Knife gate valve

Product Overview

The Non‑rising Stem Knife Gate Valve is a knife‑edge gate valve in which the stem rotates without rising while the gate moves vertically. It is designed only for ON‑OFF (open/close) service – not for flow regulation. Compared with rising stem knife gate valves, the non‑rising design maintains a constant overall height, requiring less vertical installation space. It is especially suitable for confined spaces such as valve pits, basements, and pipe trenches.

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. Actuators can be manual, electric, or pneumatic (all ON‑OFF type)

Product Structure

The Non‑rising Stem Knife Gate Valve mainly consists of the actuator  and the non‑rising stem valve body assembly.

Actuator:

1. Available in manual (handwheel), electric, or pneumatic.

2. Manual: the handwheel directly rotates the stem nut; the stem rotates without rising, and the gate is driven up/down via the thread pair.

3. Electric/pneumatic: the actuator outputs rotational torque to drive the stem.

4. All actuators are ON‑OFF type – not for modulation.

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Non‑rising Stem 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. The top of the gate is connected to the stem; as the stem rotates, the gate moves up/down along guide grooves.

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

4. Stem: Stainless steel trapezoidal‑thread stem. The lower end connects to the gate, and the upper end connects to the actuator (or handwheel). The stem rotates only – it does not rise.

5. Stem Nut: Copper alloy or stainless steel nut fixed to the body or yoke, engaging with the stem threads to convert rotary motion into linear gate movement.

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

7. Guide Grooves: Internal guide ribs in the body or bonnet ensure vertical gate movement without tilting.

8. Yoke: Connects the body to the actuator (the yoke is shorter due to the non‑rising stem design).

The non‑rising design keeps the overall valve height constant, making it suitable for space‑limited installations.

Function

1. Non‑rising Stem Construction: The stem rotates without rising; the overall valve height does not change, requiring minimal vertical space – ideal for valve pits, basements, and other confined areas.

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. Remote ON‑OFF Control: With electric or pneumatic actuators, remote automatic open/close operation is possible.

7. Manual Emergency Operation: Manual version operates directly by handwheel; electric/pneumatic versions are equipped with a handwheel for manual operation during power or air supply failure.

8. Valve Position Indication: The top of the stem typically has a position indicator, or external limit switches provide valve position feedback.

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. Installation Space: Applications with limited vertical clearance (valve pits, basements, pipe trenches, etc.).

6. Typical Applications:

   1. Sludge valves in valve pits of underground wastewater treatment plants

   2. Sewage line shut‑off in building basements

   3. Pulp line isolation in space‑limited areas of paper mills

   4. Underground mine slurry pipelines

   5. Isolation valves in industrial pipe trenches

   6. Blow‑off valves in municipal water supply valve pits

Summary

The Non‑rising Stem Knife Gate Valve, with its advantages of non‑rising stem design for space saving, knife‑edge cutting function, self‑cleaning flow path, and optional bidirectional sealing, is an ideal shut‑off valve for pipelines handling particle‑ or fiber‑laden media in installations with limited vertical clearance. Compared with rising stem knife gate valves, the non‑rising version maintains a constant overall height, making it especially suitable for valve pits, basements, and pipe trenches. Compared with ordinary non‑rising gate valves, the knife‑edge gate effectively cuts through fibers and particles, preventing clogging. With flanged connections, a full‑bore flow path, and optional manual or automated actuators, the Non‑rising Stem Knife Gate Valve is an efficient and compact solution for ON‑OFF pipeline systems that require reliable shut‑off, handle solids or fibers, and have limited installation height.