Research On The Structural Characteristics And Working Principle Of Ball Valves Installed On Ear Shafts

In industrial settings, fluid control plays a vital role across countless production processes. Valves, as the central components for managing fluid flow, directly influence the stability and efficiency of industrial operations. Among important valve types, the trunnion-mounted ball valve sees widespread use in diverse sectors-including petroleum, chemical processing, natural gas, and power generation-thanks to its distinctive design and demonstrated reliability.

For example, in petroleum transmission pipelines, these valves provide quick and dependable fluid isolation or diversion, safeguarding pipeline integrity. Within chemical processing facilities, they allow precise control over chemical flow rates and direction, ensuring uninterrupted operations. Understanding the structural characteristics and working principles of trunnion-mounted ball valves is therefore highly valuable in practice. This knowledge supports appropriate valve selection, correct implementation, and design optimization for this category.

 

The ear shaft mounted ball valve is mainly composed of key components such as the ball, valve body, ear shaft and valve seat. The sphere is the opening and closing part of the valve, usually spherical in shape with a flow passage in the middle. The valve is opened and closed by rotating the sphere. The valve body is the outer shell of the valve, providing installation support and fluid passage for other components. The ear shaft is a distinctive component for installing ball valves on the ear shaft. It connects the ball and the valve body, serving to support and transmit motion. The valve seat works in conjunction with the ball to form a sealing pair, preventing fluid leakage.

 

(II)The connection and interaction between the ear shaft part and the ball and valve body

Connection Methods Between Trunnion and Sphere

Common connection methods between the trunnion and the sphere include welding and keyed connections. Welding offers advantages like high connection strength and excellent sealing performance, ensuring the trunnion and sphere become an integrated unit. This allows stable operation even under demanding conditions such as high pressure and high temperature. However, welding requires higher process standards. Stresses can concentrate during welding, and defects may occur. Once welded, disassembly and repair become difficult. Keyed connections, using keys to join the trunnion and sphere, provide convenient installation and disassembly, facilitating valve maintenance and inspection. The strength of keyed connections is relatively lower, however. Under significant loads, loosening may occur, potentially affecting normal valve operation. Consequently, welded connections suit applications demanding high valve reliability and sealing, where frequent disassembly is not required. Keyed connections are better suited for scenarios prioritizing installation and maintenance convenience.

Connection Form Between Trunnion and Valve Body

The trunnion is typically connected to the valve body via bearing supports. Bearings provide stable support for the trunnion, reducing rotational friction resistance. This ensures the sphere can rotate smoothly and flexibly within the valve body. This connection form also effectively bears the weight of the sphere and fluid forces, transferring these loads to the valve body. This prevents excessive deformation or damage to the trunnion under load. For example, in some large trunnion-mounted ball valves, the use of high-precision rolling bearings significantly reduces trunnion rotational resistance, enhancing valve operational performance.

Interaction Between Trunnion, Sphere, and Valve Body

During valve opening and closing, the trunnion plays a critical role in transmitting motion and bearing forces. When the actuator rotates the trunnion, it transmits this rotational motion to the sphere. The sphere then rotates around its axis, achieving valve opening or closure. Simultaneously, the trunnion must bear the sphere's weight and the forces exerted on the sphere by the fluid. Under fluid pressure, the sphere generates a thrust towards the closed position. This force transmits through the trunnion to the valve body. The trunnion must possess sufficient strength and rigidity to prevent deformation under load. This ensures the sphere rotates accurately to its predetermined position, achieving precise opening and closing.

 

(II) The influence of the ear shaft on the rotational movement and sealing performance of the ball

Influence on Sphere Rotation
The design parameters of the trunnion, such as its diameter and length, significantly impact the flexibility and smoothness of the sphere's rotation. A larger trunnion diameter increases the contact area with the bearing, enabling it to carry greater loads, while also increasing rotational resistance. An excessively long trunnion may cause significant wobble during rotation, compromising the smoothness of the sphere's movement; conversely, a trunnion that is too short may fail to provide adequate support for the sphere, reducing valve stability. Furthermore, the trunnion plays a crucial role in preventing sphere misalignment. Proper trunnion design and installation ensure the sphere remains correctly positioned throughout its rotation, preventing issues like inaccurate valve opening or compromised sealing due to misalignment.

Influence on Sealing Performance
The precision of the fit between the trunnion and the valve seat directly affects the seal integrity between the sphere and the seat. If the trunnion machining precision is insufficient, leading to dimensional deviations or excessive surface roughness, the sealing surfaces between the sphere and seat will exhibit poor contact, resulting in leakage. Under fluid pressure, the trunnion must maintain stable sealing performance. Fluctuations in fluid pressure may cause slight deformation of the trunnion, demanding sufficient strength and rigidity to resist these pressure effects and ensure sealing integrity remains unaffected. For instance, manufacturing trunnions from high-strength alloy materials and enhancing their mechanical properties through processes like heat treatment effectively improves trunnion stability under fluid pressure, preventing leakage.

 

(I) Transmission of Fluid Pressure Through the Trunnion Structure
During valve opening and closing, fluid pressure initially acts upon the sphere. As the sphere is connected to the trunnion, this fluid pressure is transmitted from the sphere to the trunnion. The trunnion then transfers this pressure to the valve body and other components. The trunnion structure facilitates the rational distribution and transmission of fluid pressure. For instance, leveraging the lever principle, it converts a smaller operating force into a larger opening or closing force, enabling easier valve operation. In certain high-pressure trunnion-mounted ball valves, specially designed trunnion structures effectively distribute fluid pressure more evenly, reducing the torque required for valve operation and enhancing its operability.

(II)Impact of Fluid Pressure on Overall Valve Operation
Changes in Operating Characteristics
The operating characteristics of trunnion-mounted ball valves change significantly under varying fluid pressures. As fluid pressure increases, the torque required to open and close the valve also increases. This occurs because higher fluid pressure exerts greater resistance against the sphere's rotation, demanding larger operating forces to overcome this resistance and rotate the sphere. For example, under low-pressure conditions, operators can easily manipulate the valve manually; whereas under high-pressure conditions, electric or pneumatic actuators may be necessary to provide sufficient operating force.

Dynamic Impact on Sealing Performance
Fluid pressure also dynamically affects the valve's sealing performance. When fluid pressure rises, the compressive force on the sealing interface between the sphere and the seat increases, potentially enhancing sealing performance. However, if the fluid pressure becomes excessive and surpasses the seat material's capacity, it may cause the seat to deform or become damaged, thereby compromising the seal. The trunnion structure must accommodate these fluid pressure variations. Through sound design and material selection, it ensures reliable sealing performance is maintained across different operating conditions. For instance, utilizing seat materials with good elasticity and corrosion resistance allows the seal to adapt to some extent to pressure fluctuations, maintaining stable sealing performance.

 

Trunnion-mounted ball valves feature a unique structural design. The connection methods and interaction mechanisms between the trunnion, sphere, and valve body – along with their influence on the sphere's rotational movement and sealing performance – demonstrate the sophisticated engineering of this valve type. Regarding operational principles, the trunnion structure plays a pivotal role in transmitting fluid pressure and governing overall valve operation. As the core component, the trunnion critically impacts valve performance by ensuring stable sphere rotation, precise opening/closing positioning, and maintaining reliable sealing integrity across diverse operating conditions.

With continuous advancements in industrial technology, performance requirements for trunnion-mounted ball valves continue to escalate. Future development will likely focus on achieving higher pressure ratings, larger bore sizes, and greater intelligence. Examples include adopting innovative materials and advanced manufacturing techniques to enhance trunnion strength and corrosion resistance, while integrating smart control technologies to enable real-time operational monitoring and remote control – thereby further improving valve reliability and operational convenience. Continuous research and refinement of trunnion-mounted ball valves will unlock new innovations and foster development opportunities within the industrial fluid control sector.