Knife gate valve

Product Overview

The Electric Knife Gate Valve is a knife‑edge gate valve driven by an electric actuator, designed only for ON‑OFF (open/close) service – not for flow regulation. It is widely used in automated piping systems in papermaking, wastewater treatment, mining, chemical, and power generation industries for remote shut‑off of media. The sharp knife‑edge gate cuts through hanging fibers, paper, plastic strips, and other materials during closure, preventing clogging.

The body flow path has no recesses, providing self‑cleaning action. A bidirectional sealing option is available for applications requiring pressure containment from either direction. The valve has flanged connections, with nominal diameters from DN50 to DN1200, pressure ratings PN10/PN16 (Class 150), and body materials including cast iron, carbon steel, and stainless steel. The electric actuator is equipped with a handwheel, limit switches, and optional explosion‑proof features.

Product Structure

The Electric Knife Gate Valve mainly consists of the electric actuator (ON‑OFF type) and the knife gate valve body assembly.

Electric Actuator (ON‑OFF Type):

1. Motor: Reversible motor providing driving force.

2. Gearbox: Gear or worm‑gear reducer delivering high torque.

3. Travel Limit Switches: Adjustable switches to control fully open and fully closed positions.

4. Torque Limit Switch: Overload protection to prevent valve damage if the gate jams.

5. Handwheel Mechanism: Manual override for on‑site commissioning and emergency operation.

6. Terminal Box: For connection of power, ON‑OFF control signal, and feedback signal.

7. Optional Accessories: Explosion‑proof actuator, dry contact limit switches, bus communication (Modbus, Profibus), etc.

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Knife Gate Valve Body Assembly:

1. Body: Cast or fabricated body in gray cast iron, ductile iron, carbon steel (WCB), stainless steel (CF8/CF8M), etc. Flanged ends conforming to GB/T 9113, ANSI B16.5, EN 1092‑1, etc. Full‑bore flow path with no pockets to prevent material buildup.

2. Gate: Stainless steel (304, 316, 310S) knife‑edge gate with a sharp edge to cut through fibers and particles. The gate surface can be hardfaced with Stellite or chrome‑plated for improved wear resistance.

3. Seats: Available in unidirectional or bidirectional sealing. Seat materials include rubber (EPDM, NBR, FKM), PTFE, metal (Stellite hardfaced), or ceramic.

4. Stem: Stainless steel trapezoidal‑thread stem, connected to the gate at the bottom and to the electric actuator output shaft at the top.

5. Packing Box: Contains PTFE or flexible graphite packing, compressed by a packing gland to prevent external leakage.

6. Yoke: Connects the body to the electric actuator.

Compact construction; electric control enables remote ON‑OFF operation.

Function

1. Remote Electric ON‑OFF Control: Receives an ON‑OFF signal (AC 220V, DC 24V, etc.) from DCS or PLC to automatically open or close the valve, allowing unattended operation.

2. Knife‑Edge Cutting Function: The sharp edge of the gate cuts through hanging fibers, paper, plastic strips, rags, and other materials during closure, preventing clogging.

3. Self‑Cleaning Flow Path: The body flow path has no recesses. When fully open, the media can flush the interior, preventing solids accumulation.

4. Bidirectional Sealing (optional): A bidirectional floating seat or double‑sided sealing design allows the valve to withstand media pressure from either direction, accommodating flow reversal or bidirectional pressure requirements.

5. Full‑Bore Low Flow Resistance: When fully open, the gate is completely out of the flow path, providing minimal pressure loss.

6. Overload Protection: The electric actuator is equipped with a torque limit switch that cuts motor power if the gate jams, protecting both valve and actuator.

7. Manual Emergency Operation: The handwheel on the actuator allows manual operation during power failure or actuator fault.

8. Valve Position Feedback: Provides dry contact limit switch signals (fully open / fully closed) for monitoring by a host system.

Working Conditions

1. Applicable Media: Pulp, sewage, sludge, mineral slurry, coal slurry, powders, fiber suspensions, particle‑laden liquids, corrosive liquids, etc.

2. Temperature Range: –20°C to +200°C (PTFE seats); –20°C to +80°C (rubber seats); –29°C to +550°C (metal seats).

3. Pressure Rating: PN10, PN16 (Class 150); higher ratings available on request.

4. Nominal Diameter: DN50 – DN1200 (2″ – 48″); larger sizes available on request.

5. Power Supply: AC 220V, AC 380V (standard); DC 24V optional.

6. Control Signal: ON‑OFF (AC 220V or DC 24V).

7. Feedback Signal: Limit switch contact signals (open / closed).

8. Typical Applications:

   1. Automatic shut‑off of pulp lines in paper mills

   2. Automatic sludge and sewage discharge in wastewater treatment plants

   3. Automatic control of mine tailings transport

   4. Ash and slag discharge in coal‑fired power plants

   5. Automatic batching of chemical fiber and polymer slurries

   6. Fruit pulp and sauce filling lines in the food industry

   7. Automatic dust discharge in steel mills

Summary

The Electric Knife Gate Valve (ON‑OFF type), with its advantages of remote electric ON‑OFF control, knife‑edge cutting function, self‑cleaning flow path, and optional bidirectional sealing, is an ideal shut‑off valve for automated piping systems handling media containing solid particles, fibers, or slurries. This valve is designed for fully open or fully closed operation only – not for flow regulation.

Compared with manual knife gate valves, the electric version enables remote control and centralized management, reducing manual intervention. Compared with ordinary electric gate valves, the knife‑edge gate effectively cuts through fibers and particles, preventing clogging. With flanged connections, a full‑bore flow path, and optional explosion‑proof actuators, it is suitable for harsh environments and hazardous areas. For pipeline systems that require automatic ON‑OFF control and handle media containing solids, fibers, or slurries, the Electric Knife Gate Valve is an efficient and reliable solution.