What Is The Trunnion in A Ball Valve?

In a ball valves, the trunnion is a fixed shaft that supports the rotation of the ball. It is usually located at the top and bottom of the sphere, and its core function is to hold the sphere in place to ensure that the valve operates steadily under high pressure and large diameter conditions, while reducing operating torque and improving sealing performance. Here are some details:
I. Structure and functioning of the central nervous system
Position of the fixed sphere: The The trunnion Position is fixed by the top valve stem and bottom stem stem (support shaft) to prevent displacement under fluid pressure. Unlike floating ball valves, floating ball valves are only supported by seats on either side, a design that makes trunnion ball valves more suitable for high-pressure environments.
* Distributed fluid pressure: Under high pressure conditions, fluid pressure is applied to the ball. The shaft shifts the spherical load from the valve seat to its own structure, preventing valve seat from being worn down by excessive compression, while also reducing the lateral force of the valve stem and extending valve life.
• Reduced Reduced Operating Torque: The amount of torque required to rotate the sphere is greatly reduced by attaching the ear mark to the sphere. For example, in a 600-class high-pressure natural gas pipelines, the trunnion design can reduce the size of the actuator by more than 30%, reducing energy consumption and costs.
ii. Core Advantages of Trunnion Ball Valves
**High Pressure Large Diameter Adaptability:** Trunnion ball valves can withstand pressure up to Class 600 (approximately 10 MPa) and is suitable for pipes up to 60 inches (1524 mm) in diameter.
* * **Bidirectional Sealing Capability:** Axle ball valves are designed with spring or floating seats and are leak-free in both directions. Even if the medium flows in from any direction, the seat still presses against the sphere to ensure a reliable seal.
* **Double Seat Exsanguination:** The upper and lower seats of the interceptor ball valve float independently. Combined with the valve body drain connection, the following functions can be achieved:
Two-way seal: Two-way seal, can reduce pressure inside the cavity, prevent dielectric thermal expansion caused valve damage.
DIB (Double Isolation and Exsanguination): Provides double isolation to reduce downstream leakage risk and is suitable for high-risk media such as sand-containing liquids.
Anti-Flyout Structure: Some trunnion ball valves incorporate an anti-flyout structure (such as a retaining ring or pin) in the valve stem design to prevent the valve stem or ball from being ejected from the valve body under high pressure or abnormal operating conditions, ensuring operational safety.
III. Typical Application Scenarios of Trunnion Ball Valves
Oil and Gas Industry: Long Pipeline: First, last and interconnecting lines for gas stations, able to withstand high pressure differentials and unclean media (sand gas, etc.).
Refining Units: Ensure safe dielectric cutting during high pressure shutoffs and ensure the location of key valves at the top/bottom of towers and torch/ventilation systems.
Chemical industry: When dealing with corrosive media such as acid and alkali, trunnion ball valves has a corrosion resistant seat and wrought steel body to meet the requirements of harsh working conditions.
Power industry: used for gas generation and combined cycle power plant gas supply piping system, high temperature, high pressure steam or gas shock resistance.
Cryogenic Operating Conditions
Cryogenic trunnion ball valves (such as those used in liquefied natural gas applications) are designed with special materials and seals to maintain sealing performance of -196°C and prevent brittle breakage.
IV. INTRODUCTION INTRODUCTION INTRODUCTION Key Selection Considerations
Pressure and Temperature Matching
valve model are selected according to the maximum working pressure and temperature of the pipe to ensure that body material ((e.g., A105, F316L) and sealing material (e.g. metal seal, graphite seal) are suitable for operating conditions.
Media Characteristics
For corrosive media (e.g. seawater, chemical materials), corrosion resistant valve seats and hard-faced welded balls should be selected; for particulate media (e.g. coal powder, pulp), a scratch seal structure should be used to prevent leakage.
Actuator Type
Select electric, pneumatic, or hydraulic actuators according to automation requirements. The low torque characteristics of trunnion ball valves allow the use of smaller actuators, reducing costs.
Accreditation and standards
Priority is given to valves that meet international standards such as API 6D and ISO 14313 to ensure that they pass fire, static and blowout prevention safety tests.