Multi-directional Control and Sealing Technology of Three-way Ball Valves

I. Working Principle and Multi-directional Control of Three-way Ball Valve

1. Basic Structure and Working Principle

L-type flow channel: AnL-type three-way ball valvehas two outlets, allowing fluid to flow from one inlet to either of the two outlets. This design is mainly used for flow path switching, suitable for scenarios where fluid needs to be switched between two pipelines.

T-type flow channel: AT-type three-way ball valvehas three through-holes, enabling fluid switching among three directions. This design is suitable for confluence or diversion needs, capable of connecting three pipelines simultaneously.

2. Principle of Multi-directional Control

Opening process:

1. In the closed position, the ball is tightly pressed against the valve seat by the mechanical pressure of the stem, sealing the flow channel.

2. When the handwheel or actuator is rotated counterclockwise, the stem moves in the opposite direction, and its bottom angular plane disengages the ball from the valve seat.

3. The stem continues to lift, and the ball starts to rotate without friction until it reaches the fully open position.

Closing process:

1. Rotating the handwheel or actuator clockwise, the stem begins to descend, and the ball leaves the valve seat and starts to rotate.

2. The stem interacts with the guide pin in the stem spiral groove, causing the stem and ball to rotate 90° simultaneously.

3. The ball rotates 90° without contact with the valve seat, and finally, the angular plane at the bottom of the stem mechanically wedges and presses the ball against the valve seat to achieve complete sealing.

3. Application Scenarios of Multi-directional Control

Diversion and Confluence:T-type three-way ball valvesare widely used in scenarios requiring fluid distribution to multiple pipelines or confluence from multiple pipelines, such as material distribution and recovery in chemical production.

Flow Direction Switching:L-type three-way ball valvesare suitable for scenarios where fluid flow direction needs to be switched between two pipelines, such as flow direction switching in oil pipelines.

II. Sealing Technology of Three-way Ball Valve

Sealing performance is one of the key characteristics of three-way ball valves, directly affecting their reliability and safety in industrial applications. The development and innovation of sealing technology provide strong support for the application of three-way ball valves in extreme working conditions.

1. Selection of Sealing Materials

Polytetrafluoroethylene (PTFE): It has excellent corrosion resistance and low friction coefficient, suitable for various chemical media and low-temperature environments.

Flexible Graphite: Suitable for high-temperature environments, with good heat resistance and sealing performance.

Metal Sealing: Such as Stellite cobalt-based hard alloy, suitable for high-temperature, high-pressure, and high-wear environments.

2. Design of Sealing Structure

Rigid Sealing Seat: Simple in structure but poor in elasticity, suitable for low-pressure environments.

Sealing Seat with Elastic Elements: Pre-tightening force is provided through elastic elements (such as springs) to enhance sealing performance.

Lip-type Sealing Seat: It has good elasticity and can compensate for the pre-compression amount of the sealing surface, suitable for medium-pressure environments.

Combined Sealing Seat: It adopts a combination of an elastic expansion ring and a PTFE lip-type sealing seat, integrating the elastoplastic deformation capacity of metal materials and the corrosion resistance of PTFE, suitable for high-pressure and extreme temperature environments.

3. Optimization of Sealing Performance

Multi-seat Design:T-type three-way ball valvesadopt a four-seat design, with balanced force, ensuring reliable sealing on the closed channel.

Surface Treatment: Anti-corrosion coating treatment is applied to the valve body and internal components to improve corrosion resistance.

Dynamic Compensation: Through the combination of elastic elements and flexible materials, dynamic compensation of the sealing surface is achieved, ensuring good sealing performance during long-term use.

III. Applications of Three-way Ball Valves in Extreme Working Conditions

Due to their excellent multi-directional control capability and sealing performance,three-way ball valvesare widely used in various extreme working conditions. The following are typical application scenarios:

1. High-temperature and High-pressure Environments

In high-temperature and high-pressure oil and natural gas pipelines,three-way ball valvescan effectively cope with extreme temperatures and pressures by using high-temperature alloy materials and combined sealing seats. For example,T-type three-way ball valvescan be used for diversion and confluence operations to ensure stable fluid transmission under high-pressure conditions.

2. Cryogenic Environments

In cryogenic applications, such as the storage and transportation of liquefied natural gas (LNG), three-way ball valves use low-temperature special sealing materials (such as fluororubber) and low-temperature carbon steel or stainless steel materials to ensure sealing performance at low temperatures.

3. Corrosive Medium Environments

In chemical production,three-way ball valvesare often used to handle corrosive media. By selecting corrosion-resistant materials (such as stainless steel and PTFE) and optimizing the sealing structure, three-way ball valvescan operate stably for a long time in acidic, alkaline, or highly corrosive environments.