Knife gate valve

Product Overview

The Manual Knife Gate Valve is a shut‑off valve with a handwheel‑direct‑driven mechanism and a knife‑edge gate. It is designed only for ON‑OFF (open/close) service – not for flow regulation. Compared with electric or pneumatic knife gate valves, the manual version requires no external power source, offers simple construction, reliable operation, and low cost. It is particularly suitable for locations without electricity or compressed air, as well as for infrequent operation.

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. The valve has flanged connections, with nominal diameters from DN50 to DN600, pressure ratings PN10/PN16 (Class 150), and body materials including cast iron, carbon steel, and stainless steel. It is widely used for pipeline shut‑off in wastewater treatment, papermaking, mining, chemical, and similar industries.

Product Structure

The Manual Knife Gate Valve mainly consists of the handwheel drive mechanism and the valve body assembly.

Handwheel Drive Mechanism:

1. Handwheel: Cast iron or ductile iron handwheel with a non‑slip handle.

2. Stem Nut: Copper alloy or stainless steel nut engaging with the stem trapezoidal threads.

3. Bearings: Thrust ball bearings or plain bearings to reduce operating torque.

4. Yoke: Connects the body to the drive mechanism and absorbs axial forces.

5. Stem: Stainless steel trapezoidal‑thread stem, moving the gate up and down.

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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 recesses.

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.

3. Seats: Available in rubber (EPDM, NBR, FKM), PTFE, or metal sealing; bidirectional sealing optional.

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

5. Optional Bonnet: Available with an enclosed bonnet (for hazardous media) or open‑frame (bonnetless) construction.

Compact construction; manual operation requires no electricity or compressed air.

Function

1. Manual Operation: Rotating the handwheel turns the stem nut, driving the stem and gate up or down to open or close the valve. No external energy required.

2. Knife‑Edge Cutting Function: The sharp edge of the gate cuts through hanging fibers, paper, plastic strips, 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.

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

6. Low Operating Torque: The trapezoidal threads combined with bearings make handwheel operation easy.

7. Visual Position Indication: A position indicator on top of the stem allows visual confirmation of valve open/close status.

8. Easy Maintenance: Packing can be adjusted or replaced in‑line without removing the valve body.

Working Conditions

1. Applicable Media: Sewage, sludge, pulp, slurry, mud, fiber suspensions, particle‑laden 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 – DN600 (2″ – 24″); larger sizes available on request.

5. Operation: Manual (handwheel); bevel gear option available for large sizes to reduce operating effort.

6. Typical Applications:

   1. Sludge and sewage lines in wastewater treatment plants (no power supply areas)

   2. Manual isolation in paper mill pulp lines

   3. Manual shut‑off in mine tailings pipelines

   4. Standby valves in chemical slurry lines

   5. Manual control in fruit pulp and sauce lines in the food industry

   6. Manual valves in industrial wastewater treatment systems

   7. Agricultural irrigation mud pipelines

Summary

The Manual Knife Gate Valve, with its advantages of manual operation, no external energy required, knife‑edge cutting function, self‑cleaning flow path, and simple construction, is an ideal shut‑off valve for handling particle‑ or fiber‑laden media in locations without electricity or compressed air, and for infrequent operation. Compared with electric or pneumatic knife gate valves, the manual version offers lower initial cost, simpler maintenance, and higher reliability.

With flanged connections, a full‑bore flow path, and handwheel or bevel gear operation, the Manual Knife Gate Valve is an economical and practical first choice for pipeline systems that require reliable shut‑off, handle solids or fibers, and have no on‑site power source or require only occasional operation.