- Differences in structure and working principle
| Terms | butterfly valve | knife gate valve |
|---|---|---|
|
Core Structure |
The round butterfly plate rotates around the valve shaft (angle ≤ 90°), the valve body is mostly round or oval structure. | Knife-shaped wedge gate moves vertically up and down, the valve body is a rectangular structure, with cutting edge design to cope with particulate media. |
| Opening and closing method | Angular stroke drive, by rotating the butterfly plate to regulate the flow or cut off the medium | Straight stroke valve, the gate and sealing surface to form a shear action, only support full open or full closed |
| Sealing Mechanism | The outer edge of the butterfly plate contacts the elastic sealing ring to achieve sealing, and the sealing performance is greatly affected by the medium pressure. | The knife plate and the valve seat form a shear seal through the rigid sealing surface, which can cut media impurities to enhance the reliability of the seal. |
- Comparison of performance parameters
| parametric | butterfly valve | knife gate valve |
|---|---|---|
| Applicable pressure | ≤PN40(Medium and low voltage scenarios) | Up to PN100 (high pressure scenarios) |
| Applicable temperature | -20°C to 200°C (subject to sealing materials) | -29°C to 425°C (metal hard seal suitable for high temperatures) |
| Fluid resistance | Low resistance to flow when fully open (approx. 0.5), but prone to turbulence for high-speed fluids | The flow path is completely through, the resistance coefficient is close to 0, suitable for high flow requirements |
| Opening and closing speed | Fast (opening and closing in 90° rotation), supports frequent operations | Longer opening and closing strokes, slower action (requires full lifting and lowering of the knife plate) |
- The difference between application scenarios
| Applications | Butterfly valve | Knife gate valve |
|---|---|---|
| Suitable media | Clean liquids, gases and media with trace suspended solids (e.g. water supply and drainage, air-conditioning circulating water) | High-viscosity fluids, slurries containing fibres/particles (e.g. papermaking slurries, sewage sludge, petroleum coke sludge) |
| Typical areas | Building water supply, fire-fighting systems, food processing ventilation ducts | Chemical reactor outlet, mine tailings transport, thermal power ash treatment |
| Operational requirements | Scenarios requiring flow regulation or frequent opening and closing (e.g. pumping station pressure regulation) | Harsh conditions requiring only full opening/closing with impurities (e.g. sewage treatment plant interception) |
- Maintenance and economy differences
| Dimensionality | Butterfly valve | Knife gate valve |
|---|---|---|
| Maintenance costs | Simple structure, easy to replace seals (rubber material life of about 3-5 years) | The knife plate needs to be replaced as a whole after wear and tear, and the maintenance frequency is high (the life expectancy is about 1-3 years in the scenario with solid media). |
| Manufacturing cost | Light weight (30%-50% lighter than knife gate valve under the same calibre), flexible material selection (fluorine lining anti-corrosion can be selected) | Heavy casting valve body and high hardness cutter plate processing cost is higher |