ASME 2-Piece Trunnion Ball Valve Q347F

Practical Functions

Ball valves are primarily utilized in piping systems to shut off, divert, and redirect the flow direction of process media. As an innovative valve type widely popularized in recent years, ball valves feature distinct advantages as follows:

1. Extremely low flow resistance, with its drag coefficient equivalent to that of an equal-length straight pipe.

2. Simple structure, compact overall dimensions, and lightweight design.

3. Dependable sealing performance. The sealing contact surfaces adopt plastic materials with excellent sealing capability, and are also extensively deployed in vacuum system applications.

4. Effortless operation and rapid switching. Only a 90° rotation is required to cycle between fully open and fully closed positions, ideal for remote automated control.

5. Easy maintenance. The valve structure is simplistic, and the sealing rings are generally replaceable movable components, greatly simplifying disassembly and replacement work.

6. At full open or full closed position, the sealing faces of the ball and valve seat are completely isolated from the conveyed medium, preventing erosion and wear on the valve sealing surfaces during medium passage.

7. Wide service applicability. Available sizes range from tiny diameters of several millimeters up to large bores of several meters, suitable for conditions from high vacuum to ultra-high pressure.

Ball valves are currently widely applied in industries including petroleum, chemical engineering, power generation, papermaking, atomic energy, aerospace, rocket manufacturing, as well as general civil daily-use fields.

Main Classification

By Structural Form

1. Floating Ball Valve

The ball body of this valve design is unconstrained (floating). Under the action of medium pressure, the ball generates positional displacement and presses firmly against the outlet-side sealing surface, achieving tight sealing at the outlet end.

Floating ball valves boast a simple structure and excellent sealing performance. However, the full medium pressure load acting on the ball is entirely transferred to the outlet sealing ring. Therefore, it is critical to confirm that the sealing material can withstand the operational pressure load from the conveyed medium. This construction is widely used for low-pressure and medium-pressure service.

2. Trunnion Mounted (Fixed) Ball Valve

The ball body of this valve is mechanically fixed and will not deform or shift under pressure. All fixed ball valves are fitted with floating seats. When subjected to medium pressure, the valve seat moves axially, compressing the sealing ring tightly onto the ball surface to achieve positive sealing. Typically, upper and lower support trunnion shafts are installed on the ball body, which greatly reduces operating torque, making this design ideal for high-pressure and large-diameter valves.

To further enhance operational flexibility and sealing reliability, oil-lubricated sealing ball valves have been developed in recent generations. Specially formulated sealing grease is injected between the mating sealing surfaces to form a durable oil film. This design not only strengthens sealing integrity, but also lowers required operating torque, making it even more suitable for extra-large diameter ball valve specifications.

3. Elastic Ball Valve

The ball body of an elastic ball valve is designed with built-in elasticity. Both the ball body and valve seat sealing ring are manufactured from metallic materials, requiring extremely high specific sealing pressure. Reliable sealing cannot be achieved relying solely on medium pressure alone, so additional external compressive force must be applied. This valve variant is engineered for high-temperature and high-pressure operating conditions.

An elastic compliant groove is machined at the bottom of the ball body to achieve elastic preload. During valve closing, the wedge-shaped end of the valve stem presses the ball body firmly against the valve seat to establish a tight seal. When the ball is rotated to open the valve, the ball rebounds slightly to its original geometry, creating a minimal clearance between the ball and seat. This design effectively reduces sealing surface friction and operating torque.

Port Configuration Classification

Ball valves are categorized by channel layout into straight-way, three-way and right-angle types. The latter two categories are used to divert medium and alter fluid flow direction.

Other Classifications

Ball valves are available in O-ball valve and V-ball valve types.

- O-type ball valve: Adopts floating ball design. The ball body is precision cast with hardened surface treatment; the valve seat is made of reinforced PTFE material. Its flow bore matches the pipe nominal diameter, offering extremely large flow capacity and minimal flow resistance. It achieves zero leakage when closed, primarily used as an on/off valve. It is especially suitable for high-viscosity, fibrous and granular media.

- V-type ball valve: Features fixed ball structure. A V-shaped notch is machined on the ball body to realize proportional regulation, with flow characteristics approximating an equal percentage curve.

Based on actuation requirements, ball valves can be equipped with pneumatic or electric actuators, forming pneumatic ball valves and electric ball valves respectively.

- For proportional regulation of pneumatic ball valves: A valve positioner must be installed.

- For proportional regulation of electric ball valves: An electric actuator or servo amplifier is required.

By material: Carbon steel ball valves, 304 stainless steel ball valves, 316 stainless steel ball valves and bronze ball valves.

By application pressure grade: High-pressure ball valves and low-pressure ball valves.

- High-pressure ball valves: Mainly applied in petroleum, natural gas, hydraulic system, engineering machinery and other industries.

- Low-pressure ball valves: Primarily used in non-corrosive medium pipelines such as water service.