Views: 0 Author: J-VALVES Publish Time: 2025-02-21 Origin: Site
Understanding trunnion Ball Valves
Key Features of trunnion Ball Valves
1. trunnion Design: The trunnion design allows for the valve to be mounted on a vertical axis, providing stability and reducing the risk of misalignment. This design is particularly beneficial in high-pressure and high-temperature applications where precise alignment is crucial.
2. Robust Construction: trunnion ball valves are typically constructed from high-strength materials such as carbon steel, stainless steel, or alloy steel. These materials ensure the valve can withstand the mechanical stresses and corrosive environments common in the oil and gas industry.
3. Precision Sealing: These valves feature precision-machined metal seats and high-quality seal materials, such as PTFE or other fluoropolymers, to ensure minimal leakage and long-term durability.
4. Fire-Safe Design: Compliance with ISO 14313 ensures that trunnion ball valves are designed to be fire-safe. This feature is crucial for applications in hazardous environments, such as oil and gas pipelines, where the valve must remain functional even in the event of a fire.
• Valve Body: The main structure that houses the ball and other components. The body is typically made from high-strength steel to ensure durability and resistance to corrosion.
• Ball: The spherical element that controls the flow by rotating around its axis. The ball is often made from stainless steel or other corrosion-resistant materials.
• trunnion: The unique feature that allows the valve to be mounted on a vertical axis, providing stability and reducing the risk of misalignment.
• Seats: The sealing elements that provide a tight seal when the valve is closed. Seats are typically made from metal or high-performance polymers.
• Stem: The component that connects the ball to the actuator, allowing for rotation. The stem is designed to withstand high mechanical stresses.
• Actuator: The mechanism used to rotate the ball, which can be manual, electric, pneumatic, or hydraulic.
ISO 14313 Standard: Key Requirements
ISO 14313:2007 specifies requirements and provides recommendations for the design, manufacturing, testing, and documentation of ball, check, gate, and plug valves for application in pipeline systems meeting the requirements of ISO 13623 for the petroleum and natural gas industries. This standard is not applicable to subsea pipeline valves, which are covered by ISO 14723, or to valves for pressure ratings exceeding PN 420 (Class 2500).
• Material Selection: The standard outlines the choice of materials for different components of the valve, ensuring they can withstand harsh operating conditions. Common materials include carbon steel, stainless steel, and alloy steel.
• Mechanical Properties: Materials must meet specific mechanical properties, such as tensile strength and hardness, to ensure the valve can withstand operational stresses.
• Thermal Treatment: Some materials may require specific heat treatment processes to enhance their resistance to stress corrosion cracking (SCC).
• Pressure Testing: Valves must undergo rigorous pressure testing to verify their ability to withstand operating pressures.
• Leakage Testing: Advanced leakage testing methods, such as helium leak testing, are used to detect even the smallest leaks and ensure the valve's sealing integrity.
• Non-Destructive Testing (NDT): Techniques such as ultrasonic testing (UT) and radiographic testing (RT) are used to detect any defects or imperfections in the valve components.
Marking and Documentation
• Marking Requirements: Valves must be clearly marked with essential information, such as size, pressure rating, and material.
• Documentation: Detailed documentation must accompany the valves, including manufacturing records, test results, and certification.
Application in the Oil and Gas Industry
trunnion ball valves are extensively used in natural gas pipelines, particularly those containing hydrogen sulfide (H₂S) and other corrosive substances. The robust construction and precision sealing of these valves ensure reliable performance and minimal maintenance. Key considerations include:
• Material Selection: For natural gas pipelines containing H₂S, materials such as 316L stainless steel or alloy 625 are often specified due to their excellent resistance to SCC.
• Design Requirements: The design must ensure that all components, including the shell, bonnet, disc, and seat ring, are made from materials that can withstand the corrosive environment.
• Testing and Certification: Valves must be tested and certified to meet the requirements of ISO 14313, including specific tests for sulfur resistance.
In oil and gas processing plants, trunnion ball valves are used for their high strength and corrosion resistance. These valves are suitable for applications involving high pressures and temperatures, such as:
• Material Selection: Materials such as duplex stainless steel may be used for their high strength and corrosion resistance.
• Design Requirements: The design must account for the potential presence of corrosive substances, including H₂S, and ensure that all components are made from appropriate materials.
• Testing and Certification: Valves must undergo rigorous testing to ensure they meet the performance and safety standards specified by ISO 14313.
