The pressure-balanced plug valve is a special plug valve designed to reduce the operating torque under high-pressure conditions and enhance the sealing reliability. Its core principle is to offset the axial thrust of the medium pressure on the plug through the internal pressure balance channel, thereby significantly reducing the opening and closing resistance and extending the sealing life. The following are its key features and technical analysis:
1. Core working principle
Pressure balance mechanism
A through channel (such as a top opening) is designed inside the plug to allow the high-pressure medium to act on both ends of the plug inlet and outlet at the same time, forming an axial force balance, eliminating the huge friction resistance caused by the unilateral pressure extrusion of the traditional plug valve.
During operation, only the friction between the sealing pairs needs to be overcome, and the torque can be reduced by more than 60%, which is especially suitable for large-diameter high-pressure valves.
Oil-lubricated sealing system
Special sealing grease is injected through the valve stem or valve body grease injection channel to form a dynamic oil film sealing layer between the plug and the valve seat, enhancing the sealing and reducing metal contact wear.
The grease injection function can replenish sealing grease during the use of the valve, repair minor leaks, and extend the maintenance cycle.
2. Structural characteristics
| Features | Advantages |
|---|---|
| Flip-chip design | The valve stem is installed from the bottom of the valve body (inverted structure), and the packing can be replaced online during maintenance to avoid disassembly of the pipeline |
| Metal Hard Seal | The plug body and valve seat are made of hardened alloy (such as Stellite coating), which is resistant to erosion and high temperature (≤540℃) |
| Fire safety | Complying with API 6FA standard, the metal seal pair can still maintain emergency sealing in case of fire. |
| Low flow resistance design | Full-diameter flow channel + semi-circular optimized channel, minimal pressure drop loss, suitable for high flow conditions |
3. Typical application scenarios
High-pressure oil and gas transportation: Class 900Lbs and above pressure level (such as wellhead equipment, long-distance pipelines), withstanding pressure ≥ 15MPa.
Refining high-temperature medium: Diversion and cutting of viscous media such as heavy oil and asphalt, sealing surface temperature resistance > 350℃.
Fluid containing solid particles: The oil lubrication system can prevent particles from embedding into the sealing surface, suitable for sand-containing crude oil or slurry.
4. Selection specifications and standards
Manufacturing standards: Must comply with API 599 (valve inspection), API 6D (pipeline valves) or API 6A (wellhead equipment).
Pressure level: Conventionally covers ANSI 150~2500Lbs, and special working conditions support API 6A 5000psi high-pressure customization.
Material requirements: High sulfur environment must meet NACE MR0175 sulfur corrosion resistance standard.