1. Flow control and structural limitations
Unable to adjust flow: Only fully open or fully closed states are supported, and fine flow adjustment cannot be achieved;
Flow resistance problem: In some designs, when the knife gate valve is fully opened, the blade is perpendicular to the fluid direction, which may cause large flow resistance and energy loss;
Simple structure leads to functional limitations: It cannot adapt to special scenarios such as silencer, and the compensation is poor.
2. Sealing performance and leakage risk
The sealing surface is easy to wear: The contact surface between the blade and the valve seat is large, and it is easy to leak due to wear after long-term use;
Insufficient material adaptability: If the material is not properly selected (such as non-corrosive materials), the sealing surface is easily eroded by the medium and fails;
Impurity sensitivity: Welding slag, particles and other impurities are easy to embed into the sealing surface, reducing the reliability of the seal.
3. Operation and maintenance issues
Effortless switching operation: Large-diameter valves require greater operating force, and manual operation is inefficient;
Slow switching speed: Long opening and closing time may affect the system response efficiency;
Frequent maintenance: The worn gate plate (wear exceeds 2mm and needs to be replaced) and seals need to be replaced regularly.
4. Durability and working condition restrictions
The blade is easy to damage: the blade is easy to wear, deform or jam, reducing the service life;
Not suitable for high temperature and high pressure: the sealing surface is easy to fail under high temperature and high pressure, limiting the scope of application;
Noise and impact: it is easy to generate large noise and fluid impact during the opening and closing process, which may damage the pipeline.
5. Other defects
Large size: it occupies more installation space, especially the large-diameter open rod design;
Water hammer risk: water hammer phenomenon may be caused when closing quickly.
The disadvantages of knife gate valves are mainly concentrated in sealing performance, operating efficiency and working condition adaptability. When selecting, it is necessary to weigh the pros and cons in combination with the characteristics of the medium and the use scenario.