled off to prevent overpressure.

8. FD – Fire-Safe Design
Compliant with API 607 or BS 6755 standards. A secondary metal-to-metal seal ensures shut-off if primary soft seals are destroyed in a fire. Valves include graphite packing and gaskets to meet fire-safe requirements.

Trunnion vs. Floating Ball Valves: Key Differences

• Ball Support: In floating ball valves, the ball is not fixed and relies on fluid pressure to press against the downstream seat to form a seal. In contrast, trunnion ball valves have a fixed ball supported by trunnions at both ends, allowing the seats to move slightly to maintain a seal.

• Pressure Handling: Trunnion ball valves are designed to handle higher pressures more effectively than floating ball valves, making them suitable for high-pressure applications.

• Operating Torque: Due to the fixed ball design, trunnion ball valves require less operating torque compared to floating ball valves, leading to easier operation and reduced wear on components.

• Size and Application: Floating ball valves are typically used in smaller sizes and lower pressure applications, while trunnion ball valves are preferred for larger sizes and higher pressure scenarios.

How Do Trunnion Ball Valves Work?

Mechanism of Operation

Trunnion ball valves are quarter-turn valves that regulate fluid flow through a pipeline by rotating a spherical ball with a central bore. When the valve is open, the bore aligns with the pipeline, allowing fluid to pass through. Conversely, rotating the ball 90 degrees closes the valve, blocking the flow. This straightforward operation ensures quick and reliable control over fluid movement.

Role of the Trunnion in Stabilizing the Ball

In trunnion ball valves, the ball is supported at both the top and bottom by trunnions—mechanical shafts that anchor the ball securely within the valve body. This dual support system enhances the valve’s stability, especially under high-pressure conditions, and reduces the operating torque required to open and close the valve. By minimizing friction and wear, the trunnion design contributes to the valve’s durability and reliable performance.

Types of Trunnion Ball Valves

Trunnion ball valves are essential components in fluid control systems, designed to handle high-pressure and high-temperature applications. Their design and material selection are crucial for ensuring optimal performance and longevity. Below is an overview of the different types of trunnion ball valves based on design, material, and application.

Based on Design: 

• Split-Body Design: This design features a valve body divided into two or more pieces, allowing for easier maintenance and inspection. The trunnion ball is supported within the body, and the valve can be disassembled without removing it from the pipeline. This design is advantageous for valves that require frequent maintenance or inspection.

• Top-Entry Design: In this configuration, the valve body is accessed from the top, facilitating the removal and replacement of internal components without disturbing the valve’s position in the pipeline. This design is beneficial for applications where space constraints make side-entry designs impractical.

Based on Material: 

• Stainless Steel: Known for its excellent corrosion resistance, stainless steel trunnion ball valves are ideal for applications involving corrosive fluids or environments. They maintain structural integrity and performance over extended periods.

• Carbon Steel: Carbon steel valves offer strength and durability at a more cost-effective price point. They are suitable for general-purpose applications but may require additional coatings or linings to prevent corrosion in certain environments.

• Alloy Steel: Alloy steel valves are engineered to withstand extreme conditions, including high temperatures and pressures. They are often used in specialized applications where standard materials may not suffice.

Based on Application: 

• High-Pressure Applications: Trunnion ball valves designed for high-pressure applications are built to handle elevated pressures without compromising performance. They are commonly used in industries such as oil and gas, where pressure control is critical.

• Cryogenic Applications: Valves used in cryogenic applications are constructed to operate effectively at extremely low temperatures. They are essential in industries dealing with liquefied gases, ensuring reliable performance in freezing conditions.

• Corrosive Environments: For applications involving corrosive substances, trunnion ball valves are made from materials resistant to chemical attack, such as stainless steel or alloy steels. This ensures longevity and reliability in harsh chemical processing environments.

Key Advantages of Trunnion Ball Valves

Trunnion ball valves are integral to fluid control systems, offering several advantages that enhance their performance and reliability across various industrial applications.

1. Superior Performance in High-Pressure Systems

The trunnion design, which secures the ball at both the top and bottom, enables these valves to handle significantly higher pressures compared to floating ball valves. This robust construction ensures a reliable seal even under extreme pressure conditions, making trunnion ball valves ideal for demanding applications in industries such as oil and gas, petrochemicals, and power generation.

2. Reduced Operating Torque and Wear

By anchoring the ball with trunnions, the valve experiences less friction during operation. This reduction in friction leads to lower operating torque, facilitating easier valve actuation and reducing the strain on actuators. Consequently, this design minimizes wear and tear on internal components, extending the valve’s service life and reducing maintenance requirements.

3. Enhanced Sealing Reliability

Trunnion ball valves are equipped with spring-loaded seats that maintain consistent pressure against the ball, ensuring a tight seal. This feature enhances sealing reliability, preventing leaks and ensuring the integrity of the fluid control system. The ability to maintain a secure seal under varying pressure conditions is particularly beneficial in applications where leak prevention is critical.

4. Longevity in Harsh Environments

Constructed from durable materials and featuring a design that reduces internal stresses, trunnion ball valves are well-suited for harsh environments. Their ability to withstand high pressures, temperatures, and corrosive substances contributes to their longevity and reliability in demanding industrial settings. This durability ensures consistent performance over extended periods, even in challenging operating conditions.

Common Applications of Trunnion Ball Valves

Trunnion ball valves are integral to fluid control systems across various industries, offering precise regulation and secure sealing in demanding environments. Below are some of the primary applications:

1. Oil and Gas Pipelines

In the oil and gas sector, trunnion ball valves are essential for managing the flow of crude oil, natural gas, and refined products through pipelines. Their robust design enables them to withstand high pressures and temperatures, ensuring safe and efficient transportation of hydrocarbons over long distances. These valves are commonly used in gas feed lines, field gas plants, industrial gas processing plants, oil refinery feedstock lines, and crude oil plants.

2. Petrochemical and Refining Industries

Within petrochemical plants and refineries, trunnion ball valves play a crucial role in controlling the flow of various chemicals and hydrocarbons during processing. Their ability to handle high-pressure and high-temperature conditions makes them suitable for applications such as cracking, reforming, and distillation processes. The valves’ durability and reliable sealing are vital for maintaining safety and efficiency in these complex operations.

3. Power Generation and Water Treatment Plants

Trunnion ball valves are utilized in power generation facilities to regulate the flow of steam, water, and other fluids within boiler systems, cooling circuits, and steam turbine control systems. Their capacity to manage high-pressure and high-temperature fluids ensures the efficient operation of power plants. Similarly, in water treatment plants, these valves control the flow of water and chemicals during various treatment processes, contributing to the production of clean and safe water.

How to Choose the Right Trunnion Ball Valve

Selecting the appropriate trunnion ball valve is crucial for ensuring optimal performance, safety, and longevity in fluid control systems. Consider the following factors and industry standards when making your choice:

1. Factors to Consider

• Pressure Rating: Ensure the valve’s pressure rating aligns with your system’s operating pressures. Trunnion ball valves are designed to handle high-pressure applications, making them suitable for industries like oil and gas, petrochemical, and power generation.

• Temperature: Select a valve that can withstand the operating temperatures of your system. Trunnion ball valves are available in materials and designs that accommodate both high and low-temperature environments.

• Fluid Type: Consider the chemical compatibility of the valve materials with the fluids in your system. Trunnion ball valves are suitable for handling a wide range of fluids, including corrosive and abrasive substances.

2. Industry Standards and Certifications

• API 6D: This standard specifies requirements for pipeline valves, including trunnion ball valves, ensuring they meet performance and testing criteria for pipeline applications.

• ASME B16.34: This standard covers valves for use in pressure systems, providing guidelines on design, materials, and testing to ensure valve integrity and performance.

• API 607: This standard outlines fire test requirements for valves, ensuring they maintain functionality and integrity under fire conditions.

• ISO 9001: This certification indicates that the valve manufacturer adheres to quality management systems, ensuring consistent product quality.

Conclusion

Trunnion ball valves play a critical role in industrial systems by providing reliable fluid control in high-pressure, high-temperature, and corrosive environments. Their unique design ensures superior performance, reduced operating torque, enhanced sealing reliability, and longevity, making them essential for industries such as oil and gas, petrochemical, and power generation. With various types available based on design, material, and application, selecting the right valve is crucial for optimal system performance. We invite you to explore our product catalog and discover the perfect trunnion ball valve solutions for your specific needs.