Knife Gate Valve

Knife gate valves are used in mining, wastewater treatment, pulp and paper, and chemical processing to isolate or control the flow of abrasive or viscous fluids. They are specified by nominal diameter, pressure rating, body material, and seat type. Grades differ by body construction (wafer, lug, or flanged), gate material (stainless steel or duplex), and seat options (metal-to-metal, resilient, or replaceable). They are chosen for their ability to handle high solids content and provide a bubble-tight seal even after repeated cycling. The valve uses a flat, sharp-edged gate that slides perpendicular to the flow path. When closed, the gate cuts through the media and presses against a seat to form a seal. The knife edge reduces cutting force and ensures a clean shut-off, even with fibrous or particulate-laden fluids. Common parameters include nominal diameters from DN50 to DN600 (ISO 6708), pressure ratings PN10 to PN16 (ISO 7005), body materials such as CF8M (316 stainless steel) or WCB (carbon steel) per ASTM A351/A216, gate materials like SS316 or Duplex 2205 per ASTM A240, and seat materials including EPDM, PTFE, or metal. Face-to-face dimensions comply with ISO 5752 or MSS SP-81, and flange drilling matches ANSI 150 or PN10/16 per ASME B16.5 or ISO 7005. Leakage rate for resilient seats is Class VI (bubble-tight) per ANSI FCI 70-2. Operating temperature ranges from -20 to +120 °C, and maximum working pressure is 10–16 bar at ambient temperature. Internal surface finish is ≤ 6.3 μm Ra. Test pressures are 1.5 × PN for shell and 1.1 × PN for seat per ISO 5208. Actuator mounting complies with ISO 5211. Relevant standards include ISO 5211, ANSI B16.34, API 609, MSS SP-81, and GB/T 12234. Always verify model-specific values and standards with the legal manufacturer or supplier.

The valve uses a flat, sharp-edged gate that slides perpendicular to the flow path. When closed, the gate cuts through the media and presses against a seat to form a seal. The knife edge reduces cutting force and ensures a clean shut-off, even with fibrous or particulate-laden fluids. The gate is guided by body grooves and is typically operated by a handwheel, pneumatic actuator, or electric actuator. The seat can be resilient (e.g., EPDM, PTFE) or metal-to-metal, depending on the application. The design allows for a bubble-tight seal in resilient-seat versions, while metal seats are used for higher temperatures or abrasive media. The valve is installed between flanges (wafer type) or with integral flanges (lug or flanged type). The sharp edge minimizes wear and prevents clogging, making it suitable for slurries and powders.