The Basic Structure of Carbon Steel Floating Ball Valve

A Carbon Steel Floating Ball Valve is a quarter-turn valve that uses a hollow, perforated, and floating ball to control the flow of media through a pipeline. Its structure is relatively simple, which contributes to its widespread use in low to medium pressure systems.

The valve body of a carbon steel floating ball valve is typically made from ASTM A216 WCB (cast carbon steel), which provides good mechanical strength, temperature resistance, and corrosion resistance when coated appropriately. The valve body is usually made in two or three pieces (split body or three-piece design), allowing for easier maintenance.

The key component in this valve type is the floating ball, which is not fixed to the stem but rather held in place by compression from the seats. When the valve is closed, the pressure of the fluid forces the ball against the downstream seat, forming a tight seal. This design is effective for small to medium diameters and low to moderate pressures, as it depends on fluid pressure to achieve sealing.

The seats are often made of soft materials such as PTFE (polytetrafluoroethylene), which provide reliable sealing and are resistant to corrosion. The design ensures a tight shut-off, making it suitable for applications where leakage control is essential.

The stem connects the actuator or handle to the floating ball and is typically equipped with a sealing system consisting of packing rings and O-rings. This prevents leakage along the stem and ensures operational safety. Anti-blowout stem designs are standard in carbon steel valves for added safety.

The Cast Steel Trunnion Ball Valve is designed for higher pressure applications and larger pipe sizes. It offers enhanced stability, lower operating torque, and improved sealing performance, making it well-suited for complex industrial processes.

Constructed from cast steel, such as ASTM A216 WCB or other alloy variants depending on service conditions, the valve body provides a robust frame for high-pressure operations. Unlike the floating design, the trunnion-mounted ball is supported by bearings at the top and bottom. This fixed position prevents the ball from shifting under pressure, making it more stable in high-pressure flow systems.

One of the defining features of the trunnion valve is its dual-seat design, which is spring-loaded or pressure-activated to maintain sealing integrity on both sides of the ball. This feature ensures effective sealing regardless of the direction of flow or pressure. Soft seat materials like PTFE are common, though metal seats are used for high-temperature or abrasive media.

The cast steel trunnion ball valve typically includes a gear operator or an actuator (pneumatic or electric) to rotate the ball. Since the ball is supported by trunnions, it requires less torque to operate compared to a floating ball valve. This makes automation more efficient and reliable in larger diameter pipelines.

The stem is equipped with multiple seals and is often anti-blowout in design to improve safety. The use of fire-safe and anti-static components is standard in designs to meet industry regulations.

The cast steel trunnion ball valve is preferred in oil and gas pipelines, power generation, petrochemical industries, and refineries. It is suitable for both onshore and offshore applications, especially where high integrity and long-term sealing performance are required under pressure conditions.

Understanding the structure and working principles of both valve types helps ensure proper selection, which is critical for optimizing system performance, safety, and long-term operational reliability in various industrial settings.