Differences in Structural Design and Operating Principles
1. Wedge-Type Gate
- The gate is wedge-shaped (single or double wedges). The vertical movement of the valve stem compresses the gate against the inclined surface of the valve seat, achieving a seal.
- Typical structures include elastic gates (accommodating temperature deformation) and rigid gates (suitable for high pressures).
- The seal is assisted by the medium pressure, tightening with increasing pressure, making it suitable for high-pressure conditions (e.g., PN16-PN100).
2. Parallel Gate
- The gate is a double-plate structure with a spring or support device in the middle, forcing the two plates into contact with the valve seat through external force.
- Available in single-plate (sealing by medium pressure) and double-plate (sealing by spring preload). The latter is more suitable for low-pressure or clean media (e.g., below PN10).
Performance Comparison and Application Scenarios
1. Sealing
- Wedge-type gates offer more reliable sealing at high pressures, but are prone to leakage at low temperatures due to material shrinkage. Parallel gates are more adaptable to low-pressure and particulate media.
- According to the GB/T 12234-2019 standard, the leakage level of wedge gate valves can reach ANSI Class VI (bubble level), while that of parallel gate valves is generally Class IV (drip leakage is permitted).
2. Fluid Resistance
- Both types offer low resistance when fully open (flow resistance coefficient approximately 0.1-0.3), but the parallel gate valve, due to its simpler structure, is more suitable for high-velocity media (such as pipelines larger than DN300).
3. Maintenance Cost
- Wedge gate valve maintenance requires grinding the sealing surface, which takes a long time. Parallel gate valves allow for quick replacement of gate components, reducing maintenance costs by 30%-50% (data source: American Valve Association analysis report).
Selection Recommendations
1. Applications Where Wedge Gate Valve ... 2. Parallel gates are preferred for applications involving solid particles or viscous media (e.g., sewage treatment);
- Low-pressure, large-diameter pipelines (e.g., municipal water supply and drainage systems DN ≥ 500).
Additional Knowledge: Special Variant Designs
1. The "elastic gate" of the wedge gate compensates for temperature deformation and is suitable for temperatures ranging from -196°C to 550°C.
2. The "knife gate" of the parallel gate is specifically designed for slurry media, increasing cutting capacity by 40%.