Trunnion mounted Ball Valve

1. What is Trunnion Mounted Ball Valve?

A Trunnion mounted Ball Valve is a robust flow control solution designed for high-pressure and large-diameter industrial piping systems. Unlike floating designs where the internal sphere is supported by the seats, this specific configuration utilizes a fixed ball mechanism supported by a top and bottom shaft (trunnion). This mechanical arrangement ensures that the sphere remains centered within the body, regardless of the upstream pressure, effectively transferring the hydraulic load to the valve body rather than the sealing seats. This design is particularly suitable for demanding services where operational reliability and seat longevity are critical.

As a core component of heavy-duty fluid automation, these rotary units are engineered to meet global industrial standards, including API 6D, ANSI, and GB. The architecture typically features a split-body or top-entry design, allowing for high structural integrity under extreme mechanical stress. Whether utilized in oil and gas transmission or high-pressure chemical processing, the trunnion-style architecture offers consistent performance and lower operating torque compared to floating alternatives. The equipment can be integrated with various drive systems, such as AT series pneumatic actuators or intelligent electric motors, to facilitate remote automated control.

2. How this Trunnion Rotary Device Works?

The operational principle of this equipment centers on a fixed-axis rotation that manages fluid flow through a ninety-degree turn of the internal sphere. Because the ball is anchored by trunnions, the sealing is achieved through a spring-loaded seat mechanism that moves against the stationary ball under the influence of line pressure.

The core operational stages include:

1. Opening Phase: When the actuator transmits torque through the high-strength stem (often made of 2Cr13 or similar alloys), the internal sphere pivots from a position perpendicular to the flow to one parallel to it. This transition allows the media to pass through the full-bore body with a high flow coefficient (Cv) and negligible pressure drop.
2. Closing and Sealing Phase: Upon receiving a signal to close, the sphere rotates ninety degrees back. The upstream pressure acts on the piston-effect seats, pushing them firmly against the sphere to ensure a bubble-tight seal. In high-performance models, a double block and bleed (DBB) function allows for the venting of the body cavity when the valve is in the closed position, providing an extra layer of safety.
3. Fire-Safe and Anti-Static Protection: The design incorporates secondary metal-to-metal sealing surfaces that activate if the soft seals are destroyed by high heat. Additionally, internal grounding springs ensure that any static electricity generated by the rotating sphere is safely discharged to the body and the pipeline.

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3. Types of Trunnion-style Control Units

3.1 Material Classification and Properties

To handle a wide range of industrial media and pressure classes (ranging from PN1.6 to PN42.0 MPa), these devices are manufactured from various high-performance metals:

• Carbon Steel Series: Utilizing WCB or A105 materials, these units provide excellent mechanical strength for general oil and gas services.
• Stainless Steel Series: Manufactured from alloys like CF8, CF8M, or 316L, these models offer superior corrosion resistance for aggressive chemical and offshore applications.
• Special Alloy Series: For extremely corrosive or high-temperature environments, units can be constructed with Duplex steel or Monel internals to ensure material integrity.

3.2 Sealing and Actuation Variants

• Resilient Seated: Features seats made of PTFE, RPTFE, or Devlon, providing excellent sealing performance for gas and clean liquid services at moderate temperatures.
• Metal Seated: Utilizes hardened metal surfaces for the ball and seats, often coated with Tungsten Carbide, to manage abrasive slurries or high-temperature steam.
• Automated Assemblies: These units are frequently equipped with heavy-duty pneumatic actuators (AT/BW series) or motorized electric actuators, allowing for precise isolation managed through 4-20mA signals or digital protocols.

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4. Core Advantages of the Trunnion System

The trunnion design provides several technical benefits that enhance the safety and efficiency of high-pressure industrial operations.

• Low Operating Torque: By supporting the weight of the ball on bearings, the friction between the ball and the seats is significantly reduced, allowing for the use of smaller and more cost-effective actuators.
• Automatic Pressure Relief: The spring-loaded seats are designed to automatically relieve excess pressure from the body cavity into the pipeline, preventing potential body damage due to thermal expansion.
• Independent Sealing: Both the upstream and downstream seats can seal independently, providing a reliable redundant barrier against leaks.

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5. Industrial Applications

The stability and high-pressure capability of the Trunnion mounted Ball Valve make it indispensable across multiple critical sectors:

1. Oil and Gas Transmission: These units are essential for long-distance pipelines and compressor stations where high-pressure isolation and reliable safety features like DBB are mandatory.
2. Petrochemical and Refining: In refining processes involving high temperatures and corrosive hydrocarbons, the trunnion-mounted units provide durable service with minimal maintenance requirements.
3. Power Generation: Metal-seated models are deployed in cooling water systems and high-pressure steam lines where mechanical reliability is necessary for plant safety and operational uptime.
4. Chemical Processing: Used for large-scale distribution of chemical reagents, these valves ensure zero-leakage performance and protect the environment from hazardous spills.