Knife gate valve

Product Overview

The Bevel Gear Knife Gate Valve is a knife‑edge gate valve driven by a bevel gear reduction mechanism. It is designed only for ON‑OFF (open/close) service – not for flow regulation. Compared with standard handwheel‑operated knife gate valves, the bevel gear drive provides a gear reduction ratio (typically 4:1 or 5:1) that significantly reduces the required operating torque, making valve operation much easier – especially for large diameters (DN300 and above) or applications where high torque is needed.

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 DN300 to DN800, pressure ratings PN10/PN16 (Class 150), and body materials including cast iron, carbon steel, and stainless steel. It is widely used for large‑bore shut‑off in sewage, pulp, slurry, power generation, and other industries.

Product Structure

The Bevel Gear Knife Gate Valve mainly consists of the bevel gear drive mechanism and the valve body assembly.

Bevel Gear Drive Mechanism:

1. Handwheel: Cast iron or ductile iron handwheel with a large diameter for easy operation.

2. Bevel Gearbox: A pair of spiral bevel gears with built‑in bearings, providing high transmission efficiency and low noise. Reduction ratio is typically 4:1 to 5:1.

3. Input Shaft: Connected to the handwheel, rotating the smaller bevel gear.

4. Output Shaft: Connected to the stem nut or directly to the stem, delivering amplified torque.

5. Housing: Cast iron or cast steel sealed housing with protection rating IP54 or higher, suitable for outdoor environments.

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

7. Bearings: Thrust bearings to absorb axial loads.

8. Yoke: Connects the gearbox to the valve body.

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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. Stem: Stainless steel trapezoidal‑thread stem, moving the gate up and down. For large diameters, the stem diameter is increased to handle higher torque.

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

6. Bonnet: Bolted to the body, with internal guides to ensure vertical gate movement.

7. Optional Flush Ports: For settling media, flush ports can be provided.

The bevel gear drive makes large‑diameter valve operation easy, allowing a single person to open or close the valve effortlessly.

Function

1. Bevel Gear Reduction Drive: The gear reduction ratio multiplies the input torque from the handwheel, making operation easy – particularly suitable for large diameters or high‑torque valves.

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. Mechanical Self‑Locking: The bevel gear reduction mechanism is self‑locking; the gate will not move due to media pressure, ensuring safety.

7. Good Environmental Protection: The sealed gearbox housing protects against dust, moisture, and outdoor conditions.

8. Valve Position Indication: A position indicator on the output shaft or the number of handwheel turns can indicate the valve open/close status.

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: DN300 – DN800 (12″ – 32″); larger sizes available on request.

5. Operation: Bevel gear manual with large handwheel. (Electric or pneumatic actuators can also be fitted in place of the bevel gear.)

6. Typical Applications:

   1. Large‑diameter sludge lines in wastewater treatment plants

   2. Pulp lines of DN300 and above in paper mills

   3. Main tailings transport pipelines in mining

   4. Main ash and slag lines in power plants

   5. Large‑diameter isolation valves in industrial recirculating water systems

   6. Raw water pipelines in municipal water supply

Summary

The Bevel Gear Knife Gate Valve, with its advantages of bevel gear reduction drive, low operating torque, knife‑edge cutting function, and self‑cleaning flow path, is an ideal shut‑off valve for large‑diameter (DN300 and above) pipelines handling particle‑ or fiber‑laden media. Compared with standard handwheel‑operated knife gate valves, the bevel gear drive significantly reduces operating torque through gear reduction, allowing one person to easily operate large‑diameter valves.

Compared with electric or pneumatic knife gate valves, the bevel gear manual valve requires no external power, has lower initial cost, and is simpler to maintain. With flanged connections, a full‑bore flow path, and reliable sealing, the Bevel Gear Knife Gate Valve is an economical, easy‑to‑operate, and practical solution for ON‑OFF pipeline systems that require reliable shut‑off, handle solids or fibers, have large diameters, and have no on‑site power source.