The plug valve is a commonly used fluid control valve, widely applied in industries such as oil, natural gas, and chemicals due to its high sealing performance and ease of operation. The valve features a simple design, where a rotating plug controls the flow direction of the fluid, ensuring safe operation in systems involving high pressure, high temperature, and hazardous media.

1. Working Principle

The core structure of a plug valve is a cylindrical or conical plug with a through passage. When the plug rotates, the passage aligns or misaligns with the fluid pathway of the valve body, thus controlling the opening and closing of the valve.

(1) Open Position

When the passage on the plug valve aligns with the fluid pathway of the valve body, the fluid can flow directly through the valve, ensuring an unobstructed flow. This design minimizes pressure loss during fluid flow, making it suitable for applications where maintaining stable flow is essential.

(2) Closed Position

When the plug is rotated 90 degrees, the passage becomes perpendicular to the fluid pathway, completely cutting off the flow of fluid, achieving the closed position. The 90-degree rotation of the plug valve allows for a complete shutdown of the fluid flow, offering a quick response, making it ideal for emergency shut-off applications.

2. Structural Characteristics

(1) Types of Plug Valves

Plug valves typically come in two types: conical and cylindrical plugs. The conical plug provides better sealing performance but may require additional lubrication or material support at high temperatures, while the cylindrical plug operates smoothly and is suitable for applications requiring frequent on/off operation.

(2) Sealing Materials

The sealing design of plug valves typically uses PTFE (Polytetrafluoroethylene) or other non-metallic lining materials, which offer high corrosion resistance and flexibility, ensuring good sealing performance even under high pressure. Additionally, some high-end plug valves employ metal-to-metal sealing for extreme environments, preventing seal failure.

(3) Wear and Corrosion Resistance

The internal materials of plug valves are typically made of corrosion-resistant materials such as stainless steel or nickel-based alloys, preventing wear caused by medium corrosion. This makes them suitable for transporting acidic or corrosive media and is commonly used in the chemical industry and refining systems.

(4) Simple Maintenance

The internal structure of the plug valve is simple, with no complex springs or valve disc mechanisms, making disassembly and maintenance relatively easy. In high-temperature and high-pressure environments, specific materials and designs can be selected to extend the valve’s service life and reduce subsequent maintenance costs.

3. Application Scenarios

The application of plug valves is commonly found in critical situations where leakage prevention is essential, as well as in systems requiring rapid opening and closing or fluid shut-off. Below are some typical application scenarios:

(1) Oil and Gas Industry

In oil and gas transportation pipelines, plug valves reduce the potential risk of leakage with their reliable sealing performance. Especially at the ends or junctions of long-distance pipelines, plug valves can quickly shut off the flow, ensuring safe operation.

(2) Chemical Industry

In highly corrosive or particle-laden media, plug valves perform exceptionally well. Their corrosion-resistant design is ideal for transporting acidic or alkaline liquids, chemical solvents, and other media, effectively handling complex chemical environments and reducing the risk of material corrosion.

(3) High-Temperature and High-Pressure Systems

Some specially designed metal-to-metal sealing plug valves can operate stably for extended periods in high-temperature and high-pressure systems. They are commonly used in steam pipelines, boiler systems, and other high-temperature environments, maintaining excellent sealing and flow control.

(4) Emergency Shut-off Systems

In systems where rapid fluid flow interruption is necessary, the 90-degree rotation design of the plug valve allows for quick and complete fluid shut-off in emergency situations, ensuring safety.

4. Key Points for Installation and Maintenance

(1) Installation

During installation, ensure that the valve is properly aligned with the pipeline to avoid valve body damage due to pipeline stress. In operational systems, it is recommended to perform manual torque testing to ensure the flexibility of the plug.

(2) Lubrication and Seal Inspection

For plug valves used in high-temperature environments, regular lubrication is necessary to prevent the plug from sticking. Inspect the wear on the sealing materials to ensure that the valve maintains its sealing performance in high-pressure environments.

(3) Periodic Maintenance

For systems in long-term use, it is recommended to regularly check for wear on the plug and aging of the sealing rings. Replace them as necessary to ensure the valve's safety performance.