Parallel gate valves rely on a spring or wedge between the two gates to achieve a forced seal. They are easy to operate, have low flow resistance, and are suitable for low-pressure, large-diameter pipelines. Wedge gate valves, on the other hand, utilize the self-tightening principle of a wedge-shaped gate to enhance sealing performance. They are resistant to high pressure and high temperature, but require high installation precision and are widely used in harsh environments such as petrochemicals and power plants.
Parallel gate valves: The two sealing surfaces are parallel to each other. They typically employ a double-gate structure with a spring or thrust wedge in the middle. External force is used to press the gate tightly against the valve seat to achieve a seal.
Wedge gate valves: The sealing surfaces are wedge-shaped (commonly 2°52′ to 10°). When closed, the gate wedges downwards, utilizing the self-tightening effect of the inclined plane to increase the sealing pressure, achieving a tightening effect with increasing pressure.
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Comparison Table: Parallel Gate Valve vs. Wedge Gate Valve
| Comparison Dimension | Wedge Gate Valve | Parallel Gate Valve |
| Gate Structure | The gate is wedge-shaped (V-type); the two seating faces are at an angle. | The two seating faces are parallel to each other; the gate is a flat plate. |
| Sealing Principle | Forced Sealing: Relies on the mechanical downward force of the stem to wedge the gate into the seats. | Pressure-Assisted Sealing: Primarily relies on the media pressure to push the gate against the downstream seat. |
| Thermal Binding | High Risk: Changes in temperature cause seat expansion, which can "lock" the wedge gate in place. | Minimal Risk: The parallel structure is not affected by radial compression caused by temperature changes. |
| Operating Torque | Higher: Requires significant torque at the moment of closure to overcome friction and wedging force. | Lower: Only needs to overcome sliding friction throughout the stroke. |
| Sealing Performance | Excellent: Mechanical alignment ensures a robust seal at both low and high pressures. | Superior at High Pressure: At low pressure, it may require internal springs for a tight seal. |
| Wear & Tear | High friction at the point of contact; seating faces are prone to galling over time. | Uniform sliding friction throughout the stroke; wear is more evenly distributed. |
| Flow Resistance | Minimal: Straight-through flow path when fully open (full bore). | Minimal: Straight-through flow path; essentially acts like a section of pipe. |
| Maintenance | Moderate: Angled seats require high precision for grinding and alignment. | Lower: Parallel faces are easier to grind and resurface during maintenance. |
| Typical Applications | Water, Steam, Oil, Gas (General industrial/municipal use). | Oil & Gas Transmission, Chemical plants, Power stations (especially high-temp service). |
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FAQ
What is the application of wedge gate valve?
Wedge Gate Valves are commonly used as on-off and isolation valves in oil, gas, water, sea water and steam lines. They are used fully open or fully close and not suitable for throttling. Vastas Wedge Gate Valves are API 600 licensed and SIL 2&3 certified.
What is the lifespan of a gate valve?
15–25 years
Approximate lifespan by valve type: Gate Valves:15–25 years. Ball Valves:10–20 years. Butterfly Valves:8–15 years.